Review Article | Open Access
Dan G. Duda, "Molecular Biomarkers of Response to Antiangiogenic Therapy for Cancer", International Scholarly Research Notices, vol. 2012, Article ID 587259, 11 pages, 2012. https://doi.org/10.5402/2012/587259
Molecular Biomarkers of Response to Antiangiogenic Therapy for Cancer
Antiangiogenic therapy for cancer has gone from an intriguing hypothesis in the 1970s to an accepted treatment approach for many cancer types. It has also become a standard of care for certain eye diseases. Yet, despite the use of molecularly targeted drugs with well defined targets, to date there are no biomarkers to guide the use of antiangiogenic therapy in patients. The mechanisms of action of these drugs are also being debated. This paper discusses some of the emerging biomarker candidates for this type of cancer therapy, which have provided mechanistic insight and might be useful in the future for optimizing cancer treatment.
1. Antiangiogenic Therapy
Approval of an anti-vascular endothelial growth factor (VEGF) blocking antibody (bevacizumab or Avastin, Genentech, South San Francisco, CA, USA) in combination with chemotherapy for metastatic colorectal cancer in 2004 represented a paradigm shift in cancer therapy. For the first time, an agent targeting the tumor stroma (i.e., the vasculature), as opposed to directly targeting the malignant cells proved to be a viable anticancer treatment option.
Over the last decade, the United States Food and Drug Administration has approved eight anti-angiogenic agents for cancer treatment, and three anti-angiogenic agents for wet age-related macula degeneration therapy (Table 1). A large number of other anti-angiogenic agents are in late phases of clinical development (phase III clinical trials). All the approved anti-angiogenic drugs target VEGF signaling. Some are blocking the ligand, VEGF, for example, bevacizumab, aflibercept (Zaltrap/Eylea, Sanofi-Aventis, Paris, France, and Regeneron Pharmaceuticals, Tarrytown, NY, USA), ranibizumab (Lucentis, Genentech, South San Francisco, CA, USA), and pegaptanib (Macugen, OSI Pharmaceuticals, Long Island, NY, USA). Others are inhibiting the activity of the VEGF tyrosine kinase receptors (VEGFR1, VEGFR2), for example, sorafenib and regorafenib (Nexavar and Stivarga, Bayer Healthcare Pharmaceuticals, Leverkusen, Germany, and Onyx Pharmaceuticals, South San Francisco, CA, USA), sunitinib (Sutent) and axitinib (Inlyta) (Pfizer Inc., New York, NY, USA), pazopanib (Votrient, GlaxoSmithKline, Brentford, Middlesex, UK), and vandetanib (Zactima, Astra Zeneca Pharmaceuticals, Alderley Park, Cheshire, UK). Anti-VEGF therapy has become a standard of care for metastatic colo-rectal cancer (in first, second, and third line of treatment), advanced non-small cell lung cancer, renal cell carcinoma, hepatocellular carcinomas, glioblastoma, gastrointestinal stromal tumor (GIST), pancreatic neuroendocrine tumor, and medullary thyroid cancer [1–13] (Table 1). Given these developments, anti-angiogenic therapy represents one of the most exciting areas in cancer research and clinical oncology [14–23]. But beyond the proof-of-the-principle efficacy for anti-angiogenic therapy in these advanced cancers, this success brought critical challenges. First, this therapy has not shown the same benefit in other advanced cancers (e.g., breast cancer, ovarian cancer, prostate cancer, and pancreatic ductal adenocarcinoma) . Second, in the patients who respond to anti-angiogenic therapy, the benefit is transient (i.e., the tumors acquire resistance to anti-angiogenic treatment). Other patients do not respond at all (i.e., the tumors are inherently resistant to anti-angiogenic treatment). Third, similar to most other anti-cancer drugs, anti-angiogenic agents may induce significant side effects . And finally, treatment with current anti-angiogenic agents is extremely costly [26, 27]. How do we tackle these problems? One potential solution for optimizing treatment with current anti-angiogenic agents is to identify useful biomarkers (see Box 1 for definitions) in order to (1) select (or exclude) patients for treatment with a specific anti-angiogenic drug; and (2) detect early the escape from anti-VEGF therapy.
The former would allow a “more personalized” treatment (for patients more likely to benefit) and/or a sparing of a fraction of patients (those unlikely to respond) from the side effects and the high cost of these treatments. The latter would allow us to devise better combinatorial treatment strategies to extend the benefit of anti-angiogenic agents. Biomarkers have been used for “molecularly targeted” agents, but so far only for those that directly attack the cancer cells, for example, human epidermal growth factor receptor 2 (HER2) expression or amplification for anti-HER2 therapy in breast cancer, RAS mutation for anti-epidermal growth factor receptor (EGFR) therapy, and mutation for BRAF inhibitors in melanoma [57–59]. But despite agreement that biomarker discovery and validation are a major priority in the tumor angiogenesis field and the widespread use of anti-angiogenic drugs in the clinic, there are currently no validated biomarkers for use in the clinic for treatment of patient with any type of cancer or for the treatment for wet age-related macula degeneration. Among the many reasons for this situation the most notable are (1) tumor heterogeneity, (2) the incomplete understanding of the mechanism(s) of action that lead to benefit of anti-VEGF therapy in some but not all advanced cancers, and (3) the differential targeting of VEGF pathway and off-target effects by the current anti-angiogenic drugs and by the agents in clinical development. I will summarize here the current progress on our mechanistic understanding of anti-VEGF therapy and on the current status molecular and cellular biomarker discovery and will provide a perspective on the future directions in this field.
2. The Angiogenic Balance
Over four decades of research on angiogenesis have unraveled many of the underpinnings of tumor angiogenesis in general and VEGF pathway in particular [60–64]. VEGF is a key proangiogenic molecule in developmental neovascularization as well as in physiological and pathological angiogenesis [62, 65–67]. VEGF exerts its effect by binding the two tyrosine kinase (TK) receptors VEGFR-1 (FLT1) and VEGFR-2 (KDR) as well as the non-TK receptors neuropilin 1 (NRP-1) and NRP-2 . Of these, VEGF interaction with VEGFR2 is thought to convey most of the critical pro-angiogenic signals . However, VEGF interaction with VEGFR-1 and NRP-1 in cancer cells or in nonendothelial stromal cells (e.g., in myeloid cells such as macrophages) may be critical for the growth of tumors that depend on this pathway for survival and, through indirect mechanisms, to angiogenesis in tumors . During development and in physiological conditions, the effects of VEGF are finely tuned and counterbalanced by anti-angiogenic molecules such as the soluble form of VEGFR-1 (sVEGFR-1/sFLT-1) or thrombospondins (TSP-1 and -2), which ensures stabilization and maturation of the vasculature . In tumors, oncogene or hypoxia-driven VEGF overexpression leads to dysregulated angiogenesis and an abnormal vasculature . Here, the balance is tipped toward pro-angiogenesis. In genetic models in mice, overexpression of VEGFR-1 and sVEGFR-1 led to a “normalization” of the tumor vasculature . Conversely, overexpression of sVEGFR1 may lead to hypertension (e.g., preeclampsia) or defects in developmental angiogenesis [70–72]. Beyond VEGF, other VEGF family members can bind the VEGFRs and participate in angiogenesis: PlGF, VEGF-B, VEGF-C, and VEGF-D. The role of VEGFR-1 and its more selective ligand placental growth factor (PlGF) is currently unclear, but may be particularly important in certain malignancies . Similarly, VEGF-C and VEGF-D might play a role during new blood vessel formation . First, they can bind to VEGFR2, and second, their cognate receptor VEGFR3 is expressed on “tip” cells (specialized endothelial cells responsible for vessel sprouting) [60, 73]. In addition, other angiogenesis modulators (positive or negative) may affect the angiogenic balance, for example, the pro-angiogenic molecules basic fibroblast growth factor (bFGF or FGF-2), angiopoietin 1 (Ang-1), Ang-2, and endoglin or the endogenous angiogenesis inhibitors TSP-1 and TSP-2 . These angiogenic molecules are produced by the cancer cells and by the stromal cells alike. The latter include activated tumor-activated fibroblasts and bone marrow derived cells recruited by the tumor—most notably tumor infiltrating macrophages, neutrophils, and myeloid derived suppressor cells [35, 74, 75].
Could we exploit all this knowledge for biomarker discovery? The answer is likely yes, provided that biomarker studies will be biology driven and prospectively validated [28–31, 76]. The systemic and imaging biomarkers may also play a crucial role in discovery of biomarkers for anti-angiogenic therapy and are discussed in detail elsewhere [30, 77, 78]. Here, I will discuss in the next three sections the candidate biomarkers belonging to VEGF family and to other angiogenic pathways, and the cellular biomarkers.
3. Molecular and Cellular Biomarker Candidates for Antiangiogenic Therapy
Tissue-based biomarkers are ideal because they reflect the changes occurring in a tumor during treatment, but obtaining biopsies is difficult due to the invasive nature of the procedure. Circulating molecular and cellular biomarkers found in blood are a minimally invasive alternative that can be used repeatedly over the course of treatment with an anti-angiogenic agent. Whereas changes in blood circulation may reflect the systemic effects of anti-VEGF therapy, the impact of these changes on tumor response or escape remains unclear and will need to be established in mechanistic studies in preclinical models .
3.1. VEGF Family Members as Circulating Biomarkers
VEGF expression is usually elevated both in the tumors as well as in the circulation of cancer patients and is often an indicator of poor prognosis. All the anti-angiogenic drugs that have received or are pending approval from the US Food and Drug Administration target VEGF signaling—either by blocking the ligand (bevacizumab, aflibercept) or by inhibiting the tyrosine kinase receptors (sorafenib, sunitinib, vandetanib, pazopanib, axitinib, and regorafenib). Thus, the natural choice for a biomarker has been VEGF itself. However, to date the results have been highly inconsistent . High VEGF levels are almost invariably associated with poor outcomes in correlative studies , which is indicative of its prognostic biomarker value. In some cancers (e.g., breast cancers or HCC) the levels of circulating VEGF in plasma correlated with outcome of anti-VEGF therapy [30, 56, 79]. However, in other cancers neither the intra-tumoral nor the circulating VEGF associated with outcome of bevacizumab treatment [80, 81]. For example, a recent meta-analysis across four randomized phase III trials of bevacizumab with chemotherapy or immunotherapy in metastatic colorectal cancer, advanced non-small cell lung cancer, and advanced renal cell carcinoma showed that higher baseline levels of circulating VEGF were associated with shortened progression free survival and overall survival regardless of bevacizumab treatment . This indicates that circulating VEGF levels may be prognostic but not predictive biomarkers for bevacizumab containing regimens. Moreover, the authors did not find a good correlation between blood circulating VEGF concentration and intratumor expression of VEGF . On the other hand, more recent studies have measured shorter isoforms of VEGF (e.g., VEGF121), which do not bind to the extracellular matrix components (i.e., heparin), and have found intriguing correlations with outcome . However, other studies failed to detect a significant correlation for short isoforms of VEGF . Thus, the clinical significance of circulating or tissue VEGF levels remains to be clarified, as most of the efforts to use VEGF itself as a predictive biomarker have thus far been disappointing. Current ongoing efforts to measure distinct VEGF isoforms or VEGF fragments may yield additional insight and resurrect interest in research on VEGF as predictive biomarker.
3.1.1. Other VEGF Family Members
In addition to VEGF-A (or VEGF), the VEGF family includes VEGF-B, VEGF-C, VEGF-D, and PlGF. These VEGF family members may play a role in tumor angiogenesis . Currently available antiangiogenic drugs affect these factors in a differential manner (i.e., they are not affected by bevacizumab but may be blocked by aflibercept or receptor tyrosine kinase inhibitors) . Of interest, some of these factors have been shown to be upregulated in response to anti-VEGF therapy both in patients and in preclinical models . The most consistent change has been the increase in circulating levels of plasma PlGF, which has been reported essentially for all anti-VEGF drugs and experimental agents, irrespective of their mechanism of VEGF inhibition [30, 85]. This has led to the hypotheses that (1) PlGF change may have pharmacodynamic biomarker value and (2) that PlGF increase may mediate resistance to anti-VEGF agents that do not block this molecule (e.g., bevacizumab). Both of these hypotheses need to be further validated prospectively. Of interest, the increase in PlGF may be due to systemic effects, as tumor-derived PlGF may actually be decreased after bevacizumab treatment . Similarly, VEGF-C and VEGF-D have been proposed as escape biomarkers for bevacizumab in metastatic colorectal cancer patients in other exploratory studies .
3.1.2. Soluble VEGF Receptors
As discussed above, there are 3 VEGF tyrosine kinase receptors in the plasma membrane, known as VEGFR-1 (FLT-1), VEGFR-2 (KDR), and VEGFR-3 (FLT-4). In addition to the plasma membrane receptors, soluble receptors are present in blood circulation—as a result of alternative splicing or possibly due to plasma membrane receptor shedding .
Of these soluble receptors, sVEGFR-1 has clear biological activity. This has led our group to conduct extensive studies of circulating sVEGFR-1—an endogenous blocker of VEGF and PlGF and a factor linked with “vascular normalization”—as biomarker or response to anti-VEGF agents . Our hypothesis has been that circulating plasma sVEGFR-1 is a “negative” biomarker that could be used to predict response to anti-VEGF therapies in cancer. Specifically, we propose that cancer patients with preexisting high levels of circulating sVEGFR-1 (i.e., in whom VEGF pathway is endogenously suppressed) are resistant to bevacizumab and other anti-VEGF treatments. Indeed, we have shown in exploratory studies that patients with higher plasma levels of sVEGFR-1 have a poor outcome after treatment with bevacizumab, sunitinib, vandetanib, and cediranib [88–94]. Collectively, these results suggest that anti-VEGF therapy may not have a beneficial effect in patients with high sVEGFR-1 levels. In further support of this, we also found that patients with higher sVEGFR-1 levels in circulation experienced fewer side effects from anti-VEGF treatments [88, 92, 93]. Finally, polymorphisms in the FLT1 gene that are associated with higher VEGFR1 expression have also been associated with poor outcome of bevacizumab containing regimens in phase III studies (see below) . If confirmed in larger studies, plasma sVEGFR1 may potentially allow stratification of cancer patients to regimens that include anti-VEGF therapy.
Soluble VEGFR2, which is an abundant protein in human plasma, has also been extensively studied. Multiple studies have shown that anti-VEGFR tyrosine kinase inhibitors but not bevacizumab induce a significant decrease in plasma sVEGFR-2 levels (summarized in ). The same result has been reported for circulating sVEGFR-3 (i.e., a decrease in plasma sVEGFR3 after treatment with tyrosine kinase inhibitors that block VEGFR-3). The presence of this signature has been associated with improved outcomes in some studies, but its value as a predictive or pharmacodynamic biomarkers is currently unknown [29–31].
3.2. Other Soluble Plasma Biomarker Candidates
3.2.1. Soluble Basement Membrane Components
Collagen IV is one of the main constituents of vascular basement membranes. In glioblastomas, there is an excessive deposition of basement membranes, which more than doubles the thickness tumor blood vessels compared to normal brain blood vessels [96, 97]. Vascular normalization after anti-VEGF therapy results in normalization of the vascular basement membrane—that is, a reduction in thickness—as seen in mice and in patients [96–98]. Thus, we tested the hypothesis that proteolytic degradation of these membranes could release soluble collagen IV in blood circulation and that this biomarker could be used as a measure of therapeutic efficacy. Indeed, we found that recurrent glioblastoma patients who had an increased in plasma collagen IV levels after anti-VEGF therapy had an increase in progression-free survival . If validated, either alone or in combination with imaging biomarkers of vascular normalization, the change in soluble collagen IV may potentially allow an early assessment of drug activity and stratification of glioblastoma patients to anti-VEGF therapies .
3.2.2. Inflammatory Factors
In addition to VEGF family members, many biomarker studies have focused on inflammatory cytokines and chemokines because they may exert pro-angiogenic effects either directly or indirectly (via modulation of bone marrow derived cell recruitment in circulation and infiltration in tumors) (Box 2).
A comprehensive study was conducted in patients with advanced non-small cell lung cancer who were treated with vandetanib plus chemotherapy, vandetanib alone, or chemotherapy alone. Interestingly, the patterns of changes in soluble biomarkers in each of the three study arms were distinct . Specifically, an increased risk of disease progression was associated with increases in a different marker in each arm, increased plasma VEGF levels for vandetanib monotherapy versus increase in plasma Interleukin (IL)-8 concentration for combination therapy. IL-8 may act as a VEGF-independent pro-angiogenic pathway  and has been associated with poor prognosis in hepatocellular carcinoma patients treated with sunitinib . Other notable candidates for biomarkers of tumor evasion from anti-VEGF therapy are the stromal-cell-derived factor 1 alpha (SDF1α, also referred to as CXCL12) and IL-6. We have found associations between increased plasma SDF1α after treatment and poor outcome in studies of anti-VEGF agents in recurrent glioblastoma (cediranib), sarcoma (sorafenib), and breast cancer (bevacizumab) patients [89, 92, 101–103]. Moreover, increased plasma SDF1α and plasma IL-6 have been associated with poor outcomes in locally advanced rectal cancer and advanced hepatocellular carcinoma patients treated with bevacizumab, chemoradiation, and sunitinib, respectively [94, 104]. These potential resistance biomarkers may drive the design of trials anti-VEGF agents.
3.2.3. Other Circulating Factors or Soluble Receptors
Finally, recent studies have reported significant changes or associations with outcome for other circulating factors and/or their soluble receptors. Some of the findings have been more consistent, for example, the transient decrease in plasma Ang-2 after anti-VEGF therapy [89, 90, 92]. Others appeared to be more agent/disease specific, for example, changes and correlations between circulating bFGF, platelet derived growth factor (PDGF)-BB, soluble (s)Tie2, soluble intercellular adhesion molecule 1 (sICAM-1), and matrix metalloproteinase (MMP)-2, MMP-9, and MMP-10 [87, 89, 90, 92, 94, 100, 105]. All of these biomarkers will require additional study and prospective validation.
3.3. Tissue Based Biomarkers
Whenever available—for example, when serial biopsies can be performed or when tissues are obtained at surgery or autopsy—tumor specimens have been invaluable for conducting correlative studies and gaining mechanistic insights into the effects of anti-VEGF therapies. These studies have been quite limited because of the invasive and costly nature of these procedures and the difficulty in standardizing immunohistochemical procedures.
As mentioned previously, intratumoral levels of VEGF have not been so far shown to predict survival outcome of anti-VEGF therapy [81, 82], although correlations with response rates have been reported [106, 107]. Given the disappointing data reported so far, and considering the limitations of tissue VEGF evaluation, this biomarker does not appear promising.
However, these intriguing results raised critical questions. If neither circulating nor tissue VEGF correlate with outcome of anti-VEGF agents, then what is the mechanism of action that leads to a benefit after treatment with these drugs? While multiple groups are actively exploring various mechanisms involving the vasculature, stroma, immune system, or cancer cells themselves, several emerging data are standing out. Tumor microvascular density has been often evaluated both as a predictive biomarker and as a pharmacodynamic marker of anti-angiogenic therapy with anti-VEGF agents. Indeed, two studies found a decrease in vascular density after bevacizumab treatment in rectal and breast cancer [92, 104, 108]. But other studies did not find a significant change . This effect was associated with increased apoptotic rate in cancer cells but interestingly, did not change the proliferation rate of cancer cells [108, 109]. One explanation for this paradoxical finding is that the remaining vasculature after anti-VEGF therapy is more “normal” structurally and functionally [110–113]. The association between microvascular density and survival remains unclear, with most studies reporting a lack of correlation .
In a study of serial biopsies from rectal cancers, our group has reported that while bevacizumab did no change VEGF or VEGFR expression in the cancer cells, this anti-VEGF treatment decreased PlGF and increased SDF1α and its receptor (CXCR4) expression in the rectal cancer cells . Of interest, increased plasma SDF1α levels during treatment in these patients correlated with distant disease progression pointing toward SDF1α/CXCR4 axis as a potential escape mechanism from anti-VEGF therapy [86, 102].
While enticing, these hypotheses on the mechanism of action of anti-VEGF agents remain to be further confirmed in patients, as our understanding of the dynamics of VEGFR regulation and the interactions between receptor subtypes in tumor tissue is not well enough advanced to allow the use of these levels as biomarkers of therapeutic efficacy.
Finally, genetic studies of tumor samples have also generated mixed results. While establishing the mutational status in various cancers has made a crucial impact on the development and use of anti-cancer agents, for example, KRAS mutation for cetuximab treatment in metastatic colorectal cancer and BRAF mutation for vemurafenib treatment in melanoma, it has failed so far to impact the development or the use of anti-VEGF drugs. For example, P53, KRAS, or BRAF mutations in metastatic colorectal cancer did not associate with bevacizumab-chemotherapy treatment outcome in metastatic colorectal cancer . Many studies have focused on single nucleotide polymorphisms (SNPs) in VEGF family genes as well as other genes [115–118]. Some reports found significant correlations between certain VEGF and VEGFR2 genes with survival or risk of developing hypertension after bevacizumab treatment in metastatic breast and colorectal cancer [117, 119]. However, these findings have not been yet reproduced by other studies. More recently, SNPs in VEGFR1 were shown to associate with survival after treatment with bevacizumab based regimens in 2 phase III studies in advanced pancreatic adenocarcinoma and metastatic renal cell carcinoma . These SNPs were associated with higher VEGFR1 expression . These VEGFR1 SNPs correlated with a poor outcome, which is in line with the finding that high circulating sVEGFR1 is associated with poor outcome after anti-VEGF therapy (see above) [88–94]. Also, a consistent finding appears to be the association between SNPs in CXCR2 and IL8 genes and outcome after anti-VEGF therapies [115, 116, 118, 120]. Once again, this suggests an important role that inflammatory cytokines and their receptors may play in the outcome of anti-VEGF therapy. These data strongly suggest that SNP evaluation could be used in the future to predict outcome of anti-VEGF therapy. Moreover, the evaluations of gene polymorphisms have the great advantage of being more feasible as they are minimally invasive and less expensive and do not necessarily require tumor tissue. However, only more extensive investigation and validation of the current lead candidates could potentially provide a biomarker for anti-VEGF therapy.
4. Challenges, Conclusions, and Future Perspective
One major challenge for the interpretation of molecular biomarker studies in general is that a vast amount of data was generated in single arm studies, that is, in which all patients received the same therapy. This makes the distinction between prognostic and predictive biomarkers impossible. Another challenge is that while bevacizumab and aflibercept are specific inhibitors of VEGF pathways, all the anti-angiogenic tyrosine kinase inhibitors are promiscuous, inhibiting multiple, and non-angiogenic tyrosine kinases as well as angiogenic ones [121, 122]. Therefore, it can be difficult to know whether a given biochemical or physiological effect is the result of anti-angiogenic activity or due to effects on other oncogenic targets (e.g., c-KIT inhibition by sunitinib in gastrointestinal stromal tumors or EGFR and RET inhibition by vandetanib in advanced medullary thyroid cancer). Even for bevacizumab/aflibercept studies, the interpretation is confounded by the fact that most studies included concurrent chemotherapeutic drugs, making it difficult to tease out the effects of each type of therapy.
In summary, identifying and validating predictive biomarkers of response and gaining the ability to stratify cancer patients to currently approved anti-angiogenic drugs remain major priorities in oncology. A number of potential biomarkers have emerged from correlative clinical studies that warrant further study in large randomized trials. Some such trials are now underway and their results will be critical for advancement of this field, not only for biomarker discovery but also for further elucidation of the specific mechanisms of action of these important new therapies.
Conflict of Interests
The author does not have any direct financial relation with the commercial identities mentioned in this paper.
The research of the author is supported by US National Institutes of Health Grants P01-CA080124, R01-CA159258, Federal Share National Cancer Institute Proton Beam Program Income, and the American Cancer Society Grant 120733-RSG-11-073-01-TBG. This paper uses some updated information from [31, 56].
- A. L. Cheng, Y. K. Kang, Z. Chen et al., “Efficacy and safety of sorafenib in patients in the Asia-Pacific region with advanced hepatocellular carcinoma: a phase III randomised, double-blind, placebo-controlled trial,” The Lancet Oncology, vol. 10, no. 1, pp. 25–34, 2011.
- T. F. Cloughesy, M. D. Prados, P. Wen et al., “non-comparative clinical trial of the effect of bevacizumab alone or in combination with irinotecan (CPT-11) on 6-month progression free survival in recurrent, treatment-refractory glioblastoma,” Journal of Clinical Oncology, vol. 26, abstract 2010, 2008.
- G. D. Demetri, A. T. van Oosterom, C. R. Garrett et al., “Efficacy and safety of sunitinib in patients with advanced gastrointestinal stromal tumour after failure of imatinib: a randomised controlled trial,” The Lancet, vol. 368, no. 9544, pp. 1329–1338, 2006.
- B. Escudier, T. Eisen, W. M. Stadler et al., “Sorafenib in advanced clear-cell renal-cell carcinoma,” The New England Journal of Medicine, vol. 356, no. 2, pp. 125–134, 2007.
- B. J. Giantonio, P. J. Catalano, N. J. Meropol et al., “Bevacizumab in combination with oxaliplatin, fluorouracil, and leucovorin (FOLFOX4) for previously treated metastatic colorectal cancer: results from the Eastern Cooperative Oncology Group Study E3200,” Journal of Clinical Oncology, vol. 25, no. 12, pp. 1539–1544, 2007.
- H. Hurwitz, L. Fehrenbacher, W. Novotny et al., “Bevacizumab plus irinotecan, fluorouracil, and leucovorin for metastatic colorectal cancer,” The New England Journal of Medicine, vol. 350, no. 23, pp. 2335–2342, 2004.
- J. M. Llovet, S. Ricci, V. Mazzaferro et al., “Sorafenib in advanced hepatocellular carcinoma,” The New England Journal of Medicine, vol. 359, no. 4, pp. 378–390, 2008.
- R. J. Motzer, T. E. Hutson, P. Tomczak et al., “Sunitinib versus interferon alfa in metastatic renal-cell carcinoma,” The New England Journal of Medicine, vol. 356, no. 2, pp. 115–124, 2007.
- B. I. Rini, S. Halabi, J. E. Rosenberg et al., “Phase III trial of bevacizumab plus interferon alfa versus interferon alfa monotherapy in patients with metastatic renal cell carcinoma: final results of CALGB 90206,” Journal of Clinical Oncology, vol. 28, no. 13, pp. 2137–2143, 2010.
- A. Sandler, R. Gray, M. C. Perry et al., “Paclitaxel-carboplatin alone or with bevacizumab for non-small-cell lung cancer,” The New England Journal of Medicine, vol. 355, no. 24, pp. 2542–2550, 2006.
- C. N. Sternberg, I. D. Davis, J. Mardiak et al., “Pazopanib in locally advanced or metastatic renal cell carcinoma: results of a randomized phase III trial,” Journal of Clinical Oncology, vol. 28, no. 6, pp. 1061–1068, 2010.
- E. Van Cutsem, J. Tabernero, R. Lakomy et al., “Addition of aflibercept to fluorouracil, leucovorin, and irinotecan improves survival in a phase III randomized trial in patients with metastatic colorectal cancer previously treated with an oxaliplatin-based regimen,” Journal of Clinical Oncology, vol. 30, no. 28, pp. 3499–3506, 2012.
- S. A. Wells Jr., B. G. Robinson, R. F. Gagel et al., “Vandetanib in patients with locally advanced or metastatic medullary thyroid cancer: a randomized, double-blind phase III trial,” Journal of Clinical Oncology, vol. 30, pp. 134–141, 2012.
- D. G. Duda, T. T. Batchelor, C. G. Willett, and R. K. Jain, “VEGF-targeted cancer therapy strategies: current progress, hurdles and future prospects,” Trends in Molecular Medicine, vol. 13, no. 6, pp. 223–230, 2007.
- D. G. Duda, R. K. Jain, and C. G. Willett, “Antiangiogenics: the potential role of integrating this novel treatment modality with chemoradiation for solid cancers,” Journal of Clinical Oncology, vol. 25, no. 26, pp. 4033–4042, 2007.
- L. M. Ellis, “Antiangiogenic therapy at a crossroads: clinical trial results and future directions,” Journal of Clinical Oncology, vol. 21, no. 23, supplement, pp. 281s–283s, 2003.
- F. A. L. M. Eskens, “Angiogenesis inhibitors in clinical development; where are we now and where are we going?” British Journal of Cancer, vol. 90, no. 1, pp. 1–7, 2004.
- N. Ferrara, K. J. Hillan, H. P. Gerber, and W. Novotny, “Discovery and development of bevacizumab, an anti-VEGF antibody for treating cancer,” Nature Reviews Drug Discovery, vol. 3, no. 5, pp. 391–400, 2004.
- A. Grothey and E. Galanis, “Targeting angiogenesis: progress with anti-VEGF treatment with large molecules,” Nature Reviews Clinical Oncology, vol. 6, no. 9, pp. 507–518, 2009.
- V. L. Heath and R. Bicknell, “Anticancer strategies involving the vasculature,” Nature Reviews Clinical Oncology, vol. 6, no. 7, pp. 395–404, 2009.
- R. K. Jain, “Antiangiogenic therapy for cancer: current and emerging concepts,” Oncology, vol. 19, no. 4, supplement, pp. 7–16, 2005.
- R. K. Jain, D. G. Duda, J. W. Clark, and J. S. Loeffler, “Lessons from phase III clinical trials on anti-VEGF therapy for cancer,” Nature Clinical Practice Oncology, vol. 3, no. 1, pp. 24–40, 2006.
- L. S. Rosen, “VEGF-targeted therapy: therapeutic potential and recent advances,” Oncologist, vol. 10, no. 6, pp. 382–391, 2005.
- E. Van Cutsem, D. Lambrechts, H. Prenen, R. K. Jain, and P. Carmeliet, “Lessons from the adjuvant bevacizumab trial on colon cancer: what next?” Journal of Clinical Oncology, vol. 29, no. 1, pp. 1–4, 2011.
- H. M. W. Verheul and H. M. Pinedo, “Possible molecular mechanisms involved in the toxicity of angiogenesis inhibition,” Nature Reviews Cancer, vol. 7, no. 6, pp. 475–485, 2007.
- T. Fojo and C. Grady, “How much is life worth: cetuximab, non-small cell lung cancer, and the $440 billion question,” Journal of the National Cancer Institute, vol. 101, no. 15, pp. 1044–1048, 2009.
- A. T. Fojo and D. R. Parkinson, “Biologically targeted cancer therapy and marginal benefits: are we making too much of too little or are we achieving too little by giving too much?” Clinical Cancer Research, vol. 16, no. 24, pp. 5972–5980, 2010.
- Biomarkers Definitions Working Group, “Biomarkers and surrogate endpoints: preferred definitions and conceptual framework,” Clinical pharmacology and therapeutics, vol. 69, no. 3, pp. 89–95, 2001.
- N. Murukesh, C. Dive, and G. C. Jayson, “Biomarkers of angiogenesis and their role in the development of VEGF inhibitors,” British Journal of Cancer, vol. 102, no. 1, pp. 8–18, 2010.
- R. K. Jain, D. G. Duda, C. G. Willett et al., “Biomarkers of response and resistance to antiangiogenic therapy,” Nature Reviews Clinical Oncology, vol. 6, no. 6, pp. 327–338, 2009.
- D. G. Duda, “Targeting tumor angiogenesis: biomarkers of angiogenesis and antiangiogenic therapy in cancer,” Angiogenesis Foundation e-publication, 2011, http://www.angio.org/cme/biom.php.
- L. M. Coussens and Z. Werb, “Inflammation and cancer,” Nature, vol. 420, no. 6917, pp. 860–867, 2002.
- A. Mantovani, P. Allavena, A. Sica, and F. Balkwill, “Cancer-related inflammation,” Nature, vol. 454, no. 7203, pp. 436–444, 2008.
- W. E. Naugler and M. Karin, “The wolf in sheep's clothing: the role of interleukin-6 in immunity, inflammation and cancer,” Trends in Molecular Medicine, vol. 14, no. 3, pp. 109–119, 2008.
- J. W. Pollard, “Tumour-educated macrophages promote tumour progression and metastasis,” Nature Reviews Cancer, vol. 4, no. 1, pp. 71–78, 2004.
- G. He, G. Y. Yu, V. Temkin et al., “Hepatocyte IKKβ/NF-κB inhibits tumor promotion and progression by preventing oxidative stress-driven STAT3 activation,” Cancer Cell, vol. 17, no. 3, pp. 286–297, 2010.
- E. J. Park, J. H. Lee, G. Y. Yu et al., “Dietary and genetic obesity promote liver inflammation and tumorigenesis by enhancing IL-6 and TNF expression,” Cell, vol. 140, no. 2, pp. 197–208, 2010.
- E. Pikarsky, R. M. Porat, I. Stein et al., “NF-κB functions as a tumour promoter in inflammation-associated cancer,” Nature, vol. 431, no. 7007, pp. 461–466, 2004.
- M. Belakavadi and B. P. Salimath, “Mechanism of inhibition of ascites tumor growth in mice by curcumin is mediated by NF-kB and caspase activated DNase,” Molecular and Cellular Biochemistry, vol. 273, no. 1-2, pp. 57–67, 2005.
- T. P. Hamsa and G. Kuttan, “GAntiangiogenic activity of berberine is mediated through the downregulation of hypoxia-inducible factor-1, VEGF, and proinflammatory mediators,” Drug and Chemical Toxicology, vol. 35, pp. 57–70, 2012.
- J. Rhode, S. Fogoros, S. Zick et al., “Ginger inhibits cell growth and modulates angiogenic factors in ovarian cancer cells,” BMC Complementary and Alternative Medicine, vol. 7, article 44, 2007.
- A. Shibata, T. Nagaya, T. Imai, H. Funahashi, A. Nakao, and H. Seo, “Inhibition of NF-κB activity decreases the VEGF mRNA expression in MDA-MB-231 breast cancer cells,” Breast Cancer Research and Treatment, vol. 73, no. 3, pp. 237–243, 2002.
- L. Veschini, D. Belloni, C. Foglieni et al., “Hypoxia-inducible transcription factor-1 alpha determines sensitivity of endothelial cells to the proteosome inhibitor bortezomib,” Blood, vol. 109, no. 6, pp. 2565–2570, 2007.
- M. Wu, C. Huang, X. Li et al., “LRRC4 inhibits glioblastoma cell proliferation, migration, and angiogenesis by downregulating pleiotropic cytokine expression and responses,” Journal of Cellular Physiology, vol. 214, no. 1, pp. 65–74, 2008.
- W. Zhang, X. D. Zhu, H. C. Sun et al., “Depletion of tumor-associated macrophages enhances the effect of sorafenib in metastatic liver cancer models by antimetastatic and antiangiogenic effects,” Clinical Cancer Research, vol. 16, no. 13, pp. 3420–3430, 2010.
- J. D. Zhao, J. Liu, Z. G. Ren et al., “Maintenance of Sorafenib following combined therapy of three-dimensional conformal radiation therapy/intensity-modulated radiation therapy and transcatheter arterial chemoembolization in patients with locally advanced hepatocellular carcinoma: a phase I/II study,” Radiation Oncology, vol. 5, no. 1, article 12, 2010.
- Y. Carmi, E. Voronov, S. Dotan et al., “The role of macrophage-derived IL-1 in induction and maintenance of angiogenesis,” Journal of Immunology, vol. 183, no. 7, pp. 4705–4714, 2009.
- T. Sakurai, G. He, A. Matsuzawa et al., “Hepatocyte necrosis induced by oxidative stress and IL-1α release mediate carcinogen-induced compensatory proliferation and liver tumorigenesis,” Cancer Cell, vol. 14, no. 2, pp. 156–165, 2008.
- G. Germano, P. Allavena, and A. Mantovani, “Cytokines as a key component of cancer-related inflammation,” Cytokine, vol. 43, no. 3, pp. 374–379, 2008.
- F. Kubo, S. Ueno, K. Hiwatashi et al., “Interleukin 8 in human hepatocellular carcinoma correlates with cancer cell invasion of vessels but not with tumor angiogenesis,” Annals of Surgical Oncology, vol. 12, no. 10, pp. 800–807, 2005.
- Y. Mizukami, W. S. Jo, E. M. Duerr et al., “Induction of interleukin-8 preserves the angiogenic response in HIF-1α-deficient colon cancer cells,” Nature Medicine, vol. 11, no. 9, pp. 992–997, 2005.
- D. J. Brat, A. C. Bellail, and E. G. Van Meir, “The role of interleukin-8 and its receptors in gliomagenesis and tumoral angiogenesis,” Neuro-Oncology, vol. 7, no. 2, pp. 122–133, 2005.
- M. Grunewald, I. Avraham, Y. Dor et al., “VEGF-induced adult neovascularization: recruitment, retention, and role of accessory cells,” Cell, vol. 124, no. 1, pp. 175–189, 2006.
- W. Li, E. Gomez, and Z. Zhang, “Immunohistochemical expression of stromal cell-derived factor-1 (SDF-1) and CXCR4 ligand receptor system in hepatocellular carcinoma,” Journal of Experimental and Clinical Cancer Research, vol. 26, no. 4, pp. 527–533, 2007.
- T. Mansuroglu, P. Ramadori, J. Dudás et al., “Expression of stem cell factor and its receptor c-Kit during the development of intrahepatic cholangiocarcinoma,” Laboratory Investigation, vol. 89, no. 5, pp. 562–574, 2009.
- A. X. Zhu, D. G. Duda, D. V. Sahani, and R. K. Jain, “HCC and angiogenesis: possible targets and future directions,” Nature Reviews Clinical Oncology, vol. 8, no. 5, pp. 292–301, 2011.
- P. B. Chapman, A. Hauschild, C. Robert et al., “Improved survival with vemurafenib in melanoma with BRAF V600E mutation,” The New England Journal of Medicine, vol. 364, no. 26, pp. 2507–2516, 2011.
- C. S. Karapetis, S. Khambata-Ford, D. J. Jonker et al., “K-ras mutations and benefit from cetuximab in advanced colorectal cancer,” The New England Journal of Medicine, vol. 359, no. 17, pp. 1757–1765, 2008.
- D. J. Slamon, B. Leyland-Jones, S. Shak et al., “Use of chemotherapy plus a monoclonal antibody against her2 for metastatic breast cancer that overexpresses HER2,” The New England Journal of Medicine, vol. 344, no. 11, pp. 783–792, 2001.
- P. Carmeliet and R. K. Jain, “Molecular mechanisms and clinical applications of angiogenesis,” Nature, vol. 473, no. 7347, pp. 298–307, 2011.
- H. F. Dvorak, “Vascular permeability factor/vascular endothelial growth factor: a critical cytokine in tumor angiogenesis and a potential target for diagnosis and therapy,” Journal of Clinical Oncology, vol. 20, no. 21, pp. 4368–4380, 2002.
- N. Ferrara, H. P. Gerber, and J. LeCouter, “The biology of VEGF and its receptors,” Nature Medicine, vol. 9, no. 6, pp. 669–676, 2003.
- J. Folkman, “Tumor angiogenesis: therapeutic implications,” The New England Journal of Medicine, vol. 285, no. 21, pp. 1182–1186, 1971.
- J. Folkman, “Angiogenesis: an organizing principle for drug discovery?” Nature Reviews Drug Discovery, vol. 6, no. 4, pp. 273–286, 2007.
- P. Carmeliet, “Angiogenesis in life, disease and medicine,” Nature, vol. 438, no. 7070, pp. 932–936, 2005.
- P. Carmeliet, V. Ferreira, G. Breier et al., “Abnormal blood vessel development and lethality in embryos lacking a single VEGF allele,” Nature, vol. 380, no. 6573, pp. 435–439, 1996.
- N. Ferrara, K. Carver-Moore, H. Chen et al., “Heterozygous embryonic lethality induced by targeted inactivation of the VEGF gene,” Nature, vol. 380, no. 6573, pp. 439–442, 1996.
- R. K. Jain, “Molecular regulation of vessel maturation,” Nature Medicine, vol. 9, no. 6, pp. 685–693, 2003.
- M. Mazzone, D. Dettori, R. Leite de Oliveira et al., “Heterozygous deficiency of PHD2 restores tumor oxygenation and inhibits metastasis via endothelial normalization,” Cell, vol. 136, no. 5, pp. 839–851, 2009.
- J. C. Chappell, S. M. Taylor, N. Ferrara, and V. L. Bautch, “Local guidance of emerging vessel sprouts requires soluble Flt-1,” Developmental Cell, vol. 17, no. 3, pp. 377–386, 2009.
- R. J. Levine, S. E. Maynard, C. Qian et al., “Circulating angiogenic factors and the risk of preeclampsia,” The New England Journal of Medicine, vol. 350, no. 7, pp. 672–683, 2004.
- S. E. Maynard, J. Y. Min, J. Merchan et al., “Excess placental soluble fms-like tyrosine kinase 1 (sFlt1) may contribute to endothelial dysfunction hypertension, and proteinuria in preeclampsia,” Journal of Clinical Investigation, vol. 111, no. 5, pp. 649–658, 2003.
- T. Tammela, G. Zarkada, E. Wallgard et al., “Blocking VEGFR-3 suppresses angiogenic sprouting and vascular network formation,” Nature, vol. 454, no. 7204, pp. 656–660, 2008.
- D. Hanahan and L. M. Coussens, “Accessories to the crime: functions of cells recruited to the tumor microenvironment,” Cancer Cell, vol. 21, pp. 309–322, 2012.
- C. Murdoch, M. Muthana, S. B. Coffelt, and C. E. Lewis, “The role of myeloid cells in the promotion of tumour angiogenesis,” Nature Reviews Cancer, vol. 8, no. 8, pp. 618–631, 2008.
- J. W. Park, R. S. Kerbel, G. J. Kelloff et al., “Rationale for biomarkers and surrogate end points in mechanism-driven oncology drug development,” Clinical Cancer Research, vol. 10, no. 11, pp. 3885–3896, 2004.
- J. M. Collins, “Imaging and other biomarkers in early clinical studies: one step at a time or re-engineering drug development?” Journal of Clinical Oncology, vol. 23, no. 24, pp. 5417–5419, 2005.
- S. M. Galbraith, “Antivascular cancer treatments: Imaging biomarkers in pharmaceutical drug development,” British Journal of Radiology, vol. 76, no. 1, pp. S83–S86, 2003.
- D. W. Miles, S. L. de Haas, L. Dirix et al., “Plasma biomarker analyses in the AVADO phase III randomized study of first-line bevacizumab + docetaxel in patients with human epidermal growth factor receptor (HER) 2-negative metastatic breast cancer,” Cancer Research, vol. 70, abstract P2-16-04, 2010.
- A. Dowlati, R. Gray, D. H. Johnson, J. H. Schiller, J. Brahmer, and A. B. Sandler, “Prospective correlative assessment of biomarkers in E4599 randomized phase II/III trial of carboplatin and paclitaxel ± bevacizumab in advanced non-small cell lung cancer (NSCLC),” Journal of Clinical Oncology, vol. 24, p. 7027, 2006.
- A. M. Jubb, H. I. Hurwitz, W. Bai et al., “Impact of vascular endothelial growth factor-A expression, thrombospondin-2 expression, and microvessel density on the treatment effect of bevacizumab in metastatic colorectal cancer,” Journal of Clinical Oncology, vol. 24, no. 2, pp. 217–227, 2006.
- C. Bernaards, P. Hegde, D. Chen et al., “Circulating vascular endothelial growth factor (VEGF) as a biomarker for bevacizumab-based therapy in metastatic colorectal, non-small cell lung, and renal cell cancers: analysis of phase III studies,” Journal of Clinical Oncology, vol. 28, supplement, abstract 10519, no. 15, 2010.
- E. Van Cutsem, S. de Haas, Y. K. Kang et al., “Bevacizumab in combination with chemotherapy as first-line therapy in advanced gastric cancer: a biomarker evaluation from the AVAGAST randomized phase III trial,” Journal of Clinical Oncology, vol. 30, pp. 2119–2127, 2012.
- G. C. Jayson, S. de Haas, P. Delmar et al., “Evaluation of plasma VEGFA as a potential predictive pan-tumour biomarker for bevacizumab,” European Journal of Cancer, vol. 47, article S96, 2011.
- N. S. Horowitz, R. T. Penson, D. G. Duda et al., “Safety, efficacy and biomarker exploration in a phase II study of bevacizumab, oxaliplatin and gemcitabine in recurrent Müllerian carcinoma,” Clinical Ovarian Cancer, vol. 4, no. 1, pp. 26–33, 2011.
- L. Xu, D. G. Duda, E. di Tomaso et al., “Direct evidence that bevacizumab, an anti-VEGF antibody, up-regulates SDF1α, CXCR4, CXCL6, and neuropilin 1 in tumors from patients with rectal cancer,” Cancer Research, vol. 69, no. 20, pp. 7905–7910, 2009.
- C. H. Lieu, H. T. Tran, Z. Jiang et al., “The association of alternate VEGF ligands with resistance to anti-VEGF therapy in metastatic colorectal cancer,” Journal of Clinical Oncology, vol. 29, supplement, abstract 3533, 2011.
- D. G. Duda, C. G. Willett, M. Ancukiewicz et al., “Plasma soluble VEGFR-1 is a potential dual biomarker of response and toxicity for bevacizumab with chemoradiation in locally advanced rectal cancer,” Oncologist, vol. 15, no. 6, pp. 577–583, 2010.
- T. T. Batchelor, D. G. Duda, E. di Tomaso et al., “Phase II study of cediranib, an oral pan-vascular endothelial growth factor receptor tyrosine kinase inhibitor, in patients with recurrent glioblastoma,” Journal of Clinical Oncology, vol. 28, no. 17, pp. 2817–2823, 2010.
- E. R. Gerstner, K. E. Emblem, A. S. Chi et al., “Effects of cediranib, a VEGF signaling inhibitor, in combination with chemoradiation on tumor blood flow and survival in newly diagnosed glioblastoma,” Journal of Clinical Oncology, vol. 30, supplement, abstract 2009, 2012.
- J. A. Meyerhardt, M. Ancukiewicz, T. A. Abrams et al., “Phase I study of cetuximab, irinotecan, and vandetanib (ZD6474) as therapy for patients with previously treated metastastic colorectal cancer,” PLoS ONE, vol. 7, Article ID e38231, 2012.
- S. M. Tolaney, D. G. Duda, Y. Boucher et al., “A phase II study of preoperative (preop) bevacizumab (bev) followed by dose-dense (dd) doxorubicin (A)/cyclophosphamide (C)/paclitaxel (T) in combination with bev in HER2-negative operable breast cancer (BC),” Journal of Clinical Oncology, vol. 30, supplement, abstract 1026, 2012.
- A. X. Zhu, M. Ancukiewicz, J. G. Supko et al., “Clinical, pharmacodynamic (PD), and pharmacokinetic (PK) evaluation of cediranib in advanced hepatocellular carcinoma (HCC): a phase II study (CTEP, 7147),” Journal of Clinical Oncology, vol. 30, supplement, abstract 4112, 2012.
- A. X. Zhu, D. V. Sahani, D. G. Duda et al., “Efficacy, safety, and potential biomarkers of sunitinib monotherapy in advanced hepatocellular carcinoma: a phase II study,” Journal of Clinical Oncology, vol. 27, no. 18, pp. 3027–3035, 2009.
- D. Lambrechts, B. Claes, P. Delmar et al., “VEGF pathway genetic variants as biomarkers of treatment outcome with bevacizumab: an analysis of data from the AViTA and AVOREN randomised trials,” The Lancet Oncology, vol. 13, no. 7, pp. 724–733, 2012.
- W. S. Kamoun, C. D. Ley, C. T. Farrar et al., “Edema control by cediranib, a vascular endothelial growth factor receptor-targeted kinase inhibitor, prolongs survival despite persistent brain tumor growth in mice,” Journal of Clinical Oncology, vol. 27, no. 15, pp. 2542–2552, 2009.
- F. Winkler, S. V. Kozin, R. T. Tong et al., “Kinetics of vascular normalization by VEGFR2 blockade governs brain tumor response to radiation: role of oxygenation, angiopoietin-1, and matrix metalloproteinases,” Cancer Cell, vol. 6, no. 6, pp. 553–563, 2004.
- E. di Tomaso, M. Snuderl, W. S. Kamoun et al., “Glioblastoma recurrence after cediranib therapy in patients: lack of “rebound” revascularization as mode of escape,” Cancer Research, vol. 71, no. 1, pp. 19–28, 2011.
- A. G. Sorensen, T. T. Batchelor, W. T. Zhang et al., “A “vascular normalization index” as potential mechanistic biomarker to predict survival after a single dose of cediranib in recurrent glioblastoma patients,” Cancer Research, vol. 69, no. 13, pp. 5296–5300, 2009.
- E. O. Hanrahan, H. Y. Lin, E. S. Kim et al., “Distinct patterns of cytokine and angiogenic factor modulation and markers of benefit for vandetanib and/or chemotherapy in patients with non-small-cell lung cancer,” Journal of Clinical Oncology, vol. 28, no. 2, pp. 193–201, 2010.
- T. T. Batchelor, A. G. Sorensen, E. di Tomaso et al., “AZD2171, a pan-VEGF receptor tyrosine kinase inhibitor, normalizes tumor vasculature and alleviates edema in glioblastoma patients,” Cancer Cell, vol. 11, no. 1, pp. 83–95, 2007.
- D. G. Duda, S. V. Kozin, N. D. Kirkpatrick, L. Xu, D. Fukumura, and R. K. Jain, “CXCL12 (SDF1α)-CXCR4/CXCR7 pathway inhibition: an emerging sensitizer for anticancer therapies?” Clinical Cancer Research, vol. 17, no. 8, pp. 2074–2080, 2011.
- C. P. Raut, Y. Boucher, D. G. Duda et al., “Effects of sorafenib on intra-tumoral interstitial fluid pressure and circulating biomarkers in patients with refractory sarcomas (NCI protocol 6948),” PLoS ONE, vol. 7, Article ID e26331, 2012.
- C. G. Willett, D. G. Duda, E. Di Tomaso et al., “Efficacy, safety, and biomarkers of neoadjuvant bevacizumab, radiation therapy, and fluorouracil in rectal cancer: a multidisciplinary phase II study,” Journal of Clinical Oncology, vol. 27, no. 18, pp. 3020–3026, 2009.
- S. Kopetz, P. M. Hoff, J. S. Morris et al., “Phase II trial of infusional fluorouracil, irinotecan, and bevacizumab for metastatic colorectal cancer: efficacy and circulating angiogenic biomarkers associated with therapeutic resistance,” Journal of Clinical Oncology, vol. 28, no. 3, pp. 453–459, 2010.
- D. Foernzler, P. Delmar, M. Kockx, J. Cassidy, L. Saltz, and S. Scherer, “Tumor tissue based biomarker analysis in NO16966: a randomized phase III study of first-line bevacizumab in combination with oxaliplatin-based chemotherapy in patients with mCR,” Gastrointestinal Cancers Symposium Proceedings Abstract 374, 2010.
- S. X. Yang, S. M. Steinberg, D. Nguyen, T. D. Wu, Z. Modrusan, and S. M. Swain, “Gene expression profile and angiogenic marker correlates with response to neoadjuvant bevacizumab followed by bevacizumab plus chemotherapy in breast cancer,” Clinical Cancer Research, vol. 14, no. 18, pp. 5893–5899, 2008.
- C. G. Willett, Y. Boucher, D. G. Duda et al., “Surrogate markers for antiangiogenic therapy and dose-limiting toxicities for bevacizumab with radiation and chemotherapy: continued experience of a phase I trial in rectal cancer patients,” Journal of Clinical Oncology, vol. 23, no. 31, pp. 8136–8139, 2005.
- S. B. Wedam, J. A. Low, S. X. Yang et al., “Antiangiogenic and antitumor effects of bevacizumab in patients with inflammatory and locally advanced breast cancer,” Journal of Clinical Oncology, vol. 24, no. 5, pp. 769–777, 2006.
- S. Goel, D. G. Duda, L. Xu et al., “Normalization of the vasculature for treatment of cancer and other diseases,” Physiological Reviews, vol. 91, no. 3, pp. 1071–1121, 2011.
- R. K. Jain, “Normalizing tumor vasculature with anti-angiogenic therapy: a new paradigm for combination therapy,” Nature Medicine, vol. 7, no. 9, pp. 987–989, 2001.
- R. K. Jain, “Normalization of tumor vasculature: an emerging concept in antiangiogenic therapy,” Science, vol. 307, no. 5706, pp. 58–62, 2005.
- R. K. Jain, “Taming vessels to treat cancer,” Scientific American, vol. 298, no. 1, pp. 56–63, 2008.
- W. L. Ince, A. M. Jubb, S. N. Holden et al., “Association of k-ras, b-raf, and p53 status with the treatment effect of bevacizumab,” Journal of the National Cancer Institute, vol. 97, no. 13, pp. 981–989, 2005.
- A. Gerger, A. El-Khoueiry, W. Zhang et al., “Pharmacogenetic angiogenesis profiling for first-line Bevacizumab plus oxaliplatin-based chemotherapy in patients with metastatic colorectal cancer,” Clinical Cancer Research, vol. 17, pp. 5783–5792, 2011.
- L. lo Giudice, M. Di Salvatore, Astone et al., “Polymorphisms in VEGF, eNOS, COX-2, and IL-8 as predictive markers of response to bevacizumab,” Journal of Clinical Oncology, vol. 28, supplement, abstract e13502, 2010.
- F. Loupakis, A. Ruzzo, L. Salvatore et al., “Retrospective exploratory analysis of VEGF polymorphisms in the prediction of benefit from first-line FOLFIRI plus bevacizumab in metastatic colorectal cancer,” BMC Cancer, vol. 11, article 247, 2011.
- A. M. Schultheis, G. Lurje, K. E. Rhodes et al., “Polymorphisms and clinical outcome in recurrent ovarian cancer treated with cyclophosphamide and bevacizumab,” Clinical Cancer Research, vol. 14, no. 22, pp. 7554–7563, 2008.
- B. P. Schneider, M. Wang, M. Radovich et al., “Association of vascular endothelial growth factor and vascular endothelial growth factor receptor-2 genetic polymorphisms with outcome in a trial of paclitaxel compared with paclitaxel plus bevacizumab in advanced breast cancer: ECOG 2100,” Journal of Clinical Oncology, vol. 26, no. 28, pp. 4672–4678, 2008.
- W. W. Zhang, J. E. Cortes, H. Yao et al., “Predictors of primary imatinib resistance in chronic myelogenous leukemia are distinct from those in secondary imatinib resistance,” Journal of Clinical Oncology, vol. 27, no. 22, pp. 3642–3649, 2009.
- D. G. Duda, M. Ancukiewicz, and R. K. Jain, “Biomarkers of antiangiogenic therapy: how do we move from candidate biomarkers to valid biomarkers?” Journal of Clinical Oncology, vol. 28, no. 2, pp. 183–185, 2010.
- A. X. Zhu, D. G. Duda, D. V. Sahani, and R. K. Jain, “Development of sunitinib in hepatocellular carcinoma: rationale, early clinical experience, and correlative studies,” Cancer Journal, vol. 15, no. 4, pp. 263–268, 2009.
Copyright © 2012 Dan G. Duda. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.