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Disease Markers
Volume 2014 (2014), Article ID 671283, 3 pages
http://dx.doi.org/10.1155/2014/671283
Research Article

Molecular Targeted Approaches for Advanced BRAF V600, N-RAS, c-KIT, and GNAQ Melanomas

1Department of Clinical and Diagnostic Medicine and Public Health, University of Modena and Reggio Emilia, Via del Pozzo 71, 41100 Modena, Italy
2Department of Dermatology, University of Modena and Reggio Emilia, Via del Pozzo 71, 41100 Modena, Italy
3Department of Plastic and Reconstructive Surgery, University of Modena and Reggio Emilia, Via del Pozzo 71, 41100 Modena, Italy
4Department of Medical Oncology, University of Modena and Reggio Emilia, Via del Pozzo 71, 41100 Modena, Italy
5Dermatology & Skin Cancer Unit, Arcispedale Santa Maria Nuova, IRCCS, Reggio Emilia, Italy

Received 10 June 2013; Revised 19 November 2013; Accepted 19 November 2013; Published 23 January 2014

Academic Editor: Dinesh Kumbhare

Copyright © 2014 Ponti Giovanni et al. 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.

Abstract

The introduction of a newly developed target therapy for metastatic melanomas poses the challenge to have a good molecular stratification of those patients who may benefit from this therapeutic option. Practically, BRAF mutation status (V600E) is commonly screened although other non-V600E mutations (i.e., K-R-M-D) could be found in some patients who respond to therapy equally to the patients harboring V600E mutations. Furthermore, other mutations, namely, N-RAS, KIT, and GNAQ, should be sequenced according to distinct melanoma specific subtypes and clinical aspects. In our report, a practical flow chart is described along with our experience in this field.


After decades of unsatisfactory treatments for advanced melanoma, in the last five years, new treatment modalities have been explored that dramatically change the current clinic scenario. The introduction of targeted therapies for melanoma is based on the discovery of genes that are linked to the initiation, progression, and invasion of the tumor [1]. More specifically, somatic mutations in the BRAF, NRAS, KIT, and GNAQ genes are critical to correctly stage and manage patients with metastatic disease who can nowadays benefit from these modern molecular targeted therapies. The mutations affect receptor tyrosine kinases and the MAPK and MTOR pathways display different frequencies in distinct histopathological subtypes of melanoma [2].

Somatic mutations in BRAF have been found in almost 50% of all melanomas [3, 4] and most commonly in melanomas derived from skin without chronic sun-induced damage [5]. The result of these mutations (mainly V600E) is enhanced BRAF kinase activity and increased phosphorylation of downstream targets, particularly MEK.

In particular, BRAF inhibitors, targeting the common V600E mutations, have become increasingly popular since they have a high objective response rate and few side effects.

In a previous study we demonstrated that patients harboring uncommon BRAF V600R-M-D mutations, not included in the original experimental protocols of BRAF selective inhibitors, were the responders to the therapy. Surprisingly, patients harboring non-V600E BRAF mutations revealed an objective clinical response similar to V600E melanoma patients [6, 7].

In the clinical setting, BRAF mutations are routinely screened but when BRAF mutation is not detected, melanomas should be screened for N-RAS, KIT, and GNAQ mutations.

RAS genes are mutated in up to 20% of melanomas which are typically thicker and have a higher mitotic rate [8]. Higher frequency of KIT mutation in melanoma is associated with older patients and the acral and mucosal melanoma subtypes [8]. Somatic mutations in the GNAQ and GNA11 genes are found in 80% of uveal melanomas [9]. Nowadays, patients with N-RAS, KIT, and GNAQ mutated tumors can be enrolled in clinical trials of specific inhibitors [2, 811].

In the experience of our institution, thirty-two BRAF mutated melanomas (32%) were detected among 99 melanomas screened for genetic mutations. Among BRAF mutation-negative melanomas, 6 N-RAS mutations (four Q61R, one Q61K, and one Q61L) and 3 KIT mutations (N822K) were found. The lower BRAF mutation rate found in our study compared to the literature might be due to a selection bias since we screened only patients with metastatic disease.

Hot spot V600E mutations were found in 27 patients. V600R mutation and double (V600E-V600M) mutation were identified in two melanomas. In five cases, V600K mutations were found. Two screening failures were noted.

Twenty-three patients with BRAF mutated metastatic melanoma were enrolled in the protocol with BRAF inhibitors for compassionate use at the University of Modena. Two N-RAS mutated patients were enrolled in an alternative anti-NRAS protocol in another University. Mean progression-free survival for BRAF positive patients at followup of 8 weeks was 7.6 months (Table 1) (Figure 1). There was no statistically significant difference in the duration of the objective tumor response among different BRAF status groupings. An objective response with few side effects was observed in all except one patient (Table 2).

tab1
Table 1: Patients treated with BRAF and NRAS inhibitors.
tab2
Table 2: Patients treated with BRAF inhibitors: frequencies of side effects.
671283.fig.001
Figure 1: Clinical features of patients treated with BRAF inhibitors.
Based on our preliminary findings, we propose a stepwise model to characterize the mutational status of melanomas.(1)Screen for V600E BRAF mutation in melanoma patients with advanced disease (i.e., unresectable stages III and IV) as well as those at high risk of disease progression (stages IIIB and IIIC).(2)In case of negative-V600E BRAF mutation, look for other non-V600E BRAF mutations (i.e., K, M, R, D).(3)Melanomas not showing BRAF mutations should be investigated for N-RAS mutations.(4)Double-negative BRAF and N-RAS melanomas should be further explored for KIT mutations or amplifications. This is even more relevant for acral and mucosal melanomas that should be investigated for both BRAF and KIT mutations at the first step.(5)Triple-negative melanomas may benefit from GNAQ mutation evaluation, especially for uveal melanoma.

For melanoma, like other cancers, tailored therapies are dramatically changing the current approaches for treating patients with metastatic disease. However, the heterogeneous molecular defects in melanoma account for the development of drug resistance and thus the different clinical objective responses of targeted therapies. It is known that resistance to BRAF inhibitors is due to either the acquisition of secondary mutations in the BRAF gene or upregulation of other molecular pathways such as platelet-derived growth factor receptor β or N-RAS, the consequences of which lead to resistance to MEK and ERK inhibitors [12, 13]. Independent research teams have identified three mechanisms by which melanoma can develop resistance to BRAF inhibitors [13, 14]. The findings suggest that BRAF inhibitors will need to be combined with other types of drugs, although future studies will have to determine the relative frequency of each mechanism. To conclude, future efforts will be directed not only to develop multitargeted therapies (i.e., BRAF and MEK inhibitors) but also to further investigate the combination of target treatments and promising immune-therapy approach.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

References

  1. P. A. Ascierto, J. M. Kirkwood, J.-J. Grob et al., “The role of BRAF V600 mutation in melanoma,” Journal of Translational Medicine, vol. 10, article 85, 2012. View at Publisher · View at Google Scholar · View at Scopus
  2. S. Y. Morita and S. N. Markovic, “Molecular targets in melanoma: time for ‘ethnic personalization’,” Expert Review of Anticancer Therapy, vol. 12, no. 5, pp. 601–608, 2012. View at Google Scholar
  3. H. Davies, G. R. Bignell, C. Cox et al., “Mutations of the BRAF gene in human cancer,” Nature, vol. 417, no. 6892, pp. 949–954, 2002. View at Publisher · View at Google Scholar
  4. J. L. Maldonado, J. Fridlyand, H. Patel et al., “Determinants of BRAF mutations in primary melanomas,” Journal of the National Cancer Institute, vol. 95, no. 24, pp. 1878–1890, 2003. View at Publisher · View at Google Scholar
  5. J. A. Curtin, J. Fridlyand, T. Kageshita et al., “Distinct sets of genetic alterations in melanoma,” The New England Journal of Medicine, vol. 353, no. 20, pp. 2135–2147, 2005. View at Publisher · View at Google Scholar · View at Scopus
  6. G. Ponti, G. Pellacani, A. Tomasi et al., “The somatic affairs of BRAF: tailored therapies for advanced malignant melanoma and orphan non-V600E (V600R-M) mutations,” Journal of Clinical Pathology, vol. 66, no. 5, pp. 441–445, 2013. View at Google Scholar
  7. G. Ponti, A. Tomasi, and G. Pellacani, “Overwhelming response to Dabrafenib in a patient with double BRAF mutation (V600E, V600M) metastatic malignant melanoma,” Journal of Hematology & Oncology, vol. 5, article 60, 2012. View at Google Scholar
  8. J. A. Curtin, K. Busam, D. Pinkel, and B. C. Bastian, “Somatic activation of KIT in distinct subtypes of melanoma,” Journal of Clinical Oncology, vol. 24, no. 26, pp. 4340–4346, 2006. View at Publisher · View at Google Scholar · View at Scopus
  9. G. Ambrosini, C. A. Pratilas, L. X. Qin et al., “Identification of unique MEK-dependent genes in GNAQ mutant uveal melanoma involved in cell growth, tumor cell invasion, and MEK resistance,” Clinical Cancer Research, vol. 18, no. 13, pp. 3552–3561, 2012. View at Google Scholar
  10. G. Ambrosini, E. Musi, A. L. Ho, E. de Stanchina, and G. K. Schwartz, “Inhibition of mutant GNAQ signaling in uveal melanoma induces AMPK-dependent autophagic cell death,” Molecular Cancer Therapeutics, vol. 12, no. 5, pp. 768–776, 2013. View at Google Scholar
  11. S. Abu-Abed, N. Pennell, T. Petrella, F. Wright, A. Seth, and W. Hanna, “KIT gene mutations and patterns of protein expression in mucosal and acral melanoma,” Journal of Cutaneous Medicine and Surgery, vol. 16, no. 2, pp. 135–142, 2012. View at Publisher · View at Google Scholar · View at Scopus
  12. H. Shi, X. Kong, A. Ribas, and R. S. Lo, “Combinatorial treatments that overcome PDGFRβ-driven resistance of melanoma cells toV600EB-RAF inhibition,” Cancer Research, vol. 71, no. 15, pp. 5067–5074, 2011. View at Publisher · View at Google Scholar · View at Scopus
  13. R. Nazarian, H. Shi, Q. Wang et al., “Melanomas acquire resistance to B-RAF(V600E) inhibition by RTK or N-RAS upregulation,” Nature, vol. 468, no. 7326, pp. 973–977, 2010. View at Publisher · View at Google Scholar · View at Scopus
  14. C. M. Johannessen, J. S. Boehm, S. Y. Kim et al., “COT drives resistance to RAF inhibition through MAP kinase pathway reactivation,” Nature, vol. 468, no. 7326, pp. 968–972, 2010. View at Publisher · View at Google Scholar · View at Scopus