The Role of Viruses and Bacteria in Oncogenesis: Future Perspectives on Prevention and Treatment
1University of Palermo, Palermo, Italy
2International Agency for Research on Cancer (IARC), Lyon, France
3The Chinese University of Hong Kong, Shatin, Hong Kong
4Institute Pasteur de Tunis, Tunis, Tunisia
The Role of Viruses and Bacteria in Oncogenesis: Future Perspectives on Prevention and Treatment
Description
Cancer is considered a multifactorial disease determined by the interaction between both environmental and genetic factors. Infection by biological agents such as viruses, bacteria, and parasites is strong risk factor for specific cancers. Based on epidemiological and biological studies, the International Agency for Research Cancer (IARC) has classified eleven infectious agents as human carcinogens (Group 1). Infectious agents in this group include Epstein-Barr virus (EBV), hepatitis C virus (HCV), hepatitis B virus (HBV), human herpes virus type 8 (HHV-8, also known as Kaposi's sarcoma herpes virus, KSHV), human immunodeficiency virus, type-1 (HIV-1), human T cell lymphotropic virus, type-1 (HTLV-1), human papillomavirus (HPV, high-risk types 16, 18, 31, 33, 35, 39,45,51, 52, 56, 58, and 59), Helicobacter pylori, Schistosoma haematobium, Opisthorchis viverrini, and Clonorchis sinensis. The global burden of tumors attributable to viruses and bacterial infections in 2012 was estimated at 15.4% (2.2 million).
The majority of infection-driven cancers have been associated with Helicobacter pylori (770 000 new cases), Human Papillomavirus (640 000 new cases), Hepatitis B virus (420 000 new cases), Hepatitis C virus (170 000 new cases), and Epstein-Barr virus (120 000 new cases). Most of the infection-driven cancers occur in developing countries and areas such as Africa, as well as Central and South America.
Epstein-Barr virus, also known as human herpesvirus 4 (HHV4), is abundantly present in healthy individuals, as it is believed to be present in approximately 90% of the worldwide population. Persistent EBV infections result in the development of several types of human B cell malignancies, including Burkitt's lymphoma (BL) and Hodgkin and non-Hodgkin lymphomas. In addition, EBV has been associated with epithelial cancers, i.e., nasopharyngeal carcinoma (NPC) and a subset of gastric carcinoma.
The high-risk human papillomavirus (HPV) types are responsible for the most common sexually transmitted infections in men and women. The majority of high-risk HPV infections are asymptomatic, transient, and efficiently cleared by the host immune system in 12-24 months. However, some infections may persist causing chromosomal instability and development of premalignant lesions that, if left untreated, have the potential to develop into in invasive cancer in the anogenital area (cervix, vagina, vulva, anus, and penis) as well as in the upper respiratory tract (tonsil and oropharynx). In addition, mucosal low-risk HPV types, such as HPV6 and 11, are able to induce self-limiting benign lesions. These lesions present as anogenital warts, recurrent respiratory papillomatosis in the larynxes, and oral papillomas.
Studies in the last three decades have led to development of several prophylactic vaccines for seven high-risk HPV types (16, 18, 31, 33, 45, 52, and 58) and two low-risk HPV types (6 and 11) that have been used worldwide. The high efficacy of these HPV vaccines and the excellent safety profile are currently providing important health benefits for the population. Active safety monitoring of HPV vaccines is therefore considered a key priority in many countries.
Importantly, most of our current knowledge is on the HPV infection in female anogenital tract, whereas there is only limited understanding on how this infection affects men. In addition, very little is known regarding HPV infection in the head and neck, as well as risk factors associated with cancer development.
Although scientific knowledge in the field of viral oncology has now reached a high level, the role of bacteria as mediators of oncogenesis is less understood. Greater understanding of bacterial-driven carcinogenesis has the potential to provide further novel means of cancer prevention.
The most accepted model of bacteria-mediated carcinogenesis is intimately linked to chronic inflammation induced by an infection. For example. Helicobacter pylori infection has been shown to correlate with gastric cancer. Expanding upon this, when coinfection occurs between both H. pylori and EBV the risk of gastric cancer is increased. Similarly, coinfection of high-risk HPV types with another bacterium, Chlamydia trachomatis, appears to be a risk factor for the development of cervical cancer.
The focus of this special issue will be on new clinical, epidemiological, and functional data on virus- and bacteria-driven carcinogenesis. In addition, it will also review the role of bacteria in influencing cancer development. Finally, it will review the clinical indications known for vaccination against human papillomavirus, highlighting the efficacy of the nonavalent vaccine in preventing cervical, vaginal, and vulvar H-SIL, as suggested by recent systematic literature reviews. This issue will be helpful for basic researchers and clinicians.
Potential topics include but are not limited to the following:
- Correlation between oncogenesis and viral infections
- Correlation between oncogenesis and bacterial infections
- Correlation between viral coinfection and oncogenesis
- The HPV vaccine and it is efficacy at preventing oncogenesis
- Bacteria and virus coinfection in oncogenesis