Oncogenic Viruses–Chapter 20: The involvement of human papillomavirus in breast cancer in general and the different prognostic biomarkers in triple-negative breast cancer

Because breast cancer is a multifactorial disease, the role of infectious agents in the development of the disease is of great interest. The high incidence of breast cancer around the world has led to interest in a possible viral etiology of breast cancer. There is increasing evidence that high-risk human papillomavirus is involved in cancers besides cervical cancer. Infectious agents are thought to be responsible for approximately 16% of cancers worldwide. However, there are mixed reports in the literature regarding the prevalence and potential pathogenicity of viruses in breast cancer. Triple-negative breast cancer (TNBC) is defined as a type of breast cancer with lack of expression of estrogen receptor, progesterone receptor, and HER2 protein. The tumorigenesis is not likely to be driven by a hormonal or HER2 pathway. Chemotherapy is still the main therapeutic approach for this subgroup of patients; therefore progress in the treatment of TNBC remains an important challenge. Data derived from molecular technologies have identified TNBCs with different gene expression and mutation profiles that may help in developing targeted therapies. So far, however, only a few of these have been shown to improve the prognosis and outcomes of patients with TNBC. This chapter has two parts. The first part focuses on the involvement of human papillomavirus (HPV) in breast cancer in general; the second part discusses prognostic biomarkers in TNBC.