Breast cancer is one of the most common cancers in women[1], with more than 2.1 million people diagnosed with breast cancer annually[2]. Breast Cancer is the second most common cancer in women in the United States, with 268,600 new cases in the year. After lung cancer, breast cancer is the second deadliest cancer in the world and is responsible for 627,000 and 41760 deaths in the world and the United States respectively[2]. About 15% of women's cancer deaths are due to Breast cancer[1]. Until 2015, the incidence of breast cancer had an upward trend, but today the incidence of breast cancer has a steady trend[1]. However, the exact cause of breast cancer is unknown, and several factors such as lifestyle, smoking, obesity, aging, and infectious agents are considered as risk factors for breast cancer[2, 3]. According to the International Cancer Agency, infectious agents such as viruses are responsible for 15–20% of human cancers[4]. Previous studies have shown that papillomavirus[5], Epstein-Barr virus (EBV)[2], mouse mammary tumor virus (MMTV)[6, 7], and bovine leukemia virus (BLV)[8] are associated with an increased risk of breast cancer. Moreover, several recent studies have suggested a possible relationship between Human Herpes Virus-8 (HHV-8) and breast cancer[9, 10].
The HHV-8 is the eighth human virus of the Herpesviridae and is also known as Kaposi's Sarcoma-associated Herpes Virus (KSHV)[11]. The HHV-8 virus causes Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman’s disease[12, 13]. Kaposi's sarcoma is more common among immunocompromised individuals such as AIDS patients[14]. Studies have shown that this virus is tumorigenic and is closely related to fibro adenoma tumors[9, 15]. However, the virus is not associated with cervical and oral tumors[16, 17]. A study by PAUL et al. Showed that the HHV-8 virus has the potential to invade and persist in the brain tissue[18]. Several studies have also shown that the HHV-8 virus has been detected in breast cancer patients. The study by Tsai showed that the prevalence of HHV-8 in breast cancer patients is higher than other viruses[9]. Also, the Amira S. Mohamed study showed, 28.8% blood samples of breast cancer cases were positive for HHV-8 DNA[10].
The HHV-8 virus has the ability to produce cytokine homologs such as interleukin-6 (IL-6). Studies have shown that an increase in IL-6 is associated with metastasis and the progression of breast cancer [19–21]. Increased IL-6 expression activates the virus lytic cycle and increases the expression of genes involved in pathogenesis, leading to the development of malignancy[22]. The ability to infect and proliferate in epithelial cells, the ability to produce interleukin homologs, and the detection of the hhv-8 virus genome in breast cancer tissue are factors that suggest that the hhv-8 virus may be associated with breast cancer[23].
We aimed to investigate the presence of HHV-8 genome in breast tissues in women with breast cancer.