The Oncogenic Roles of JC Virus T Antigen in Breast Carcinogenesis.

JC virus (JCV) infects 80-90% of the population and results in progressive multifocal leukoencephalopathy upon immunodeficiency. The study aimed to pathologically clarify the oncogenic roles of T antigen in human breast cancers. Breast cancer, dysplasia, and normal tissues were examined for of JCV by nested and real-time PCR. The positive rate or copy number of T antigen was compared with clinicopathological parameters of breast cancer. JCV existence was morphologically detected by immunohistochemistry and PCR. T antigen was examined by Western blot using frozen samples of breast cancer and paired normal tissues. According to nested PCR, the positive rate of breast ductal or lobular carcinoma was lower than that of normal tissue ( < 0.05). T antigen existence was negatively correlated with E-cadherin expression and triple-negative breast cancer ( < 0.05), but positively correlated with lymph node metastasis and estrogen receptor and progestogen receptor expression ( < 0.05). Quantitative PCR showed that JCV copies were gradually decreased from normal, dysplasia to cancer tissues ( < 0.05). JCV T antigen copy number was lower in ductal adenocarcinoma than in normal tissue ( < 0.05), in line with in situ PCR and immunohistochemistry. JCV copies were negatively correlated with tumor size and E-cadherin expression ( < 0.05), but positively correlated with G grading of breast cancer ( < 0.05). Western blot also indicated weaker T antigen expression in breast cancer than normal tissues ( < 0.05). JCV T antigen might play an important role in breast carcinogenesis. It can be employed as a molecular marker for the differentiation and aggressive behaviors of breast cancer.