Novel evidence indicates the presence and replication of hepatitis B virus in breast cancer tissue

As a member of the liver tropic virus family, hepatitis B virus (HBV) was thought to only infect and replicate within the liver. Sodium taurocholate co‑transporting polypeptide (NTCP) has been identied as a functional cellular receptor and a major determinant of liver tropism and HBV entry level species specicity. In the present study, the Oncomine database was used to explore differences in NTCP expression among cancerous and normal tissues. The results revealed that NTCP was highly expressed in breast cancer (BC), which was subsequently verified in clinical samples. Furthermore, in the BC tissue of patients with chronic HBV, HBV antigens, viral DNA/RNA and specific viral particles were detected via immunohistochemistry, ELISA, western blotting, reverse transcription‑quantitative PCR and electron microscopy. Different HBV biomarkers and Dane particles were detected in BC. Furthermore, high levels of HBV‑specific RNAs, the characteristic signals of HBV replication, were also detected, indicating that HBV infects BC tissue by binding to NTCP and replicating within. Based on the data of the present study, BC tissue may represent a second location of HBV infection and replication in addition to the liver.