Expression of Human Endogenous Retroviruses (HERVs) in Breast Cancer: A Transcriptomic Study

Background: Human endogenous retroviruses (HERVs) are ancient viral elements integrated into the human genome. HERVs, especially HERV-K (HML-2), play a significant role in the onset and advancement of breast cancer. This study examined the expression of endogenous retroviruses in human breast tissues to reveal potential associations between retroviruses and breast cancer.

Materials and methods: RNA-Seq datasets from breast cancer tissues (ductal carcinoma and triple-negative subtypes) and normal breast tissues were retrieved from the NCBI Sequence Read Archive (SRA). Bio-informatics analysis included read mapping against the human genome (hg19) and a custom pseudogenome containing HERVsequences. Normalized expression of HERV-human junctions was calculated, and statistical comparisons were performed using independent samples t-tests and Mann-Whitney tests

Results: Breast cancer tissues exhibited significantly higher normalized coverage of HERV integration sites compared to healthy controls (p = 0.009). Among breast cancer cases, patients who had undergone treatment showed significantly lower HERV expression than untreated patients (p = 0.023). Visualization via IGV confirmed increased read accumulation at HERV loci in cancer samples.

Conclusion: HERVs were overexpressed in breast cancer cell lines compared to healthy breast tissue samples, with expression levels influenced by therapeutic interventions. These findings support the potential role of HERVs as biomarkers for breast cancer diagnosis, prognosis, and therapeutic monitoring.