The major bioactive polyphenol in green tea, EGCG, could potentially reverse the abnormal changes induced by oncogenic HPV strains.
This research involved organotypic raft cultures of keratinocytes infected with HPV18. The culture was established at an air-liquid interface for 10 days and then treated with EGCG for an additional 10 days. The treated raft sections were stained using antibodies specifically targeting cell proliferation, keratinocyte differentiation markers, and tumor suppressor genes. Further, western blotting was utilized on EGCG-treated cells to determine the levels of HPV18 E6 and E7 protein expression.
It was observed that the EGCG treatment blocked the ability of HPV18-positive keratinocytes to produce hyperplastic epithelium within the raft culture. EGCG allowed for a decline in cell proliferation as confirmed by bromodeoxyuridine label incorporation and Ki67 staining, and it led to the upregulated expression of various tumor suppressor genes. Meanwhile, productive viral replication was impaired. Importantly, the treatment did not significantly impact keratinocyte differentiation. Rather, EGCG treatment in the culture encouraged the degradation of E6 and E7 proteins and reinstated the tumor suppressor gene expression.
