HPV18 E6/E7 activates Ca2+ influx to promote the malignant progression of cervical cancer by inhibiting Ca2+ binding protein 1 expression.

Abstract

Mounting studies have shown that the oncoproteins E6 and E7 encoded by the human papillomavirus (HPV) genome are essential in HPV-induced cervical cancer (CC). Ca2+ binding protein 1 (CABP1), a downstream target of HPV18-positive HeLa cells that interferes with E6/E7 expression, was identified through screening the GEO Database (GSE6926). It was confirmed to be down-regulated in CC through TCGA prediction and in vitro detection. Subsequent in vitro experiments revealed that knocking down E6/E7 inhibited cell proliferation, migration, and invasion, whereas knocking down CABP1 promoted these processes. Simultaneously knocking down CABP1 reversed these effects. Additionally, the results were validated in vivo. Previous studies have indicated that CABP1 can regulate Ca2+ channels, influencing Ca2+ influx and tumor progression. In this study, it was observed that knocking down CABP1 enhanced Ca2+ inflow, as demonstrated by flow cytometry and confocal microscopy. Knocking down E6/E7 inhibited these processes, whereas simultaneously knocking down E6/E7 and CABP1 restored the inhibitory effect of knocking down E6/E7 on Ca2+ inflow. To further elucidate that E6/E7 promotes CC progression by inhibiting CABP1 expression and activating Ca2+ influx, BAPTA/AM treatment was administered during CABP1 knockdown. It was discovered that Ca2+ chelation could reverse the effect of CABP1 knockdown on CC cells. In conclusion, our results offer a novel target for the diagnosis and treatment of HPV-induced CC.