HPV16 E6 oncoprotein increases cell adhesion in human keratinocytes

Expression of the E6 oncoprotein of human papillomavirus (HPV) 16 in primary human keratinocytes (PHKs) was previously shown to significantly reduce apoptosis. This could be due to increased cell adhesion. Adhesion ability was tested by seeding cells on tissue culture dishes coated with different concentrations of poly(HEME) and determination of the proportion of attached cells. Assays were carried out with PHKs, immortalized human keratinocytes (HaCaT) and human 293T cells. The E6 gene was transduced via retroviral infection or DNA transfection. Results of these assays showed that expression of E6 increased the proportion of cells that attached to poly(HEME). Several HPV16 E6 mutants were also tested in the above assay in 293T cells. These assays showed that the p53 targeting region of E6 is dispensable for this activity. Assays of inhibition of tyrosine kinases by bombesin showed that E6 probably utilizes other pathways to increase cell adhesion.