Increased expression of 70 kD heat shock protein in cultured primary human keratinocytes induced by human papillomavirus 16 E6/E7 gene.

Background: Heat shock protein 70 (HSP70) is expressed highly in epithelial tumours associated closely with human papillomavirus 16 (HPV16) infections. However, evidence about the direct relationship between HSP70 expression and HPVs infections are still lacking. In the present study, we examined the expression of HSP70 in keratinocytes introduced with HPV16 E6/E7 oncogenes.
Methods: Stable transfected cells were established by transfection of the plasmids pLXSN16E6/E7 into cultured primary keratinocytes and subsequently selected by plasmid specific selection antibiotic (G418) at the required concentration. The expression of HSP70 in pLXSN16E6/E7 transfected keratinocytes was determined by Western blot. The correlation of HSP70 expression and E6/E7 transfection was further confirmed by doubly labelled immunofluorescent staining.
Results: Compared to non-transfected keratinocytes, there was a significant trend for higher levels of HSP70 in pLXSN16E6/E7 transfected keratinocytes. Doubly labelled immunofluorescent staining experiment showed that the co-localization of HPV16 E6/E7 and HSP70 in transfected keratinocytes was observed and increased expression of HSP70 was strongly associated with the transfection of HPV16 E6/E7.
Conclusions: Our studies demonstrated increased levels of HSP70 proteins in keratinocytes stably transfected by HPV16 E6/E7 oncogenes. It suggests that the expression of HSP70 is modulated by HPV16 E6/E7 proteins, which may be involved in HPV16 E6/E7 induced immortalization.