HPV16 E6/E7 upregulates HIF-2α and VEGF by inhibiting LKB1 in lung cancer cells.

Long-term persistent infection of HPV16 E6/E7 is frequently associated with lung cancers, especially in non-smokers and in Asians. However, molecular mechanisms of HPV16 E6/E7 induction of lung cancer are not fully understood. Using bi-directional genetic manipulation and four well-established lung cancer cell lines, we showed HPV16 E6/E7 downregulated expression of liver kinase B1 at both protein and messenger RNA levels; liver kinase B1 downregulated hypoxia-inducible factor 2α at protein level but not at messenger RNA level, and hypoxia-inducible factor 2α upregulated vascular endothelial growth factor at both protein and messenger RNA levels. This is the first study to show hypoxia-inducible factor 2α as a downstream effector of liver kinase B1 in lung cancer cells. Our results indicate that HPV16 E6/E7 indirectly upregulated the expression of vascular endothelial growth factor by inhibition of liver kinase B1 expression and upregulation of hypoxia-inducible factor 2α expression, thus propose a human papillomavirus-liver kinase B1-hypoxia-inducible factor 2α-vascular endothelial growth factor axis for the tumorigenesis of lung cancer. Our study also provides new evidence to support the critical role of liver kinase B1 in the pathogenesis of human papillomavirus-related lung cancer and suggests novel therapeutic targets.