Human papillomavirus type 16/18 up-regulates the expression of interleukin-6 and antiapoptotic Mcl-1 in non-small cell lung cancer

Purpose: Human papillomavirus (HPV) 16/18 infection is reported to be associated with nonsmoking Taiwanese female lung cancer. In this study, we attempted to further reveal the association between HPV infection with Mcl-1 and interleukin (IL)-6 expressions and to elucidate the roles of HPV infection in lung tumorigenesis. Experimental Design: IL-6 and Mcl-1 expressions were investigated in 79 tumor tissues from lung cancer patients by immunohitochemistry. Secreting IL-6 levels and Mcl-1 expressions were examined by ELISA and Western blot, respectively, in HPV 16/18 E6- and E7-transfected A549 human lung cancer cells, as well as in the HPV16-infected TL-1 lung cancer cells established from lung cancer patients. Results: Lung tumors (70.9% and 57.0%) had positive IL-6 and Mcl-1 immunostainings, respectively. Significant correlation between IL-6 and Mcl-1 expression were observed (P < 0.0001). Both IL-6 and Mcl-1 expression were significantly associated with HPV 16/18 infection (P = 0.014 and P = 0.004, respectively). IL-6 and Mcl-1 protein levels were not only elevated in HPV 16/18 E6- and E7-transfected A549 cells but also in TL-1 cells. Phosphaticlylinositol-3-OH kinase pathway was the major pathway contributing to the up-regulation of Mcl-1 by IL-6 in HPV-infected lung cancer cells. Conclusions: The up-regulating effects of HPV 16/18 E6 and E7 to IL-6 and Mcl-1 expressions were observed in E6- and E7-transfected A549 cells and in HPV16-infected TL-1 cells, mainly through the phosphatidylinositol-3-OH kinase pathway. The involvement of HPV infection in lung tumorigenesis may be partly through a concomitant increased expression of autocrine and/or paracrine IL-6 and the downstream Mcl-1.