title: Re-expression of HPV16 E2 in SiHa (human cervical cancer) cells potentiates NF-κB activation induced by TNF-α concurrently increasing senescence and survival.
abstract: Re-expression of E2 in human papillomavirus (HPV) transformed tumour cells can induce apoptosis; however, some evidences also attribute an important role to E2 in sustaining tumorigenesis. In the present paper, we studied the effects of tumour necrosis factor (TNF)-α-mediated NF-κB (nuclear factor kappa-light-chain-enhancer of activated B-cells) activation on E2-induced senescence in HPV16-integrated SiHa cells. The results show that E2 inhibits endogenous E6 gene expression and sensitizes SiHa cells to TNF-α-induced NF-κB activation. Under this condition there was an increase in the expression of senescent proteins p53, p21, p27 and p16 and senescence-associated (SA)-β-galactosidase activity indicating that TNF-α augments E2-mediated senescence. Re-expression of E2 expression with TNF-α treatment resulted in an increase in the expression of anti-apoptotic Bcl2 (B-cell lymphoma 2) protein and other pro-survival genes like cyclin D1 (cyc D1), survivin and hTERT (human telomerase reverse transcriptase). Concomitantly, E2 + TNF-α combination increased the survival of SiHa cells by positive changes in viability, proliferation and colony formation. E2-induced apoptotic tendency shifted towards senescence in presence of TNF-α by arresting the cells at both G0/G1 and G2/M phases, thus enhancing cell survival. Another observation in the present study is the significant up-regulation of key senescence messaging factors regulated by NF-κB namely interleukin (IL)-6, IL-8, high-mobility group protein A (HMGA)1 and B (HMGB)1 in E2-transfected cells treated with TNF-α. Our data provide a mechanistic basis and a new insight for the role of TNF-α and E2 in linking cellular senescence, tumorigenesis and HPV re-infection.
authors.affiliation: *Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600 036, India.
authors.forename: Devan
authors.initials: D
authors.lastname: Prabhavathy
authors.affiliation: *Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600 036, India.
authors.forename: Chandrasekaran Karthik
authors.initials: CK
authors.lastname: Subramanian
authors.affiliation: *Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai 600 036, India.
authors.forename: Devarajan
authors.initials: D
authors.lastname: Karunagaran
mesh_terms: D045744:Cell Line, Tumor; D002470:Cell Survival; D016922:Cellular Senescence; D002584:Cervix Uteri / Q000276:immunology / Q000821:virology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000276:immunology*; D005260:Female; D015870:Gene Expression; D052162:Human papillomavirus 16 / Q000235:genetics / Q000276:immunology*; D006801:Humans; D016328:NF-kappa B / Q000276:immunology*; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000276:immunology*; D030361:Papillomavirus Infections / Q000150:complications* / Q000276:immunology / Q000821:virology; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology*; D002583:Uterine Cervical Neoplasms / Q000150:complications / Q000276:immunology / Q000821:virology*
chemical_list: D004268:DNA-Binding Proteins; C054855:E2 protein, Human papillomavirus type 16; D016328:NF-kappa B; D009856:Oncogene Proteins, Viral; D014409:Tumor Necrosis Factor-alpha