Carboplatin induces apoptotic cell death through downregulation of constitutively active nuclear factor-kappaB in human HPV-18 E6-positive HEp-2 cells.
Because the role of nuclear factor kappaB (NF-kappaB) is in cellular growth control and neoplasia, we explored the status of NF-kappaB and investigated its role in survival of human HPV-18 E6-positive HEp-2 cells. We observed accumulation of p65 in the nucleus. Moreover, without any external stimulus constitutive NF-kappaB DNA binding and transactivation activity were detected in HEp-2 cells. Treatment with NF-kappaB inhibitor curcumin (diferuloylmethane) and transient transfection of the mutant form of IkappaBalpha, IkappaBalpha super repressor (IkappaBalpha-SR), suppressed constitutive NF-kappaB activity as well as proliferation, suggesting that constitutive NF-kappaB activity is required for the survival of HEp-2 cells. Carboplatin treatment downregulated constitutive NF-kappaB activity and prevented nuclear retention of p65. Further, carboplatin also suppressed the constitutive IkappaBalpha phosphorylation leading to stabilization of IkappaBalpha protein in the cells. Carboplatin inhibited NF-kappaB binding to its response element present in Bcl-2 promoter resulting in downregulation of antiapoptotic Bcl-2 protein. Thus, our results for the first time indicate that constitutive NF-kappaB has a significant role in the survival of HPV-18 E6-positive HEp-2 cells. Moreover, inactivation of NF-kappaB is one of the mechanisms underlying the induction of carboplatin-mediated apoptosis in HPV-18 E6-positive cancer cells.
Singh
Sandeep
S
National Centre for Cell Science, NCCS Complex, Pune University Campus, Ganeshkhind, Pune 411-007, Maharashtra, India.
Bhat
Manoj Kumar
MK
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D016190:Carboplatin / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D003474:Curcumin / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins; D015536:Down-Regulation / Q000187:drug effects; D017930:Genes, Reporter; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009856:Oncogene Proteins, Viral / Q000096:biosynthesis / Q000378:metabolism*; D027383:Papillomaviridae / Q000502:physiology*; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D051996:Transcription Factor RelA; D014162:Transfection
D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; C052603:E6 protein, Human papillomavirus type 18; D020672:I-kappa B Proteins; D016328:NF-kappa B; D009856:Oncogene Proteins, Viral; D019253:Proto-Oncogene Proteins c-bcl-2; D012097:Repressor Proteins; D051996:Transcription Factor RelA; D016190:Carboplatin; D003474:Curcumin