Human papilloma virus 16 E6 RNA interference enhances cisplatin and death receptor-mediated apoptosis in human cervical carcinoma cells.
In cervical cancer, the p53 and retinoblastoma (pRb) tumor suppressor pathways are disrupted by the human papilloma virus (HPV) E6 and E7 oncoproteins, because E6 targets p53 and E7 targets pRb for rapid proteasome-mediated degradation. We have investigated whether E6 suppression with small interfering RNA (siRNA) restores p53 functionality and sensitizes the HPV16-positive cervical cancer cell line SiHa to apoptosis by cisplatin, irradiation, recombinant human tumor necrosis factor-related apoptosis-inducing ligand (rhTRAIL), or agonistic anti-Fas antibody. E6 siRNA resulted in decreased E6 mRNA levels and enhanced p53 and p21 expression, demonstrating the restoration of p53 functionality in SiHa cells, without inducing high levels of apoptosis (<10%). Cell surface expression of the proapoptotic death receptors (DRs) DR4, DR5, and Fas was not affected by E6 suppression. E6 suppression conferred susceptibility to cisplatin-induced apoptosis but not to irradiation-, rhTRAIL-, or anti-Fas antibody-induced apoptosis. Combining cisplatin with rhTRAIL or anti-Fas antibody induced even higher apoptosis levels in E6-suppressed cells. At the molecular level, cisplatin treatment resulted in elevated p53 levels, enhanced caspase-3 activation, and reduced p21 levels in E6-suppressed cells. Cisplatin in combination with death receptor ligands enhanced caspase-8 and caspase-3 activation and reduced X-linked inhibitor-of-apoptosis protein (XIAP) levels in these cells. We showed using siRNA that the enhanced apoptosis in E6-supressed cells was related to reduced XIAP levels and not due to reduced p21 levels. In conclusion, targeting E6 or XIAP in combination with cisplatin can efficiently potentiate rhTRAIL-induced apoptosis in HPV-positive cervical cancer cells.
Department of Medical Oncology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
Shinta
S
Tan
Brigitte M T
BM
Hougardy
Gert J
GJ
Meersma
Bessel
B
Schaap
Elisabeth G E
EG
de Vries
Ate G J
AG
van der Zee
Steven
S
de Jong
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D002945:Cisplatin / Q000494:pharmacology*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000502:physiology; D005260:Female; D006367:HeLa Cells; D006801:Humans; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000502:physiology*; D034622:RNA Interference; D053218:Receptors, Death Domain / Q000502:physiology*; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000032:analysis; D002583:Uterine Cervical Neoplasms / Q000188:drug therapy* / Q000473:pathology; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000502:physiology
D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C068651:E6 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D053218:Receptors, Death Domain; D012097:Repressor Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; D016159:Tumor Suppressor Protein p53; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D053148:Caspase 3; D053181:Caspase 8; D002945:Cisplatin