Evidence of an association between human papillomavirus and impaired chemotherapy-induced apoptosis in cervical cancer cells.
OBJECTIVE
The aim of this study was to determine cervical cancer cell sensitivity to chemotherapy-induced apoptosis based on human papillomavirus (HPV) status.


METHODS
CaSki (HPV-positive) and C33A (HPV-negative) cells were treated with camptothecin or cisplatin. Cellular viability was determined by trypan blue exclusion. Apoptotic indexes were determined by flow cytometric analysis of annexin V labeling and morphological changes. Mitochondrial release of cytochrome c was determined by immunofluorescence using confocal microscopy. Caspase 3 activation and bax expression were assessed by immunoblotting.


RESULTS
CaSki cells displayed chemoresistance to both camptothecin and cisplatin. Low response to apoptogenic stimuli was evidenced by a marginal increase in the apoptotic cell fraction after camptothecin treatment (22.9 +/- 2.56%) compared with control (17.8 +/- 1.95%). Cisplatin (14.8 +/- 1.01%) caused a slight decrease in apoptosis. Mitochondrial release of cytochrome c and cleavage of caspase 3 could not be demonstrated in CaSki cells after treatment. Despite p53 mutation, C33A cells were sensitive to the antiproliferative effects of camptothecin and cisplatin. Mean apoptotic events were 17.5 +/- 0.33 for control, 42 +/- 1.76 for cisplatin, and 38.1 +/- 0.75 for camptothecin. An intact cytochrome c pathway was demonstrated in C33A cells leading to cleavage of caspase 3 after camptothecin treatment. The constitutive bax expression demonstrated in both cell lines displayed no change after camptothecin treatment.


CONCLUSIONS
HPV-positive cervical cancer cells have an inherent resistance to chemotherapy-induced apoptosis. HPV-dependant inactivation of apoptotic regulators such as p53 and blockage of downstream events such as cytochrome c release and caspase 3 activation might be elemental to this cellular survival advantage provided by high-risk oncogenic papillomavirus.
Padilla
Luis A
LA
Division of Gynecologic Oncology, University of Minnesota, Minneapolis, Minnesota 55455, USA. lupadilla@salud.unm.edu
Leung
Benjamin S
BS
Carson
Linda F
LF
D017304:Annexin A5; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002166:Camptothecin / Q000494:pharmacology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology*; D003574:Cytochrome c Group / Q000378:metabolism; D004789:Enzyme Activation; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D027383:Papillomaviridae; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis; D019253:Proto-Oncogene Proteins c-bcl-2; D014407:Tumor Cells, Cultured; D002583:Uterine Cervical Neoplasms / Q000188:drug therapy* / Q000473:pathology / Q000821:virology*; D051028:bcl-2-Associated X Protein
D017304:Annexin A5; D000970:Antineoplastic Agents; C494826:BAX protein, human; D003574:Cytochrome c Group; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D002945:Cisplatin; D002166:Camptothecin