Cisplatin restores p53 function and enhances the radiosensitivity in HPV16 E6 containing SiHa cells.
Most HPV-positive cervical cancer cells possess wild type p53 gene, but its normal p53 functions are disrupted by expression of HPVs E6. Treatment with 0-20 microM cisplatin for 24 h in HPV16 E6 containing SiHa cells suppressed E6 mRNA, reduced E6 protein, and restored p53 expression in dose-dependent manners. Dual-parameter flow cytometric analysis indicated that sub-G(1) apoptotic cells, but not necrotic cells were the major species for cisplatin-induced cytotoxicity in SiHa cells. After 0-10 microM cisplatin treatment, slightly more apoptotic cells appeared from SiHa cells than those from dominant negative p53-transfected SiHa cells. There was no different ionizing radiation (IR)-induced apoptosis in these two different cells. On the other hand, cisplatin enhanced more IR-induced sub-G(1) apoptosis in SiHa than mp53-SiHa cells. These accompanied with prolonged p53 restoration in irradiated-SiHa cells after 24 h cisplatin treatment and thereafter. In contrast, it was not found in cells after irradiation alone. Similar results were also shown in Mdm2 expression in SiHa cells after combined treatment. Therefore, cisplatin restored p53 expression and prolonged IR-induced p53 restoration would be possible candidates to response more sub-G(1) apoptosis in irradiated SiHa cells. These results provided another new explanation on cisplatin sensitizing radiotherapy for HPV16 E6 containing cancer cells.
Huang
Haimei
H
Department of Life Science, National Tsing-Hua University, Taiwan, ROC. hmhuang@life.nthu.edu.tw
Huang
Shian-Yi
SY
Chen
Ting-Ting
TT
Chen
Ja-Chi
JC
Chiou
Chian-Ling
CL
Huang
Ter-Mei
TM
D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000633:toxicity; D017209:Apoptosis / Q000528:radiation effects; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology* / Q000633:toxicity; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011836:Radiation Tolerance / Q000187:drug effects*; D011839:Radiation, Ionizing; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D002583:Uterine Cervical Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology* / Q000532:radiotherapy
D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; C068651:E6 protein, Human papillomavirus type 16; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D002945:Cisplatin