Wild-type p53-function is not required for hyperthermia-enhanced cytotoxicity of cisplatin.
The objective was to test the hypothesis that wild-type p53-function is required for the enhancement of the cytotoxicity of cis-diammine-dichloroplatinum(II) (cDDP) cytotoxicity by hyperthermia (HT). Human colorectal carcinoma cells (RKO) with wild-type p53-function and transfectants with HPV16-E6 or with a dominant negative mutant p53 were used. Cells were treated with HT (60 min at 41 degrees C, 43 degrees C, 45 degrees C: HT41, HT43, HT45). with various doses of cDDP alone or with a combined treatment, simultaneously applied. Survival was determined by clonogenic assays. Levels and localization of p53 were analysed with immunocytochemistry and Western blotting. The extent of HT41-enhanced cytotoxicity of cDDP was similar in all cell lines studied. Immunocytochemistry of wild-type p53 cells showed that p53 is transferred to the nucleus within 5 h after HT43, whilst after HT41 no significant effects were observed. Cell fractionation experiments of wild-type p53 cells showed that, immediately after HT43/HT45, nuclear p53-levels increased as compared to controls, but could not be extracted from the matrix. The extractability was restored 3-5 h after treatment. No significant differences in p53-levels were observed after HT41. These results indicate that, although HT43/HT45 might shortly inactivate p53-function, probably by protein aggregation to the nuclear matrix, the HT-enhanced cDDP-cytotoxicity does not depend on p53-function.
van Bree
C
C
Department of Medical Oncology, Academic Medical Centre, University of Amsterdam, The Netherlands. c.vanbree@amc.uva.nl
Franken
N A
NA
Snel
F A
FA
Haveman
J
J
Bakker
P J
PJ
D000970:Antineoplastic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D016923:Cell Death; D002470:Cell Survival / Q000187:drug effects*; D002945:Cisplatin / Q000494:pharmacology*; D015179:Colorectal Neoplasms / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
D000970:Antineoplastic Agents; D016159:Tumor Suppressor Protein p53; D002945:Cisplatin