title: Expression of a non-functional p53 affects the sensitivity of cancer cells to gemcitabine.
abstract: Gemcitabine is a relatively new agent with promising activity in solid tumors. Few data are available regarding mechanisms of resistance to gemcitabine downstream from the drug-target interaction. The present study was performed to gain insight into the role of p53 status on the cytotoxicity of gemcitabine on cancer cells. Drug sensitivity, drug metabolism, cell kinetics and drug-induced apoptosis were compared in 2 lines derived from the mammary adenocarcinoma MCF-7: the wildtype p53 (wt-p53) containing MN-1 cell line and, the MDD2 line containing a dominant negative variant of the p53 protein (mut-p53). The MDD2 cell line was significantly more resistant to gemcitabine cytotoxicity than the MN-1 cell line. The resistant phenotype could not be attributed to a defective gemcitabine activation/degradation pathway or altered levels of expression of intracellular targets. Although both cell lines exhibited p53 accumulation, MN-1 but not MDD2 cells, displayed p21(WAF1) induction after exposure to gemcitabine. Gemcitabine induced an S-phase arrest in both cell lines. A more pronounced block in G1 phase, however, was observed in MN1 cells. Exposure to gemcitabine induced a higher degree of apoptosis in MN-1 than in MDD2 cells. This corresponded with suppression of Bcl-2 and Bcl-X/L expression in wt-p53 cells exposed to gemcitabine whereas Bcl-2 levels remained stable and Bcl-X/L levels increased in mut-p53 cells exposed to gemcitabine. We conclude that the p53 status of cancer cells influences their sensitivity to gemcitabine cytotoxicity. Our evidence suggests that loss of p53 function leads to loss of cell cycle control and alterations in the apoptotic cascade, conferring resistance to gemcitabine in cancer cell lines displaying a mut-p53.
authors.affiliation: INSERM 453, Laboratoire de Cytologie Analytique, Faculté de Médecine Rockefeller, Lyon, France. fgalma@rockefeller.univ-lyon1.fr
authors.forename: Carlos María
authors.initials: CM
authors.lastname: Galmarini
authors.forename: Marilyn L
authors.initials: ML
authors.lastname: Clarke
authors.forename: Nicole
authors.initials: N
authors.lastname: Falette
authors.forename: Alain
authors.initials: A
authors.lastname: Puisieux
authors.forename: John R
authors.initials: JR
authors.lastname: Mackey
authors.forename: Charles
authors.initials: C
authors.lastname: Dumontet
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000473:pathology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis / Q000235:genetics; D004249:DNA Damage; D004261:DNA Replication / Q000187:drug effects; D004273:DNA, Neoplasm / Q000187:drug effects; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D005260:Female; D016193:G1 Phase / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005799:Genes, Dominant; D019254:Genes, bcl-2; D016158:Genes, p53; D006801:Humans; D009363:Neoplasm Proteins / Q000172:deficiency / Q000502:physiology*; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000378:metabolism; D010641:Phenotype; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012334:RNA, Neoplasm / Q000096:biosynthesis / Q000235:genetics; D016196:S Phase / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000502:physiology*; D051020:bcl-X Protein; D000093542:Gemcitabine
chemical_list: D000964:Antimetabolites, Antineoplastic; C494811:BCL2L1 protein, human; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004273:DNA, Neoplasm; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D016159:Tumor Suppressor Protein p53; D051020:bcl-X Protein; D003841:Deoxycytidine; D000093542:Gemcitabine