title: Involvement of p53 in gemcitabine mediated cytotoxicity and radiosensitivity in breast cancer cell lines.
abstract: Gemcitabine (2',2'-difluoro-2'-deoxycytidine; dFdCyd) is one of the anti-metabolites drugs that target DNA replication. We evaluated dFdCyd cytotoxicity and its radiosensitizing ability in human breast cancer cell lines, MCF-7 (wild-type p53) and MDA-MB-231 (mutant-type p53) along with normal mammary epithelial cell line (MCF-12) for comparison. Radiosensitivity and cytotoxicity were measured by the clonogenic survival assays. DNA DSBs was studied by Pulse Field Gel Electrophoresis (PFGE) and cell cycle distribution was analyzed by flow cytometry. MDA-MB-231 cells were the most sensitive to the cytotoxicity of dFdCyd (IC(50) 5 nM) then MCF-7 (IC(50) 10nM), whereas MCF-12 cells were the most resistant to the cytotoxicity of dFdCyd (IC(50) 70 nM). MCF-12 and MCF-7 cell lines did not show any radiosensitization to dFdCyd, whereas the MDA-MB-231 cells showed significantly increased radioresistant to dFdCyd at equimolar concentration (p=0.002) and at IC(50) concentration (p<0.001). The DNA double strand breaks (DSBs) repair showed that dFdCyd neither increases DNA DSBs nor decreases the rate of their repair in MCF-12 and MCF-7 cell lines, while the same treatment in MDA-MB-231 cell line led to decrease the rate of DSBs or increase the rate of DNA repair (p=0.034). Therefore, dFdCyd is a cytotoxic agent, especially in the cancer cells irrespective of having wild-type or mutated p53 protein, but it is not effective as radiosensitizer in the cell lines used in this study. dFdCyd combined with radiation reduces the efficacy of chemo-radiotherapy in p53 mutated cells. Therefore, p53-mutated cancer could be a counter-indication for radiation-gemcitabine combined treatment.
authors.affiliation: Biochemistry and Molecular Biology Department, Faculty of Medicine and Health Sciences, Sana'a University, Sana'a, Yemen. sameersalem@yahoo.com
authors.forename: Sameer D
authors.initials: SD
authors.lastname: Salem
authors.forename: Faisal M
authors.initials: FM
authors.lastname: Abou-Tarboush
authors.forename: Nadeem M
authors.initials: NM
authors.lastname: Saeed
authors.forename: Waheeb D
authors.initials: WD
authors.lastname: Al-Qadasi
authors.forename: M Abul
authors.initials: MA
authors.lastname: Farah
authors.forename: Muneera
authors.initials: M
authors.lastname: Al-Buhairi
authors.forename: Najla
authors.initials: N
authors.lastname: Al-Harbi
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Alhazza
authors.forename: Ghazi
authors.initials: G
authors.lastname: Alsbeih
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor / Q000187:drug effects / Q000528:radiation effects; D002470:Cell Survival / Q000187:drug effects; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016521:Electrophoresis, Gel, Pulsed-Field; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects; D005260:Female; D006801:Humans; D009154:Mutation; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*; D000093542:Gemcitabine
chemical_list: D000964:Antimetabolites, Antineoplastic; D011838:Radiation-Sensitizing Agents; D016159:Tumor Suppressor Protein p53; D003841:Deoxycytidine; D000093542:Gemcitabine