title: Silencing of endo-exonuclease expression sensitizes mouse B16F10 melanoma cells to DNA damaging agents.
abstract: We previously identified an endo-exonuclease that is highly expressed in cancer cells and plays an important role in DSB repair mechanisms. A small molecular compound pentamidine, which specifically inhibited nuclease activity of the isolated endo-exonuclease from yeast as well as from mammalian cells, was capable of sensitizing tumor cells to DNA damaging agents. In this study, we investigated the effect of precisely silencing the endo-exonuclease expression by small interfering RNA (siRNA) upon treatment with a variety of DNA damaging agents in mouse B16F10 melanoma cells. A maximum of 3.6 to approximately 4-fold reduction in endo-exonuclease mRNA expression was achieved, over a period of 48-72 h of post transfection with a concomitant reduction in protein expression (approximately 4-5 fold), resulting in a substantial reduction (approximately 45-50%) of the corresponding nuclease activity. Suppressed endo-exonuclease expression conferred significant decrease in cell survival, ranging from approximately 30 to approximately 50% cell killing, in presence of DNA damaging drugs methyl methane sulfonate (MMS), cisplatin, 5-fluoro uracil (5-FU) and gamma-irradiation but not at varying dosages of ultra violet (UV) radiation. The data strongly support a role for the endo-exonuclease in repairing DNA damages, induced by MMS, cisplatin, 5-FU and gamma irradiation but not by UV radiation. The results presented in this study suggest that the endo-exonuclease siRNA could be useful as a therapeutic tool in targeting the endo-exonuclease in cancer therapy.
authors.affiliation: Department of Oncology, Faculty of Medicine, McGill University, 845 Sherbrooke St., Montreal, QC, H3A 2T5, Canada.
authors.forename: Sibgat A
authors.initials: SA
authors.lastname: Choudhury
authors.forename: Paul
authors.initials: P
authors.lastname: Kauler
authors.forename: Slobodan
authors.initials: S
authors.lastname: Devic
authors.forename: Terry Y-K
authors.initials: TY
authors.lastname: Chow
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D004249:DNA Damage; D004720:Endonucleases / Q000235:genetics*; D005092:Exonucleases / Q000235:genetics*; D005472:Fluorouracil / Q000494:pharmacology; D005720:Gamma Rays; D020868:Gene Silencing; D008546:Melanoma, Experimental / Q000188:drug therapy / Q000532:radiotherapy; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D051379:Mice; D009153:Mutagens / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D014466:Ultraviolet Rays
chemical_list: D000970:Antineoplastic Agents; D009153:Mutagens; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D008741:Methyl Methanesulfonate; D004720:Endonucleases; D005092:Exonucleases; C020104:endoexonuclease; D002945:Cisplatin; D005472:Fluorouracil