Drg1, a novel target for modulating sensitivity to CPT-11 in colon cancer cells.
Treatment of the human colon cancer cells Hct116 with SN-38 (an active metabolite of CPT-11) resulted in G2 cell cycle arrest without induction of apoptosis. However, subsequent treatment of SN-38-treated Hct116 cells with flavopiridol induced apoptosis. One of the genes markedly up-regulated during cell cycle arrest by SN-38 and suppressed during apoptosis by SN-38 followed by flavopiridol in Hct116 cells is Drg1. We found that Drg1 had profound effects on SN-38 sensitivity. Inhibition of endogenous Drg1 expression in Hct116 cells by stable expression of an antisense (AS) Drg1 cDNA increased the sensitivity of cells to undergo apoptosis by SN-38. Clonogenic and apoptosis assays with AS Drg1-expressing cells showed a 2-fold decrease in the IC50 and a 4-5-fold increase in induction of apoptosis with SN-38. Conversely, the forced expression of Drg1 in SW620 cells increased the resistance of these cells to SN-38-induced apoptosis by 2-5-fold. Moreover, when xenografted in mice, AS Drg1-expressing Hct116 cells were 3-fold more sensitive to CPT-11 as compared with vector transfected Hct116 cells. Similarly, tumors established from Drg1 overexpressing SW620 cells were more resistant to CPT-11 as compared with tumors established from vector-transfected SW620 cells in mice. Taken together, our data suggest that Drg1 is a novel gene that plays a direct role in resistance to CPT-11. Inhibition of Drg1 may provide a new means to increase the sensitivity of colon cancer cells to CPT-11.
Gastrointestinal Oncology Research Laboratory, Division of Solid Tumor Oncology, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, New York 10021, USA.
Monica
M
Motwani
Francis M
FM
Sirotnak
Yuhong
Y
She
Therese
T
Commes
Gary K
GK
Schwartz
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002166:Camptothecin / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000493:pharmacokinetics / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D016373:DNA, Antisense / Q000235:genetics / Q000494:pharmacology; D018076:DNA, Complementary / Q000235:genetics; D004357:Drug Synergism; D005419:Flavonoids / Q000008:administration & dosage / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D000077146:Irinotecan; D008297:Male; D051379:Mice; D008819:Mice, Nude; D010880:Piperidines / Q000008:administration & dosage / Q000494:pharmacology; D011355:Prodrugs / Q000493:pharmacokinetics / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
D016373:DNA, Antisense; D018076:DNA, Complementary; D005419:Flavonoids; D010880:Piperidines; D011355:Prodrugs; C078418:developmentally regulated GTP-binding protein; C077990:alvocidib; D000077146:Irinotecan; D019204:GTP-Binding Proteins; D002166:Camptothecin