Reduction of 9-nitrocamptothecin-triggered apoptosis in DU-145 human prostate cancer cells by ectopic expression of 14-3-3zeta.
A promising family of anticancer agents, the camptothecins, is noted for their ability to induce apoptosis specifically in malignant cells. However, a major obstacle for successful cancer treatment by these and other chemotherapeutic agents is the intrinsic or acquired resistance to drug treatment. Resistance to 9NC6, a camptothecin derivative, has been modeled in vitro using a human prostate cancer cell line. To elucidate the mechanism for acquired 9NC resistance, we have used a subtractive cloning approach to identify genes whose altered expression level is reflective of 9NC resistance or susceptibility. Differential gene expression was compared between wild-type human prostate cancer cell line, DU-145, and a 9NC-resistant subline, RC1. Results were confirmed by Northern and Western blot analyses. In this report, we focus on one gene, 14-3-3zeta. An expression vector of a full-length myc-epitope-tagged 14-3-3zeta cDNA was constructed and used for transfection into DU-145 cells. We consistently observed that 14-3-3zeta message and protein levels were dramatically increased in 9NC resistant cells. The expression levels of other 14-3-3 family members were unaffected. Strikingly, ectopic overexpression of 14-3-3zeta in wild-type 9NC-susceptible prostate cancer cells decreased 9NC-induced apoptosis. Our results suggest a novel direct or indirect role of 14-3-3zeta in mediating resistance of DU-145 cells to the topoisomerase I inhibitor, 9NC. We are currently exploring whether this represents a more general pathway for drug resistance as well.
Chatterjee
Devasis
D
Divison of Medicine, Rhode Island Hospital and Brown University, Providence, RI 02912, USA.
Goldman
Melissa
M
Braastad
Corey D
CD
Darnowski
James
J
Wyche
James H
JH
Pantazis
Panayotis
P
Goodglick
Lee
L
D048948:14-3-3 Proteins / Q000235:genetics / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D003001:Cloning, Molecular; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D015870:Gene Expression; D006801:Humans; D008297:Male; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D048948:14-3-3 Proteins; D000970:Antineoplastic Agents; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C079905:rubitecan; D002166:Camptothecin