NSC606985, a novel camptothecin analog, induces apoptosis and growth arrest in prostate tumor cells.
OBJECTIVE
Prostate cancer is a major cause of cancer mortality in American males. Once prostate cancer has metastasized, there is currently no curative therapy available. The development of effective agents is therefore a continuing effort to combat this disease. In the present study, the effects and potential mechanisms of NSC606985 (NSC), a water-soluble camptothecin analog, in prostate cancer cells were investigated.


METHODS
Prostatic tumor cells, DU-145, LNCaP and PC-3, were used for the study. Cell proliferation, cell cycle, cell apoptosis and caspase 3/7 activity were determined in the presence or absence of NSC. The levels of Bax and Bak, and the release of cytochrome c from mitochondria were analyzed by Western blot.


RESULTS
Treatment with NSC at nanomolar concentrations produced a time- and dose-dependent decrease in viable cell numbers of multiple prostate cancer cells. In DU-145 cells, NSC produced a time-and dose-dependent induction of cell apoptosis and cell cycle arrest as evidenced by cell morphological changes, increases in S-phase and sub-G1 cell fractions, an elevation of caspase 3/7 activity, DNA fragmentation and apoptotic cells. NSC increased the levels of apoptotic proteins, Bax and Bak, and induced a release of cytochrome c from mitochondria to cytosol in DU-145 cells. Co-administration of Z-VAD-FMK, a pan-caspase inhibitor, blocked NSC-induced caspase 3/7 activity and cell apoptosis without affecting NSC-induced cell cycle arrest. In contrast, co-administration of a PKCdelta inhibitor, rottlerin, had no significant effect on NSC induction of caspase activity, and slightly potentiated NSC-induced cell death. Furthermore, like camptothecin, a mutation of topoisomerase 1 that prevents the binding of camptothecin to the enzyme completely abolished the NSC effect in DU-145 cells.


CONCLUSIONS
The data obtained suggest that NSC is able to decrease cell growth, induce cell apoptosis and cause growth arrest in prostatic tumor cells, which may involve an interaction with topoisomerase 1 and an activation of mitochondrial apoptotic pathway.
Tan
Chen
C
Department of Medicine/Endocrinology, Weill Medical College of Cornell University, 1300 York Avenue, Box-149, Room F-233, New York, NY 10021, USA.
Cai
Li-Qun
LQ
Wu
Wendy
W
Qiao
Yaming
Y
Imperato-McGinley
Julianne
J
Chen
Guo-Qiang
GQ
Zhu
Yuan-Shan
YS
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000473:pathology*
D000970:Antineoplastic Agents; C514334:NSC606985; D045304:Cytochromes c; D053148:Caspase 3; D053179:Caspase 7; D002166:Camptothecin