Cancer: Breast, colon
Action: Cytostatic
Breast Cancer
Recently, natural product DNA topoisomerase I inhibitors 10-hydroxycamptothecin (HCPT) and camptothecin (CPT) have been shown to have therapeutic effects in both in vitro and in vivo models of human breast cancer. After evaluation, the apoptotic pathways were characterized in vitro and in vivo in the human breast cancer cell lines MCF-7 and MDA-MB-468.
The elevation of p53 protein levels in MCF-7 cells treated with CPT was significantly inhibited by preincubation with DNA breaks inhibitor aphidicolin, while the elevation of p21WAF1/CIP1 protein levels was not inhibited. The elevation of p21WAF1/CIP1 in MDA-MB-468 cells treated with CPT was not inhibited by aphidicolin. Using Northern blot analysis, the transcription of p21WAF1/CIP1 was shown to increase in a dose-dependent manner in MCF-7 and MDA-MB-468 cells treated with HCPT or CPT.
Results suggest that treatment with HCPT and CPT results in increased levels of p21WAF1/CIP1 protein and mRNA, and that they induce apoptosis in human breast cancer cells through both p53-dependent and -independent pathways. Findings may be significant in further understanding the mechanisms of actions of camptothecins in the treatment of human cancers (Liu & Zhang, 1998).
Colon Cancer
10-Hydroxycamptothecin (10-HCPT), an indole alkaloid isolated from a Chinese tree, Camptotheca acuminate , inhibits the activity of topoisomerase I and has a broad spectrum of anti-cancer activity in vitro and in vivo. 10-HCPT significantly repressed the proliferation of Colo 205 cells at a relatively low concentration (5-20 nM). Flow cytometry analysis and Western blot and apoptosis assays demonstrated that low-dose 10-HCPT arrested Colo 205 cells in the G2 phase of the cell-cycle and triggered apoptosis through a caspase-3-dependent pathway. No acute toxicity was observed after an oral challenge of 10-HCPT in BALB/c-nude mice every 2 days.
Results suggest that a relatively low dose of 10-HCPT (p.o.) is able to inhibit the growth of colon cancer, facilitating the development of a new protocol of human trials with this anti-cancer drug (Ping et al., 2006).
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