Gastrointestinal cancers pose major public health problems worldwide, in part because little progress has been made in the treatment of
colorectal cancers. The present study explored the potential use of
natural product topoisomerase I inhibitors,
10-hydroxycamptothecin (
HCPT) and
camptothecin (
CPT), in the treatment of human
colon cancers.
HCPT and
CPT are
indole alkaloids originally isolated from th. Chinese tree, Camptotheca acuminata. They have been shown to have a wide spectrum of anticancer activity both in vitro and in vivo. The use of these camptothecins, however, has been hampered by their water-insolubility. In the present study, following screening of their in vitro antitumor activity, we determined their in vivo antitumor effects using C.B-17-scid/scid mice bearing LS174T or DLD-1 xenografts.
Tumor-bearing mice were treated with oral doses of
HCPT (1, 3, or 6 mg/kg/day) or
CPT (1 or 3 mg/kg/day), 5 days per week for 2 weeks (LS 174T) or 3 weeks (DLD-1). Growth of the xenografts was significantly inhibited by
HCPT and
CPT in a dose-dependent manner, with marked reductions in
tumor mass occurring in those groups given
HCPT at 6 mg/kg/day or
CPT at 3 mg/kg/day. Pathologic examination confirmed the dose-dependent
atrophy of the
adenocarcinomas. In summary, this study demonstrates the potential use of water-insoluble camptothecins when given by the oral route for treatment of human
colon cancer, and provides the basis for the design of future human trials with these anticancer drugs.