Diallyl disulfide suppresses the growth of human colon tumor cell xenografts in athymic nude mice

The present studies examined the antiproliferative effects of diallyl disulfide (DADS) on the growth of human colon tumor cell line, HCT-15, xenografts in 6-wk-old female NCr nu/nu mice with an initial body weight of 20-22 g. Intraperitoneal injection of 1 mg DADS thrice weekly reduced tumor volume by 69% (P < 0.05) without apparent ill consequences such as altered growth of the host. Providing this quantity of DADS intragastrically also inhibited growth of the HCT-15 tumor. At equivalent DADS dosages, intraperitoneal treatment was proportionately more effective (P < 0.05) in reducing tumor growth than gastric intubation. Tumor inhibition caused by DADS (0.5 mg thrice weekly) was similar to that occurring with 5-fluorouracil (5-FU) treatment (0.5 mg thrice weekly). Combining DADS and 5-FU was no more effective in inhibiting tumor growth than using either compound alone. However, concurrent DADS treatment significantly (P < 0.05) inhibited the depression in leukocyte counts and spleen weight and prevented the elevated plasma urea caused by 5-FU treatment. These data suggest that DADS, a constituent of garlic oil, reduces the toxicity of 5-FU and is an effective antitumorigenic agent against xenografts resulting from an established human colon tumor cell line.