Colon cancer cells contain high levels of
cystathionine-beta-synthase (CBS). Its product,
hydrogen sulfide (H2S) promotes the growth and proliferation of
colorectal tumor cells. In order to improve the antitumor efficacy of the prototypical CBS inhibitor
aminooxyacetic acid (AOAA), we have designed and synthesized YD0171, a methyl
ester derivative of AOAA. The antiproliferative effect of YD0171 exceeded the antiproliferative potency of AOAA in HCT116 human
colon cancer cells. The
esterase inhibitor
paraoxon prevented the cellular inhibition of CBS activity by YD0171. YD0171 suppressed mitochondrial respiration and glycolytic function and induced G0/G1 arrest, but did not induce
tumor cell apoptosis or
necrosis. Metabolomic analysis in HCT116 cells showed that YD0171 affects multiple pathways of cell metabolism. The efficacy of YD0171 as an inhibitor of
tumor growth was also tested in nude mice bearing subcutaneous HCT116
cancer cell xenografts. Animals were treated via
subcutaneous injection of vehicle, AOAA (1, 3 or 9 mg/kg/day) or YD0171 (0.1, 0.5 or 1 mg/kg/day) for 3 weeks.
Tumor growth was significantly reduced by 9 mg/kg/day AOAA, but not at the lower doses. YD0171 was more potent:
tumor volume was significantly inhibited at 0.5 and 1 mg/kg/day. Thus, the in vivo efficacy of YD0171 is 9-times higher than that of AOAA. YD0171 (1 mg/kg/day) attenuated
tumor growth and
metastasis formation in the intracecal HCT116
tumor model. YD0171 (3 mg/kg/day) also reduced
tumor growth in patient-derived
tumor xenograft (PDTX) bearing athymic mice. YD0171 (3 mg/kg/day) induced the regression of established HCT116
tumors in vivo. A 5-day safety study in mice demonstrated that YD0171 at 20 mg/kg/day (given in two divided doses) does not increase plasma markers of organ injury, nor does it induce histological alterations in the liver or kidney. YD0171 caused a slight elevation in plasma
homocysteine levels. In conclusion, the
prodrug approach improves the pharmacological profile of AOAA; YD0171 represents a prototype for CBS inhibitory anticancer
prodrugs. By targeting
colorectal cancer bioenergetics, an emerging important hallmark of
cancer, the approach exemplified herein may offer direct translational opportunities.