Gossypol and its analogs, through their ability to bind to and inactivate BH3 domain-containing anti-apoptotic proteins, have been shown to inhibit the growth of various human cancer cells in culture and xenograft models. Here, we evaluated the antitumor efficacy of a novel gossypol derivative and BH3 mimetic ch282-5 (2-aminoethanesulfonic acid sodium-gossypolone) in colon cancer models. Several innovative combination strategies were also explored and elaborated.

Ch282-5 was synthesized by modifying the active aldehyde groups and R groups of gossypol according to a computer-aided drug design program. The stability of ch282-5 was examined by HPLC and cytotoxic effects of ch282-5 on colon cancer cells were assessed by MTS assay. Activation of mitochondrial apoptotic pathway by ch282-5 was evidenced with a series of molecular biology techniques. In vivo antitumor activity of ch282-5 and its combination with chloroquine, rapamycin, oxaliplatin and ABT-263 was also evaluated in colon cancer xenograft model and experimental liver metastasis model.

Ch282-5 showed antiproliferative and pro-cell death activity against colon cancer cells both in vitro and in vivo, and the response to the drug correlated with inhibition of anti-apoptotic Bcl-2 proteins, induction of mitochondria-dependent apoptotic pathway and disruption of mitophagy and mTOR pathway. Ch282-5 also suppressed liver metastasis produced by intrasplenic injection of colon cancer cells. Furthermore, ch282-5 could potentiate the effectiveness of oxaliplatin and rescue ABT-263 efficacy by downregulaton of Mcl-1 and elevation of platelet number.

These findings provide a rational basis for clinical investigation of this highly promising BH3 mimetic in colon cancer.