Colorectal cancer and hepatocellular carcinoma cases account for a total of 12% of cancer deaths in the United States, highlighting the critical need for improved therapeutics. Cytochrome P450 2W1 (CYP2W1) is expressed in 30% of colorectal and 53% of hepatocellular carcinoma tumors but absent in healthy adult tissue. While endogenous CYP2W1 substrates are unknown, it can monooxygenate xenobiotics. Starting from the natural product duocarmycin a series of inactive prodrugs were designed that are converted to cytotoxins only by CYP2W1 and CYP1A1. To help design duocarmycin analogues more specific for CYP2W1 activation, it is crucial to understand CYP2W1 structure and function.
One method is to build a pharmacophore identifying the physicochemical characteristics of ligands compatible with active site binding. To initiate these studies, human CYP2W1 has been expressed in E. coli, purified, and an artificial luminescent substrate identified. A structurally diverse set of about 7,000 biologically-active compounds were screened for inhibition. Of those, 705 compounds were confirmed as inhibitors for a 9.96% hit rate. These compounds will be tested to ensure they do not inhibit other assay components before determining their IC50 values. Ranking compounds by IC50 and comparing ligand structures should help determine complementary features of the CYP2W1 active site. Ultimately better characterization of CYP2W1 can be used to improve selectivity of duocarmycin prodrugs for CYP2W1 activation for colorectal and hepatocellular carcinoma therapies.
Supported by NIH R37 GM076343 and T32 GM007767