Abstract 2980: Cystathionine-beta-synthase (CBS)-derived hydrogen sulfide (H2S) supports proliferation, migration and bioenergetics in colon cancer-associated fibroblasts (CAFs)

Introduction: Our group has recently demonstrated that CBS, one of the H2S-producing enzymes, is abundantly overexpressed in human colorectal cancer (CRC) tissue specimens resulting in an increased H2S production. In order to extend our observations, we have now compared, using immunohistochemistry, CBS expression in carcinoma-associated fibroblasts (CAFs) compared to normal colonic fibroblasts (NCFs) in human colon adenocarcinoma samples. The overall goal of our studies is to characterize how the CBS/H2S axis contributes to the malignant phenotype of the CAFs in the tumor microenvironment. Methods: Human CAFs and NCFs were collected from CRC under an IRB approved protocol and cultured in vitro. Western blot analysis of both NCF and CAF was performed to determine CBS protein expression levels. SiRNA/shRNA-mediated silencing of CBS in CAFs was performed. A pharmacological inhibitor of CBS, aminooxyacetic acid (AOAA), in both CAF and NCF cultures was also utilized. Hydrogen sulfide (H2S) levels were measured using the fluorogenic probe 7-Azido-4-methylcoumarin. We also performed proliferation assays using a coulter counter in CAFs, NCFs, and CAFs subjected to siRNA/shRNA-mediated CBS silencing or AOAA. Control cells were transduced with shNT vectors. Cells were also treated with the slow-releasing H2S donor GYY4137. We also conducted cell migration assays in transwell chambers (migration of CAFs toward conditioned media (CM) collected either from HCT116 cells or normal colon mucosal cells (NCM356). Finally, the XF24 Extracellular Flux Analyzer (Seahorse) was used to measure bioenergetic function in CAFs subjected to siRNA/shRNA-mediated silencing of CBS or treated with AOAA. Results: CBS protein expression and H2S production in CAFs was increased compared to NCFs. The H2S donor, GYY 4137, increased the proliferation rate of CAFs but not of NCFs. CBS silencing or AOAA treatment reduced CAF migration toward conditioned media from HCT116 cells. Genetic or pharmacological inhibition of CBS in CAF cells suppressed key bioenergetic parameters including basal respiration, ATP production, maximal respiratory capacity, and spare respiratory capacity compared to NCF cells or CAF shNT cells. Conclusions: Thus, CBS/H2S axis serves as a mechanism to support CAFs’ function. In these cells, H2S contributes to maintaining their bioenergetic functions, which, in turn, promotes their proliferation and migration toward colon cancer cells. We hypothesize that these processes may contribute CRC progression. Citation Format: Katalin Modis, Manjit Maskey, Paul Johnson, Csaba Szabo, Mark R. Hellmich, Celia Chao. Cystathionine-beta-synthase (CBS)-derived hydrogen sulfide (H2S) supports proliferation, migration and bioenergetics in colon cancer-associated fibroblasts (CAFs) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2980. doi:10.1158/1538-7445.AM2017-2980