Asparagine synthetase and G-protein coupled estrogen receptor are critical responders to nutrient supply inKRASmutant colorectal cancer

Abstract

AbstractThe nutrient status of the tumor microenvironment has major impacts on cell growth. Under nutrient depletion, asparagine synthetase (ASNS)-mediated asparagine production increases to sustain cell survival. G protein-coupled estrogen receptor-1 (GPER1) signaling converges via cAMP/PI3K/AKT with KRAS signaling to regulateASNSexpression. However, the role of GPER1 in CRC progression is still debated, and the effect of nutrient supply on bothASNSandGPER1relative toKRASgenotype is not well understood. Here, we modeled a restricted nutrient supply by eliminating glutamine from growing cancer cells in a 3D spheroid model of human female SW48KRASwild-type (WT) andKRASG12A mutant (MT) CRC cells, to examine effects onASNSandGPER1expression. Glutamine depletion significantly inhibited cell growth in bothKRASMT and WT cells; however,ASNSandGPER1were upregulated inKRASMT compared to WT cells. When nutrient supply was adequate,ASNSandGPER1were not altered between cell lines. The impact of estradiol, a ligand for GPER1, was examined for any additional effects on cell growth. Under glutamine deplete conditions, estradiol decreased the growth ofKRASWT cells but had no effect onKRASMT cells; estradiol had no additive or diminutive effect on the upregulation ofASNSorGPER1between the cell lines. We further examined the association ofGPER1andASNSlevels with overall survival in a clinical colon cancer cohort of The Cancer Genome Atlas. Both highGPER1andASNSexpression associated with poorer overall survival for females only in advanced stage tumors. These findings suggest thatKRASMT cells have mechanisms in place that respond to decreased nutrient supply, typically observed in advanced tumors, by increasing the expression ofASNSandGPER1to drive cell growth. Furthermore,KRASMT cells are resistant to the protective effects of estradiol under nutrient deplete conditions. ASNS and GPER1 may therefore be potential therapeutic targets that can be exploited to manage and controlKRASMT CRC.