Glutaminase inhibition ameliorates cancer-associated fibroblast lipid support of pancreatic cancer cell growth.

Abstract

Background: Lipid homeostasis is critical for pancreatic adenocarcinoma (PDAC) cell survival under hypoxic and nutrient-deprived conditions. Hypoxia inhibits unsaturated lipid biosynthesis, compelling cancer cells to depend on exogenous unsaturated lipids to counteract saturated lipid-induced toxicity. Our previous work revealed that cancer-associated fibroblasts (CAFs) secrete unsaturated lipids, primarily lysophosphatidylcholines (LPCs), to alleviate lipotoxic stress in PDAC cells. Here, we conducted a drug screen to identify compounds that bypass the rescue effect of exogenous LPCs on cancer cell survival under stress.

Methods: We employed high-throughput screening of a bioactive chemical library with 3,336 compounds, including FDA-approved drugs and drug-like molecules against defined molecular targets. Two assays were performed: a cytotoxicity assay to exclude indiscriminately toxic compounds at 1 μM and an LPC crosstalk inhibition assay to identify compounds that selectively reduce cancer cell viability in the presence of LPCs under stress conditions.

Results: CB-839, a glutaminase inhibitor, was identified as the most effective compound, selectively inhibiting the LPC-mediated rescue of PDAC cell viability effect without intrinsic cytotoxicity. Mechanistic studies revealed that CB-839 induces cell death by activating the pro-apoptotic ATF4/CHOP pathway, reducing antioxidant production, and increasing reactive oxygen species (ROS). While CB-839 showed limited efficacy against PDAC tumor cells alone in vivo, it modestly inhibited tumor growth in a PDAC-CAF co-implanted subcutaneous mouse model, highlighting its potential to disrupt CAF-mediated nutrient support. Additionally, glutamine antagonists showed more potent tumor-suppressive effects than CB-839.

Conclusion: Our findings emphasize the importance of glutamine metabolism inhibition in suppressing tumor growth and disrupting CAF-mediated crosstalk. We further underscore the potential of glutamine antagonist prodrugs as a strategy to target metabolic vulnerabilities in PDAC.