Abstract 831: CPT1A inhibition sensitizes diffuse large B-cell lymphoma to venetoclax treatment

Abstract First-line immunochemotherapy fails to achieve a durable response in up to one third of patients with diffuse large B-cell lymphoma (DLBCL). Therapy resistance is mediated, in part, by ineffective elimination of B-cells protected by a metabolic tumor-stroma interaction. Carnitine palmitoyltransferase 1A (CPT1A), a component of the prognostic DLBCL-LAMI signature, plays a major role in transporting fatty acids - partly provided by stromal cells - into mitochondria to support B-cell metabolism. We investigated the CPT1A inhibitors ST1326 and perhexiline for their ability to eliminate lymphoma cells in the presence of stromal cells and the potential of sensitizing them to the therapeutic BCL2 inhibitor venetoclax. CPT1A protein expression was evaluated in primary tumor specimens by immunohistochemistry using TMAs. CPT1A inhibitors and venetoclax (ABT-199) were tested on different pre-clinical models: (1) 15 DLBCL cell lines, (2) co-culture models of DLBCL cell lines and either stromal cell line HS-5 or primary DLBCL-cancer associated fibroblasts to evaluate the induction of B-cell death in a stromal environment, and (3) patient-derived DLBCL cells. Therapeutic efficacy was assessed using MTT cytotoxicity and CellTiter Glo 2.0 assays. Effects on lipid metabolism, molecular signaling and induction of cell death were investigated by oil red O staining, immunoblots and AnxV/TMRM flow cytometry, respectively. CPT1A protein was expressed in 77% (67/87) of primary DLBCL (cytoplasmic staining, cut-off 20%). Both CPT1A inhibitors impaired the viability of lymphoma cells: perhexiline treatment was cytotoxic in 5/5 cell lines (IC50 = 5.5-7.5 µM), ST1326 in 10/15 cell lines (IC50 = 5-18 µM). Viability of normal fibroblasts was not affected by either drug. Perhexiline lost its cytotoxic effect against lymphoma cells when co-cultured with stromal cells. In contrast, ST1326 remained effective in killing DLBCL cells also in stromal environment. Suppression of fatty acid transport into mitochondria by ST1326 resulted in cytoplasmic lipid accumulation, suppression of anti-apoptotic Bcl-XL and phospho-AKT, and induction of apoptotic cell death. The combination of ST1326 with the BCL2 inhibitor venetoclax increased its cytotoxic efficacy. Three DLBCL cell lines that were BCL2-positive but resistant to venetoclax were sensitized by ST1326 to the BCL2 inhibitor, an effect that persisted in the presence of stromal cells. In patient-derived DLBCL models (partly from patients with poor response to standard immunochemotherapy), CPT1A inhibition impaired the viability of primary DLBCL cells and enhanced the antitumor activity of venetoclax. Targeting fatty acid metabolism using ST1326 effectively eliminates lymphoma cells in the presence of stromal cells and increases significantly the efficacy of the BCL2-specific inhibitor venetoclax, thus providing a new candidate approach in the treatment of DLBCL. Citation Format: Sophia Steinlein, Heike Horn, Emma Attwood, Annette M. Staiger, Katrin S. Kurz, Andreas Rosenwald, German Ott, Claudia Kalla. CPT1A inhibition sensitizes diffuse large B-cell lymphoma to venetoclax treatment. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 831.