Abstract A024: Interrogating mechanisms underlying AHCYL1 dependency in kidney cancer

Abstract Background. Despite the advent of novel therapies and improvements in existing treatment modalities, renal cancer remains difficult to cure in patients with advanced disease (5-year median survival ∼18 months). This, combined with the growing incidence of renal cancer, highlights the critical need for novel therapeutic targets. Methods. By mining publicly available genetic screening data (e.g., Broad Institute’s DepMap and Novartis’s DRIVE), we identified the S-adenosylhomocysteine (SAH) hydrolase paralog, AHCYL1, as a kidney-lineage enriched genetic dependency. Our rigorous validation studies, both in vitro and in vivo, show that genetic loss of AHCYL1 (e.g., using CRISPR/Cas9) leads to fitness defects across a panel of transformed RCC cell lines and RCC patient-derived organoids. Results. Several functions of AHCYL1 have been previously described – including SAH sensing/metabolism, apoptotic control, and Ca+2 signaling. Previous data generated in our laboratory (and others) has highlighted the importance of methionine/cysteine metabolism in renal cancers. We hypothesized that AHCYL1’s putative role in SAH/Met metabolism may underly AHCYL1 dependency in RCC. AHCYL1 has poor SAH hydrolysis activity; however, it can indirectly regulate SAM/SAH pools via interaction with AHCY. Additionally, we discovered that binding cofactor NAD+ resulted in a conformational change that forced AHCYL1 into a thermostable complex, which aligned with a novel role for AHCYL1 as a NAD+ sensor. Consistent with this, cell-based studies showed that AHCYL1 loss depletes NAD+ and perturbs the abundance of several Met/Cys metabolism intermediates. This is biologically relevant because dietary interventions, such as Met restriction, exacerbate the dependence on AHCYL1 in vivo. Surprisingly, we found that AHCYL1 loss also disrupts central carbon metabolism [e.g., depletes tricarboxylic acid (TCA) intermediates] and isotope tracing experiments, using 13C6-glucose, indicated a decrease in labeled TCA intermediates upon AHCYL1 inactivation. Importantly, supplementing depleted TCA metabolites (e.g., succinate) is sufficient to rescue the fitness defects triggered by AHCYL1 loss. Together, perturbations in both Met and TCA metabolism can regulate AHCYL1’s oncogenic role in RCC. Conclusions. Altogether, our findings reassign a metabolic role for AHCYL1 in RCC, provide a mechanistic basis for AHCYL1’s onco-metabolic functions. AHCYL1 is inherently druggable and our ongoing studies (e.g., a DEL screen) are addressing the feasibility of targeting AHCYL1 to eventually exploit this target in kidney cancer therapy. Citation Format: Noah M. Dubasik, Pooneh Koochaki, Jesse Coker, Christopher Goins, Shaun R. Stauffer, Abhishek A. Chakraborty. Interrogating mechanisms underlying AHCYL1 dependency in kidney cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Kidney Cancer Research: From Molecular Insights to Therapeutic Breakthroughs; 2026 Mar 13-16; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2026;86(5_Suppl_2):Abstract nr A024.