LAUSR

Activation of the nuclear factor erythroid 2-related factor 2 (NRF2) pathway, either through gain-of-function mutations in the NRF2 encoding gene NFE2L2 or through loss-of-function of its suppressor, Kelch-like ECH-associated protein 1 (KEAP1), is a frequent manifestation in various malignancies. NRF2 activation exerts pro-tumoral effects in part by altering cancer cell metabolism. We previously reported a novel mechanism of NRF2 tumoral immune suppression through selective upregulation of the tryptophan metabolizing enzyme kynureninase (KYNU) in lung adenocarcinoma. In the current study, we explored the Pan-Cancer relevance of NRF2-mediated KYNU upregulation. We analyzed the gene expression dataset for 9,801 tumors representing 32 cancer types in The Cancer Genome Atlas (TCGA). Elevated KYNU expression levels paralleled increased gene-based signatures of NRF2-activation and was strongly associated with an immunosuppressive tumor microenvironment, marked by high expression of gene-based signatures of Tregs as well as immune checkpoint blockade-related genes CD274 (PDL-1), PDCD1 (PD-1), and CTLA4, regardless of cancer type. Cox proportional hazard models further revealed that increased tumoral KYNU gene expression was prognostic for poor overall survival in several cancer types, including thymoma, acute myeloid leukemia, low grade glioma, kidney renal papillary cell carcinoma, gastric adenocarcinoma, and pancreatic ductal adenocarcinoma (PDAC). Using PDAC as a model system, we confirmed that siRNA-mediated knockdown of NRF2 reduces KYNU mRNA expression, whereas activation of NFE2L2 (the encoding gene for NRF2) through either small molecule agonists or siRNA-mediated knockdown of KEAP1 upregulated KYNU. Metabolomic analyses of conditioned media from PDAC cell lines revealed elevated levels of KYNU-derived anthranilate, confirming KYNU as enzymatically functional. Collectively, our findings highlight the multi-cancer relevance of the NRF2-KYNU axis and of tumoral KYNU as a prognostic marker of poor overall survival associated with immunosuppression. Citation Format: Ricardo A. Leon Letelier, Ali H. Abdel Sater, Yihui Chen, Ranran Wu, Jennifer B. Dennison, Soyoung Park, Ehsan Irajizad, Hiroyuki Katayama, Jody Vykoukal, Samir Hanash, Edwin J. Ostrin, Johannes F. Fahrmann. KYNU upregulation is a prominent feature of NRF2-activated cancers and is associated with tumor immunosuppression and poor prognosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6031.