Abstract 624: Classifying cGAS-STING activity links chromosomal instability with immunotherapy response in metastatic bladder cancer

Abstract

Abstract The cGAS-STING pathway serves a critical role in anti-cancer therapy. Particularly, response to immunotherapy is likely driven by both active cGAS-STING signaling that attracts immune cells, and by the presence of cancer neoantigens that presents as targets for cytotoxic T-cells. Chromosomal instability (CIN) is a hallmark of cancer, but also leads to an accumulation of cytosolic DNA that in turn results in increased cGAS-STING signaling. To avoid triggering the cGAS-STING pathway, it is commonly disrupted by the cancer cells, either through mutations in the pathway or through transcriptional silencing. Given its effect on the immune system, determining the cGAS-STING activation status prior to treatment initiation is likely of clinical relevance, but to date no robust method has been developed. Here, we used combined expression data from 2307 tumors from five cancer types from The Cancer Genome Atlas (TCGA) to define a novel cGAS-STING activity score based on eight genes with a known role in the pathway. Using unsupervised clustering, four distinct categories of cGAS-STING activation were identified. In multivariate models, the cGAS-STING active tumors show improved prognosis. Importantly, in an independent bladder cancer immunotherapy treated cohort, patients without cGAS-STING activation showed very limited response to treatment, while patients with strong cGAS-STING activation showed improved response and improved prognosis, particularly among patients with high CIN and high numbers of neoantigens. In a multivariate model, a significant interaction was observed between CIN, neoantigens, and cGAS-STING activation. Together, this supports a role of cGAS-STING activity as a predictive biomarker in combination with measures of CIN and neoantigens for the application of immunotherapy. Citation Format: Mateo Sokac. Classifying cGAS-STING activity links chromosomal instability with immunotherapy response in metastatic bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 624.