Abstract PR007: Chronic cGAS activation drives immunosuppressive remodeling and resistance to antiangiogenic tyrosine kinase inhibitors in ccRCC

Abstract Purpose: Tyrosine kinase inhibitors (TKIs) targeting VEGF signaling are widely used in ccRCC, either alone or combined with immune checkpoint blockade (ICB). Although TKI–ICB combinations improve outcomes, their durability is inferior to dual PD-1/CTLA-4 blockade, and prolonged TKI exposure inevitably induces resistance. Increasing evidence highlights the tumor immune microenvironment (TIME) in therapeutic escape; however, the mechanisms underlying TKI-driven remodeling of the TIME to promote resistance remain poorly defined. Here, we systematically characterized TKI-driven TIME reprogramming to develop therapeutic strategies to overcome resistance to TKIs. Methods: ccRCC cell lines (786-O, RCC4) were exposed to prolonged TKI treatment with sunitinib and axitinib to model extended clinical therapy. A tumor cell–monocytes co-culture system was applied to assess TKI-induced alterations in THP-1 cells. Both LVRCC67 and Renca murine RCC models were used to evaluate therapeutic response in vivo. Molecular analyses included Western blotting, qPCR, and immunofluorescence. Results: Re-analysis of bulk RNA-seq of a ccRCC PDX model (Diaz-Montero et al., Br J Cancer, 2016) showed significant enrichment of cGAS-mediated cytosolic DNA-sensing and type I interferon pathways during tumor escape from sunitinib. Re-analysis of scRNA-seq data from pazopanib-treated patients (Chen et al., Cancer Letters, 2024) also revealed increased activation of the cGAS pathway and its downstream chemokines in non-responders. These results indicate that cGAS pathway activation may mediate resistance to TKIs. To test this hypothesis, we further confirmed that prolonged sunitinib or axitinib exposure (2 weeks) in 786-O and RCC4 cells induced DNA damage, cytosolic DNA accumulation, and upregulation of immune-attracting cytokines (e.g., CCL3, CCL5, CXCL10) and and the macrophage modulating cytokine IL-6 in a cGAS-dependent manner. In human monocyte THP-1 cells, IL-6 stimulation induced the expression of CD163 and PVR, two markers associated with immunosuppressive macrophage function. Co-culturing THP-1 cells with 786-O cells also induced CD163 and PVR expression in THP-1 cells, which was reduced when co-cultured with 786-O cGAS KD cells. In contrast, co-culture with long-term sunitinib-treated 786-O cells further enhanced the expression of CD163 and PVR. Notably, this effect was abrogated by IL-6 receptor blockade using tocilizumab. To functionally validate the role of cGAS signaling in immune modulation and TKI response in vivo, we generated a Cgas-knockdown LVRCC67 cell line. Cgas-deficient tumors grew more slowly and exhibited enhanced sensitivity to sunitinib and axitinib. Loss of cGas reduced Cd3 (T-cell marker) and Cd163 (M2 macrophage marker) expression in tumors, whereas sunitinib treatment induced the opposite effects. Conclusions: Prolonged TKI treatment promotes an immunosuppressive TIME and drives resistance via chronic tumor-intrinsic cGAS activation. Targeting the cGAS pathway and IL-6 signaling may represent promising strategies to overcome TKI resistance. Citation Format: Hongchao He, Xiande Liu, Xuesong Zhang, Hoang Anh, Eric Jonasch. Chronic cGAS activation drives immunosuppressive remodeling and resistance to antiangiogenic tyrosine kinase inhibitors in ccRCC [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 PR007.