SMAD3-driven cell state transitions underpin immunoresistance in bladder cancer

Despite the clinical success of anti-PD-1/PD-L1 immunotherapy in a subset of patients with high-risk bladder cancer (BLCA), most tumors remain refractory to treatment. We hypothesized that immunotherapy resistance is encoded within the intrinsic signaling state of BLCA cells and arises through specific cell-state transitions that precede therapeutic exposure. To test this hypothesis, we applied a cell State Transition Assessment and Regulation (cSTAR) framework to identify key signaling modules and aberrant causal network connections that (i) drive oncogenic progression and acquisition of aggressive phenotypes and (ii) govern BLCA cell susceptibility to T cell-mediated cytotoxicity. cSTAR analysis identified TGF{beta}/SMAD3 signaling as the principal driver of both oncogenic transformation and immunoresistance in BLCA cells. Inhibiting SMAD3 sensitized BLCA cells to PD-1-expressing Jurkat cells and primary human CD4+ T cell-mediated cytotoxicity through suppression of autophagy and activation of multiple cell death pathways. By integrating cell state transition analysis with functional immune co-culture assays, our work demonstrates that tumor cell state transitions control sensitivity to T cell killing, complementing established immune-intrinsic mechanisms of immunotherapy response.