Abstract 6991: Transcriptomic profiling of human and mouse models highlights YAP pathway hyperactivation as the underlying mechanism of the biological and clinical aggressiveness of Numb-defective bladder cancer

Abstract

Abstract In this study, we identify a previously uncharacterized role for the tumor suppressor, Numb, in bladder tumorigenesis, defining new predictive biomarkers and potentially actionable targets for the treatment of non-muscle-invasive bladder cancers. We conducted a comprehensive IHC analysis of Numb expression leveraging two retrospective longitudinal cohorts comprising 356 post-cystectomy muscle-invasive bladder cancer (MIBC) patients and 77 high-grade non-muscle-invasive (NMIBC) patients with transurethral resections. We found that Numb expression is frequently deregulated in the tumor compared to the adjacent normal urothelium, with NumbLow status correlating with poorer prognosis both in MIBC, associated with advanced stage at diagnosis, vascular invasion, and worse overall survival, and in NMIBC, where a NumbLow status associates with a higher rate of progression to life-threatening MIBC disease. In a transgenic mouse model with targeted deletion of the Numb gene in the basal layer of the bladder mucosa, we observed that loss of Numb per se is sufficient to drive malignant transformation of the normal urothelium and accelerates tumorigenesis in carcinogen-induced models. Integrative transcriptomic analysis of human and mouse Numb-deficient BC models revealed consistent dysregulation of the YAP1/TAZ1 inhibitory Hippo pathway, identifying YAP1 transcriptional hyperactivation as the most distinguishing trait downstream of NUMB loss. Through genetic and pharmacological functional inhibition studies in relevant mouse and human BC cell line-based models, we provide proof-of-evidence that interfering with YAP pathway activation at multiple upstream levels of the Hippo cascade reverts the aggressive Numb loss-associated tumor phenotypes, in particular growth and invasive/migratory potential, thereby highlighting the YAP pathway as a potential therapeutical vulnerability for the treatment of clinically aggressive Numb-deficient human BC. We also identified a gene signature of early BC depending on loss of Numb that we extensively validated for its potential as a predictor of NMIBC to MIBC progression, arguing for its clinical application as a biomarker for NIMBC patient stratification for targeted anti-YAP signaling treatment to prevent MIBC transition. In summary, our study identifies a previously uncharacterized role of Numb in bladder cancer progression, highlighting its potential as a predictive biomarker of NMIBC to MIBC transition and response to targeted therapies, thereby advancing a framework for precision oncology for NMIBC patients at high risk of progression to life-threatening MIBC disease. Citation Format: Francesco Antonio Tucci, Rosa Pennisi, Maria Grazia Filippone, Roberta Bonfanti, Francesco Romeo, Damiano Rigiracciolo, Stefano Freddi, Francesca Sanguedolce, Giuseppe Renne, Giancarlo Pruneri, Gianluca Vago, Daniela Tosoni, Salvatore Pece. Transcriptomic profiling of human and mouse models highlights YAP pathway hyperactivation as the underlying mechanism of the biological and clinical aggressiveness of Numb-defective bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6991.