Cell-of-origin and genetic drivers define advanced bladder cancer subtypes and potential therapeutic response in mouse models.

BACKGROUND

Bladder cancer (BC) remains a major clinical challenge owing to its high recurrence, limited treatment options, and molecular heterogeneity. Despite recent therapeutic advances, prognosis remains poor and resistance to treatment is common, underscoring the need for improved experimental models to study tumorigenesis and therapeutic response. A critical obstacle in advanced BC research is the scarcity of in vivo models that accurately replicate invasive and metastatic behavior and serve as robust preclinical tools for evaluating new therapies, especially in immunocompetent settings.

METHODS

To assess how the cell of origin and specific driver genes influence bladder tumorigenesis and subtype specification, we engineered four genetically modified mouse models of advanced BC. Two combinations of tumor suppressor genes—either Pten and Trp53, or Pten, Trp53, Rb1, and Rbl1— were targeted either basal or suprabasal urothelial cells via intravesical Cre-adenovirus delivery. From tumors arising in these models, we derived multiple cell lines and established syngeneic graft models. Both genetically engineered mouse models and derived mouse cell lines were extensively characterized and transcriptionally compared with advanced human BC and human BC cell lines, and were further utilized as preclinical platforms to evaluate therapeutic responses.

RESULTS

Loss of the retinoblastoma gene family reduced cancer-specific survival and was associated with more differentiated carcinomas. In both genetic backgrounds, luminal-derived tumors appeared earlier but displayed fewer metastatic events. Histopathological and transcriptomic analyses revealed that these tumors resemble human basal-squamous and stroma-rich subtypes, sharing regulatory networks and activated signaling pathways with human invasive BC. Tumors lacking retinoblastoma family genes exhibited enhanced immune infiltration, reinforcing their value for diverse preclinical applications. To overcome detection and latency limitations, we established syngeneic graft models from tumor-derived cell lines. These models were validated as preclinical platforms, exhibiting therapeutic responses to CDK4/6 inhibition and anti-PD-L1 immunotherapy.

CONCLUSIONS

These novel mouse models faithfully recapitulate key molecular, histological, and immune features of human invasive BC. They represent versatile and clinically relevant preclinical models for dissecting disease progression mechanisms and evaluating emerging therapeutic strategies within an intact immune environment.