HOXB4 Promotes Bladder Cancer Progression in Part Through Transcriptional Activation of Smoothened

Homeobox B4 (HOXB4) is a homeobox transcription factor implicated in development and oncogenesis; however, its role in bladder cancer (BCa) remains insufficiently defined. Bladder cancer is among the most common malignancies worldwide, and its high rates of recurrence and progression highlight the need to identify new molecular drivers and therapeutic targets. In this study, we show that HOXB4 is overexpressed in BCa and that elevated levels of HOXB4 are associated with unfavorable clinical outcomes. Functionally, HOXB4 knockdown markedly suppressed cellular proliferation, migration, invasion, and experimental lung colonization in vitro and in vivo. Furthermore, transcriptomic analyses and validation assays, including quantitative PCR, immunoblotting, RNA-sequencing, luciferase reporter, and chromatin immunoprecipitation (ChIP) assays, demonstrated that perturbing HOXB4 modulates Hedgehog signaling. Mechanistically, HOXB4 bound to the Smoothened (SMO) promoter and transcriptionally activated SMO, thereby amplifying Hedgehog pathway activity and promoting malignant phenotypes in BCa cells. Collectively, these findings delineate a HOXB4-SMO axis that drives BCa progression and suggest this pathway as a candidate target for patient stratification and therapeutic exploration. Future studies should validate these findings in larger multi-center cohorts and assess the therapeutic potential of SMO inhibition in preclinical BCa models.