Chemotherapy resistance of urinary bladder cancer mediated by a Notch and Wnt co-regulatory module of stemness

Despite breakthroughs in molecularly targeted and immune therapies, the prognosis for patients with urinary bladder cancer (UBC) has remained unsatisfactory over the past few decades. Understanding the molecular underpinnings of UBC treatment refractoriness is crucial for identifying novel therapeutic targets and strategies. Cancer stemness plays a pivotal role in the oncogenesis and treatment resistance of UBC, while the underlying molecular regulatory mechanisms are poorly understood. We identified isoform 1 of ASPM (ASPM-i1) as the most upregulated stemness-associated factor in tumorigenic UBC cells, predominantly expressed by ALDH1+ stem-like cancer cells. Pairing genetic ASPM-i1 inhibition with standard chemotherapeutic agents used in the treatment of UBC, including cisplatin and gemcitabine, circumvents the treatment resistance of tumorigenic and stem-like UBC cells. Mechanistically, ASPM-i1 interacts with the Disheveled (DVL) and intracellular NOTCH proteins, thereby attenuating CUL3- or FBXW7-mediated ubiquitination and the subsequent proteasomal degradation. The regulatory module concomitantly enhances the activities and ligand responsiveness of the Wnt and Notch signaling pathways in UBC cells. As a result, ASPM-i1 inhibition sensitized tumorigenic UBC cells to chemotherapy in a NOTCH- and DVL-dependent manner. In human UBC tissues, ASPM-i1 shows substantial cell-to-cell heterogeneity and is upregulated in a subset (46.4%) of tumors, correlating with poor clinical prognosis. This study reveals a crucial co-regulatory module of Notch and Wnt signaling that mediates stemness and chemotherapy resistance in tumorigenic UBC cells; its inhibition provides a novel approach to enhance chemosensitivity and improve therapeutic outcomes in human UBC.