CAB39 modulates epithelial–mesenchymal transition through NF-κB signaling activation, enhancing invasion, and metastasis in bladder cancer

Bladder cancer (BC), the predominant urological malignancy in men, exhibits complex molecular underpinnings contributing to its progression. This investigation aims to elucidate the expression dynamics of calcium-binding protein 39 (CAB39) in both healthy and cancerous tissues and to explore its functional role in the epithelial–mesenchymal transition (EMT) within human bladder cancer contexts. Utilizing immunohistochemistry and quantitative reverse transcription analyses, we assessed CAB39 expression across BC specimens and cell lines. Further, we implemented wound healing, cell invasion, and CCK-8 proliferation assays in CAB39-knockdown cell lines, alongside a nude mouse xenograft model, to gauge the impact of diminished CAB39 expression on the invasive, migratory, and proliferative capacities of BC cells. Our gene set enrichment analysis probed into the repertoire of genes augmented by increased CAB39 expression in BC cells, with subsequent validation via western blotting. Our findings reveal a pronounced overexpression of CAB39 in both BC tissues and cellular models, inversely correlated with disease prognosis. Remarkably, the oncogenic trajectory of bladder cancer was mitigated upon the establishment of shRNA-mediated CAB39 knockdown in vitro and in vivo, effectively reversing the cancer's invasive and metastatic behaviors and curbing tumorigenesis in xenograft models. Hence, CAB39 emerges as a critical biomarker for bladder cancer progression, significantly implicated in facilitating EMT via the upregulation of neural cadherin (N-cadherin) and the suppression of epithelial cadherin through NF-κB signaling pathways. CU-T12-9 effectively overturned the downregulation of p65-NF-kB and N-cadherin, key elements involved in EMT and cell motility, induced by CAB39 knockdown. This study underscores CAB39's pivotal role in bladder cancer pathophysiology and its potential as a therapeutic target.