Isoflurane promotes epithelial-to-mesenchymal transition and metastasis of bladder cancer cells through HIF-1α-β-catenin/Notch1 pathways

Aims: Epithelial-to-mesenchymal transition (EMT) facilitates cell migration and invasion, and contributes to metastasis in bladder cancer. Within the perioperative period, anesthetic such as isoflurane have been found to affect cancer prognosis. In the study, we reported the tumor-promoting effect of isoflurane in bladder cancer. Materials and Methods: Human bladder cancer cell lines T24 and BIU-87 were exposed to isoflurane at different concentrations. The immunofluorescent staining of Ki67, Annexin V-FITC/PI staining, Transwell invasion assays and wound-healing assays were performed to assess cell proliferation, apoptosis, invasion and migration. Expressions of EMT markers (E-cadherin, N-cadherin and Vimentin) and metastatic markers (Snail-1, Slug-1 and MMP-2/9) were determined by immunoblotting. Orthotopic tumor models and mice given tail vein injection of T24 cells were developed with or without 4-h exposure to 2% isoflurane. Key findings: We found isoflurane promoted bladder cancer cell proliferation, invasion and migration but reduce apoptosis in a concentration-dependent manner. In addition, isoflurane was shown to increase HIF-1 alpha and its nuclear accumulation in bladder cancer cells. HIF-1 alpha knockdown inhibited bladder cancer cell proliferation and delayed EMT, which was reversed in the presence of 4-h exposure to 2% isoflurane. Likewise, we found isoflurane modulated beta-catenin/Notch1 pathways via HIF-1 alpha. In vivo studies showed that isoflurane exposure accelerated formation of orthotopic bladder tumor and promoted hepatic metastases from carcinoma of the bladder. Significance: Taken together, our study demonstrates that a frequently used anesthetic can exert a protumorigenic effect on bladder cancer. Isoflurane may serve as an important contributory factor to high recurrence following surgery.