Knockdown of TMEM45A overcomes multidrug resistance and epithelial-mesenchymal transition in human colorectal cancer cells through inhibition of TGF-β signalling pathway

Colorectal cancer (CRC), a leading cause of cancer death, has recently been known as the most prevalent malignancy worldwide. Although chemotherapy is an important therapeutic option for CRC patients, multidrug resistance (MDR) still remains a major cause of chemotherapy failure. Transmembrane protein 45A (TMEM45A) has been found highly expressed in various cancers, and is also proposed as an interesting biomarker for chemoresistance. However, the association between TMEM45A and MDR in CRC remains unclear. This study aimed to investigate the key role of TMEM45A in CRC by knockdown of its expression in 5-FU-resistant CRC cells (HCT-8/5-FU and SW480/5-FU) and their parental cells (HCT-8 and SW480). Data showed that TMEM45A was significantly up-regulated in HCT-8/5-FU and SW480/5-FU cells in comparison with their parental HCT-8 and SW480 cells. Knockdown of TMEM45A enhanced 5-FU sensitivity and 5-FU-induced apoptosis in HCT-8/5-FU and SW480/5-FU cells. It was also found that inhibition of TMEM45A increased the intracellular accumulation of Rhodamine-123 and down-regulated the expression of MDR1 in HCT-8/5-FU and SW480/5-FU cells. In addition, knockdown of TMEM45A suppressed migration and invasion of HCT-8/5-FU and SW480/5-FU cells. Furthermore, knockdown of TMEM45A not only attenuated MDR-enhanced epithelial-mesenchymal transition (EMT), but also suppressed MDR-enhanced activation of the TGF-beta signalling pathway in HCT-8/5-FU and SW480/5-FU cells. Taken together, our study suggests that knockdown of TMEM45A can effectively overcome MDR and inhibit EMT via suppression of the TGF-beta signalling pathway in human CRC cells, and that targeting TMEM45A will be a potential strategy in the treatment of MDR in CRC.