Long non-coding RNA HOXA-AS2 promotes the migration, invasion and stemness of bladder cancer via regulating miR-125b/Smad2 axis

Long non-coding RNA HOXA-AS2 (HOXA cluster antisense RNA 2) has been reported to function as an oncogene in different types of cancers including breast cancer, liver cancer, gastric cancer and colorectal cancer, etc. However, its role in the development and progression of bladder cancer remains unknown. This study aimed to examine the expression of HOXA-AS2 in bladder cancer, to explore its role in the migration, invasion and stemness of bladder cancer cells and to further identify the potential downstream target miRNAs of HOXA-AS2 in this type of cancer. Our results firstly demonstrated the upregulation of HOXA-AS2 in both bladder cancer cells and clinical bladder tumors. Such upregulation was also positively correlated with the advanced stage, invasion and lymph node metastasis of bladder cancer as well as the expression of cancer stem cell marker OCT4 in patients. After knockdown of HOXA-AS2 in bladder cancer 5637 and T24 cells, the migration, invasion and stemness of cancer cells were significantly inhibited, indicating the capability of HOXA-AS2 to promote the migration, invasion and stemness of bladder cancer cells. Knockdown of HOXA-AS2 also suppressed in vivo tumor growth in the nude mice. Furthermore, this study also identified miR-125b as a downstream target of HOXA-AS2 and revealed the downregulation of miR-125b by HOXA-AS2 as well as the involvement of HOXA-AS2/miR-125b/Smad2 interactions in the functional role of HOXA-AS2 in mediating the migration, invasion and stemness of bladder cancer cells. Together, our findings suggest that HOXA-AS2 might be a potential biomarker and target for the diagnosis, monitoring and treatment of bladder cancer.