MicroRNA-26a (miR-26a) functions as a tumor suppressor by regulating its direct target gene high mobility group AT-hook 1 (HMGA1). This study was aimed to investigate the associations of differential expression of miR-26a and HMGA1 with tumor progression and prognosis in urothelial bladder cancer (UBC) patients.

One hundred and twenty-six UBC patients were selected and quantitative real-time PCR was performed to detect the expression of miR-26a and HMGA1 mRNA in the respective tumors.

Our data showed the decreased expression of miR-26a and the increased expression of HMGA1 mRNA in UBC tissues compared with corresponding non-cancerous tissues (both P<0.001). Then, the expression levels of miR-26a in UBC tissues were negatively correlated with those of HMGA1 mRNA significantly (r=–0.72, P<0.001). In addition, UBC patients with combined miR-26a downregulation and HMGA1 upregulation (miR-26a-low/HMGA1-high) more frequently had advanced pathological stage (P<0.001) and high tumor grade (P<0.001). Moreover, miR-26a-low/HMGA1-high expression was associated with a significantly shortest disease-free survival (P<0.001) and overall survival (P<0.001) of all miR-26a/HMGA1 combined expression groups. Furthermore, multivariate analysis indicated that miR-26a/HMGA1 expression was an independent prognostic factor for both disease-free survival and overall survival (both P=0.001) in UBC patients.

Interaction between miR-26a and its target gene HMGA1 may contribute to the malignant progression of human UBC. Tumors with miR-26a downregulation in combination with high expression of HMGA1 showed a worse prognosis than the other tumors. Combined detection of their expression might be particularly helpful for surveillance of disease progression and treatment stratification.