Objective: To investigate the expression of microRNA-21 (mir-21) in invasive ductal carcinoma (IDC) of the breast and its association with phosphatase and tensin homologue deleted from chromosome (PTEN)-10 protein expression and the clinicopathologic features of IDC.
Methods: Specimens of IDC and normal tissues more than 5 cm away from the tumor tissues were collected from 40 IDC patients, all female, aged 53 (35-77). Stem-loop real-time RT-PCR was used to examine the mir-21 expression. Immunohistochemistry was used to examine the PTEN protein expression in the tumor tissue. The association of mir-21 expression with the PTEN expression and the clinicopathologic features of the breast IDC were analyzed.
Results: Compared with the nontumor control samples, the median (M) of relative expression of mir-21 (2(-DeltadeltaCt)) was 5.770 (25th-75th percentile, 3.605-7.255) in the tumor samples, significantly higher than that of the nontumor control samples (set at 1.000, P<0.001). Reduced PTEN protein expression was seen in 45% (18/22) of all cases. The expression of mir-21 was higher in the group of reduced PTEN expression (with an M of 6.800) than in the group of high PTEN expression (with an M of 4.850, P=0.013). The up-regulated expression of mir-21 was positively correlated with the TNM clinical stage, lymph node positivity, and proliferation index (P=0.021, 0.010, and 0.030 respectively).
Conclusion: mir-21 plays an important role in the development and progression of breast cancer. PTEN is possibly one of the targets of mir-21.