Higher miR-21 expression in invasive breast carcinomas is associated with positive estrogen and progesterone receptor status in patients from Serbia.

MicroRNAs play essential role in breast carcinoma progression and invasion. Our principal goals were to assess clinicopathological and prognostic correlations of microRNA-21 (miR-21) expression levels in a group of 39 Serbian breast cancer patients with invasive lobular (ILC), ductal (IDC), or mixed (ILC-IDC) breast carcinomas and in order to discover the role of miR-21 in potential novel form of stratification of the patients with different estrogen receptor (ER) and progesterone receptor (PR) status. MiR-21 expression levels were measured by stem-loop real-time RT-PCR using TaqMan technology. ER, PR, human epidermal growth factor 2 receptor (Her-2), and proliferative index (Ki-67) were evaluated by immunohistochemistry. MiR-21 levels do not vary among ILC, IDC, and ILC-IDC subgroups. MiR-21 expression levels varied significantly in the age, tumor size, Ki-67, and different grade (p = 0.030, p = 0.036, p = 0.027 and p = 0.032, respectively) subgroups. ER+ and PR+ showed higher miR-21 levels than their negative receptor status paired groups ER- and PR- with p = 0.012 and p = 0.018, respectively. MiR-21 positively correlated with ER and PR status (p = 0.018, ρ = 0.379 and p = 0.034, ρ = 0.345, respectively). Our findings suggest that miR-21 emulates transitional form of expression and that the levels of expression might be useful for stratification of the patients with different receptor status with the purpose to seek for new therapy approaches especially for the patients with the lack of response to conventional endocrine therapy.