Expression of tumor suppressors miR-195 and let-7a as potential biomarkers of invasive breast cancer

Marcia M. Marques, Adriane F. Evangelista, Taciane Macedo, René Aloisio da Costa Vieira, Cristovam Scapulatempo-Neto, Rui M. Reis, André L. Carvalho, Ismael Dale Cotrim Guerreiro da Silva

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the posttranscriptional level. Some miRNAs, including let-7a and miR-195, have been described as tumor suppressors. However, the roles of these microRNAs in breast cancer progression remain controversial. The aim of this study is to evaluate miR-195 and let-7a expression as potential biomarkers of invasive breast cancer. In the present study, 200 individuals were separated into three groups: (i) 72 women constituting the control group who were selected according to rigorous and well-established criteria; (ii) 56 patients with benign breast tumors; and (iii) 72 patients with malignant breast cancers of different clinical stages. The miR-195 and let-7a expression levels in serum were evaluated by real-time PCR. The results were assessed alone and in combination, and the analysis included an estimation of sensitivity and specificity in ROC curves. Compared with the benign and control groups, both microRNAs were downregulated in the malignant breast cancer patient group. Compared with the malignant group, the combination of both biomarkers in the control and benign groups showed good sensitivity and specificity in the serum with AUCs of 0.75 and 0.72, respectively. The biomarker combination for the control group versus the malignant group exhibited a better sensitivity and specificity than for the benign group versus the malignant group. These findings support the evidence that the analysis of miR-195 and let-7a can be used as a non-invasive biomarker for breast cancer detection.