Expression Analysis of miR-29b in Malignant and Benign Breast Tumors: A Promising Prognostic Biomarker for Invasive Ductal Carcinoma With a Possible Histotype-Related Expression Status

Abstract Background Aberrations in microRNA levels seem to provide valuable information regarding breast cancer prognosis and therapy. In this study, we sought to analyze miR-29b expression in breast tumors and thus explore its clinical value. Materials and Methods One hundred twenty-one malignant and 56 benign breast tissue specimens were collected and subjected to extraction of total RNA, which was polyadenylated and reverse transcribed to cDNA. Subsequently, a highly sensitive quantitative real-time polymerase chain reaction protocol was developed and miR-29b levels, estimated via the comparative C T method, were finally subjected to comprehensive statistical analysis. Results MiR-29b levels did not differ between the analyzed benign and malignant breast tissue specimens, but were found to be significantly ( P  = .010) decreased in invasive ductal adenocarcinomas compared with their lobular counterparts, albeit receiver operating characteristics curve analysis did not verify the latter correlation. Additionally, miR-29b expression was elevated in samples with positive estrogen receptor status ( P  = .021) in the overall population, whereas it was negatively correlated ( P  = .035) with primary tumor staging in the ductal subset and increased in poorly-differentiated tumors of lobular origin ( P  = .041). Furthermore, Kaplan–Meier and Cox regression analyses showed that patients with ductal carcinoma and elevated miR-29b levels had a significantly longer disease-free survival ( P  = .010) and a lower risk to relapse (hazard ratio = 0.35, 95% confidence interval, 0.15-0.81; P  = .014). Conclusion Our results provide evidence that miR-29b levels constitute a promising biomarker of favorable prognosis for patients with invasive ductal breast carcinoma and imply that its expression status might be affected by the histological origin of breast malignancy.