Micro-RNA Expression Profiling in Malaysian Triple-Negative Breast Cancer Patients: Impact on Recurrence Prediction

Abstract

Background: Triple negative breast cancer (TNBC) is characterized by its biologic aggressiveness, worse prognosis and lack of therapeutic targets. Due to high probability of tumor recurrence and also due to lack of available targeted therapies, TNBC patients are treated with standard chemotherapy using TAC [taxane (T), adriamycin (A) and cytoxan (C)] chemotherapy regimen. However, TNBC patients present significant interindividual differences of treatment efficacy. Drug resistance and recurrence remains major clinical obstacles to successful treatment in many TNBC patients. This warrants the need for early identification of TNBC patients who are likely to be chemosensitive and those who have high recurrence risk. TNBC may have specific molecular features that could be possible targets for new biologic targeted drugs. microRNAs (miRNAs) which are aberrantly expressed in tumors, can target and modulate key genes involved in TNBC chemotherapy. Aberrant microRNA expression is strongly implicated in anticancer drug resistance phenotype and hence, miRNAs appear to be promising candidates for response and recurrence prediction. Aim: To investigate the expression profile of few candidate miRNAs (miR-21, miR-27b, miR-34a, miR-182, miR-200c and miR-451) in tumourous and nontumourous tissues in Malaysian TNBC patients and their utility as predictive markers of recurrence in TNBC patients. Methods: Malaysian TNBC patients who had undergone TAC chemotherapy regimen at Hospital Universiti Sains Malaysia were identified and the clinicopathological variables were recorded. Total RNA from cancerous and adjacent noncancerous tissues of FFPE samples from 41 patients were isolated, transcribed and preamplified. The expression of selected miRNAs (miR-21, miR-27b, miR-34a, miR-182, miR-200c and miR-451) were quantified using quantitative real-time PCR (qRT-PCR). The miRNAs expression was categorized into two groups based on upregulation and downregulation. The disease outcome of the patients were evaluated after completion of chemotherapy. Disease-free survival (DFS) analysis using Kaplan-Meier method followed by univariate and multivariate Cox's regression analysis were performed to investigate the impact of these candidate miRNAs on recurrence prediction. Results: The relative expressions of miR-27b and miR-451 were found to be significantly lower in cancerous as compared with normal adjacent tissues of TNBC patients. Multivariate Cox's regression analysis demonstrated that medullary and metaplastic tumor subtypes and positive axillary lymph nodes significantly increased the risk of recurrence in TNBC patients. Downregulated expression of miR-21 and upregulated expression of miR-182 were found to be associated with risk of recurrence in TNBC patients. Conclusion: Tumor subtypes, positive axillary lymph nodes as well as expression profiles of miR-21 and miR-182 could be useful as predictive biomarkers of recurrence in TNBC patients.