MicroRNA-26a-5p as a potential predictive factor for determining the effectiveness of trastuzumab therapy in HER-2 positive breast cancer patients

BACKGROUND: Breast cancer (BC) is known as the most prevalent type of cancer among women. Trastuzumab, as an anticancer drug, has been used broadly in human epidermal growth factor receptor 2 (HER-2) positive (+) BC patients. Moreover, accumulating evidence has demonstrated that microRNAs is involved in the pathogenesis BC. Hence, we aimed to investigate the effect of trastuzumab on the expression levels of microRNA-26a in HER-2 positive BC patients. METHODS: This study was conducted among HER-2 + and HER-2 Negative (−) BC patients. Serum expression of microRNA-26a was detected by real-time PCR. Then, we assessed the correlations of microRNA-26a levels with multiple clinico-pathological characteristics of BC. RESULTS: In HER-2 + patients, the microRNA-26a expression significantly increased after treatment with Docetaxel/Trastuzumab in comparison to before the treatment levels (p.value = 0.01). However, this overexpression in HER-2-patients after treatment with Docetaxel was not significant compared to the levels before the treatment (p.value = 0.14). In addition, the expression of microRNA —26a has significantly increased in HER-2 + patients who were ≤48 years old and premenopausal after the treatment with Docetaxel/Trastuzumab when compared to the levels before the treatment (p.value = 0.039 vs. 0.031, respectively). Furthermore, there was a significant correlation between the expression of microRNA —26a and the tumor size, stage, estrogen receptor (ER) and progesterone receptor (PR) status in the HER-2 + group before and after the treatment (p.value = 0.043, 0.042, 0.049 and 0.034 respectively). CONCLUSIONS: Trastuzumab led to overexpression of microRNA-26a in HER-2 + BC patients. It seems that the detecting microRNA —26a expression levels, during or after the trastuzumab therapy could be a useful biomarker for monitoring the therapeutic response in HER-2 + BC patients. However, further studies on large populations of women with HER-2+ BC are needed to explore this possible novel biomarker, in more detail, within various clinical contexts.