Background: Breast cancer (BC) is a common malignancy with a high mortality rate. Malignant cell transformation is associated with metabolic changes. One group pf proteins that are affected are the monocarboxylate transporters (MCTs-SLC16A). The MCTs comprise 14 members, and they play an important role in the growth, proliferation, and metabolism of cancer cells by transporting monocarboxylates such as lactate, pyruvate and thyroid hormones. We aimed to evaluate the expression of MCT3 (SLC16A8), MCT8 (SLC16A2) and MCT9 (SLC16A9) genes in breast cancer samples, comparing to normal adjacent tissues.
Methods: Forty paired breast cancer tumor samples, the adjacent non-tumor and five healthy tissues were collected. Three cancer cell lines (MCF-7, MDA-MB-231, and SKBR3) were also analysed. The expression of SLC16A8, SLC16A2 and SLC16A9 were assessed using quantitative real-time PCR (qRT-PCR). The relationship between gene expression with the pathological features of the tumors, and the hormone receptors status [estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2)] of the patients tumors were also analyzed. Microarray data and survival analyses for each of the candidate genes was undertaken
Results: There was a significantly lower expression of the MCT3 gene in tumor samples compared to adjacent normal tissue and healthy samples (P-value < 0.05). There was a significant difference in the expression of all three candidate genes between the BC tissues and normal tissues, and for the, tissues with different hormone receptor status (ER, PR and HER2) and the molecular subtypes. Altered MCT8 and MCT9 gene expression was associated with a reduced survival
Conclusion: MCT3 expression is significantly downregulated in breast cancer tissue. MCT3 may represent a novel therapeutic target in breast cancer patients, or in some hormone receptor subgroups, such as HER2-negative or triple-negative.