Monocarboxylate transporters in breast cancer and adipose tissue are novel biomarkers and potential therapeutic targets.

Monocarboxylate transporters (MCTs) are transmembrane proteins that control the lactate metabolism and associated with poor prognosis in solid tumours including breast cancer (BC). This study aimed to evaluate the clinical and prognostic value of MCTs used by immunohistochemistry and quantum dots-based fluorescent imaging technique in BC and surrounding stroma with emphasis on the interaction between tumour and stroma. Moreover, the data from The Cancer Genome Atlas (TCGA) was analyzed to evaluate the association between MCTs mRNA expression and prognosis of breast cancer patients. Our study found that MCT1 overexpression was observed in hormone receptor-negative and high-proliferation subtypes. High expression of MCT1 and MCT4 in tumour tissues was associated with poor patient outcome; further the correlation between MCT1 expression and poor prognosis in breast cancer was further strengthened when combined with MCT4 overexpression in the adjacent adipose tissue. These results demonstrate that MCTs tend to play a role in the aggressive BC subtypes through the dynamic interaction between breast cancer cells and adipocytes, and developing therapeutics to block this interaction will be a promising strategy in cancer therapy.