The association between markers of tumour cell metabolism, the tumour microenvironment and outcomes in patients with colorectal cancer.

Tumour cell anaerobic metabolism has been reported to be a prognostic factor in colorectal cancer. The present study investigated the association between monocarboxylate transporter (MCT) 1, MCT 2, lactate dehydrogenase (LDH) 1 and LDH 5, the tumour microenvironment, and outcome in patients with colorectal cancer. A cohort of 150 patients with stage I-III CRC were utilised to assess tumour cell expression of MCT-1, MCT-2, LDH-1 and LDH-5 by immunohistochemistry. Expression levels were dichotomised and associations with tumour factors, the tumour microenvironment and survival analysed. Nuclear LDH-5 associates with poor prognosis (HR 1.68 95% CI 0.99-2.84, p = 0.050) and trends toward increased tumour stroma percentage (TSP, p = 0.125). Cytoplasmic MCT-2 also trends toward increased TSP (p = 0.081). When combined into a single score; nuclear LDH-5 + TSP significantly associated with decreased survival independent of stage (HR 2.61 95% CI 1.27-5.35, p = 0.009), increased tumour budding (p = 0.002) and decreased stromal T-lymphocytes (p = 0.014). Similarly, cytoplasmic MCT-2 + TSP significantly associated with decreased survival (HR 2.32 95% CI 1.31-4.11, p = 0.003), decreased necrosis (p = 0.039), and increased tumour budding (p = 0.004). The present study reports that the combination of TSP and nuclear LDH-5 was significantly associated with survival, increased tumour budding, and decreased stromal T-lymphocytes. This supports the hypothesis that increased stromal invasion promotes tumour progression via modulation of tumour metabolism. Moreover, MCT-2 and LDH-5 may provide promising therapeutic targets for patients with stromal-rich CRC.