MCT1 transporters are crucial for the trans-epithelial transport of bacterially-derived short chain fatty acids within the healthy human colon (1). In normal colonic tissue, MCT1 is located in the basolateral membranes of surface epithelial cells (2). However, MCT1 transporters also play a key role in lactate transport in tumour cells, although both increases (3) and decreases (4) in MCT1 abundance have been reported in colonic carcinoma. Our previous study showed significant regional differences in healthy colon MCT1 abundance (5), suggesting an explanation for these conflicting reports. This current study hence investigated MCT1 abundance changes in carcinoma tissue from different colonic regions. Immunolocalization studies were performed using microarray slides containing matching samples of carcinoma and normal resection tissue from the same patient. Tissue sample pairs were taken from either the ascending, transverse, descending or sigmoid colon. Immunoperoxidase staining was performed using an anti-MCT1 antibody and the extent of MCT1 staining scored. Overall, MCT1 staining was not significantly different between normal and carcinoma paired samples from ascending (NS, N=16, paired t-test), transverse (NS, N=7, paired t-test) or descending colon (NS, N=5, paired t-test). However, in sigmoid colon there was a significant five-fold increase in MCT1 staining in carcinoma compared to normal tissue (P<0.05, N=21, paired t-test). In conclusion, our data showed changes in MCT1 abundance observed in colonic carcinoma tissue compared to normal resection tissue were region-dependent. Future research is now required to establish if this finding is repeated for other transporters thought to be involved in colonic tumour metabolism (e.g. GLUT2).