CA9 and breast cancer: By use of an in situ proximity ligation assay (PLA), Ames et al. could recently demonstrate a direct interaction between MCT1, MCT4 and CAIX in tissue samples of human breast cancer patients.189 Interestingly, the number of PLA signals increased with higher tumour grade, indicating that the number of MCT1/4–CAIX transport metabolons increases during tumour progression.189