Immunohistochemical detection of MCT, LDH isoforms, and COx in breast cancer cell line MDA-MB-231. LDH isoforms, MCT2, and MCT4 were colocalized with mitochondrial protein marker COx (A, B, C). MCT 1 was not expressed in MDA-MB-231 cells. The thickness of the optical section ∼1 μm, scale bar = 10 μm.