The expression of monocarboxylate transporter 4 (MCT4) in head and neck normal tissues, head and neck cancers, and human oral squamous cell lines. (A) Immunohistochemistry analysis of MCT4 in head and neck normal tissue (a) and head and neck cancer (HNC) (b). Scale Bar = 200 μm. (B) Scatterplot of the MCT4-positive areas in the head and neck normal tissues (n = 11) and head and neck squamous cell carcinoma (HNSCC) (n = 70). Error bars: mean ± standard deviation (SD). There was a significantly increased expression of MCT4 in the HNSCC samples (p < 0.0001). (C) Expression of MCT4 in human oral squamous cell carcinoma cell lines (HSC-2, -3, -4; SAS, OSC-19) and a human breast cancer cell line (MCF7) analyzed by western blotting.