MCAM and nasopharyngeal carcinoma: For testing the hypothesis that huMETCAM/MUC18 expression might suppress the tumorigenesis of the NPC cells, we used a biochemical method to increase the expression of huMETCAM/MUC18 by transfecting the NPC-TW01 cells with the huMETCAM/MUC18 cDNA via a lipofection reagent, and we isolated the G418-resistant (G418R) clones that expressed different levels of the protein.