SLC5A5 and carcinoma: Following the demonstration of mRNA expression of NIS by quantitative real-time PCR in melanoma and epithelial carcinoma cells, we next sought to examine the expression of NIS at the protein level in these cells, using the melanoma cell M14, hepatocarcinoma cell HepG2, and gastric carcinoma cell MKN-7 as representatives which displayed the most robust expression of NIS (Table 1).