AFP and neoplasm: For example, replacing the constitutive CMV promoter with either the liver-specific human α anti-trypsin (hAAT) promoter, the muscle-specific smooth muscle 22 (SM22) promoter, or the tumour-specific α-fetoprotein (AFP) promoter led to tissue-specific transgene expression in liver, muscle cells, and AFP-positive carcinoma cells, respectively [77,78].