In the fifteen sensitive tumor cell lines, a weak constitutive expression of IFNA1 in the absence of the virus was found in six tumor cell lines (Meso35, 36, 37, 56, 34 and 122) and was increased in the presence of MV in four of these (Meso35, 36, 34 and 122). This evidence concerns the gene IFNA1 and neoplasm.