Cell specificity of 4E was tested in H1299 cells, a lung carcinoma cell line. Of the seven ADHs, only ADH1B is known to be expressed in lungs (Smith et al., 1971), although data from our lab suggests that neither ADH1B nor ADH4 are expressed in these cells. However, the transfected minimal promoters of both ADH4 and ADH1B did show activity above the vector-only background. Therefore, we tested the enhancer activity of 4E upstream of ADH4, ADH1B and SV40 promoters. No enhancer activity was detected with any of the three promoters (Table 2). These results suggest that 4E shows cellular specificity.
