To further demonstrate that TSA downregulates the USP promoter and therefore inhibits the expression of an active P-glycoprotein, we decided to include in this study three additional colon carcinoma cell lines: LS-174 T, Colo-320 and DLD-1 that express P-glycoprotein, as shown by Western blot analysis in Figure 5A. Figure 5B shows that these cell lines express the long 5′-UTR MDR1 mRNA and, furthermore, that TSA treatment decreased the levels of expression of the long 5′-UTR MDR1 mRNA in all of them. The gene discussed is ABCB1; the disease is colon carcinoma.