PGP and neoplasm: In that sense, we have demonstrated that TSA markedly reduced Pgp expression in the L1210R drug-resistant murine cell line [20] and “sensitized” these cells to daunomycin [26,27], as shown in Figure 1C, where TSA treatment increases DNM accumulation in L1210R cells, suggesting that iHDACs might have a therapeutic potential against chemoresistant tumours.