The anti-proliferative effects of HDIs and CDDP against studied lung cancer cell lines. Inhibition of the proliferation of A549, NCI-H1563, NCI-H2170 cancer cells measured by the MTT assay (A). Anticancer activity of HDIs and CDDP occurs in order of treatment independent manner. A549 cell line was treated with both HDIs and CDDP (VPA + CDDP; SAHA + CDDP) in culture medium in doses of 1/4 IC50 + 1/4 IC50, 1/2 IC50 + 1/2 IC50, IC50 + IC50. Next, A549 cell line was treated with CDDP in culture medium and after 1 hour one of HDIs was added to medium containing CDDP (CDDP→VPA; CDDP→SAHA). Parallel, A549 cell line was treated with one of HDIs in medium and after 1 hour CDDP was added to medium containing VPA (VPA→CDDP; SAHA→CDDP). The same doses were used (B).