HDAC9 and neoplasm: Therefore, we hypothesized that a curcumin derivative CU4c (CU4c) with ethyl groups at the side chains (Figure 1) would exhibit HDAC-inhibitory and anti-tumor activities against non-small cell lung cancer (NSCLC) cells because CU4c presented more potent HDAC inhibition (87%) than CU (67%) [26].