HDAC9 and neoplasm: Similarly, the inhibition of histone deacetylase (HDAC), highly involved in lung cancer [26], by means of SAHA (Fig. 5d) and of DNA methyltransferase by means of 5-AZA (Fig. 5e) did not modify caspase-4-induced cell proliferation, implying that caspase-4 is unlikely to be involved in epigenetic modulation/s that lead to tumor cell proliferation [27].