Thus while the relatively poor solubility and high doses of tubacin needed for in vitro and in vivo responses have limited enthusiasm for advancing tubacin as a therapeutic for humans, the tumor suppressive activities described here suggest that tubacin, or drugs related to tubacin that retain both its HDAC6-dependent and HDAC6-independent activities, may be potent anti-cancer agents. This evidence concerns the gene HDAC6 and neoplasm.