HDAC9 and colonic neoplasm: Furthermore, the high expression of SCFAs receptors in immune cells has indicated that SCFAs affect the expansion and production of Treg cells through the inhibition of SCFA-GPCR or HDAC, participating in intestinal immune regulation, and regulating and colon cancer development (El Kaoutari et al., 2013; Johansson et al., 2015).