HDAC9 and obesity due to melanocortin 4 receptor deficiency: In contrast, in mammary pads from naive animals or those without tumors, HFD reduced HDAC activity, supporting the notion that HFD and obesity increase acetylations of histones with changes in the epigenome.38 Similar to our findings, it was previously reported that HFD-induced HDAC activity plays important roles in epigenetic regulation of tumor suppressor genes involved in colorectal tumor growth and progression, including increased epithelial–mesenchymal transition and tumor inflammation in a xenograft model.39