More recently, Kularatne, et al. [165]) developed polycaprolactone polymer NPs associated with 4-phenylbutyric acid, an HDAC inhibitor, to enhance DOX-based therapy in CRC, while Busi, et al. [166] developed keratin NPs loaded with 9-hydroxystearic acid, another HDAC1 inhibitor, which induced cell cycle arrest and cell death in CRC lines. Here, HDAC9 is linked to colorectal carcinoma.