Based on this background, in this study we investigated whether Valproic acid (VPA), a class I/IIa HDAC inhibitor that has been shown to inhibit HDAC2 [12], could influence the expression and the acetylation of PD-L1 and whether acetylation could affect its interaction with molecules such as TRAPPC4 and its localization on cell surface of pancreatic cancer cells. The gene discussed is HDAC9; the disease is familial pancreatic carcinoma.