Tumor immunotherapy has revolutionized cancer treatment, particularly through the use of immune checkpoint inhibitors targeting the PD-L1/PD-1 axis. While PD-L1 expression on tumor cells has been established as a predictive biomarker for therapeutic response, emerging evidence highlights the significance of PD-L1 expression on myeloid cells in the periphery and in the tumor microenvironment (TME). This study investigates the effects of the selective HDAC6 inhibitor ITF3756 on PD-L1 expression and on the immune functionality of monocytes stimulated with the pro-inflammatory cytokine TNF-α.