HDAC9 and cancer: Despite the relatively low existing understanding of the mechanisms of action of HDACs and DNMTs inhibitors in the immune system, the promising results obtained in preclinical models have favored the recent development of several clinical trials testing combinations of anti-PD-L1/PD-1 or CTLA-4 therapies and HDAC or DNMTs inhibitors for the treatment of several types of cancers (https://clinicaltrials.gov).