Its proposed mode of action in combination therapies is that inhibition of HDAC activity would have synergistic effects with cancer chemotherapy by at least 2 mechanisms: first, by tilting the balance between oncogenes and tumor suppressor genes in favor of tumor suppressors, and second, by altering the sensitivity to DNA‐damaging chemotherapy through modulation of chromatin structure.8, 11. This evidence concerns the gene HDAC9 and cancer.