PRDM9 and cancer: The U.S Food and Drug Administration (FDA) has approved the epigenetic drugs (epi-drugs); DNA methyltransferase inhibitors (DNMTi), histone deacetylase inhibitors (HDACi) and histone methyltransferase inhibitors (HMTi) for the treatment of several cancers including myelodysplastic syndromes, leukemia, lymphoma, multiple myeloma and epithelioid sarcoma [16–18]).