TP53 and myelodysplastic syndrome: If HMAs demethylate promoters that induce apoptosis by enhancing the activity of tumor-suppressor genes such as TP53, they may require the existence of at least 1 functional allele to perform their mechanism of action, a characteristic that is lacking in MDS-biTP53; without this function, the effect on hematopoiesis is minimal and survival, dismal.