5-Azacytidine (also known as 5-AzaC), a compound belonging to a class of cytosine analogues, is a DNA methyl transferase (DNMT) inhibitor that exerts potent cytotoxicity against multiple myeloma (MM) cells, including MM.1S, MM.1R, RPMI-8266, RPMI-LR5, RPMI-Dox40 and Patient-derived MM, with the half maximal inhibition concentration IC50 values of 1.5 μmol/L, 0.7 μmol/L, 1.1 μmol/L, 2.5 μmol/L, 3.2 μmol/L and 1.5 μmol/L respectively].