Melphalan, as an alkylating drug, is responsible for an increase in the level of the DNA double break marker (γH2AX), induces the phosphorylation of checkpoint kinase 1 (CHK-1) and checkpoint kinase 2 (CHK-2) in MM cells (RPMI8226 and MM1.S) [31], and leads to apoptosis through the formation of intra- and interstitial DNA cross-bonds [32]. Here, CHEK1 is linked to Miyoshi myopathy.