To further determine if NCX1 was a contributing factor to the development of MM, we exposed 4 MM cell lines (RPMI8226, KMS11, U266, MM.1S) to KB-R7943, an inhibitor of reverse-mode NCX1, for 24 h, 48 h, 72 h and 96 h. This evidence concerns the gene SLC8A1 and Miyoshi myopathy.