SPHK1 and chronic myelogenous leukemia, BCR-ABL1 positive: To gain deeper insight into the impact of sphingolipid metabolism on CML cells, we performed RNA-seq analysis of K562 cells with shRNA-mediated knockdown of SPHK1. The volcano plot of differentially expressed genes (DEGs) showed 112 up-regulated and 122 down-regulated genes, with SPHK1 showing the most statistically significant difference among all DEGs (Fig. 4A).