It has been reported that CAL-101 blocks Erk1/2 phosphorylation in INA-6 human myeloma cells [23], which is consistent with our results with X-370 (Figure 3) and CAL101 in Raji and SU-DHL-6 cells (Figure S6), suggesting that PI3Kδ acts upstream of Erk1/2 in some cell types. The gene discussed is MAPK3; the disease is plasma cell myeloma.