These results together suggested that signaling pathways through CD44 and ALK4 differentially regulate the spheroid formation and ALDHbright CICs in MM cells, and that possible cooperation exists where HA–CD44 axis may locate upstream of the Activin-A–Alk4 axis in tumor formation (Supplemental Fig. S8). The gene discussed is ACVR1B; the disease is Miyoshi myopathy.