a The expression of ITGA6 in plasma cell dyscrasias (MGUS, SMM, MM and PCL) and PCs of healthy donor (NC). The expression level of ITGA6 in patients with MGUS, SMM and MM was lower than that of healthy donors. ITGA6 level in PCL was lower than that of MM patients. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001, ns not significant versus NC. b Kaplan–Meier plots indicating the prognostic relevance of ITGA6 expression in the event-free and overall survival of MM patients (GSE24080 and GSE4581).