CSNK2B and monoclonal gammopathy: To investigate the expression of CK2 in bortezomib-sensitive B cell tumors, the expression of CK2α (catalytic subunit) and CK2β (regulatory subunit) proteins were examined by immunohistochemistry in lymph node biopsies from MCL patients (n = 21), in normal lymphoid tissues (tonsils or reactive lymph nodes)(n = 3), in bone marrow biopsies obtained from monoclonal gammopathy of undetermined significance (MGUS) (n = 5) and MM patients (n = 17).