Comparison of interleukin-1 beta expression by in situ hybridization in monoclonal gammopathy of undetermined significance and multiple myeloma.

We investigated whether interleukin-1beta (IL-1beta) is differentially expressed in plasma cells from monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM) patients because IL-1beta appears to play a major role in the development of lytic bone lesions, the major clinical feature distinguishing MGUS from myeloma. In situ hybridization (ISH) for IL-1beta was performed using bone marrow aspirates from 51 MM, 7 smoldering MM, 21 MGUS, and 5 normal control samples. Using the ISH technique IL-1beta mRNA was detectable in the plasma cells from 49 of 51 patients with active myeloma and 7 of 7 patients with smoldering myeloma. In contrast, 5 of 21 patients with MGUS and 0 of 5 normal controls had detectable IL-1beta message. Bone lesions were present in 40 of the 51 MM patients analyzed, and all 40 patients had IL-1beta mRNA by ISH. These results show that greater than 95% of MM patients but less than 25% of MGUS patients are positive for IL-1beta production. In the future, continued follow-up of IL-1beta positive and negative MGUS patients should determine whether aberrant expression of plasma cell IL-1beta is predictive of those MGUS patients that will eventually progress to active myeloma.