Serum Levels of OPG and MIP-1α in Untreated Multiple Myeloma Patients. Correlations with Staging, Survival and Bone Disease.

Abstract

Cytokines, such as MIP-1a (macrophage inhibiting factor) and OPG (osteoprotegerin) are assumed to play a role in MM disease biology and bone disease, by mechanisms that are still under investigation. MIP-1a is constitutively secreted by myeloma cells, plays a possible role in the development of MM bone lesions, enhance MM cell adhesion to stromal cells and its serum levels have been recently related to survival in MM. OPG is a soluble decoy receptor which acts as a soluble receptor antagonist that prevents osteoclasts activation and the development of bone disease. Reported findings on serum OPG levels in MM patients are controversial as well as its possible role in the biology of the disease. In order to investigate the possible relationship of MIP-1a and OPG levels in MM patients with prognosis and bone disease, we determined by ELISA serum MIP-1a and OPG levels in 20 MGUS, 82 MM patients and 27 healthy individuals (HI). Both cytokines were determined by ELISA (R&D, Quantikine, USA) in frozen sera collected at dignosis, before treatment. The median age of MM patients was 69 years (44–84) and 50% were males. MM patients' stage was as follows: 23 stage I, 28 stage II, 31 stage III according to Durie-Salmon staging system and 27 stage I, 17 stage II, 35 stage III according to the International Scoring System (ISS). In HI median MIP-1a was 28 pg/ml (15–54) and median OPG 1600 pg/ml (450–4600). In subjects with MGUS, median MIP-1a was 34 pg/ml (17–58) and median OPG 2300 pg/ml (820–6200). In MM patients, median pretreatment serum MIP-1a was 32 pg/ml (16–100) and OPG 3000 pg/ml (820–25000). No statistical significant difference was observed between HI, MGUS and MM patients with regard to MIP-1a levels but for OPG levels differences between HI and MM patients and between MGUS and MM patients were both significant (0.01 and 0.05 respectively). No relationship was found between MIP-1a or OPG levels and bone disease. However, there was a trend for longer survival in patients with MIP-1a or OPG levels lower than median (5-year overall survival 60 ± 12 vs 38 ± 14, p=0.08 and 66 ± 13 vs 29 ± 13, p=0.07 respectively). In addition MIP-1a levels were correlated with ISS stage: MIP-1a levels were 28.3±11.3 in ISS stage 1, 29.8±11.1 in ISS stage 2, 39±19.2 in ISS stage 3 (p=0.02). In conclusion, in our experience serum OPG levels are higher in MM patients than in MGUS or HI, MIP-1a levels are correlated with the ISS stage and both high serum MIP-1a and OPG levels at diagnosis are related with a shorter survival.