Gadolinium Containing Contrast Agent Promotes Multiple Myeloma Cell Growth: Implication for Clinical Use of MRI in Myeloma

Bone marrow infiltration by myeloma cells and osteolytic bone lesions are the major features of Multiple Myeloma. Magnetic Resonance Imaging (MRI) has been used in MM not only to image bone marrow (BM) and to identify lytic bone disease but to also evaluate therapeutic response and prognosis. Gadolinium (Gd)-based contrast agents are frequently used to enhance MRI resolution. We evaluated effect of the most common Gd-containing agent, Omniscan, on myeloma cells. We observed that Omniscan induced both time and dose dependent MM cell growth in vitro (8-20 fold increase relative to control). Importantly, the presence of BMSC enhanced the effect of Omniscan on growth of both MM cell lines and primary MM cells. However, Omniscan was not able to overcome cytotoxic effects of conventional and novel agents in MM. This growth promoting effects were not observed on normal BM stromal cells. Evaluating the molecular mechanism of action of Omniscan on MM cells, we observed time dependent ERK1/2 phosphorylation as well as reversal of growth promoting effects of Omniscan by specific inhibition of ERK signaling; however, Omniscan had no effect on STAT3 and AKT signaling pathways. Next, we investigated in vivo effect of Omniscan in a murine xenograft model of MM. Following detection of tumor, mice were treated with either iv Omniscan or PBS. Treatment with Omniscan significantly induced MM tumor growth compared to control mice (1042 ±243 mm³ vs 502 ±137 mm³ respectively; p=0.0001). Finally in autopsies in 8 MM patients with repeated exposure to Omniscan, we quantified gadolinium in various tissues using Inductively-coupled mass spectrometry. We observed massive quantities of gadolinium accumulation in tissues of these MM patients regardless of their renal function. These results, confirming both in vitro and in vivo growth promoting effects of Gd-containing contrast agent on MM, suggest the need for further analysis of the mechanism of its action on myeloma cells and careful analysis of its clinical impact in MM patients undergoing MRI evaluation.