Potential new therapeutics for Waldenstrom's macroglobulinemia.

Thalidomide the first commercially available immune modulatory drug (IMiD), has activity in the treatment of Waldenstrom's macroglobulinemia (WM), as well as multiple myeloma, myelodysplastic syndrome, myelofibrosis with myeloid metaplasia, chronic lymphocytic leukemia (CLL), and B-cell lymphomas. Although its molecular mechanisms of action have not yet been elucidated, thalidomide and the IMiDs affect a variety of cytokines and inflammatory mediators including tumor necrosis factor-alpha (TNFalpha), interleukin (IL)-1beta, interferon gamma (IFNgamma), IL-6, IL-10, IL-12, and COX-2 and angiogenesis factors such as vascular endothelial growth factor (VEGF) and its receptor. The IMiDs also affect adhesion molecules such as ICAM-1, ICAM-2, and L-CAM, in addition to preferentially stimulating CD8 cells and expanding natural killer (NK) cell populations. Since most IMiDs share these properties, it would be expected that the second-generation IMiDs (REVIMID, ACTIMID) would have activity similar to thalidomide in WM with an improved safety profile. TNFalpha and angiogenesis most likely play a role in promoting the growth and development of WM. The selective cytokine inhibitory drugs (SelCIDs) are potent phosphodiesterase 4 (PDE-4) inhibitors that inhibit TNFalpha production and are highly antiangiogenic. In addition, inhibition of PDE-4 induces apoptosis in human CLL lymphocytes. It is therefore expected that the SelCIDs might have activity in Waldenstrom's tumors. Jun N-terminal kinase (JNK) is a component of signaling cascades that modulate apoptosis, the induction of an inflammatory response via the AP-1 pathway, and modulation of cellular proliferation. In a variety of tumors, including multiple myeloma, JNK is induced as part of a protective mechanism. It is hypothesized that inhibition of JNK activity might allow other chemotherapeutic agents to be more effective in a similar manner to corticosteroids. Work is in progress to evaluate this. Inhibitors of the E3 subunit of ubiquitin ligase may also selectively modulate the expression of receptors, growth factors, and transcription factors essential to the growth, survival, and spread of tumors. We hypothesize that the IMiDs, SelCIDs, JNK inhibitors, and ligase inhibitors will be the basis for a new nonchemotherapeutic approach to the treatment of WM and other related diseases.