Lenalidomide Displays Direct Anti-Non-Hodgkin’s Lymphoma (NHL) Cell Activity in Association with Enhanced SPARC Expression but Independent of Its Ability to Strongly Inhibit NHL Cell VEGF Production In Vitro.

Lenalidomide is an oral anti-angiogenic, anti-proliferative and immunomodulatory drug that is approved for the treatment of transfusion-dependent patients with anemia due to low- or intermediate-1-risk MDS associated with a del 5q cytogenetic abnormality with or without additional cytogenetic abnormalities, and in combination with dexamethasone for the treatment of previously treated multiple myeloma patients. Encouraging early results suggest a potential for clinical efficacy in B cell non-Hodgkin’s lymphoma (NHL). We have previously shown that lenalidomide can directly inhibit the proliferation of NHL cells and synergize with dexamethasone in inducing cell cycle arrest at the G1/S transition leading to caspase activation and apoptosis. In this study we have studied the potential for lenalidomide mediated growth inhibition, apoptosis and inhibition of angiogenic factors in NHL. We have assessed proliferation, expression of p21 and SPARC tumor suppressor genes and the production of the angiogenic factor vascular endothelial growth factor (VEGF) in six established NHL cells lines in vitro. The effect of lenalidomide on NHL cells was determined after 1–3 days using ³H-thymidine incorporation, microbead array and real time PCR. We found that lenalidomide displays anti-proliferative effects on Namalwa, Jeko-1 and Rec-1 cells when used alone and in combination with dexamethasone. However, several NHL cell lines, such as Granta-519, DB, and JVM-2, appear to be resistant. We also found that lenalidomide strongly inhibited VEGF production (but not mRNA levels) by the three sensitive lines (but not the three resistant lines) at much lower concentrations than required for inhibitory effects on proliferation. Excess recombinant human VEGF or neutralizing anti-VEGF antibody had no effect on Rec-1 proliferation suggesting that there is no connection between these two effects. Lenalidomide strongly increased the expression of tumor suppressor genes, such as p21^cip/kip and SPARC (secreted protein acidic and rich in cysteine). In particular, elevation of SPARC mRNA correlated with the anti-proliferative effect of lenalidomide and was not seen in the resistant cells, whereas elevated p21 was observed in both sensitive and resistant (DB) cells. The effect of SPARC gene silencing on lenalidomide-induced effects is being assessed in siRNA studies. In conclusion, lenalidomide demonstrates anti-proliferative activity against certain sensitive NHL cells, particularly in combination with dexamethasone. Potent anti-VEGF activity of lenalidomide appears to be independent of proliferation and supports its anti-angiogenic potential. Lenalidomide-induced up-regulation of SPARC mRNA appears to correlate with sensitivity and may have biomarker potential in NHL.