Direct Inhibitory Effects of Lenalidomide on the Proliferation and VEGF Production of Non-Hodgkin Lymphoma Cells Are Associated with Increased SPARC Expression

Lenalidomide is an oral anti-angiogenic, anti-proliferative and immunomodulatory drug approved for the treatment of Low- or Intermediate-risk myelodysplastic syndrome associated with a del(5q) cytogenetic abnormality, and in combination with dexamethasone for previously treated multiple myeloma. Early clinical results suggest potential clinical efficacy in B-cell non-Hodgkin lymphoma (NHL). In this study, we investigated lenalidomide-mediated inhibition of cell proliferation and angiogenic factors in the following NHL subtypes: mantle cell lymphoma (MCL), diffuse large-B-cell lymphoma, and follicular lymphoma (FL). The effect of lenalidomide on these tumor cells was determined after 1–3 days of treatment by ³H-thymidine incorporation, Luminex-based microbead array, and real-time qRT-PCR. We also assessed the expression of tumor suppressor genes such as p21cip1 and secreted protein acidic and rich in cysteine (SPARC). We found that lenalidomide induced direct anti-proliferative effects on each NHL subtype, with MCL cells being the most sensitive. Pro-angiogenic factors such as vascular endothelial growth factor (VEGF) were expressed at a high level in all lymphoma cell lines. Lenalidomide inhibited VEGF production at much lower concentrations than required for anti-proliferative effects, particularly in MCL and FL cell lines. Addition of recombinant human VEGF or neutralizing anti-VEGF antibody had no effect on MCL cell proliferation, suggesting that these effects are independent. Mechanistic studies indicated that lenalidomide strongly increased the gene expression of the tumor suppressor genes p21cip1 and SPARC to varying degrees. Elevation of SPARC mRNA significantly correlated with both the anti-proliferative and the VEGF-suppressive effects of lenalidomide on MCL cells (p < 0.05). Transfection of tumor cells with SPARC siRNA led to significant resistance to lenalidomide suggesting that this effect is mediated at least in part through the up-regulation of SPARC. In conclusion, lenalidomide demonstrates anti-proliferative activity against multiple NHL cell subtypes with greatest potency against MCL. The potent anti-VEGF activity of lenalidomide supports the anti-angiogenic potential of the drug. Thus, lenalidomide-induced up-regulation of SPARC mRNA correlates with MCL sensitivity and may have biomarker potential.