SGN-30, a novel chimeric anti-CD30 antibody, induces cell cycle arrest and apoptosis in ALK+ anaplastic large cell lymphoma.

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Background. CD30 receptor, a member of the tumor necrosis factor (TNF) superfamily, is aberrantly overexpressed in a group of lymphoid neoplasms including Hodgkin lymphoma (HL), and anaplastic large cell lymphoma (ALCL), including anaplastic lymphoma kinase (ALK)+ and ALK- cases. SGN-30 is a recently described chimeric (human-mouse) anti-CD30 antibody that has been shown to inhibit cell proliferation in HL and ALK+ ALCL cell lines. However, the underlying mechanisms explaining the effects of SGN-30 on cell proliferation in CD30+ lymphoma cells are unknown. Methods. Two CD30+ cell lines, Karpas 299 (ALK+ ALCL), Mac2a (ALK-ALCL), and one CD30- cell line Jurkat (T-cell acute lymphoblastic leukemia) were used for this study. Cell viability was assessed 24 hours after incubation with the SGN-30 antibody at increasing concentrations (0, 5, 20, and 40 ng/ml) using trypan blue exclusion assay. Apoptotic cell death was assessed by, immunoflourescence (DAPI staining), and flow cytometry (Annexin V binding) methods. Expression levels of apoptosis-and cell cycle-related proteins were evaluated using Western blot analysis with specific antibodies. Results. The SGN-30 antibody significantly decreased the viability of Karpas 299 cells with marked cell death observed at a concentration of 20 ng/ml and 40 ng/ml. Cell death in Karpas 299 was associated with apoptotic morphology of tumor cells, a significant increase of Annexin V binding, downregulation of the anti-apoptotic proteins Bcl-xL, full length Mcl-1 and cFLIP, and upregulation of pro-apoptotic effectors including short-form Mcl-1, and cleaved Caspase 3. Moreover, treatment of Karpas 299 with increasing concentration of SGN-30 resulted in cell cycle arrest as shown by BrdU incorporation that was associated with upregulation of cyclin-dependent kinase inhibitors p21 and p14, increased levels of unphosphorylated RB protein and decreased Cyclin A levels. Using the SGN-30 antibody at a concentration of 40 ng/ml, no effect on cell viability was detected in Mac2a and Jurkat cells lines. No significant changes in cell cycle regulating proteins were observed in Mac2a or control Jurkat cells. Conclusion. The SGN-30 antibody induces cell cycle arrest and apoptosis in ALK+ALCL cells, but has little effect on ALK-ALCLs. A number of cell cycle and apoptotic proteins are modulated in ALK+ALCL cells after exposure to SGN-30.