Abstract 3079: Targeted therapy for EBV-associated B-cell neoplasms

Epstein-Barr virus (EBV) is directly implicated in several B-cell lymphoid malignancies. EBV associated B-cell neoplasms occur in both organ and allogeneic hematopoietic stem cell transplantations due to immunosuppression in these patients to maintain the function of transplant. Treatment of these B-cell neoplasms is limited to reduction in immunosuppression and antineoplastic chemotherapy. EBV associated lymphomas are characterized by prominent activation of Nuclear Factor kappa (NF-kB) pathway and targeting this pathway establishes a rationale for therapeutic approach. The ubiquitin/proteasome signaling pathway plays an important role in regulation of NF-kB pathway. Bortezomib (BZ) is the first FDA approved proteasome inhibitor for treating both newly diagnosed and relapsed/refractory multiple myelomas, and mantle cell lymphomas. BZ acts through inhibition of the 26S proteasome, a large protease complex that degrade ubiquitinated proteins. BZ stabilizes various cellular proteins involved in cell cycle arrest and apoptosis including p21, p27, p53, and IkBα by inhibiting proteasome function. Stabilization of IkBα results in inhibition of NF-kB signaling pathway which promotes tumor cell survival, growth, and angiogenesis. The major limiting factor for long-term administration of BZ through intravenous or subcutaneous is risk of peripheral neuropathy. There is a need to develop bioavailable proteasome inhibitor with low toxicity profile to overcome this conundrum. Ixazomib is an investigational orally bioavailable proteasome inhibitor which inhibits the activity of the 20S catalytic core subunit of the proteasome and currently in clinical trials for patients with relapsed/refractory multiple myeloma. Here we report the first preclinical evaluation of oral proteasome inhibitor ixazomib growth inhibitory effects on EBV-infected B-lymphoblastoid cell lines Raji and Daudi. In these cell lines, treatment with Ixazomib significantly induced apoptosis dose dependently (10-50 nM), in association with poly (ADP-ribose) polymerase cleavage. Cell cycle analysis by flow cytometry showed that Ixazomib treatment induced G2/M arrest dose dependently with concomitant decreases in the percentage of cells in G0/G1 and S phases. Immunoblotting analysis revealed increase in p53 and p27 levels without significant change in the relative levels of p21. Mechanistically, ixazomib treatment resulted in accumulation of polyubiquitinated proteins including accumulation of phosphorylated IkBα as demonstrated by western blot analysis concomitant with significant reduction in NF-kB activity and subunit translocation to the nucleus. Altogether, our pre-clinical data indicate that ixazomib induces apoptosis in EBV-associated lymphoma cells by blocking NF-kB signaling cascade and support the rationale for testing ixazomib in patients with EBV-associated B-cell neoplasms. Citation Format: Siddhartha Ganuguly, Satyanarayana Alleboina, Sudhakiranmayi Kuravi, Joseph McGuirk, Ramesh Balusu. Targeted therapy for EBV-associated B-cell neoplasms. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3079.