Abstract 2578: Synthetic lethal approaches to aurora inhibition in aggressive B-cell non-Hodgkin lymphoma
Authors: Mahadevan Daruka , Morales Carla , Cooke Laurence , Pandey Manjari , Spier Catherine , Qi Wenqing 
Published: August 2015

Abstract
We explored synthetic lethality in the context of aurora inhibition with novel combination therapies for aggressive B-NHL. Aurora A and B are serine/threonine kinases and when amplified dysregulate the mitotic phase of the cell cycle. Pre-clinical and clinical evidence demonstrate that aurora inhibition has therapeutic benefit in aggressive B-NHL. Alisertib, an aurora inhibitor has single agent activity in B-NHL mouse xenograft tumors and clinical trials. Pre-clinical studies demonstrate Bruton's tyrosine kinase (BTK) is persistently expressed despite alisertib therapy. TMAs for DLBCL (S0313, S0515, N = 60) and MCL (S0213, S0601, N = 45) were generated to evaluate aurora A, B and BTK expression by IHC. We developed B-NHL cell lines resistant to alisertib to evaluate mechanisms of acute and chronic resistance and knock down of aurora A and B to evaluate Myc, Bcl2 and BTK expression. Mouse B-NHL xenograft models were conducted to demonstrate synthetic lethality of aurora plus BTK inhibition. We demonstrate synergistic inhibition of cell proliferation associated with apoptosis, particularly in ABC and double hit DLBCL and mantle cell lymphoma (MCL) cells. Ibrutinib completely inhibited BTK and AKT activity at 3.0μM without affecting BTK or AKT protein level in B-NHL cells that co-over-express Myc and Bcl-2. Aurora A and B knockdown show compromised oncogene expression. IHC indicated in DLBCL and MCL aurora B to be differentially over-expressed versus aurora A and BTK. Alisertib plus ibrutinib was highly synergistic in inhibiting cell proliferation and inducing apoptosis in B-NHL cells. Moreover, this effect was amplified with the addition of rituximab. Acute and chronic resistance to alisertib was due to ERK1/2 activation. Significantly greater apoptosis was induced in the triplet combination (alisertib + ibrutinib + rituximab) compared to doublet combinations (ibrutinib + rituximab or alisertib + ibrutinib or alisertib + rituximab). Mouse xenograft models of MCL (Granta-519) and double hit DLBCL (U2932) showed ibrutinib alone had no anti-B-NHL activity. Ibrutinib + alisertib lead to tumor growth inhibition (TGI) of ∼50% in MCL and ∼30% in DLBCL (p = 0.005). Interestingly, ibrutinib + rituximab lead to a TGI of ∼60% (p = 0.005) in both B-NHL mouse models. In contrast, triplet therapy with alisertib plus ibrutinib plus rituximab demonstrated a statistically significant tumor TGI of ∼70-90% (p = 0.005) in both B-NHL mouse models with an associated enhanced overall survival (&gt;70 days). Harvested tumors at the end of treatment(s) demonstrated target inhibition and increased apoptosis with triple therapy. Inhibition of BTK plus rituximab in the presence of aurora inhibition is synthetic lethal in B-NHL and warrant clinical trial evaluation.
Citation Format: Daruka Mahadevan, Carla Morales, Laurence Cooke, Manjari Pandey, Catherine Spier, Wenqing Qi. Synthetic lethal approaches to aurora inhibition in aggressive B-cell non-Hodgkin lymphoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2578. doi:10.1158/1538-7445.AM2015-2578