Abstract C144: Treatment with β-catenin antagonist BC2059 exhibits single agent efficacy and exerts superior activity with tyrosine kinase inhibitor (TKI) or histone deacetylase (HDAC) inhibitor against human AML, CML, and myeloproliferative neoplasm (MPN) progenitor cells.
Authors: Fiskus Warren , Smith Jacqueline , Mudunuru Uma , Hembruff Stacey , Reyes Ruben , Abhyankar Sunil , McGuirk Joseph , Aljitawi Omar , Ganguly Siddhartha , Horrigan Stephen , Sharma Sunil , Bhalla Kapil N. 
Published: June 2012

The canonical WNT-β-catenin signaling is essential to the cellular processes of self-renewal and growth, as well as required for self-renewal of leukemia stem. The multi-protein degradation complex for β-catenin is often inactivated in transformed hematopoietic progenitor cells. This results in the preservation, nuclear translocation and interaction of β-catenin with the T-cell factor (TCF)/lymphoid enhancer factor (LEF) transcription factor, which regulates the expression of genes such as cyclin D1, MYC and survivin. BC2059 (β-Cat Pharmaceuticals) is a potent small molecule, anthraquinone oxime-analog inhibitor of the WNT-β-catenin pathway. Treatment with BC2059 mediates the degradation and attenuated levels of β-catenin. In the present studies, we determined the activity of BC2059 in human cultured and primary AML, CML and advanced MPN versus normal cells. Exposure to 50 to 100 nM of BC2059 induced cell cycle G1 phase accumulation and apoptosis (40 to 80%) of the cultured AML cells (HL-60 and OCI-AML3), MPN HEL92.1.7 (HEL) and UKE1 cells expressing the mutant JAK2V617F, as well as of the CML K562 and LAMA-84 cells expressing BCR-ABL. BC2059 treatment also induced apoptosis of CD34+ primary MPN cells from patients with advanced MPN expressing mutant JAK2, as well as of primary CD34+ AML and CML progenitor cells. In contrast, BC2059 did not induce significant apoptosis of normal CD34+ progenitor cells. Exposure to BC2059 attenuated both β-catenin protein levels (significantly restored by co-treatment with the proteasome inhibitor) and the activity of the LEF1/TCF4 transcription factor, associated with reduced levels of cyclin D1, MYC and survivin in the cell lysates of BC2059-treated AML, CML and MPN cells. Following the tail vein infusion of HEL cells and establishment of MPN, NOD-SCID mice were treated with 15 or 20 mg/kg of BC2059 administered b.i.w for three weeks via the tail vein. As compared to the control, BC2059-treated mice demonstrated significantly improved survival (p &lt;0.001). Next, we examined the effects of co-treatment with BC2059 (20 to 50 nM) and JAK2-targeted TKI TG101209 (TG) (200–1000 nM) or BCR-ABL-targeted TKI nilotinib (10–20 nM) against MPN or CML cells, respectively. As compared to treatment with each agent alone, co-treatment with BC2059 and TG synergistically induced apoptosis of HEL and primary CD34+ MPN cells. Additionally, co-treatment with BC2059 and nilotinib induced synergistic apoptosis of K562 and primary CML progenitor cells. Further, combined treatment with BC2059 and the HDAC inhibitor panobinostat (10 to 20 nM) also induced significantly more apoptosis of HL-60, HEL and K562 (p &lt; 0.01), as well as of the primary CD34+ MPN, primary AML and CML progenitor cells. Notably, BC2059 (50 nM) also induced marked apoptosis of panobinostat-resistant cultured AML HL-60/LR cells (Blood 112: 2896, 2008). BC2059-based combinations were remarkably less toxic in normal CD34+ progenitor cells (p &lt; 0.01). Thus, BC2059 exerts notable in vitro and in vivo activity against human myeloid malignant cells. Additionally, BC2059 exerts superior activity in combination with an HDAC inhibitor, as well as with JAK2 or BCR-ABL-targeted TKI against AML, MPN and CML progenitor cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C144.