Abstract 5459: Preclinical efficacy of the novel PIM2 kinase inhibitor, JP_11646, in human acute leukemia models

Abstract

Abstract PIM kinases (PIM1,2, and 3) are constitutively active serine/threonine protein kinases which regulate cell cycle, survival, and drug resistance and have been strongly implicated in cancer cell survival and tumorigenesis. Although expression levels of PIM family members (PIM1, 2, and 3) differ by cancer type, PIM1 and PIM2 kinases are preferentially overexpressed in hematological malignancies. Here we studied the biological effects of treatment with a novel pan-PIM inhibitor, JP_11646 exhibiting potent inhibition of PIM2 kinase activity, in human acute myeloid (AML), acute lymphocytic leukemia (ALL), and lymphoma cell lines. Human AML cell lines (THP-1, KG-1, HL60-VCR, ML2, MV(4;11)) were evaluated for basal mRNA and protein expression of PIM kinases using real time PCR and western blot analysis, respectively. A panel of thirty additional human AML, ALL (Nalm-6), and lymphoma (RAJI) cell lines were exposed to JP_11646 at concentrations ranging from 0.001 to 10 uM for 48-72 hours followed by measurements of cell proliferation by MTT assay and cell viability by CellTiter-Glo assay. The Hill model was used to fit each concentration-response curve for each cell line and endpoint. Nonlinear regression analysis was performed using Phoenix 64 for estimation of IC50 and Imax. AML (HEL) cells after 72 hour of JP_11646 treatment were analyzed for induction of apoptosis measured via annexin V and 7AAD flow cytometry. AML cell lines exhibited differential basal mRNA expression of PIM kinases. The cell lines that expressed the highest levels of PIM1, PIM2, and PIM3 mRNA were THP-1 and ML2, respectively. Basal expression of the PIM2 protein revealed the presence of all three PIM2 isoforms in AML (HEL, THP-1) cells. JP_11646 treatment resulted in inhibition of proliferation across the entire panel of AML and ALL cell lines, with the overall potency (IC50) ranging from 0.07 to 0.37 uM and maximal inhibition ranging from 70 to 97.5 percent. As the drug exposure time increased from 48 to 72 hours, the maximal inhibition increased 2 to 3-fold. Inhibition of cell viability across a panel of 30 leukemia and lymphoma cell lines demonstrated a similar IC50 range from 0.05 to 0.25 uM. AML (HEL) cells treated with JP_116464 at doses of 0.1 and 0.5 uM for 72 hours exhibited a concentration-dependent induction of apoptosis of 32% and 89% percent, respectively. Taken together, our results demonstrate broad anti-leukemic activity and potency of the novel PIM kinase inhibitor, JP_11646, across a wide panel of human AML and ALL cell lines with induction of apoptosis and cell death at nM concentrations. Further, investigation of the in vivo effects of JP_11646 in representative human AML xenograft models is ongoing. Citation Format: Krista E. Pundt, Carmen M. Baldino, Justin Caserta, Stephane Dumas, Yvonne Flanders, Eunice S. Wang, Gerald J. Fetterly. Preclinical efficacy of the novel PIM2 kinase inhibitor, JP_11646, in human acute leukemia models. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5459. doi:10.1158/1538-7445.AM2014-5459