Novel inhibition of PIM2 kinase has significant anti-tumor efficacy in multiple myeloma

The PIM kinase family (PIM1, 2 and 3) have a central role in integrating growth and survival signals, and are expressed in a wide range of solid and hematological malignancies. We now confirm that PIM2 is overexpressed in multiple myeloma (MM) patients, and within MM group it is overexpressed in the high-risk MF subset (activation of proto-oncogenes MAF/MAFB). This is consistent with our finding of PIM2's role in key signaling pathways (IL-6, CD28 activation) that confer chemotherapy resistance in MM cells. These studies have identified a novel PIM2-selective non-ATP competitive inhibitor (JP11646) that has a 4 to 760-fold greater suppression of MM proliferation and viability than ATP-competitive PIM inhibitors. This increased efficacy is due not only to the inhibition of PIM2 kinase activity, but also to a novel mechanism involving specific downregulation of PIM2 mRNA and protein expression not seen with the ATP competitive inhibitors. Treatment with JP11646 in xenogeneic myeloma murine models demonstrated significant reduction in tumor burden and increased median survival. Altogether our findings suggest the existence of previously unrecognized feedback loop(s) where PIM2 kinase activity regulates PIM2 gene expression in malignant cells, and that JP11646 represents a novel class of PIM2 inhibitors that interdicts this feedback.

Abstract P6-11-10: Preclinical efficacy of the novel PIM2 kinase inhibitor, JP11646 in triple negative breast cancer models

Background: Triple negative breast cancer (TNBC) patients have poorer prognosis and there remains a lack of novel targeted therapies for their treatment. PIM2 (Proviral Integrations of Moloney virus 2) belongs to a family of three kinases that have been implicated in the survival and progression of hematologic malignancies and solid tumors. PIM2 has been linked to epithelial to mesenchymal transition in TNBC, which can lead to metastasis and chemotherapeutic resistance. We hypothesized that PIM2 may present as a therapeutic target in TNBC.

Materials and Methods: The study involved both in vitro and in vivo studies involving a novel PIM2 inhibitor JP11646 (obtained from Jasco Pharmaceuticals). TNBC cell lines MDA-MB-231 and BT-549 were obtained for our in vitro studies. Cell viability was evaluated using MTT assay. Western Blot assay was used to evaluate relative protein expression. For in vivo studies, female SCID mice were inoculated in the mammary fat pads with 1 × 106 MDA-MB-231 cells. When tumor volumes reached 100 mm3, the mice were treated with JP11646 at the dosage 15mg/kg intraperitoneally for 2 consecutive days weekly for total of 4 weeks as determined from previous experiments. Control animals received vehicle only. The mice were euthanized once tumors reached ∼1,700 mm3.

Results: BT-549 cells treated in vitro with 3 different available PIM kinase inhibitors AZD 1208, LGB321 and JP12641 showed only modest reduction in cell viability. However, treatment of both MDA-MB-231 and BT-549 with JP 11646 demonstrated significant reduction in cell viability with IC50 ranging from 40 to 71.6 nM. Treatment with JP11646 demonstrated a novel mechanism of action resulting in downregulation of PIM2 in both cell lines. Treatment with JP11646, but not other PIM kinase inhibitors, resulted in activation of apoptosis as measured by cleaved PARP (cPARP) levels. Anti-PIM2 siRNA treatment but not treatment with non-specific PIM kinase inhibitor AZD1208 resulted in cPARP induction. Inhibition of proteolysis by bortezomib resulted in preservation of PIM2 and inhibition of apoptosis as demonstrated by decreased cPARP levels after treatment with JP11646. PIM2 over-expressing clone of MDA-MB-231 cells showed enhanced proliferation and migration properties both in vitro and in vivo.Treatment of mice with orthotopically implanted MDA-MB-231 tumors with JP 11646 resulted in significant reduction in the tumor growth (p=0.0019) and increased overall survival (p=0.018) as compared to control mice.

Conclusions: PIM2 upregulation in TNBC cell line resulted in more aggressive phenotype. JP11646, through novel mechanism of action resulting in degradation of PIM2, showed robust activity in TNBC cell lines both in vitro and in vivo. Further correlative studies in tumors harvested from in vivo experiments are ongoing. These results encourage further exploration of use of JP11646 as a targeted agent in treatment of TNBC.

Citation Format: Mehta R, Kothai Guruswamy Sangameswaran D, Bezbatchenko K, Moore J, Gil M, Khoury T, Baldino C, Caserta J, Fetterly, Jr. G, Lee K, Adjei A, Opyrchal M. Preclinical efficacy of the novel PIM2 kinase inhibitor, JP11646 in triple negative breast cancer models [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-11-10.

Abstract 681: Translational pharmacology approaches to explore the novel mechanism of a pan-PIM kinase inhibitor, JP-11646, in acute myeloid leukemia

Leukemia, an aggressive immature hematological malignancy, is the sixth leading cause of cancer death in the U.S., with an overall cure rate of only 25%. PIM kinases are serine/threonine kinases that regulate cell cycle and survival. In hematological malignancies, PIM kinases are overexpressed, constitutively active, and associated with drug resistance. Thus, PIM kinases are novel therapeutic targets. JP-11646 is a pan-PIM inhibitor that has shown antitumor activity in various tumor types, with an increased potency against PIM2. In these studies, a comparison of three pan-PIM inhibitors on cell proliferation and PIM expression, along with the effect of JP-11646 on cellular signaling were investigated in human acute leukemia (AML).

An in vitro MTT assay was used to determine the overall anti-proliferative effects of various pan-PIM inhibitors in human AML (HEL, and MV(4;11)) cell lines. Cells were exposed to various concentrations (0.001 to 100 μM) of JP-11646, AZD1208 and LGB321. An Emax model was used to estimate the overall potency (IC50) and maximal inhibition (Imax) of the three inhibitors (0.06 μM, 0.20 μM and 0.43 μM and 89, 35 and 46 percent, respectively). It was determined that JP_11646 is 3-100 times more potent than AZD1208 and LGB321. Following inhibitor treatment (1, 2, 4, 6 and 24 hrs), PIM2 protein expression decreases by 50% at 6 hrs following 0.1 μM JP-11646; while both AZD1208 (0.45 μM) and LGB321 (0.20 μM) increase PIM2 protein expression by 1.5-fold following 2-6 hours of treatment. In conjunction with PIM 2 protein inhibition, real-time PCR results show that JP_11646 treatment results in a time- and concentration-dependent decrease of PIM1, 2 and 3 mRNA. In HEL cells, JP_11646 is more potent against PIM2, with PIM2 mRNA loss occurring as early as 1-2 hours post treatment. To determine the consequence of PIM inhibition via JP-11646, p-4EBP-1 and cleaved caspase protein expression were examined. Following 24 hours of JP-11646 treatment, p-4EBP-1 protein decreases in a concentration-dependent manner, suggesting the effect of JP-11646 on AML cell proliferation may be due to a disruption in p-4EBP-1 function in translation. Similarly, cleaved caspase increases and caspase 3 decreases following JP-11646 treatment, suggesting JP-11646 induces apoptosis. PE annexin V staining with FACS analysis confirmed that cells treated with JP-11646 undergo apoptotic or necrotic cell death in a time and concentration dependent manner, which is a unique characteristic of JP-11646 versus other known pan-PIM inhibitors.

In summary, the novel PIM kinase inhibitor, JP-11646, demonstrated more potent anti-leukemic activity than other pan-PIM kinase inhibitors in human AML cell lines. The modulation of PIM2 kinase, additional downstream targets, and the induction of apoptosis at nM concentrations by JP-11646 suggests JP-11646 is a novel and unique pan-PIM inhibitor.

Citation Format: Krista E. Pundt, Carmen Baldino, Justin Caserta, Laura B. Pitzonka, Kelvin Lee, Alex Adjei, Gerald J. Fetterly. Translational pharmacology approaches to explore the novel mechanism of a pan-PIM kinase inhibitor, JP-11646, in acute myeloid leukemia. [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 681. doi:10.1158/1538-7445.AM2015-681

Abstract 5056: PIM-1 kinase regulates vitamin D receptor signaling in human renal carcinoma cells

Dysregulation of vitamin D signaling and metabolism enzymes is a frequent change in many cancers and may confound approaches to vitamin -D based therapies. The mechanisms by which aberrant vitamin D signaling and metabolism lead to resistance to vitamin D action are poorly understood. The kidney plays a critical role in vitamin D synthesis and metabolism; in renal cell carcinoma (RCC) cells vitamin D metabolism is dysregulated. Recently, we discovered that an oncogenic protein kinase PIM-1 is involved in vitamin D-induced expression of 24-hydroxylase, a key catalytic enzyme of vitamin D encoded by CYP24A1 gene, in bladder and prostate cancer. To study the impact of PIM1 on vitamin D signaling and vitamin D-mediated anti-tumor activity in RCC, we analyzed 4 human renal cell carcinoma cell lines (Caki-1, ACHN, A498 and 786-O) and 25 samples of human RCC tumor tissue and 13 benign kidney tissues (including 10 matched tumor and benign tissue samples) by qRT-PCR, immunohistochemistry (IHC), Western blot analysis, MTT and clonogenic assays. VDR mRNA and protein were detected in all RCC cell lines. IHC showed that VDR was strongly expressed in the normal kidney tissues, but decreased in RCC tissues. As expected, VDR expression was significantly increased by treatment with 1,25-dihydroxyvitamin D3 (1,25D3) in RCC cell lines. MTT and clonogenic assays showed that 1,25D3 inhibited RCC cell growth (p<0.05). We also noted a significant increase of CYP24A1 expression induced by vitamin D3 (p<0.0001); and effect which would be expected to promote the catabolism of 1,25D3. qRT-PCR and Western blot analysis demonstrated that PIM-1 is expressed in RCC cells. PIM-1 inhibition by siRNA or PIM-1 inhibitor JP_11646 significantly reduced 1,25D3-induced CYP24A1 expression (p<0.05). Therefore, we hypothesized that targeting PIM-1 kinase activity with a PIM-1 inhibitor may be an effective strategy to reduce 1,25D3 metabolism, thereby enhancing vitamin D-mediated anti-tumor activity. Inhibition of PIM1 kinase activity by JP_11646 reduced CYP24A1 expression at the transcriptional level in RCC cells. We further evaluated the efficacy of the PIM1 inhibitor alone or in combination with 1,25D3. Inhibition of PIM1 kinase activity by JP_11646 reduced cell growth in RCC cell lines in a dose-dependent manner as measured by MTT and clonogenic assays. Furthermore, inhibition of PIM1 kinase activity enhances 1,25D3-mediated inhibitory effect on cell growth in RCC cells (p<0.05). This study indicates that PIM-1 is involved in the regulation of vitamin D signaling in RCC. Inhibition of PIM kinase activity combined with vitamin D may be an attractive new therapeutic strategy for RCC.

Citation Format: Wei Luo, Yingyu Ma, Carmen Baldino, Justin Caserta, Swathi Ramakrishnan, Pili Roberto, Candace Johnson, Donald Trump. PIM-1 kinase regulates vitamin D receptor signaling in human renal carcinoma cells. [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 5056. doi:10.1158/1538-7445.AM2015-5056

Surviving the odds: targeting PIM2 in plasma cell survival (TUM10P.1051)

Plasma cells (PC) depend on interactions with bone marrow stroma and the resultant growth factors for their long lived survival. Very little is known about the molecular mediators of these survival signals. One such molecule that has recently come of interest is PIM2. PC malignancies such as multiple myeloma (MM) preferentially express PIM2 over its counterparts PIM1 or PIM3 downstream of the PI3K/AKT/mTOR pathway essential for differentiation and survival of PC. In this study, we explored an experimental drug JP_11646 (Jasco Pharmaceuticals LLC) that has a high potency towards PIM kinases, more specifically towards PIM2. Using MM cell lines as a model for long term PC survival, we have shown for the first time that inhibiting PIM2 deregulates survival pathways that involve IL-6, DC protection of MM and CD28 activation by deregulating key survival factors such as NFκB, decreased phosphorylation and inactivation of the PIM2 substrate and pro-apoptotic protein BAD, lower levels of the inactive phosphorylated translational repressor 4EBP1, besides affecting transcription and translation of PIM2 itself. This was recapitulated when PIM2 was silenced with siRNA. Through northerns and protein assays, we also explore the transcriptional and translational dimensions involved in regulating PIM2 in plasma cells. An understanding of the role of PIM2 in MM biology will help to understand how plasma cells survive long term and maintain humoral immunity.