The proto-oncogene proviral integration site for moloney murine leukemia virus (PIM) kinases (PIM-1, PIM-2, and PIM-3) are serine/threonine kinases that are involved in a number of signaling pathways important to cancer cells. PIM kinases act in downstream effector functions as inhibitors of apoptosis and as positive regulators of G1-S phase progression through the cell cycle. PIM kinases are upregulated in multiple cancer indications, including lymphoma, leukemia, multiple myeloma, and prostate, gastric, and head and neck cancers. Overexpression of one or more PIM family members in patient tumors frequently correlates with poor prognosis. The aim of this investigation was to evaluate PIM expression in low- and high-grade urothelial carcinoma and to assess the role PIM function in disease progression and their potential to serve as molecular targets for therapy. One hundred thirty-seven cases of urothelial carcinoma were included in this study of surgical biopsy and resection specimens. High levels of expression of all three PIM family members were observed in both noninvasive and invasive urothelial carcinomas. The second-generation PIM inhibitor, TP-3654, displays submicromolar activity in pharmacodynamic biomarker modulation, cell proliferation studies, and colony formation assays using the UM-UC-3 bladder cancer cell line. TP-3654 displays favorable human ether-à-go-go-related gene and cytochrome P450 inhibition profiles compared with the first-generation PIM inhibitor, SGI-1776, and exhibits oral bioavailability. In vivo xenograft studies using a bladder cancer cell line show that PIM kinase inhibition can reduce tumor growth, suggesting that PIM kinase inhibitors may be active in human urothelial carcinomas.

Pyruvate kinase converts phosphoenolpyruvate to pyruvate, catalyzing the rate-limiting step of glycolysis. The M1 isoenzyme of pyruvate kinase (PKM1) is found in adult tissues; whereas, PKM2 is a splicesome variant found in embryonic and cancer cells. PKM2 expression in malignant cells is a result of the tumor microenvironment and is responsible for maintaining a glycolytic phenotype. PKM2 has other nonmetabolic functions in malignant cells, including transcriptional coactivation and protein kinase activity. PKM2 activators have antitumor properties by inducing tetramerization of two PKM2 dimers causing PKM2 to function like PKM1. Restoring PKM2 to PKM1-like levels of activity causes reversal of the Warburg effect in cancer cells. PKM2 activators have therapeutic potential in the treatment of cancer and other metabolic diseases.

Background. Nek2 is a serine/threonine kinase localized to the centrosome. It promotes cell cycle progression from G2 to M by inducing centrosome separation. Recent studies have shown that high Nek2 expression is correlated with drug resistance in multiple myeloma patients. Materials and Methods. To investigate the role of Nek2 in bortezomib resistance, we ectopically overexpressed Nek2 in several cancer cell lines, including multiple myeloma lines. Small-molecule inhibitors of Nek2 were discovered using an in-house library of compounds. We tested the inhibitors on proteasome and cell cycle activity in several cell lines. Results. Proteasome activity was elevated in Nek2-overexpressing cell lines. The Nek2 inhibitors inhibited proteasome activity in these cancer cell lines. Treatment with these inhibitors resulted in inhibition of proteasome-mediated degradation of several cell cycle regulators in HeLa cells, leaving them arrested in G2/M. Combining these Nek2 inhibitors with bortezomib increased the efficacy of bortezomib in decreasing proteasome activity in vitro. Treatment with these novel Nek2 inhibitors successfully mitigated drug resistance in bortezomib-resistant multiple myeloma. Conclusion. Nek2 plays a central role in proteasome-mediated cell cycle regulation and in conferring resistance to bortezomib in cancer cells. Taken together, our results introduce Nek2 as a therapeutic target in bortezomib-resistant multiple myeloma.

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The proto-oncogene PIM kinases (PIM-1, PIM-2, PIM-3) are serine/threonine kinases that have been shown to be involved in a number of signaling pathways important to cancer cells. PIM kinases act as downstream effectors as inhibitors of apoptosis and as positive regulators of G1-S phase progression through the cell cycle. PIM kinases are upregulated in multiple cancer indications, including lymphoma, leukemia, multiple myeloma, prostate, gastric, and head & neck cancers. Overexpression of one or more PIM family members in patient tumors frequently correlates with poor prognosis. The aim of this investigation was to evaluate PIM expression in low- and high-grade urothelial carcinoma, and to assess for expression that may contribute to disease progression and serve as a potential site for targeted therapy. Seventy-two cases of urothelial carcinoma were included in this retrospective study of surgical biopsy and resection specimens from the University of Utah Department of Pathology (retrieved from 2008-2011). Tissue was stained with commercially available antibodies against PIM-1, PIM-2, and PIM-3. Cases were divided into three groups (invasive high grade urothelial carcinoma (n=49), non-invasive urothelial carcinoma/carcinoma in situ (n=16), and non-invasive low grade urothelial carcinoma (n=7)). Individual cases were then given a score (0-4) based upon a percentage of cells staining positive for each antibody (<5%=0; 5-25%=1; 26-50%=2; 51-75%=3; >75%=4). A score of 2 or greater was considered expressed. PIM-1, PIM-2 and PIM-3 expression was noted in 29% (2/7), 43% (3/7) and 86% (6/7) cases of non-invasive low-grade urothelial carcinoma; 44% (7/16), 50% (8/16), 44% (7/16) cases of non-invasive high-grade urothelial carcinoma; 10% (5/49), 27% (13/49), and 18% (9/49) cases of invasive high-grade urothelial carcinoma, respectively. These results suggest that expression of PIM-1, PIM-2 and PIM-3 is present in a significant percentage of urothelial carcinomas and may serve as a source for targeted PIM-kinase inhibition. We have developed PIM inhibitors exhibiting 4-10 fold improved potency against the PIM kinase family compared to our original PIM inhibitor SGI-1776. Our PIM inhibitors display sub-μM activity in pharmacodynamic marker modulation, proliferation and 2D colony formation assays using the UM-UC-3 bladder cancer cell line. These PIM kinase inhibitors also are potent inducers of apoptosis in T24, RT4, and UM-UC-3 bladder cancer cell lines. These compounds have favorable hERG and CYP inhibition profiles compared with SGI-1776, and demonstrate excellent oral bioavailability. In vivo xenograft studies using bladder cancer cell line models show that PIM kinase inhibition can reduce the tumor growth of these tumor models suggesting that PIM kinase inhibitors may be active in human urothelial carcinomas. Citation Format: Kent J. Carpenter, Rachel Brog, Christopher Moreno, Daniel J. Albertson, Jared J. Bearss, Ting Liu, Steven Warner, David J. Bearss. Small molecule iInhibitors of PIM kinases as potential treatments for urothelial carcinomas. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2174. doi:10.1158/1538-7445.AM2013-2174