Pim kinase inhibitor, SGI-1776, induces apoptosis in chronic lymphocytic leukemia cells. Blood. 2009;114:4150-4157. [PMID: 19734450 DOI: 10.1182/blood-2009-03-212852]

Targeting STAT5 or STAT5-Regulated Pathways Suppresses Leukemogenesis of Ph+ Acute Lymphoblastic Leukemia

Combining standard cytotoxic chemotherapy with BCR-ABL1 tyrosine kinase inhibitors (TKI) has greatly improved the upfront treatment of patients with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL). However, due to the development of drug resistance through both BCR-ABL1-dependent and -independent mechanisms, prognosis remains poor. The STAT5 transcription factor is activated by BCR-ABL1 and by JAK2-dependent cytokine signaling; therefore, inhibiting its activity could address both mechanisms of resistance in Ph+ ALL. We show here that genetic and pharmacologic inhibition of STAT5 activity suppresses cell growth, induces apoptosis, and inhibits leukemogenesis of Ph+ cell lines and patient-derived newly diagnosed and relapsed/TKI-resistant Ph+ ALL cells ex vivo and in mouse models. STAT5 silencing decreased expression of the growth-promoting PIM-1 kinase, the apoptosis inhibitors MCL1 and BCL2, and increased expression of proapoptotic BIM protein. The resulting apoptosis of STAT5-silenced Ph+ BV173 cells was rescued by silencing of BIM or restoration of BCL2 expression. Treatment of Ph+ ALL cells, including samples from relapsed/refractory patients, with the PIM kinase inhibitor AZD1208 and/or the BCL2 family antagonist Sabutoclax markedly suppressed cell growth and leukemogenesis ex vivo and in mice. Together, these studies indicate that targeting STAT5 or STAT5-regulated pathways may provide a new approach for therapy development in Ph+ ALL, especially the relapsed/TKI-resistant disease.Significance: Suppression of STAT5 by BCL2 and PIM kinase inhibitors reduces leukemia burden in mice and constitutes a new potential therapeutic approach against Ph+ ALL, especially in tyrosine kinase inhibitor-resistant disease. Cancer Res; 78(20); 5793-807. ©2018 AACR.

The dual inhibitor of the phosphoinositol-3 and PIM kinases, IBL-202, is effective against chronic lymphocytic leukaemia cells under conditions that mimic the hypoxic tumour microenvironment

Despite significant advances in treatment, chronic lymphocytic leukaemia (CLL) remains an incurable disease. Ibrutinib and idelalisib, which inhibit Bruton Tyrosine kinase (BTK) and phosphoinositol-3 (PI3) kinase-δ respectively, have become important treatment options for the disease and demonstrate the potential of targeting components of the B-cell receptor-signalling pathway. IBL-202 is a dual inhibitor of the PIM and PI3 kinases. Synergy between the pan-PIM inhibitor, pPIMi, and idelalisib against a range of haematological cell lines and primary CLL cells supports the rationale for preclinical studies of IBL-202 in CLL. Importantly, IBL-202, but not idelalisib, was cytotoxic against CLL cells under in vitro conditions that mimic the hypoxic tumour microenvironment. The significant effects of IBL-202 on CD49d and CXCR4 expression and migration, cycle and proliferation of CLL cells suggest the drug may also interfere with the migratory and proliferative capacity of the leukaemic cells. Collectively, these data demonstrate that dual inhibition of the PIM and PI3 kinases by IBL-202 may be an effective strategy for targeting CLL cells, particularly within the environmental niches known to confer drug-resistance.

Biological properties and structural study of new aminoalkyl derivatives of benzimidazole and benzotriazole, dual inhibitors of CK2 and PIM1 kinases

The new aminoalkyl-substituted derivatives of known CK2 inhibitors 4,5,6,7-tetrabromo-1H-benzimidazole (TBBi) and 4,5,6,7-tetrabromo-1H-benzotriazole (TBBt) were synthesized, and their influence on the activity of recombinant human CK2 α, CK2 holoenzyme and PIM1 kinases was evaluated. All derivatives inhibited the activity of studied kinases and the most efficient were aminopropyl-derivatives 8b and 14b. These compounds also exerted inhibition of cancer cell lines - CCRF-CEM (acute lymphoblastoid leukemia), MCF-7 (human breast cancer), and PC-3 (prostate cancer) proliferation and their EC₅₀ is comparable with the value for clinically studied CK2 inhibitor CX-4945. Preliminary structure activity relationship analysis indicated that the spacer length affected antitumor potency, and two to three methylene units were more favorable. The complex of CK2 α^1-335/8b was crystallized, both under high-salt conditions and under low-salt conditions giving crystals which diffracted X-rays to about 2.4 Å resolution, what enabled the determination of the corresponding 3D-structures.

Preclinical characterization of INCB053914, a novel pan-PIM kinase inhibitor, alone and in combination with anticancer agents, in models of hematologic malignancies

The Proviral Integration site of Moloney murine leukemia virus (PIM) serine/threonine protein kinases are overexpressed in many hematologic and solid tumor malignancies and play central roles in intracellular signaling networks important in tumorigenesis, including the Janus kinase-signal transducer and activator of transcription (JAK/STAT) and phosphatidylinositol 3-kinase (PI3K)/AKT pathways. The three PIM kinase isozymes (PIM1, PIM2, and PIM3) share similar downstream substrates with other key oncogenic kinases and have differing but mutually compensatory functions across tumors. This supports the therapeutic potential of pan-PIM kinase inhibitors, especially in combination with other anticancer agents chosen based on their role in overlapping signaling networks. Reported here is a preclinical characterization of INCB053914, a novel, potent, and selective adenosine triphosphate-competitive pan-PIM kinase inhibitor. In vitro, INCB053914 inhibited proliferation and the phosphorylation of downstream substrates in cell lines from multiple hematologic malignancies. Effects were confirmed in primary bone marrow blasts from patients with acute myeloid leukemia treated ex vivo and in blood samples from patients receiving INCB053914 in an ongoing phase 1 dose-escalation study. In vivo, single-agent INCB053914 inhibited Bcl-2-associated death promoter protein phosphorylation and dose-dependently inhibited tumor growth in acute myeloid leukemia and multiple myeloma xenografts. Additive or synergistic inhibition of tumor growth was observed when INCB053914 was combined with selective PI3Kδ inhibition, selective JAK1 or JAK1/2 inhibition, or cytarabine. Based on these data, pan-PIM kinase inhibitors, including INCB053914, may have therapeutic utility in hematologic malignancies when combined with other inhibitors of oncogenic kinases or standard chemotherapeutics.

Structure-based design of novel quinoxaline-2-carboxylic acids and analogues as Pim-1 inhibitors

We identified a new series of quinoxaline-2-carboxylic acid derivatives, targeting the human proviral integration site for Moloney murine leukemia virus-1 (HsPim-1) kinase. Seventeen analogues were synthesized providing useful insight into structure-activity relationships studied. Docking studies realized in the ATP pocket of HsPim-1 are consistent with an unclassical binding mode of these inhibitors. The lead compound 1 was able to block HsPim-1 enzymatic activity at nanomolar concentrations (IC₅₀ of 74 nM), with a good selectivity profile against a panel of mammalian protein kinases. In vitro studies on the human chronic myeloid leukemia cell line KU812 showed an antitumor activity at micromolar concentrations. As a result, compound 1 represents a promising lead for the design of novel anticancer targeted therapies.

Microenvironment-induced PIM kinases promote CXCR4-triggered mTOR pathway required for chronic lymphocytic leukaemia cell migration

Lymph node microenvironment provides chronic lymphocytic leukaemia (CLL) cells with signals promoting their survival and granting resistance to chemotherapeutics. CLL cells overexpress PIM kinases, which regulate apoptosis, cell cycle and migration. We demonstrate that BCR crosslinking, CD40 stimulation, and coculture with stromal cells increases PIMs expression in CLL cells, indicating microenvironment‐dependent PIMs regulation. PIM1 and PIM2 expression at diagnosis was higher in patients with advanced disease (Binet C vs. Binet A/B) and in those, who progressed after first‐line treatment. In primary CLL cells, inhibition of PIM kinases with a pan‐PIM inhibitor, SEL24‐B489, decreased PIM‐specific substrate phosphorylation and induced dose‐dependent apoptosis in leukaemic, but not in normal B cells. Cytotoxicity of SEL24‐B489 was similar in TP53‐mutant and TP53 wild‐type cells. Finally, inhibition of PIM kinases decreased CXCR4‐mediated cell chemotaxis in two related mechanisms‐by decreasing CXCR4 phosphorylation and surface expression, and by limiting CXCR4‐triggered mTOR pathway activity. Importantly, PIM and mTOR inhibitors similarly impaired migration, indicating that CXCL12‐triggered mTOR is required for CLL cell chemotaxis. Given the microenvironment‐modulated PIM expression, their pro‐survival function and a role of PIMs in CXCR4‐induced migration, inhibition of these kinases might override microenvironmental protection and be an attractive therapeutic strategy in this disease.

Control of translational activation by PIM kinase in activated B-cell diffuse large B-cell lymphoma confers sensitivity to inhibition by PIM447

The PIM family kinases promote growth and survival of tumor cells and are expressed in a wide variety of human cancers. Their potential as therapeutic targets, however, is complicated by overlapping activities with multiple other pathways and remains poorly defined in most clinical scenarios. Here we explore activity of the new pan-PIM inhibitor PIM447 in a variety of lymphoid-derived tumors. We find strong activity in cell lines derived from the activated B-cell subtype of diffuse large B-cell lymphoma (ABC-DLBCL). Sensitive lines show lost activation of the mTORC1 signaling complex and subsequent lost activation of cap-dependent protein translation. In addition, we characterize recurrent PIM1 protein-coding mutations found in DLBCL clinical samples and find most preserve the wild-type protein's ability to protect cells from apoptosis but do not bypass activity of PIM447. Pan-PIM inhibition therefore may have an important role to play in the therapy of selected ABC-DLBCL cases.

PIM kinases as therapeutic targets against advanced melanoma

Therapeutic strategies for the treatment of metastatic melanoma show encouraging results in the clinic; however, not all patients respond equally and tumor resistance still poses a challenge. To identify novel therapeutic targets for melanoma, we screened a panel of structurally diverse organometallic inhibitors against human-derived normal and melanoma cells. We observed that a compound that targets PIM kinases (a family of Ser/Thr kinases) preferentially inhibited melanoma cell proliferation, invasion, and viability in adherent and three-dimensional (3D) melanoma models. Assessment of tumor tissue from melanoma patients showed that PIM kinases are expressed in pre- and post-treatment tumors, suggesting PIM kinases as promising targets in the clinic. Using knockdown studies, we showed that PIM1 contributes to melanoma cell proliferation and tumor growth in vivo; however, the presence of PIM2 and PIM3 could also influence the outcome. The inhibition of all PIM isoforms using SGI-1776 (a clinically-available PIM inhibitor) reduced melanoma proliferation and survival in preclinical models of melanoma. This was potentiated in the presence of the BRAF inhibitor PLX4720 and in the presence of PI3K inhibitors. Our findings suggest that PIM inhibitors provide promising additions to the targeted therapies available to melanoma patients.

Pim-2 Cooperates with Downstream Factor XIAP to Inhibit Apoptosis and Intensify Malignant Grade in Prostate Cancer

To find the exact downstream effector of Pim-2 pathway in prostate cancer cells, and to determine the means by which it affects prostate cancer. XIAP, Pim-2 and p-eIF4B expressions were detected in PCA and BPH tissues. Then the Pim-2 and XIAP expressions were manipulated using transfection or RNAi in prostatic cells. Finally, Pim-2/eIF4B/XIAP levels were examined in PCA tissues with different clinicopathologic features. XIAP was significantly higher in PCA than in BPH tissues. When Pim-2 was transfected into noncancerous prostate epithelial cells RWPE-1, Pim-2, p-eIF4B and XIAP were all significantly increased and the apoptosis rate was significantly decreased. When XIAP was transfected into RWPE-1 cells, XIAP was significantly increased with no impact on Pim-2, p-eIF4B and the apoptosis rate. When Pim-2 SiRNA was transfected into prostate cancer cells PC-3, Pim-2, p-eIF4B and XIAP were significantly decreased and the apoptosis rate was significantly increased. When XIAP SiRNA was transfected into PC-3 cells, XIAP was significantly decreased with no impact on Pim-2, p-eIF4B and apoptosis rate. Pim-2, p-eIF4B and XIAP were all significantly higher in PCA tissues with GS ≥8 than those with GS ≤7. XIAP is the downstream factor of Pim-2 pathway in prostate cancer cells. Pim-2 and XIAP cooperate in inhibiting the apoptosis of prostate cancer cells. The activation of Pim-2 pathway may predict higher GS in prostate cancer.

PIM activity in tumours: A key node of therapy resistance

The PIM kinases are proto-oncogenes which have been shown to facilitate cell survival and proliferation to drive malignancy and resistance post-therapy. They are able to suppress cell death signals, sustain PI3K/AKT/mTORC1 pathway activity and regulate the MYC oncogenic program. Recent work has revealed PIM kinase essentiality for advanced tumour maintenance and described tumour sensitivity to small molecule inhibitors targeting PIM kinase in multiple malignancies.

Expression and significance of Pim-3 kinase in adult T-cell leukemia

BACKGROUND

Human T-cell leukemia virus type 1 (HTLV-1) causes adult T-cell leukemia (ATL). Viral Tax protein plays a major role in ATL development. Pim family of serine/threonine kinases is composed of Pim-1, -2, and -3. The potential of Pim family as a target in ATL was analyzed.

METHODS

RT-PCR and Western blotting were used to determine the expression of Pim kinases, Tax, and intracellular signal molecules. Knockdown of Pim-3 and RelA was performed using small interfering RNA. The effects on cell proliferation, viability, cell cycle, and apoptosis were analyzed by WST-8, propidium iodide, and APO2.7 assay. NF-κB DNA binding activity was investigated by electrophoretic mobility shift assay.

RESULTS

Pim-3 expression was restricted to HTLV-1-infected T-cell lines. Tax induced Pim-3 expression through NF-κB. Knockdown of Pim-3 showed growth inhibition of HTLV-1-infected T cells. NJC97-NH, a novel inhibitor of the Pim-1/3 kinases, inhibited cell viability. NJC97-NH induced G2/M cell cycle arrest associated with downregulation of cyclin A and cyclin B1 expression, as well as apoptosis accompanied with downregulation of XIAP and Mcl-1 expression through inhibition of NF-κB pathway, mediated through decrease in IκBα and RelA phosphorylation.

CONCLUSION

Pim-3 is a potentially suitable target for the development of novel therapeutic agents against ATL.

PIM-1 kinase inhibitor SMI-4a exerts antitumor effects in chronic myeloid leukemia cells by enhancing the activity of glycogen synthase kinase 3β

The development of targeted tyrosine kinase inhibitors (TKIs) has succeeded in altering the course of chronic myeloid leukemia (CML). However, a number of patients have failed to respond or experienced disease relapse following TKI treatment. Proviral integration site for moloney murine leukemia virus-1 (PIM-1) is a serine/threonine kinase that participates in regulating apoptosis, cell cycle, signal transduction and transcriptional pathways, which are associated with tumor progression, and poor prognosis. SMI-4a is a selective PIM-1 kinase inhibitor that inhibits PIM-1 kinase activity in vivo and in vitro. The present study aimed to explore the mechanism underlying the antitumor effect of SMI-4a in K562 and imatinib-resistant K562 (K562/G) cell lines. It was demonstrated that SMI-4a inhibited the proliferation of K562 and K562/G cells using a WST-8 assay. The Annexin V-propidium iodide assay demonstrated that SMI-4a induced apoptosis of K562 and K562/G cells in a dose-, and time-dependent manner. Furthermore, Hoechst 33342 staining was used to verify the apoptosis rate. The clone formation assay revealed that SMI-4a significantly inhibited the colony formation capacity of K562 and K562/G cells. Western blot analysis demonstrated that SMI-4a decreased phosphorylated (p)-Ser9-glycogen synthase kinase (GSK) 3β/pGSK3β and inhibited the translocation of β-catenin. In addition, the downstream gene expression of apoptosis regulator Bax and poly(ADP-ribose) polymerase-1 was upregulated, and apoptosis regulator Bcl-2 and Myc proto-oncogene protein expression levels were downregulated. Immunofluorescence results demonstrated changes in the expression level of β-catenin in the plasma and nucleus. The results of the present study suggest that SMI-4a is an effective drug to use in combination with current chemotherapeutics for the treatment of imatinib-resistant CML.

The addition of abemaciclib to sunitinib induces regression of renal cell carcinoma xenograft tumors

Multiple therapies currently exist for renal cell carcinoma, however, most do not result in cure and the development of acquired resistance is the rule rather than the exception. CDK4/6 and PIM1 kinases are potential new therapeutic targets in RCC. Abemaciclib is a potent CDK4/6 and PIM1 kinase inhibitor, thus we evaluated the effects of abemaciclib on renal cell carcinoma. In vitro, abemaciclib causes decreased cellular viability, increased apoptosis, and alterations in autophagy in renal cell carcinoma cell lines. A pre-clinical mouse model of RCC shows abemaciclib in combination with sunitinib to cause dramatic reduction in tumor sizes without overt toxicity. Thus abemaciclib is active in renal cell carcinoma and should be evaluated in a clinical trial in combination with sunitinib. Additionally, CDK4/6 and PIM1 kinase appear to be viable clinical targets in renal cell carcinoma.

PIM kinases 1, 2 and 3 in intracellular LIF signaling, proliferation and apoptosis in trophoblastic cells

Proviral insertion in murine (PIM) lymphoma proteins are mainly regulated by the Janus Kinase/Signal Transducer Activator of Transcription (JAK/STAT) signaling pathway, which can be activated by members of the Interleukin-6 (IL-6) family, including Leukemia Inhibitory Factor (LIF). Aim of the study was to compare PIM1, PIM2 and PIM3 expression and potential cellular functions in human first and third trimester trophoblast cells, the immortalized first trimester extravillous trophoblast cell line HTR8/SVneo and the choriocarcinoma cell line JEG-3. Expression was analyzed by qPCR and immunochemical staining. Functions were evaluated by PIM inhibition followed by analysis of kinetics of cell viability as assessed by MTS assay, proliferation by BrdU assay, and apoptosis by Western blotting for BAD, BCL-XL, (cleaved) PARP, CASP3 and c-MYC. Apoptosis and necrosis were tested by flow cytometry (annexin V/propidium iodide staining). All analyzed PIM kinases are expressed in primary trophoblast cells and both cell lines and are regulated upon stimulation with LIF. Inhibition of PIM kinases significantly reduces viability and proliferation and induces apoptosis. Simultaneously, phosphorylation of c-MYC was reduced. These results demonstrate the involvement of PIM kinases in LIF-induced regulation in different trophoblastic cell lines which may indicate similar functions in primary cells.

Expression of PIM kinases in Reed-Sternberg cells fosters immune privilege and tumor cell survival in Hodgkin lymphoma

Reed-Sternberg (RS) cells of classical Hodgkin lymphoma (cHL) express multiple immunoregulatory proteins that shape the cHL microenvironment and allow tumor cells to evade immune surveillance. Expression of certain immunoregulatory proteins is modulated by prosurvival transcription factors, such as NFκB and STATs. Because these factors also induce expression of the oncogenic PIM1/2/3 serine/threonine kinases, and as PIMs modulate transcriptional activity of NFκB and STATs, we hypothesized that these kinases support RS cell survival and foster their immune privilege. Here, we investigated PIM1/2/3 expression in cHL and assessed their role in developing RS cell immune privilege and survival. PIM1/2/3 were ubiquitously expressed in primary and cultured RS cells, and their expression was driven by JAK-STAT and NFκB activity. Genetic or chemical PIM inhibition with a newly developed pan-PIM inhibitor, SEL24-B489, induced RS cell apoptosis. PIM inhibition decreased cap-dependent protein translation, blocked JAK-STAT signaling, and markedly attenuated NFκB-dependent gene expression. In a cHL xenograft model, SEL24-B489 delayed tumor growth by 95.8% (P = .0002). Furthermore, SEL24-B489 decreased the expression of multiple molecules engaged in developing the immunosuppressive microenvironment, including galectin-1 and PD-L1/2. In coculture experiments, T cells incubated with SEL24-B489-treated RS cells exhibited higher expression of activation markers than T cells coincubated with control RS cells. Taken together, our data indicate that PIM kinases in cHL exhibit pleiotropic effects, orchestrating tumor immune escape and supporting RS cell survival. Inhibition of PIM kinases decreases RS cell viability and disrupts signaling circuits that link these cells with their niches. Thus, PIM kinases are promising therapeutic targets in cHL.

Cell lines generated from a chronic lymphocytic leukemia mouse model exhibit constitutive Btk and Akt signaling

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of mature CD5⁺ B cells in blood. Spontaneous apoptosis of CLL cells in vitro has hampered in-depth investigation of CLL pathogenesis. Here we describe the generation of three monoclonal mouse cell lines, EMC2, EMC4 and EMC6, from the IgH.TEμ CLL mouse model based on sporadic expression of SV40 large T antigen. The cell lines exhibit a stable CD5⁺CD43⁺IgM⁺CD19⁺ CLL phenotype in culture and can be adoptively transferred into Rag1^−/− mice. RNA-seq analysis revealed only minor differences between the cell lines and their primary tumors and suggested that NF-κB and mTOR signaling pathways were involved in cell line outgrowth. In vitro survival and proliferation was dependent on constitutive phosphorylation of Bruton's tyrosine kinase (Btk) at Y551/Y223, and Akt(S473). Treatment of the cell lines with small molecule inhibitors specific for Btk (ibrutinib) or PI3K (idelalisib), which is upstream of Akt, resulted in reduced viability, proliferation and fibronectin-dependent cell adhesion. Treatment of cell line-engrafted Rag1^−/− mice with ibrutinib was associated with transient lymphocytosis, reduced splenomegaly and increased overall survival. Thus, by generating stable cell lines we established a novel platform for in vitro and in vivo investigation of CLL signal transduction and treatment modalities.

Design and Synthesis of Potent and Selective PIM Kinase Inhibitors by Targeting Unique Structure of ATP-Binding Pocket

In the development of kinase inhibitors, one of the major concerns is selectivity. An effective strategy to achieve high selectivity is to utilize structural differences among kinases to inform inhibitor design. Here, we set out to improve the PIM (proviral integration site for Moloney murine leukemia virus) kinase-inhibitory selectivity of our previously reported 7-azaindole derivative 2, which has promising ADMET properties, by targeting a unique bulge in the ATP-binding pocket. 6-Substituted 7-azaindoles, especially the 6-chlorinated derivatives, proved to be potent and selective PIM kinase inhibitors and appear to be promising lead compounds for future drug discovery.

Biochemical changes of salivary gland adenoid cystic carcinoma cells induced by SGI-1776

Provirus integration site for Moloney murine leukemia virus 1 (Pim-1) has proved to be an oncogene and it is known that to depress Pim-1 activity may be a novel oncological treatment strategy. SGI-1776, a small molecule, is the first clinically tested inhibitor of the Pim kinase family. Here, we aimed to explore the effect of SGI-1776 on salivary adenoid cystic carcinoma (SACC). Expression of Pim-1 was confirmed in SACC and control tissues by qRT-PCR. After SGI-1776 treatment, the Pim-1 expressions and Pim-1 kinase activity in both SACC-83 and SACC-LM cell lines were measured. Cell proliferation, cell invasion, cell cycle, apoptosis and mitochondrial membrane potential were analyzed. Also, the expression of FOXO3a, p-FOXO3a, RUNX3, Bcl-2, BAD, p-BAD, Bim and p-Bim were detected by Western blot. The results showed that Pim-1 was significantly overexpressed in SACC tissues. SGI-1776 down-regulated the Pim-1 expression, inhibited Pim-1 kinase activity, reduced cell proliferation, decreased invasive ability, increased caspase-3 activity and induced apoptosis, cell cycle arrest and mitochondrial depolarization. Reduced expression was also seen in p-FOXO3a, RUNX3, Bcl-2, p-BAD and p-Bim, whereas no significant changes were observed from FOXO3a, BAD and Bim. These results confirm the pivotal role of Pim-1 in SACC and suggest that targeting Pim-1 kinase signal pathway by SGI-1776 might be a promising therapeutic modality for SACC.

eIF4B is a convergent target and critical effector of oncogenic Pim and PI3K/Akt/mTOR signaling pathways in Abl transformants

Activation of eIF4B correlates with Abl-mediated cellular transformation, but the precise mechanisms are largely unknown. Here we show that eIF4B is a convergent substrate of JAK/STAT/Pim and PI3K/Akt/mTOR pathways in Abl transformants. Both pathways phosphorylated eIF4B in Abl-transformed cells, and such redundant regulation was responsible for the limited effect of single inhibitor on Abl oncogenicity. Persistent inhibition of one signaling pathway induced the activation of the other pathway and thereby restored the phosphorylation levels of eIF4B. Simultaneous inhibition of the two pathways impaired eIF4B phosphorylation more effectively, and synergistically induced apoptosis in Abl transformed cells and inhibited the growth of engrafted tumors in nude mice. Similarly, the survival of Abl transformants exhibited a higher sensitivity to the pharmacological inhibition, when combined with the shRNA-based silence of the other pathway. Interestingly, such synergy was dependent on the phosphorylation status of eIF4B on Ser422, as overexpression of eIF4B phosphomimetic mutant S422E in the transformants greatly attenuated the synergistic effects of these inhibitors on Abl oncogenicity. In contrast, eIF4B knockdown sensitized Abl transformants to undergo apoptosis induced by the combined blockage. Collectively, the results indicate that eIF4B integrates the signals from Pim and PI3K/Akt/mTOR pathways in Abl-expressing leukemic cells, and is a promising therapeutic target for such cancers.

Cancer's Achilles' Heel: Apoptosis and Necroptosis to the Rescue

Apoptosis, and the more recently discovered necroptosis, are two avenues of programmed cell death. Cancer cells survive by evading these two programs, driven by oncogenes and tumor suppressor genes. While traditional therapy using small molecular inhibitors and chemotherapy are continuously being utilized, a new and exciting approach is actively underway by identifying and using synergistic relationship between driver and rescue genes in a cancer cell. Through these synthetic lethal relationships, we are gaining tremendous insights into tumor vulnerabilities and specific molecular avenues for induction of programmed cell death. In this review, we briefly discuss the two cell death processes and cite examples of such synergistic manipulations for therapeutic purposes.

PIM1 kinase inhibition as a targeted therapy against triple-negative breast tumors with elevated MYC expression

Triple-negative breast cancer (TNBC), in which cells lack expression of the estrogen receptor (ER), the progesterone receptor (PR) and the ERBB2 (also known as HER2) receptor, is the breast cancer subtype with the poorest outcome. No targeted therapy is available against this subtype of cancer owing to a lack of validated molecular targets. We previously reported that signaling involving MYC-an essential, pleiotropic transcription factor that regulates the expression of hundreds of genes-is disproportionally higher in triple-negative (TN) tumors than in receptor-positive (RP) tumors. Direct inhibition of the oncogenic transcriptional activity of MYC has been challenging to achieve. Here, by conducting a shRNA screen targeting the kinome, we identified PIM1, a non-essential serine-threonine kinase, in a synthetic lethal interaction with MYC. PIM1 expression was higher in TN tumors than in RP tumors and was associated with poor prognosis in patients with hormone- and HER2-negative tumors. Small-molecule PIM kinase inhibitors halted the growth of human TN tumors with elevated MYC expression in patient-derived tumor xenograft (PDX) and MYC-driven transgenic mouse models of breast cancer by inhibiting the oncogenic transcriptional activity of MYC and restoring the function of the endogenous cell cycle inhibitor, p27. Our findings warrant clinical evaluation of PIM kinase inhibitors in patients with TN tumors that have elevated MYC expression.

The PIM inhibitor AZD1208 synergizes with ruxolitinib to induce apoptosis of ruxolitinib sensitive and resistant JAK2-V617F-driven cells and inhibit colony formation of primary MPN cells

Classical myeloproliferative neoplasms (MPNs) are hematopoietic stem cell disorders that exhibit excess mature myeloid cells, bone marrow fibrosis, and risk of leukemic transformation. Aberrant JAK2 signaling plays an etiological role in MPN formation. Because neoplastic cells in patients are largely insensitive to current anti-JAK2 therapies, effective therapies remain needed. Members of the PIM family of serine/threonine kinases are induced by JAK/STAT signaling, regulate hematopoietic stem cell growth, protect hematopoietic cells from apoptosis, and exhibit hematopoietic cell transforming properties. We hypothesized that PIM kinases may offer a therapeutic target for MPNs. We treated JAK2-V617F-dependent MPN model cells as well as primary MPN patient cells with the PIM kinase inhibitors SGI-1776 and AZD1208 and the JAK2 inhibitor ruxolitinib. While MPN model cells were rather insensitive to PIM inhibitors, combination of PIM inhibitors with ruxolitinib led to a synergistic effect on MPN cell growth due to enhanced apoptosis. Importantly, PIM inhibitor mono-therapy inhibited, and AZD1208/ruxolitinib combination therapy synergistically suppressed, colony formation of primary MPN cells. Enhanced apoptosis by combination therapy was associated with activation of BAD, inhibition of downstream components of the mTOR pathway, including p70S6K and S6 protein, and activation of 4EBP1. Importantly, PIM inhibitors re-sensitized ruxolitinib-resistant MPN cells to ruxolitinib by inducing apoptosis. Finally, exogenous expression of PIM1 induced ruxolitinib resistance in MPN model cells. These data indicate that PIMs may play a role in MPNs and that combining PIM and JAK2 kinase inhibitors may offer a more efficacious therapeutic approach for MPNs over JAK2 inhibitor mono-therapy.

ATM function and its relationship with ATM gene mutations in chronic lymphocytic leukemia with the recurrent deletion (11q22.3-23.2)

Approximately 10–20% of chronic lymphocytic leukemia (CLL) patients exhibit del(11q22–23) before treatment, this cohort increases to over 40% upon progression following chemoimmunotherapy. The coding sequence of the DNA damage response gene, ataxia-telangiectasia-mutated (ATM), is contained in this deletion. The residual ATM allele is frequently mutated, suggesting a relationship between gene function and clinical response. To investigate this possibility, we sought to develop and validate an assay for the function of ATM protein in these patients. SMC1 (structural maintenance of chromosomes 1) and KAP1 (KRAB-associated protein 1) were found to be unique substrates of ATM kinase by immunoblot detection following ionizing radiation. Using a pool of eight fluorescence in situ hybridization-negative CLL samples as a standard, the phosphorylation of SMC1 and KAP1 from 46 del (11q22–23) samples was analyzed using normal mixture model-based clustering. This identified 13 samples (28%) that were deficient in ATM function. Targeted sequencing of the ATM gene of these samples, with reference to genomic DNA, revealed 12 somatic mutations and 15 germline mutations in these samples. No strong correlation was observed between ATM mutation and function. Therefore, mutation status may not be taken as an indicator of ATM function. Rather, a direct assay of the kinase activity should be used in the development of therapies.

Characterization of HJ-PI01 as a novel Pim-2 inhibitor that induces apoptosis and autophagic cell death in triple-negative human breast cancer

AIM

Pim-2 is a short-lived serine/threonine kinase, which plays a key role in metastasis of breast cancer through persistent activation of STAT3. Although the crystal structure of Pim-2 has been reported, but thus far no specific Pim-2-targeted compounds have been reported. In this study, we identified a novel Pim-2 inhibitor, HJ-PI01, by in silico analysis and experimental validation.

METHODS

The protein-protein interaction (PPI) network, chemical synthesis, molecular docking, and molecular dynamics (MD) simulations were used to design and discover the new Pim-2 inhibitor HJ-PI01. The anti-tumor effects of HJ-PI01 were evaluated in human breast MDA-MB-231, MDA-MB-468, MDA-MB-436, MCF-7 cells in vitro and in MDA-MB-231 xenograft mice, which were treated with HJ-PI01 (40 mg·kg(-1)·d(-1), ig) with or without lienal polypeptide (50 mg·kg(-1)·d(-1), ip) for 10 d. The apoptosis/autophage-inducing mechanisms of HJ-PI01 were elucidated using Western blots, immunoblots, flow cytometry, transmission electron microscopy and fluorescence microscopy.

RESULTS

Based on the PrePPI network, the potential partners interacting with Pim-2 in regulating apoptosis (160 protein pairs) and autophagy (47 protein pairs) were identified. Based on the structural characteristics of Pim-2, a total of 15 compounds (HJ-PI01 to HJ-P015) were synthesized, which showed moderate or remarkable anti-proliferative potency in the human breast cancer cell lines tested. The most effective compound HJ-PI01 exerted a robust inhibition on MDA-MB-231 cells compared with chlorpromazine and the pan-Pim inhibitor PI003. Molecular dynamics (MD) simulation revealed that HJ-PI01 had a good binding score with Pim-2. Moreover, HJ-PI01 (300 nmol/L) induced death receptor-dependent and mitochondrial apoptosis as well as autophagic death in MDA-MB-231 cells. In MDA-MB-231 xenograft mice, administration of HJ-PI01 remarkably inhibited the tumor growth and induced tumor cell apoptosis in vivo. Co-administration of HJ-PI01 with lienal polypeptide could improve the anti-tumor activity of HJ-PI01 and reduce its toxicity.

CONCLUSION

The newly synthesized compound, HJ-PI01, can induce death receptor/mitochondrial apoptosis and autophagic cell death by targeting Pim-2 in human breast cancer cells in vitro and in vivo.

Pre-clinical evidence of PIM kinase inhibitor activity in BCR-ABL1 unmutated and mutated Philadelphia chromosome-positive (Ph+) leukemias

We investigated the efficacy of targeting the PIM kinase pathway in Philadelphia chromosome-positive (Ph+) leukemias. We provide evidence that inhibition of PIM, with the pan-PIM inhibitor SGI-1776, results in suppression of classic PIM effectors and also elements of the mTOR pathway, suggesting interplay between PIM and mTOR signals. Our data demonstrate that PIM inhibition enhances the effects of imatinib mesylate on Ph+ leukemia cells. We also found that PIM inhibition results in suppression of leukemic cell proliferation and induction of apoptosis of Ph+ leukemia cells, including those resistant to imatinib mesylate. Importantly, inhibition of PIM results in enhanced suppression of primary leukemic progenitors from patients with CML. Altogether these findings suggest that pharmacological PIM targeting may provide a unique therapeutic approach for the treatment of Ph+ leukemias.

Idelalisib Impacts Cell Growth through Inhibiting Translation-Regulatory Mechanisms in Mantle Cell Lymphoma

PURPOSE

PI3K is a critical node in the B-cell receptor pathway, which is responsible for survival and proliferation of B-cell malignancies. Idelalisib, a PI3Kδ-isoform-specific inhibitor, has been approved to treat B-cell malignancies. Although biological activity of the drug has been evaluated, molecular mechanisms and signaling pathway disruption leading to the biological effects of idelalisib are not yet well defined. Prior laboratory reports have identified transcription and translation as the primary events for attenuation of PI3Kα isoform. We hypothesized that PI3Kδ-isoform inhibition by idelalisib should also affect gene transcription and protein translation.

EXPERIMENTAL DESIGN

Using three mantle cell lymphoma cell lines and primary cells from patients, biological consequences such as apoptosis/cell-cycle analysis, as well as RNA/protein synthesis were evaluated. Proteomics analyses (RPPA and immunoblot assays) defined molecular events downstream of PI3K/AKT cassette.

RESULTS

Idelalisib treatment resulted in inhibition of protein synthesis, which correlated with reduction in cell size and cell growth. A moderate loss of viability without any change in cell-cycle profile was observed. Idelalisib treatment inhibited AKT activation, an immediate downstream PI3K effector, and also reduced phosphorylation levels of downstream AKT/mTOR pathway proteins such as PRAS40. In addition, idelalisib treatment impeded activation of the MAPK pathway, and MEK, ERK and p90RSK phosphorylation levels were reduced. Reduction in AKT, PDK1, and MEK phosphorylation correlated with protein synthesis inhibition.

CONCLUSIONS

Collectively, these results clarify the molecular mechanisms of actions and may provide biomarkers and targets for combination with idelalisib in B-cell malignancies. Clin Cancer Res; 23(1); 181-92. ©2016 AACR.

Computational prediction and experimental validation of a novel synthesized pan-PIM inhibitor PI003 and its apoptosis-inducing mechanisms in cervical cancer

PIM protein family, short-lived serine/threonine kinases (PIM1, PIM2 and PIM3), are weak oncogenes but contribute to tumorigenesis as cancer targets. Thus, design of a novel pan-PIM inhibitor is still a challenge for current cancer drug discovery. Herein, we used a Naïve Bayesian model to construct the PIM network and identified Bad and Hsp90 to interact with PIMs. Then, we screened a series of candidate small-molecule compounds targeting PIMs, and subsequently synthesized a novel small-molecule compound PI003 with remarkable anti-proliferative activities in cervical cancer cells. Moreover, we found that PI003 induced apoptosis via the death-receptor and mitochondrial pathways by targeting PIMs and affecting Bad and Hsp90. Combined with microRNA microarray analyses, we demonstrated that some microRNAs such as miR-1296 and miR-1299 could affect PIM1-STAT3 pathway in PI003-induced apoptosis. Finally, we reported that PI003 had remarkable anti-tumor activity and apoptosis-inducing effect in in vivo mouse model. In conclusion, these results demonstrate that PI003, as a novel synthesized pan-PIM inhibitor, induces the death-receptor and mitochondrial apoptosis involved in microRNA regulation, and also possessed remarkable anti-tumor activity and apoptosis-inducing effect in vivo. Thus, these findings would shed light on discovering more potential new small-molecule pan-PIM inhibitors in future cervical cancer therapy.

Protein profiling identifies mTOR pathway modulation and cytostatic effects of Pim kinase inhibitor, AZD1208, in acute myeloid leukemia

Pim kinases phosphorylate and regulate a number of key acute myeloid leukemia (AML) cell survival proteins, and Pim inhibitors have recently entered clinical trial for hematological malignancies. AZD1208 is a small molecule pan-Pim kinase inhibitor and AZD1208 treatment resulted in growth inhibition and cell size reduction in AML cell lines including FLT3-WT (OCI-AML-3, KG-1a, and MOLM-16) and FLT3-ITD mutated (MOLM-13 and MV-4-11). There was limited apoptosis induction (<10% increase) in the AML cell lines evaluated with up to 3 μM AZD1208 for 24 h, suggesting that growth inhibition is not through apoptosis induction. Using reverse phase protein array (RPPA) and immunoblot analysis, we identified that AZD1208 resulted in suppression of mTOR signaling, including inhibition of protein phosphorylation of mTOR (Ser2448), p70S6K (Thr389), S6 (Ser235/236), and 4E-BP1 (Ser65). Consistent with mTOR inhibition, there was also a reduction in protein synthesis that correlated with cell size reduction and growth inhibition with AZD1208; our study provides insights into the mechanism of AZD1208.

Development and Application of a High-Throughput Fluorescence Polarization Assay to Target Pim Kinases

Pim proteins consisting of three isoforms (Pim-1, Pim-2, and Pim-3) are a family of serine/threonine kinases that regulate fundamental cellular responses such as cell growth, differentiation, and apoptosis. Overexpression of the Pim kinases has been linked to a wide variety of hematological and solid tumors. Thus, all three Pim kinases have been studied as promising targets for anticancer therapy. Here, we report on the development and optimization of an immobilized metal ion affinity partitioning (IMAP) fluorescence polarization (FP) method for Pim kinases. In this homogeneous 384-well assay method, fluorescein-labeled phosphopeptides are captured on cationic nanoparticles through interactions with immobilized trivalent metals, resulting in high polarization values. The apparent Km values for adenosine triphosphate (ATP) were determined to be 45 ± 7, 6.4 ± 2, and 29 ± 5 μM for Pim-1, Pim-2, and Pim-3, respectively. The assay yielded robustness with Z'-factors of >0.75 and low day-to-day variability (CV <5%) for all three Pim kinases. The IMAP FP assay was further validated by determining IC50 values for staurosporine and a known Pim inhibitor. We have also used an IMAP FP assay to examine whether compound 1, an ATP mimetic inhibitor designed through structure-based drug design, is indeed an ATP-competitive inhibitor of Pim kinases. Kinetic analysis based on Lineweaver-Burk plots showed that the inhibition mechanism of compound 1 is ATP competitive against all three Pim isoforms. The optimized IMAP assay for Pim kinases not only allows for high-throughput screening but also facilitates the characterization of novel Pim inhibitors for drug development.

Cyclin-Dependent Kinase Inhibitor P1446A Induces Apoptosis in a JNK/p38 MAPK-Dependent Manner in Chronic Lymphocytic Leukemia B-Cells

CDK (cyclin-dependent kinase) inhibitors have shown remarkable activity in CLL, where its efficacy has been linked to inhibition of the transcriptional CDKs (7 and 9) and deregulation of RNA polymerase and short-lived pro-survival proteins such as MCL1. Furthermore, ER (endoplasmic reticulum) stress has been implicated in CDK inhibition in CLL. Here we conducted a pre-clinical study of a novel orally active kinase inhibitor P1446A in CLL B-cells. P1446A inhibited CDKs at nanomolar concentrations and induced rapid apoptosis of CLL cells in vitro, irrespective of chromosomal abnormalities or IGHV mutational status. Apoptosis preceded inactivation of RNA polymerase, and was accompanied by phosphorylation of stress kinases JNK (c-Jun N-terminal kinase) and p38 MAPK (mitogen-activated protein kinase). Pharmacologic inhibitors of JNK/p38 MAPK conferred protection from P1446A-mediated apoptosis. Treatment with P1446A led to a dramatic induction of NOXA in a JNK-dependent manner, and sensitized CLL cells to ABT-737, a BH3-mimetic. We observed concurrent activation of apoptosis stress-inducing kinase 1 (ASK1) and its interaction with inositol-requiring enzyme 1 (IRE1) and tumor necrosis factor receptor-associated factor 2 (TRAF2) in CLL cells treated with P1446A, providing insights into upstream regulation of JNK in this setting. Consistent with previous reports on limited functionality of ER stress mechanism in CLL cells, treatment with P1446A failed to induce an extensive unfolded protein response. This study provides rationale for additional investigations of P1446A in CLL.

Patterns and Significance of PIM Kinases in Urothelial Carcinoma

BACKGROUND

The Provirus integrating site Moloney murine leukemia virus (Pim) family are proteins with serine/threonine kinase activity. Studies have demonstrated overexpression of Pims in cancer. To our knowledge, only a single study has examined Pim-1 in urothelial carcinoma. The aim of this investigation was to evaluate Pim-1, Pim-2, and Pim-3 in urothelial carcinoma and assess for expression that may contribute to disease progression and serve as a site for targeted therapy.

METHODS

This retrospective study included 137 cases taken from specimens from the University of Utah, Department of Pathology (2008 to 2011). Tissue was stained with antibodies against Pim-1, Pim-2, and Pim-3. Cases were classified into 3 groups, based upon current World Health Organization criteria (invasive high-grade urothelial carcinoma [IHG] [n=84], noninvasive high-grade urothelial carcinoma/carcinoma in situ [n=32], and noninvasive low-grade urothelial carcinoma [NILG] [n=21]). Cases were scored and recorded as positive or negative on the basis of the percentage of cells with cytoplasmic and/or nuclear staining.

RESULTS

NILG showed higher expression of Pim-1 (relative expression rate [RER]=2.28; 95% confidence interval [CI], 0.183-0.764) and Pim-3 (RER=3.06; 95% CI, 0.423-0.816) compared with other lesions. IHG had lower expression of Pim-1 (RER=0.31; 95% CI, 0.401-0.844) and Pim-3 (RER=0.354; 95% CI, 0.322-0.816) and noninvasive high-grade urothelial carcinoma (NIHG) demonstrated increased expression of Pim-1 and (RER=2.09; 95% CI, 0.124-0.739) and Pim-2 (RER=1.70; 95% CI, 0.151-0.591). At least 1 Pim kinase protein was expressed at the following rates: 49% in IHG, 66% in NIHG, and 76% in NILG.

CONCLUSION

A high percentage of urothelial carcinomas express Pim kinases. Pim expression differs in NILG, NIHG, and IHG lesions.

Combination of Pim kinase inhibitors and Bcl-2 antagonists in chronic lymphocytic leukemia cells

The Pim proteins are Ser/Thr kinases over-expressed in several hematological malignancies such as chronic lymphocytic leukemia (CLL) and some solid cancers like prostate cancer. Several small molecules have been developed to inhibit these kinases. In prostate cancer cell lines, the Pim kinase inhibitor SMI-4a and the Bcl-2 antagonist ABT-737 resulted in synergistic cytotoxicity. Akin to prostate cancer cells, CLL lymphocytes over-express Pim and Bcl-2 proteins. It was hypothesized that similar cytotoxic interaction should be observed in CLL. This study evaluated the in vitro cytotoxic effect of three Pim kinase inhibitors (AZD1208, SGI-1776 and SMI-4a) combined with Bcl-2 antagonists (ABT-737 or ABT-199) in malignant CLL lymphocytes. Data indicated Pim kinase inhibitors in combination with ABT-737 or ABT-199 resulted mostly in additive cytotoxicity with a few synergistic responses; however, the extent of synergism was less robust than that observed previously in prostate cancer cell lines treated with SMI-4a and ABT-737.

The mRNA-binding protein HuR promotes hypoxia-induced chemoresistance through posttranscriptional regulation of the proto-oncogene PIM1 in pancreatic cancer cells

Previously, it has been shown that pancreatic ductal adenocarcinoma (PDA) tumors exhibit high levels of hypoxia, characterized by low oxygen pressure (pO2) and decreased O2 intracellular perfusion. Chronic hypoxia is strongly associated with resistance to cytotoxic chemotherapy and chemoradiation in an understudied phenomenon known as hypoxia-induced chemoresistance. The hypoxia-inducible, pro-oncogenic, serine-threonine kinase PIM1 (Proviral Integration site for Moloney murine leukemia virus 1) has emerged as a key regulator of hypoxia-induced chemoresistance in PDA and other cancers. Although its role in therapeutic resistance has been described previously, the molecular mechanism behind PIM1 overexpression in PDA is unknown. Here, we demonstrate that cis-acting AU-rich elements (ARE) present within a 38-base pair region of the PIM1 mRNA 3'-untranslated region mediate a regulatory interaction with the mRNA stability factor HuR (Hu antigen R) in the context of tumor hypoxia. Predominantly expressed in the nucleus in PDA cells, HuR translocates to the cytoplasm in response to hypoxic stress and stabilizes the PIM1 mRNA transcript, resulting in PIM1 protein overexpression. A reverse-phase protein array revealed that HuR-mediated regulation of PIM1 protects cells from hypoxic stress through phosphorylation and inactivation of the apoptotic effector BAD and activation of MEK1/2. Importantly, pharmacological inhibition of HuR by MS-444 inhibits HuR homodimerization and its cytoplasmic translocation, abrogates hypoxia-induced PIM1 overexpression and markedly enhances PDA cell sensitivity to oxaliplatin and 5-fluorouracil under physiologic low oxygen conditions. Taken together, these results support the notion that HuR has prosurvival properties in PDA cells by enabling them with growth advantages in stressful tumor microenvironment niches. Accordingly, these studies provide evidence that therapeutic disruption of HuR's regulation of PIM1 may be a key strategy in breaking an elusive chemotherapeutic resistance mechanism acquired by PDA cells that reside in hypoxic PDA microenvironments.

Targeting the Pim kinases in multiple myeloma

Multiple myeloma (MM) is a plasma cell malignancy that remains incurable. Novel treatment strategies to improve survival are urgently required. The Pims are a small family of serine/threonine kinases with increased expression across the hematological malignancies. Pim-2 shows highest expression in MM and constitutes a promising therapeutic target. It is upregulated by the bone marrow microenvironment to mediate proliferation and promote MM survival. Pim-2 also has a key role in the bone destruction typically seen in MM. Additional putative roles of the Pim kinases in MM include trafficking of malignant cells, promoting oncogenic signaling in the hypoxic bone marrow microenvironment and mediating resistance to therapy. A number of Pim inhibitors are now under development with lead compounds entering the clinic. The ATP-competitive Pim inhibitor LGH447 has recently been reported to have single agent activity in MM. It is anticipated that Pim inhibition will be of clinical benefit in combination with standard treatments and/or with novel drugs targeting other survival pathways in MM.

Investigating pyridazine and phthalazine exchange in a series of iridium complexes in order to define their role in the catalytic transfer of magnetisation from para-hydrogen

Reaction of [Ir(IMes)(COD)Cl] with pyridazine (pdz) or phthalazine (phth) and H₂ results in the formation of the para-hydrogen magnetisation transfer catalysts [Ir(H)₂(IMes)(pdz)₃]Cl and [Ir(H)₂(IMes)(phth)₃]Cl.

The reaction of [Ir(IMes)(COD)Cl], [IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene, COD = 1,5-cyclooctadiene] with pyridazine (pdz) and phthalazine (phth) results in the formation of [Ir(COD)(IMes)(pdz)]Cl and [Ir(COD)(IMes)(phth)]Cl. These two complexes are shown by nuclear magnetic resonance (NMR) studies to undergo a haptotropic shift which interchanges pairs of protons within the bound ligands. When these complexes are exposed to hydrogen, they react to form [Ir(H)₂(COD)(IMes)(pdz)]Cl and [Ir(H)₂(COD)(IMes)(phth)]Cl, respectively, which ultimately convert to [Ir(H)₂(IMes)(pdz)₃]Cl and [Ir(H)₂(IMes)(phth)₃]Cl, as the COD is hydrogenated to form cyclooctane. These two dihydride complexes are shown, by NMR, to undergo both full N-heterocycle dissociation and a haptotropic shift, the rates of which are affected by both steric interactions and free ligand pK_a values. The use of these complexes as catalysts in the transfer of polarisation from para-hydrogen to pyridazine and phthalazine via signal amplification by reversible exchange (SABRE) is explored. The possible future use of drugs which contain pyridazine and phthalazine motifs as in vivo or clinical magnetic resonance imaging probes is demonstrated; a range of NMR and phantom-based MRI measurements are reported.

Synthesis and Biological Evaluation of Pyrazolo[1,5-a]pyrimidine Compounds as Potent and Selective Pim-1 Inhibitors

Pim-1 has emerged as an attractive target for developing therapeutic agents for treating disorders involving abnormal cell growth, especially cancers. Herein we present lead optimization, chemical synthesis and biological evaluation of pyrazolo[1,5-a]pyrimidine compounds as potent and selective inhibitors of Pim-1 starting from a hit from virtual screening. These pyrazolo[1,5-a]pyrimidine compounds strongly inhibited Pim-1 and Flt-3 kinases. Selected compounds suppressed both the phosphorylation of BAD protein in a cell-based assay and 2-dimensional colony formation in a clonogenic cell survival assay at submicromolar potency, suggesting that cellular activity was mediated through inhibition of Pim-1. Moreover, these Pim-1 inhibitors did not show significant hERG inhibition at 30 μM concentration. The lead compound proved to be highly selective against a panel of 119 oncogenic kinases, indicating it had an improved safety profile compared with the first generation Pim-1 inhibitor SGI-1776.

Targeting Pim kinases for cancer treatment: opportunities and challenges

Pim oncogenes are highly expressed in many types of hematological and solid cancers. Pim kinases regulate the network of signaling pathways that are critical for tumorigenesis and development, making Pim kinases the attractive drug targets. Currently, two approaches have been employed in designing Pim kinase inhibitors: ATP-mimetics and non-ATP mimetics; but all target the ATP-binding pocket and are ATP-competitive. In this review, we summarize the current progress in understanding the Pim-related structure and biology, and provide insights into the binding modes of some prototypical Pim-1 inhibitors. The challenges as well as opportunities are highlighted for development of Pim kinase inhibitors as potential anticancer agents.

The discovery of novel 3-(pyrazin-2-yl)-1H-indazoles as potent pan-Pim kinase inhibitors

The three Pim kinases are a small family of serine/threonine kinases regulating several signaling pathways that are fundamental to tumorigenesis. As such, the Pim kinases are a very attractive target for pharmacological inhibition in cancer therapy. Herein, we describe our efforts toward the development of a potent, pan-Pim inhibitor. The synthesis and hit-to-lead SAR development from a 3-(pyrazin-2-yl)-1H-indazole derived hit 2 to the identification of a series of potent, pan-Pim inhibitors such as 13o are described.

PIM kinases: an overview in tumors and recent advances in pancreatic cancer

The PIM kinases represent a family of serine/threonine kinases, which is composed of three different members (PIM1, PIM2 and PIM3). Aberrant expression of PIM kinases is observed in variety of tumors, including pancreatic cancer. The PIM kinases play pivotal roles in the regulation of cell cycle, apoptosis, properties of stem cells, metabolism, autophagy, drug resistance and targeted therapy. The roles of PIM kinases in pancreatic cancer include the regulation of proliferation, apoptosis, cell cycle, formation, angiogenesis and prediction prognosis. Blocking the activities of PIM kinases could prevent pancreatic cancer development. PIM kinases may be a novel target for cancer therapy.

Pim kinases in hematological malignancies: where are we now and where are we going?

The proviral insertion in murine (PIM) lymphoma proteins are a serine/threonine kinase family composed of three isoformes: Pim-1, Pim-2 and Pim-3. They play a critical role in the control of cell proliferation, survival, homing and migration. Recently, overexpression of Pim kinases has been reported in human tumors, mainly in hematologic malignancies. In vitro and in vivo studies have confirmed their oncogenic potential. Indeed, PIM kinases have shown to be involved in tumorgenesis, to enhance tumor growth and to induce chemo-resistance, which is why they have become an attractive therapeutic target for cancer therapy. Novel molecules inhibiting Pim kinases have been evaluated in preclinical studies, demonstrating to be effective and with a favorable toxicity profile. Given the promising results, some of these compounds are currently under investigation in clinical trials. Herein, we provide an overview of the biological activity of PIM-kinases, their role in hematologic malignancies and future therapeutic opportunities.

Flow sorting and exome sequencing reveal the oncogenome of primary Hodgkin and Reed-Sternberg cells

Classical Hodgkin lymphoma (cHL) is characterized by sparsely distributed Hodgkin and Reed-Sternberg (HRS) cells amid reactive host background, complicating the acquisition of neoplastic DNA without extensive background contamination. We overcame this limitation by using flow-sorted HRS and intratumor T cells and optimized low-input exome sequencing of 10 patient samples to reveal alterations in genes involved in antigen presentation, chromosome integrity, transcriptional regulation, and ubiquitination. β-2-microglobulin (B2M) is the most commonly altered gene in HRS cells, with 7 of 10 cases having inactivating mutations that lead to loss of major histocompatibility complex class I (MHC-I) expression. Enforced wild-type B2M expression in a cHL cell line restored MHC-I expression. In an extended cohort of 145 patients, the absence of B2M protein in the HRS cells was associated with lower stage of disease, younger age at diagnosis, and better overall and progression-free survival. B2M-deficient cases encompassed most of the nodular sclerosis subtype cases and only a minority of mixed cellularity cases, suggesting that B2M deficiency determines the tumor microenvironment and may define a major subset of cHL that has more uniform clinical and morphologic features. In addition, we report previously unknown genetic alterations that may render selected patients sensitive to specific targeted therapies.

PIM kinases as potential therapeutic targets in a subset of peripheral T cell lymphoma cases

Currently, there is no efficient therapy for patients with peripheral T cell lymphoma (PTCL). The Proviral Integration site of Moloney murine leukemia virus (PIM) kinases are important mediators of cell survival. We aimed to determine the therapeutic value of PIM kinases because they are overexpressed in PTCL patients, T cell lines and primary tumoral T cells. PIM kinases were inhibited genetically (using small interfering and short hairpin RNAs) and pharmacologically (mainly with the pan-PIM inhibitor (PIMi) ETP-39010) in a panel of 8 PTCL cell lines. Effects on cell viability, apoptosis, cell cycle, key proteins and gene expression were evaluated. Individual inhibition of each of the PIM genes did not affect PTCL cell survival, partially because of a compensatory mechanism among the three PIM genes. In contrast, pharmacological inhibition of all PIM kinases strongly induced apoptosis in all PTCL cell lines, without cell cycle arrest, in part through the induction of DNA damage. Therefore, pan-PIMi synergized with Cisplatin. Importantly, pharmacological inhibition of PIM reduced primary tumoral T cell viability without affecting normal T cells ex vivo. Since anaplastic large cell lymphoma (ALK+ ALCL) cell lines were the most sensitive to the pan-PIMi, we tested the simultaneous inhibition of ALK and PIM kinases and found a strong synergistic effect in ALK+ ALCL cell lines. Our findings suggest that PIM kinase inhibition could be of therapeutic value in a subset of PTCL, especially when combined with ALK inhibitors, and might be clinically beneficial in ALK+ ALCL.

Heat shock protein 90 inhibitor NVP-AUY922 exerts potent activity against adult T-cell leukemia-lymphoma cells

Adult T-cell leukemia–lymphoma (ATL), an aggressive neoplasm etiologically associated with HTLV-1, is a chemoresistant malignancy. Heat shock protein 90 (HSP90) is involved in folding and functions as a chaperone for multiple client proteins, many of which are important in tumorigenesis. In this study, we examined NVP-AUY922 (AUY922), a second generation isoxazole-based non-geldanamycin HSP90 inhibitor, and confirmed its effects on survival of ATL-related cell lines. Analysis using FACS revealed that AUY922 induced cell-cycle arrest and apoptosis; it also inhibited the growth of primary ATL cells, but not of normal PBMCs. AUY922 caused strong upregulation of HSP70, a surrogate marker of HSP90 inhibition, and a dose-dependent decrease in HSP90 client proteins associated with cell survival, proliferation, and cell cycle in the G₁ phase, including phospho-Akt, Akt, IKKα, IKKβ, IKKγ, Cdk4, Cdk6, and survivin. Interestingly, AUY922 induced downregulation of the proviral integration site for Moloney murine leukemia virus (PIM) in ATL cells. The PIM family (PIM-1, -2, -3) is made up of oncogenes that encode a serine/threonine protein kinase family. As PIM kinases have multiple functions involved in cell proliferation, survival, differentiation, apoptosis, and tumorigenesis, their downregulation could play an important role in AUY922-induced death of ATL cells. In fact, SGI-1776, a pan-PIM kinase inhibitor, successfully inhibited the growth of primary ATL cells as well as ATL-related cell lines. Our findings suggest that AUY922 is an effective therapeutic agent for ATL, and PIM kinases may be a novel therapeutic target.

MYC deregulation in lymphoid tumors: molecular mechanisms, clinical consequences and therapeutic implications

MYC is one of the most frequently deregulated oncogenes in human malignancies. It encodes a leucine zipper transcription factor that modulates a broad spectrum of cellular genes responsible for enhancing cell proliferation, cellular metabolism, growth, angiogenesis, metastasis, genomic instability, stem cell self-renewal and reduced differentiation. MYC functions predominantly as an amplifier of expression of already active genes, potentiating the pre-existing transcriptional program, although it can also repress certain transcriptional targets. In mouse models, MYC induces lymphomas, but requires cooperation with other lesions, including inactivation of the p53 pathway, structural alterations of BCL2 family members, or increased PI3K activity. In human B-cell tumors, MYC rearrangements involving the 8q24 region and immunoglobulin heavy or light genes are a hallmark of Burkitt lymphoma (BL), but can also occur in other lymphoid malignancies, that include diffuse large B-cell lymphoma (DLBCL), B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and Burkitt lymphoma (BCLU), plasma cell myeloma (PCM), mantle cell lymphoma (MCL) and plasmablastic lymphoma. For non-BL lymphoid malignancies, MYC fusions represent secondary genetic events and exist in the context of complex karyotypes. Regardless of the mechanism deregulating MYC, lymphomas over-expressing MYC are addicted to this oncogene, highlighting the potential clinical utility of MYC targeting strategies. Several promising approaches for pharmaceutical intervention have been suggested which are now in preclinical or clinical development. Herein, we therefore review the molecular pathogenetic mechanisms associated with MYC deregulation in human B-cell lymphomas and their implications for therapies targeting MYC.