Inhibition of Pim kinases triggers a broad antiviral activity by affecting innate immunity and via the PI3K-Akt-mTOR axis the endolysosomal system

Zoonoses such as ZIKV and SARS-CoV-2 pose a severe risk to global health. There is urgent need for broad antiviral strategies based on host-targets filling gaps between pathogen emergence and availability of therapeutic or preventive strategies. Significant reduction of pathogen titers decreases spread of infections and thereby ensures health systems not being overloaded and public life to continue. Based on previously observed interference with FGFR1/2-signaling dependent impact on interferon stimulated gene (ISG)-expression, we identified Pim kinases as promising druggable cellular target. We therefore focused on analyzing the potential of pan-Pim kinase inhibition to trigger a broad antiviral response. The pan-Pim kinase inhibitor AZD1208 exerted an extraordinarily high antiviral effect against various ZIKV isolates, SARS-CoV-2 and HBV. This was reflected by strong reduction in viral RNA, proteins and released infectious particles. Especially in case of SARS-CoV-2, AZD1208 led to a complete removal of viral traces in cells. Kinome-analysis revealed vast changes in kinase landscape upon AZD1208 treatment, especially for inflammation and the PI3K/Akt-pathway. For ZIKV, a clear correlation between antiviral effect and increase in ISG-expression was observed. Based on a cell culture model with impaired ISG-induction, activation of the PI3K-Akt-mTOR axis, leading to major changes in the endolysosomal equilibrium, was identified as second pillar of the antiviral effect triggered by AZD1208-dependent Pim kinase inhibition, also against HBV. We identified Pim-kinases as cellular target for a broad antiviral activity. The antiviral effect exerted by inhibition of Pim kinases is based on at least two pillars: innate immunity and modulation of the endolysosomal system.

Dibenzofuran Derivatives Inspired from Cercosporamide as Dual Inhibitors of Pim and CLK1 Kinases

Pim kinases (proviral integration site for Moloney murine leukemia virus kinases) are overexpressed in various types of hematological malignancies and solid carcinomas, and promote cell proliferation and survival. Thus, Pim kinases are validated as targets for antitumor therapy. In this context, our combined efforts in natural product-inspired library generation and screening furnished very promising dibenzo[b,d]furan derivatives derived from cercosporamide. Among them, lead compound 44 was highlighted as a potent Pim-1/2 kinases inhibitor with an additional nanomolar IC₅₀ value against CLK1 (cdc2-like kinases 1) and displayed a low micromolar anticancer potency towards the MV4-11 (AML) cell line, expressing high endogenous levels of Pim-1/2 kinases. The design, synthesis, structure-activity relationship, and docking studies are reported herein and supported by enzyme, cellular assays, and Galleria mellonella larvae testing for acute toxicity.

New Quinoxaline Derivatives as Dual Pim-1/2 Kinase Inhibitors: Design, Synthesis and Biological Evaluation

Proviral integration site for Moloney murine leukemia virus (Pim)-1/2 kinase overexpression has been identified in a variety of hematologic (e.g., multiple myeloma or acute myeloid leukemia (AML)) and solid (e.g., colorectal carcinoma) tumors, playing a key role in cancer progression, metastasis, and drug resistance, and is linked to poor prognosis. These kinases are thus considered interesting targets in oncology. We report herein the design, synthesis, structure–activity relationships (SAR) and in vitro evaluations of new quinoxaline derivatives, acting as dual Pim1/2 inhibitors. Two lead compounds (5c and 5e) were then identified, as potent submicromolar Pim-1 and Pim-2 inhibitors. These molecules were also able to inhibit the growth of the two human cell lines, MV4-11 (AML) and HCT-116 (colorectal carcinoma), expressing high endogenous levels of Pim-1/2 kinases.

PAI1 is a Marker of Bad Prognosis in Rectal Cancer but Predicts a Better Response to Treatment with PIM Inhibitor AZD1208

Colorectal cancer (CRC) is the third most common cancer worldwide. The standard treatment in locally advanced rectal cancer is preoperative radiation alone or in combination with chemotherapy, followed by adjuvant chemotherapy. Rectal cancer is highly lethal, with only 20% of patients showing a complete remission (by RECIST) after standard treatment, although they commonly show local or systemic relapse likely due to its late detection and high chemotherapy resistance, among other reasons. Here, we explored the role of PAI1 (Serpin E1) in rectal cancer through the analyses of public patient databases, our own cohort of locally advanced rectal cancer patients and a panel of CRC cell lines. We showed that PAI1 expression is upregulated in rectal tumors, which is associated with decreased overall survival and increased metastasis and invasion in advanced rectal tumors. Accordingly, PAI1 expression is correlated with the expression of (Epithelial-to-Mesenchymal Transition) EMT-associated genes and genes encoding drug targets, including the tyrosine kinases PDGFRb, PDGFRa and FYN, the serine/threonine kinase PIM1 and BRAF. In addition, we demonstrate that cells expressing PAI1 protein are more sensitive to the PIM inhibitor AZD1208, suggesting that PAI1 could be used to predict response to treatment with PIM inhibitors and to complement radiotherapy in rectal tumors.

RNA-Seq analysis reveals that spring viraemia of carp virus induces a broad spectrum of PIM kinases in zebrafish kidney that promote viral entry

PIM kinases are a family of serine/threonine protein kinases that potentiate the progression of the cell cycle and inhibit apoptosis. Because of this, they are considered to be proto-oncogenes, and they represent an interesting target for the development of anticancer drugs. In mammals, three PIM kinases exist (PIM-1, PIM-2 and PIM-3), and different inhibitors have been developed to block their activity. In addition to their involvement in cancer, some publications have reported that the PIM kinases have pro-viral activity, and different mechanisms where PIM kinases favour viral infections have been proposed. Zebrafish possess more than 300 Pim kinase members in their genome, and by using RNA-Seq analysis, we found a high number of Pim kinase genes that were significantly induced after infection with spring viraemia of carp virus (SVCV). Moreover, analysis of the miRNAs modulated by this infection revealed that some of them could be involved in the post-transcriptional regulation of Pim kinase abundance. To elucidate the potential role of the 16 overexpressed Pim kinases in the infectivity of SVCV, we used three different pan-PIM kinase inhibitors (SGI-1776, INCB053914 and AZD1208), and different experiments were conducted both in vitro and in vivo. We observed that the PIM kinase inhibitors had a protective effect against SVCV, indicating that, similar to what is observed in mammals, PIM kinases are beneficial for the virus in zebrafish. Moreover, zebrafish Pim kinases seem to facilitate viral entry into the host cells because when ZF4 cells were pre-incubated with the virus and then were treated with the inhibitors, the protective effect of the inhibitors was abrogated. Although more investigation is necessary, these results show that pan-PIM kinase inhibitors could serve as a useful treatment for preventing the spread of viral diseases.

Phosphorylation of Notch1 by Pim kinases promotes oncogenic signaling in breast and prostate cancer cells

Tumorigenesis is a multistep process involving co-operation between several deregulated oncoproteins. In this study, we unravel previously unrecognized interactions and crosstalk between Pim kinases and the Notch signaling pathway, with implications for both breast and prostate cancer. We identify Notch1 and Notch3, but not Notch2, as novel Pim substrates and demonstrate that for Notch1, the serine residue 2152 is phosphorylated by all three Pim family kinases. This target site is located in the second nuclear localization sequence (NLS) of the Notch1 intracellular domain (N1ICD), and is shown to be important for both nuclear localization and transcriptional activity of N1ICD. Phosphorylation-dependent stimulation of Notch1 signaling promotes migration of prostate cancer cells, balances glucose metabolism in breast cancer cells, and supports in vivo growth of both types of cancer cells on chick embryo chorioallantoic membranes. Furthermore, Pim-induced growth of orthotopic prostate xenografts in mice is associated with enhanced nuclear Notch1 activity. Finally, simultaneous inhibition of Pim and Notch abrogates the cellular responses more efficiently than individual treatments, opening up new vistas for combinatorial cancer therapy.

FLT3-ITD induces expression of Pim kinases through STAT5 to confer resistance to the PI3K/Akt pathway inhibitors on leukemic cells by enhancing the mTORC1/Mcl-1 pathway

FLT3-ITD is the most frequent tyrosine kinase mutation in acute myeloid leukemia (AML) associated with poor prognosis. We previously reported that activation of STAT5 confers resistance to PI3K/Akt inhibitors on the FLT3-ITD-positive AML cell line MV4-11 and 32D cells driven by FLT3-ITD (32D/ITD) but not by FLT3 mutated in the tyrosine kinase domain (32D/TKD). Here, we report the involvement of Pim kinases expressed through STAT5 activation in acquisition of this resistance. The specific pan-Pim kinase inhibitor AZD1208 as well as PIM447 in combination with the PI3K inhibitor GDC-0941 or the Akt inhibitor MK-2206 cooperatively downregulated the mTORC1/4EBP1 pathway, formation of the eIF4E/eIF4G complex, and Mcl-1 expression leading to activation of Bak and Bax to induce caspase-dependent apoptosis synergistically in these cells. These cooperative effects were enhanced or inhibited by knock down of mTOR or expression of its activated mutant, respectively. Overexpression of Mcl-1 conferred the resistance on 32D/ITD cells to combined inhibition of the PI3K/Akt pathway and Pim kinases, while the Mcl-1-specific BH3 mimetic A-1210477 conquered the resistance of MV4-11 cells to GDC-0941. Furthermore, overexpression of Pim-1 in 32D/TKD enhanced the mTORC1/Mcl-1 pathway and partially protected it from the PI3K/Akt inhibitors or the FLT3 inhibitor gilteritinib to confer the resistance to PI3K/Akt inhibitors. Finally, AZD1208 and GDC-0941 cooperatively inhibited the mTORC1/Mcl-1 pathway and reduced viable cell numbers of primary AML cells from some FLT3-ITD positive cases. Thus, Pim kinases may protect the mTORC1/4EBP1/Mcl-1 pathway to confer the resistance to the PI3K/Akt inhibitors on FLT3-ITD cells and represent promising therapeutic targets.

Probing Mechanisms of CYP3A Time-Dependent Inhibition Using a Truncated Model System

Time-dependent inhibition (TDI) of cytochrome P450 (CYP) enzymes may incur serious undesirable drug-drug interactions and in rare cases drug-induced idiosyncratic toxicity. The reactive metabolites are often generated through multiple sequential biotransformations and form adducts with CYP enzymes to inactivate their function. The complexity of these processes makes addressing TDI liability very challenging. Strategies to mitigate TDI are therefore highly valuable in discovering safe therapies to benefit patients. In this Letter, we disclose our simplified approach toward addressing CYP3A TDI liabilities, guided by metabolic mechanism hypotheses. By adding a methyl group onto the α carbon of a basic amine, TDI activities of both the truncated and full molecules (7a and 11) were completely eliminated. We propose that truncated molecules, albeit with caveats, may be used as surrogates for full molecules to investigate TDI.

Genetic Modeling of PIM Proteins in Cancer: Proviral Tagging and Cooperation with Oncogenes, Tumor Suppressor Genes, and Carcinogens

The PIM proteins, which were initially discovered as proviral insertion sites in Moloney-murine leukemia virus infection, are a family of highly homologous serine/threonine kinases that have been reported to be overexpressed in hematological malignancies and solid tumors. The PIM proteins have also been associated with metastasis and overall treatment responses and implicated in the regulation of apoptosis, metabolism, the cell cycle, and homing and migration, which makes these proteins interesting targets for anti-cancer drug discovery. The use of retroviral insertional mutagenesis and refined approaches such as complementation tagging has allowed the identification of myc, pim, and a third group of genes (including bmi1 and gfi1) as complementing genes in lymphomagenesis. Moreover, mouse modeling of human cancer has provided an understanding of the molecular pathways that are involved in tumor initiation and progression at the physiological level. In particular, genetically modified mice have allowed researchers to further elucidate the role of each of the Pim isoforms in various tumor types. PIM kinases have been identified as weak oncogenes because experimental overexpression in lymphoid tissue, prostate, and liver induces tumors at a relatively low incidence and with a long latency. However, very strong synergistic tumorigenicity between Pim1/2 and c-Myc and other oncogenes has been observed in lymphoid tissues. Mouse models have also been used to study whether the inhibition of specific PIM isoforms is required to prevent carcinogen-induced sarcomas, indicating that the absence of Pim2 and Pim3 greatly reduces sarcoma growth and bone invasion; the extent of this effect is similar to that observed in the absence of all three isoforms. This review will summarize some of the animal models that have been used to understand the isoform-specific contribution of PIM kinases to tumorigenesis.