PIM1 and MYC: a changing relationship?

Chemical Information and Computational Modeling of Targeting Hybrid Nucleic Acid Structures of PIM1 Sequences by Synthetic Pyrrole-Imidazole Carboxamide Drugs

DNA can adopt various distinct structural motifs, such as quadruplex, duplex, i-motifs, etc. which have multifarious applications in biomedical therapeutics. Quadruplex-duplex hybrids (QDHs) consist of the juxtaposed quadruplex and duplex motifs and are thermally stable and biologically relevant. Selective binding toward these secondary structures plays an important role in the evaluation of the structure-specific ligands. Herein, several small molecules containing anthraquinone conjugated oligopyrrole, oligoimidazole, and pyrrole-imidazole derivatives have been screened for the binding of the quadruplex-duplex nucleic acid hybrids formed in PIM1 sequences through docking and molecular dynamics (MD) simulation studies. The binding interaction of the anthraquinone polypyrrole ligands has also been checked by performing different biophysical experiments. PIM1, being a coactivator of the MYC oncogene, can be targeted by these small molecules to control MYC expression which is overexpressed in the majority of human cancer cells. Accordingly, these cancer cell-specific and blood-compatible anthraquinone conjugated oligopyrrole ligands can be employed for anticancer therapeutic applications. Thus, the structure-activity relationship (SAR) of the screened ligands manifested prudent structural information for designing PIM1 QDHs targeting small molecules.

Ribosomal Biogenesis and Translational Flux Inhibition by the Selective Inhibitor of Nuclear Export (SINE) XPO1 Antagonist KPT-185

Mantle cell lymphoma (MCL) is an aggressive B-cell lymphoma characterized by the aberrant expression of several growth-regulating, oncogenic effectors. Exportin 1 (XPO1) mediates the nucleocytoplasmic transport of numerous molecules including oncogenic growth-regulating factors, RNAs, and ribosomal subunits. In MCL cells, the small molecule KPT-185 blocks XPO1 function and exerts anti-proliferative effects. In this study, we investigated the molecular mechanisms of this putative anti-tumor effect on MCL cells using cell growth/viability assays, immunoblotting, gene expression analysis, and absolute quantification proteomics. KPT-185 exhibited a p53-independent anti-lymphoma effect on MCL cells, by suppression of oncogenic mediators (e.g., XPO1, cyclin D1, c-Myc, PIM1, and Bcl-2 family members), repression of ribosomal biogenesis, and downregulation of translation/chaperone proteins (e.g., PIM2, EEF1A1, EEF2, and HSP70) that are part of the translational/transcriptional network regulated by heat shock factor 1. These results elucidate a novel mechanism in which ribosomal biogenesis appears to be a key component through which XPO1 contributes to tumor cell survival. Thus, we propose that the blockade of XPO1 could be a promising, novel strategy for the treatment of MCL and other malignancies overexpressing XPO1.

Pim1 kinase is upregulated in glioblastoma multiforme and mediates tumor cell survival

BACKGROUND

The current therapy for glioblastoma multiforme (GBM), the most aggressive and common primary brain tumor of adults, involves surgery and a combined radiochemotherapy that controls tumor progression only for a limited time window. Therefore, the identification of new molecular targets is highly necessary. Inhibition of kinases has become a standard of clinical oncology, and thus the oncogenic kinase Pim1 might represent a promising target for improvement of GBM therapy.

METHODS

Expression of Pim1 and associated signaling molecules was analyzed in human GBM samples, and the potential role of this kinase in patients' prognosis was evaluated. Furthermore, we analyzed the in vivo role of Pim1 in GBM cell growth in an orthotopic mouse model and examined the consequences of Pim1 inhibition in vitro to clarify underlying pathways.

RESULTS

In comparison with normal brain, a strong upregulation of Pim1 was demonstrated in human GBM samples. Notably, patients with short overall survival showed a significantly higher Pim1 expression compared with GBM patients who lived longer than the median. In vitro experiments with GBM cells and analysis of patients' GBM samples suggest that Pim1 regulation is dependent on epidermal growth factor receptor. Furthermore, inhibition of Pim1 resulted in reduced cell viability accompanied by decreased cell numbers and increased apoptotic cells, as seen by elevated subG1 cell contents and caspase-3 and -9 activation, as well as modulation of several cell cycle or apoptosis regulatory proteins.

CONCLUSIONS

Altogether, Pim1 could be a novel therapeutic target, which should be further analyzed to improve the outcome of patients with aggressive GBM.

Signaling events involved in interleukin 27 (IL-27)-induced proliferation of human naive CD4+ T cells and B cells

IL-27 induces stronger proliferation of naive than memory human B cells and CD4(+) T cells. In B cells, this differential response is associated with similar levels of IL-27 receptor chains, IL-27Rα and gp130, in both subsets and stronger STAT1 and STAT3 activation by IL-27 in naive B cells. Here, we show that the stronger proliferative response of CD3-stimulated naive CD4(+) T cells to IL-27 is associated with lower levels of IL-27Rα but higher levels of gp130 compared with memory CD4(+) T cells. IL-27 signaling differs between naive and memory CD4(+) T cells, as shown by more sustained STAT1, -3, and -5 activation and weaker activation of SHP-2 in naive CD4(+) T cells. In the latter, IL-27 increases G0/G1 to S phase transition, cell division and, in some cases, cell survival. IL-27 proliferative effect on naive CD4(+) T cells is independent of MAPK, but is dependent on c-Myc and Pim-1 induction by IL-27 and is associated with induction of cyclin D2, cyclin D3, and CDK4 by IL-27 in a c-Myc and Pim-1-dependent manner. In BCR-stimulated naive B cells, IL-27 only increases entry in the S phase and induces the expression of Pim-1 and of cyclins A, D2, and D3. In these cells, inhibition of Pim-1 inhibits IL-27 effect on proliferation and cyclin induction. Altogether, these data indicate that IL-27 mediates proliferation of naive CD4(+) T cells and B cells through induction of both common and distinct sets of cell cycle regulators.

c-Myc induction of programmed cell death may contribute to carcinogenesis: a perspective inspired by several concepts of chemical carcinogenesis

The c-Myc protein, encoded by c-myc gene, in its wild-type form can induce tumors with a high frequency and can induce massive programmed cell death (PCD) in most transgenic mouse models, with greater efficiency than other oncogenes. Evidence also indicates that c-Myc can cause proliferative inhibition, i.e. mitoinhibition. The c-Myc-induced PCD and mitoinhibition, which may be attributable to its inhibition of cyclin D1 and induction of p53, may impose a pressure of compensatory proliferation, i.e. regeneration, onto the initiated cells (cancer progenitor cells) that occur sporadically and are resistant to the mitoinhibition. The initiated cells can thus proliferate robustly and progress to a malignancy. This hypothetical thinking, i.e. the concurrent PCD and mitoinhibition induced by c-Myc can promote carcinogenesis, predicts that an optimal balance is achieved between cell death and ensuing regeneration during oncogenic transformation by c-Myc, which can better promote carcinogenesis. In this perspective, we summarize accumulating evidence and challenge the current model that oncoprotein induces carcinogenesis by promoting cellular proliferation and/or inhibiting PCD. Inspired by c-myc oncogene, we surmise that many tumor-suppressive or growth-inhibitory genes may also be able to promote carcinogenesis in a similar way, i.e. by inducing PCD and/or mitoinhibition of normal cells to create a need for compensatory proliferation that drives a robust replication of initiating cells.

For better or for worse: the role of Pim oncogenes in tumorigenesis

Pim oncogenes are overexpressed in a wide range of tumours from a haematological and epithelial origin. Pim genes encode serine/threonine kinases that have been shown to counteract the increased sensitivity to apoptosis induction that is associated with MYC-driven tumorigenesis. Recently, considerable progress has been made in characterizing the pathways of PIM-mediated survival signalling. Given the unique structure of their active site and the minimal phenotype of mice mutant for all Pim family members, these oncogenes might be promising targets for highly specific and selective drugs with favourable toxicity profiles. In this Review, we discuss the physiological functions and oncogenic activities of Pim kinases.

Cancer gene discovery in mouse and man

The elucidation of the human and mouse genome sequence and developments in high-throughput genome analysis, and in computational tools, have made it possible to profile entire cancer genomes. In parallel with these advances mouse models of cancer have evolved into a powerful tool for cancer gene discovery. Here we discuss the approaches that may be used for cancer gene identification in both human and mouse and discuss how a cross-species 'oncogenomics' approach to cancer gene discovery represents a powerful strategy for finding genes that drive tumourigenesis.