The PIM kinases in hematological cancers

The PIM genes represent a family of proto-oncogenes that encode three different serine/threonine protein kinases (PIM1, PIM2 and PIM3) with essential roles in the regulation of signal transduction cascades, which promote cell survival, proliferation and drug resistance. PIM kinases are overexpressed in several hematopoietic tumors and support in vitro and in vivo malignant cell growth and survival, through cell cycle regulation and inhibition of apoptosis. PIM kinases do not have an identified regulatory domain, which means that these proteins are constitutively active once transcribed. They appear to be critical downstream effectors of important oncoproteins and, when overexpressed, can mediate drug resistance to available agents, such as rapamycin. Recent crystallography studies reveal that, unlike other kinases, they possess a hinge region, which creates a unique binding pocket for ATP, offering a target for an increasing number of potent small-molecule PIM kinase inhibitors. Preclinical studies in models of various hematologic cancers indicate that these novel agents show promising activity and some of them are currently being evaluated in a clinical setting. In this review, we profile the PIM kinases as targets for therapeutics in hematologic malignancies.     

Structural basis and prediction of substrate specificity in protein serine/threonine kinases

The large number of protein kinases makes it impractical to determine their specificities and substrates experimentally. Using the available crystal structures, molecular modeling, and sequence analyses of kinases and substrates, we developed a set of rules governing the binding of a heptapeptide substrate motif (surrounding the phosphorylation site) to the kinase and implemented these rules in a web-interfaced program for automated prediction of optimal substrate peptides, taking only the amino acid sequence of a protein kinase as input. We show the utility of the method by analyzing yeast cell cycle control and DNA damage checkpoint pathways. Our method is the only available predictive method generally applicable for identifying possible substrate proteins for protein serinethreonine kinases and helps in silico construction of signaling pathways. The accuracy of prediction is comparable to the accuracy of data from systematic large-scale experimental approaches.     

Incidence and pathogenesis of thrombosis in hematologic malignancies

Recent surveys have indicated that thromboembolic complications are at least as common in hematologic malignancies, if not more frequent, than in solid tumors. The pathogenesis of thrombosis is similar to that in solid tumors, but with additional factors unique in several forms of hematologic malignancies, as seen in acute promyelocytic leukemia, myeloma, and myeloproliferative disorders. Likewise, the factors contributing to bleeding are similar to those seen in solid tumors, with the exception of a higher frequency of thrombocytopenia.     

Angiogenesis and antiangiogenic therapy in hematologic malignancies

Angiogenesis, the generation of new blood capillaries from preexisting blood vessels, is tightly regulated in the adult organism. Although many of the initial studies were performed on solid tumors, increasing evidence indicates that angiogenesis also plays an important role in hematologic malignancies. Overexpression of angiogenic factors in particular VEGF and bFGF in most hematologic malignancies may explain the increased angiogenesis found in these malignancies and correlate with poor prognosis as well as decreased overall survival. In this review, we focus on the current literature of angiogenesis and antiangiogenic therapy in hematologic malignancies, and finally describe advances and potential challenges in antiangiogenic treatment in hematologic malignancies.     

Immune and cell therapy of hematologic malignancies

Advances in molecular biology and immunology have identified means to activate the immune response against leukemia-associated antigens. Recent studies indicate that the stealth-like phenotype of leukemia cells can be reversed through transfer of genes encoding recombinant membrane-stabilized proteins of the tumor necrosis factor (TNF) imily, such as the one encoding CD154, the ligand for CD40. A phase I clinical trial using autologous CD154-transduced leukemia cells as a cellular vaccine has provided encouraging results. Treatment not only appears capable of inducing a cellular anti-leukemia immunity, but also may have a direct effect on leukemia cells by inducing latent sensitivity to Fas (CD95)-dependent leukemia-cell apoptosis. Phase II studies currently are underway using multiple injections of autologous leukemia cells made to express recombinant CD154 via gene transfer. Conceivably, we may be entering an era of effective gene therapy for hematologic malignancies.     

Gene therapy and active immune therapy of hematologic malignancies

Gene therapy for patients with hematologic malignancies, particularly chronic lymphocytic leukemia (CLL), have focused on transducing primary leukemia cells with a virus vector to express immune-stimulating genes which can induce and propagate a productive and clinically significant immune response against the malignant cells. A variety of replication-defective vectors has been studied to transduce genes for cytokines and function-associated surface molecules. Active vaccines have been developed in vitro, and their activity has been confirmed in clinical trials. Ongoing work aims to optimize this strategy and to identify the appropriate and optimal patient groups in which to apply vaccine therapy. Clinical trials also have provided insight into unexpected alternative mechanisms through which these strategies might provide a clinical benefit.     

Activation of the pp90rsk and mitogen-activated serine/threonine protein kinases by ionizing radiation.

The cellular response to ionizing radiation (IR) includes induction of the c-jun and EGR1 early response genes. The present work has examined potential cytoplasmic signaling cascades that transduce IR-induced signals to the nucleus. The results demonstrate activation of the 40S ribosomal protein S6 kinase, pp90rsk, in human U-937 myeloid leukemia cells. Partial purification of pp90rsk by affinity chromatography demonstrated an increase in S6 peptide phosphorylation when comparing irradiated with control cells. IR-induced activation of pp90rsk was further confirmed in immune-complex kinase assays. In contrast to these findings, there was no detectable induction of pp70S6K. Previous work has demonstrated that mitogen-activated protein kinase activates pp90rsk. The present results further show that IR treatment is associated with induction of mitogen-activated protein kinase activity and that this event is temporally related to activation of pp90rsk and early response gene expression. These findings suggest that activation of the mitogen-activated protein kinase/pp90rsk cascade is involved in the response of cells to IR exposure.     

Melatonin reverses the decreases in hippocampal protein serine/threonine kinases observed in an animal model of autism

Lower global cognitive function scores are a common symptom of autism spectrum disorders (ASDs). This study investigates the effects of melatonin on hippocampal serine/threonine kinase signaling in an experimental ASD model. We found that chronic melatonin (1.0 or 5.0 mg/kg/day, 28 days) treatment significantly rescued valproic acid (VPA, 600 mg/kg)‐induced decreases in CaMKII (Thr286), NMDAR1 (Ser896), and PKA (Thr197) phosphorylation in the hippocampus without affecting total protein levels. Compared with control rats, the immunostaining of pyramidal neurons in the hippocampus revealed a decrease in immunolabeling intensity for phospho‐CaMKII (Thr286) in the hippocampus of VPA‐treated rats, which was ameliorated by chronic melatonin treatment. Consistent with the elevation of CaMKII/PKA/PKC phosphorylation observed in melatonin‐treated rat, long‐term potentiation (LTP) was enhanced after chronic melatonin (5.0 mg/kg) treatment, as reflected by extracellular field potential slopes that increased from 56 to 60 min (133.4 ± 3.9% of the baseline, P < 0.01 versus VPA‐treated rats) following high‐frequency stimulation (HFS) in hippocampal slices. Accordingly, melatonin treatment also significantly improved social behavioral deficits at postnatal day 50 in VPA‐treated rats. Taken together, the increased phosphorylation of CaMKII/PKA/PKC signaling might contribute to the beneficial effects of melatonin on autism symptoms.     

真核样丝氨酸/苏氨酸激酶在链球菌中的研究进展

有机体的生存需要不断应对变化的环境。信号转导系统的存在有助于生物对不同的内外界信号做出相应的回应。蛋白质的磷酸化是信号转导的重要机制,二元信号转导系统(two-component signal transduction system,TCSTS)是细菌最普遍的信号转导方式,然而最早在真核生物中发现的丝氨酸、苏氨酸的磷酸化在原核生物中已成为研究的热点。丝氨酸/苏氨酸激酶与磷酸酶的协同作用与致病菌各种生命活动息息相关,包括生长,代谢,毒力以及应激压力等。本文重点介绍几种常见的链球菌中的丝/苏氨酸激酶,了解其在致病菌中的作用。鉴于真核生物STK已有大量的抑制剂被广泛使用,对链球菌真核样丝/苏氨酸激酶STK(eukaryotic-like Ser/Thr kinase,eSTK)的深入了解将有助于寻找应对链球菌感染的预防和治疗手段。     

New targets for CAR T therapy in hematologic malignancies

As we expand our acumen of the intricacies of hematological malignancies at a genetic and cellular level, we have paved the way in advancing novel targeted therapeutic avenues such as chimeric antigen receptor T-cell therapies (CAR T). Engineering cells to target a specific antigen has led to dramatic remission rates in cases of relapsed/refractory non-Hodgkin lymphoma, acute lymphoblastic leukemia as well as multiple myeloma thus far with trials in place to further advance targeted therapies in other hematological malignancies. Most currently available CAR T therapies target CD19 antigen. Studies are underway exploring novel CAR T products aimed at other tumor-specific antigens with potential to improve the efficacy and reduce the toxicities. Early studies have confirmed safety and efficacy of CD22 and BCMA targeted CAR T therapies. Moreover, various other targets including CD20, CD30, CD123, kappa, and lambda light chains among others are under clinical investigation as potential avenues of targeted therapy. This review highlights the shift in the treatment paradigm in pursuing diverse antigen targets while addressing the challenges in terms of the efficacy and toxicity of current CAR T-cell therapies.     

Immunotherapy of hematologic malignancies and metastatic solid tumors in experimental animals and man

Following engraftment of donor hematopoietic cells and induction of host-versus-graft tolerance, immunocompetent lymphocytes of donor origin can induce graft-versus-leukemia (GVL) and graft-versus-tumor (GVT) effects. Engraftment of allogeneic bone marrow cells can be accomplished following non-myeloablative conditioning while possibly controlling graft-versus-host disease (GVHD). GVL and GVT effects may thus be successfully accomplished following non-myeloablative stem cell transplantation (NST) as shown by data derived from experimental animals and man.     

Immunotherapy of hematologic malignancies and metastatic solid tumors in experimental animals and man

New approaches are needed for maximizing specific responses against tumor cells resistant to chemotherapy. While cytokine therapy may amplify natural resistance against minimal residual disease, more robust anti-leukemia reactivity can be provided by allogeneic bone marrow transplantation (BMT) in conjunction with myeloablative, hence hazardous, conditioning, at the cost of graft-versus-host disease (GVHD). Documentation of the capacity of donor lymphocyte infusion (DLI) given late post BMT, when patients were off immunosuppression, in early 1987, with successful reversal of relapse and cure of patients fully resistant to maximally tolerated doses of chemoradiotherapy, with many patients alive and well >10-15 years later, indicated two important facts. First, resistant tumors are unlikely to be cured with higher doses of chemoradiotherapy that may harm the patient but not eliminate all his clonogenic tumor cells. Second, that under condition of tolerance to donor alloantigens, DLI may provide a cure to otherwise resistant patients. These observations paved the road for clinical application of non-myeloablative stem cell transplantation (NST), in the early 90s, based on a two-step procedure, first involving induction of transplantation tolerance to donor alloantigens by engraftment of donor stem cells, following safe lymphoablative rather than myeloablative conditioning. Second, use of donor lymphocytes for elimination of residual tumor or otherwise abnormal hematopoietic cells by immune-mediated graft-versus-host effects inducible by mobilized blood stem cell allografts containing larger inocula of donor T cells, or supported by post-grafting DLI when patients were off immunosuppressive modalities.     

Epigenetics in the hematologic malignancies

A wealth of genomic and epigenomic data has identified abnormal regulation of epigenetic processes as a prominent theme in hematologic malignancies. Recurrent somatic alterations in myeloid malignancies of key proteins involved in DNA methylation, post-translational histone modification and chromatin remodeling have highlighted the importance of epigenetic regulation of gene expression in the initiation and maintenance of various malignancies. The rational use of targeted epigenetic therapies requires a thorough understanding of the underlying mechanisms of malignant transformation driven by aberrant epigenetic regulators. In this review we provide an overview of the major protagonists in epigenetic regulation, their aberrant role in myeloid malignancies, prognostic significance and potential for therapeutic targeting.     

Farnesyltransferase inhibitors in hematologic malignancies: new horizons in therapy

Farnesyltransferase inhibitors (FTIs) are small-molecule inhibitors that selectively inhibit farnesylation of a number of intracellular substrate proteins such as Ras. Preclinical work has revealed their ability to effectively inhibit tumor growth across a wide range of malignant phenotypes. Many hematologic malignancies appear to be reasonable disease targets, in that they express relevant biologic targets, such as Ras, mitogen-activated protein kinase (MAPK), AKT, and others that may depend on farnesyl protein transferase (FTase) activity to promote proliferation and survival. A host of phase 1 trials have been recently launched to assess the applicability of FTIs in hematologic malignancies, many of which demonstrate effective enzyme target inhibition, low toxicity, and some clinical responses. As a result, phase 2 trials have been initiated in a variety of hematologic malignancies and disease settings to further validate clinical activity and to identify downstream signal transduction targets that may be modified by these agents. It is anticipated that these studies will serve to define the optimal roles of FTIs in patients with hematologic malignancies and provide insight into effective methods by which to combine FTIs with other agents.     

Advances in antifungal prophylaxis and empiric therapy in patients with hematologic malignancies

Abstract: Invasive fungal infection (IFI) is associated with significant morbidity and mortality in patients with hematologic malignancies. There have been significant changes in the epidemiology and outcomes of IFI in this patient population, due in part to advances in transplant procedures, supportive care, and use of newer antifungal agents. A thorough knowledge of risk factors, potential causative organisms, and the safety and efficacy of appropriate antifungal agents is required to optimize treatment. Proper diagnosis of IFI is challenging and the correlation of delays in diagnosis and treatment with poor outcome suggest that earlier intervention may result in more effective management of high‐risk patients. Because all risks may not be equal, stratifying high‐risk patients may further help target patients most likely to benefit from prophylaxis. This review focuses on various risk factors specific to patients with hematologic malignancies and discusses the use of preemptive, empiric, and prophylactic strategies in the management of IFI in this patient population.