Targeting the JAK-STAT pathway in lymphoma: a focus on pacritinib

Circular RNAs and the JAK/STAT pathway: New frontiers in cancer therapeutics

Circular RNAs, known as circRNAs, have drawn more attention to cancer biology in the last few years. Novel functions of circRNAs in cancer therapy open promising prospects for personalized medicine. This review focuses on the molecular properties and potential of circRNAs as biomarkers or therapeutic targets in cancer treatment. Unique properties of circular RNAs associated with a circular form provide stability and resilience to RNA exonuclease degradation. Circular RNAs' most important characteristic is that they are involved in the JAK/STAT pathway associated with oncogenesis. Notably, their deregulation has been reported in multiple carcinomas due to involvement in JAK/STAT signaling cascade modulation. Increased knowledge about circRNAs' interaction with the JAK/STAT pathway leads to the emergence of new possibilities for targeted cancer therapy. In addition, since circRNAs demonstrate tissue-relatedness of expression, they may be a reliable biomarker for predicting and diagnosing cancer. With the development of new technologies for targeting circRNAs, novel therapeutics can be produced that offer more personalized cancer treatment options based on the nature of the patient. The present review explores the exciting prospects of circRNAs for transforming cancer treatment into personalized medicine. It describes the current understanding of circRNA biology, its relationship to tumorigenesis, and possible targeting methods.

Janus Kinase Signaling: Oncogenic Criminal of Lymphoid Cancers

Simple Summary

Janus kinases (JAKs) are transmembrane receptors that pass signals from extracellular ligands to downstream. Increasing evidence has suggested that JAK family aberrations promote lymphoid cancer pathogenesis and progression through mediating gene expression via the JAK/STAT pathway or noncanonical JAK signaling. We are here to review how canonical JAK/STAT and noncanonical JAK signalings are represented and deregulated in lymphoid malignancies and how to target JAK for therapeutic purposes.

Abstract

The Janus kinase (JAK) family are known to respond to extracellular cytokine stimuli and to phosphorylate and activate signal transducers and activators of transcription (STAT), thereby modulating gene expression profiles. Recent studies have highlighted JAK abnormality in inducing over-activation of the JAK/STAT pathway, and that the cytoplasmic JAK tyrosine kinases may also have a nuclear role. A couple of anti-JAK therapeutics have been developed, which effectively harness lymphoid cancer cells. Here we discuss mutations and fusions leading to JAK deregulations, how upstream nodes drive JAK expression, how classical JAK/STAT pathways are represented in lymphoid malignancies and the noncanonical and nuclear role of JAKs. We also summarize JAK inhibition therapeutics applied alone or synergized with other drugs in treating lymphoid malignancies.

The JAK2 inhibitor TG101209 exhibits anti-tumor and chemotherapeutic sensitizing effects on Burkitt lymphoma cells by inhibiting the JAK2/STAT3/c-MYB signaling axis

Constitutive activation of JAK2/STAT3 is a major oncogenic signaling event involved in the development of Burkitt lymphoma (BL). In the present study, we investigated the antilymphoma activity of TG101209, a specific JAK2 inhibitor, on EBV-positive and EBV-negative Burkitt lymphoma cell lines and primary BL cells. The results showed that TG101209 had a significant antilymphoma effect by inhibiting BL cell growth and inducing apoptosis along with cell differentiation toward mature B cells in vitro. We also found that TG101209 displayed significant synergistic action and a sensitizing effect on the anti-Burkitt lymphoma activity of doxorubicin. In vivo experiments indicated that TG101209 could suppress tumor growth and prolong the overall survival of BL cell-bearing mice. The mechanistic study indicated that TG101209, by suppressing the JAK2/STAT3/c-MYB signaling axis and crosstalk between the downstream signaling pathways, plays an antilymphoma role. These data suggested that TG101209 may be a promising agent or alternative choice for the treatment of BL.

2-Thiopyrimidine/chalcone hybrids: design, synthesis, ADMET prediction, and anticancer evaluation as STAT3/STAT5a inhibitors

A novel 2-thiopyrimidine/chalcone hybrid was designed, synthesised, and evaluated for their cytotoxic activities against three different cell lines, K-562, MCF-7, and HT-29. The most active cytotoxic derivatives were 9d, 9f, 9n, and 9p (IC50=0.77-1.74 µM, against K-562 cell line), 9a and 9r (IC50=1.37-3.56 µM against MCF-7 cell line), and 9a, 9l, and 9n (IC50=2.10 and 2.37 µM against HT-29 cell line). Compounds 9a, 9d, 9f, 9n, and 9r were further evaluated for their cytotoxicity against normal fibroblast cell line WI38. Moreover, STAT3 and STAT5a inhibitory activities were determined for the most active derivatives 9a, 9d, 9f, 9n, and 9r. Dual inhibitory activity was observed in compound 9n (IC50=113.31 and 50.75 µM, against STAT3 and STAT5a, respectively). Prediction of physicochemical properties, drug likeness score, pharmacokinetic and toxic properties was detected.

Epigenetic regulation of miR-518a-5p-CCR6 feedback loop promotes both proliferation and invasion in diffuse large B cell lymphoma

To investigate the detailed functions and underlying mechanisms of miR-518a-5p/CCR6 in diffuse large B cell lymphoma (DLBCL) is needed. In this study, CCR6 expression levels were tested both in DLBCL cell lines and specimens. Through bioinformatics analysis and quantitative real-time PCR (qRT-PCR) validation, CCR6's targeted miRNA was obtained. Dual luciferase assay was used to verify their targeted relationship. Futhermore, using qRT-PCR, western blot, CCK8, Transwell assays, flow cytometry, pyrosequencing, chromatin immunoprecipitation, and azacitidine/C646 treatment, the detailed functions and underlying mechanisms of CCR6 and its targeted miRNA in DLBCL were detected. We found that negative correlation existed between CCR6 and miR-518a-5p in DLBCL. Both up-regulated miR-518a-5p and down-regulated CCR6 inhibited cell proliferation and invasion in vitro. Experiment then verified the regulatory relationship between miR-518a-5p and CCR6. JAK2 and STAT6 levels were reduced in DLBCL cells transfected with miR-518a-5p mimic or CCR6 small interfering RNA. Interestingly, we showed for the first time that a hyper-methylated condition existed at the promoter region of miR-518a-5p and azacitidine changed levels of miR-518a-5p in a time- and concentration-dependent manner. Finally, we found an enriched histone H3 on lysine 27 acetylation existed in the promoter of CCR6, whose expression could also be changed via C646 in a time- and concentration-dependent manner. The above results suggest that miR-518a-5p-CCR6 feedback loop plays a critical role in DLBCL development. The overexpression of CCR6 is mainly mediated by epigenetic modification through transcriptional and post-transcriptional activation, which provides new directions for DLBCL treatment.

Identifying Genetic Lesions in Ocular Adnexal Extranodal Marginal Zone Lymphomas of the MALT Subtype by Whole Genome, Whole Exome and Targeted Sequencing

The pathogenesis of ocular adnexal marginal zone lymphomas of mucosa-associated lymphatic tissue-type (OAML) is not fully understood. We performed whole genome sequencing (WGS) and/or whole exome sequencing (WES) for 13 cases of OAML and sequenced 38 genes selected from this analysis in a large cohort of 82 OAML. Besides confirmation of frequent mutations in the genes transducin beta like 1 X-linked receptor 1 (TBL1XR1) and cAMP response element binding protein (CREBBP), we newly identifed JAK3 as a frequently mutated gene in OAML (11% of cases). In our retrospective cohort, JAK3 mutant cases had a shorter progression-free survival compared with unmutated cases. Other newly identified genes recurrently mutated in 5-10% of cases included members of the collagen family (collagen type XII alpha 1/2 (COL12A1, COL1A2)) and DOCK8. Evaluation of the WGS data of six OAML did not reveal translocations or a current infection of the lymphoma cells by viruses. Evaluation of the WGS data for copy number aberrations confirmed frequent loss of TNFAIP3, and revealed recurrent gains of the NOTCH target HES4, and of members of the CEBP transcription factor family. Overall, we identified several novel genes recurrently affected by point mutations or copy number alterations, but our study also indicated that the landscape of frequently (>10% of cases) mutated protein-coding genes in OAML is now largely known.

Inhibition of JAK2/STAT3 Signaling Pathway Suppresses Proliferation of Burkitt's Lymphoma Raji Cells via Cell Cycle Progression, Apoptosis, and Oxidative Stress by Modulating HSP70

Background

The aim of this study was to investigate the effect of the JAK2/STAT3 pathway on the proliferation, cell cycle distribution, apoptosis, and oxidative stress of Raji cells via regulating HSP70 expression.

Material/Methods

Raji cells were divided into Blank, HSP70 siRNA, NC siRNA, AG490 (a JAK2/STAT3 signaling pathway inhibitor), and HSP70 siRNA + rh JAK2 (recombinant human JAK2) groups. HSP70 expression was detected by quantitative real-time reverse transcription-PCR (qRT-PCR); the expression levels of HSP70 and JAK2/STAT3 pathway-related proteins were evaluated by Western blotting; cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays; cell cycle distribution was observed by flow cytometry; cell apoptosis was tested by Annexin V-FITC/PI and Hoechst 33342/PI staining; reactive oxygen species (ROS) production was measured by dichloro-dihydro-fluorescein diacetate (DCFH-DA) assays; and MDA content and SOD and GSH-Px activities were determined using detection kits.

Results

AG490 obviously down-regulated HSP70 expression, inhibited proliferation, induced cell cycle arrest at the G0/G1 phase, and promoted apoptosis in Raji cells; these effects were similar to the effects of HSP70 siRNA. Furthermore, ROS production and MDA content were increased in Raji cells treated with HSP70 siRNA or AG490, while SOD and GSH-Px activities were reduced. Raji cells in the HSP70 siRNA + rh JAK2 group did not significantly differ from those in the Blank group in regards to proliferation, cell cycle, apoptosis, and oxidative stress.

Conclusions

Blocking the JAK2/STAT3 signaling pathway may inhibit proliferation, induce cell cycle arrest, and promote oxidative stress and apoptosis in Raji cells via the down-regulation of HSP70.

Contribution of STAT3 to Inflammatory and Fibrotic Diseases and Prospects for its Targeting for Treatment

Signal transducer and activator of transcription (STAT) 3 plays a central role in the host response to injury. It is activated rapidly within cells by many cytokines, most notably those in the IL-6 family, leading to pro-proliferative and pro-survival programs that assist the host in regaining homeostasis. With persistent activation, however, chronic inflammation and fibrosis ensue, leading to a number of debilitating diseases. This review summarizes advances in our understanding of the role of STAT3 and its targeting in diseases marked by chronic inflammation and/or fibrosis with a focus on those with the largest unmet medical need.

The role of the JAK/STAT signal pathway in rheumatoid arthritis

Proinflammatory cytokine activation of the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signal transduction pathway is a critical event in the pathogenesis and progression of rheumatoid arthritis. Under normal conditions, JAK/STAT signaling reflects the influence of negative regulators of JAK/STAT, exemplified by the suppressor of cytokine signaling and protein inhibitor of activated STAT. However, in rheumatoid arthritis (RA) both of these regulators are dysfunctional. Thus, continuous activation of JAK/STAT signaling in RA synovial joints results in the elevated level of matrix metalloproteinase gene expression, increased frequency of apoptotic chondrocytes and most prominently 'apoptosis resistance' in the inflamed synovial tissue. Tofacitinib, a JAK small molecule inhibitor, with selectivity for JAK2/JAK3 was approved by the United States Food and Drug Administration (US FDA) for the therapy of RA. Importantly, tofacitinib has demonstrated significant clinical efficacy for RA in the post-US FDA-approval surveillance period. Of note, the success of tofacitinib has spurred the development of JAK1, JAK2 and other JAK3-selective small molecule inhibitors, some of which have also entered the clinical setting, whereas other JAK inhibitors are currently being evaluated in RA clinical trials.

The landscape of new drugs in lymphoma

The landscape of drugs for the treatment of lymphoma has become crowded in light of the plethora of new agents, necessitating the efficient prioritization of drugs for expedited development. The number of drugs available, and the fact that many can be given for an extended period of time, has resulted in the emergence of new challenges; these include determining the optimal duration of therapy, and the need to balance costs, benefits, and the risk of late-onset toxicities. Moreover, with the increase in the number of available investigational drugs, the number of possible combinations is becoming overwhelming, which necessitates prioritization plans for the selective development of novel combination regimens. In this Review, we describe the most-promising agents in clinical development for the treatment of lymphoma, and provide expert opinion on new strategies that might enable more streamlined drug development. We also address new approaches for patient selection and for incorporating new end points into clinical trials.

Negative Regulators of JAK/STAT Signaling in Rheumatoid Arthritis and Osteoarthritis

Elevated levels of pro-inflammatory cytokines are generally thought to be responsible for driving the progression of synovial joint inflammation in rheumatoid arthritis (RA) and osteoarthritis (OA). These cytokines activate several signal transduction pathways, including the Janus kinase/Signal Transducers and Activators of Transcription (JAK/STAT), Stress-Activated/Mitogen-Activated Protein Kinase (SAPK/MAPK) and phosphatidylinositol-3-kinase/Akt/mechanistic target of rapamycin (PI3K/Akt/mTOR) pathways which regulate numerous cellular responses. However, cytokine gene expression, matrix metalloproteinase gene expression and aberrant immune cell and synoviocyte survival via reduced apoptosis are most critical in the context of inflammation characteristic of RA and OA. Negative regulation of JAK/STAT signaling is controlled by Suppressor of Cytokine Signaling (SOCS) proteins. SOCS is produced at lower levels in RA and OA. In addition, gaining further insight into the role played in RA and OA pathology by the inhibitors of the apoptosis protein family, cellular inhibitor of apoptosis protein-1, -2 (c-IAP1, c-IAP2), X (cross)-linked inhibitor of apoptosis protein (XIAP), protein inhibitor of activated STAT (PIAS), and survivin (human) as well as SOCS appears to be a worthy endeavor going forward.

Oncogenic Signaling Pathways and Pathway-Based Therapeutic Biomarkers in Lymphoid Malignancies

Lymphoma is characterized by heterogeneous biology, pathologic features, and clinical outcome. This has been proven by accumulating pathologic and molecular evidence attributed to underlying aberrant alterations at genetic, epigenetic, transcriptional, protein, microenvironmental levels, and dysregulated oncogenic signaling pathways. In the era of precision medicine, targeting oncogenic pathways to design drugs and to optimize treatment regimens for the lymphoma patients is feasible and clinically significant. As such, further understanding of the biology and the mechanisms behind lymphoma development and identification of oncogenic pathway activation and pathway-based biomarkers to better design precise therapies are challenging but hopeful. Furthermore, pathway-based targeted therapies in combination with traditional chemotherapy, single specific targeted antibody therapy, and immunotherapy might raise the hope for the patients with lymphoma, especially for relapsed and refractory lymphoma patients.

Synthetic Lethal Screen Demonstrates That a JAK2 Inhibitor Suppresses a BCL6-dependent IL10RA/JAK2/STAT3 Pathway in High Grade B-cell Lymphoma

We demonstrate the usefulness of synthetic lethal screening of a conditionally BCL6-deficient Burkitt lymphoma cell line, DG75-AB7, with a library of small molecules to determine survival pathways suppressed by BCL6 and suggest mechanism-based treatments for lymphoma. Lestaurtinib, a JAK2 inhibitor and one of the hits from the screen, repressed survival of BCL6-deficient cells in vitro and reduced growth and proliferation of xenografts in vivo BCL6 deficiency in DG75-AB7 induced JAK2 mRNA and protein expression and STAT3 phosphorylation. Surface IL10RA was elevated by BCL6 deficiency, and blockade of IL10RA repressed STAT3 phosphorylation. Therefore, we define an IL10RA/JAK2/STAT3 pathway each component of which is repressed by BCL6. We also show for the first time that JAK2 is a direct BCL6 target gene; BCL6 bound to the JAK2 promoter in vitro and was enriched by ChIP-seq. The place of JAK2 inhibitors in the treatment of diffuse large B-cell lymphoma has not been defined; we suggest that JAK2 inhibitors might be most effective in poor prognosis ABC-DLBCL, which shows higher levels of IL10RA, JAK2, and STAT3 but lower levels of BCL6 than GC-DLBCL and might be usefully combined with novel approaches such as inhibition of IL10RA.

DNA methyltransferase inhibitors: an updated patent review (2012-2015)

INTRODUCTION

DNA methyltransferases (DNMTs), important enzymes involved in epigenetic regulation of gene expression, represent promising targets in cancer therapy. DNMT inhibitors (DNMTi), which can modulate the aberrant DNA methylation pattern in a reversible way via inhibiting DNMT activity, have attracted significant attention in recent years.

AREAS COVERED

This review outlines the newly patented inhibitors targeting DNMTs, mainly incorporating small molecular inhibitors and oligonucleotide derivatives. The chemical structures, biological activity, and the encouraging clinical research in progress are delineated in detail.

EXPERT OPINION

Two drugs, azacitidine and decitabine, have evidently shown efficacy in hematologic malignancies, yet do not work well on solid tumors, have low specificity, substantial toxicity, and poor bioavailability. With the rapid advancement in systems biology, drug combinations, such as DNMTi, in conjugation with histone deacetylase inhibitors (HDACi) or immunotherapy, probably serve as an efficient way of implementing epigenetic therapy. Meanwhile, the resolved autoinhibitory structures of DNMTs afford a novel strategy for targeting the protein-protein interface involved in the autoinhi-bitory interactions. The molecular mechanism underlying the conformational transitions would also shed new light on the design of allosteric inhibitors. Both strategies would produce inhibitors with more selectivity compared to nucleotide derivatives.

Involvement of transcription factor Oct-1 in the regulation of JAK-STAT signaling pathway in cells of Burkitt lymphoma

We studied the role of transcription factor Oct-1 in the regulation of expression of genes of the JAK-STAT signaling pathway in the Namalwa Burkitt's lymphoma cell line. Overexpression of Oct-1 isoforms (Oct-1A, Oct-1L, and Oct-1X) causes a decrease in the activity of four genes involved in the JAK-STAT signaling pathway-IFNAR2, STAT1, STAT2, and STAT4. As a result of our research, it was found that genes STAT2 and STAT4 are direct targets for Oct-1 protein.

Novel drug targets for personalized precision medicine in relapsed/refractory diffuse large B-cell lymphoma: a comprehensive review

Diffuse large B-cell lymphoma (DLBCL) is a clinically heterogeneous lymphoid malignancy and the most common subtype of non-Hodgkin's lymphoma in adults, with one of the highest mortality rates in most developed areas of the world. More than half of DLBLC patients can be cured with standard R-CHOP regimens, however approximately 30 to 40 % of patients will develop relapsed/refractory disease that remains a major cause of morbidity and mortality due to the limited therapeutic options.Recent advances in gene expression profiling have led to the identification of at least three distinct molecular subtypes of DLBCL: a germinal center B cell-like subtype, an activated B cell-like subtype, and a primary mediastinal B-cell lymphoma subtype. Moreover, recent findings have not only increased our understanding of the molecular basis of chemotherapy resistance but have also helped identify molecular subsets of DLBCL and rational targets for drug interventions that may allow for subtype/subset-specific molecularly targeted precision medicine and personalized combinations to both prevent and treat relapsed/refractory DLBCL. Novel agents such as lenalidomide, ibrutinib, bortezomib, CC-122, epratuzumab or pidilizumab used as single-agent or in combination with (rituximab-based) chemotherapy have already demonstrated promising activity in patients with relapsed/refractory DLBCL. Several novel potential drug targets have been recently identified such as the BET bromodomain protein (BRD)-4, phosphoribosyl-pyrophosphate synthetase (PRPS)-2, macrodomain-containing mono-ADP-ribosyltransferase (ARTD)-9 (also known as PARP9), deltex-3-like E3 ubiquitin ligase (DTX3L) (also known as BBAP), NF-kappaB inducing kinase (NIK) and transforming growth factor beta receptor (TGFβR).This review highlights the new insights into the molecular basis of relapsed/refractory DLBCL and summarizes the most promising drug targets and experimental treatments for relapsed/refractory DLBCL, including the use of novel agents such as lenalidomide, ibrutinib, bortezomib, pidilizumab, epratuzumab, brentuximab-vedotin or CAR T cells, dual inhibitors, as well as mechanism-based combinatorial experimental therapies. We also provide a comprehensive and updated list of current drugs, drug targets and preclinical and clinical experimental studies in DLBCL. A special focus is given on STAT1, ARTD9, DTX3L and ARTD8 (also known as PARP14) as novel potential drug targets in distinct molecular subsets of DLBCL.

Cancer prevention and therapy through the modulation of the tumor microenvironment

Cancer arises in the context of an in vivo tumor microenvironment. This microenvironment is both a cause and consequence of tumorigenesis. Tumor and host cells co-evolve dynamically through indirect and direct cellular interactions, eliciting multiscale effects on many biological programs, including cellular proliferation, growth, and metabolism, as well as angiogenesis and hypoxia and innate and adaptive immunity. Here we highlight specific biological processes that could be exploited as targets for the prevention and therapy of cancer. Specifically, we describe how inhibition of targets such as cholesterol synthesis and metabolites, reactive oxygen species and hypoxia, macrophage activation and conversion, indoleamine 2,3-dioxygenase regulation of dendritic cells, vascular endothelial growth factor regulation of angiogenesis, fibrosis inhibition, endoglin, and Janus kinase signaling emerge as examples of important potential nexuses in the regulation of tumorigenesis and the tumor microenvironment that can be targeted. We have also identified therapeutic agents as approaches, in particular natural products such as berberine, resveratrol, onionin A, epigallocatechin gallate, genistein, curcumin, naringenin, desoxyrhapontigenin, piperine, and zerumbone, that may warrant further investigation to target the tumor microenvironment for the treatment and/or prevention of cancer.

Identification of azabenzimidazoles as potent JAK1 selective inhibitors

We have identified a class of azabenzimidazoles as potent and selective JAK1 inhibitors. Investigations into the SAR are presented along with the structural features required to achieve selectivity for JAK1 versus other JAK family members. An example from the series demonstrated highly selective inhibition of JAK1 versus JAK2 and JAK3, along with inhibition of pSTAT3 in vivo, enabling it to serve as a JAK1 selective tool compound to further probe the biology of JAK1 selective inhibitors.

Genetic and molecular targets in lymphoma: implications for prognosis and treatment

Lymphomas are the most common hematologic malignancies with approximately 79,000 new cases estimated for 2013 in the USA. Despite improved outcomes, relapse or recurrence remains a common problem with conventional cytotoxic therapy. Recently, many genetic and molecular mechanisms that drive various cellular events like apoptosis, angiogenesis and cell motility have been more clearly delineated. These new findings, coupled with the advent of high-throughput screening technology have led to the discovery of many compounds that can target specific mutations and/or influence deregulated transcription. In this review, we intend to provide a concise overview of genetic and molecular events that drive cellular processes in lymphomas and represent potential therapeutic targets. Additionally, we briefly discuss the prognostic significance of select biological markers.

9H-Carbazole-1-carboxamides as potent and selective JAK2 inhibitors

The discovery, synthesis, and characterization of 9H-carbazole-1-carboxamides as potent and selective ATP-competitive inhibitors of Janus kinase 2 (JAK2) are discussed. Optimization for JAK family selectivity led to compounds 14 and 21, with greater than 45-fold selectivity for JAK2 over all other members of the JAK kinase family.

Designed Macrocyclic Kinase Inhibitors

Cancer continues to present as an increasing and serious global unmet medical need in today's aging population.1 Macrocyclic kinase inhibitors have reached advanced clinical testing and are making an impact in oncologic conditions including myelofibrosis, lymphomas and leukemias. Rheumatoid arthritis (RA) is also beginning to be impacted with the first macrocycle having entered Phase I clinical evaluation in healthy volunteers. Increasing reports of innovative macrocycles in preclinical research are appearing in the literature. Desirable, selective, multi-kinase inhibitory profiles against specific kinases known to be abrogated in cancer, RA, and other diseases have been achieved in a first generation series of clinical stage compact small molecule macrocyclic kinase inhibitors. Herein we discuss their design, synthesis, structure activity relationships and assessment of the latest clinical data in a range of oncologic conditions. Macrocyclic kinase inhibitors have the potential to offer new hope to patients and their families.

Profile of pacritinib and its potential in the treatment of hematologic disorders

Pacritinib (previously known as SB-1518) is an innovative selective inhibitor of Janus kinase 2 and FMS-related tyrosine kinase 3 providing potential in the treatment of hematological malignancies such as myeloproliferative neoplasias, acute myeloid leukemia, and various lymphomas. Pacritinib has potent antiproliferative activity in Janus kinase 2 and/or FMS-related tyrosine kinase 3 activity-dependent cell lines and an ability to promote apoptosis and inhibit the signal transducers and activators of transcription (STAT) pathway. Pharmacokinetic studies have indicated a good per os bioavailability and favorable kinetic parameters. To date, promising results have been produced in five completed early-phase clinical trials in which pacritinib has been studied. Pacritinib displayed interesting activity and an acceptable safety profile, with mild to moderate gastrointestinal disorders being its most common adverse effects.

Investigational FMS-like tyrosine kinase 3 inhibitors in treatment of acute myeloid leukemia

INTRODUCTION

Outcomes for the majority of patients with acute myeloid leukemia (AML) remain poor. Over the past decade, significant progress has been made in the understanding of the cytogenetic and molecular determinants of AML pathogenesis. One such advance is the identification of recurring mutations in the FMS-like tyrosine kinase 3 gene (FLT3). Currently, this marker, which appears in approximately one-third of all AML patients, not only signifies a poorer prognosis but also identifies an important target for therapy. FLT3 inhibitors have now undergone clinical evaluation in Phase I, II and III clinical trials, as both single agents and in combination with chemotherapeutics. Unfortunately, to date, none of the FLT3 inhibitors have gained FDA approval for the treatment of patients with AML. Yet, several promising FLT3 inhibitors are being evaluated in all phases of drug development.

AREAS COVERED

This review aims to highlight the agents furthest along in their development. It also focuses on those FLT3 inhibitors that are being evaluated in combination with other anti-leukemia agents.

EXPERT OPINION

The authors believe that the field of research for FLT3 inhibitors remains promising, despite the historically poor prognosis of this subgroup of patients with AML. The most promising areas of research will likely be the elucidation of the mechanisms of resistance to FLT3 inhibitors, and development of potent FLT3 inhibitors alone or in combination with hypomethylating agents, cytotoxic chemotherapy or with other targeted agents.

Differential gene expression of the key signalling pathway in para-carcinoma, carcinoma and relapse human pancreatic cancer

Pancreatic cancer (PC) has a high rate of mortality and a poorly understood mechanism of progression. Investigation of the molecular mechanism of PC and exploration of the specific markers for early diagnosis and specific targets of therapy are key points to prevent and treat PC effectively and to improve their prognosis. In our study, expression profiles experiment of para-carcinoma, carcinoma and relapse human PC was performed using Agilent human whole genomic oligonucleotide microarrays with 45 000 probes. Differentially expressed genes related with PC were screened and analysed further by Gene Ontology term analysis and Kyoto encyclopaedia of genes and genomes pathway analysis. Our results showed that there were 3853 differentially expressed genes associated with pancreatic carcinogenesis and relapse. In addition, our study found that PC was related to the Jak-STAT signalling pathway, PPAR signalling pathway and Calcium signalling pathway, indicating their potential roles in pancreatic carcinogenesis and progress.

A rare case of primary cutaneous follicle centre lymphoma presenting as a giant tumour of the scalp and combined with JAK2V617F positive essential thrombocythaemia

Primary cutaneous follicle centre lymphoma (PCFCL) is a rare cutaneous B cell lymphoma in middle-age adults with excellent prognosis. Here we present a case of a patient with a PCFCL in the form of a giant tumour of the scalp in combination with a myeloproliferative neoplasm, JAK2V617F positive essential thrombocythaemia. This case may be of interest because of the favourable outcome in spite of the large size of the PCFCL, the rare combination with essential thrombocythaemia and because it contributes to discussion on the role of JAK2 mutation in such patients.

Emerging therapeutic paradigms to target the dysregulated Janus kinase/signal transducer and activator of transcription pathway in hematological malignancies

Over the past decade, there has been increasing biochemical evidence that the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway is aberrantly activated in malignant cells from patients with a wide spectrum of cancers of the blood and immune systems. The emerging availability of small molecule inhibitors of JAK and other signaling molecules in the JAK/STAT pathway has allowed preclinical studies validating an important role of this pathway in the pathogenesis of many hematologic malignancies, and provided motivation for new strategies for treatment of these diseases. Here, a round-table panel of experts review the current preclinical and clinical landscape of the JAK/STAT pathway in acute lymphoid and myeloid leukemias, lymphomas and myeloma, and chronic myeloid neoplasms.

Protein kinase inhibitors: breakthrough medicines and the next generation

In this issue of Expert Opinion on Investigational Drugs, several protein kinases families and pathways underlying cancer and other diseases are reviewed and several small molecule inhibitors that are in clinical trials are further described. Highlights of these reviews and drug evaluations are summarized in this editorial.

Role of the JAK-STAT signal pathway in the development and progression of liver cancer

Primary liver cancer is a kind of malignant tumor that occurs in liver cells and bile duct epithelial cells. There is a great difference in the incidence of liver cancer among different countries and regions. In China, liver cancer is one of the most common malignant tumors and has the third highest mortality rate. About 110 thousand people die of liver cancer in China each year, accounting for 45% of worldwide deaths caused by liver cancer. The research on the biological behavior of liver cancer has been widely carried out, and the relationship between the janus kinase-signal transducers and activators of transcription (JAK-STAT) signal pathway, which is activated in many types of human malignant tumors and involved in the occurrence and development of tumors, and liver cancer has attracted wide attention. In this paper we will discuss the relationship between the JAK-STAT signal pathway and biological behavior of liver cancer.