C-kit Receptor Tyrosine Kinase Research Articles

Chinese‐German Cooperation Group Tumor Immunology: Another inspiring Meeting in Deidesheim

Chinese‐German Cooperation Group Tumor Immunology: Another inspiring Meeting in Deidesheim

Laxative Effect of Spicatoside A by Cholinergic Regulation of Enteric Nerve in Loperamide-Induced Constipation: ICR Mice Model.

Researches on spicatoside A (SpiA)-containing natural products suggest the possibility of SpiA as a potential laxative to alleviate chronic constipation. However, no studies have been conducted with single compound administration of SpiA. To verify the laxative effects and mechanism of action of SpiA on chronic constipation, we investigated alterations in the excretion parameters, histological structure, and cholinergic regulation of the enteric nerve in the colons of Institute of Cancer Research (ICR) mice with loperamide (Lop)-induced constipation after exposure to 20 mg/kg of SpiA. Decrease in the number, weight and water contents of stools in the Lop+Vehicle treated group significantly recovered after SpiA treatment, and alterations in the histological structure and transmission electron microscopy (TEM) images were improved in the Lop+SpiA treated group. Similar recovery effects were observed in the ability for mucin secretion and expression of the membrane water channel gene (aquaporin 8, AQP8). Furthermore, significant improvements were observed in the acetylcholinesterase (AChE) activity and acetylcholine receptors’ (AChRs) downstream signaling pathway after treatment of SpiA. The levels of gastrointestinal (GI) hormones including cholecystokinin (CCK) and gastrin were also remarkably enhanced in the Lop+SpiA treated group as compared to the Lop+Vehicle treated group. The expression of receptor tyrosine kinase (C-kit) and protein gene product 9.5 (PGP9.5) in Cajal and neural cells, as well as the phosphorylation of myosin light chain (MLC) in smooth muscle cells, were recovered after SpiA exposure. Taken together, the results of the present study provide the first strong evidence that SpiA improves chronic constipation through muscarinic cholinergic regulation of the enteric nerve in a Lop-induced constipation ICR mice model.

Pediatric cutaneous mastocytosis and c-KIT mutation screening.

Background: Cutaneous mastocytosis (CM) is a heterogeneous disease that commonly presents with skin lesions in childhood. Objective: In this study, we aimed to evaluate the clinical and laboratory test results of our patients with CM to ascertain prognostic factors by using patients' long-term follow-up results and to determine c-KIT (receptor tyrosine kinase) mutation from peripheral blood samples, which might be responsible for the etiopathogenesis of pediatric mastocytosis. Methods: The clinical observation data of 32 children who had been diagnosed with CM were retrospectively researched. Exon 8, 9, 11, 13, and 17 c-KIT gene locations were analyzed from DNA material that was obtained from peripheral blood samples of all the patients by using polymerase chain reaction analysis and automatic DNA sequencing. Results: The tryptase level was higher in patients with familial cases and in cases of patients who had gastrointestinal mediator releasing symptoms (p = 0.017, p = 0.038, respectively). The use of clarithromycin and the use of vitamin D were determined as triggers for mediator release. Hypogammaglobulinemia was found in six patients (18.8%). Indoor tobacco exposure was seen to be higher in patients not in remission than in patients in remission (59.1% and 20%, respectively) (p = 0.040). Allergic diseases were observed in 80% of patients in complete remission and 22.7% of patients not in remission (p = 0.002). Concomitant allergic diseases were found to be good prognosis markers among pediatric patients with CM. No c-KIT mutation was discovered in any of the patients. Conclusion: In this study, tobacco exposure would seem to be a barrier for remission, and concomitant allergic diseases were seen to be a good prognosis marker. Evaluation of peripheral c-KIT mutation had no diagnostic contribution among pediatric patients with CM in contrast to adults.

Frontline Science: Mast cells regulate neutrophil homeostasis by influencing macrophage clearance activity.

The receptor tyrosine kinase cKit and its ligand stem cell factor are essential for mast cells (MC) development and survival. Strains with mutations affecting the Kit gene display a profound MC deficiency in all tissues and have been extensively used to investigate the role of MC in both physiologic and pathologic conditions. However, these mice present a variety of abnormalities in other immune cell populations that can affect the interpretation of MC-related responses. C57BL/6 KitW-sh are characterized by an aberrant extramedullary myelopoiesis and systemic neutrophilia. MC deficiency in KitW-sh mice can be selectively repaired by engraftment with in vitro-differentiated MC to validate MC-specific functions. Nevertheless, the impact of MC reconstitution on other immune populations has never been evaluated in detail. Here, we specifically investigated the neutrophil compartment in primary and secondary lymphoid organs of C57BL/6 KitW-sh mice before and after MC reconstitution. We found that, albeit not apparently affecting neutrophils phenotype or maturation, MC reconstitution of KitW-sh mice restored the number of neutrophils at a level similar to that of wild-type C57BL/6 mice. In vitro and ex vivo experiments indicated that MC can influence neutrophil clearance by increasing macrophages' phagocytic activity. Furthermore, the G-CSF/IL-17 axis was also influenced by the presence or absence of MC in KitW-sh mice. These data suggest that MC play a role in the control of neutrophil homeostasis and that this aspect should be taken into account in the interpretation of results obtained using KitW-sh mice.

The intermediate filament protein synemin (SYNM) was found to be more widespread in CD117+ gastrointestinal stromal cell tumors (GIST) than the CD34 transmembrane phosphoglycoprotein: an immunohistochemical study

ABSTRACTInterstitial cells of Cajal (ICC) are the pacemaker cells in the gastrointestinal system, initiating the rhythmic systematic contraction of smooth muscle to regulate peristalsis. Benign ICC are identified immunohistochemically by positive staining for CD117, c-kit tyrosine kinase receptor. CD117 expression is maintained during the malignant transformation of ICC into gastrointestinal stromal cell tumors (GIST). However, to date, no single reliable marker for GIST has been identified by immunohistochemical (IHC) staining, and correct diagnosis depends on IHC staining results using multiple markers. This study compared the reactivities of synemin (SYNM) intermediate filament protein and CD34, a known marker for stem cells, endothelial cells, and many GIST tumors, in 54 formalin-fixed, paraffin-embedded GIST, which were determined by this study to be CD117 positive. Double-immunofluorescence (IF) staining was also used to assess whether CD117 and SYNM were co-expressed by ICC. While 81.5% of the GIST were CD34+, 92.9% of these tumors were SYNM+. ICC were CD117+/SYNM+, whereas mast cells were CD117+/SYNM−. Because the percentage of CD117+/SYNM+ GIST was higher than the percentage of 117+/CD34+ GIST, this study suggested that SYNM was a better marker than CD34 for GIST diagnosis. In addition, differential expression of SYNM and CD117 helped distinguish between ICC and mast cells.

Cucurbitacin B induces inhibitory effects via the CIP2A/PP2A/C-KIT signaling axis in t(8;21) acute myeloid leukemia

Acute myeloid leukemia (AML) is the most common subtype of hematological malignancy in humans, and its incidence increases with age. The treatment of AML still faces challenges. Therefore, there is an urgent need to develop more effective targeted therapies. The receptor tyrosine kinase C-KIT confers critical proliferative signals to AML. Cancerous inhibitor of protein phosphatase 2A (CIP2A) is an endogenous inhibitor of protein phosphatase 2A (PP2A), which promotes the growth and transformation of various solid tumors. These actions make CIP2A a promising target for tumor treatment. Here, we reported the effects and underlying mechanisms of a natural compound, cucurbitacin B (CuB), on AML. We reported that CuB suppressed growth and induced apoptosis in AML cells. The inhibition of growth and activation of apoptosis were mediated through CuB-induced downregulation of the CIP2A/PP2A/C-KIT signal pathway. Furthermore, CuB inactivated the JAK2 and STAT3 molecules downstream of C-KIT via the downregulation of CIP2A. These results advance our understanding of CuB-induced growth inhibition and apoptosis and support further investigation of CuB as a CIP2A inhibitor for AML therapies.

Small Molecule Amyloid-β Protein Precursor Processing Modulators Lower Amyloid-β Peptide Levels via cKit Signaling.

Alzheimer's disease (AD) is characterized by the accumulation of neurotoxic amyloid-β (Aβ) peptides consisting of 39-43 amino acids, proteolytically derived fragments of the amyloid-β protein precursor (AβPP), and the accumulation of the hyperphosphorylated microtubule-associated protein tau. Inhibiting Aβ production may reduce neurodegeneration and cognitive dysfunction associated with AD. We have previously used an AβPP-firefly luciferase enzyme complementation assay to conduct a high throughput screen of a compound library for inhibitors of AβPP dimerization, and identified a compound that reduces Aβ levels. In the present study, we have identified an analog, compound Y10, which also reduced Aβ. Initial kinase profiling assays identified the receptor tyrosine kinase cKit as a putative Y10 target. To elucidate the precise mechanism involved, AβPP phosphorylation was examined by IP-western blotting. We found that Y10 inhibits cKit phosphorylation and increases AβPP phosphorylation mainly on tyrosine residue Y743, according to AβPP751 numbering. A known cKit inhibitor and siRNA specific to cKit were also found to increase AβPP phosphorylation and lower Aβ levels. We also investigated a cKit downstream signaling molecule, the Shp2 phosphatase, and found that known Shp2 inhibitors and siRNA specific to Shp2 also increase AβPP phosphorylation, suggesting that the cKit signaling pathway is also involved in AβPP phosphorylation and Aβ production. We further found that inhibitors of both cKit and Shp2 enhance AβPP surface localization. Thus, regulation of AβPP phosphorylation by small molecules should be considered as a novel therapeutic intervention for AD.

IPSC-Based Phenomic Screen Revealed an Impact of Uncontrolled NFkB Activity at the Initiating Stages of AML1-ETO Related Leukemia

Onset of acute myeloid leukemia (AML) has been accounted for by cooperation between multiple genetic alterations which induce abnormal control of various cellular pathways. Among the previously listed leukemogenic lesions, AML1-ETO fusion (AE) generated by translocation (8;21) (q22;q22) is one of the common mutations observed in 20-40% of patients. AE affects transcriptional regulation associated with hematopoietic differentiation, while 60% of AE-positive AML cases are shown to have together other types of mutation of genes involved in cell proliferation, such as receptor tyrosine kinase (RTK) c-kit and FLT3. However, the detailed mechanisms of how they work in the very early stages of leukemogenesis and what unknown “cooperative ” cues function in those periods. From this viewpoint, in order to identify novel cellular molecules involved in the acquisition of leukemic phenotypes, we have conducted the gene-trap strategy-based phenomic screen in the use of pluripotent stem cell (PSC)-derived hematopoietic culture.Through our screening, we found that the functional knockdown of a gene NSFL1c, also known as p47, enhanced the activities of hematopoietic progenitor cells harboring AE to show leukemic phenotype both in vivo and in vitro: Cells differentiated from AE-PSCs which have additionally the poly A trapping sequence inserted in NSFL1c locus showed doubled efficiency in engraftment into immunodeficient NOG mice than cells without trapping (3.1% v.s. 1.3%, 16 weeks after intra bone marrow transplantation), and also showed the significantly higher colony replating efficacy in methylcellulose colony forming assay.In order to clear what lineages of cells were most responsible for those phenomena, we next performed those colony forming experiments after sorting of CD34+CD43+CD13- immature cells, CD34+/-CD43+CD13+ myeloid cells and CD71+CD41+ erythro-megakaryocytic subpopulations of cells. As a result, CD34+/-CD43+CD13+ myeloid precursors showed the strongest tendencies to emerge highly proliferative clones followed by CD34+CD43+CD13- immature progenitors in the presence of NSF1c trapping. Interestingly, those activities were cancelled in the absence of AE expression.NSFL1c is one of the component of NEMO complex which binds to ubiquitinated NEMO and induces its degradation, resulting in reduced IKK and elevated NFkB activities. In AML, elevated NF-κB pathways have been detected in more than 30% of patients. Although NF-κB signaling networks have proved induced by inflammatory and immune signals, and previous studies in vivo and in vitro showed their abnormal activities make leukemia cells escape from cell death and go into abnormal proliferation, the detailed mechanisms of how they are involved in the pathogenesis, in particular at the very early stages of the leukemogenesis, are well not defined. Our data therefore reflect the novel mechanisms behind the deviation of progenitor cell fate from normal to abnormal pathway leading to the emergence of leukemic initiating cells, and suggested the myeloid-biased leukemogenic potentials. DisclosuresNo relevant conflicts of interest to declare.

EFFECT OF NATURAL AND SYNTHETIC FOOD COLORANTS ON SPERMATOGENESIS AND THE EXPRESSION OF ITS CONTROLLING GENES

The use of food additives is controversial. However, data regarding their effects on fertility genes are still very sparse. The present study was designed to assess the effects of two coloring agents, carmoisine (synthetic) and curcumin (natural) on the expression of some genes with fertility impact. Sixty three male Sprague-Dawley albino rats were orally administered carmoisine and curcumin in three doses, acceptable daily intake (ADI), 5x- and 10x- ADI for 15, 30, and 45 days. Sperm analysis and testicular expression level of biomarkers Testin, Glial cell derived neurotrophic factor (GDNF), tyrosine kinase receptor (c-KIT), follicle stimulating hormone receptor (FSHR), A kinase anchor protein 3 (PRKA3), spermatogenesis associated 7 (Spata7), Stage-specific embryonic antigen-1 (SSEA1) genes were measured and supported with histopathological studies on rat testes tissues. The recorded results revealed significant down regulation of the tested genes in rats supplemented with carmoisine in time and dose dependent manner. However, these declines were also observed after treatment with medium and high doses of curcumin. Sperm counts were significantly decreased after carmiosine treatment in a dose dependent manner, it was 74.6±6.36, 74.00±6.63, 49.00±0.28 and 147.00±3.2 for ADI, 5xADI, 10xADI and control group respectively, without any changes after curcumin treatment. Also, histopathological studies indicated deleterious effect with medium and high doses of carmiosine. In Conclusion, carmoisine induced hazardous effects on fertility at different levels when consumed in concentrations higher than the acceptable daily-authorized level (50 mg/kg b.wt). However, curcumin as a natural food color is saver than carmoisine up to certain levels.

Inhibition of MicroRNA-221 and 222 Enhances Hematopoietic Differentiation from Human Pluripotent Stem Cells via c-KIT Upregulation.

The stem cell factor (SCF)/c-KIT axis plays an important role in the hematopoietic differentiation of human pluripotent stem cells (hPSCs), but its regulatory mechanisms involving microRNAs (miRs) are not fully elucidated. Here, we demonstrated that supplementation with SCF increases the hematopoietic differentiation of hPSCs via the interaction with its receptor tyrosine kinase c-KIT, which is modulated by miR-221 and miR-222. c-KIT is comparably expressed in undifferentiated human embryonic and induced pluripotent stem cells. The inhibition of SCF signaling via treatment with a c-KIT antagonist (imatinib) during hPSC-derived hematopoiesis resulted in reductions in the yield and multi-lineage potential of hematopoietic progenitors. We found that the transcript levels of miR-221 and miR-222 targeting c-KIT were significantly lower in the pluripotent state than they were in terminally differentiated somatic cells. Furthermore, suppression of miR-221 and miR-222 in undifferentiated hPSC cultures induced more hematopoiesis by increasing c-KIT expression. Collectively, our data implied that the modulation of c-KIT by miRs may provide further potential strategies to expedite the generation of functional blood cells for therapeutic approaches and the study of the cellular machinery related to hematologic malignant diseases such as leukemia.

Low plasma stem cell factor combined with high transforming growth factor-α identifies high-risk patients in pulmonary arterial hypertension

In pulmonary arterial hypertension (PAH), severe vasoconstriction and remodelling of small pulmonary arteries result in high mortality. Receptor tyrosine kinases and their ligands, such as transforming growth factor (TGF)-α, modulate proliferation in PAH. Although the receptor tyrosine kinase c-Kit has been shown to be overexpressed in PAH, the expression and role of its ligand stem cell factor (SCF) remain unknown. However, low plasma SCF levels are known to be linked to higher cardiovascular mortality risk.Using proximity extension assays, we measured SCF and TGF-α in venous plasma from treatment-naïve PAH patients and healthy controls. Patients were stratified into risk classes based on PAH guidelines.Plasma SCF was decreased (p=0.013) and TGF-α was increased (p<0.0001) in PAH patients compared to controls. SCF correlated to pulmonary vascular resistance (r=−0.66, p<0.0001), cardiac index (r=0.66, p<0.0001), venous oxygen saturation (r=0.47, p<0.0008), mean right atrial pressure (r=−0.44, p<0.002) and N-terminal pro-brain natriuretic protein (r=−0.39, p<0.006). SCF was lower in “high-risk” compared to “intermediate-risk” (p=0.0015) or “low-risk” (p=0.0009) PAH patients. SCF and TGF-α levels combined (SCF/TGF-α) resulted in 85.7% sensitivity and 81.5% specificity for detecting high-risk patients (p<0.0001). Finally, REVEAL (Registry to Evaluate Early and Long-Term Pulmonary Arterial Hypertension Disease Management) risk scores in PAH patients correlated to SCF/TGF-α levels (r=−0.50, p=0.0003).In conclusion, low plasma SCF combined with high TGF-α identifies high-risk PAH patients at baseline. Lower circulating SCF levels, which are associated with worse haemodynamics, may be related to the c-Kit accumulation previously observed in PAH.

β-Cell Receptor Tyrosine Kinases in Controlling Insulin Secretion and Exocytotic Machinery: c-Kit and Insulin Receptor.

Insulin secretion from pancreatic β-cells is initiated through channel-mediated depolarization, cytoskeletal remodeling, and vesicle tethering at the cell membrane, all of which can be regulated through cell surface receptors. Receptor tyrosine kinases (RTKs) promote β-cell development and postnatal signaling to improve β-cell mass and function, yet their activation has also been shown to initiate exocytotic events in β-cells. This review examines the role of RTK signaling in insulin secretion, with a focus on RTKs c-Kit and insulin receptor (IR). Pathways that control insulin release and the potential interplay between c-Kit and IR signaling are discussed, along with clinical implications of RTK therapy on insulin secretion.

Microenvironment-Induced Non-sporadic Expression of the AXL and cKIT Receptors Are Related to Epithelial Plasticity and Drug Resistance.

The existence of rare cancer cells that sporadically acquire drug-tolerance through epigenetic mechanisms is proposed as one mechanism that drives cancer therapy failure. Here we provide evidence that specific microenvironments impose non-sporadic expression of proteins related to epithelial plasticity and drug resistance. Microarrays of robotically printed combinatorial microenvironments of known composition were used to make cell-based functional associations between microenvironments, which were design-inspired by normal and tumor-burdened breast tissues, and cell phenotypes. We hypothesized that specific combinations of microenvironment constituents non-sporadically impose the induction of the AXL and cKIT receptor tyrosine kinase proteins, which are known to be involved in epithelial plasticity and drug-tolerance, in an isogenic human mammary epithelial cell (HMEC) malignant progression series. Dimension reduction analysis reveals type I collagen as a dominant feature, inducing expression of both markers in pre-stasis finite lifespan HMECs, and transformed non-malignant and malignant immortal cell lines. Basement membrane-associated matrix proteins, laminin-111 and type IV collagen, suppress AXL and cKIT expression in pre-stasis and non-malignant cells. However, AXL and cKIT are not suppressed by laminin-111 in malignant cells. General linear models identified key factors, osteopontin, IL-8, and type VIα3 collagen, which significantly upregulated AXL and cKIT, as well as a plasticity-related gene expression program that is often observed in stem cells and in epithelial-to-mesenchymal-transition. These factors are co-located with AXL-expressing cells in situ in normal and breast cancer tissues, and associated with resistance to paclitaxel. A greater diversity of microenvironments induced AXL and cKIT expression consistent with plasticity and drug-tolerant phenotypes in tumorigenic cells compared to normal or immortal cells, suggesting a reduced perception of microenvironment specificity in malignant cells. Microenvironment-imposed reprogramming could explain why resistant cells are seemingly persistent and rapidly adaptable to multiple classes of drugs. These results support the notion that specific microenvironments drive drug-tolerant cellular phenotypes and suggest a novel interventional avenue for preventing acquired therapy resistance.

Radiosensitization Through Targeting Molecular Alterations in Adenoid Cystic Carcinoma

Adenoid cystic carcinoma (ACC) is a relatively rare cancer that typically arises in salivary tissues of the head and neck. There are currently no approved systemic agents for ACC and no data supporting the delivery of chemoradiation for ACC patients. The scarcity of validated model systems has hampered research efforts. We report the establishment and propagation of an ACC patient–derived xenograft (PDX), genomic evaluation of cancer-associated mutations, and in vivo response profiles to personalized radiosensitization agents based on next-generation sequencing. An ACC PDX was established and maintained in NOD-SCID gamma (NSG) mice directly from the patient. Common cancer-associated mutations were identified using the Illumina TruSeq Amplicon Cancer panel. PDXs were treated with focal radiation or chemotherapy selected based on the genomic profile of the cancer. Focal radiation was delivered at 5 Gy x 8 fractions twice weekly for 4 weeks. Tumor size was measured over time and comparisons between treatment groups made by repeated measures ANOVA. Target inhibition in vivo was confirmed via western blot of tumor lysates and IHC of FFPE tissue. The histologic and physical characteristics of the primary human tumor are maintained in this ACC PDX. Mutations in the receptor tyrosine kinases (RTKs) cKit and KDR/VEGFR2 were identified. No mutations were identified in EGFR, RAS, or PIK3CA. Several targeted therapies were selected including dovitinib, a multi-RTK inhibitor, BEZ235, a PI3K/mTORC inhibitor, and cetuximab, an EGFR mAB. Target inhibition was confirmed by western blot and IHC. Radiation temporarily halted tumor growth. Treatment with molecularly targeted agents prolonged time to tumor doubling compared to control treatment (p<0.05 for each). Chemoradiation resulted in significant tumor regression which persisted more than 2 months after the end of treatment. PDXs are a powerful model system for investigating potential radiosensitizers based on individual tumor characteristics. Our ACC PDX represents one of only a handful of tools for studying this rare disease. These preliminary data identify the rationale to investigate selected molecular drug/radiation combinations for ACC, particularly when driven by tumor-specific genetic biomarkers. Expansion of these studies may be valuable to advance the design of new treatment strategies for ACC.

Oxidized phospholipids stimulate production of stem cell factor via NRF2-dependent mechanisms

Receptor tyrosine kinase c-Kit and its ligand stem cell factor (SCF) regulate resident vascular wall cells and recruit circulating progenitors. We tested whether SCF may be induced by oxidized palmitoyl-arachidonoyl-phosphatidylcholine (OxPAPC) known to accumulate in atherosclerotic vessels. Gene expression analysis demonstrated OxPAPC-induced upregulation of SCF mRNA and protein in different types of endothelial cells (ECs). Elevated levels of SCF mRNA were observed in aortas of ApoE−/− knockout mice. ECs produced biologically active SCF because conditioned medium from OxPAPC-treated cells stimulated activation (phosphorylation) of c-Kit in naïve ECs. Induction of SCF by OxPAPC was inhibited by knocking down transcription factor NRF2. Inhibition or stimulation of NRF2 by pharmacological or molecular tools induced corresponding changes in SCF expression. Finally, we observed decreased levels of SCF mRNA in aortas of NRF2 knockout mice. We characterize OxPLs as a novel pathology-associated stimulus inducing expression of SCF in endothelial cells. Furthermore, our data point to transcription factor NRF2 as a major mediator of OxPL-induced upregulation of SCF. This mechanism may represent one of the facets of pleiotropic action of NRF2 in vascular wall.

Paclitaxel With and Without Pazopanib for Persistent or Recurrent Ovarian Cancer

Ovarian cancer is the leading cause of gynecologic cancer deaths in the United States. Pazopanib is an oral, multitarget kinase inhibitor of vascular endothelial growth factor receptors 1, 2, and 3; platelet-derived growth factor receptors α and β; and proto-oncogene receptor tyrosine kinase (c-KIT). To estimate the progression-free survival (PFS) hazard ratio (HR) of weekly paclitaxel and pazopanib compared with weekly paclitaxel and placebo in women with recurrent ovarian cancer. Secondary objectives included frequency and severity of adverse events, proportion responding, and overall survival (OS) in each arm. Translational research objectives included exploring the association between possible biomarkers and single-nucleotide polymorphisms in vascular endothelial growth factor A, interleukin 8, and hypoxia-inducible factor 1α; and PFS, OS, and proportion responding. A randomized, placebo-controlled, double-blind phase 2 study was conducted at 26 participating institutions. Patients were enrolled between December 12, 2011, and April 22, 2013. Data were frozen on August 11, 2014. Participants were patients with persistent or recurrent epithelial ovarian, fallopian tube, or primary peritoneal carcinoma with 1 to 3 prior regimens and performance status of 0 to 2. One hundred six patients enrolled; 100 were evaluable for toxic effects. All patients received paclitaxel 80 mg/m2 intravenously on days 1, 8, and 15 every 28 days and were randomized 1:1 to pazopanib 800 mg orally daily or placebo. The primary end point was PFS. The study was designed to detect a 37.5% reduction in the hazard with 80% power (α = 10%). A total of 106 women (median age [range], 61 [35-87] years; 88 [83%] white) were enrolled. Study arms were well balanced for age, performance status, measurable disease, and prior bevacizumab. Proportion responding was 14 of 44 (31.8%) vs 10 of 44 (22.7%) for pazopanib plus paclitaxel vs paclitaxel alone. Median PFS was 7.5 vs 6.2 months for pazopanib plus paclitaxel vs paclitaxel alone, respectively (HR, 0.84; 90% CI, 0.57-1.22; P = .20). Median OS was 20.7 vs 23.3 months for pazopanib plus paclitaxel vs paclitaxel alone (HR, 1.04; 90% CI, 0.60-1.79; P = .90). Severe hypertension was more common on the pazopanib plus paclitaxel arm (relative risk, 12.0; 95% CI, 1.62-88.84). More patients discontinued treatment on the paclitaxel arm for disease progression (34 of 52 [65.4%] vs 17 of 54 [31.5%]), and more on the pazopanib plus paclitaxel arm for adverse events (20 of 54 [37%] vs 5 of 52 [9.6%]). No association was found between single-nucleotide polymorphisms (interleukin 8 and hypoxia-inducible factor 1α) and OS and proportion responding. Patients with VEGFA CC genotype may be more resistant to weekly paclitaxel than those with the AC or AA genotype, with 1 of 14 (7%), 3 of 15 (20%), and 4 of 8 (50%) responding, respectively. The combination of pazopanib plus paclitaxel is not superior to paclitaxel in women with recurrent ovarian cancer. clinicaltrials.gov Identifier: NCT01468909.

MNK1/2 inhibition limits oncogenicity and metastasis of KIT-mutant melanoma.

Melanoma can be stratified into unique subtypes based on distinct pathologies. The acral/mucosal melanoma subtype is characterized by aberrant and constitutive activation of the proto-oncogene receptor tyrosine kinase C-KIT, which drives tumorigenesis. Treatment of these melanoma patients with C-KIT inhibitors has proven challenging, prompting us to investigate the downstream effectors of the C-KIT receptor. We determined that C-KIT stimulates MAP kinase-interacting serine/threonine kinases 1 and 2 (MNK1/2), which phosphorylate eukaryotic translation initiation factor 4E (eIF4E) and render it oncogenic. Depletion of MNK1/2 in melanoma cells with oncogenic C-KIT inhibited cell migration and mRNA translation of the transcriptional repressor SNAI1 and the cell cycle gene CCNE1. This suggested that blocking MNK1/2 activity may inhibit tumor progression, at least in part, by blocking translation initiation of mRNAs encoding cell migration proteins. Moreover, we developed an MNK1/2 inhibitor (SEL201), and found that SEL201-treated KIT-mutant melanoma cells had lower oncogenicity and reduced metastatic ability. Clinically, tumors from melanoma patients harboring KIT mutations displayed a marked increase in MNK1 and phospho-eIF4E. Thus, our studies indicate that blocking MNK1/2 exerts potent antimelanoma effects and support blocking MNK1/2 as a potential strategy to treat patients positive for KIT mutations.

N-Acetylcysteine Compared to Metformin, Improves The Expression Profile of Growth Differentiation Factor-9 and Receptor Tyrosine Kinase c-Kit in The Oocytes of Patients with Polycystic Ovarian Syndrome.

BackgroundParacrine disruption of growth factors in women with polycystic ovarian syndrome (PCOS) results in production of low quality oocyte, especially following ovulation induction. The aim of this study was to investigate the effects of metformin (MET), N-acetylcysteine (NAC) and their combination on the hormonal levels and expres- sion profile of GDF-9, BMP-15 and c-kit, as hallmarks of oocyte quality, in PCOS patients.Materials and MethodsThis prospective randomized, double-blind, placebo controlled trial aims to study the effects of MET, NAC and their combination (MET+NAC) on expression of GDF-9, BMP-15 and c-kit mRNA in oocytes [10 at the germinal vesicle (GV) stage, 10 at the MI stage, and 10 at the MII stage from per group] derived following ovulation induction in PCOS. Treatment was carried out for six weeks, starting on the third day of previous cycle until oocyte aspiration. The expression of GDF9, BMP15 and c-kit were determined by quantitative real time polymerase chain reaction (RT-qPCR) and western blot analysis. Data were analyzed with one-way ANOVA.ResultsThe follicular fluid (FF) level of c-kit protein significantly decreased in the NAC group compared to the other groups. Significant correlations were observed between the FF soluble c-kit protein with FF volume, androstenedione and estradiol. The GDF-9 expression in unfertilized mature oocytes were significantly higher in the NAC group com- pared to the other groups (P<0.001). Similar difference was not observed between the MET, NAC+MET and control groups. The c-kit expression in unfertilized mature oocytes were significantly lower in the NAC group compared to the other groups (P<0.001). Similar difference was not observed between the MET, NAC+MET and control groups (Registration number: IRCT201204159476N1).ConclusionWe concluded that NAC can improve the quality of oocytes in PCOS.

Inhibition of the phosphatase STS1 in acute myeloid leukemia

The class III receptor tyrosine kinases (RTKs) FLT3 and c-KIT play a central role in normal and malignant hematopoiesis. After binding to their natural ligands, these RTKs dimerize, become autophosphorylated and activate an intracellular signaling cascade. Negative RTK regulation by dephosphorylation, ubiquitination and degradation are equally important to prevent uncontrolled kinase activity and downstream signaling in normal and malignant hematopoiesis. Recently, we identified STS1/STS2 as the phosphatases of FLT3 and c-KIT (Zhang J. et al, Stem Cell Reports, 2015). Loss of STS1/STS2 causes hyperphosphorylation of FLT3, enhanced AKT signaling and a strong proliferative advantage of hematopoietic stem and progenitors cells in STS1/ STS2 knockout mice. This indicates that STS1 and STS2 serve as negative regulators for wild-type FLT3 kinase activity and normal hematopoiesis. Internal tandem duplications of FLT3 (FLT3-ITD) are found in up to 30% of patients with acute myeloid leukemia (AML). Here, we investigated the function of STS1/ STS2 in FLT3-ITD induced malignant transformation. Surprisingly we found that loss of STS1 decreased the transforming capacity of the FLT3-ITD mutant, demonstrated by both reduced cell proliferation and colony forming ability. Importantly, the overexpression of STS1 enhanced FLT3-ITD induced cytokine independent cell growth in vitro in a phosphatase-dependent manner. Bone marrow transplantation results recapitulated the collaboration between FLT3-ITD and STS1/STS2, manifested by the increased engraftment of FLT3-ITD and STS1/STS2 co-expressing cells in vivo. Biological analyses showed prolonged half-life of FLT3-ITD, as well as increased downstream signaling in STS1 over-expressing cells. Mechanistically, the E3 ligase activity of CBL was negatively regulated by STS1. In summary, STS1/STS2 demonstrated two distinct roles in the context of FLT3wt and FLT3-ITD. Our data suggests that the phosphatase inhibition of STS1/STS2 may both improve hematopoietic recovery of normal hematopoiesis and decrease the leukemic potential of FLT3-ITD expressing blasts. Inhibiting STS1 may provide a novel therapeutic in FLT3-ITD positive AML.

The stem cell factor (SCF)/c-KIT system in carcinogenesis of reproductive tissues: What does the hormonal regulation tell us?

The tyrosine kinase receptor c-KIT and its ligand, the stem cell factor (SCF) are expressed in several tissues of male and female reproductive tract, playing an important role in the regulation of basic biological processes. The activation of c-KIT by SCF controls, cell survival and death, cell differentiation and migration. Also, the SCF/c-KIT system has been implicated in carcinogenesis of reproductive tissues due to its altered expression pattern or overactivation in consequence of gain-of-functions mutations. Over the years, it has also been shown that hormones, the primary regulators of reproductive function and causative agents in the case of hormone-dependent cancers, are also able to control the SCF/c-KIT tissue levels. Therefore, it is liable to suppose that disturbed SCF/c-KIT expression driven by (de)regulated hormone actions can be a relevant step towards carcinogenesis. The present review describes the SCF and c-KIT expression in cancers of reproductive tissues, discussing the implications of the hormonal regulation of the SCF/c-KIT system in cancer development. Understanding the relationship between hormonal imbalance and the SCF/c-KIT expression and activity would be relevant in the context of novel therapeutic approaches in reproductive cancers.