Signaling by Kit protein-tyrosine kinase--the stem cell factor receptor

Diosmetin as a promising natural therapeutic agent: In vivo, in vitro mechanisms, and clinical studies

Diosmetin, a natural occurring flavonoid, is primarily found in citrus fruits, beans, and other plants. Diosmetin demonstrates a variety of pharmacological activities, including anticancer, antioxidant, anti-inflammatory, antibacterial, metabolic regulation, cardiovascular function improvement, estrogenic effects, and others. The process of literature search was done using PubMed, Web of Science and ClinicalTrials databases with search terms containing Diosmetin, content, anticancer, anti-inflammatory, antioxidant, pharmacological activity, pharmacokinetics, in vivo, and in vitro. The aim of this review is to summarize the in vivo, in vitro and clinical studies of Diosmetin over the last decade, focusing on studies related to its anticancer, anti-inflammatory, and antioxidant activities. It is found that DIO has significant therapeutic effects on skin and cardiovascular system diseases, and its research in pharmacokinetics and toxicology is summarized. It provides the latest information for researchers and points out the limitations of current research and areas that should be strengthened in future research, so as to facilitate the relevant scientific research and clinical application of DIO.

Sarco/endoplasmic reticulum calcium ATPase 3 (SERCA3) expression in gastrointestinal stromal tumours

Accurate characterisation of gastrointestinal stromal tumours (GIST) is important for prognosis and the choice of targeted therapies. Histologically the diagnosis relies on positive immunostaining of tumours for KIT (CD117) and DOG1. Here we report that GISTs also abundantly express the type 3 Sarco/Endoplasmic Reticulum Calcium ATPase (SERCA3). SERCA enzymes transport calcium ions from the cytosol into the endoplasmic reticulum and play an important role in regulating the intensity and the periodicity of calcium-induced cell activation. GISTs from various localisations, histological and molecular subtypes or risk categories were intensely immunopositive for SERCA3 with the exception of PDGFRA-mutated cases where expression was high or moderate. Strong SERCA3 expression was observed also in normal and hyperplastic interstitial cells of Cajal. Decreased SERCA3 expression in GIST was exceptionally observed in a zonal pattern, where CD117 staining was similarly decreased, reflecting clonal heterogeneity. In contrast to GIST, SERCA3 immunostaining of spindle cell tumours and other gastrointestinal tumours resembling GIST was negative or weak. In conclusion, SERCA3 immunohistochemistry may be useful for the diagnosis of GIST with high confidence, when used as a third marker in parallel with KIT and DOG1. Moreover, SERCA3 immunopositivity may be particularly helpful in cases with negative or weak KIT or DOG1 staining, a situation that may be encountered de novo, or during the spontaneous or therapy-induced clonal evolution of GIST.

KIT Mutations and Other Genetic Defects in Mastocytosis: Implications for Disease Pathology and Targeted Therapies

A KIT activating mutation (usually KIT D816V) is detected in neoplastic cells in greater than 90% of indolent patients with systemic mastocytosis (SM). In more advanced variants of SM, additional genetic defects can be found in several myeloid malignancy-related genes, which can be detected by applying next-generation sequencing. Currently, the techniques recommended to detect the KIT D816V mutation and quantify the mutational burden in peripheral blood, bone marrow, or other organs/tissues are allele specific-quantitative PCR or droplet digital PCR. These techniques are useful for diagnosis, prognostication, follow-up and monitoring of therapeutic efficacy of cytoreductive agents in patients with SM.

Impact of KIT Editing on Coat Pigmentation and Fresh Meat Color in Yorkshire Pigs

The white coat color of Yorkshire pigs is caused by the dominant white I allele, which has been associated with at least one copy of the 450-kb duplication encompassing the entire KIT gene and a splice mutation (G > A) at the first base of intron 17. The splice mutation in KIT has an adverse effect on pigmentation in mice. Therefore, removing the 450 kb duplications harboring the KIT copy with splice mutations is expected to affect Yorkshire pig pigmentation. In this study, we describe the use of a Yorkshire pig kidney cell strain with the I^?/I^Be-ed genotype, previously created by CRISPR-Cas9, as donor cells for somatic cell nuclear transfer to generate gene-edited Yorkshire pigs. The removal of the 450 kb duplications harboring the KIT copy with splice mutation did not alter the white coat color of Yorkshire pigs, which was confirmed by the absence of fully mature melanocytes and melanin accumulation in the hair follicles. Except for the improved transcription of tyrosinase, and slight increase in microphthalmia transcription factor and tyrosinase-related protein 1 protein expression, there was no significant impact of the removal of splice mutations on genes and signaling pathways (PI3K/AKT) involved in melanogenesis. However, the removal of the 450 kb duplications harboring the KIT copy with splice mutation substantially improved fresh meat color accompanied by significantly increased red blood cell number, which merits further investigation. Our study provides new insights into the role of structural mutations of the KIT gene in the formation of white coat color and erythropoiesis in Yorkshire pigs.

Mouse dendritic cells in the steady state: Hypoxia, autophagy, and stem cell factor

Dendritic cells (DCs) are innate immune cells with a central role in immunity and tolerance. Under steady-state, DCs are scattered in tissues as resting cells. Upon infection or injury, DCs get activated and acquire the full capacity to prime antigen-specific CD4⁺ and CD8⁺ T cells, thus bridging innate and adaptive immunity. By secreting different sets of cytokines and chemokines, DCs orchestrate diverse types of immune responses, from a classical proinflammatory to an alternative pro-repair one. DCs are highly heterogeneous, and physiological differences in tissue microenvironments greatly contribute to variations in DC phenotype. Oxygen tension is normally low in some lymphoid areas, including bone marrow (BM) hematopoietic niches; nevertheless, the possible impact of tissue hypoxia on DC physiology has been poorly investigated. We assessed whether DCs are hypoxic in BM and spleen, by staining for hypoxia-inducible-factor-1α subunit (HIF-1α), the master regulator of hypoxia-induced response, and pimonidazole (PIM), a hypoxic marker, and by flow cytometric analysis. Indeed, we observed that mouse DCs have a hypoxic phenotype in spleen and BM, and showed some remarkable differences between DC subsets. Notably, DCs expressing membrane c-kit, the receptor for stem cell factor (SCF), had a higher PIM median fluorescence intensity (MFI) than c-kit^- DCs, both in the spleen and in the BM. To determine whether SCF (a.k.a. kit ligand) has a role in DC hypoxia, we evaluated molecular pathways activated by SCF in c-kit⁺ BM-derived DCs cultured in hypoxic conditions. Gene expression microarrays and gene set enrichment analysis supported the hypothesis that SCF had an impact on hypoxia response and inhibited autophagy-related gene sets. Our results suggest that hypoxic response and autophagy, and their modulation by SCF, can play a role in DC homeostasis at the steady state, in agreement with our previous findings on SCF's role in DC survival.

Does the use of the Bruton Tyrosine Kinase inhibitors and the c-kit inhibitor masitinib result in clinically significant outcomes among patients with various forms of multiple sclerosis?

Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system accompanied by chronic inflammation, axonal loss, and neurodegeneration. Traditionally, MS has been thought of as a T-cell mediated disease, but research over the past decade has demonstrated the importance of B cells in both acute demyelination and disease progression. The highly selective irreversible Bruton Tyrosine Kinase (BTK) inhibitors evobrutinib, tolebrutinib, and orelabrutinib, and the reversible BTK inhibitor fenebrutinib, all target B-cell activation and aspects of innate immunity, including macrophage and microglia biology. The c-KIT inhibitor masitinib mitigates neuroinflammation by controlling the survival, migration, and degranulation of mast cells, leading to the inhibition of proinflammatory and vasoactive molecular cascades that result from mast cell activation. This article will review and critically appraise the ongoing clinical trials of two classes of receptor tyrosine kinase inhibitors that are emerging as potential medical treatments for the varying subtypes of MS: BTK inhibitors and c-KIT inhibitors. Specifically, this review will attempt to answer whether BTK inhibitors have measurable positive clinical effects on patients with RRMS, SPMS with relapses, relapse-free SPMS, and PPMS through their effect on MRI T1 lesions; annualized relapse rate; EDSS scale; MSFC score; and time to onset of composite 12-week confirmed disability progression. Additionally, this review will examine the literature to determine if masitinib has positive clinical effects on patients with PPMS or relapse-free SPMS through its effect on EDSS or MSFC scores.

EventPointer 3.0: flexible and accurate splicing analysis that includes studying the differential usage of protein-domains

Alternative splicing (AS) plays a key role in cancer: all its hallmarks have been associated with different mechanisms of abnormal AS. The improvement of the human transcriptome annotation and the availability of fast and accurate software to estimate isoform concentrations has boosted the analysis of transcriptome profiling from RNA-seq. The statistical analysis of AS is a challenging problem not yet fully solved. We have included in EventPointer (EP), a Bioconductor package, a novel statistical method that can use the bootstrap of the pseudoaligners. We compared it with other state-of-the-art algorithms to analyze AS. Its performance is outstanding for shallow sequencing conditions. The statistical framework is very flexible since it is based on design and contrast matrices. EP now includes a convenient tool to find the primers to validate the discoveries using PCR. We also added a statistical module to study alteration in protein domain related to AS. Applying it to 9514 patients from TCGA and TARGET in 19 different tumor types resulted in two conclusions: i) aberrant alternative splicing alters the relative presence of Protein domains and, ii) the number of enriched domains is strongly correlated with the age of the patients.

Tissue distribution of stem cell factor in adults

Stem cell factor (SCF) is an essential cytokine during development and is necessary for gametogenesis, hematopoiesis, mast cell development, stem cell function, and melanogenesis. Here, we measure SCF concentration and distribution in adult humans and mice using gene expression analysis, tissue staining, and organ protein lysates. We demonstrate continued SCF expression in many cell types and tissues into adulthood. Tissues with high expression in adult humans included stomach, spleen, kidney, lung, and pancreas. In mice, we found high SCF expression in the esophagus, ovary, uterus, kidney, and small intestine. Future studies may correlate our findings of increased, organ-specific SCF concentrations within adult tissues with increased risk of SCF/CD117-related disease.

The safety of VASApos presumptive adult ovarian stem cells

Isolation and characterization of presumptive human adult ovarian stem cells (OSC) has broken the long standing dogma of the absence of postnatal neo-oogenesis. Human adult OSC have been immunosorted by antibodies reacting against the RNA helicase VASA and have been reported to engraft into appropriate stem cell niches to promote neo-oogenesis. Analysis of published research, however, questions some of the findings on isolation, characterization, in-vitro self-renewal and clinical safety of the presumptive human adult OSC. In the present study, human VASA^pos embryo-fetal primordial germ cells and presumptive adult OSC are shown to share several pluripotency and early germ cell markers not ascertained in the initial characterization of adult OSC. A new hypothesis is made that the restoration of fertility claimed to result from presumptive human adult OSC may be attributed instead to VASA^pos embryo-fetal primordial germ cell remnants in the adult ovary, or alternatively to earlier VASA^neg germ cells generated by in-vitro de-differentiation of the presumptive OSC. The suggested hypotheses have extensive implications for the practice and safety of adult OSC in the development of new treatments aimed at rescuing the ovarian reserve.

Quantitative characterization of human oncogene promoter G-quadruplex DNA-ligand interactions using a combination of mass spectrometry and capillary electrophoresis

Human c-KIT oncogene is known to regulate cell growth and proliferation, and thus, acts as a probable target in the treatment of gastrointestinal tumors (GIST). To identify small molecule ligands which can specifically bind with the G-quadruplex (G4) in the c-KIT promoter region as potential antitumor agents, we propose the combination of electrospray ionization-mass spectrometry (ESI-MS), capillary electrophoresis frontal analysis (CE-FA), and Taylor dispersion analysis (TDA) to accurately investigate the G4/ligands binding properties. First, ESI-MS was used for initial screening of natural products (NPs). CE-FA was then used to calculate specific binding constants and the stoichiometry of the native state binding pair in solution. Next, TDA, a micro-capillary flow technique was used to examine the effect of the ligand binding on the diffusivity and particle size of the c-KIT G4. Two of the screened NPs, scopolamine butylbromide (L1) and isorhamnetin-3-O-neohesperidoside (L3), were found to specifically bind to the c-KIT G4 with binding constants of around 10⁴ M^-1 and 1:1 stoichiometry in a free solution. TDA data showed that ligand binding (both L1 and L3) induced the c-KIT strands to fold into a tightly structured G4 with a decreased hydrodynamic radius. These ligands have the potential to be drug candidates for the regulation of c-KIT gene transcription by stabilizing the G4 structure. This methodology not only increased the speed of analysis but also improved its accuracy and specificity compared with the conventional binding approaches.

Detecting the formation of human c-KIT oncogene promoter G-Quadruplex by Taylor dispersion analysis

The formation of G-quadruplex (G4) structures in oncogenic G-rich promoter regions are implicated in their biological functions, especially the inhibition of transcription. The binding of cations is thought to contribute to the stabilization of the G4 formation and competition against the duplex formation in the genomic sequence. Furthermore, it might affect the recognition of DNA-binding proteins. Therefore, measuring the interaction between G4 DNA and cations in a free solution environment is critical for evaluating G4 DNA biological functions. However, how binding to cations (K⁺ and NH₄⁺) affects the folding equilibrium of the G4 structure remains unclear. In this work, a Taylor dispersion analysis (TDA) method using a capillary electrophoresis (CE) instrument was established for the quantitative characterization of the cation-dependent G4 formation in the human c-KIT oncogene promoter region, as well as diffusivities and hydrodynamic radii of DNA variations before and after folding. Our results showed that both K⁺ and NH₄⁺ can induce the random-coiled c-KIT DNA to unfold and form a more unstretched intermediate state and then fold into tightly structured G4s with smaller size. The G4 size induced by NH₄⁺ was smaller than that induced by K⁺ ions, though these two cations induced the c-KIT G4 DNA formation with similar binding constants (order of magnitude around 10⁶ M^-1). The TDA method can be widely used for rapid structural analyses of trace amounts of DNA mixtures, which effectively differentiate DNA variations or DNA-ligand complex conformations.

RTK Inhibitors in Melanoma: From Bench to Bedside

MAPK (mitogen activated protein kinase) and PI3K/AKT (Phosphatidylinositol-3-Kinase and Protein Kinase B) pathways play a key role in melanoma progression and metastasis that are regulated by receptor tyrosine kinases (RTKs). Although RTKs are mutated in a small percentage of melanomas, several receptors were found up regulated/altered in various stages of melanoma initiation, progression, or metastasis. Targeting RTKs remains a significant challenge in melanoma, due to their variable expression across different melanoma stages of progression and among melanoma subtypes that consequently affect response to treatment and disease progression. In this review, we discuss in details the activation mechanism of several key RTKs: type III: c-KIT (mast/stem cell growth factor receptor); type I: EGFR (Epidermal growth factor receptor); type VIII: HGFR (hepatocyte growth factor receptor); type V: VEGFR (Vascular endothelial growth factor), structure variants, the function of their structural domains, and their alteration and its association with melanoma initiation and progression. Furthermore, several RTK inhibitors targeting the same receptor were tested alone or in combination with other therapies, yielding variable responses among different melanoma groups. Here, we classified RTK inhibitors by families and summarized all tested drugs in melanoma indicating the rationale behind the use of these drugs in each melanoma subgroups from preclinical studies to clinical trials with a specific focus on their purpose of treatment, resulted effect, and outcomes.

Properties of FDA-approved small molecule phosphatidylinositol 3-kinase inhibitors prescribed for the treatment of malignancies

The discovery of the phosphatidylinositol 3-kinase (PI 3-kinase) pathway was a major advance in understanding eukaryotic signal transduction. The high frequency of PI 3-kinase pathway mutations in many cancers stimulated the development of drugs targeting these oncogenic mutants. The PI 3-kinases are divided into three classes and Class I PI 3-kinases, which catalyze the phosphorylation of phosphatidylinositol-4,5-bisphosphate (PI-4,5-P2) to generate phosphatidylinositol-3,4,5-trisphosphate (PIP3), are the main subject of this review. The class I PI 3-kinases are made up of p110α, p110β, p110δ, and p110γ catalytic subunits. These catalytic subunits are constitutively bound to regulatory subunits (p85α, p85β, p55γ, p101, and p87 proteins). The p85/p55 regulatory subunits heterodimerize with p110α or p110δ thereby forming complexes that are regulated chiefly by receptor protein-tyrosine kinases. The p101 and p87 subunits heterodimerize with p110γ to form complexes that are regulated mainly by G protein-coupled receptors (GPCRs). Complexes containing the p110β subunit are activated by receptor protein-tyrosine kinases as well as GPCRs. Following the generation of PIP3, the AKT and mTOR protein-serine/threonine kinases are activated leading to cell growth, proliferation, and survival. Like protein kinases, the PI 3-kinase domains consist of a bilobed structure connected by a hinge-linker segment. ATP and most PI 3-kinase and protein kinase inhibitors form hydrogen bonds with hinge residues. The small and large lobes of PI 3-kinases and protein kinases have a very similar three-dimensional structure called the protein kinase fold. Both PI 3-kinases and eukaryotic protein kinases possess an activation segment that begins with a DFG triad (Asp-Phe-Gly); the activation segment of protein kinases usually ends with an APE (Ala-Pro-Glu) signature while that of PI 3-kinases ends with a PFxLT (Pro-Phe-Xxx-Leu-Thr) signature. Dormant PI 3-kinases have a collapsed activation loop and active PI 3-kinases have an extended activation loop. The distance between the α-carbon atom of the DFG-D residue at the beginning of the activation loop and that of the PFxLT-F residue at the end of the activation loop in dormant PI 3-kinases is about 13 Å; this distance in active PI 3-kinases is about 18 Å. The protein kinase catalytic loop has an HRD (His-Arg-Asp) signature while that of the PI 3-kinases reverses the order with a DRH triad. Alpelisib is an orally effective FDA-approved PI 3-kinase-α inhibitor used for the treatment of breast cancer. Copanlisib, duvelisib, idelalisib, and umbralisib are PI 3-kinase-δ inhibitors that are approved for the third-line treatment of follicular lymphomas and other hematological disorders. Copanlisib is also a potent inhibitor of PI 3-kinase-α. Of the five approved drugs, all are orally bioavailable except copanlisib. Idelalisib interacts with the active conformation of PI 3-kinase-δ and is classified as a type I inhibitor. Alpelisib and copanlisib interact with inactive PI 3-kinase-α and PI 3-kinase-γ, respectively, and are classified as a type I½ antagonists. Except for umbralisib with a molecular weight of 571.5, all five drugs conform to the Lipinski rule of five for oral effectiveness. Copanlisib, however, must be given intravenously. Alpelisib and copanlisib inhibit PI 3-kinase-α, which is involved in insulin signaling, and both drugs promote insulin-resistance and produce hyperglycemia. The five FDA-approved PI 3-kinase inhibitors produce significant on-target toxicities, more so than many approved protein kinase antagonists. The development of PI 3-kinase inhibitors with fewer toxicities is an important long-term therapeutic goal.

The dark side of daylight: photoaging and the tumor microenvironment in melanoma progression

Continued thinning of the atmospheric ozone, which protects the earth from damaging ultraviolet radiation (UVR), will result in elevated levels of UVR reaching the earth's surface, leading to a drastic increase in the incidence of skin cancer. In addition to promoting carcinogenesis in skin cells, UVR is a potent extrinsic driver of age-related changes in the skin known as "photoaging." We are in the preliminary stages of understanding of the role of intrinsic aging in melanoma, and the tumor-permissive effects of photoaging on the skin microenvironment remain largely unexplored. In this Review, we provide an overview of the impact of UVR on the skin microenvironment, addressing changes that converge or diverge with those observed in intrinsic aging. Intrinsic and extrinsic aging promote phenotypic changes to skin cell populations that alter fundamental processes such as melanogenesis, extracellular matrix deposition, inflammation, and immune response. Given the relevance of these processes in cancer, we discuss how photoaging might render the skin microenvironment permissive to melanoma progression.

Apatinib exhibits synergistic effect with pyrotinib and reverses acquired pyrotinib resistance in HER2-positive gastric cancer via stem cell factor/c-kit signaling and its downstream pathways

BACKGROUND

Recently, progress has been made in the development of targeted therapies for human epidermal growth factor receptor 2 (HER2)-positive gastric cancer (GC). However, drug resistance has severely limited the efficacy of anti-HER2 therapies. Pyrotinib is a novel pan-HER inhibitor. Although it is effective in HER2-positive GC treatment, its efficacy in combination with apatinib and associated resistance mechanisms in HER2-positive GC remains unclear.

METHODS

In this study, the combination effects of pyrotinib and apatinib were examined in two pyrotinib-sensitive GC cells and xenografts. The RNA sequencing was used to determine the underlying mechanisms of acquired pyrotinib resistance. The role of imatinib and apatinib in reversing pyrotinib resistance was tested in pyrotinib-resistant cells and xenografts.

RESULTS

Here, we reported that a combination of pyrotinib and apatinib exhibits synergistic effect in HER2-positive NCI-N87 xenografts, and showed enhanced antitumor efficacy in HER2-positive GC, both in vitro and in vivo. Moreover, up-regulation of the stem cell factor (SCF) levels, and the PI3K/AKT and MAPK pathways was associated with acquired pyrotinib resistance in HER2-positive GC. Mechanistically, we demonstrated that the activation of the SCF/c-kit signaling and its downstream PI3K/AKT and MAPK pathways mediated pyrotinib resistance by promoting cell survival and proliferation. Imatinib and apatinib augmented the sensitivity of pyrotinib-resistant cells and xenografts to pyrotinib, by blocking SCF/c-kit signaling.

CONCLUSION

These results highlight the effectiveness of pyrotinib combined with apatinib in HER2-positive GC and acquired pyrotinib resistance, thus providing a theoretical basis for new treatment methods.

Persistent Human KIT Receptor Signaling Disposes Murine Placenta to Premature Differentiation Resulting in Severely Disrupted Placental Structure and Functionality

Activating mutations in the human KIT receptor is known to drive severe hematopoietic disorders and tumor formation spanning various entities. The most common mutation is the substitution of aspartic acid at position 816 to valine (D816V), rendering the receptor constitutively active independent of ligand binding. As the role of the KIT receptor in placental signaling cascades is poorly understood, we analyzed the impact of KIT^D816V expression on placental development using a humanized mouse model. Placentas from KIT^D816V animals present with a grossly changed morphology, displaying a reduction in labyrinth and spongiotrophoblast layer and an increase in the Parietal Trophoblast Giant Cell (P-TGC) layer. Elevated differentiation to P-TGCs was accompanied with reduced differentiation to other Trophoblast Giant Cell (TGC) subtypes and by severe decrease in proliferation. The embryos display growth retardation and die in utero. KIT^D816V-trophoblast stem cells (TSC) differentiate much faster compared to wild type (WT) controls. In undifferentiated KIT^D816V-TSCs, levels of Phosphorylated Extracellular-signal Regulated Kinase (P-ERK) and Phosphorylated Protein Kinase B (P-AKT) are comparable to wildtype cultures differentiating for 3–6 days. Accordingly, P-TGC markers Placental Lactogen 1 (PL1) and Proliferin (PLF) are upregulated as well. The results reveal that KIT signaling orchestrates the fine-tuned differentiation of the placenta, with special emphasis on P-TGC differentiation. Appropriate control of KIT receptor action is therefore essential for placental development and nourishment of the embryo.

Understanding The Role of Reline, a Natural DES, on Temperature-Induced Conformational Changes of C-Kit G-Quadruplex DNA: A Molecular Dynamics Study

The noncanonical guanine-rich DNAs have drawn particular attention to the scientific world due to their controllable diverse and polymorphic structures. Apart from biological and medical significance, G-quadruplex DNAs are widely used in various fields such as nanotechnology, nanomachine, biosensors, and biocatalyst. So far, the applications of the G-quadruplex DNA are mainly limited in the water medium. Recently, a new generation of solvent named deep eutectic solvent (DES) has become very popular and has been widely used as a reaction medium of biocatalytic reactions and long-term storage medium for nucleic acids, even at high temperature. Hence, it is essential to understand the role of DES on temperature-induced conformational changes of a G-quadruplex DNA. In this research work, we have explored the temperature-mediated conformational dynamics of c-kit oncogene promoter G-quadruplex DNA in reline medium in the temperature range of 300-500 K, using a total of 10 μs unbiased all-atom molecular dynamics simulation. Here, from RMSD, RMSF, R_g and principal component analyses, we notice that the c-kit G-quadruplex DNA is stable up to 450 K in reline medium. However, it unfolds in water medium at 450 K. It is found that the hydrogen bonding interactions between c-kit G-quadruplex DNA and reline play a key role in the stabilization of the G-quadruplex DNA even at high temperature. Furthermore, in this work we have observed a very interesting and distinctive phenomenon of the central cation of the G-quadruplex DNA. Its position was seen to fluctuate between the two tetrad cores, that is, the region between tetrad-1 and tetrad-2 and that between tetrad-2 and tetrad-3 and vice versa at 450 and 500 K in reline medium which is absent in water medium at 450 K. Moreover, the rate of its oscillation is increased when temperature is increased.

Selection signatures in goats reveal copy number variants underlying breed-defining coat color phenotypes

Domestication and human selection have formed diverse goat breeds with characteristic phenotypes. This process correlated with the fixation of causative genetic variants controlling breed-specific traits within regions of reduced genetic diversity, so called selection signatures or selective sweeps. Using whole genome sequencing of DNA pools (pool-seq) from 20 genetically diverse modern goat breeds and bezoars, we identified 2,239 putative selection signatures. In two Pakistani goat breeds, Pak Angora and Barbari, we found selection signatures in a region harboring KIT, a gene involved in melanoblast development, migration, and survival. The search for candidate causative variants responsible for these selective sweeps revealed two different copy number variants (CNVs) downstream of KIT that were exclusively present in white Pak Angora and white-spotted Barbari goats. Several Swiss goat breeds selected for specific coat colors showed selection signatures at the ASIP locus encoding the agouti signaling protein. Analysis of these selective sweeps revealed four different CNVs associated with the white or tan (A^Wt), Swiss markings (A^sm), badgerface (A^b), and the newly proposed peacock (A^pc) allele. RNA-seq analyses on skin samples from goats with the different CNV alleles suggest that the identified structural variants lead to an altered expression of ASIP between eumelanistic and pheomelanistic body areas. Our study yields novel insights into the genetic control of pigmentation by identifying six functionally relevant CNVs. It illustrates how structural changes of the genome have contributed to phenotypic evolution in domestic goats.

Domestic animals have been selected for hundreds or sometimes even thousands of years for traits that were appreciated by their human owners. This process correlated with the fixation of causative genetic variants controlling breed-specific traits within regions of reduced genetic diversity, so called selection signatures or selective sweeps. We conducted a comprehensive screen for selection signatures in 20 phenotypically and genetically diverse modern goat breeds and identified a total of 2,239 putative selection signatures in our dataset. Follow-up experiments on selection signatures harboring known candidate genes for coat color revealed six different copy number variants (CNVs). Two of these CNVs were located in the 3’-flanking region of KIT and associated with a completely white coat color phenotype in Pak Angora goats and a white-spotted coat color phenotype in Barbari goats, respectively. The other four CNVs were located at the ASIP locus. They were associated with four different types of coat color patterning in seven Swiss goat breeds. Their functional effect is mediated by region-specific quantitative changes in ASIP mRNA expression. Our study illustrates how structural changes of the genome have contributed to phenotypic evolution in domestic goats.

The Role of Stem Cell Factor in Hyperpigmented Skin Lesions

BACKGROUND

Skin hyperpigmentation usually results from an increased number, or activity, of melanocytes. The degree of pigmentation of skin depends on the amount and type of melanin, degree of skin vascularity, presence of carotene, and thickness of the stratum corneum. Common causes of hyperpigmentation include post-inflammatory hyperpigmentation, melasma, solar lentigines, ephelides (freckles), and café-au-lait macules. Some skin tumors can be hyperpigmented as basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and malignant melanoma (MM). Stem cell factor (SCF) is a growth factor and its interaction with its receptor, c-kit, is well known to be critical to the survival of melanocytes.

METHODS

This study was carried out on 60 patients complaining of hyperpigmented skin lesions (20 melasma, 20 solar lentigines, and 20 freckles) and 36 patients with skin tumors (14 BCC, 12 SCC, and 10 MM). Punch skin biopsies were taken from the previous lesions. Immunohistochemical staining of these samples was done using the stem cell factor (SCF).

RESULTS

There was positive expression of SCF in all cases of melasma, solar lentigines and freckles with significant increase in the intensity of expression in the lesional areas than the non-lesional ones (P=0.004). There was also a statistically significant increase in the expression of SCF in BCC and melanoma tumor cells.

CONCLUSION

SCF has a great role in skin hyperpigmented disorders and this can be used as a target for the developing of new antipigmentary lines of treatment by inhibiting SCF. SCF can also be involved in the emergence of some skin tumors.

Phosphoproteomic Landscaping Identifies Non-canonical cKIT Signaling in Polycythemia Vera Erythroid Progenitors

Although stem cell factor (SCF)/cKIT interaction plays key functions in erythropoiesis, cKIT signaling in human erythroid cells is still poorly defined. To provide new insights into cKIT-mediated erythroid expansion in development and disease, we performed phosphoproteomic profiling of primary erythroid progenitors from adult blood (AB), cord blood (CB), and Polycythemia Vera (PV) at steady-state and upon SCF stimulation. While AB and CB, respectively, activated transient or sustained canonical cKIT-signaling, PV showed a non-canonical signaling including increased mTOR and ERK1 and decreased DEPTOR. Accordingly, screening of FDA-approved compounds showed increased PV sensitivity to JAK, cKIT, and MEK inhibitors. Moreover, differently from AB and CB, in PV the mature 145kDa-cKIT constitutively associated with the tetraspanin CD63 and was not endocytosed upon SCF stimulation, contributing to unrestrained cKIT signaling. These results identify a clinically exploitable variegation of cKIT signaling/metabolism that may contribute to the great erythroid output occurring during development and in PV.

Serum level of stem cell factor and its soluble receptor in aspirin-exacerbated respiratory disease

Aim: Stem cell factor (SCF) may be associated with inflammatory processes leading to aspirin-induced asthma. This study evaluated the relationship between serum level of SCF and its soluble receptor with aspirin-induced asthma. Methods & materials: Twenty-five patients and 25 healthy controls were enrolled in this study. The concentration of SCF and mast/stem cell growth factor receptor (C-kit) was determined in serum samples. Spirometry and rhinometry were performed to determine the severity of the disease. p < 0.05 were considered significant. Results: The serum levels of SCF and C-kit receptor were significantly higher in the case group. The serum SCF and C-kit level had a significant positive correlation with the severity of asthma, disease duration and nasal obstruction. Conclusion: Our findings suggest that SCF and C-kit receptors have a direct effect on the severity of aspirin-induced asthma.

Dual Mechanisms of LYN Kinase Dysregulation Drive Aggressive Behavior in Breast Cancer Cells

The SRC-family kinase LYN is highly expressed in triple-negative/basal-like breast cancer (TNBC) and in the cell of origin of these tumors, c-KIT-positive luminal progenitors. Here, we demonstrate LYN is a downstream effector of c-KIT in normal mammary cells and protective of apoptosis upon genotoxic stress. LYN activity is modulated by PIN1, a prolyl isomerase, and in BRCA1 mutant TNBC PIN1 upregulation activates LYN independently of c-KIT. Furthermore, the full-length LYN splice isoform (as opposed to the Δaa25-45 variant) drives migration and invasion of aggressive TNBC cells, while the ratio of splice variants is informative for breast cancer-specific survival across all breast cancers. Thus, dual mechanisms-uncoupling from upstream signals and splice isoform ratios-drive the activity of LYN in aggressive breast cancers.

Stem cell factor and NSC87877 combine to enhance c-Kit mediated proliferation of human megakaryoblastic cells

Enhancement of hematopoietic stem cells (HSCs) proliferation is a central aim in bone marrow transplantation (BMT). A stem cell factor (SCF) and c-Kit mediated extracellular signaling trigger proliferation of HSCs. This signaling is negatively regulated by protein tyrosine phosphatases (PTPs), SHP-1 and SHP-2. Although NSC87877 (N) is known to inhibit SHP-1/SHP-2, c-Kit-mediated HSCs proliferation by inhibiting SHP-1/SHP-2 has not been reported. This study investigated the combined effect of SCF (S) and N in c-Kit mediated proliferation and underlying mechanisms. The growth of human megakaryoblastic cell line, MO7e and HSCs, upon treatment with S and N alone, and in combination was assessed by PrestoBlue staining. The expression of c-Kit, phosphorylated c-Kit, SHP-1/SHP-2 and HePTP inhibition using S and N treatment were evaluated in the MO7e cells. Megakaryoblast cell proliferation was determined by quantification of Ki-67+, S-phase, BrdU+ and CFDA-SE+ cells using flow cytometry. The combination of S and N leads to enhanced cell growth compared with either S or N alone. Collectively, the results reveal a novel mechanism by which S in combination with N significantly enhances proliferation of human megakaryoblast cells. The pretreatment of N before S enhances proliferation of cells than S alone. This promising combination would likely play an essential role in enhancing the proliferation of cells.

Kit ligand has a critical role in mouse yolk sac and aorta-gonad-mesonephros hematopoiesis

Few studies report on the in vivo requirement for hematopoietic niche factors in the mammalian embryo. Here, we comprehensively analyze the requirement for Kit ligand (Kitl) in the yolk sac and aorta-gonad-mesonephros (AGM) niche. In-depth analysis of loss-of-function and transgenic reporter mouse models show that Kitl-deficient embryos harbor decreased numbers of yolk sac erythro-myeloid progenitor (EMP) cells, resulting from a proliferation defect following their initial emergence. This EMP defect causes a dramatic decrease in fetal liver erythroid cells prior to the onset of hematopoietic stem cell (HSC)-derived erythropoiesis, and a reduction in tissue-resident macrophages. Pre-HSCs in the AGM require Kitl for survival and maturation, but not proliferation. Although Kitl is expressed widely in all embryonic hematopoietic niches, conditional deletion in endothelial cells recapitulates germline loss-of-function phenotypes in AGM and yolk sac, with phenotypic HSCs but not EMPs remaining dependent on endothelial Kitl upon migration to the fetal liver. In conclusion, our data establish Kitl as a critical regulator in the in vivoAGM and yolk sac endothelial niche.

Expression profiling of c-kit and its impact after esiRNA silencing during gonadal development in catfish

Receptor, c-Kit is a member of a family of growth factor receptors that have tyrosine kinase activity, and are involved in the transduction of growth regulatory signals across plasma membrane by activation of its ligand, kitl/scf. The present study analyzed mRNA and protein expression profiles of c-kit in the gonads of catfish, Clarias gariepinus, using real time PCR, in situ hybridization and immunohistochemistry. Tissue distribution analysis revealed higher expression mainly in the catfish gonads. Ontogeny studies showed minimal expression during early developmental stages and highest during 50-75 days post hatch, and the dimorphic expression in gonads decreased gradually till adulthood, which might suggest an important role for this gene around later stages of sex differentiation and gonadal development. Expression of c-kit was analyzed at various phases of gonadal cycle in both male and female, which showed minimal expression during the resting phase, and higher expression during the pre-spawning phase in male compared to females. In vitro and in vivo induction using human chorionic gonadotropin elevated the expression of c-kit indicating the regulatory influence of hypothalamo-hypophyseal axis. In vivo transient gene silencing using c-kit-esiRNA in adult catfish during gonadal recrudescence showed a decrease in c-kit expression, which affected the expression levels of germ cell meiotic marker sycp3, as well as several factors and steroidogenic enzyme genes that are involved in germ cell development. Decrease in the levels of 11-ketotestosterone and testosterone in serum were also observed after esiRNA silencing. The findings suggests that c-kit has an important role in the process of germ cell proliferation, development and maturation during gonadal development and recrudescence in catfish.

Bioengineering functional smooth muscle with spontaneous rhythmic contraction in vitro

Oriented smooth muscle layers in the intestine contract rhythmically due to the action of interstitial cells of Cajal (ICC) that serve as pacemakers of the intestine. Disruption of ICC networks has been reported in various intestinal motility disorders, which limit the quality and expectancy of life. A significant challenge in intestinal smooth muscle engineering is the rapid loss of function in cultured ICC and smooth muscle cells (SMC). Here we demonstrate a novel approach to maintain the function of both ICC and SMC in vitro. Primary intestinal SMC mixtures cultured on feeder cells seeded electrospun poly(3-caprolactone) scaffolds exhibited rhythmic contractions with directionality for over 10 weeks in vitro. The simplicity of this system should allow for wide usage in research on intestinal motility disorders and tissue engineering, and may prove to be a versatile platform for generating other types of functional SMC in vitro.

Epithelial-mesenchymal transition (EMT) beyond EGFR mutations per se is a common mechanism for acquired resistance to EGFR TKI

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) is a major advance in treating NSCLC with EGFR-activating mutations. However, acquired resistance, due partially to secondary mutations limits their use. Here we report that NSCLC cells with acquired resistance to gefitinib or osimertinib (AZD9291) exhibit EMT features, with a decrease in E-cadherin, and increases in vimentin and stemness, without possessing any EGFR secondary mutations. Knockdown of E-cadherin in parental cells increased gefitinib resistance and stemness, while knockdown of vimentin in resistant cells resulted in opposite effects. Src activation and Hakai upregulation were found in gefitinib-resistant cells. Knockdown of Hakai elevated E-cadherin expression, attenuated stemness, and resensitized the cells to gefitinib. Clinical cancer specimens with acquired gefitinib resistance also showed a decrease in E-cadherin and an increase in Hakai expression. The dual HDAC and HMGR inhibitor JMF3086 inhibited the Src/Hakai and Hakai/E-cadherin interaction to reverse E-cadherin expression, and attenuated vimentin and stemness to restore gefitinib sensitivity. The EMT features of AZD9291-resistant H1975 cells were related to the upregulation of Zeb1. Both gefitinib and AZD9291 sensitivity was restored by JMF3086 through reversing EMT. Our study not only revealed a common mechanism of EMT in both gefitinib and AZD9291 resistance beyond EGFR mutations per se, but also provides a new strategy to overcome it.

Optimization of Isothiazolo[4,3- b]pyridine-Based Inhibitors of Cyclin G Associated Kinase (GAK) with Broad-Spectrum Antiviral Activity

There is an urgent need for strategies to combat dengue and other emerging viral infections. We reported that cyclin G-associated kinase (GAK), a cellular regulator of the clathrin-associated host adaptor proteins AP-1 and AP-2, regulates intracellular trafficking of multiple unrelated RNA viruses during early and late stages of the viral lifecycle. We also reported the discovery of potent, selective GAK inhibitors based on an isothiazolo[4,3- b]pyridine scaffold, albeit with moderate antiviral activity. Here, we describe our efforts leading to the discovery of novel isothiazolo[4,3- b]pyridines that maintain high GAK affinity and selectivity. These compounds demonstrate improved in vitro activity against dengue virus, including in human primary dendritic cells, and efficacy against the unrelated Ebola and chikungunya viruses. Moreover, inhibition of GAK activity was validated as an important mechanism of antiviral action of these compounds. These findings demonstrate the potential utility of a GAK-targeted broad-spectrum approach for combating currently untreatable emerging viral infections.

Cellular and viral oncogenes: the key to unlocking unknowns of Kaposi's sarcoma-associated herpesvirus pathogenesis

Oncogenic viruses carry an extensive arsenal of oncogenes for hijacking cellular pathways. Notably, variations in oncogenes among tumor-producing viruses give rise to different mechanisms for cellular transformation. Specifically, Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic virus able to infect and transform a variety of cell types. The oncogenicity of KSHV disseminates from the virus' ability to induce and encode a wide variety of both cellular and viral oncogenes. Such an array of cellular and viral oncogenes enables KSHV to induce the malignant phenotype of a KSHV-associated cancer. Evolutionarily, KSHV has acquired many oncogenic homologues capable of inducing cell proliferation, cell differentiation, cell survival, and immune evasion. Integration between inducing and encoding oncogenes plays a vital role in KSHV pathogenicity. KSHV is alleged to harbor the highest number of potential oncogenes by which a virus promotes cellular transformation and malignancy. Many KSHV inducing/encoding oncogenes are mainly expressed during the latent phase of KSHV infection, a period required for virus establishment of malignant cellular transformation. Elucidation of the exact mechanism(s) by which oncogenes promote KSHV pathogenicity would not only give rise to potential novel therapeutic targets/drugs but would also add to our understanding of cancer biology. The scope of this review is to examine the roles of the most important cellular and viral oncogenes involved in KSHV pathogenicity.

Advances in diagnosis of mastocytosis and hypereosinophilic syndrome☆

Mastocytosis and hypereosinophilic syndrome is very rare neoplastic hematopoietic diseases. Mastocytosis is characterized by expansion and accumulation of clonal tissue mast cells in skin and/or various internal organs, while hypereosinophilic syndrome manifests with an increased number of eosinophils in the peripheral blood and tissue damage. These diseases represent a diagnostic challenge, since they can have overlapping clinical and pathologic features. Recently, great advances in the molecular and immunophenotypic diagnosis of these two entities were achieved, contributing to the new World Health Organization (WHO) classification. The WHO classification of myeloid neoplasms has been revised in 2016 by adding several new entities and refinement of the 2008 WHO classification, in an attempt to incorporate up-to-date clinical, prognostic, morphologic, and molecular genetics data that emerged since 2008. Here we overview the recent advances in disease diagnosis, with a focus on the updated WHO classification, refined diagnostic criteria, and up-to-date molecular findings in these two rare diseases.

Src Family Kinases Regulate Interferon Regulatory Factor 1 K63 Ubiquitination following Activation by TLR7/8 Vaccine Adjuvant in Human Monocytes and B Cells

Toll-like receptors (TLRs) play a key role in the activation of innate immune cells, in which their engagement leads to production of cytokines and co-stimulatory molecules. TLRs signaling requires recruitment of toll/IL-1R (TIR) domain-containing adaptors, such as MyD88 and/or TRIF, and leads to activation of several transcription factors, such as NF-κB, the AP1 complex, and various members of the interferon regulatory factor (IRF) family, which in turn results in triggering of several cellular functions associated with these receptors. A role for Src family kinases (SFKs) in this signaling pathway has also been established. Our work and that of others have shown that this type of kinases is activated following engagement of several TLRs, and that this event is essential for the initiation of specific downstream cellular response. In particular, we have previously demonstrated that activation of SFKs is required for balanced production of pro-inflammatory cytokines by monocyte-derived dendritic cells after stimulation with R848, an agonist of human TLRs 7/8. We also showed that TLR7/8 triggering leads to an increase in interferon regulatory factor 1 (IRF-1) protein levels and that this effect is abolished by inhibition of SFKs, suggesting a critical role of these kinases in IRF-1 regulation. In this study, we first confirmed the key role of SFKs in TLR7/8 signaling for cytokine production and accumulation of IRF-1 protein in monocytes and in B lymphocytes, two other type of antigen-presenting cells. Then, we demonstrate that TLR7 triggering leads to an increase of K63-linked ubiquitination of IRF-1, which is prevented by SFKs inhibition, suggesting a key role of these kinases in posttranslational regulation of IRF-1 in the immune cells. In order to understand the mechanism that links SFKs activation to IRF-1 K63-linked ubiquitination, we examined SFKs and IRF-1 possible interactors and proved that activation of SFKs is necessary for their interaction with TNFR-associated factor 6 (TRAF6) and promotes the recruitment of both cIAP2 and IRF-1 by TRAF6. Collectively, our data demonstrate that TLR7/8 engagement leads to the formation of a complex that allows the interaction of cIAP2 and IRF-1 resulting in IRF-1 K63-linked ubiquitination, and that active SFKs are required for this process.

Dual protein kinase and nucleoside kinase modulators for rationally designed polypharmacology

Masitinib, a highly selective protein kinase inhibitor, can sensitise gemcitabine-refractory cancer cell lines when used in combination with gemcitabine. Here we report a reverse proteomic approach that identifies the target responsible for this sensitisation: the deoxycytidine kinase (dCK). Masitinib, as well as other protein kinase inhibitors, such as imatinib, interact with dCK and provoke an unforeseen conformational-dependent activation of this nucleoside kinase, modulating phosphorylation of nucleoside analogue drugs. This phenomenon leads to an increase of prodrug phosphorylation of most of the chemotherapeutic drugs activated by this nucleoside kinase. The unforeseen dual activity of protein kinase inhibition/nucleoside kinase activation could be of great therapeutic benefit, through either reducing toxicity of therapeutic agents by maintaining effectiveness at lower doses or by counteracting drug resistance initiated via down modulation of dCK target.

Masitinib is a protein kinase inhibitor that sensitises refractory pancreatic adenocarcinoma cells to treatment with the nucleoside analog gemcitabine. Here the authors show that Masitinib activates deoxycytidine kinase to enhance phosphorylation of nucleoside analogue pro-drugs, increasing their potency.

SCF-KIT signaling induces endothelin-3 synthesis and secretion: Thereby activates and regulates endothelin-B-receptor for generating temporally- and spatially-precise nitric oxide to modulate SCF- and or KIT-expressing cell functions

We demonstrate that SCF-KIT signaling induces synthesis and secretion of endothelin-3 (ET3) in human umbilical vein endothelial cells and melanoma cells in vitro, gastrointestinal stromal tumors, human sun-exposed skin, and myenteric plexus of human colon post-fasting in vivo. This is the first report of a physiological mechanism of ET3 induction. Integrating our finding with supporting data from literature leads us to discover a previously unreported pathway of nitric oxide (NO) generation derived from physiological endothelial NO synthase (eNOS) or neuronal NOS (nNOS) activation (referred to as the KIT-ET3-NO pathway). It involves: (1) SCF-expressing cells communicate with neighboring KIT-expressing cells directly or indirectly (cleaved soluble SCF). (2) SCF-KIT signaling induces timely local ET3 synthesis and secretion. (3) ET3 binds to ETBR on both sides of intercellular space. (4) ET3-binding-initiated-ETBR activation increases cytosolic Ca²⁺, activates cell-specific eNOS or nNOS. (5) Temporally- and spatially-precise NO generation. NO diffuses into neighboring cells, thus acts in both SCF- and KIT-expressing cells. (6) NO modulates diverse cell-specific functions by NO/cGMP pathway, controlling transcriptional factors, or other mechanisms. We demonstrate the critical physiological role of the KIT-ET3-NO pathway in fulfilling high demand (exceeding basal level) of endothelium-dependent NO generation for coping with atherosclerosis, pregnancy, and aging. The KIT-ET3-NO pathway most likely also play critical roles in other cell functions that involve dual requirement of SCF-KIT signaling and NO. New strategies (e.g. enhancing the KIT-ET3-NO pathway) to harness the benefit of endogenous eNOS and nNOS activation and precise NO generation for correcting pathophysiology and restoring functions warrant investigation.

Comparative Expression Analysis of HSP70, HSP90, IL-4, TNF, KITLG and KIT-receptor Gene between Varicocele-Induced and Non-Varicocele Testes of Dog

Background

This study was designed to create an experimental varicocele model by a simple surgical procedure in dog with minimum invasion and to investigate the effect of varicocele-induced infertility on the expression of six related genes (HSP90, HSP70, IL-4, TNF, KITLG and KIT receptor).

Materials and Methods

In this experimental study, the proximal part of the pampini-form plexus of dog testes was partially occluded without abdominal incision which was confirmed by venographic examination. To evaluate varicocele in its acute form, dogs were castrated after 15 days and testes were dissected. Histopathologic evaluation was undertaken and the relative expression of the six genes was assessed by quantitative realtime polymerase chain reaction (PCR).

Results

Microscopic changes showed tubule degeneration. The Johnson score was significantly decreased in the varicocele testes when compared with non-varicocele testes. Expressions of HSP90, TNF, KITLG and the KIT-receptor gene were significantly downregulated (P=0.029, 0.047, 0.004 and 0.035 respectively) in varicocele-induced testes while HSP70 was upregulated (P=0.018). IL-4 did not show differential expression (P=0.377).

Conclusion

We conclude that partial occlusion of the proximal part of the pampiniform plexus induces varicocele in the testis of dog. Differential expression of the mentioned genes may be responsible for the pathophysiology of varicocele and related subfertility.

Anticancer kinase inhibitors impair intracellular viral trafficking and exert broad-spectrum antiviral effects

Global health is threatened by emerging viral infections, which largely lack effective vaccines or therapies. Targeting host pathways that are exploited by multiple viruses could offer broad-spectrum solutions. We previously reported that AAK1 and GAK, kinase regulators of the host adaptor proteins AP1 and AP2, are essential for hepatitis C virus (HCV) infection, but the underlying mechanism and relevance to other viruses or in vivo infections remained unknown. Here, we have discovered that AP1 and AP2 cotraffic with HCV particles in live cells. Moreover, we found that multiple viruses, including dengue and Ebola, exploit AAK1 and GAK during entry and infectious virus production. In cultured cells, treatment with sunitinib and erlotinib, approved anticancer drugs that inhibit AAK1 or GAK activity, or with more selective compounds inhibited intracellular trafficking of HCV and multiple unrelated RNA viruses with a high barrier to resistance. In murine models of dengue and Ebola infection, sunitinib/erlotinib combination protected against morbidity and mortality. We validated sunitinib- and erlotinib-mediated inhibition of AAK1 and GAK activity as an important mechanism of antiviral action. Additionally, we revealed potential roles for additional kinase targets. These findings advance our understanding of virus-host interactions and establish a proof of principle for a repurposed, host-targeted approach to combat emerging viruses.

GM-CSF Inhibits c-Kit and SCF Expression by Bone Marrow-Derived Dendritic Cells

Stem cell factor (SCF), the ligand of c-kit, is a key cytokine for hematopoiesis. Hematopoietic precursors express c-kit, whereas differentiated cells of hematopoietic lineage are negative for this receptor, with the exception of NK cells, mast cells, and a few others. While it has long been recognized that dendritic cells (DCs) can express c-kit, several questions remain concerning the SCF/c-kit axis in DCs. This is particularly relevant for DCs found in those organs wherein SCF is highly expressed, including the bone marrow (BM). We characterized c-kit expression by conventional DCs (cDCs) from BM and demonstrated a higher proportion of c-kit⁺ cells among type 1 cDC subsets (cDC1s) than type 2 cDC subsets (cDC2s) in both humans and mice, whereas similar levels of c-kit expression were observed in cDC1s and cDC2s from mouse spleen. To further study c-kit regulation, DCs were generated with granulocyte-macrophage colony-stimulating factor (GM-CSF) from mouse BM, a widely used protocol. CD11c⁺ cells were purified from pooled non-adherent and slightly adherent cells collected after 7 days of culture, thus obtaining highly purified BM-derived DCs (BMdDCs). BMdDCs contained a small fraction of c-kit⁺ cells, and by replating them for 2 days with GM-CSF, we obtained a homogeneous population of c-kit⁺ CD40^hi MHCII^hi cells. Not only did BMdDCs express c-kit but they also produced SCF, and both were striking upregulated if GM-CSF was omitted after replating. Furthermore, a small but significant reduction in BMdDC survival was observed upon SCF silencing. Incubation of BMdDCs with SCF did not modulate antigen presentation ability of these cells, nor it did regulate their membrane expression of the chemokine receptor CXCR4. We conclude that the SCF/c-kit-mediated prosurvival circuit may have been overlooked because of the prominent use of GM-CSF in DC cultures in vitro, including those human DC cultures destined for the clinics. We speculate that DCs more prominently rely on SCF in vivo in some microenvironments, with potential implications for graft-versus-host disease and antitumor immunity.

Subfertility and Risk of Testicular Cancer in the EPSAM Case-Control Study

Background/objectives

It has been suggested that subfertility and testicular cancer share genetic and environmental risk factors. We studied both subfertility and the strongest known testicular cancer susceptibility gene, the c-KIT ligand (KITLG), whose pathway is involved in spermatogenesis.

Methods

The EPSAM case-control study is comprised of testicular cancer patients from the Province of Turin, Italy, diagnosed between 1997 and 2008. The present analysis included 245 cases and 436 controls from EPSAM, who were aged 20 years or older at diagnosis/recruitment. The EPSAM questionnaire collected information on factors such as number of children, age at first attempt to conceive, duration of attempt to conceive, use of assisted reproduction techniques, physician-assigned diagnosis of infertility, number of siblings, and self-reported cryptorchidism. Genotyping of the KITLG single nucleotide polymorphism (SNP) rs995030 was performed on the saliva samples of 202 cases and 329 controls.

Results

Testicular cancer was associated with the number of children fathered 5 years before diagnosis (odds ratio (OR) per additional child: 0.78, 95% confidence interval (CI): 0.58–1.04) and sibship size (OR per additional sibling: 0.76, 95% CI: 0.66–0.88). When considering the reproductive history until 1 year before diagnosis, attempting to conceive for at least 12 months or fathering a child using assisted reproduction techniques was not associated with the risk of testicular cancer, nor was age at first attempt to conceive or physician-assigned diagnosis of infertility. The SNP rs995030 was strongly associated with risk of testicular cancer (per allele OR: 1.83; 95%CI: 1.26–2.64), but it did not modify the association between number of children and the risk of testicular cancer.

Conclusion

This study supports the repeatedly reported inverse association between number of children and risk of testicular cancer, but it does not find evidence of an association for other indicators of subfertility.

The Evolution of Oncology Companion Diagnostics from Signal Transduction to Immuno-Oncology

Sixteen oncology drugs have been approved with a companion diagnostic (CDx) test by the FDA. These represent only 9.6% of the 167 oncology drug approvals since 1998, the year the first CDx test for Herceptin was approved. The great majority of CDx tests are for drugs that inhibit signal transduction pathways by either inhibiting the intracellular kinase activity with a small molecule or preventing ligand-induced receptor activation with a monoclonal antibody. In most of these cases, prospective patient selection for the biomarker-positive subpopulation was initiated in or before Phase II. The development of CDx tests for emerging immunotherapies will be more complicated because they are not dependent on driver mutations in the drug target, the mechanism of action is often pleiotropic, and will require both protein and cell-based assays to evaluate the interaction of the tumor with the immune system. Consequently, we will need to develop new biomarker strategies for the development of immunotherapies and to determine whether the optimum strategy is to release a prior checkpoint blockade in patients with a suppressed immune response, or to prime a new immune response to the tumor.

Expression of Epidermal c-Kit+ of Vitiligo Lesions Is Related to Responses to Excimer Laser

Background

The survival and growth of melanocytes are controlled by the binding of stem cell factor to its cell surface receptor c-kit+ (CD117). We have observed that c-kit+ melanocytes existed in some lesions of vitiligo, while Melan A+ cells were absent.

Objective

To verify possible relation between c-kit+ expression and treatment response in non-segmental vitiligo lesions

Methods

Skin biopsies were done from the center of the 47 lesions from the 47 patients with non-segmental vitiligo. Expression of c-kit+ and Melan A, and amounts of melanin in the epidermis were assessed in each lesion, and treatment responses to excimer laser were evaluated.

Results

Thirty-five of the 47 lesions (74.5%) had c-kit+ phenotypes. There was significant difference of c-kit staining value between good responders in 3 months of excimer laser treatment (average of 24 sessions) and the others.

Conclusion

c-Kit expression in vitiliginous epidermis may be related to better treatment responses to excimer laser.

The genomic landscape of testicular germ cell tumours: from susceptibility to treatment

The genomic landscape of testicular germ cell tumour (TGCT) can be summarized using four overarching hypotheses. Firstly, TGCT risk is dominated by inherited genetic factors, which determine nearly half of all disease risk and are highly polygenic in nature. Secondly KIT-KITLG signalling is currently the major pathway that is implicated in TGCT formation, both as a predisposition risk factor and a somatic driver event. Results from genome-wide association studies have also consistently suggested that other closely related pathways involved in male germ cell development and sex determination are associated with TGCT risk. Thirdly, the method of disease formation is unique, with tumours universally stemming from a noninvasive precursor lesion, probably of fetal origin, which lies dormant through childhood into adolescence and then eventually begins malignant growth in early adulthood. Formation of a 12p isochromosome, a hallmark of TGCT observed in nearly all tumours, is likely to be a key triggering event for malignant transformation. Finally, TGCT have been shown to have a distinctive somatic mutational profile, with a low rate of point mutations contrasted with frequent large-scale chromosomal gains. These four hypotheses by no means constitute a complete model that explains TGCT tumorigenesis, but advances in genomic technologies have enabled considerable progress in describing and understanding the disease. Further advancing our understanding of the genomic basis of TGCT offers a clear opportunity for clinical benefit in terms of preventing invasive cancer arising in young men, decreasing the burden of chemotherapy-related survivorship issues and reducing mortality in the minority of patients who have treatment-refractory disease.

MicroRNAs and Gastrointestinal Stromal Tumor

Gastrointestinal stromal tumor (GIST) is the most commonly diagnosed mesenchymal tumor in the gastrointestinal tract. This tumor type is driven by gain-of-function mutations in receptor tyrosine kinases (such as KIT, PDGFRA, and BRAF) or loss-of-function mutations in succinate dehydrogenase complex subunit genes (SDHx). Molecular studies on GIST have improved our understanding of the biology of the disease and have led to the use of targeted therapy approach, such as imatinib for KIT/PDGFRA-mutated GIST. Recently, microRNAs have emerged as important regulators of KIT expression, cancer cell behavior, and imatinib response in GIST. This chapter aims to provide an overview on current understanding of the biological roles of microRNAs in GIST and possible implications in prognosis and therapeutic response.