Functional Investigation of IGF1R Mutations in Multiple Myeloma.

High expression of the receptor tyrosine kinase (RTK) insulin-like growth factor-1 receptor (IGF1R) and RTK mutations are associated with high-risk/worse prognosis in multiple myeloma (MM). Combining the pIGF1R/pINSR inhibitor linsitinib with the proteasome inhibitor (PI) bortezomib seemed promising in a clinical trial, but IGF1R expression was not associated with therapy response. Because the oncogenic impact of IGF1R mutations is so far unknown, we investigated the functional impact of IGF1R mutations on survival signaling, viability/proliferation and survival response to therapy. We transfected four human myeloma cell lines (HMCLs) with IGF1RWT, IGF1RD1146N and IGF1RN1129S (Sleeping Beauty), generated CRISPR-Cas9 IGF1R knockouts in the HMCLs U-266 (IGF1RWT) and L-363 (IGF1RD1146N) and tested the anti-MM activity of linsitinib alone and in combination with the second-generation PI carfilzomib in seven HMCLs. IGF1R knockout entailed reduced proliferation. Upon IGF1R overexpression, survival signaling was moderately increased in all HCMLs and slightly affected by IGF1RN1129S in one HMCL, whereby the viability remained unaffected. Expression of IGF1RD1146N reduced pIGF1R-Y1135, especially under serum reduction, but did not impact downstream signaling. Linsitinib and carfilzomib showed enhanced anti-myeloma activity in six out of seven HMCL irrespective of the IGF1R mutation status. In conclusion, IGF1R mutations can impact IGF1R activation and/or downstream signaling, and a combination of linsitinib with carfilzomib might be a suitable therapeutic approach for MM patients potentially responsive to IGF1R blockade.

Caveolin-2 palmitoylation turnover facilitates insulin receptor substrate-1-directed lipid metabolism by insulin receptor tyrosine kinase.

Here, we show that insulin induces palmitoylation turnover of Caveolin-2 (Cav-2) in adipocytes. Acyl protein thioesterases-1 (APT1) catalyzes Cav-2 depalmitoylation, and zinc finger DHHC domain-containing protein palmitoyltransferase 21 (ZDHHC21) repalmitoylation of the depalmitoylated Cav-2 for the turnover, thereby controlling insulin receptor (IR)-Cav-2-insulin receptor substrate-1 (IRS-1)-Akt-driven signaling. Insulin-induced palmitoylation turnover of Cav-2 facilitated glucose uptake and fat storage through induction of lipogenic genes. Cav-2-, APT1-, and ZDHHC21-deficient adipocytes, however, showed increased induction of lipolytic genes and glycerol release. In addition, white adipose tissues from insulin sensitive and resistant obese patients exhibited augmented expression of LYPLA1 (APT1) and ZDHHC20 (ZDHHC20). Our study identifies the specific enzymes regulating Cav-2 palmitoylation turnover, and reveals a new mechanism by which insulin-mediated lipid metabolism is controlled in adipocytes.

Multiplex single-cell chemical genomics reveals the kinase dependence of the response to targeted therapy.

Chemical genetic screens are a powerful tool for exploring how cancer cells' response to drugs is shaped by their mutations, yet they lack a molecular view of the contribution of individual genes to the response to exposure. Here, we present sci-Plex-Gene-by-Environment (sci-Plex-GxE), a platform for combined single-cell genetic and chemical screening at scale. We highlight the advantages of large-scale, unbiased screening by defining the contribution of each of 522 human kinases to the response of glioblastoma to different drugs designed to abrogate signaling from the receptor tyrosine kinase pathway. In total, we probed 14,121 gene-by-environment combinations across 1,052,205 single-cell transcriptomes. We identify an expression signature characteristic of compensatory adaptive signaling regulated in a MEK/MAPK-dependent manner. Further analyses aimed at preventing adaptation revealed promising combination therapies, including dual MEK and CDC7/CDK9 or nuclear factor κB (NF-κB) inhibitors, as potent means of preventing transcriptional adaptation of glioblastoma to targeted therapy.

Signaling Pathways Controlling Axonal Wrapping in Drosophila.

The rapid transmission of action potentials is an important ability that enables efficient communication within the nervous system. Glial cells influence conduction velocity along axons by regulating the radial axonal diameter, providing electrical insulation as well as affecting the distribution of voltage-gated ion channels. Differentiation of these wrapping glial cells requires a complex set of neuron-glia interactions involving three basic mechanistic features. The glia must recognize the axon, grow around it, and eventually arrest its growth to form single or multiple axon wraps. This likely depends on the integration of numerous evolutionary conserved signaling and adhesion systems. Here, we summarize the mechanisms and underlying signaling pathways that control glial wrapping in Drosophila and compare those to the mechanisms that control glial differentiation in mammals. This analysis shows that Drosophila is a beneficial model to study the development of even complex structures like myelin.

Omics profiling identifies the regulatory functions of the MAPK/ERK pathway in nephron progenitor metabolism.

Nephron endowment is defined by fetal kidney growth and crucially dictates renal health in adults. Defects in the molecular regulation of nephron progenitors contribute to only a fraction of reduced nephron mass cases, suggesting alternative causative mechanisms. The importance of MAPK/ERK activation in nephron progenitor maintenance has been previously demonstrated, and here, we characterized the metabolic consequences of MAPK/ERK deficiency. Liquid chromatography/mass spectrometry-based metabolomics profiling identified 42 reduced metabolites, of which 26 were supported by in vivo transcriptional changes in MAPK/ERK-deficient nephron progenitors. Among these, mitochondria, ribosome and amino acid metabolism, together with diminished pyruvate and proline metabolism, were the most affected pathways. In vitro cultures of mouse kidneys demonstrated a dosage-specific function for pyruvate in controlling the shape of the ureteric bud tip, a regulatory niche for nephron progenitors. In vivo disruption of proline metabolism caused premature nephron progenitor exhaustion through their accelerated differentiation in pyrroline-5-carboxylate reductases 1 (Pycr1) and 2 (Pycr2) double-knockout kidneys. Pycr1/Pycr2-deficient progenitors showed normal cell survival, indicating no changes in cellular stress. Our results suggest that MAPK/ERK-dependent metabolism functionally participates in nephron progenitor maintenance by monitoring pyruvate and proline biogenesis in developing kidneys.

Different HSP90 Inhibitors Exert Divergent Effect on Myxoid Liposarcoma In Vitro and In Vivo.

The therapeutic options for patients with relapsed or metastatic myxoid liposarcoma (MLS) remain scarce and there is currently no targeted therapy available. Inhibition of the HSP90 family of chaperones has been suggested as a possible therapeutic option for patients with MLS. However, the clinical effect of different HSP90 inhibitors vary considerably and no comparative study in MLS has been performed. Here, we evaluated the effects of the HSP90 inhibitors 17-DMAG, AUY922 and STA-9090 on MLS cell lines and in an MLS patient-derived xenograft (PDX) model. Albeit all drugs inhibited in vitro growth of MLS cell lines, the in vivo responses were discrepant. Whereas 17-DMAG inhibited tumor growth, AUY922 surprisingly led to increased tumor growth and a more aggressive morphological phenotype. In vitro, 17-DMAG and STA-9090 reduced the activity of the MAPK and PI3K/AKT signaling pathways, whereas AUY922 led to a compensatory upregulation of downstream ERK. Furthermore, all three tested HSP90 inhibitors displayed a synergistic combination effect with trabectidin, but not with doxorubicin. In conclusion, our results indicate that different HSP90 inhibitors, albeit having the same target, can vary significantly in downstream effects and treatment outcomes. These results should be considered before proceeding into clinical trials against MLS or other malignancies.

Identification of copy number variation-driven molecular subtypes informative for prognosis and treatment in pancreatic adenocarcinoma of a Chinese cohort.

BACKGROUND: Pancreatic adenocarcinoma (PAAD) is one of the most lethal carcinomas, and the current histopathological classifications are of limited use in clinical decision-making. There is an unmet need to identify new biomarkers for prognosis-informative molecular subtyping and ultimately for precision medicine. METHODS: We profiled genomic alterations for 608 PAAD patients in a Chinese cohort, including somatic mutations, pathogenic germline variants and copy number variations (CNV). Using the CNV information, we performed unsupervised consensus clustering of these patients, differential CNV analysis and functional/pathway enrichment analysis. Cox regression was conducted for progression-free survival analysis, the elastic net algorithm used for prognostic model construction, and rank-based gene set enrichment analysis for exploring tumor microenvironments. FINDINGS: Our data did not support prognostic value of point mutations in either highly mutated genes (such as KRAS, TP53, CDKN2A and SMAD4) or homologous recombination repair genes. Instead, associated with worse prognosis were amplified genes involved in DNA repair and receptor tyrosine kinase (RTK) related signalings. Motivated by this observation, we categorized patients into four molecular subtypes (namely repair-deficient, proliferation-active, repair-proficient and repair-enhanced) that differed in prognosis, and also constructed a prognostic model that can stratify patients with low or high risk of relapse. Finally, we analyzed publicly available datasets, not only reinforcing the prognostic value of our identified genes in DNA repair and RTK related signalings, but also identifying tumor microenvironment correlates with prognostic risks. INTERPRETATION: Together with the evidence from genomic footprint analysis, we suggest that repair-deficient and proliferation-active subtypes are better suited for DNA damage therapies, while immunotherapy is highly recommended for repair-proficient and repair-enhanced subtypes. Our results represent a significant step in molecular subtyping, diagnosis and management for PAAD patients. FUNDING: This work was supported by the National Natural Science Foundation of China (grant numbers 81470894, 81502695, 81672325, 81871906, 82073326, 82103482 and 32170663), the Shanghai Sailing Program (grant number 20YF1426900), and the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning (awarded to H.F.).

Atractylenolide­1 alleviates gastroparesis in diabetic rats by activating the stem cell factor/c­kit signaling pathway.

Diabetic gastroparesis (DGP), also known as delayed gastric emptying, is a common complication of diabetes mellitus. There are numerous clinical symptoms associated with DGP, as well as high treatment costs and markedly reduced patient quality of life. However, the pathogenesis of DGP is not clear, thus effective treatment methods are yet to be established. In the present study, a DGP rat model was established in Sprague­Dawley rats by the intraperitoneal injection of streptozotocin (STZ). DGP model rats were treated with different doses of atractylenolide­1 to detect alterations in gastrointestinal function, including gastroparesis, gastric emptying, gastric motility, gastric peristalsis and gastric blood flow. Compared with the DGP group, atractylenolide­1 treatment significantly reduced glycaemia and the level of glycated hemoglobin, as well as restoring gastrointestinal function. Gastroparesis, gastric emptying, gastric motility, gastric peristalsis and gastric blood flow were significantly impaired in the STZ­induced group compared with the vehicle control group. Moreover, the STZ­induced group displayed downregulated expression levels of the DGP indicator KIT proto­oncogene, receptor tyrosine kinase (c­kit), as investigated by immunohistochemistry, and stem cell factor (SCF) protein, as assessed using ELISA, significantly enhanced rat interstitial cells of Cajal (ICC) apoptosis, and significantly altered levels of oxidative stress­related markers (malondialdehyde and superoxide dismutase) in the serum and gastric tissues compared with the vehicle control group. By contrast, treatment with atractylenolide­1 significantly counteracted the effects of DGP on peristalsis, inhibited apoptosis and suppressed oxidative stress by regulating the expression of heme oxygenase 1 in STZ­induced DGP model rats. Further research indicated that atractylenolide­1 regulated oxidative stress reactions and improved gastric function by activating the SCF/c­kit signaling pathway. Collectively, the results of the present study suggested that atractylenolide­1 promoted ICC survival and preserved the structure of the gastric tissue network in a DGP rat model via the SCF/c­kit signaling pathway, providing novel insights for the treatment of DGP.

Emerging cell biological functions of phosphatidylinositol 5 phosphate 4 kinase.

The generation of phosphoinositides (PIs) with spatial and temporal control is a key mechanism in cellular organization and signaling. The synthesis of PIs is mediated by PI kinases, proteins that are able to phosphorylate unique substrates at specific positions on the inositol headgroup to generate signaling molecules. Phosphatidylinositol 5 phosphate 4 kinase (PIP4K) is one such lipid kinase that is able to specifically phosphorylate phosphatidylinositol 5 phosphate, the most recently discovered PI to generate the well-known and abundant PI, phosphatidylinositol 4,5 bisphosphate [PI(4,5)P2]. PIP4K appears to be encoded only in metazoan genomes, and several genetic studies indicate important physiological functions for these enzymes in metabolism, immune function, and growth control. PIP4K has recently been reported to localize to multiple cellular compartments, including the nucleus, plasma membrane, endosomal systems, and autophagosome. However, the biochemical activity of these enzymes that is relevant to these physiological functions remains elusive. We review recent developments in this area and highlight emerging roles for these enzymes in cellular organization.

Role of receptor tyrosine kinases mediated signal transduction pathways in tumor growth and angiogenesis-New insight and futuristic vision.

In the past two decades, significant progress has been made in the past two decades towards the understanding of the basic mechanisms underlying cancer growth and angiogenesis. In this context, receptor tyrosine kinases (RTKs) play a pivotal role in cell proliferation, differentiation, growth, motility, invasion, and angiogenesis, all of which contribute to tumor growth and progression. Mutations in RTKs lead to abnormal signal transductions in several pathways such as Ras-Raf, MEK-MAPK, PI3K-AKT and mTOR pathways, affecting a wide range of biological functions including cell proliferation, survival, migration and vascular permeability. Increasing evidence demonstrates that multiple kinases are involved in angiogenesis including RTKs such as vascular endothelial growth factor, platelet derived growth factor, epidermal growth factor, insulin-like growth factor-1, macrophage colony-stimulating factor, nerve growth factor, fibroblast growth factor, Hepatocyte Growth factor, Tie 1 & 2, Tek, Flt-3, Flt-4 and Eph receptors. Overactivation of RTKs and its downstream regulation is implicated in tumor initiation and angiogenesis, representing one of the hallmarks of cancer. This review discusses the role of RTKs, PI3K, and mTOR, their involvement, and their implication in pro-oncogenic cellular processes and angiogenesis with effective approaches and newly approved drugs to inhibit their unrestrained action.

Loss of UTX/KDM6A and the activation of FGFR3 converge to regulate differentiation gene-expression programs in bladder cancer.

Bladder cancer prognosis is closely linked to the underlying differentiation state of the tumor, ranging from the less aggressive and most-differentiated luminal tumors to the more aggressive and least-differentiated basal tumors. Sequencing of bladder cancer has revealed that loss-of-function mutations in chromatin regulators and mutations that activate receptor tyrosine kinase (RTK) signaling frequently occur in bladder cancer. However, little is known as to whether and how these two types of mutations functionally interact or cooperate to regulate tumor growth and differentiation state. Here, we focus on loss of the histone demethylase UTX (also known as KDM6A) and activation of the RTK FGFR3, two events that commonly cooccur in muscle invasive bladder tumors. We show that UTX loss and FGFR3 activation cooperate to disrupt the balance of luminal and basal gene expression in bladder cells. UTX localized to enhancers surrounding many genes that are important for luminal cell fate, and supported the transcription of these genes in a catalytic-independent manner. In contrast to UTX, FGFR3 activation was associated with lower expression of luminal genes in tumors and FGFR inhibition increased transcription of these same genes in cell culture models. This suggests an antagonistic relationship between UTX and FGFR3. In support of this model, UTX loss-of-function potentiated FGFR3-dependent transcriptional effects and the presence of UTX blocked an FGFR3-mediated increase in the colony formation of bladder cells. Taken together, our study reveals how mutations in UTX and FGFR3 converge to disrupt bladder differentiation programs that could serve as a therapeutic target.

Quantitative Phosphoproteomics Reveals System-Wide Phosphorylation Network Altered by Spry in Mouse Mammary Stromal Fibroblasts.

Understanding the fundamental role of the stroma in normal development and cancer progression has been an emerging focus in recent years. The receptor tyrosine kinase (RTK) signaling pathway has been reported playing critical roles in regulating the normal and cancer microenvironment, but the underlying mechanism is still not very clear. By applying the quantitative phosphoproteomic analysis of Sprouty proteins (SPRYs), generic modulators of RTK signaling and deleted mouse mammary fibroblasts, we quantified a total of 11,215 unique phosphorylation sites. By contrast, 554 phosphorylation sites on 425 proteins had SPRY-responsive perturbations. Of these, 554 phosphosites, 362 sites on 277 proteins, were significantly increased, whereas 192 sites on 167 proteins were decreased. Among the regulated proteins, we identified 31 kinases, 7 phosphatases, and one phosphatase inhibitor that were not systematically characterized before. Furthermore, we reconstructed a phosphorylation network centered on RTK signaling regulated by SPRY. Collectively, this study uncovered a system-wide phosphorylation network regulated by SPRY, providing an additional insight into the complicated RTK signaling pathways involved in the mammary gland microenvironment.

Silencing of COPB2 inhibits the proliferation of gastric cancer cells and induces apoptosis via suppression of the RTK signaling pathway.

Emerging studies have reported that coatomer protein complex subunit ß2 (COPB2) is overexpressed in several types of malignant tumor; however, to the best of our knowledge, no studies regarding COPB2 in gastric cancer have been published thus far. Therefore, the present study aimed to determine the significance and function of COPB2 in gastric cancer. COPB2 expression in gastric cancer cell lines was measured using reverse transcription­quantitative polymerase chain reaction (RT­qPCR) analysis. In addition, lentivirus­short hairpin RNA (shRNA) COPB2 (Lv­shCOPB2) was generated and used to infect BGC­823 cells to analyze the effects of COPB2 on the cancerous phenotype. The effects of shRNA­mediated COPB2 knockdown on cell proliferation were detected using MTT, 5­bromo­2­deoxyuridine and colony formation assays. In addition, the effects of COPB2 knockdown on apoptosis were analyzed by flow cytometry. Nude mice and fluorescence imaging were used to characterize the regulation of tumor growth in vivo, and qPCR and immunohistochemistry were subsequently conducted to analyze COPB2 expression in xenograft tumor tissues. Furthermore, a receptor tyrosine kinase (RTK) signaling pathway antibody array was used to explore the relevant molecular mechanisms underlying the effects of COPB2 knockdown. The results revealed that COPB2 mRNA was abundantly overexpressed in gastric cancer cell lines, whereas knockdown of COPB2 significantly inhibited cell growth and colony formation ability, and led to increased cell apoptosis in vitro. The tumorigenicity assay revealed that knockdown of COPB2 reduced tumor growth in nude mice, and fluorescence imaging indicated that the total radiant efficiency of mice in the Lv­shCOPB2­infected group was markedly reduced compared with the mice in the Lv­shRNA control­infected group in vivo. The antibody array assay revealed that the levels of phosphorylation in 23 target RTKs were significantly reduced: In conclusion, COPB2 was highly expressed in gastric cancer cell lines, and knockdown suppressed colony formation and promoted cell apoptosis via inhibiting the RTK signaling and its downstream signaling cascade molecules. Therefore, COPB2 may present a valuable target for gene silencing strategy in gastric cancer.

Tuned polymerization of the transcription factor Yan limits off-DNA sequestration to confer context-specific repression.

During development, transcriptional complexes at enhancers regulate gene expression in complex spatiotemporal patterns. To achieve robust expression without spurious activation, the affinity and specificity of transcription factor-DNA interactions must be precisely balanced. Protein-protein interactions among transcription factors are also critical, yet how their affinities impact enhancer output is not understood. The Drosophila transcription factor Yan provides a well-suited model to address this, as its function depends on the coordinated activities of two independent and essential domains: the DNA-binding ETS domain and the self-associating SAM domain. To explore how protein-protein affinity influences Yan function, we engineered mutants that increase SAM affinity over four orders of magnitude. This produced a dramatic subcellular redistribution of Yan into punctate structures, reduced repressive output and compromised survival. Cell-type specification and genetic interaction defects suggest distinct requirements for polymerization in different regulatory decisions. We conclude that tuned protein-protein interactions enable the dynamic spectrum of complexes that are required for proper regulation.

Extracellular Matrix Remodeling Regulates Glucose Metabolism through TXNIP Destabilization.

The metabolic state of a cell is influenced by cell-extrinsic factors, including nutrient availability and growth factor signaling. Here, we present extracellular matrix (ECM) remodeling as another fundamental node of cell-extrinsic metabolic regulation. Unbiased analysis of glycolytic drivers identified the hyaluronan-mediated motility receptor as being among the most highly correlated with glycolysis in cancer. Confirming a mechanistic link between the ECM component hyaluronan and metabolism, treatment of cells and xenografts with hyaluronidase triggers a robust increase in glycolysis. This is largely achieved through rapid receptor tyrosine kinase-mediated induction of the mRNA decay factor ZFP36, which targets TXNIP transcripts for degradation. Because TXNIP promotes internalization of the glucose transporter GLUT1, its acute decline enriches GLUT1 at the plasma membrane. Functionally, induction of glycolysis by hyaluronidase is required for concomitant acceleration of cell migration. This interconnection between ECM remodeling and metabolism is exhibited in dynamic tissue states, including tumorigenesis and embryogenesis.

Protein Phase Separation Provides Long-Term Memory of Transient Spatial Stimuli.

Protein/RNA clusters arise frequently in spatially regulated biological processes, from the asymmetric distribution of P granules and PAR proteins in developing embryos to localized receptor oligomers in migratory cells. This co-occurrence suggests that protein clusters might possess intrinsic properties that make them a useful substrate for spatial regulation. Here, we demonstrate that protein droplets show a robust form of spatial memory, maintaining the spatial pattern of an inhibitor of droplet formation long after it has been removed. Despite this persistence, droplets can be highly dynamic, continuously exchanging monomers with the diffuse phase. We investigate the principles of biophysical spatial memory in three contexts: a computational model of phase separation; a novel optogenetic system where light can drive rapid, localized dissociation of liquid-like protein droplets; and membrane-localized signal transduction from clusters of receptor tyrosine kinases. Our results suggest that the persistent polarization underlying many cellular and developmental processes could arise through a simple biophysical process, without any additional biochemical feedback loops.

Regulation of Kinase Activity in the Caenorhabditis elegans EGF Receptor, LET-23.

In the active HER receptor dimers, kinases play distinct roles; one is the catalytically active kinase and the other is its allosteric activator. This specialization enables signaling by the catalytically inactive HER3, which functions exclusively as an allosteric activator upon heterodimerization with other HER receptors. It is unclear whether the allosteric activation mechanism evolved before HER receptors functionally specialized. We determined the crystal structure of the kinase domain of the only EGF receptor in Caenorhabditis elegans, LET-23. Our structure of a non-human EGFR kinase reveals autoinhibitory features conserved in the human counterpart. Strikingly, mutations within the putative allosteric dimer interface abrogate activity of the isolated LET-23 kinase and of the full-length receptor despite these regions being only partially conserved with human EGFR. Our results indicate that ancestral EGFRs have built-in features that poise them for allosteric activation that could facilitate emergence of the catalytically dead, yet functional, orthologs.

Induced sensitivity to EGFR inhibitors is mediated by palmitoylated cysteine 1025 of EGFR and requires oncogenic Kras.

Currently, there are no effective therapeutic strategies targeting Kras driven cancers, and therefore, identifying new targeted therapies and overcoming drug resistance have become paramount for effective long-term cancer therapy. We have found that reducing expression of the palmitoyl transferase DHHC20 increases cell death induced by the EGFR inhibitor gefitinib in Kras and EGFR mutant cell lines, but not MCF7 cells harboring wildtype Kras. We show that the increased gefitinib sensitivity in cancer cells induced by DHHC20 inhibition is mediated directly through loss of palmitoylation on a previously identified cysteine residue in the C-terminal tail of EGFR. We utilized an EGFR point mutant in which the palmitoylated cysteine 1025 is mutated to alanine (EGFRC1025A), that results in receptor activation. Expression of the EGFR mutant alone in NIH3T3 cells does not increase sensitivity to gefitinib-induced cell death. However, when EGFRC1025A is expressed in cells expressing activated KrasG12V, EGFR inhibitor induced cell death is increased. Surprisingly, lung cancer cells harboring the EGFR inhibitor resistant mutation, T790M, become sensitive to EGFR inhibitor treatment when DHHC20 is inhibited. Finally, the small molecule, 2-bromopalmitate, which has been shown to inhibit palmitoyl transferases, acts synergistically with gefitinib to induce cell death in the gefitinib resistant cell line NCI-H1975.

Sodium butyrate enhances the growth inhibitory effect of sunitinib in human renal cell carcinoma cells.

Sunitinib (SU) is a small molecule that inhibits the receptor tyrosine kinase (RTK) signaling pathway, and has been clinically used to treat advanced renal cell carcinoma (RCC). However, SU is not always effective as RCC is a highly chemoresistant type of cancer. One of the factors that confer chemoresistance to RCC is a hypoxic condition. Lack of oxygen activates hypoxia-inducible factor (HIF) protein, which is followed by the upregulation of growth factors, including vascular endothelial growth factor and activation of the RTK signaling pathway. In this context, histone deacetylase inhibitors (HDACIs) are considered prominent combined agents for SU as they downregulate the expression of HIFs. Therefore, the present study aimed to investigate the effectiveness of combined treatment with SU and sodium butyrate (NaBu), an HDACI. Long-term exposure to these agents exerted a stronger growth inhibitory effect in RCC cell lines compared with single treatment groups. Furthermore, combined treatment suppressed HIF-2α protein, which was induced under hypoxic conditions. In addition, this combination sustained the activity of the RTK signaling pathway to the level of intact cells, although a single treatment with SU or NaBu was demonstrated to increase this activity. Overall, it is suggested that the combination of SU and NaBu is effective for overcoming drug resistance in RCC.

Role of stem cell growth factor/c-Kit in the pathogenesis of irritable bowel syndrome.

Irritable bowel syndrome (IBS) is a functional bowel disease with a complicated etiopathogenesis, often characterized by gastrointestinal motility disorder and high visceral sensitivity. IBS is a comprehensive multi-systemic disorder, with the interaction of multiple factors, such as mental stress, intestinal function and flora, heredity, resulting in the disease. The existence of a common mechanism underlying the aforementioned factors is currently unknown. The lack of therapies that comprehensively address the disease symptoms, including abdominal pain and diarrhea, is a limitation of current IBS management. The current review has explored the role of the SCF/c-Kit receptor/ligand system in IBS. The SCF/c-Kit system constitutes a classical ligand/receptor tyrosine kinase signaling system that mediates inflammation and smooth muscle contraction. Additionally, it provides trophic support to neural crest-derived cell types, including the enteric nervous system and mast cells. The regulation of SCF/c-Kit on the interstitial cells of Cajal (ICC) suggest that it may play a key role in the aberrant intestinal dynamics and high visceral sensitivity observed in IBS. The role of the SCF/c-Kit system in intestinal motility, inflammation and nerve growth has been reported. From the available biomedical evidence on the pathogenesis of IBS, it has been concluded that the SCF-c-Kit system is a potential therapeutic target for rational drug design in the treatment of IBS.