Mechanisms of regulation and function of G-protein-coupled receptor kinases

G-protein-coupled receptor kinases (GRKs) interact with the agonist-activated form of G-protein-coupled receptor (GPCR) to affect receptor phosphorylation and to initiate profound impairment of receptor signaling, or desensitization. GPCR forms the largest family of cell surface receptors, and defects in GRK function have the potential consequence to affect GPCR-stimulated biological responses in many pathological situations.

Pan-TRK positive uterine sarcoma in immunohistochemistry without neurotrophic tyrosine receptor kinase gene fusions:A case report

BACKGROUND The classification of uterine sarcomas is based on distinctive morphological and immunophenotypic characteristics,increasingly supported by molecular genetic diagnostics.Data on neurotrophic tyrosine receptor kinase(NTRK)gene fusionpositive uterine sarcoma,potentially aggressive and morphologically similar to fibrosarcoma,are limited due to its recent recognition.Pan-TRK immunohistochemistry(IHC)analysis serves as an effective screening tool with high sensitivity and specificity for NTRK-fusion malignancies.CASE SUMMARY We report a case of a malignant mesenchymal tumor originating from the uterine cervix,which was pan-TRK IHC-positive but lacked NTRK gene fusions,accompanied by a brief literature review.A 55-year-old woman presented to the emergency department with abdominal pain and distension,exhibiting significant ascites and multiple solid pelvic masses.Pelvic examination revealed a tumor encompassing the uterine cervix,extending to the vagina and uterine corpus.A punch biopsy of the cervix indicated NTRK sarcoma with positive immunochemical pan-TRK stain.However,subsequent next generation sequencing revealed no NTRK gene fusion,leading to a diagnosis of poorly differentiated,advanced-stage sarcoma.CONCLUSION The clinical significance of NTRK gene fusion lies in potential treatment with TRK inhibitors for positive sarcomas.Identifying such rare tumors is crucial due to the potential applicability of tropomyosin receptor kinase inhibitor treatment.

Targeting receptor tyrosine kinases in gastric cancer

Molecularly targeted therapeutic agents are constantly being developed and have been shown to be effective in various clinical trials. One group of representative targeted oncogenic kinases, the receptor tyrosine kinases (RTKs), has been associated with gastric cancer development. Trastuzumab, an inhibitor of ERBB2, has been approved for the treatment of gastric cancer, although other receptor tyrosine kinases, such as epidermal growth factor receptor, vascular endothelial growth factor, platelet-derived growth factor receptor, c-Met, IGF-1R and fibroblast growth factor receptor 2, are also activated in gastric cancer. The promising results of the trastuzumab clinical trial for gastric cancer resulted in the approval of trastuzumab-based therapy as a first-line treatment for human epidermal growth factor receptor 2-positive patients. On the other hand, the trial examining bevacizumab in combination with conventional chemotherapy did not meet its primary goal of increasing the overall survival time of gastric cancer patients; however, a significantly higher response rate and a longer progression-free survival were observed in the bevacizumab arm of the trial. Other clinical trials, especially phase III trials that have tested drugs targeting RTKs, such as cetuximab, panitumumab, gefitinib, erlotinib, figitumumab, sorafenib, sunitinib and lapatinib, have shown that these drugs have modest effects against gastric cancer. This review summarizes the recent results from the clinical trials of molecularly targeted drugs and suggests that further improvements in the treatment of advanced gastric cancer can be achieved through the combination of conventional drugs with the new molecularly targeted therapies.

Are TrkB receptor agonists the right tool to fulfill the promises for a therapeutic value of the brain-derived neurotrophic factor?

Brain-derived neurotrophic factor signaling via its receptor tro pomyosin receptor kinase B regulates several crucial physiological processes.It has been shown to act in the brain,promoting neuronal survival,growth,and plasticity as well as in the rest of the body where it is involved in regulating for instance aspects of the metabolism.Due to its crucial and very pleiotro pic activity,reduction of brain-derived neurotrophic factor levels and alterations in the brain-derived neurotrophic factor/tropomyosin receptor kinase B signaling have been found to be associated with a wide spectrum of neurological diseases.Howeve r,because of its poor bioavailability and pharmacological properties,brain-derived neurotrophic factor itself has a very low therapeutic value.Moreover,the concomitant binding of exogenous brain-derived neurotrophic factor to the p75 neurotrophin receptor has the potential to elicit several unwanted and deleterious side effects.Therefo re,developing tools and approaches to specifically promote tropomyosin receptor kinase B signaling has become an important goal of translational research.Among the newly developed tools are different categories of tropomyosin receptor kinase B receptor agonist molecules.In this review,we give a comprehensive description of the diffe rent tro pomyosin receptor kinase B receptor agonist drugs developed so far and of the res ults of their application in animal models of several neurological diseases.Moreover,we discuss the main benefits of tropomyosin receptor kinase B receptor agonists,concentrating especially on the new tropomyosin receptor kinase B agonist antibodies.The benefits observed both in vitro and in vivo upon application of tropomyosin receptor kinase B receptor agonist drugs seem to predominantly depend on their general neuroprotective activity and their ability to promote neuronal plasticity.Moreover,tro pomyosin receptor kinase B agonist antibodies have been shown to specifically bind the tropomyosin receptor kinase B receptor and not p75 neurotrophin receptor.Therefore,while,based on the current knowledge,the tropomyosin receptor kinase B receptor agonists do not seem to have the potential to reve rse the disease pathology per se,promoting brainderived neurotrophic factor/tro pomyosin receptor kinase B signaling still has a very high therapeutic relevance.

Diabetes and high-glucose could upregulate the expression of receptor for activated C kinase 1 in retina

BACKGROUND Diabetic retinopathy(DR)is a major ocular complication of diabetes mellitus,leading to visual impairment.Retinal pigment epithelium(RPE)injury is a key component of the outer blood retinal barrier,and its damage is an important indicator of DR.Receptor for activated C kinase 1(RACK1)activates protein kinase C-ε(PKC-ε)to promote the generation of reactive oxygen species(ROS)in RPE cells,leading to apoptosis.Therefore,we hypothesize that the activation of RACK1 under hypoxic/high-glucose conditions may promote RPE cell apoptosis by modulating PKC-ε/ROS,thereby disrupting the barrier effect of the outer blood retinal barrier and contributing to the progression of DR.AIM To investigate the role and associated underlying mechanisms of RACK1 in the development of early DR.METHODS In this study,Sprague-Dawley rats and adult RPE cell line-19(ARPE-19)cells were used as in vivo and in vitro models,respectively,to explore the role of RACK1 in mediating PKC-εin early DR.Furthermore,the impact of RACK1 on apoptosis and barrier function of RPE cells was also investigated in the former model.RESULTS Streptozotocin-induced diabetic rats showed increased apoptosis and upregulated expression of RACK1 and PKC-εproteins in RPE cells following a prolonged modeling.Similarly,ARPE-19 cells exposed to high glucose and hypoxia displayed elevated mRNA and protein levels of RACK1 and PKC-ε,accompanied by an increases in ROS production,apoptosis rate,and monolayer permeability.However,silencing RACK1 significantly downregulated the expression of PKC-εand ROS,reduced cell apoptosis and permeability,and protected barrier function.CONCLUSION RACK1 plays a significant role in the development of early DR and might serve as a potential therapeutic target for DR by regulating RPE apoptosis and barrier function.

Characterization of a S-locus-related Receptor-like Kinase Cluster in Rice Chromosome 4

We have identified 14 S _locus glycoprotein (SLG)_related protein kinase genes in a 323 kb contig of rice (Oryza sativa L.) chromosome 4 and we detected the transcription pattern of this gene cluster by reverse transcription_polymerase reaction (RT_PCR). RT_PCR results revealed that nine putative genes were transcribed in rice and these genes had the different expression patterns: two genes are expressed predominantly in reproductive tissues while the other seven genes are expressed in both reproductive and vegetative tissues. Analysis of the predicted amino acid sequences demonstrated that the extracellular receptor domains are highly homologous to SLG of Brassica, whereas the cytoplasmic kinase domains contain conserved amino acids present in serine/threonine kinases.

Effects of laser photocoagulation on serum angiopoietin-1, angiopoietin-2, angiopoietin-1/angiopoietin-2 ratio, and soluble angiopoietin receptor Tie-2 levels in type 2 diabetic patients with proliferative diabetic retinopathy

·AIM: To determine the effects of laser photocoagulation on serum levels of angiopoietin-1(Ang-1),angiopoietin-2(Ang-2), soluble angiopoietin receptor Tie-2(Tie-2), Ang-1/Ang-2 ratio and vascular endothelial growth factor(VEGF) in patients with type 2diabetes mellitus(T2DM) and proliferative diabetic retinopathy(PDR). We also explored the role of the Ang/Tie system in PDR.·METHODS:Totally 160patientswithT2 DM, including50 patients with non-diabetic retinopathy(NDR), 58 patients with non-proliferative diabetic retinopathy(NPDR), and52 patients with PDR were enrolled in this study. Serum Ang-1, Ang-2, Tie-2 receptor and VEGF levels were measured using enzyme-linked immunosorbent assays for all patients and were repeated in 26 patients who underwent laser photocoagulation two months after the procedure.·RESULTS:ThemedianlevelsofAng-2andVEGFinserum were significantly higher in the NPDR group(4.23 ng/mL and 303.2 pg/mL, respectively) compared to the NDR group(2.67 ng/mL and 159.8 pg/mL, respectively, P 【0.01), with the highest level in the PDR group(6.26 ng/mL and531.2 pg/mL, respectively, P 【0.01). The median level of Ang-1 was significantly higher in the NPDR group(10.77ng/mL) compared to the NDR group(9.31 ng/mL) and the PDR groups(9.54 ng/mL)(P 【0.05), while no difference was observed between the PDR and NDR groups. Ang-1/Ang-2 ratio of PDR group was lowest in three groups(1.49 vs 2.69 and 2.90, both P 【0.01). The median level of Tie-2was not significantly different among three groups(P 】0.05).Ang-2 was positively correlated with VEGF and Tie-2 in the PDR and NPDR groups(both P 【0.05). Among the 26 patients who underwent laser photocoagulation, serum Ang-2 and VEGF levels significantly decreased(both P 【0.05), whereas serum Ang-1 level and Ang-1/Ang-2ratio were weakly increased(P 】0.05). The median levels of Ang-2 and VEGF in serum were highest in PDR group,however, Ang-1/Ang-2 ratio of PDR group was lowest in three groups.·CONCLUSION: Laser photocoagulation can reduce serum Ang-2 and VEGF levels. The Ang/Tie system and VEGF play an important role in the development and progression of T2 DM patients with PDR.

Pathogenesis of RON receptor tyrosine kinase in cancer cells: activation mechanism, functional crosstalk, and signaling addiction

The RON receptor tyrosine kinase, a member of the MET proto-oncogene family, is a pathogenic factor im- plicated in tumor malignancy. Specifically, aberrations in RON signaling result in increased cancer cell growth, survival, invasion, angiogenesis, and drug resistance. Biochemical events such as ligand binding, receptor over- expression, generation of structure-defected variants, and point mutations in the kinase domain contribute to RON signaling activation. Recently, functional crosstalk between RON and signaling proteins such as MET and EFGR has emerged as an additional mechanism for RON activation, which is critical for tumorigenic develop- ment. The RON signaling crosstalk acts either as a regulatory feedback loop that strengthens or enhances tumor- igenic phenotype of cancer cells or serves as a signaling compensatory pathway providing a growth/survival ad- vantage for cancer cells to escape targeted therapy. Moreover, viral oncoproteins derived from Friend leukemia or Epstein-Barr viruses interact with RON to drive viral oncogenesis. In cancer cells, RON signaling is integrated into cellular signaling network essential for cancer cell growth and survival. These activities provide the mo- lecular basis of targeting RON for cancer treatment. In this review, we will discuss recent data that uncover the mechanisms of RON activation in cancer cells, review evidence of RON signaling crosstalk relevant to cancer malignancy, and emphasize the significance of the RON signaling addiction by cancer cells for tumor therapy. Understanding aberrant RON signaling will not only provide insight into the mechanisms of tumor pathogenesis, but also lead to the development of novel strategies for molecularly targeted cancer treatment.

Associations Between Epidermal Growth Factor Receptor Gene Mutation and Serum Tumor Markers in Advanced Lung Adenocarcinomas: A Retrospective Study

Objective To investigate the associations between epidermal growth factor receptor （EGFR） gene mutations and serum tumor markers in advanced lung adenocarcinomas. Methods We investigated the association between EGFR gene mutations and clinical features, including serum tumor marker levels, in 97 advanced lung adenocarcinomas patients who did not undergo the treatment of EGlaR tyrosine kinase inhibitors. EGFR gene mutation was detected by real-time PCR at exons 18, 19, 20, and 21. Serum tumor marker concentrations were analyzed by chemiluminescence assay kit at the same time. Results EGFR gene mutations were detected in 42 （43%） advanced lung adenocarcinoma patients. Gender （P=0.003）, smoking status （P=0.001）, and abnormal serum status of carcinoembryonic antigen （CEA, P=0.028） were significantly associated with EGFR gene mutation incidence. Multivariate analysis showed the abnormal CEA level in serum was independently associated with the incidence of EGFR gene mutation （P=0.046） with an odds ratio of 2.613 （95% Ch 1.018-6.710）. However, receiver operating characteristic （ROC） curve analysis revealed CEA was not an ideal predictive marker for EGFR gene mutation status in advanced lung adenocarcinoma （the area under the ROC curve was 0.608, P=0.069）. Conclusions EGFR gene mutation status is significantly associated with serum CEA status in advanced lung adenocarcinmoas. However, serum CEA is not an ideal predictor for EGFR mutation.

Imipramine protects retinal ganglion cells from oxidative stress through the tyrosine kinase receptor B signaling pathway

Retinal ganglion cell（RGC） degeneration is irreversible in glaucoma and tyrosine kinase receptor B（Trk B）-associated signaling pathways have been implicated in the process.In this study,we attempted to examine whether imipramine,a tricyclic antidepressant,may protect hydrogen peroxide（H_2O_2）-induced RGC degeneration through the activation of the Trk B pathway in RGC-5 cell lines.RGC-5 cell lines were pre-treated with imipramine 30 minutes before exposure to H_2O_2.Western blot assay showed that in H_2O_2-damaged RGC-5 cells,imipramine activated Trk B pathways through extracellular signal-regulated protein kinase/Trk B phosphorylation.TUNEL staining assay also demonstrated that imipramine ameliorated H_2O_2-induced apoptosis in RGC-5 cells.Finally,Trk B-Ig G intervention was able to reverse the protective effect of imipramine on H_2O_2-induced RGC-5 apoptosis.Imipramine therefore protects RGCs from oxidative stress-induced apoptosis through the Trk B signaling pathway.

Expression and functional study of cholecystokinin-A receptors on the interstitial Cajal-like cells of the guinea pig common bile duct

BACKGROUND Many studies have shown that interstitial Cajal-like cell(ICLC)abnormalities are closely related to a variety of dynamic gastrointestinal disorders.ICLCs are pacemaker cells for gastrointestinal movement and are involved in the transmission of nerve impulses.AIM To elucidate the expression profile and significance of cholecystokinin-A(CCK-A)receptors in ICLCs in the common bile duct(CBD),as well as the role of CCK in regulating CBD motility through CCK-A receptors on CBD ICLCs.METHODS The levels of tyrosine kinase receptor(c-kit)and CCK-A receptors in CBD tissues and isolated CBD cells were quantified using the double immunofluorescence labeling technique.The CCK-mediated enhancement of the movement of CBD muscle strips through CBD ICLCs was observed by a muscle strip contraction test.RESULTS Immunofluorescence showed co-expression of c-kit and CCK-A receptors in the CBD muscularis layer.Observations of isolated CBD cells showed that c-kit was expressed on the surface of ICLCs,the cell body and synapse were colored and polygonal,and some cells presented protrusions and formed networks adjacent to the CBD while others formed filaments at the synaptic terminals of local cells.CCK-A receptors were also expressed on CBD ICLCs.At concentrations ranging from 10^(-6) mol/L to 10^(-10) mol/L,CCK promoted CBD smooth muscle contractility in a dose-dependent manner.In contrast,after ICLC removal,the contractility mediated by CCK in CBD smooth muscle decreased.CONCLUSION CCK-A receptors are highly expressed on CBD ICLCs,and CCK may regulate CBD motility through the CCK-A receptors on ICLCs.

Expression of Soluble Vascular Endothelial Growth Factor Receptor-2 and Its Effect on Proliferation of Vascular Endothelial Cells

Vascular endothelial growth factors（VEGFs） respectively bind to each of three receptor tyrosine kinases（RTKs）,known as Flt-1,KDR and Flt-4.Since VEGFs and their respective families of receptor tyrosine kinases（VEGFRs） are critical proteins which can regulate vascular development during angiogenesis,we decided to explore the inhibitory effects of soluble kinase insert domain-containing receptor（sKDR） on endothelial cells and angiogenesis.Total RNA was extracted from human umbilical vein endothelial cells（HUVEC）,and cDNA of extracellular domains 1―4 was amplified and recombined with pQE40 vector.After being expressed,affinity purified,renatured and analyzed by Western blot,the sKDR was assayed for its effects on endothelial cells by [3-（4,5-dimethylthiazol-2-yl）2,5-diphenyltetrazolium bromide]（MTT）,and on angiogenesis by chick chorioallantoic membrane（CAM） experiment.sKDR cDNA of 1150 bp was obtained via real-time polymerase chain reaction（RT-PCR）,and sKDR was expressed by pQE40 procaryotic expression system,purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis（SDS-PAGE） analysis with only one band and proved by Western blot.MTT assay demonstrateds that sKDR could inhibit the VEGF-stimulated HUVEC from proliferation,and CAM experiment showed sKDR could block the VEGF-induced angiogenesis.sKDR has the biological activity to bind with VEGF ligands and is a potential target for tumor anti-angiogenesis therapy.

Increased tumor necrosis factor receptor 1 expression in human colorectal adenomas

AIM: To determine the expression statuses of tumor necrosis factor (TNF)-α, its receptors (TNF-R) and downstream effector molecules in human colorectal adenomas. METHODS: We measured the serum concentrations of TNF-α and its receptors in 62 colorectal adenoma patients and 34 healthy controls. The protein expression of TNF-α, TNF-R1, TNF-R2 and downstream signals of the TNF receptors, such as c-Jun N-terminal kinase (JNK), nuclear factor-κ B and caspase-3, were also investigated in human colorectal adenomas and in normal colorectal mucosal tissues by immunohistochemistry. Immunofluorescence confocal microscopy was used to investigate the consistency of expression of TNF-R1 and phospho-JNK (p-JNK). RESULTS: The serum levels of soluble TNF-R1 (sTNF-R1) in adenoma patients were significantly higher than in the control group (3.67 ± 0.86 ng/mL vs 1.57 ± 0.72 ng/mL, P < 0.001). Receiver operating characteristic analysis revealed the high diagnostic sensitivity of TNF-R1 measurements (AUC was 0.928) for the diagnosis of adenoma, and the best cut-off level of TNF-R1 was 2.08 ng/mL, with a sensitivity of 93.4% and a specificity of 82.4%. There were no significant differences in the serum levels of TNF-α or sTNF-R2 between the two groups. Immunohistochemistry showed high levels of TNF-R1 and p-JNK expression in the epithelial cells of adenomas. Furthermore, a high incidence of co-localization of TNF-R1 and p-JNK was identified in adenoma tissue. CONCLUSION: TNF-R1 may be a promising biomarker of colorectal adenoma, and it may also play an important role in the very early stages of colorectal carcinogenesis.

Direct observation of the autophosphorylation of insulin receptor kinase by mass spectrometry

The catalytic and signaling activities of insulin receptor kinase （IRK） are regulated by the autophosphorylation of three tyrosine residues in a cytoplasmic protein-tyrosine kinase domain at Tyro 1158, Tyro 1162 and Tyro 1163. In this study, time-course of the auphosphorylation of the core kinase （residues 978-1283） from IRK was directly investigated by online electrospray ionization mass spectrometry. It is found that two tyrosine residues were phosphorylated in reaction time range of 30 min. This study implies that mass spectrometric technique must be a powerful tool to directly monitor the biological macromolecular modification and will also provide the information of the order and the mechanism of autophosphorylation at the tyrosine sites coupled with tandem mass spectrometric technique.

Effect of organophosphorus insecticides on phosphorylation of the M_2 muscarinic acetylcholine receptor

BACKGROUND： Organophosphorus insecticides may promote the accumulation of acetylcholine at synapses and the neuromuscular junction by inhibiting acetylcholinesterase activity to cause disturbance of neural signal conduction and induce a toxic reaction. Organophosphorus insecticides may act on M2 muscarinic acetylcholine receptors, whose combination with G proteins is regulated by phosphorylation of G protein-coupled receptor kinase 2. OBJECTIVE： To investigate the effects of organophosphorus insecticides on the phosphorylation of G protein-coupled receptor kinase 2-mediated M2 muscarinic acetylcholine receptors and to reveal other possible actions of organophosphorus insecticides. DESIGN, TIME AND SETTING： An observational study, which was performed in the Central Laboratory of Shenyang Medical College, and Department of Physiological Sciences, College of Veterinary Medicine, Oklahoma State University from June 2002 to December 2004. MATERIALS： Paraoxon, parathion, chlorpyrifos, and chlorpyrifos oxon were provided by Chem Service Company, USA, [γ -p^32] ATP and [^35S]GTP γ S by New England Nuclear Life Science Products, and recombinant β 2-adrenergic receptor membrane protein by Sigma Company, USA. METHODS： The M2 muscarinic acetylcholine receptor was extracted and purified from pig brain using affinity chromatography. Subsequently, the purified M2 muscarinic acetylcholine receptor, G protein-coupled receptor kinase 2, and [γ -p^32] ATP were incubated with different concentrations of paraoxon and chlorpyrifos oxon together. The mixture then underwent polyacrylamide gel electrophoresis, and the gel film was dried and radioactively autographed to detect phosphorylation of the M2 muscarinic acetylcholine receptor. Finally, the radio-labeled phosphorylated M2 receptor protein band was excised for counting with an isotope liquid scintillation counter. MAIN OUTCOME MEASURES： Effects of chlorpyrifos oxon, paraoxon, chlorpyrifos, and parathion in different concentrations on the phosphorylation of the M2 muscarinic acetylcholine receptor; effects of chlorpyrifos oxon on the phosphorylation of the β -adrenergic receptor. RESULTS： Chlorpyrifos oxon could completely inhibit the phosphorylation of the M2 muscarinic acetylcholine receptor, and its IC50 was 70 μ mol/L. Chlorpyrifos could also inhibit the phosphorylation of the M2 muscarinic acetylcholine receptor. However, paraoxon and parathion could not inhibit the phosphorylation of the M2 muscarinic acetylcholine receptor. Chlorpyrifos oxon in different concentrations could also not inhibit the phosphorylation of the β 2-adrenergic receptor catalyzed by G protein-coupled receptor kinase 2. CONCLUSION： Different kinds of organophosphorus insecticides have different effects on the phosphorylation of the G protein-coupled receptor kinase 2-mediated M2 muscarinic acetylcholine receptor. Organophosphorus insecticides possibly have different toxic effects.

Involvement of Met receptor pathway in aggressive behavior of colorectal cancer cells induced by parathyroid hormone-related peptide

BACKGROUND Parathyroid hormone-related peptide(PTHrP)plays a key role in the development and progression of many tumors.We found that in colorectal cancer(CRC)HCT116 cells,the binding of PTHrP to its receptor PTHR type 1(PTHR1)activates events associated with an aggressive phenotype.In HCT116 cell xenografts,PTHrP modulates the expression of molecular markers linked to tumor progression.Empirical evidence suggests that the Met receptor is involved in the development and evolution of CRC.Based on these data,we hypothesized that the signaling pathway trigged by PTHrP could be involved in the transactivation of Met and consequently in the aggressive behavior of CRC cells.AIM To elucidate the relationship among PTHR1,PTHrP,and Met in CRC models.METHODS For in vitro assays,HCT116 and Caco-2 cells derived from human CRC were incubated in the absence or presence of PTHrP(1-34)(10-8 M).Where indicated,cells were pre-incubated with specific kinase inhibitors or dimethylsulfoxide,the vehicle of the inhibitors.The protein levels were evaluated by Western blot technique.Real-time polymerase chain reaction(RT-qPCR)was carried out to determine the changes in gene expression.Wound healing assay and morpho logical monitoring were performed to evaluate cell migration and changes related to the epithelialmesenchymal transition(EMT),respectively.The number of viable HCT116 cells was counted by trypan blue dye exclusion test to evaluate the effects of irinotecan(CPT-11),oxaliplatin(OXA),or doxorubicin(DOXO)with or without PTHrP.For in vivo tests,HCT116 cell xenografts on 6-wk-old male N:NIH(S)_nu mice received daily intratumoral injections of PTHrP(40μg/kg)in 100μL phosphate-buffered saline(PBS)or the vehicle(PBS)as a control during 20 d.Humanitarian slaughter was carried out and the tumors were removed,weighed,and fixed in a 4%formaldehyde solution for subsequent treatment by immunoassays.To evaluate the expression of molecular markers in human tumor samples,we studied 23 specimens obtained from CRC patients which were treated at the Hospital Interzonal de Graves y Agudos Dr.JoséPenna(Bahía Blanca,Buenos Aires,Argentina)and the Hospital Provincial de Neuquén(Neuquén,Neuquén,Argentina)from January 1990 to December 2007.Seven cases with normal colorectal tissues were assigned to the control group.Tumor tissue samples and clinical histories of patients were analyzed.Paraffin-embedded blocks from primary tumors were reviewed by hematoxylin-eosin staining technique;subsequently,representative histological samples were selected from each patient.From each paraffin block,tumor sections were stained for immunohistochemical detection.The statistical significance of differences was analyzed using proper statistical analysis.The results were considered statistically significant at P<0.05.RESULTS By Western blot analysis and using total Met antibody,we found that PTHrP regulated Met expression in HCT116 cells but not in Caco-2 cells.In HCT116 cells,Met protein levels increased at 30 min(P<0.01)and at 20 h(P<0.01)whereas the levels diminished at 3 min(P<0.05),10 min(P<0.01),and 1 h to 5 h(P<0.01)of PTHrP treatment.Using an active Met antibody,we found that where the protein levels of total Met decreased(3 min,10 min,and 60 min of PTHrP exposure),the status of phosphorylated/activated Met increased(P<0.01)at the same time,suggesting that Met undergoes proteasomal degradation after its phosphorylation/activation by PTHrP.The increment of its protein level after these decreases(at 30 min and 20 h)suggests a modulation of Met expression by PTHrP in order to improve Met levels and this idea is supported by our observation that the cytokine increased Met mRNA levels at least at 15 min in HCT116 cells as revealed by RT-qPCR analysis(P<0.05).We then proceeded to evaluate the signaling pathways that mediate the phosphorylation/activation of Met induced by PTHrP in HCT116 cells.By Western blot technique,we observed that PP1,a specific inhibitor of the activation of the protooncogene protein tyrosine kinase Src,blocked the effect of PTHrP on Met phosphorylation(P<0.05).Furthermore,the selective inhibition of the ERK 1/2 mitogen-activated protein kinase(ERK 1/2 MAPK)using PD98059 and the p38 MAPK using SB203580 diminished the effect of PTHrP on Met phosphorylation/activation(P<0.05).Using SU11274,the specific inhibitor of Met activation,and trypan blue dye exclusion test,Western blot,wound healing assay,and morphological analysis with a microscope,we observed the reversal of cell events induced by PTHrP such as cell proliferation(P<0.05),migration(P<0.05),and the EMT program(P<0.01)in HCT116 cells.Also,PTHrP favored the chemoresistance to CPT-11(P<0.001),OXA(P<0.01),and DOXO(P<0.01)through the Met pathway.Taken together,these findings suggest that Met activated by PTHrP participates in events associated with the aggressive phenotype of CRC cells.By immunohistochemical analysis,we found that PTHrP in HCT116 cell xenografts enhanced the protein expression of Met(0.190±0.014)compared to tumors from control mice(0.110±0.012;P<0.05)and of its own receptor(2.27±0.20)compared to tumors from control mice(1.98±0.14;P<0.01).Finally,assuming that the changes in the expression of PTHrP and its receptor are directly correlated,we investigated the expression of both Met and PTHR1 in biopsies of CRC patients by immunohistochemical analysis.Comparing histologically differentiated tumors with respect to those less differentiated,we found that the labeling intensity for Met and PTHR1 increased and diminished in a gradual manner,respectively(P<0.05).CONCLUSION PTHrP acts through the Met pathway in CRC cells and regulates Met expression in a CRC animal model.More basic and clinical studies are needed to further evaluate the PTHrP/Met relationship.

Levetiracetam induces tyrosine kinase receptor B expression in SH-SY5Y cells

Tyrosine kinase receptor B （TrkB） plays an important role in long-term potentiation and memory formation.The present study used all-trans retinoic acid to induce TrkB expression in SH-SY5Y cells,and observed the effects of levetiracetam （LEV） on TrkB expression.Following exposure to 10,50,and 100 μg/mL LEV,the number of TrkB-positive cells,and average absorbance value were increased.Results demonstrated that LEV can induce TrkB expression in SH-SY5Y cells.

Neurotrophic receptor tyrosine kinase family members in secretory and non-secretory breast carcinomas

BACKGROUND Breast cancer is the most common female cancer and a major cause of morbidity and mortality.Progress in breast cancer therapeutics has been attained with the introduction of targeted therapies for specific sub-sets.However,other subsets lack targeted interventions and thus there is persisting need for identification and characterization of molecular targets in order to advance breast cancer therapeutics.AIM To analyze the role of lesions in neurotrophic receptor tyrosine kinase(NTRK)genes in breast cancers.METHODS Analysis of publicly available genomic breast cancer datasets was performed for identification and characterization of cases with fusions and other molecular abnormalities involving NTRK1,NTRK2 and NTRK3 genes.RESULTS NTRK fusions are present in a small number of breast cancers at the extensive GENIE project data set which contains more than 10000 breast cancers.These cases are not identified as secretory in the database,suggesting that the histologic characterization is not always evident.In the breast cancer The Cancer Genome Atlas(TCGA)cohort the more common molecular lesion in NTRK genes is amplification of NTRK1 observed in 7.9% of breast cancers.CONCLUSION Neurotrophin receptors molecular lesions other than fusions are observed more often than fusions.However,currently available NTRK inhibitors are effective mainly for fusion lesions.Amplifications of NTRK1,being more frequent in breast cancers,could be a viable therapeutic target if inhibitors efficacious for them become available.

Role of Tyrosine Kinase Receptors in Growth Factor Mediated Signal Transduction, with Specific Reference to MAPK/Rasand p13k-Akt Containing Pathways in Oncogenesis: A Qualitative Database Review

Receptor Tyrosine kinases (RTKs) play a crucial role in the signal transduction pathways at cellular levels. RTK plays a vital role in cellular communication and transmission of signals to the adjacent cells and regulates different functions of the cell, such as cellular growth, differentiation, metabolism and motility. RTK s triggers growth factor receptors such as epidermal growth factor, insulin growth factor-1 receptor, platelet derived growth factor receptor, and fibro blast growth factor receptor and vascular endothelial growth factor receptor, thereby initiating and regulating cell growth and proliferation. MAPK/RAS and PI3/AKT pathways are the major pathways of RTK’s function. Dysregulation of these RTK’s and pathways often leads to many diseases such as Noonan Syndrome, Logius Syndrome, CFC syndrome and different types of cancer. Point mutation and over expression of receptors and mutations in Ras leads to 30% of human cancers. Also over expression of different growth factor receptors by RTK too lead to several types of cancers as Glioblastoma, Thyroid cancer, Colon cancer and Non-small cell lung cancer. PTEN mutation in PI3/AKT pathway often leads to carcinoma relative to Thyroid, Skin, Large intestine, eye and Bone. Therefore, these RTK’s often used as targets for cancer therapies. The medical sector uses various types of small molecule tyrosine kinase inhibitors such as ATP competitive inhibitors, Allosteric inhibitors and covalent inhibitors which are known as Afatinib, Crizotinib, Eroltinib, Icotinib, Lepatinib and Lenvatinib in treatment and management of differential carcinomas.

Correlation between expression of two transforming growth factor-beta 1 receptors and microvascular density in a rat model of cerebral ischemia and reperfusion injury

The effects of transforming growth factor-β1 （TGF-β1） are currently controversial. Whether TGF-β1 promotes or inhibits revascularization under different conditions remains poorly understood. Based on previous studies, the current experiment established rat models of cerebral ischemia and reperfusion injury （IRI）, and demonstrated that pathological and functional damage was also increased after IRI. The most serious damage was observed at 3 days after reperfusion, at which time microvascular density fell to its lowest level. Soon afterwards, microvascular density increased, new collateral circulation was gradually established at 4 to 7 days after reperfusion, and pathological damage and neurological deficits were improved. TGF-β1, activin receptor-like kinase 5 （ALK5） mRNA and protein expression levels increased gradually over time. In contrast, ALK1 mRNA and protein expression decreased over the same period. A significant negative correlation was detected between microvascular density and expression of the ALK5 gene transcript. There was no correlation between microvascular density and ALK1 gene transcriptional expression following cerebral IRI in a rat model. These findings suggest that ALK5, rather than ALK1, is the critical receptor in the TGF-β1 signal pathways after cerebral IRI.