MicroRNA‐137‐mediated Src oncogenic signaling promotes cancer progression

The tyrosine kinase c‐Src is frequently overexpressed and activated in a wide variety of human cancers. However, the molecular mechanisms responsible for the upregulation of c‐Src remain elusive. To examine whether microRNA‐mediated c‐Src upregulation promotes cancer progression, we screened miRNAs with complementarity to the 3′‐UTR of c‐Src mRNA. Among these miRNAs, down‐regulation of miR‐137 was tightly associated with c‐Src‐mediated tumor progression of human colon cancer cells/tissues. Re‐expression of miR‐137 in human colon cancer cells suppressed tumor growth and caused the disruption of focal contacts, suppression of cell adhesion, and invasion, although restoration of c‐Src in miR‐137‐treated cells could not fully rescue the tumor‐suppressive effect of miR‐137. We found that miR‐137 targets AKT2 and paxillin also and miR‐137‐mediated regulation of c‐Src /AKT2 is crucial for controlling tumor growth, whereas that of c‐Src/paxillin contributes to malignancy. miR‐137 suppressed Src‐related oncogenic signaling and changed the expression of miRNAs that are regulated by Src activation. miR‐137 controls the expression of c‐Src/AKT2/paxillin and synergistically suppresses Src oncogenic signaling evoked from focal adhesions. In various human cancers that harbor c‐Src upregulation, the dysfunction of this novel mechanism would serve as a critical trigger for tumor progression.     

胰腺癌BxPC3细胞中Src激酶对Notch-1活化的调节

目的 探讨在胰腺癌细胞BxPC3中,Src激酶对Notch-1活化的影响.方法 用siRNA干扰的方法分别抑制Notch-1和c-Src的表达;加入Src激酶抑制剂PP2抑制Src激酶活性;MTT法检测细胞的生长;Western blot检测Notch-1蛋白活性形式NICD水平的变化.结果 抑制Notch-1表达及抑制Src激酶活性可明显抑制BxPC3细胞生长;抑制Src激酶活性及抑制c-Src蛋白表达可下调Notch-1 NICD水平.结论 Src激酶在胰腺癌细胞BxPC3中促进Notch-1的活化,促进BxPc3细胞的生长.     

Src family protein tyrosine kinase signaling mediates monosodium urate crystal-induced IL-8 expression by monocytic THP-1 cells.

Neutrophil-dependent inflammation dependent on monosodium urate (MSU) crystal-induced IL-8 expression occurs in gout. MSU crystals activate phagocyte Src family tyrosine kinases and the serine/threonine kinase p70s6k. Thus, using monocytic THP-1 cells, we assessed the potential for Src family kinases and p70s6k to mediate MSU-induced IL-8 expression. MSU crystals induced phosphorylation of p70s6k and the Src kinases c-Src, Lyn, Hck, and Fyn. IL-8 expression was attenuated more by the Src kinase inhibitor PP1 than by the p70s6k inhibitor rapamycin. PP1 inhibited crystal-induced phosphorylation of ERK1/2 and IkappaBalpha and suppressed IkappaB kinase (IKK) activation and NF-kappaB binding to the IL-8 promoter, signals that mediate MSU-induced IL-8 expression. Transfection of the native Src inhibitor, C-terminal Src kinase (Csk), also suppressed crystal-induced c-Src, ERK1/2, and IkappaBalpha phosphorylation and IL-8 expression. We conclude that Src family tyrosine kinase signaling plays a significant role in MSU crystal-induced IL-8 expression via stimulation of ERK1/2 pathway and NF-kappaB activation.     

Src Tyrosine Kinase Inhibitor,M475271, Suppresses Subcutaneous Growth and Production of Lung Metastasis Via Inhibition of Proliferation,Invasion, and Vascularization of Human Lung Adenocarcinoma Cells

Src, a proto-oncogene, has been strongly implicated in the growth, progression and metastasis of a number of human cancers. Its role in lung cancer is, however, still unknown. In the present study, we assessed the expression of Src in three different human lung adenocarcinoma cell lines (PC-9, PC14PE6, A549), and explored the effect of a novel Src kinase inhibitor, M475271, on the behavior of the cell lines. The three cell lines expressed various levels of auto-phosphorylated Src. While M475271 reduced Src-phosphorylation and invasiveness of all three cell lines, it inhibited the proliferation of PC-9 and A549 cells with highly phosphorylated Src, but not PC14PE6 cells. We further examined the effect of M475271 on subcutaneous tumors and lung metastasis caused by PC-9 and/or A549 cells in NK-cell depleted SCID mice. Daily oral treatment with M475271 inhibited the growth of subcutaneous tumors with PC-9 and A549 cells via inhibition of tumor cells proliferation, VEGF production and/or vascularization in the mice in a dose-dependent manner. In the metastasis model with A549 cells, the lung weight in the M475271 (50 mg/kg)-treated group was less than that of the control group, despite no difference in the number of metastatic nodules. Our results suggest that inhibition of tyrosine kinase Src by M475271 could reduce the growth, invasion and VEGF-mediated neovascularization of lung adenocarcinoma cells, resulting in inhibition of growth of subcutaneous tumors and lung metastasis. Therefore, a novel Src tyrosine kinase inhibitor, M475271, might be helpful for controlling the progression of human lung adenocarcinoma.     

Distinct roles for N‐Cadherin linked c‐Src and fyn kinases in lens development

Background: Src family tyrosine kinases (SFKs) are often coincidently expressed but few studies have dissected their individual functions in the same cell during development. Using the classical embryonic lens as our model, we investigated SFK signaling in the regulation of both differentiation initiation and morphogenesis, and the distinct functions of c‐Src and Fyn in these processes. Results: Blocking SFK activity with the highly specific inhibitor PP1 induced initiation of the lens differentiation program but blocked lens fiber cell elongation and organization into mini lens‐like structures called lentoids. These dichotomous roles for SFK signaling were discovered to reflect distinct functions of c‐Src and Fyn and their differentiation‐state‐specific recruitment to and action at N‐cadherin junctions. c‐Src was highly associated with the nascent N‐cadherin junctions of undifferentiated lens epithelial cells. Its siRNA knockdown promoted N‐cadherin junctional maturation, blocked proliferation, and induced lens cell differentiation. In contrast, Fyn was recruited to mature N‐cadherin junctions of differentiating lens cells and siRNA knockdown suppressed differentiation‐specific gene expression and blocked morphogenesis. Conclusions: Through inhibition of N‐cadherin junction maturation, c‐Src promotes lens epithelial cell proliferation and the maintenance of the lens epithelial cell undifferentiated state, while Fyn, signaling downstream of mature N‐cadherin junctions, promotes lens fiber cell morphogenesis. Developmental Dynamics 242:469–474, 2013. © 2013 Wiley Periodicals, Inc.     

Stimulation of extracellular signal-regulated kinases and proliferation in the human gastric cancer cells KATO-III by obestatin

Obestatin, the ghrelin-associated peptide, activates cell proliferation in the gastric cancer cell line KATO-III. The results showed that this peptide induced cell proliferation by mitogen-activated kinase kinase/extracellular signal-regulated kinases1/2 (ERK1/2) phosphorylation. A sequential analysis of the obestatin transmembrane signalling pathway indicated that the ERK1/2 activity is partially blocked after preincubation of the cells with pertussis toxin, as well as by wortmannin (an inhibitor of phosphoinositide 3-kinase (PI3K)), staurosporine (an inhibitor of protein kinase C (PKC)) and 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2, which inhibits the non receptor tyrosine kinase Src). Upon administration of obestatin, the intracellular levels of phospho-PKCepsilon- and theta-isoenzymes rise with similar time-courses, from which PKCepsilon appears to be the responsible for ERK1/2 response. Based on the experimental data, a signalling pathway involving the consecutive activation of G(i), PI3K, novel PKCepsilon and Src for ERK1/2 activation is proposed. These results point to a functionally active peptide that regulates proliferation of the gastric cancer cells KATO-III.     

CD137 ligand‐mediated reverse signals increase cell viability and cytokine expression in murine myeloid cells: Involvement of mTOR/p70S6 kinase and Akt

Cross‐linking of CD137 ligand (CD137L), a member of the TNF family, with recombinant CD137‐Fc (rCD137‐Fc) protein enhanced adherence of bone marrow‐derived macrophages, and increased the expression of ICAM‐1, IL‐1β, IL‐6, M‐CSF and phosphotyrosine proteins. In RAW264.7 cells, a murine myeloid cell line, rCD137‐Fc not only increased adherence but also cell multiplication, in a manner comparable to LPS or M‐CSF. In addition, it up‐regulated expression of IL‐1β, IL‐1 receptor antagonist, IL‐6, COX2, tenascin C, neuropeptide Y and M‐CSF mRNA. Neutralization of M‐CSF by incubating the RAW264.7 cells with anti‐M‐CSF mAb did not prevent the CD137L signal‐induced viability. Viability was blocked by PP2, an Src tyrosine kinase inhibitor, rapamycin, an mTOR inhibitor and LY294002, a PI3K inhibitor, but not by Wortmannin, another PI3K inhibitor. Cross‐linking of CD137L increased phosphorylation of Akt and p70S6 kinase. The latter was blocked by PP2, rapamycin or LY294002, but not by Wortmannin, whereas phosphorylation of Akt was blocked by LY294002 or Wortmannin. These findings demonstrate that reverse signals evoked by CD137L regulate immune functions in macrophages.     

Identification of ACA‐28, a 1′‐acetoxychavicol acetate analogue compound,as a novel modulator of ERK MAPK signaling,which preferentially kills human melanoma cells

The extracellular signal‐regulated kinase (ERK) signaling pathway is essential for cell proliferation and is frequently deregulated in human tumors such as melanoma. Melanoma remains incurable despite the use of conventional chemotherapy; consequently, development of new therapeutic agents for melanoma is highly desirable. Here, we carried out a chemical genetic screen using a fission yeast phenotypic assay and showed that ACA‐28, a synthetic derivative of 1′‐acetoxychavicol acetate (ACA), which is a natural ginger compound, effectively inhibited the growth of melanoma cancer cells wherein ERK MAPK signaling is hyperactivated due to mutations in the upstream activating regulators. ACA‐28 more potently inhibited the growth of melanoma cells than did the parental compound ACA. Importantly, the growth of normal human epidermal melanocytes (NHEM) was less affected by ACA‐28 at the same 50% inhibitory concentration. In addition, ACA‐28 specifically induced apoptosis in NIH/3T3 cells which were oncogenically transformed with human epidermal growth factor receptor‐2 (HER2/ErbB2), but not in the parental cells. Notably, the ACA‐28‐induced apoptosis in melanoma and HER2‐transformed cells was abrogated when ERK activation was blocked with a specific MEK inhibitor U0126. Consistently, ACA‐28 more strongly stimulated ERK phosphorylation in melanoma cells, as compared in NHEM. ACA‐28 might serve as a promising seed compound for melanoma treatment.     

Src family kinase potentiates the activity of nicotinic acetylcholine receptor in rat autonomic ganglion innervating urinary bladder

Src family kinases (SFKs), one of the tyrosine kinase groups, are primary regulators of signal transductions that control cellular functions such as cell proliferation, differentiation, survival, metabolism, and other important roles of the cell. One of the crucial functions of SFKs is to regulate the activities of various neuronal channels. In this study, we investigated the modulatory action of SFK on nicotinic acetylcholine receptors (nAChRs) expressed in rat major pelvic ganglion (MPG) neurons innervating the urinary bladder. PP1 and PP2 (5 μM), selective Src-kinase inhibitors, attenuated ACh-induced ionic currents and [Ca2+](i) transients in MPG neurons, whereas PP3, an inactive analogue, had no effect. Blocking the tyrosine kinase activity of Src kinase by pp60 c-src inhibitory peptide also reduced the ACh-induced currents. Conversely, sodium orthovanadate (200 μM), a tyrosine phosphatase inhibitor, significantly augmented the ACh-induced currents. In the kinase assay, the activities of SFKs in MPG neurons were also inhibited by PP2, but not by PP3. These data suggests that SFKs may have a facilitative role on the synaptic transmission in rat pelvic autonomic ganglion.     

PP2, a potent inhibitor of Src family kinases, protects against hippocampal CA1 pyramidal cell death after transient global brain ischemia

It has been indicated that Src family protein tyrosine kinases (SrcPTKs) potentiate N-methyl-D-aspartate (NMDA) receptor function by phosphorylating NR2A subunits and that postsynaptic density protein 95 (PSD-95) facilitates this regulation. In this paper, we define the role of SrcPTKs in delayed neuronal damage following transient brain ischemia and explore the underlying mechanisms involved in this event. Transient global brain ischemia was induced by the four-vessel occlusion method. A specific Src family kinase inhibitor PP2 (4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyramidine) and a PP2 negative control PP3 (4-amino-7-phenylpyrazolo[3,4-d]pyramidine) were infused into rat cerebroventricule 30 min before occlusion. Hematoxylin and eosine staining showed that the number of surviving pyramidal neurons in rat hippocampal CA1 subfield increased markedly in PP2-treated rats comparing to PP3-treated groups after 5 days of reperfusion following ischemia. Additionally, immunoprecipitation and immunoblot analysis revealed that preadministration of PP2, but not PP3, attenuated not only the increased tyrosine phosphorylation of NR2A but also the enhanced interactions among Src, NR2A and PSD-95 induced by ischemia/reperfusion. In conclusion, SrcPTKs promote binding of the kinases and their substrate NR2A attributed to the scaffolding effect of PSD-95 during transient brain ischemia and reperfusion, which are responsible for the elevation of NR2A tyrosine phosphorylation and consequent delayed neuronal cell death.     

Gab2 is phosphorylated on tyrosine upon interleukin-2/interleukin-15 stimulation in mycosis-fungoides-derived tumor T cells and associates inducibly with SHP-2 and Stat5a

Cutaneous T cell lymphomas (CTCLs) often show abnormal interleukin-2 (IL-2) receptor signaling. In this study, we investigated the role of Gab2, a recently identified adaptor molecule involved in IL-2 receptor signaling in CTCLs. We show that Gab2 was transiently phosphorylated by tyrosine in human mycosis fungoides (MF) tumor T cells upon IL-2 stimulation and that SHP2 as well as Stat5a associated inducibly with Gab2. IL-15, but not IL-4, also induced tyrosine phosphorylation of Gab2, suggesting that the IL-2 receptor beta-chain is important for IL-2-induced Gab2 phosphorylation. Preincubation of cells with the Src family kinase inhibitor, PP1, surprisingly increased the IL-2- and IL-15-induced tyrosine phosphorylation of Gab2, indicating that an Src family kinase member negatively regulates IL-2 receptor signaling in MF T cells. Thus, although Gab2 seems to function normally in MF T cells compared to normal T cells, Gab2 itself might be abnormally regulated by an Src family kinase.     

Endothelial Src kinase regulates membrane recycling from the lateral border recycling compartment during leukocyte transendothelial migration

When leukocytes cross endothelial cells during the inflammatory response, membrane from the recently described lateral border recycling compartment (LBRC) is selectively targeted around diapedesing leukocytes. This "targeted recycling" is critical for leukocyte transendothelial migration. Blocking homophilic PECAM interactions between leukocytes and endothelial cells blocks targeted recycling from the LBRC and blocks diapedesis. However, the cellular signaling pathways that trigger targeted recycling are not known. We show that targeted recycling from the LBRC is dependent on Src kinase. The selective Src kinase inhibitor PP2 blocked targeted recycling and blocked diapedesis by over 70%. However, Src kinase inhibition did not affect the structure or normal constitutive recycling of membrane from the LBRC in the absence of leukocytes. PECAM, a Src kinase substrate, traffics between the LBRC and the endothelial surface at the cell border. However, virtually all of the PECAM in the cell that was phosphorylated on tyrosine residues was found in the LBRC. These findings demonstrate that Src kinase activity is critical for the targeted recycling of membrane from the LBRC to the site of transendothelial migration and that the PECAM in the LBRC is qualitatively different from the PECAM on the surface of endothelial cells.     

Role of different protein tyrosine kinases in fMLP-induced neutrophil transmigration

Protein tyrosine phosphorylation is among the early signaling events in polymorphonuclear leukocyte (PMN) responses to chemoattractant stimulation. We previously showed that tyrosine phosphorylation might serve as the downstream signaling for the modulation of PMN transmigration by CD47. Here, we further investigated the role of various tyrosine kinases in PMN transmigration and identified the potential tyrosine kinases serving as CD47-mediated signaling downstream. We observed that PMN transmigration was significantly enhanced by Src family kinase inhibitors PP1 and PP2 as well as Syk tyrosine kinase inhibitor piceatannol, suggesting that these kinases have negative regulatory roles in PMN chemotaxis. In contrast, PMN chemotaxis was reduced by LFM-A13, an inhibitor of the Tec family tyrosine kinase Btk (Bruton's tyrosine kinase). LFM-A13 also dose-dependently inhibited N-formyl-Met-Leu-Phe (fMLP)-induced PMN intracellular [Ca2+] increase. Since LFM-A13 significantly enhanced PMN chemokinesis while other inhibitors had no effect, the inhibition of PMN chemotaxis by LFM-A13 might be due to the promotion of random cell migration. Among the other inhibitors we tested, AG126 significantly inhibited PMN transmigration while the MAP kinase inhibitors SB20358 and PD98059 showed an enhancing effect. No effect of herbimycin A, erbstatin analog, lavendustin A or AG490 on PMN transmigration was observed. Treatment with PP1, PP2 or piceatannol all partially reversed the delay of PMN transmigration caused by inhibitory anti-CD47 antibody. In summary, our results demonstrate distinct roles of different tyrosine kinases in regulating PMN chemotaxis and suggest Src and/or Syk kinases are likely involved in CD47-mediated downstream signaling.     

Key role of proline-rich tyrosine kinase 2 in interleukin-8 (CXCL8/IL-8)-mediated human neutrophil chemotaxis

The signalling pathways leading to CXCL8/IL-8-induced human neutrophil migration have not been fully characterized. The present study demonstrates that CXCL8 induces tyrosine phosphorylation as well as enzymatic activity of proline-rich tyrosine kinase 2 (Pyk2), a non-receptor protein tyrosine kinase (PTK), in human neutrophils. Induction of Pyk2 tyrosine phosphorylation by CXCL8 is regulated by Src PTK activation, whereas it is unaffected by phosphatidylinositol 3-kinase activation. Inhibition of Pyk2 activation by PP1, a Src PTK inhibitor, is paralleled by the inhibition of CXCL8-mediated neutrophil chemotaxis. Among CXCL8 receptors, Src protein tyrosine kinase activation selectively regulates CXCR1-mediated polymorphonuclear neutrophil (PMN) chemotaxis. Overexpression of PykM, the kinase-dead mutant of Pyk2, blocks CXCL8-induced chemotaxis of HL-60-derived PMN-like cells, thus pinpointing the key role of Pyk2 in CXCL8-induced chemotaxis.     

Antibody binding to cell surface amyloid precursor protein induces neuronal injury by deregulating the phosphorylation of focal adhesion signaling related proteins

The biological function of full-length amyloid-β protein precursor (APP), the precursor of Aβ, is not fully understood. Mounting studies reported that antibody binding to cell surface APP causes neuronal injury. However, the mechanism of cell surface APP mediating neuronal injury remains to be determined. Colocalization of APP with integrin on cell surface leads us to suppose that focal adhesion (FA) related mechanism is involved in surface APP-mediated neuronal injury. In the present study, results demonstrated that primary cultured neurons treated with antibody against APP-N-terminal not only caused neuronal injury and aberrant morphologic changes of neurite, but also induced reaction of FA proteins appearing an acute increase then decrease pattern. Moreover, the elevation of tyrosine phosphorylation of FA proteins including paxillin and focal adhesion kinase (FAK), and down-regulated expression of protein tyrosine phosphatase (PTP1B) induced by APP antibody were prevented by inhibitor of Src protein kinases 4-amino-5-(4-chlorophenyl)-7(t-butyl) pyrazol (3,4-D) pyramide (PP2) and G protein inhibitor pertussis toxin (PTX), implying that Src family kinase and G protein play roles in APP-induced FA signals. In addition, pretreatment with PTX and PP2 was able to suppress APP-antibody induced neuronal injury. Taken together, the results suggest a novel mechanism for APP mediating neuronal injury through deregulating FA signals.     

Stimulation of extracellular signal-regulated kinases and proliferation in the human gastric cancer cells KATO-III by obestatin

Obestatin, the ghrelin-associated peptide, activates cell proliferation in the gastric cancer cell line KATO-III. The results showed that this peptide induced cell proliferation by mitogen-activated kinase kinase/extracellular signal-regulated kinases1/2 (ERK1/2) phosphorylation. A sequential analysis of the obestatin transmembrane signalling pathway indicated that the ERK1/2 activity is partially blocked after preincubation of the cells with pertussis toxin, as well as by wortmannin (an inhibitor of phosphoinositide 3-kinase (PI3K)), staurosporine (an inhibitor of protein kinase C (PKC)) and 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2, which inhibits the non receptor tyrosine kinase Src). Upon administration of obestatin, the intracellular levels of phospho-PKCε- and θ-isoenzymes rise with similar time-courses, from which PKCε appears to be the responsible for ERK1/2 response. Based on the experimental data, a signalling pathway involving the consecutive activation of G_i, PI3K, novel PKCε and Src for ERK1/2 activation is proposed. These results point to a functionally active peptide that regulates proliferation of the gastric cancer cells KATO-III.     

Fyn kinase mediates cortical actin ring depolymerization required for mast cell migration in response to TGF‐β in mice

Transforming growth factor‐β (TGF‐β) is a potent mast cell (MC) chemoattractant able to modulate local inflammatory reactions. The molecular mechanism leading to TGF‐β‐directed MC migration is not fully described. Here we analyzed the role of the Src family protein kinase Fyn on the main TGF‐β‐induced cytoskeletal changes leading to MC migration. Utilizing bone marrow‐derived mast cells (BMMCs) from WT and Fyn‐deficient mice we found that BMMC migration to TGF‐β was impaired in the absence of the kinase. TGF‐β caused depolymerization of the cortical actin ring and changes on the phosphorylation of cofilin, LIMK and CAMKII only in WT cells. Defective cofilin activation and phosphorylation of regulatory proteins was detected in Fyn‐deficient BMMCs and this finding correlated with a lower activity of the catalytic subunit of the phosphatase PP2A. Diminished TGF‐β‐induced chemotaxis of Fyn‐deficient cells was also observed in an in vivo model of MC migration (bleomycin‐induced scleroderma). Our results show that Fyn kinase is an important positive effector of TGF‐β‐induced chemotaxis through the control of PP2A activity and this is relevant to pathological processes that are related to TGF‐β‐dependent mast cell migration.