Src Signaling Research Articles

Abstract LB012: Claudin-1 is a driver and therapeutic target for cholangiocarcinoma

Abstract Introduction: Cholangiocarcinoma (CCA) shows an alarming rise in incidence and mortality with unsatisfactory treatment options. Claudin-1 (CLDN1), a member of the tight junction family, is a transmembrane protein mediating cell stemness, plasticity and signaling. The functional role of CLDN1 as a therapeutic target for CCA is unknown. We have previously developed highly specific monoclonal antibodies (mAb) targeting exposed non-junctional CLDN1 exhibiting an excellent safety profile in non-human primates (Roehlen, Saviano et al. Science Translational Medicine 2022). Here, we aimed to explore the role of CLDN1 as an oncogenic driver and therapeutic target for CCA. Methods: Comprehensive CLDN1 expression analyses in patient tissues were performed to evaluate CLDN1 as a therapeutic target. Proof-of-concept studies using CLDN1 mAbs were performed in state-of-the-art mouse CDX and PDX models including models for advanced metastatic disease. Single-cell RNA sequencing and proteomics were applied to investigate tumor cell fate and signaling in vivo and ex vivo models. Results: Comprehensive analyses of CLDN1 protein and RNA expression in CCA patient tissues revealed a marked and significant upregulation of CLDN1 in CCA. Single-cell RNA sequencing of the CCA microenvironment revealed strong expression in tumor cells showing EMT, cell cycle and interferon response signature, uncovering CLDN1 as a therapeutic target. Targeting exposed CLDN1 by highly specific mAbs resulted in a significant and robust antitumoral effect in vivo across CDX and PDX models for intra- and extrahepatic CCA including advanced metastatic disease. Functional studies in cell-based models of CCA showed that CLDN1 mAbs markedly and significantly suppressed migration and invasion of tumor cells. Mechanistically, treatment with CLDN1 mAb suppressed Notch1, Src, and Hippo-YAP signaling - key signal transduction pathways implicated in CCA development and progression. Conclusion: Collectively, these results support an important functional role for CLDN1 in CCA pathogenesis and provide robust pre-clinical proof-of-concept for CLDN1-specific mAbs to treat CCA, setting the stage for its clinical development. Citation Format: Marion Muller, Zeina Nehme, Emilie Crouchet, Frank Jühling, Natascha Röhlen, Patrick Pessaux, Emanuele Felli, Lipika Goyal, Markus Meyer, Roberto Iacone, Alberto Toso, Luigi Manenti, Patrice Laquerriere, Aïna Venkatasamy, Nabeel Bardeesy, Catherine Schuster, Laurent Mailly, Thomas F. Baumert. Claudin-1 is a driver and therapeutic target for cholangiocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB012.

THY1 (CD90) Maintains the Adherens Junctions in Nasopharyngeal Carcinoma via Inhibition of SRC Activation

We had previously shown that THY1 (CD90) is a tumor suppressor in nasopharyngeal carcinoma (NPC) and that its down-regulation and loss of expression are associated with tumor metastasis, yet the mechanism leading to such effects remains unknown. In this study we show that tumor invasion could be suppressed by THY1 via adherens junction formation in a few NPC cell lines, and knockdown of THY1 would disrupt this cell-cell adhesion phenotype. Mechanistically, the activity of the SRC family kinase (SFK) member, SRC, and canonical Wnt signaling were dramatically reduced when THY1 was constitutively expressed. Previous studies by others have found that high levels of SRC activity in NPCs are associated with EMT and a poor prognosis. We hypothesized that THY1 can suppress tumor invasion in NPC via inhibition of SRC. By gene silencing of SRC, we found that the in vitro NPC cell invasion was significantly reduced and adherens junctions were restored. Through proteomic analysis, we identified that platelet-derived growth factor receptor β (PDGF-Rβ) and protein tyrosine phosphatase nonreceptor type 22 (PTPN22) are novel and potential binding partners of THY1, which were subsequently verified by co-immunoprecipitation (co-IP) analysis. The ligand of PDGF-Rβ (PDGF-BB) could highly induce SRC activation and NPC cell invasion, which could be almost completely suppressed by THY1 expression. On the other hand, the PTPN22 siRNA could enhance both the SRC activities and the cell invasion and could also disrupt the adherens junctions in the THY1-expressing NPC cells; the original THY1-induced phenotypes were reverted when the PTPN22 expression was reduced. Together, our results identified that PTPN22 is essential for THY1 to suppress cell invasion and SRC activity, maintain tight adherens junctions, and prevent NPC metastasis. These results suggested that PDGF-Rβ and SRC can be used as drug targets for suppressing NPC metastasis. Indeed, our in vivo assay using the SRC inhibitor KX2-391, clearly showed that inhibition of SRC signaling can prevent the metastasis of NPC, indicating that targeting SRC can be a promising approach to control the NPC progression.

Obacunone inhibits RANKL/M-CSF-mediated osteoclastogenesis by suppressing integrin- FAK-Src signaling.

Disrupted osteoblastogenesis or aberrant activation of osteoclastogenesis usually results in the break of bone homeostasis thus causing bone-associated diseases like osteoporosis. Obacunone, as a natural compound present in citrus fruits, has been demonstrated for various biological activities including anti-cancer and anti-inflammatory properties. However, the role of obacunone in regulating osteoclastogenesis has not been elucidated so far. Here, using in vitro cell models of RANKL (Receptor activator of nuclear factor-kB ligand) and M-CSF (Macrophage-colony-stimulating factor)-induced osteoclastogenesis, we showed that obacunone inhibited osteoclast differentiation in RAW264.7 cells and bone marrow macrophages (BMMs), as evidenced by obacunone dose-dependent reduction in numbers of osteoclasts and downregulated expressions of osteoclastogenesis-associated key genes. The anti-osteoclastic properties of obacunone were associated with downregulated expressions of Integrin α1 and attenuated activation of Focal adhesion kinase (FAK) and Steroid receptor coactivator (Src) signaling. Functional Integrin α1 blockade or FAK-Src inhibition suppressed RANKL/M-CSF-induced osteoclastogenesis, while Integrin α1 overexpression or FAK/Src activation partially attenuated obacunone's effects on suppressing RANKL/M-CSF-induced osteoclast differentiation. Furthermore, in vivo administration of obacunone displayed super therapeutic effects in attenuating ovariectomy-induced bone loss in mice, as indicated by decreases in serum biomarkers of bone turnover, restoring of femur fracture maximum force, and reversing of the worsened bone-related parameters in ovariectomized animals. Taken together, these findings demonstrate that obacunone has pharmacological activities to suppress osteoclast differentiation through modulating the Integrin-FAK-Src pathway, and suggest that obacunone is a therapeutic candidate for the treatment and prevention of bone diseases such as osteoporosis.

Sesamin Attenuates VEGFA-Induced Angiogenesis via Inhibition of Src and FAK Signaling in Chick Chorioallantoic Membrane Model and Human Endothelial EA.hy926 Cells.

Sesamin, a major phytochemical in sesame seeds and oil, has been reported to have effects on physiological and pathological angiogenesis in several studies. Nevertheless, the underlying mechanisms of sesamin's effect on angiogenesis are not understood well enough. This study aimed to investigate its effect on both physiological and pathological angiogenesis using the in vivo chick chorioallantoic membrane (CAM) model and the in vitro human endothelial cell line, EA.hy926, model. Sesamin inhibited the VEGFA-induced pathological angiogenesis significantly, although no effect was seen on angiogenesis without induction. It reduced the formation of vascular branches in the VEGFA-treated CAMs and also the proliferation and migration of EA.hy926 endothelial cells induced by VEGFA. Sesamin impeded the VEGF-mediated activation of Src and FAK signaling proteins, which may be responsible for sesamin-mediated reduction of pathological angiogenesis. Moreover, the effect of sesamin on the expressions of angiogenesis-related genes was then investigated and it was found that both mRNA and protein expressions of Notch1, the key pathway in vascular development, induced by VEGFA, were significantly reduced by sesamin. Our results altogether suggested that sesamin, by inhibiting pathological angiogenesis, has the potential to be employed in the prevention or treatment of diseases with over-angiogenesis, such as cancers.

Bufalin inhibits epithelial-mesenchymal transition and increases radiosensitivity of non-small cell lung cancer via inhibition of the Src signaling.

Epithelial-mesenchymal transition (EMT) is a biological process involved in tumor migration, invasion, and radiotherapy resistance. Bufalin can affect the proliferation, apoptosis and invasion of tumor cells by regulating multiple signaling pathways. Whether bufalin can increase radiosensitivity through EMT deserves further investigation. In this study, we investigated the effect of bufalin on the EMT and radiosensitivity of non-small cell lung cancer (NSCLC) and the underlying molecular mechanism. NSCLC cells were treated with bufalin (at a dose of 0-100 nM) or irradiated with 6 MV X-rays (4 Gy/min). The effects of bufalin on cell survival, cell cycle, radiosensitivity, cell migration, and invasion were detected. Western blot was used to analyze the gene expression changes of Src signaling in NSCLC cell induced by Bufalin. Bufalin significantly inhibited cell survival, migration, and invasion and induced G2/M arrest and apoptosis. Cells co-treated with bufalin and radiation manifested a higher inhibitory effect compared to those treated with radiation or bufalin alone. Furthermore, the levels of p-Src and p-STAT3 were considerably reduced following bufalin treatment. Interestingly, elevated p-Src and p-STAT3 were observed in cells treated with radiation. Bufalin inhibited radiation-induced p-Src and p-STAT3, whereas the knockdown of Src abrogated the effects of bufalin on cell migration, invasion, EMT, and radiosensitivity. Bufalin inhibits EMT and enhances radiosensitivity through targeting Src signaling in NSCLC.

Jiawei Taohe Chengqi Decoction attenuates hepatic fibrosis by preventing activation of HSCs through regulating Src/ERK/Smad3 signal pathway

Ethnopharmacological relevanceJiawei Taohe Chengqi Decoction (JTCD) is a Traditional Chinese Medicine (TCM) formula modified from Taohe Chengqi Decoction in the classic ancient literature of TCM “Treatise on Febrile Diseases”. Clinical and pharmacological studies have shown that JTCD has a therapeutic effect on hepatic encephalopathy, non-alcoholic fatty liver, cirrhotic ascites, and can alleviate acute liver injury in rats. Our previous studies confirmed that JTCD could alleviate hepatic fibrosis and activation of hepatic stellate cells (HSCs). However, its mechanism remains unclear. Aim of the studyThis study aimed to elucidate the mechanism of Src Signal on hepatic fibrosis and HSCs activation, and whether JTCD inhibited hepatic fibrosis and HSCs activation through affecting Src Signal. Materials and methodsIn vivo, sixty specific pathogen free male C57/BL6 mice were divided into following six groups: Control group, Model group, SARA group, JTCD low dose group, JTCD medium dose group and JTCD high dose group. Then we established a carbon tetrachloride (CCL4)-induced hepatic fibrosis mice model, each JTCD group was given the corresponding dose of JTCD by gavage, the SARA group was given Saracatinib and the control group was given saline, once a day for 4 consecutive weeks. UPLC-Q-TOF-MS analyzed chemical components of JTCD. Pathological examination including Hematoxylin and Eosin (H&E), Masson and Sirius red staining was used to observe the characteristic of hepatic fibrosis. Automatic biochemical analyzer detected the levels of alanine aminotransfease (ALT), and aspartate transaminase (AST) in serum. Western-blot and immunohistochemical staining (IHC) detected protein expression. In vitro, we used shRNA to knock down the expression of Src in immortalized human hepatic stellate cell line (LX-2), then intervened with ERK1/2 agonists/inhibitors and JTCD-containing serum after transforming growth factor β1 (TGF-β1) treatment. Immunofluorescence and western-blot detected protein expression. The migratory characteristic of HSCs was assessed by wound-healing assay. ResultsWe identified 135 chemical components in the water extract of JTCD, and the water extract of JTCD contains a variety of anti-hepatic fibrosis components. Compared to the model group, hepatic fibrosis performance was significantly improved, the serum levels of ALT and AST were significantly decreased in JTCD groups and SARA group, IHC staining and western blot results indicated that JTCD decreased the expressions of α-smooth muscle actin (α-SMA), phospho-Src (Tyr416), phospho-ERK1/2 and phospho-Smad3. In vitro, JTCD-containing serum could significantly decrease the protein expressions of α-SMA, phospho-Src (Tyr416), phospho-ERK1/2 and phospho-Smad3 according to the results of western-blot and immunofluorescence, in addition, JTCD-containing serum inhibited the mobility and activation of LX-2. What's more, after intervening with Src-shRNA, ERK1/2 agonists/inhibitors and JTCD-containing serum, the western-blot results showed that Src/ERK/Smad3 signal has an important role in hepatic fibrosis and HSCs, and JTCD attenuates hepatic fibrosis by preventing activation of HSCs through regulating Src/ERK/Smad3 signal pathway. ConclusionsThe results showed that Src kinase promoted hepatic fibrosis and HSCs activation through the ERK/Smad3 signal pathway. More importantly, the mechanism by which JTCD attenuated hepatic fibrosis and HSCs activation was by inhibiting the Src/ERK/Smad3 signal pathway.

Intracellular and extracellular moesins differentially regulate Src activity and β-catenin translocation to the nucleus in breast cancer cells

It is increasingly recognized that a single protein can have multiple, sometimes paradoxical, roles in cell functions as well as pathological conditions depending on its cellular locations. Here we report that moesins (MSNs) in the intracellular and extracellular domains present opposing roles in pro-tumorigenic signaling in breast cancer cells. Using live cell imaging with fluorescence resonance energy transfer (FRET)- and green fluorescent protein (GFP)-based biosensors, we investigated the molecular mechanism underlying the cellular location-dependent effect of MSN on Src and β-catenin signaling in MDA-MB-231 breast cancer cells. Inhibition of intracellular MSN decreased the activities of Src and FAK, whereas overexpression of intracellular MSN increased them. By contrast, extracellular MSN decreased the activities of Src, FAK, and RhoA, as well as β-catenin translocation to the nucleus. Consistently, Western blotting and MTT-based analysis showed that overexpression of intracellular MSN elevated the expression of oncogenic genes, such as p-Src, β-catenin, Lrp5, MMP9, Runx2, and Snail, as well as cell viability, whereas extracellular MSN suppressed them. Conditioned medium derived from MSN-overexpressing mesenchymal stem cells or osteocytes showed the anti-tumor effects by inhibiting the Src activity and β-catenin translocation to the nucleus as well as the activities of FAK and RhoA and MTT-based cell viability. Conditioned medium derived from MSN-inhibited cells increased the Src activity, but it did not affect the activities of FAK and RhoA. Silencing CD44 and/or FN1 in MDA-MB-231 cells blocked the suppression of Src activity and β-catenin accumulation in the nucleus by extracellular MSN. Collectively, the results suggest that cellular location-specific MSN is a strong regulator of Src and β-catenin signaling in breast cancer cells, and that extracellular MSN exerts tumor-suppressive effects via its interaction with CD44 and FN1.

The type II TGF-β receptor phosphorylates Tyr182 in the type I receptor to activate downstream Src signaling.

Transforming growth factor-β (TGF-β) signaling has important roles during embryonic development and in tissue homeostasis. TGF-β ligands exert cellular effects by binding to type I (TβRI) and type II (TβRII) receptors and inducing both SMAD-dependent and SMAD-independent intracellular signaling pathways, the latter of which includes the activation of the tyrosine kinase Src. We investigated the mechanism by which TGF-β stimulation activates Src in human and mouse cells. Before TGF-β stimulation, inactive Src was complexed with TβRII. Upon TGF-β1 stimulation, TβRII associated with and phosphorylated TβRI at Tyr182. Binding of Src to TβRI involved the interaction of the Src SH2 domain with phosphorylated Tyr182 and the interaction of the Src SH3 domain with a proline-rich region in TβRI and led to the activation of Src kinase activity and Src autophosphorylation. TGF-β1-induced Src activation required the kinase activities of TβRII and Src but not that of TβRI. Activated Src also phosphorylated TβRI on several tyrosine residues, which may stabilize the binding of Src to the receptor. Src activation was required for the ability of TGF-β to induce fibronectin production and migration in human breast carcinoma cells and to induce α-smooth muscle actin and actin reorganization in mouse fibroblasts. Thus, TGF-β induces Src activation by stimulating a direct interaction with TβRI that depends on tyrosine phosphorylation of TβRI by TβRII.

Tirbanibulin for Actinic Keratosis: Insights into the Mechanism of Action.

Actinic keratosis (AK) is a common pre-neoplastic skin lesion constituted by uncontrolled proliferation of atypical keratinocytes that may evolve to squamous cell carcinoma. With global prevalence increasing, AK is expected to be the most common carcinoma of the skin. Tirbanibulin is a reversible tubulin polymerization inhibitor with potent anti-proliferative and anti-tumoral effects. In-vivo and in-vitro studies have shown that tirbanibulin significantly inhibits cell proliferation, tumor growth and downregulates Src signaling with no overt toxicity. Early phase and Phase III trials have shown high lesion clearance, compliance, and few side effects of once daily tirbanibulin treatment. This review discusses tirbanibulin anti-cancer activity, focusing on tubulin polymerization and Src signaling inhibitory effects, highlighting relevant literature and novel preclinical results from the ATNXUS-KX01-001 study. Furthermore, we address the relevant findings obtained in recent clinical trials to evaluate the safety, efficacy, pharmacokinetics, clearance efficacy, and side effects of the 1% tirbanibulin ointment applied once daily. In summary, we highlight preclinical and clinical evidence on the use of tirbanibulin as an effective and safe treatment option for AK.

Focal adhesion kinase signaling is necessary for the hydrogen sulfide-enhanced proliferation, migration and invasion of HTR8/SVneo human trophoblasts

Objective: Hydrogen sulfide (H2S) has been elucidated that it promotes migration and invasion in human placenta trophoblasts. However, the signaling pathway underlying H2S-based regulation of trophoblasts remains unknown. Hence, we investigated the potential effect of sodium hydrosulfide (NaHS), an exogenous H2S donor, on extravillous trophoblasts. Methods: The Cell Counting Kit-8 was used to detect the proliferative activity of trophoblasts and to screen the optimal concentration of NaHS. The migration and invasion of HTR8/SVneo cells were measured by Transwell assays. Gene expression was determined by quantitative real-time PCR analysis. Protein expression was determined by western blot. Results: We found that NaHS could promote the proliferation, migration, and invasion of HTR8/SVneo cells. The phosphorylation of focal adhesion kinase (FAK), Src, and extracellular signal-regulated kinase (ERK) were activated by NaHS. Moreover, NaHS also upregulated the expression of matrix metalloproteinase-2(MMP-2) and MMP-9, downregulated the expression of E-cadherin in HTR8/SVneo cells. The application of NaHS could increase the expression of cystathionine-β-synthase. Conclusion: Both FAK–Src signaling and the upstream signaling cascade of ERK activation play a significant important role in NaHS-induced proliferation, migration, and invasion via upregulating activity of MMP-2, MMP-9, and downregulating E-cadherin in HTR8/SVneo cells. These novel findings may provide a strong foundation for the clinical application of H2S donor drugs.

First quantitative dosages: Strong correlations between non-5-HT2Rs serotonin receptors on normal human heart valves.

Although critical in animal and human development and pathology, a measurement of the quantitative expression of 5-HTR serotonin receptors on animal or human valvular tissues has never been performed. Quantification of the most frequent 5-HTRs reported as being present in human peripheral tissue was performed using radiolabeled agonists/antagonists. A membrane protein extract from normal human valves (aortic/mitral/tricuspid and some pulmonary) and associated diseased left myocardium, all unusable in clinics, were obtained from the Homograft bank. We analyzed 5-HT1AR/5-HT1B/DR/5-HT2AR/5-HT2BR/5-HT 2CR/5-HT4R/5-HT7R from 28 hearts. We confirmed the presence of tissue and measured the quantitative content for respective proteins in femtomol/mg of protein extracts: for 5-HT2AR (35.9+/-0.7), 5-HT2BR (28.8+/-1.3) but also a newly observed and robust expression for 5-HT4R (38+/-4.2). We identified one, 5-HT1ARs (4.9+/-0.3), and the possible expression, but at a very low level, of previously reported 5-HT1B/DRs (1.3+/-0.5) as well as the new 5-HT7Rs (3.5+/0.1) and 5-HT2CRs (1.2+/-0.1). Interestingly, by using univariate analysis, we were able to observe many correlations between the different 5-HTR levels of expression especially between 5-HT1AR/5-HT1B/DR and also between 5-HT4R/5-HT7R, but none were observed between 5-HT2AR and 5-HT2BR. Using multivariate analyses for a specific 5-HTR level of expression, after adjustment for implantation sites and other 5-HTRs, we found that 5-HT1AR was correlated with 5-HT1B/DR;5-HT4R with 5-HT7R and 5-HT1AR;5-HT2BR with 5-HT2AR only. For 5-HT2C, no correlation was observed. 5-HT2AR/5-HT2BR and 5-HT4R were all observed to have a high and equal level of expression on human valves, but that of 5-HT1AR was more limited. Since these non-5-HT2Rs are coupled with different G-proteins, with specific signaling, theoretically they may control the main 5-HT2R signaling (i.e., PLC/DAG-PKC-ERK/Ras/Src signaling) involved in valvular fibrosis and degeneration.

Proteomic time course of breast cancer cells highlights enhanced sensitivity to Stat3 and Src inhibitors prior to endocrine resistance development

To prevent the development of endocrine-resistant breast cancer, additional targeted therapies are increasingly being trialled in combination with endocrine therapy. The molecular mechanisms facilitating cancer cell survival during endocrine treatment remain unknown but could help direct selection of additional targeted therapies. We present a novel proteomic timecourse dataset, profiling potential drug targets in a population of MCF7 cells during 1 year of tamoxifen treatment. Reverse phase protein arrays profiled >70 proteins across 30 timepoints. A biphasic response to tamoxifen was evident, which coincided with changes in growth rate. Tamoxifen strongly impeded cell growth for the first 160 days, followed by gradual growth recovery and eventual resistance development. The growth-impeded phase was distinguished by the phosphorylation of Stat3 (y705) and Src (y527). Tumour tissue from patients treated with neo-adjuvant endocrine therapy (<4 months) also displayed increased Stat3 and Src signalling. Inhibitors of Stat3 (napabucasin) and Src (dasatinib), were effective at killing tamoxifen-treated MCF7 and T47D cells. Sensitivity to both drugs was significantly enhanced once tamoxifen had induced the growth-impeded phase. This novel proteomic resource identifies key mechanisms enabling cell survival during tamoxifen treatment. It provides valuable insight into potential drug combinations and timing that may prevent the development of endocrine resistance.

Combined high NEDD9 expression and E-cadherin loss correlate with poor clinical outcome in gastric cancer.

Neural precursor cell expressed developmentally downregulated 9 (NEDD9) is a member of the Cas family. Previous studies have revealed that NEDD9 coordinates the focal adhesion kinase and Src signaling cascades that are involved in integrin-dependent adhesion and migration, invasion, cell apoptosis and life cycle, and survival, which may play a role in epithelial-mesenchymal transformation. The aim of this study was to analyze the expression of NEDD9 and E-cadherin in gastric cancer (GC) and evaluate their clinical significance. NEDD9 and E-cadherin expression was analyzed with immunohistochemistry using tissue microarray technique in 435 GC patients who underwent gastrectomy. The NEDD9 expression level was defined by the combination score, which was determined by multiplying the staining intensity score and the proportion score (≥5; NEDD9-high, <5; NEDD9-low). E-cadherin loss was defined as a total loss of staining. The clinicopathologic parameters, overall survival, and disease-free survival rates were analyzed according to the NEDD9 and E-cadherin expression status. The combined NEDD9 and E-cadherin expression status correlated with lymphatic invasion (P=0.001), vascular invasion (P=0.020), and T stage (P=0.001). Combined high NEDD9 expression and loss of E-cadherin expression status had a worse overall survival rate (P<0.001) and served as a poor prognostic factor (Hazard ratio 2.49, 95% CI 1.25-5, P=0.01). Immunohistochemical staining for NEDD9 and E-cadherin may function as a candidate prognostic marker for gastric cancer in everyday practice, especially when applied in combination.

57 (PB047) - Regulation of BIM by cooperative Src and MAPK signaling

Background: Thyroid cancer is the most common endocrine malignancy with poor survival rates for patients with advanced and anaplastic thyroid cancer due to lack of effective therapies. We have previously demonstrated that combined Src and MAPK inhibition results in synergistic inhibition of growth in vitro and in vivo, and increased apoptosis in BRAF- and RAS- mutant cells, while PIK3CA- mutants are resistant. Using a proteomics approach, here we show that the pro-apoptotic protein, BIM, is increased in cells that are sensitive to combined Src and MAPK inhibition compared to cells that are resistant.

The microtubule network enables Src kinase interaction with the Na,K-ATPase to generate Ca2+ flashes in smooth muscle cells.

Background: Several local Ca2+ events are characterized in smooth muscle cells. We have previously shown that an inhibitor of the Na,K-ATPase, ouabain induces spatially restricted intracellular Ca2+ transients near the plasma membrane, and suggested the importance of this signaling for regulation of intercellular coupling and smooth muscle cell contraction. The mechanism behind these Na,K-ATPase-dependent “Ca2+ flashes” remains to be elucidated. In addition to its conventional ion transport function, the Na,K-ATPase is proposed to contribute to intracellular pathways, including Src kinase activation. The microtubule network is important for intracellular signaling, but its role in the Na,K-ATPase-Src kinase interaction is not known. We hypothesized the microtubule network was responsible for maintaining the Na,K-ATPase-Src kinase interaction, which enables Ca2+ flashes. Methods: We characterized Ca2+ flashes in cultured smooth muscle cells, A7r5, and freshly isolated smooth muscle cells from rat mesenteric artery. Cells were loaded with Ca2+-sensitive fluorescent dyes, Calcium Green-1/AM and Fura Red/AM, for ratiometric measurements of intracellular Ca2+. The Na,K-ATPase α2 isoform was knocked down with siRNA and the microtubule network was disrupted with nocodazole. An involvement of the Src signaling was tested pharmacologically and with Western blot. Protein interactions were validated with proximity ligation assays. Results: The Ca2+ flashes were induced by micromolar concentrations of ouabain. Knockdown of the α2 isoform Na,K-ATPase abolished Ca2+ flashes, as did inhibition of tyrosine phosphorylation with genistein and PP2, and the inhibitor of the Na,K-ATPase-dependent Src activation, pNaKtide. Ouabain-induced Ca2+ flashes were associated with Src kinase activation by phosphorylation. The α2 isoform Na,K-ATPase and Src kinase colocalized in the cells. Disruption of microtubule with nocodazole inhibited Ca2+ flashes, reduced Na,K-ATPase/Src interaction and Src activation. Conclusion: We demonstrate that the Na,K-ATPase-dependent Ca2+ flashes in smooth muscle cells require an interaction between the α2 isoform Na, K-ATPase and Src kinase, which is maintained by the microtubule network.

Electroacupuncture attenuates ischemic injury after stroke and promotes angiogenesis via activation of EPO mediated Src and VEGF signaling pathways.

Although electroacupuncture (EA) has been shown to be effective in the treatment of stroke, its mechanisms of action remain undefined. This study explored the therapeutic effects of EA in rats with cerebral ischemia-reperfusion injury (CIRI) and evaluated its possible mechanisms in promoting angiogenesis. To evaluate the effect of EA, we used 2, 3, 5-Triphenyl-2H-Tetrazolium Chloride (TTC) staining and behavior score to calculate the cerebral infarct volume and neurological deficit score after CIRI. Western blot (WB) analysis was employed to evaluate the expression of cluster of differentiation 34 (CD34), erythropoietin (EPO), vascular endothelial growth factor (VEGF) and phospho-Src (p-Src) in the brain of the rats with CIRI. On the other hand, we established an oxygen-glucose deprivation/reoxygenation (OGD/R) injury model using brain microvascular endothelial cells (BMECs), and analyzed cell viability and expression of VEGF or p-Src using cell counting kit-8 (CCK-8) and WB, respectively. Our data showed that EA at the GV26 acupoint could significantly promote the expression of CD34, EPO, VEGF and p-Src in CIRI rats. Our CCK-8 results demonstrated that intervention with recombinant EPO and VEGF proteins remarkably improved the viability of BMECs after OGD/R, while a Src inhibitor, PP1, reversed this phenotype. The WB results showed that the recombinant EPO protein increased the expression of VEGF and p-Src, which was significantly inhibited by PP1. Taken together, our findings showed that EA at the GV26 acupoint can significantly attenuate ischemic injury after stroke and promote angiogenesis via activation of EPO-mediated Src and VEGF signaling pathways. Besides, the upregulation of VEGF may also be associated with the activation of Src by EPO.

KC-180-2 Exerts Anti-SCLC Effects via Dual Inhibition of Tubulin Polymerization and Src Signaling.

In this study, a series of N-benzyl-2-(5-phenylpyridin-2-yl) acetamide-based derivatives were successfully designed and synthesized as anti-cancer agents. KC-180-2 was screened as a potentially leading compound with dual mechanisms of action: Src signaling and tubulin polymerization inhibition. It efficiently suppressed the proliferation of five cancer cell lines (MDA-MB-231, H446, SKOV-3, HepG2, and HT29), with IC50 values ranging from 5 to 188 nM, especially small-cell lung cancer (SCLC) cells (IC50, 5 nM). Correspondingly, it exerted a significant therapeutic effect on the H446 small-cell lung cancer xenograft model, significantly reducing the volume of tumors without obvious toxicity. Mechanistically, this compound significantly inhibited the polymerization of purified tubulin in vitro, inducing G2/M cell cycle arrest and binding to the kinase catalytic domain of the Src protein, which reduced the phosphorylation of Src. Thus, KC-180-2 is a potential lead compound for the further development of a new anti-tumor drug against SCLC.

Plectin promotes tumor formation by B16 mouse melanoma cells via regulation of Rous sarcoma oncogene activity

BackgroundMelanoma is a malignant tumor characterized by high proliferation and aggressive metastasis. To address the molecular mechanisms of the proto-oncogene, Rous sarcoma oncogene (Src), which is highly activated and promotes cell proliferation, migration, adhesion, and metastasis in melanoma. Plectin, a cytoskeletal protein, has recently been identified as a Src-binding protein that regulates Src activity in osteoclasts. Plectin is a candidate biomarker of certain tumors because of its high expression and the target of anti-tumor reagents such as ruthenium pyridinecarbothioamide. The molecular mechanisms by which plectin affects melanoma is still unclear. In this study, we examined the role of plectin in melanoma tumor formation.MethodsWe used CRISPR/Cas9 gene editing to knock-out plectin in B16 mouse melanoma cells. Protein levels of plectin and Src activity were examined by western blotting analysis. In vivo tumor formation was assessed by subcutaneous injection of B16 cells into nude mice and histological analysis performed after 2 weeks by Hematoxylin-Eosin (H&E) staining. Cell proliferation was evaluated by direct cell count, cell counting kit-8 assays, cyclin D1 mRNA expression and Ki-67 immunostaining. Cell aggregation and adhesion were examined by spheroid formation, dispase-based dissociation assay and cell adhesion assays.ResultsIn in vivo tumor formation assays, depletion of plectin resulted in low-density tumors with large intercellular spaces. In vitro experiments revealed that plectin-deficient B16 cells exhibit reduced cell proliferation and reduced cell-to-cell adhesion. Since Src activity is reduced in plectin-deficient melanomas, we examined the relationship between plectin and Src signaling. Src overexpression in plectin knockout B16 cells rescued cell proliferation and improved cell-to-cell adhesion and cell to extracellular matrix adhesion.ConclusionThese results suggest that plectin plays critical roles in tumor formation by promoting cell proliferation and cell-to-cell adhesion through Src signaling activity in melanoma cells.

Platelets and tyrosine kinase inhibitors: clinical features, mechanisms of action, and effects on physiology.

Tyrosine kinase inhibitors (TKIs) have emerged as a promising class of target-directed, small molecule inhibitors used to treat hematologic malignancies, inflammatory diseases, and autoimmune disorders. Recently, TKIs have also gained interest as potential antiplatelet-directed therapeutics that could be leveraged to reduce pathologic thrombus formation and atherothrombotic complications, while minimally affecting platelet hemostatic function. This review provides a mechanistic overview and summarizes the known effects of tyrosine kinase inhibitors on platelet signaling and function, detailing prominent platelet signaling pathways downstream of the glycoprotein VI (GPVI) receptor, integrin αIIbβ3, and G protein-coupled receptors (GPCRs). This review focuses on mechanistic as well as clinically relevant and emerging TKIs targeting major families of tyrosine kinases including but not limited to Bruton's tyrosine kinase (BTK), spleen tyrosine kinase (Syk), Src family kinases (SFKs), Janus kinases (JAK), and signal transducers and activators of transcription (STAT) and evaluates their effects on platelet aggregation and adhesion, granule secretion, receptor expression and activation, and protein phosphorylation events. In summation, this review highlights current advances and knowledge on the effects of select TKIs on platelet biology and furthers insight on signaling pathways that may represent novel druggable targets coupled to specific platelet functional responses.

Estrogen receptor variant ER-α36 facilitates estrogen signaling via EGFR in glioblastoma.

Glioblastoma (GBM) is a deadly and common primary brain tumor. Poor prognosis is linked to high proliferation and cell heterogeneity. Sex differences may play a role in patient outcome. Previous studies showed that ER-α36, a variant of the estrogen receptor (ER), mediated non-genomic estrogen signaling and is highly expressed in many ER-negative malignant tumors. ER-α36 also associates with epidermal growth factor receptor(EGFR). The primary purpose of this study is to investigate the cross talk between ER-α36 and EGFR in estrogen-mediated GBM cell proliferation. Here, we showed that ER-α36 was highly expressed and confirmed that ER-α36 co-labels with EGFR in human GBM samples using immunohistochemical techniques. We also investigated the mechanisms of estrogen-induced proliferation in ER-α-negative cell lines. We found that GBM cells showed varying responsive to mitogenic estrogen signaling which correlated with ER-α36 expression, and knockdown of ER-α36 diminished the response. Exposure to estrogen also caused upregulation of cyclin protein expression in vitro. We also found that low concentration of estrogen promoted SRC-Y-416 and inhibited SRC-Y-527 phosphorylation, corresponding with activated SRC signaling. Inhibiting SRC or EGFR abolished estrogen-induced mitogenic signaling, including cyclin expression and MAPK phosphorylation. Cumulatively, our results demonstrate that ER-α36 promotes non-genomic estrogen signaling via the EGFR/SRC/MAPK pathway in GBM. This may be important for the treatment of ER-α-negative GBMs that retain high level of ER-α36, since estrogen may be a viable therapeutic target for these patients.