Oncogenic KIT-induced aggressive systemic mastocytosis requires SHP2/PTPN11 phosphatase for disease progression in mice

Acquired mutations in KIT are driver mutations in systemic mastocytosis (SM). Here, we tested the role of SHP2/PTPN11 phosphatase in oncogenic KIT signaling using an aggressive SM mouse model. Stable knock-down (KD) of SHP2 led to impaired growth, colony formation, and increased rates of apoptosis in P815 cells. This correlated with defects in signaling to ERK/Bim, Btk, Lyn, and Stat5 pathways in P815-KD cells compared to non-targeting (NT). Retro-orbital injections of P815 NT cells in syngeneic DBA/2 mice resulted in rapid development of aggressive SM within 13-16 days characterized by splenomegaly, extramedullary hematopoiesis, and multifocal liver tumors. In contrast, mice injected with P815 SHP2 KD cells showed less disease burden, including normal spleen weight and cellularity, and significant reductions in mastocytoma cells in spleen, bone marrow, peripheral blood and liver compared to NT controls. Treatment of human mast cell leukemia HMC-1 cells or P815 cells with SHP2 inhibitor II-B08, resulted in reduced colony formation and cell viability. Combining II-B08 with multi-kinase inhibitor Dasatinib showed enhanced efficacy than either inhibitor alone in blocking cell growth pathways and cell viability. Taken together, these results identify SHP2 as a key effector of oncogenic KIT and a therapeutic target in aggressive SM.     

SHP2 介导IL-6 促进乳腺癌细胞侵袭作用机制的研究*

目的：探讨非受体型酪氨酸磷酸酶SHP 2 介导白细胞介素- 6（interleukin- 6 ,IL- 6）促进人乳腺癌细胞侵袭的作用,以及相应的分子机制。方法：利用外源性重组IL- 6 处理人乳腺癌细胞T 47D ,采用表达IL- 6 的慢病毒感染T 47D 细胞使其内源性表达IL- 6,观察细胞的形态学改变情况,分析细胞迁移和侵袭能力的变化。采用小RNA 干扰的方法下调IL- 6 信号通路中关键分子SHP 2 的表达,观察其表达下降对IL- 6 促进乳腺癌细胞侵袭能力的影响,同时采用Westernblot方法检测Erk1/ 2 磷酸化变化。结果：上调IL- 6 在乳腺癌细胞中的表达显著促进乳腺癌细胞的迁移和侵袭能力,且细胞发生由上皮形态向类成纤维细胞形态的变化,同时伴随着上皮标志性蛋白E-cadherin 表达下调和间质标志Vimentin 表达上调。下调SHP 2 的表达明显抑制IL- 6 诱导乳腺癌细胞的上皮间质转化（epithelialmesenchymaltransition,EMT ）和侵袭能力,同时伴随着细胞内Erk1/ 2 磷酸化水平的下降。结论：SHP 2 通过介导IL- 6 诱导的EMT 促进乳腺癌细胞的迁移和侵袭能力。     

Cross-talk between gastric cancer and hepatic stellate cells promotes invadopodia formation during liver metastasis

In gastric cancer (GC), the liver is a common organ for distant metastasis, and patients with gastric cancer with liver metastasis (GCLM) generally have poor prognosis. The mechanism of GCLM is unclear. Invadopodia are special membrane protrusions formed by tumor cells that can degrade the basement membrane and ECM. Herein, we investigated the role of invadopodia in GCLM. We found that the levels of invadopodia-associated proteins were significantly higher in liver metastasis than in the primary tumors of patients with GCLM. Furthermore, GC cells could activate hepatic stellate cells (HSCs) within the tumor microenvironment of liver metastases through the secretion of platelet-derived growth factor subunit B (PDGFB). Activated HSCs secreted hepatocyte growth factor (HGF), which activated the MET proto-oncogene, MET receptor of GC cells, thereby promoting invadopodia formation through the PI3K/AKT pathway and subsequently enhancing the invasion and metastasis of GC cells. Therefore, cross-talk between GC cells and HSCs by PDGFB/platelet derived growth factor receptor beta (PDGFRβ) and the HGF/MET axis might represent potential therapeutic targets to treat GCLM.     

Protein tyrosine phosphatase epsilon and Neu-induced mammary tumorigenesis

Aberrant regulation of the phosphorylation of proteins on tyrosine residues is a well-established cause of cancer. Protein tyrosine phosphatases (PTPs) share in the crucial function of maintaining appropriate levels of phosphorylation of cellular proteins, making them potentially key players in regulating the transformation process. The receptor-type tyrosine phosphatase Epsilon (RPTPɛ) participates in supporting the transformed phenotype of mammary tumor cells induced in vivo by the Neu tyrosine kinase. The phosphatase is overexpressed in mammary tumors induced in mice by a Neu transgene and expression of RPTPɛ in mouse mammary glands leads to massive hyperplasia and associated tumorigenesis. Furthermore, cells isolated from mammary tumors induced by Neu in mice genetically lacking RPTPɛ appear less transformed and proliferate less well than corresponding mammary tumor cells isolated from mice expressing the phosphatase. At the molecular level, RPTPɛ dephosphorylates and activates Src and the related kinases Yes and Fyn, and the activities of these kinases are significantly reduced in tumor cells lacking RPTPɛ. Restoring the activities of these kinases reveals that it is only the reduced activity of Src that causes the aberrant morphology and proliferation rate of tumor cells lacking RPTPɛ. RPTPɛ is primed to activate Src, and presumably related kinases, following its phosphorylation by Neu at Y695 within its C-terminus. This event is crucial in enabling RPTPɛ to activate Src, but appears not to affect the activity of RPTPɛ towards unrelated substrates. We conclude that a Neu-RPTPɛ-Src pathway exists in mouse mammary tumor cells, in which Neu phosphorylates RPTPɛ thereby driving the phosphatase to specifically activate Src family kinases and to assist in maintaining the transformed phenotype.     

CD73 facilitates invadopodia formation and boosts malignancy of head and neck squamous cell carcinoma via the MAPK signaling pathway

Elevated adenosine generated by CD73 (ecto‐5′‐nucleotidase; NT5E) could boost immunosuppressive responses and promote immune evasion in the tumor microenvironment. However, despite the immune response, CD73 could also promote tumor progression in a variety of cancers, and the nonimmunologic role and corresponding molecular mechanism of CD73 involved in head and neck squamous cell carcinoma (HNSCC) progression are not well characterized. Here, we demonstrated that CD73/NT5E is overexpressed in HNSCC tissues and predicts poor prognosis. Suppression of CD73 inhibited the proliferation, migration, and invasion of HNSCC cell lines (CAL27 and HN4) in vitro and in vivo. Gene set variation analysis (GSVA) and gene set enrichment analysis (GSEA) predicted that CD73 may be involved in invadopodia formation and MAPK signaling activation. As expected, knockdown of CD73 inhibited the MAPK signaling pathway, and the suppressive effect of CD73 knockdown on proliferation, migration, invasion, and invadopodia formation was reversed by a MAPK signaling activator. Our results suggest that CD73 could promote the proliferation, migration, invasion, and invadopodia formation of HNSCC via the MAPK signaling pathway and provide new mechanistic insights into the nonimmunological role of CD73 in HNSCC.     

Protein tyrosine phosphatase SHP-2: A proto-oncogene product that promotes Ras activation

SHP-2 is a cytoplasmic protein tyrosine phosphatase (PTP) that contains two Src homology 2 (SH2) domains. Although PTPs are generally considered to be negative regulators on the basis of their ability to oppose the effects of protein tyrosine kinases, SHP-2 is unusual in that it promotes the activation of the Ras-MAPK signaling pathway by receptors for various growth factors and cytokines. The molecular basis for the activation of SHP-2 is also unique: In the basal state, the NH₂-terminal SH2 domain of SHP-2 interacts with the PTP domain, resulting in autoinhibition of PTP activity; the binding of SHP-2 via its SH2 domains to tyrosine-phosphorylated growth factor receptors or docking proteins, however, results in disruption of this intramolecular interaction, leading to exposure of the PTP domain and catalytic activation. Indeed, SHP-2 proteins with artificial mutations in the NH₂-terminal SH2 domain have been shown to act as dominant active mutants in vitro . Such activating mutations of PTPN11 (human SHP-2 gene) were subsequently identified in individuals with Noonan syndrome, a human developmental disorder that is sometimes associated with juvenile myelomonocytic leukemia. Furthermore, somatic mutations of PTPN11 were found to be associated with pediatric leukemia. SHP-2 is also thought to participate in the development of other malignant disorders, but in a manner independent of such activating mutations. Biochemical and functional studies of SHP-2 and genetic analysis of PTPN11 in human disorders have thus converged to provide new insight into the pathogenesis of cancer as well as potential new targets for cancer treatment. ( Cancer Sci  2009; 100: 1786–1793)     

基于酪氨酸磷酸酶SHP2变构抑制剂的肿瘤靶向治疗

[摘要] 蛋白质酪氨酸磷酸化对细胞的生命活动至关重要,其调控异常与多种疾病的发生密切相关。在酪氨酸磷酸酶家族中,SHP2 是目前唯一被证实的原癌蛋白,参与调控多个癌症相关过程。其活化突变会导致白血病、黑色素瘤、乳腺癌及肺癌的发生。2016 年以来,随着高特异性、可口服的SHP2 新型变构抑制剂成功开发,靶向抑制SHP2 在抑制肿瘤生长以及改善肿瘤耐药性方面逐渐显现出了强大的临床应用潜力,提示SHP2 抑制剂有望成为首个靶向酪氨酸磷酸酶的抗肿瘤靶向药物。     

The tyrosine phosphatase PTPRO sensitizes colon cancer cells to anti-EGFR therapy through activation of SRC-mediated EGFR signaling

Inappropriate activation of epidermal growth factor receptor (EGFR) plays a causal role in many cancers including colon cancer. The activation of EGFR by phosphorylation is balanced by receptor kinase and protein tyrosine phosphatase activities. However, the mechanisms of negative EGFR regulation by tyrosine phosphatases remain largely unexplored. Our previous results indicate that protein tyrosine phosphatase receptor type O (PTPRO) is down-regulated in a subset of colorectal cancer (CRC) patients with a poor prognosis. Here we identified PTPRO as a phosphatase that negatively regulates SRC by directly dephosphorylating Y416 phosphorylation site. SRC activation triggered by PTPRO down-regulation induces phosphorylation of both EGFR at Y845 and the c-CBL ubiquitin ligase at Y731. Increased EGFR phosphorylation at Y845 promotes its receptor activity, whereas enhanced phosphorylation of c-CBL triggers its degradation promoting EGFR stability. Importantly, hyperactivation of SRC/EGFR signaling triggered by loss of PTPRO leads to high resistance of colon cancer to EGFR inhibitors. Our results not only highlight the PTPRO contribution in negative regulation of SRC/EGFR signaling but also suggest that tumors with low PTPRO expression may be therapeutically targetable by anti-SRC therapies.     

Protein tyrosine phosphatase PTPN13 negatively regulates Her2/ErbB2 malignant signaling

Deregulated Her2/ErbB2 receptor tyrosine kinase drives tumorigenesis and tumor progression in a variety of human tissues. Her2 transmits oncogenic signals through phosphorylation of its cytosolic domain. To study innate cellular mechanisms for containing Her2 oncogenic phosphorylation, a siRNA phosphatase library was screened for cellular phosphatase(s) that enhance phosphorylation in the signaling motif of Her2 after knockdown. We found that silencing protein tyrosine phosphatase PTPN13 significantly augmented growth factor-induced phosphorylation of the Her2 signaling domain and promoted the invasiveness of Her2-deregulated cancer cells. In addition, we discovered that growth factor-induced phosphorylation of PTPN13 was essential for the dephosphorylation of Her2 suggesting a negative feedback mechanism induced by growth factor to inhibit cellular Her2 activity through PTPN13. Importantly, we showed that PTPN13 mutations previously reported in human tumors significantly reduced the phosphatase activity of PTPN13, and consequently elevated the oncogenic potential of Her2 and the invasiveness of Her2-overexpressing human cancer cells. Taken together, these results suggest that cellular PTPN13 inhibits Her2 activity by dephosphorylating the signal domain of Her2 and plays a role in attenuating invasiveness and metastasis of Her2 overactive tumors.     

Protein tyrosine phosphatase activity as a diagnostic parameter in breast cancer

Summary Cellular phosphotyrosine levels are regulated by the balance between protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). It is supposed that this balance is disturbed in tumour cells, making the increased or altered activity of PTKs and PTPs likely hallmarks of tumour tissues. Indeed it could be shown that the PTK activity was increased in breast cancer in correlation with prognosis (Hennipmanet al., Cancer Res. 49, 516–522, 1989). In the present report we measured the PTP activities in breast cancer and normal breast tissues. An increase of approximately three- to four-fold was measured in the cytosolic tumour fractions compared to normal, whereas the solubilized membrane fraction PTP activity showed an increase in tumours of approximately 1.5-fold. Remarkably, the membrane PTP activity correlated with the presence of tumour positive axillary lymph nodes (p = 0.004), whereas the cytosolic PTP activity correlated with the mitotic index, a higher PTP activity occurring when the mitotic index was higher than 10 (p = 0.0004). These results indicate that membrane PTP activity may be considered as an index of metastatic potential, whereas cytosolic PTP activity may be a measure of the growth capacity of the tumour. The increase of PTP activity in breast cancers was confirmed by enzyme-histochemical studies. In frozen sections of tumours a strong to moderate activity was found in both tumour cells and interstitial cells. In the interstitium membrane activity was most pronounced, whereas in the tumour cells diffuse staining of the cytoplasm together with a clear membrane staining was demonstrated. Immunoblotting with anti-phosphotyrosine antibodies also reveals differences between the tumours and normal tissues, confirming the disturbance of the balance between protein tyrosyl phosphorylation and dephosphorylation in the tumour cells.     

SHP2在非小细胞肺癌中的表达及意义

背景与目的以往研究表明,异常的酪氨酸磷酸化与癌的发生密切相关,本研究旨在采用组织芯片技术结合免疫组化方法来研究蛋白酪氨酸磷酸酶SHP2在非小细胞肺癌(non-small cell lung cancer,NSCLC)中的表达及意义。方法80例NSCLC石蜡标本制成组织芯片,采用链菌素亲生物素-过氧化物酶法(SP)进行免疫组化检测。结果SHP2在NSCLC中的表达率为70.00%(56/80),其中鳞癌为72.5%(29/40),腺癌为67.50%(27/40);有无淋巴结转移的患者SHP2的阳性表达率分别为73.61%(53/72)和37.50%(3/8)(P<0.05);SHP2的表达与患者性别、年龄、肿块大小、病理类型、分化程度、临床分期间无统计学差异(P<0.05)。结论SHP2在NSCLC中有较高的表达率,且与淋巴结转移密切相关,提示肺癌的发生、发展可能与SHP2有关,SHP2可能是肺癌新的标志物及治疗靶点。     

Betulinic acid suppresses STAT3 activation pathway through induction of protein tyrosine phosphatase SHP‐1 in human multiple myeloma cells

STAT3 activation has been associated with survival, proliferation and invasion of various human cancers. Whether betulinic acid, a pentacyclic triterpene, can modulate the STAT3 pathway, was investigated in human multiple myeloma (MM) cells. We found that betulinic acid inhibited constitutive activation of STAT3, Src kinase, JAK1 and JAK2. Pervanadate reversed the betulinic acid‐induced downregulation of STAT3 activation, suggesting the involvement of a protein tyrosine phosphatase (PTP). Furthermore, betulinic acid induced the expression of the PTP SHP‐1 and silencing of the SHP‐1 gene abolished the ability of betulinic acid to inhibit STAT3 activation and rescued betulinic acid‐induced cell death. Betulinic acid also downregulated the expression of STAT3‐regulated gene products such as bcl‐xL, bcl‐2, cyclin D1 and survivin. This correlated with an increase in apoptosis as indicated by an increase in the sub‐G1 cell population and an increase in caspase‐3‐induced PARP cleavage. Consistent with these results, overexpression of constitutive active STAT3 significantly reduced the betulinic acid‐induced apoptosis. Betulinic acid also enhanced the apoptosis induced by thalidomide (from 10 to 55%) and bortezomib (from 5 to 70%) in MM cells. Overall, our results suggest that betulinic acid downregulates STAT3 activation through upregulation of SHP‐1, and this may have potential in sensitization of STAT3 overexpressing tumors to chemotherapeutic agents.     

Discs large homolog 5 decreases formation and function of invadopodia in human hepatocellular carcinoma via Girdin and Tks5

Invadopodium formation is a crucial early event of invasion and metastasis of hepatocellular carcinoma (HCC). However, the molecular mechanisms underlying regulation of invadopodia remain elusive. This study aimed to investigate the potential role of discs large homolog 5 (Dlg5) in invadopodium formation and function in HCC. We found that Dlg5 expression was significantly lower in human HCC tissues and cell lines than adjacent nontumor tissues and liver cells. Lower Dlg5 expression was associated with advanced stages of HCC, and poor overall and disease‐free survival of HCC patients. Dlg5‐silencing promoted epithelial–mesenchymal transition, invadopodium formation, gelatin degradation function, and invadopodium‐associated invasion of HepG2 cells. In contrast, Dlg5 overexpression inhibited epithelial–mesenchymal transition, functional invadopodium formation, and invasion of SK‐Hep1 cells. Both Girdin and Tks5, but not the Tks5 nonphosphorylatable mutant, were responsible for the enhanced invadopodium formation and invasion of Dlg5‐silenced HepG2 cells. Furthermore, Dlg5 interacted with Girdin and interfered with the interaction of Girdin and Tks5. Dlg5 silencing promoted Girdin and Tks5 phosphorylation, which was abrogated by Girdin silencing and rescued by inducing shRNA‐resistant Girdin expression. Moreover, Dlg5 overexpression significantly inhibited HCC intrahepatic and lung metastasis in vivo. Taken together, our data indicate that Dlg5 acts as a novel regulator of invadopodium‐associated invasion via Girdin and by interfering with the interaction between Girdin and Tks5, which might be important for Tks5 phosphorylation in HCC cells. Conceivably, Dlg5 may act as a new biomarker for prognosis of HCC patients.     

Targeting SHP2 sensitizes differentiated thyroid carcinoma to the MEK inhibitor

Pharmacologic targeting of components of the MAPK/ERK pathway in differentiated thyroid carcinoma (DTC) is often limited due to the development of adaptive resistance. However, the detailed mechanism of MEK inhibitor (MEKi) resistance is not fully understood. Here, MEKi-resistant models were constructed successfully, in which multiple receptor tyrosine kinases (RTKs) signaling pathways and Src-homology 2 domain-containing phosphatase 2 (SHP2) were activated in MEKi-resistant cells. Given the physiological role of SHP2 as the downstream target of many RTKs, we first found blockade of SHP2 enhanced the sensitivity to MEKi in constructed MEKi-resistant models. Interestingly, we also found that compared with MEKi treatment alone, MEKi in combination with an SHP2 inhibitor markedly suppressed the reactivation of the MEK/ERK pathway; thus, the addition of the SHP2 inhibitor significantly improved the antitumor effects of MEKi. The synergistic suppression of DTC upon treatment with both inhibitors was further confirmed in xenograft models and transgenic models. Thus, our data suggest that RTKs activation leads to reactivation of the MAPK pathway and resistance to MEKi in DTC, which is reversed by SHP2 blockade. As a novel active inhibitor of SHP2, SHP099 in combination with MEKi is a promising therapeutic approach for advanced DTC and MEKi-resistant one.     

FMNL2通过Rho信号通路促进胃癌细胞的侵袭和迁移

目的:研究同源形成素样蛋白2（FMNL2）是否通过Rho信号通路促进胃癌细胞的侵袭和迁移。方法:利用Oncomine数据库中的大数据分析FMNL2在胃癌及癌旁组织中的表达水平。运用实时定量聚合酶链反应（RT-PCR）和蛋白质印迹法（Western blot）检测胃癌细胞系中FMNL2 mRNA和蛋白的表达情况,使用shFMNL2质粒和空载质粒转染胃癌细胞系,并分为敲减组和对照组。采用 CCK8法、划痕实验、Transwell侵袭实验分析细胞的生物学功能,包括增殖、迁移及侵袭能力,利用Western blot方法检测两组细胞经Rho信号通路抑制剂Y27632处理后的E-cadherin、Vimentin及Rho信号通路相关蛋白的表达情况。结果:经生物信息学分析发现FMNL2在胃癌组织中高表达。同样FMNL2在胃癌细胞中表达水平升高。划痕实验和Transwell侵袭实验结果表明敲减组的迁移和侵袭能力显著下降。Western blot结果显示与对照组相比,E-cadherin在敲减组表达上调,Vimentin、RhoA、ROCK在敲减组表达下调。加入通路抑制剂Y27632后,EMT相关蛋白表达可被逆转。结论:下调FMNL2的表达可抑制胃癌细胞的侵袭迁移能力,并且可通过抑制Rho信号通路来实现。     

SHP2靶向治疗在抗肿瘤研究中的进展

免疫治疗和靶向治疗是目前抗肿瘤精准治疗的主要方式,但耐药性的出现导致一些肿瘤患者无法从临床治疗中获益。含Src同源2结构域的蛋白酪氨酸磷酸酶2（Src homology 2 domain-containing protein tyrosine phosphatase 2,SHP2）参与细胞内多种级联信号通路。基于底物特异性的SHP2在不同组织类型的背景下,发挥着促癌或者抑癌的重要作用。近几年随着多种新开发的SHP2变构抑制剂的出现,SHP2已成为一些肿瘤的潜在药物靶点。对一些临床前癌症模型的研究表明,SHP2变构抑制剂与其他靶向药和/或免疫检查点阻断剂联合使用是精准治疗耐药癌症的一种很有前景的策略。本文主要综述了近年来SHP2在肿瘤和免疫细胞中的作用机制、在临床前模型中的肿瘤靶向和免疫治疗研究以及SHP2抑制剂在临床试验中的研究进展。     

Protein tyrosine phosphatase mu regulates glioblastoma cell growth and survival in vivo

Glioblastoma multiforme (GBM) is the most lethal primary brain tumor. Extensive proliferation and dispersal of GBM tumor cells within the brain limits patient survival to approximately 1 year. Hence, there is a great need for the development of better means to treat GBM. Receptor protein tyrosine phosphatase (PTP)μ is proteolytically cleaved in GBM to yield fragments that promote dispersal of GBM cells. While normal brain tissue retains expression of full-length PTPμ, low-grade human astrocytoma samples have varying amounts of full-length PTPμ and cleaved PTPμ. In the highest-grade astrocytomas (i.e., GBM), PTPμ is completely proteolyzed into fragments. We demonstrate that short hairpin RNA mediated knockdown of full-length PTPμ and PTPμ fragments reduces glioma cell growth and survival in vitro. The reduction in growth and survival following PTPμ knockdown is enhanced when cells are grown in the absence of serum, suggesting that PTPμ may regulate autocrine signaling. Furthermore, we show for the first time that reduction of PTPμ protein expression decreases the growth and survival of glioma cells in vivo using mouse xenograft flank and i.c. tumor models. Inhibitors of PTPμ could be used to reduce the growth and survival of GBM cells in the brain, representing a promising therapeutic target for GBM.