Functions of Shp2 in cancer

Shp-2 is critical for ERK and metabolic engagement downstream of IL-15 receptor in NK cells

The phosphatase Shp-2 was implicated in NK cell development and functions due to its interaction with NK inhibitory receptors, but its exact role in NK cells is still unclear. Here we show, using mice conditionally deficient for Shp-2 in the NK lineage, that NK cell development and responsiveness are largely unaffected. Instead, we find that Shp-2 serves mainly to enforce NK cell responses to activation by IL-15 and IL-2. Shp-2-deficient NK cells have reduced proliferation and survival when treated with high dose IL-15 or IL-2. Mechanistically, Shp-2 deficiency hampers acute IL-15 stimulation-induced raise in glycolytic and respiration rates, and causes a dramatic defect in ERK activation. Moreover, inhibition of the ERK and mTOR cascades largely phenocopies the defect observed in the absence of Shp-2. Together, our data reveal a critical function of Shp-2 as a molecular nexus bridging acute IL-15 signaling with downstream metabolic burst and NK cell expansion.

Protein Phosphatases-A Touchy Enemy in the Battle Against Glioblastomas: A Review

Glioblastoma (GBM) is the most common malignant tumor arising from brain parenchyma. Although many efforts have been made to develop therapies for GBM, the prognosis still remains poor, mainly because of the difficulty in total resection of the tumor mass from brain tissue and the resistance of the residual tumor against standard chemoradiotherapy. Therefore, novel adjuvant therapies are urgently needed. Recent genome-wide analyses of GBM cases have clarified molecular signaling mechanisms underlying GBM biology. However, results of clinical trials targeting phosphorylation-mediated signaling have been unsatisfactory to date. Protein phosphatases are enzymes that antagonize phosphorylation signaling by dephosphorylating phosphorylated signaling molecules. Recently, the critical roles of phosphatases in the regulation of oncogenic signaling in malignant tumor cells have been reported, and tumorigenic roles of deregulated phosphatases have been demonstrated in GBM. However, a detailed mechanism underlying phosphatase-mediated signaling transduction in the regulation of GBM has not been elucidated, and such information is necessary to apply phosphatases as a therapeutic target for GBM. This review highlights and summarizes the phosphatases that have crucial roles in the regulation of oncogenic signaling in GBM cells.

Association of nuclear localization of SHP2 and YAP1 with unfavorable prognosis in non-small cell lung cancer

Src homology region 2 (SH2)-containing protein tyrosine phosphatase 2 (SHP2) is ubiquitously expressed in cytoplasmic localization, which in turn confers tumor malignancy and poor prognosis in various human cancers. YAP1 interacts with SHP2 to promote translocation of SHP2 to nucleus, which consequently promotes Wnt target activation. However, the oncogenic role of the nuclear localization of SHP2 in human cancers remains unclear. We hypothesized that nuclear SHP2 localization, in combination with nuclear YAP1 expression, could be associated with poor overall survival (OS) and relapse free survival (RFS) due to an increase in cyclin D1 and c-Myc mRNA expression following activation of Wnt/ß-catenin signaling. Immunohistochemical analysis of SHP2 and YAP1 protein expression in 102 tumors resected from patients with NSCLC revealed that nuclear SHP2 expression was well correlated with nuclear YAP1 expression (P < 0.001). Evaluation of cyclin D1 and c-Myc mRNA levels by the real-time reverse-phase polymerase chain reaction (RT-PCR) revealed that patients with high cyclin D1 and high c-Myc mRNA expressing tumors more commonly showed high nuclear YAP1 and high nuclear SHP2 (high/high) rather than the high/low, low/high, or low/low combinations (P < 0.001 for cyclin D1 and c-Myc). Kaplan-Meier and Cox-regression models showed OS and RFS to be poorer in patients in the high/high subgroup than in the low/low subgroup (OS: HR = 2.85, 95% CI, 1.52-5.35, P = 0.001; RFS: HR = 2.55, 95% CI, 1.37-4.72, P = 0.003). No prognostic significance was observed for the other two subgroups (low/high and high/low) when compared to the low/low subgroup in this study population. Therefore, we suggest that the prognostic value of SHP2 could reflect the nuclear localization of SHP2 and its interaction with nuclear YAP1, which led to subsequent upregulation of cyclin D1 and c-Myc mRNA expression via activation of the Wnt/ß-catenin signaling pathway.

Post-treatment de-phosphorylation of p53 correlates with dasatinib responsiveness in malignant melanoma

BACKGROUND

Dasatinib (Sprycel) was developed as a tyrosine kinase inhibitor targeting Bcr-Abl and the family of Src kinases. Dasatinib is commonly used for the treatment of acute lymphoblastic and chronic myelogenous leukemia. Previous clinical studies in melanoma returned inconclusive results and suggested that patients respond highly heterogeneously to dasatinib as single agent or in combination with standard-of-care chemotherapeutic dacarbazine. Reliable biomarkers to predict dasatinib responsiveness in melanoma have not yet been developed.

RESULTS

Here, we collected comprehensive in vitro data from experimentally well-controlled conditions to study the effect of dasatinib, alone and in combination with dacarbazine, on cell proliferation and cell survival. Sixteen treatment conditions, covering therapeutically relevant concentrations ranges of both drugs, were tested in 12 melanoma cell lines with diverse mutational backgrounds. Melanoma cell lines responded heterogeneously and, importantly, dasatinib and dacarbazine did not synergize in suppressing proliferation or inducing cell death. Since dasatinib is a promiscuous kinase inhibitor, possibly affecting multiple disease-relevant pathways, we also determined if basal phospho-protein amounts and treatment-induced changes in phospho-protein levels are indicative of dasatinib responsiveness. We found that treatment-induced de-phosphorylation of p53 correlates with dasatinib responsiveness in malignant melanoma.

CONCLUSIONS

Loss of p53 phosphorylation might be an interesting candidate for a kinetic marker of dasatinib responsiveness in melanoma, pending more comprehensive validation in future studies.

Protein Tyrosine Phosphatases: Regulators of CD4 T Cells in Inflammatory Bowel Disease

Protein tyrosine phosphatases (PTPs) play a critical role in co-ordinating the signaling networks that maintain lymphocyte homeostasis and direct lymphocyte activation. By dephosphorylating tyrosine residues, PTPs have been shown to modulate enzyme activity and both mediate and disrupt protein-protein interactions. Through these molecular mechanisms, PTPs ultimately impact lymphocyte responses to environmental cues such as inflammatory cytokines and chemokines, as well as antigenic stimulation. Mouse models of acute and chronic intestinal inflammation have been shown to be exacerbated in the absence of PTPs such as PTPN2 and PTPN22. This increase in disease severity is due in part to hyper-activation of lymphocytes in the absence of PTP activity. In accordance, human PTPs have been linked to intestinal inflammation. Genome wide association studies (GWAS) identified several PTPs within risk loci for inflammatory bowel disease (IBD). Therapeutically targeting PTP substrates and their associated signaling pathways, such as those implicated in CD4⁺ T cell responses, has demonstrated clinical efficacy. The current review focuses on the role of PTPs in controlling CD4⁺ T cell activity in the intestinal mucosa and how disruption of PTP activity in CD4⁺ T cells can contribute to intestinal inflammation.

Structural reorganization of SHP2 by oncogenic mutations and implications for oncoprotein resistance to allosteric inhibition

Activating mutations in PTPN11, encoding the cytosolic protein tyrosine phosphatase SHP2, result in developmental disorders and act as oncogenic drivers in patients with hematologic cancers. The allosteric inhibitor SHP099 stabilizes the wild-type SHP2 enzyme in an autoinhibited conformation that is itself destabilized by oncogenic mutations. Here, we report the impact of the highly activated and most frequently observed mutation, E76K, on the structure of SHP2, and investigate the effect of E76K and other oncogenic mutations on allosteric inhibition by SHP099. SHP2^E76K adopts an open conformation but can be restored to the closed, autoinhibited conformation, near-identical to the unoccupied wild-type enzyme, when complexed with SHP099. SHP099 inhibitory activity against oncogenic SHP2 variants in vitro and in cells scales inversely with the activating strength of the mutation, indicating that either oncoselective or vastly more potent inhibitors will be necessary to suppress oncogenic signaling by the most strongly activating SHP2 mutations in cancer.

Activating mutations of the non-receptor protein tyrosine phosphatase SHP2 can cause cancer. Here the authors present the crystal structure of SHP2^E76K, the most frequent cancer-associated SHP2 mutation, which adopts an open-state structure and show that the allosteric inhibitor SHP099 can revert SHP2^E76K to its closed, autoinhibited conformation.

Exploring the effect of N308D mutation on protein tyrosine phosphatase-2 cause gain-of-function activity by a molecular dynamics study

One of the most common protein tyrosine phosphatase-2 (SHP2) mutations in Noonan syndrome is the N308D mutation, and it increases the activity of the protein. However, the molecular basis of the activation of N308D mutation on SHP2 conformations is poorly understood. Here, molecular dynamic simulations were performed on SHP2 and SHP2-N308D to explore the effect of N308D mutation on SHP2 cause gain of function activity, respectively. The principal component analysis, dynamic cross-correlation map, secondary structure analysis, residue interaction networks, and solvent accessible surface area analysis suggested that the N308D mutation distorted the residues interactions network between the allosteric site (residue Gly244-Gly246) and C-SH2 domain, including the hydrogen bond formation and the binding energy. Meanwhile, the activity of catalytic site (residue Gly503-Val505) located in the Q-loop in mutant increased due to this region's high fluctuations. Therefore, the substrate had more chances to access to the catalytic activity site of the precision time protocol domain of SHP2-N308D, which was easy to be exposed. In addition, we had speculated that the Lys244 located in the allosteric site was the key residue which lead to the protein conformation changes. Consequently, overall calculations presented in this study ultimately provide a useful understanding of the increased activity of SHP2 caused by the N308D mutation.

Hyperglycaemia-induced methylglyoxal accumulation potentiates VEGF resistance of diabetic monocytes through the aberrant activation of tyrosine phosphatase SHP-2/SRC kinase signalling axis

Diabetes mellitus (DM) is a major cardiovascular risk factor contributing to cardiovascular complications by inducing vascular cell dysfunction. Monocyte dysfunction could contribute to impaired arteriogenesis response in DM patients. DM monocytes show blunted chemotactic responses to arteriogenic stimuli, a condition termed as vascular endothelial growth factor (VEGF) resistance. We hypothesize that methylglyoxal (MG), a glucose metabolite, induces monocyte dysfunction and aimed to elucidate the underlying molecular mechanisms. Human monocytes exposed to MG or monocytes from DM patients or mice (db/db) showed VEGF-resistance secondary to a pro-migratory phenotype. Mechanistically, DM conditions or MG exposure resulted in the upregulation of the expression of SHP-2 phosphatase. This led to the enhanced activity of SHP-2 and aided an interaction with SRC kinase. SHP-2 dephosphorylated the inhibitory phosphorylation site of SRC leading to its abnormal activation and phosphorylation of cytoskeletal protein, paxillin. We demonstrated that MG-induced molecular changes could be reversed by pharmacological inhibitors of SHP-2 and SRC and by genetic depletion of SHP-2. Finally, a SHP-2 inhibitor completely reversed the dysfunction of monocytes isolated from DM patients and db/db mice. In conclusion, we identified SHP-2 as a hitherto unknown target for improving monocyte function in diabetes. This opens novel perspectives for treating diabetic complications associated with impaired monocyte function.

Inducible SHP-2 activation confers resistance to imatinib in drug-tolerant chronic myeloid leukemia cells

BCR-ABL kinase mutations, accounting for clinical resistance to tyrosine kinase inhibitor (TKI) such as imatinib, frequently occur in acquired resistance or in advanced phases of chronic myeloid leukemia (CML). Emerging evidence implicates a critical role for non-mutational drug resistance mechanisms underlying the survival of residual cancer 'persister' cells. Here, we utilized non-mutational imatinib-resistant K562/G cells to reveal SHP-2 as a resistance modulator of imatinib treatment response during the early phase. SHP-2 phosphorylation was significantly higher in K562/G cells than in sensitive K562 cells. In K562 cells, both short-term and long-term exposure to imatinib induced SHP-2 phosphorylation. Consistently, gain- and loss-of-function mutants in SHP-2 proved its regulation of imatinib resistance. SHP-2 inhibitor and imatinib exhibited a strong antitumor synergy in in vitro and in vivo K562/G models. Mechanistically, dual SHP-2 and BCR-ABL inhibition blocked RAF/MEK/ERK and PI3K/AKT/mTOR pathways, respectively, leading to dramatic apoptotic death of K562/G cells. In conclusion, our results highlight that SHP-2 could be exploited as a biomarker and therapeutic target during the early phase of imatinib resistance development in CML.

Protein Tyrosine Phosphatases as Potential Regulators of STAT3 Signaling

The signal transducer and activator of transcription 3 (STAT3) protein is a major transcription factor involved in many cellular processes, such as cell growth and proliferation, differentiation, migration, and cell death or cell apoptosis. It is activated in response to a variety of extracellular stimuli including cytokines and growth factors. The aberrant activation of STAT3 contributes to several human diseases, particularly cancer. Consequently, STAT3-mediated signaling continues to be extensively studied in order to identify potential targets for the development of new and more effective clinical therapeutics. STAT3 activation can be regulated, either positively or negatively, by different posttranslational mechanisms including serine or tyrosine phosphorylation/dephosphorylation, acetylation, or demethylation. One of the major mechanisms that negatively regulates STAT3 activation is dephosphorylation of the tyrosine residue essential for its activation by protein tyrosine phosphatases (PTPs). There are seven PTPs that have been shown to dephosphorylate STAT3 and, thereby, regulate STAT3 signaling: PTP receptor-type D (PTPRD), PTP receptor-type T (PTPRT), PTP receptor-type K (PTPRK), Src homology region 2 (SH-2) domain-containing phosphatase 1(SHP1), SH-2 domain-containing phosphatase 2 (SHP2), MEG2/PTP non-receptor type 9 (PTPN9), and T-cell PTP (TC-PTP)/PTP non-receptor type 2 (PTPN2). These regulators have great potential as targets for the development of more effective therapies against human disease, including cancer.

Inhibition of SHP2 by new compounds induces differential effects on RAS/RAF/ERK and PI3K/AKT pathways in different cancer cell types

Kinases and phosphatases are important players in growth signaling and are involved in cancer development. For development of targeted cancer therapy, attention is given to kinases rather than phosphatases inhibitors. Src homology region 2 domain-containing protein tyrosine phosphatase2 (SHP2) is overexpressed in different types of cancers. We investigated the SHP2-inhibitory effects of two new 5-aminosalicylate-4-thiazolinones in human cervical (HeLa) and breast (MCF-7 & MDA-MB-231) cancer cells. In-silico molecular docking showed preferential affinity of the two compounds towards the catalytic over the allosteric site of SHP2. An enzymatic assay confirmed the docking results whereby 0.01 μM of both compounds reduced SHP2 activity to 50%. On cellular level, the two compounds significantly reduced the expression of SHP2, KRAS, p-ERK and p-STAT3 in HeLa but not in the other two cell lines. Phosphorylation of AKT and JNK was enhanced in HeLa and MCF7. Both compounds exhibited anti-proliferative/anti-migratory effects on HeLa and MCF7 but not in MDA-MB-231 cells. These results indicate that inhibition of SHP2 and its downstream pathways by the two compounds might be a promising strategy for cancer therapy in some but not all cancer types.

Myeloid-restricted ablation of Shp2 restrains melanoma growth by amplifying the reciprocal promotion of CXCL9 and IFN-γ production in tumor microenvironment

The Src homology 2 domain-containing protein tyrosine phosphatase 2 (Shp2) is generally considered to be an oncogene owing to its ability in enhancing the malignancy of multiple types of tumor cells; however, its role in modulating tumor immunity remains largely elusive. Here, we reported that myeloid-restricted ablation of Shp2 suppressed melanoma growth. Mechanistically, loss of Shp2 potentiates macrophage production of CXCL9 in response to IFN-γ and tumor cell-derived cytokines, thereby facilitating the tumor infiltration of IFN-γ-producing T cells that could in turn support CXCL9 production within tumor microenvironment. Collectively, our findings highlight a causative role of myeloid Shp2 in dampening T cell-mediated antitumor immunity by restraining the macrophage/CXCL9-T cell/IFN-γ feedback loop. Thus, targeting macrophage Shp2 may help to create a Th1-dominant tumor immune microenvironment.

A shift in the IL-6/STAT3 signalling pathway imbalance towards the SHP2 pathway in severe asthma results in reduced proliferation process

BACKGROUND

Bronchial fibroblasts are the main structural cells responsible for extracellular matrix production and turnover in lung tissue. They play a key role in airway remodelling in asthma through different cytokines including interleukin (IL-6).

OBJECTIVE

To decipher IL-6 signalling in bronchial fibroblasts obtained from severe eosinophilic asthmatics compared to mild asthmatics and healthy controls.

METHODS

Human bronchial fibroblasts were isolated from bronchial biopsies of mild and severe eosinophilic asthmatics and non-atopic healthy controls. IL-6 was assessed by qRT-PCR and ELISA. Phosphorylated STAT3, SHP2 and p38/MAPK were evaluated by Western blot. Chemical inhibitors for SHP2 and p38 were used. Fibroblast proliferation was evaluated by BrdU incorporation test.

RESULTS

IL-6 release was significantly increased in fibroblasts from mild and severe asthmatics compared to healthy controls. Fibroblasts from severe asthmatics showed a reduced STAT3 activation compared to mild asthmatics and healthy controls. Constitutive activation of phosphatase SHP2 was found to negatively regulate IL-6 induced STAT3 phosphorylation in fibroblasts from severe asthmatics. This effect was accompanied by a decrease in fibroblast proliferation rate due to the activated p38/mitogen-activated protein kinase. SHP2 and p38/MAPK specific inhibitors (PHPS1 and SB212190) significantly induce a restoration of STAT3 phosphorylation, IL-6 target gene expression and cell proliferation.

CONCLUSION

These data show dysregulated IL-6 signalling in bronchial fibroblasts derived from severe eosinophilic asthmatic subjects involving the protein tyrosine phosphatase SHP2 and p38MAPK. Collectively, our data provides new insights into the mechanisms by which bronchial fibroblasts regulate airway remodelling in severe asthma.

Helicobacter pylori-induced gastric pathology: insights from in vivo and ex vivo models

Gastric colonization with Helicobacter pylori induces diverse human pathological conditions, including superficial gastritis, peptic ulcer disease, mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric adenocarcinoma and its precursors. The treatment of these conditions often relies on the eradication of H. pylori, an intervention that is increasingly difficult to achieve and that does not prevent disease progression in some contexts. There is, therefore, a pressing need to develop new experimental models of H. pylori-associated gastric pathology to support novel drug development in this field. Here, we review the current status of in vivo and ex vivo models of gastric H. pylori colonization, and of Helicobacter-induced gastric pathology, focusing on models of gastric pathology induced by H. pylori, Helicobacter felis and Helicobacter suis in rodents and large animals. We also discuss the more recent development of gastric organoid cultures from murine and human gastric tissue, as well as from human pluripotent stem cells, and the outcomes of H. pylori infection in these systems.

Shp2 confers cisplatin resistance in small cell lung cancer via an AKT-mediated increase in CA916798

The tyrosine phosphatase Shp2 is associated with tumorigenesis in small cell lung cancer (SCLC). However, the relationship between Shp2 and resistance to chemotherapy remains unclear. Here, we show that Shp2 plays an important role in inducing resistance to cisplatin-based chemotherapy via the SHP2-AKT-CA916798 pathway. In an SCLC cell line, overexpression of Shp2 induced cisplatin resistance and the increased expression of AKT, pAKT, pmTOR, and CA916798. Conversely, depletion of Shp2 in a cisplatin-resistant cell line via RNA interference increased cisplatin sensitivity and decreased AKT, pAKT, pmTOR, and CA916798 expression levels. Activation of AKT stimulated CA916798 expression and altered the level of Shp2. A mouse xenograft model verified the results obtained from the in vitro experiments. In addition, we collected and analyzed clinical SCLC specimens and found that Shp2 levels correlated with CA916798 expression in tumor tissues. Importantly, higher levels of Shp2 or CA916798 were associated with a poorer prognosis in SCLC patients who received chemotherapy. Together, our findings indicate that Shp2 induces cisplatin resistance in SCLC patients via the SHP2-AKT-CA916798 pathway. Therefore, Shp2 and CA916798 may be promising biomarkers for predicting resistance to chemotherapy and may function as targets for enhancing treatments.

Small molecule targeting of PTPs in cancer

Protein tyrosine phosphatases (PTPs) undeniably have a central role in the development and progression of human cancers. Historically, however, PTPs have not been viewed as privileged drug targets, and progress on identifying potent, selective, and cell-active small molecule PTP inhibitors has suffered accordingly. This situation is rapidly changing, however, due to biochemical advances in the study of PTPs and recent small molecule screening campaigns, which have identified potent and mechanistically diverse lead structures. These compounds are facilitating the exploration of the fundamental cellular processes controlled by PTPs in cancers, and could form the inflection point for new therapeutic paradigms for the treatment of a range of cancers. Herein, we review recent advances in the discovery and biological annotation of cancer-relevant small molecule PTP inhibitors.

SHP2 overexpression enhances the invasion and metastasis of ovarian cancer in vitro and in vivo

Purpose

SHP2 has roles in a variety of signal transduction pathways and in many important cellular processes, including proliferation, differentiation, movement regulation, and apoptosis. In addition, SHP2 expression is closely associated with multiple types of malignancies. In this study, we examined the role of SHP2 in epithelial ovarian cancer.

Patients and methods

SHP2 expression in cancer and normal ovarian tissue specimens was evaluated by immunohistochemical staining and Western blot analyses. The correlation between the SHP2 expression level and clinicopathological features was analyzed. The role of SHP2 in epithelial ovarian cancer was evaluated by assessing SHP2 expression patterns in vitro and in vivo, and activation of the PI3K/AKT pathway was examined.

Results

SHP2 is expressed at higher levels in ovarian cancer tissues than in normal ovarian tissues and in an ovarian cancer cell line than in a normal ovarian cell line. On the basis of these findings, SHP2 is overexpressed in ovarian cancer both in vitro and in vivo. In addition, SHP2 overexpression is associated with tumor stage and differentiation, enhanced cell proliferation and invasion, and tumorigenesis and metastasis.

Conclusion

SHP2 overexpression enhances ovarian tumor proliferation and invasion by activating the PI3K-AKT axis, indicating that SHP2 potentially plays a direct role in the pathogenesis of ovarian epithelial cell cancer. These novel findings provide key insights that are applicable to basic cancer research and to the prevention and treatment of cancer.

Amino-acid sensing and degrading pathways in immune regulation

Indoleamine 2,3-dioxygenases (IDOs) - belonging in the heme dioxygenase family and degrading tryptophan - are responsible for the de novo synthesis of nicotinamide adenine dinucleotide (NAD⁺). As such, they are expressed by a variety of invertebrate and vertebrate species. In mammals, IDO1 has remarkably evolved to expand its functions, so to become a prominent homeostatic regulator, capable of modulating infection and immunity in multiple ways, including local tryptophan deprivation, production of biologically active tryptophan catabolites, and non-enzymatic cell-signaling activity. Much like IDO1, arginase 1 (Arg1) is an immunoregulatory enzyme that catalyzes the degradation of arginine. Here, we discuss the possible role of amino-acid degradation as related to the evolution of the immune systems and how the functions of those enzymes are linked by an entwined pathway selected by phylogenesis to meet the newly arising needs imposed by an evolving environment.

Targeting endogenous proteins for degradation through the affinity-directed protein missile system

Targeted proteolysis of endogenous proteins is desirable as a research toolkit and in therapeutics. CRISPR/Cas9-mediated gene knockouts are irreversible and often not feasible for many genes. Similarly, RNA interference approaches necessitate prolonged treatments, can lead to incomplete knockdowns and are often associated with off-target effects. Targeted proteolysis can overcome these limitations. In this report, we describe an affinity-directed protein missile (AdPROM) system that harbours the von Hippel-Lindau (VHL) protein, the substrate receptor of the Cullin2 (CUL2) E3 ligase complex, tethered to polypeptide binders that selectively bind and recruit endogenous target proteins to the CUL2-E3 ligase complex for ubiquitination and proteasomal degradation. By using synthetic monobodies that selectively bind the protein tyrosine phosphatase SHP2 and a camelid-derived VHH nanobody that selectively binds the human ASC protein, we demonstrate highly efficient AdPROM-mediated degradation of endogenous SHP2 and ASC in human cell lines. We show that AdPROM-mediated loss of SHP2 in cells impacts SHP2 biology. This study demonstrates for the first time that small polypeptide binders that selectively recognize endogenous target proteins can be exploited for AdPROM-mediated destruction of the target proteins.

Role of STAT3 and FOXO1 in the Divergent Therapeutic Responses of Non-metastatic and Metastatic Bladder Cancer Cells to miR-145

Although miR-145 is the most frequently downregulated miRNA in bladder cancer, its exact stage association and downstream effector have not been defined. Here, we found that miR-145 was upregulated in human patients with bladder cancer with lymph node metastasis and in metastatic T24T cell line. Forced expression of miR-145 promoted anchorage-independent growth of T24T cells accompanied by the downregulation of forkhead box class O1 (FOXO1). In contrast, in non-metastatic T24 cells, miR-145 overexpression inhibited cell growth with upregulation of FOXO1, and the knockdown of FOXO1 abolished the miR-145-mediated inhibition of cell growth. Mechanistic studies revealed that miR-145 directly bound to and attenuated 3'-untranslated region (UTR) activity of foxo1 mRNA in both T24 and T24T cells. Interestingly, miR-145 suppressed STAT3 phosphorylation at Tyr705 and increased foxo1 promoter transcriptional activity in T24 cells, but not in T24T cells, suggesting a role of STAT3 in the divergent responses to miR-145. Supporting this was our finding that STAT3 knockdown mimicked miR-145-mediated upregulation of FOXO1 in T24T cells and inhibition of anchorage-independent growth. Consistently, ectopic expression of miR-145 promoted tumor formation of xenograft T24T cells, whereas such promoting effect became inhibitory due to specific knockdown of STAT3. Together, our findings demonstrate the stage-specific association and function of miR-145 in bladder cancers and provide novel insights into the therapeutic targeting of miR-145. Mol Cancer Ther; 16(5); 924-35. ©2017 AACR.

Escape from IFN-γ-dependent immunosurveillance in tumorigenesis

Immune interferon (IFN), also known as IFN-γ, promotes not only immunomodulation but also antimicrobial and anticancer activity. After IFN-γ binds to the complex of IFN-γ receptor (IFNGR) 1-IFNGR2 and subsequently activates its downstream signaling pathways, IFN-γ immediately causes transcriptional stimulation of a variety of genes that are principally involved in its biological activities. Regarding IFN-γ-dependent immunosurveillance, IFN-γ can directly suppress tumorigenesis and infection and/or can modulate the immunological status in both cancer cells and infected cells. Regarding the anticancer effects of IFN-γ, cancer cells develop strategies to escape from IFN-γ-dependent cancer immunosurveillance. Immune evasion, including the recruitment of immunosuppressive cells, secretion of immunosuppressive factors, and suppression of cytotoxic T lymphocyte responses, is speculated to be elicited by the oncogenic microenvironment. All of these events effectively downregulate IFN-γ-expressing cells and IFN-γ production. In addition to these extrinsic pathways, cancer cells may develop cellular tolerance that manifests as hyporesponsiveness to IFN-γ stimulation. This review discusses the potential escape mechanisms from IFN-γ-dependent immunosurveillance in tumorigenesis.

Targeting protein kinase-b3 (akt3) signaling in melanoma

INTRODUCTION

Deregulated Akt activity leading to apoptosis inhibition, enhanced proliferation and drug resistance has been shown to be responsible for 35-70% of advanced metastatic melanomas. Of the three isoforms, the majority of melanomas have elevated Akt3 expression and activity. Hence, potent inhibitors targeting Akt are urgently required, which is possible only if (a) the factors responsible for the failure of Akt inhibitors in clinical trials is known; and (b) the information pertaining to synergistically acting targeted therapeutics is available. Areas covered: This review provides a brief introduction of the PI3K-Akt signaling pathway and its role in melanoma development. In addition, the functional role of key Akt pathway members such as PRAS40, GSK3 kinases, WEE1 kinase in melanoma development are discussed together with strategies to modulate these targets. Efficacy and safety of Akt inhibitors is also discussed. Finally, the mechanism(s) through which Akt leads to drug resistance is discussed in this expert opinion review. Expert opinion: Even though Akt play key roles in melanoma tumor progression, cell survival and drug resistance, many gaps still exist that require further understanding of Akt functions, especially in the (a) metastatic spread; (b) circulating melanoma cells survival; and

System analysis identifies distinct and common functional networks governed by transcription factor ASCL1, in glioma and small cell lung cancer

Systematic functional network analysis of ASCL1 revealed that it regulates mitosis and cell proliferation pathways and has distinct functions in glioma and SCLC.

RASopathy Gene Mutations in Melanoma

Next-generation sequencing of melanomas has unraveled critical driver genes and genomic abnormalities, mostly defined as occurring at high frequency. In addition, less abundant mutations are present that link melanoma to a set of disorders, commonly called RASopathies. These disorders, which include neurofibromatosis and Noonan and Legius syndromes, harbor germline mutations in various RAS/mitogen-activated protein kinase signaling pathway genes. We highlight shared amino acid substitutions between this set of RASopathy mutations and those observed in large-scale melanoma sequencing data, uncovering a significant overlap. We review the evidence that these mutations activate the RAS/mitogen-activated protein kinase pathway in melanoma and are involved in melanomagenesis. Furthermore, we discuss the observations that two or more RASopathy mutations often co-occur in melanoma and may act synergistically on activating the pathway.

The use of SHP-2 gene transduced bone marrow mesenchymal stem cells to promote osteogenic differentiation and bone defect repair in rat

Bone tissue engineering is a promising approach for bone regeneration, in which growth factors play an important role. The tyrosine phosphatase Src-homology region 2-containing protein tyrosine phosphatase 2 (SHP2), encoded by the PTPN11 gene, is essential for the differentiation, proliferation and metabolism of osteoblasts. However, SHP-2 has never been systematically studied for its effect in osteogenesis. We predicted that overexpression of SHP-2 could promote bone marrow-derived mesenchymal stem cell (BMSC)osteogenic differentiation and SHP-2 transduced BMSCs could enhance new bone formation, determined using the following study groups: (1) BMSCs transduced with SHP-2 and induced with osteoblast-inducing liquid (BMSCs/SHP-2/OL); (2) BMSCs transduced with SHP-2 (BMSCs/-SHP-2); (3) BMSCs induced with osteoblast-inducing liquid (BMSCs/OL) and (4) pure BMSCs. Cells were assessed for osteogenic differentiation by quantitative real-time polymerase chain reaction analysis, western blot analysis, alkaline phosphatase activity and alizarin red S staining. For in vivo assessment, cells were combined with beta-tricalcium phosphate scaffolds and transplanted into rat calvarial defects for 8 weeks. Following euthanasia, skull samples were explanted for osteogenic evaluation, including micro-computed tomography measurement, histology and immunohistochemistry staining. SHP-2 and upregulation of its gene promoted BMSC osteogenic differentiation and therefore represents a potential new therapeutic approach to bone repair. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1871-1881, 2016.

SHP-2 Mediates Cryptosporidium parvum Infectivity in Human Intestinal Epithelial Cells

The parasite, Cryptosporidium parvum, induces human gastroenteritis through infection of host epithelial cells in the small intestine. During the initial stage of infection, C. parvum is reported to engage host mechanisms at the host cell-parasite interface to form a parasitophorous vacuole. We determined that upon infection, the larger molecular weight proteins in human small intestinal epithelial host cells (FHs 74 Int) appeared to globally undergo tyrosine dephosphorylation. In parallel, expression of the cytoplasmic protein tyrosine phosphatase Src homology-2 domain-containing phosphatase 2 (SHP-2) increased in a time-dependent manner. SHP-2 co-localized with the C. parvum sporozoite and this interaction increased the rate of C. parvum infectivity through SH2-mediated SHP-2 activity. Furthermore, we show that one potential target that SHP-2 acts upon is the focal adhesion protein, paxillin, which undergoes moderate dephosphorylation following infection, with inhibition of SHP-2 rescuing paxillin phosphorylation. Importantly, treatment with an inhibitor to SHP-2 and with an inhibitor to paxillin and Src family kinases, effectively decreased the multiplicity of C. parvum infection in a dose-dependent manner. Thus, our study reveals an important role for SHP-2 in the pathogenesis of C. parvum. Furthermore, while host proteins can be recruited to participate in the development of the electron dense band at the host cell-parasite interface, our study implies for the first time that SHP-2 appears to be recruited by the C. parvum sporozoite to regulate infectivity. Taken together, these findings suggest that SHP-2 and its down-stream target paxillin could serve as targets for intervention.