Lack of phosphotyrosine phosphatase SHP-1 expression in malignant T-cell lymphoma cells results from methylation of the SHP-1 promoter

The cross-talk between miRNAs and JAK/STAT pathway in cutaneous T cell lymphoma: Emphasis on therapeutic opportunities

Mycosis Fungoides (MF) and Sézary Syndrome (SS) belong to a wide spectrum of T cell lymphoproliferative disorders collectively termed cutaneous T cell lymphomas (CTCL). CTCLs represent an archetype of heterogeneous and dynamically variable lymphoproliferative neoplasms typified by distinct clinical, histological, immunophenotypic, and genetic features. Owing to its complex dynamics, the pathogenesis of CTCL remains elusive. However, in recent years, progress in CTCL classification combined with next-generation sequencing analyses has broadened the genetic and epigenetic spectrum of clearly defined CTCL entities such as MF and SS. Several large-scale genome studies have identified the polygenic nature of CTCL and unveiled an idiosyncratic mutational landscape involving genetic aberrations, epigenetic alterations, cell cycle dysregulation, apoptosis, and the constitutive activation of T cell/NF-κB/JAK-STAT signaling pathways. In this review, we summarize the evolving insights on how the intrinsic epigenetic events driven by dysregulated miRNAs, including the oncogenic and tumor-suppressive miRNAs, influence the pathogenesis of MF and SS. We also focus on the interplay between the JAK/STAT pathway and miRNAs in CTCL as well as the significance of the miRNA/STAT axis as a relevant pathogenetic mechanism underlying CTCL initiation and progression. Based on these biologic insights, the current status and recent progress on novel therapies with a strong biological rationale, including miRNA-targeted molecules and JAK/STAT-targeted therapy for CTCL management, are discussed.

Chimeric kinase ALK induces expression of NAMPT and selectively depends on this metabolic enzyme to sustain its own oncogenic function

As we show in this study, NAMPT, the key rate-limiting enzyme in the salvage pathway, one of the three known pathways involved in NAD synthesis, is selectively over-expressed in anaplastic T-cell lymphoma carrying oncogenic kinase NPM1::ALK (ALK + ALCL). NPM1::ALK induces expression of the NAMPT-encoding gene with STAT3 acting as transcriptional activator of the gene. Inhibition of NAMPT affects ALK + ALCL cells expression of numerous genes, many from the cell-signaling, metabolic, and apoptotic pathways. NAMPT inhibition also functionally impairs the key metabolic and signaling pathways, strikingly including enzymatic activity and, hence, oncogenic function of NPM1::ALK itself. Consequently, NAMPT inhibition induces cell death in vitro and suppresses ALK + ALCL tumor growth in vivo. These results indicate that NAMPT is a novel therapeutic target in ALK + ALCL and, possibly, other similar malignancies. Targeting metabolic pathways selectively activated by oncogenic kinases to which malignant cells become "addicted" may become a novel therapeutic approach to cancer, alternative or, more likely, complementary to direct inhibition of the kinase enzymatic domain. This potential therapy to simultaneously inhibit and metabolically "starve" oncogenic kinases may not only lead to higher response rates but also delay, or even prevent, development of drug resistance, frequently seen when kinase inhibitors are used as single agents.

Global and promoter specific hypermethylation of tumor suppressor genes P16, SOCS1, and SHP1 in oral squamous cell carcinoma and oral submucous fibrosis

ABSTRACTS

Aberrant methylation pattern leads to altered gene expression, that is, involved in the transformation of various cancers, including oral squamous cell carcinoma (OSCC). In the present study, an attempt has been made to examine the association of global and promoter-specific methylation of tumor suppressor genes in patients with OSCC and oral submucous fibrosis (OSMF). Promoter-specific methylation of tumor suppressor genes P16, SOCS1, and SHP1 had been studied earlier for their aberrant methylation patterns in other cancers; however, these studies were mainly conducted in-vitro or in animal models, and as such, only a few studies are available on human samples. In the present study evaluation of promoter-specific methylation of genes P16, SOCS1, and SHP1 in 76 patients' blood and tissue samples was done and compared with methylation of 35 healthy control samples using qPCR. Further, these samples were analyzed for global methylation patterns using ELISA. The results have shown a significant decreasing trend of promoter methylation (OSCC > OSMF > Controls); the methylation indices (MI) were significantly higher in OSCC than in the controls. The median MI of three genes for OSCC were P16MI (0.96), SHP1MI (0.79), and SOCS1 (0.80). Similarly, median MIs for OSMF were P16MI (0.18), SHP1 MI (0.19), and SOCS1 MI (0.5) against controls with MI (0) for each of the three genes. The global methylation %mC values were 1.9, 0.5, and 0.1, respectively. The values of MI and %mC were found to correlate with various risk factors such as tobacco, smoking, and alcohol consumption, which are positively involved in OSMF pathogenesis followed by oral cancer progression. Further, the methylation trend in tissue was reflected in blood samples, proving a window for methylation load to be used as a lesser invasive biomarker. The sensitivity and specificity of methylation load were also found reasonable. Therefore, the current study suggests that there may be a role of global and promoter-specific methylation load in the transition of OSMF to OSCC.

Repair of Limb Ischemia Is Dependent on Hematopoietic Stem Cell Specific-SHP-1 Regulation of TGF-β1

BACKGROUND

Hematopoietic stem cell (HSC) therapy has shown promise for tissue regeneration after ischemia. Therefore, there is a need to understand mechanisms underlying endogenous HSCs activation in response to ischemic stress and coordination of angiogenesis and repair. SHP-1 plays important roles in HSC quiescence and differentiation by regulation of TGF-β1 signaling. TGF-β1 promotes angiogenesis by stimulating stem cells to secrete growth factors to initiate the formation of blood vessels and later aid in their maturation. We propose that SHP-1 responds to ischemia stress in HSC and progenitor cells (HSPC) via regulation of TGF-β1.

METHODS

A mouse hind limb ischemia model was used. Local blood perfusion in the limbs was determined using laser doppler perfusion imaging. The number of positive blood vessels per square millimeter, as well as blood vessel diameter (μm) and area (μm²), were calculated. Hematopoietic cells were analyzed using flow cytometry. The bone marrow transplantation assay was performed to measure HSC reconstitution.

RESULTS

After femoral artery ligation, TGF-β1 was initially decreased in the bone marrow by day 3 of ischemia, followed by an increase on day 7. This pattern was opposite to that in the peripheral blood, which is concordant with the response of HSC to ischemic stress. In contrast, SHP-1 deficiency in HSC is associated with irreversible activation of HSPCs in the bone marrow and increased circulating HSPCs in peripheral blood following limb ischemia. In addition, there was augmented auto-induction of TGF-β1 and sustained inactivation of SHP-1-Smad2 signaling, which impacted TGF-β1 expression in HSPCs in circulation. Importantly, restoration of normal T GF-β1 oscillations helped in the recovery of limb repair and function.

CONCLUSIONS

HSPC-SHP-1-mediated regulation of TGF-β1 in both bone marrow and peripheral blood is required for a normal response to ischemic stress.

Molecular pathogenesis of Cutaneous T cell Lymphoma: Role of chemokines, cytokines, and dysregulated signaling pathways

Cutaneous T cell lymphomas (CTCLs) are a heterogeneous group of lymphoproliferative neoplasms that exhibit a wide spectrum of immune-phenotypical, clinical, and histopathological features. The biology of CTCL is complex and remains elusive. In recent years, the application of next-generation sequencing (NGS) has evolved our understanding of the pathogenetic mechanisms, including genetic aberrations and epigenetic abnormalities that shape the mutational landscape of CTCL and represent one of the important pro-tumorigenic principles in CTCL initiation and progression. Still, identification of the major pathophysiological pathways including genetic and epigenetic components that mediate malignant clonal T cell expansion has not been achieved. This is of prime importance given the role of malignant T cell clones in fostering T helper 2 (Th2)-bias tumor microenvironment and fueling progressive immune dysregulation and tumor cell growth in CTCL patients, manifested by the secretion of Th2-associated cytokines and chemokines. Alterations in malignant cytokine and chemokine expression patterns orchestrate the inflammatory milieu and influence the migration dynamics of malignant clonal T cells. Here, we highlight recent insights about the molecular mechanisms of CTCL pathogenesis, emphasizing the role of cytokines, chemokines, and associated downstream signaling networks in driving immune defects, malignant transformation, and disease progression. In-depth characterization of the CTCL immunophenotype and tumoral microenvironment offers a facile opportunity to expand the therapeutic armamentarium of CTCL, an intractable malignant skin disease with poor prognosis and in dire need of curative treatment approaches.

Next-Generation Sequencing Analysis of CpG Methylation of a Tumor Suppressor Gene SHP-1 Promoter in Stable Cell Lines and HCV-Positive Patients

Hepatitis C virus (HCV) is the major causative pathogen associated with hepatocellular carcinoma and liver cirrhosis. The main virion component, the Core (C) protein, is involved in multiple aspects of HCV pathology including oncogenesis and immune evasion. In this study, we established a next-generation bisulfite sequencing (NGS-BS) protocol to analyze the CpG methylation profile at the tumor suppressor gene SHP-1 P2 promoter as a model system. Our data show that HCV C protein expression in the immortalized T cells correlated with a specific CpG methylation profile at the SHP-1 P2. The NGS-BS on HCV-positive (HCV⁺) patient-derived PBMCs revealed a considerably different CpG methylation profile compared to the HCV C protein immortalized T cells. Notably, the CpG methylation profile was very similar in healthy and HCV⁺ PBMCs, suggesting that the SHP-1 P2 CpG methylation profile is not altered in the HCV⁺ individuals. Collectively, the NGS-BS is a highly sensitive method that can be used to quantitatively characterize the CpG methylation status at the level of individual CpG position and also allows the characterization of cis-acting effects on epigenetic regulation.

SHP-1 dephosphorylates histone H2B to facilitate its ubiquitination during transcription

Dynamic regulation of phosphorylation and dephosphorylation of histones is essential for eukaryotic transcription, but the enzymes engaged in histone dephosphorylation are not fully explored. Here, we show that the tyrosine phosphatase SHP-1 dephosphorylates histone H2B and plays a critical role during transition from the initiation to the elongation stage of transcription. Nuclear-localized SHP-1 is associated with the Paf1 complex at chromatin and dephosphorylates H2B at tyrosine 121. Moreover, knockout of SHP-1, or expression of a mutant mimicking constitutive phosphorylation of H2B Y121, leads to a reduction in genome-wide H2B ubiquitination, which subsequently causes defects in RNA polymerase II-dependent transcription. Mechanistically, we demonstrate that Y121 phosphorylation precludes H2B's interaction with the E2 enzyme, indicating that SHP-1-mediated dephosphorylation of this residue may be a prerequisite for efficient H2B ubiquitination. Functionally, we find that SHP-1-mediated H2B dephosphorylation contributes to maintaining basal autophagic flux in cells through the efficient transcription of autophagy and lysosomal genes. Collectively, our study reveals an important modification of histone H2B regulated by SHP-1 that has a role during eukaryotic transcription.

Interfering B cell receptor signaling via SHP-1/p-Lyn axis shows therapeutic potential in diffuse large B-cell lymphoma

Background

Diffuse large B cell lymphoma (DLBCL) is an aggressive and molecularly heterogeneous non-Hodgkin’s lymphoma. The B cell receptor (BCR) signaling pathway in DLBCL emerges as a new drug target. Protein phosphatase SHP-1 negatively regulates several oncogenic tyrosine kinases and plays a tumor suppressive role.

Methods

The direct SHP-1 agonists were used to evaluate the potential therapeutic implication of SHP-1 in DLBCL. Immunohistochemical staining for SHP-1 was quantified by H-score. The SHP-1 phosphatase activity was determined using tyrosine phosphatase assay. In vitro studies, including MTT, western blot analysis and cell apoptosis, were utilized to examined biological functions of SHP-1.

Results

Oral administration of SHP-1 agonist showed the potent anti-tumor effects compared to a selective Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib in mice bearing U2932 xenografts. SHP-1 agonist increased SHP-1 activity as well as downregulated p-Lyn in vivo. Here, we demonstrated that immunohistochemical staining for SHP-1 expression was positive in 76% of DLBCL samples. SHP-1 agonist exerted anti-proliferative and apoptotic effects compared with ibrutinib in DLBCL cells. Mechanistically, SHP-1 agonist decreased BCR signaling, especially p-Lyn, and led to apoptosis.

Conclusions

These data suggest that SHP-1 negatively regulates phosphorylation of Lyn, and targeting SHP-1/p-Lyn using SHP-1 agonist has therapeutic potential for treatment of DLBCL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00518-0.

Hepatitis C Virus Core Protein Down-Regulates Expression of Src-Homology 2 Domain Containing Protein Tyrosine Phosphatase by Modulating Promoter DNA Methylation

Hepatitis C virus (HCV) is the major causative pathogen associated with liver cirrhosis and hepatocellular carcinoma. The main virion component, the core (C) protein, has been implicated in several aspects of HCV pathology including oncogenesis and immune subversion. Here we show that expression of the C protein induced specific tyrosine phosphorylation of the TCR-related signaling proteins ZAP-70, LAT and PLC-γ in the T cells. Stable expression of the C protein specifically reduced Src homology domain 2-containing protein tyrosine phosphatase 1 (SHP-1) mRNA and protein accumulation. Quantitative CpG methylation analysis revealed a distinct CpG methylation pattern at the SHP-1 gene promoter in the C protein expressing cells that included specific hypermethylation of the binding site for Sp1 transcription factor. Collectively, our results suggest that HCV may suppress immune responses and facilitate its own persistence by deregulating phosphotyrosine signaling via repressive epigenetic CpG modification at the SHP-1 promoter in the T cells.

Exploiting the STAT3 Nexus in Cancer-Associated Fibroblasts to Improve Cancer Therapy

The tumor microenvironment (TME) is composed of a heterogenous population of cells that exist alongside the extracellular matrix and soluble components. These components can shape an environment that is conducive to tumor growth and metastatic spread. It is well-established that stromal cancer-associated fibroblasts (CAFs) in the TME play a pivotal role in creating and maintaining a growth-permissive environment for tumor cells. A growing body of work has uncovered that tumor cells recruit and educate CAFs to remodel the TME, however, the mechanisms by which this occurs remain incompletely understood. Recent studies suggest that the signal transducer and activator of transcription 3 (STAT3) is a key transcription factor that regulates the function of CAFs, and their crosstalk with tumor and immune cells within the TME. CAF-intrinsic STAT3 activity within the TME correlates with tumor progression, immune suppression and eventually the establishment of metastases. In this review, we will focus on the roles of STAT3 in regulating CAF function and their crosstalk with other cells constituting the TME and discuss the utility of targeting STAT3 within the TME for therapeutic benefit.

Epigenetics in psoriasis: perspective of DNA methylation

Psoriasis is a chronic inflammatory skin disease characterized by excessive proliferation of keratinocytes (KCs). Onset of psoriasis is related to genetic, immune and environmental factors. The environment can interact with the genome through epigenetic modifications, including DNA methylation, and this modification is involved in the pathogenesis of psoriasis. In addition to a skin disease, psoriasis is also considered a systemic disease. We reviewed the current literature of psoriatic DNA methylation for studies from several aspects on the DNA methylation distribution patterns in different tissues/cells, single-nucleotide polymorphisms, and candidate disease genes and identified target genes regulated by DNA methylation that have been directly/indirectly validated. This review contributes to a comprehensive understanding of the important a role that DNA methylation plays in psoriasis from a holistic perspective and will promote the implementation of DNA methylation in diagnostic and therapeutic strategies for psoriatic patients.

Epigenetics of cutaneous T-cell lymphoma: biomarkers and therapeutic potentials

Cutaneous T-cell lymphomas (CTCLs) are a heterogeneous group of skin-homing non-Hodgkin lymphomas. There are limited options for effective treatment of patients with advanced-stage CTCL, leading to a poor survival rate. Epigenetics plays a pivotal role in regulating gene expression without altering the DNA sequence. Epigenetic alterations are involved in virtually all key cancer-associated pathways and are fundamental to the genesis of cancer. In recent years, the epigenetic hallmarks of CTCL have been gradually elucidated and their potential values in the diagnosis, prognosis, and therapeutic intervention have been clarified. In this review, we summarize the current knowledge of the best-studied epigenetic modifications in CTCL, including DNA methylation, histone modifications, microRNAs, and chromatin remodelers. These epigenetic regulators are essential in the development of CTCL and provide new insights into the clinical treatments of this refractory disease.

Epigenetic alterations and advancement of treatment in peripheral T-cell lymphoma

Peripheral T-cell lymphoma (PTCL) is a rare and heterogeneous group of clinically aggressive diseases associated with poor prognosis. Except for ALK + anaplastic large-cell lymphoma (ALCL), most peripheral T-cell lymphomas are highly malignant and have an aggressive disease course and poor clinical outcomes, with a poor remission rate and frequent relapse after first-line treatment. Aberrant epigenetic alterations play an important role in the pathogenesis and development of specific types of peripheral T-cell lymphoma, including the regulation of the expression of genes and signal transduction. The most common epigenetic alterations are DNA methylation and histone modification. Histone modification alters the level of gene expression by regulating the acetylation status of lysine residues on the promoter surrounding histones, often leading to the silencing of tumour suppressor genes or the overexpression of proto-oncogenes in lymphoma. DNA methylation refers to CpG islands, generally leading to tumour suppressor gene transcriptional silencing. Genetic studies have also shown that some recurrent mutations in genes involved in the epigenetic machinery, including TET2, IDH2-R172, DNMT3A, RHOA, CD28, IDH2, TET2, MLL2, KMT2A, KDM6A, CREBBP, and EP300, have been observed in cases of PTCL. The aberrant expression of miRNAs has also gradually become a diagnostic biomarker. These provide a reasonable molecular mechanism for epigenetic modifying drugs in the treatment of PTCL. As epigenetic drugs implicated in lymphoma have been continually reported in recent years, many new ideas for the diagnosis, treatment, and prognosis of PTCL originate from epigenetics in recent years. Novel epigenetic-targeted drugs have shown good tolerance and therapeutic effects in the treatment of peripheral T-cell lymphoma as monotherapy or combination therapy. NCCN Clinical Practice Guidelines also recommended epigenetic drugs for PTCL subtypes as second-line therapy. Epigenetic mechanisms provide new directions and therapeutic strategies for the research and treatment of peripheral T-cell lymphoma. Therefore, this paper mainly reviews the epigenetic changes in the pathogenesis of peripheral T-cell lymphoma and the advancement of epigenetic-targeted drugs in the treatment of peripheral T-cell lymphoma (PTCL).

Cellular Interactions and Inflammation in the Pathogenesis of Cutaneous T-Cell Lymphoma

Cutaneous T-cell lymphoma (CTCL) comprises a group of lymphoproliferative diseases characterized by the accumulation of malignant T cells in chronically inflamed skin lesions. In early stages, the disease presents as skin patches or plaques covering a limited area of the skin and normally follows an indolent course. However, in a subset of patients the cutaneous lesions develop into tumors and the malignant T cells may spread to the lymphatic system, blood and internal organs with fatal consequences. Despite intensive research, the mechanisms driving disease progression remain incompletely understood. While most studies have focused on cancer cell-intrinsic oncogenesis, such as genetic and epigenetic events driving malignant transformation and disease progression, an increasing body of evidence shows that the interplay between malignant T cells and non-malignant cells plays a crucial role. Here, we outline some of the emerging mechanisms by which tumor, stromal and epidermal interactions may contribute to the progression of CTCL with particular emphasis on the crosstalk between fibroblasts, keratinocytes and malignant T cells.

STAT3 Dysregulation in Mature T and NK Cell Lymphomas

Abstract: T cell lymphomas comprise a distinct class of non-Hodgkin's lymphomas, which include mature T and natural killer (NK) cell neoplasms. While each malignancy within this group is characterized by unique clinicopathologic features, dysregulation in the Janus tyrosine family of kinases/Signal transducer and activator of transcription (JAK/STAT) signaling pathway, specifically aberrant STAT3 activation, is a common feature among these lymphomas. The mechanisms driving dysregulation vary among T cell lymphoma subtypes and include activating mutations in upstream kinases or STAT3 itself, formation of oncogenic kinases which drive STAT3 activation, loss of negative regulators of STAT3, and the induction of a pro-tumorigenic inflammatory microenvironment. Constitutive STAT3 activation has been associated with the expression of targets able to increase pro-survival signals and provide malignant fitness. Patients with dysregulated STAT3 signaling tend to have inferior clinical outcomes, which underscores the importance of STAT3 signaling in malignant progression. Targeting of STAT3 has shown promising results in pre-clinical studies in T cell lymphoma lines, ex-vivo primary malignant patient cells, and in mouse models of disease. However, targeting this pleotropic pathway in patients has proven difficult. Here we review the recent contributions to our understanding of the role of STAT3 in T cell lymphomagenesis, mechanisms driving STAT3 activation in T cell lymphomas, and current efforts at targeting STAT3 signaling in T cell malignancies.

Immunohistochemical Detection of Hematopoietic Cell-specific Protein-Tyrosine Phosphatase (Tyrosine Phosphatase SHP-1) in a Series of Endometrioid and Serous Endometrial Carcinoma

In this study, we evaluated the expression of SHP-1 (PTPN6) in endometrioid (Ec) and serous (Sc) subtypes of endometrial carcinoma by immunohistochemical analysis. In total, 114 patients with Ec carcinoma and 48 patients with Sc carcinoma were enrolled in this study. The correlation between the type of histology, the grade of tumor, the stage of development, and immunoreactivity to SHP-1 was evaluated. Kaplan-Meier and multivariate survival analyses, using a Cox regression model, were performed to establish whether this marker has prognostic value in these malignancies, on the basis of follow-up and stratification of the patients according to their SHP-1 immunoreactivity. A significantly higher SHP-1 expression was observed in the Ec group compared with the Sc group (P=0.0005, Fisher exact test). In the Ec group, SHP-1 immunoreactivity was correlated with grading, demonstrating that more differentiated lesions expressed SHP-1 more frequently than less differentiated neoplasms (G1 vs. G2, P=0.0243, statistically significant value, Fisher exact test; G1 vs. G3, P=0.0088, extremely significant value, Fisher exact test). Instead, in the Sc group, SHP-1 expression was not correlated with grading, as Sc is now defined as a high-grade carcinoma. SHP-1 expression did not change with neoplastic progression in Ec and Sc groups. From both univariate and multivariate analysis in the Ec group, expression of SHP-1 remained a positive prognostic factor (P=0.004, log-rank test) [HR=0.32 (0.11 to 0.94), P=0.039]. In contrast, in the Sc group, no correlation between SHP-1 expression and survival was noted (P=0.77, log-rank test). In this study, we observed that the absence of SHP-1 in immunohistochemical analysis might serve as a marker of poor prognosis for a subset of high-grade endometrial cancer.

Re-Expression of Bone Marrow Proteoglycan-2 by 5-Azacytidine is associated with STAT3 Inactivation and Sensitivity Response to Imatinib in Resistant CML Cells

Background:

Epigenetic silencing of tumor suppressor genes (TSG) is involved in development and progression of cancers. Re-expression of TSG is inversely proportionate with STAT3 signaling pathways. Demethylation of DNA by 5-Azacytidine (5-Aza) results in re-expression of silenced TSG. Forced expression of PRG2 by 5-Aza induced apoptosis in cancer cells. Imatinib is a tyrosine kinase inhibitor that potently inhibits BCR/ABL tyrosine kinase resulting in hematological remission in CML patients. However, majority of CML patients treated with imatinib would develop resistance under prolonged therapy.

Methods:

CML cells resistant to imatinib were treated with 5-Aza and cytotoxicity of imatinib and apoptosis were determined by MTS and annexin-V, respectively. Gene expression analysis was detected by real time-PCR, STATs activity examined using Western blot and methylation status of PRG2 was determined by pyrosequencing analysis.

Result:

Expression of PRG2 was significantly higher in K562-R+5-Aza cells compared to K562 and K562-R (p=0.001). Methylation of PRG2 gene was significantly decreased in K562-R+5-Aza cells compared to other cells (p=0.021). STAT3 was inactivated in K562-R+5-Aza cells which showed higher sensitivity to imatinib.

Conclusion:

PRG2 gene is a TSG and its overexpression might induce sensitivity to imatinib. However, further studies are required to evaluate the negative regulations of PRG2 on STAT3 signaling.

Nucleophosmin-anaplastic lymphoma kinase: the ultimate oncogene and therapeutic target

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase physiologically expressed by fetal neural cells. However, aberrantly expressed ALK is involved in the pathogenesis of diverse malignancies, including distinct types of lymphoma, lung carcinoma, and neuroblastoma. The aberrant ALK expression in nonneural cells results from chromosomal translocations that create novel fusion proteins. These protein hybrids compose the proximal part of a partner gene, including its promoter region, and the distal part of ALK, including the coding sequence for the entire kinase domain. ALK was first identified in a subset of T-cell lymphomas with anaplastic large cell lymphoma (ALCL) morphology (ALK+ ALCL), the vast majority of which harbor the well-characterized nucleophosmin (NPM)-ALK fusion protein. NPM-ALK co-opts several intracellular signal transduction pathways, foremost being the STAT3 pathway, normally activated by cytokines from the interleukin-2 (IL-2) family to promote cell proliferation and to inhibit apoptosis. Many genes and proteins modulated by NPM-ALK are also involved in evasion of antitumor immune response, protection from hypoxia, angiogenesis, DNA repair, cell migration and invasiveness, and cell metabolism. In addition, NPM-ALK uses epigenetic silencing mechanisms to downregulate tumor suppressor genes to maintain its own expression. Importantly, NPM-ALK is capable of transforming primary human CD4⁺ T cells into immortalized cell lines indistinguishable from patient-derived ALK+ ALCL. Preliminary clinical studies indicate that inhibition of NPM-ALK induces long-lasting complete remissions in a large subset of heavily pretreated adult patients and the vast majority of children with high-stage ALK+ ALCL. Combining ALK inhibition with other novel therapeutic modalities should prove even more effective.

Malignant inflammation in cutaneous T-cell lymphoma-a hostile takeover

Cutaneous T-cell lymphomas (CTCL) are characterized by the presence of chronically inflamed skin lesions containing malignant T cells. Early disease presents as limited skin patches or plaques and exhibits an indolent behavior. For many patients, the disease never progresses beyond this stage, but in approximately one third of patients, the disease becomes progressive, and the skin lesions start to expand and evolve. Eventually, overt tumors develop and the malignant T cells may disseminate to the blood, lymph nodes, bone marrow, and visceral organs, often with a fatal outcome. The transition from early indolent to progressive and advanced disease is accompanied by a significant shift in the nature of the tumor-associated inflammation. This shift does not appear to be an epiphenomenon but rather a critical step in disease progression. Emerging evidence supports that the malignant T cells take control of the inflammatory environment, suppressing cellular immunity and anti-tumor responses while promoting a chronic inflammatory milieu that fuels their own expansion. Here, we review the inflammatory changes associated with disease progression in CTCL and point to their wider relevance in other cancer contexts. We further define the term "malignant inflammation" as a pro-tumorigenic inflammatory environment orchestrated by the tumor cells and discuss some of the mechanisms driving the development of malignant inflammation in CTCL.

Jak3, STAT3, and STAT5 inhibit expression of miR-22, a novel tumor suppressor microRNA, in cutaneous T-Cell lymphoma

Aberrant activation of Janus kinase-3 (Jak3) and its key down-stream effectors, Signal Transducer and Activator of Transcription-3 (STAT3) and STAT5, is a key feature of malignant transformation in cutaneous T-cell lymphoma (CTCL). However, it remains only partially understood how Jak3/STAT activation promotes lymphomagenesis. Recently, non-coding microRNAs (miRNAs) have been implicated in the pathogenesis of this malignancy. Here, we show that (i) malignant T cells display a decreased expression of a tumor suppressor miRNA, miR-22, when compared to non-malignant T cells, (ii) STAT5 binds the promoter of the miR-22 host gene, and (iii) inhibition of Jak3, STAT3, and STAT5 triggers increased expression of pri-miR-22 and miR-22. Curcumin, a nutrient with anti-Jak3 activity and histone deacetylase inhibitors (HDACi) also trigger increased expression of pri-miR-22 and miR-22. Transfection of malignant T cells with recombinant miR-22 inhibits the expression of validated miR-22 targets including NCoA1, a transcriptional co-activator in others cancers, as well as HDAC6, MAX, MYCBP, PTEN, and CDK2, which have all been implicated in CTCL pathogenesis. In conclusion, we provide the first evidence that de-regulated Jak3/STAT3/STAT5 signalling in CTCL cells represses the expression of the gene encoding miR-22, a novel tumor suppressor miRNA.

Enhancing SHP-1 expression with 5-azacytidine may inhibit STAT3 activation and confer sensitivity in lestaurtinib (CEP-701)-resistant FLT3-ITD positive acute myeloid leukemia

Background

Tumor-suppressor genes are inactivated by methylation in several cancers including acute myeloid leukemia (AML). Src homology-2 (SH2)-containing protein-tyrosine phosphatase 1 (SHP-1) is a negative regulator of the JAK/STAT pathway. Transcriptional silencing of SHP-1 plays a critical role in the development and progression of cancers through STAT3 activation. 5-Azacytidine (5-Aza) is a DNA methyltransferase inhibitor that causes DNA demethylation resulting in re-expression of silenced SHP-1. Lestaurtinib (CEP-701) is a multi-targeted tyrosine kinase inhibitor that potently inhibits FLT3 tyrosine kinase and induces hematological remission in AML patients harboring the internal tandem duplication of the FLT3 gene (FLT3-ITD). However, the majority of patients in clinical trials developed resistance to CEP-701. Therefore, the aim of this study, was to assess the effect of re-expression of SHP-1 on sensitivity to CEP-701 in resistant AML cells.

Methods

Resistant cells harboring the FLT3-ITD were developed by overexposure of MV4-11 to CEP-701, and the effects of 5-Aza treatment were investigated. Apoptosis and cytotoxicity of CEP-701 were determined using Annexin V and MTS assays, respectively. Gene expression was performed by quantitative real-time PCR. STATs activity was examined by western blotting and the methylation profile of SHP-1 was studied using MS-PCR and pyrosequencing analysis. Repeated-measures ANOVA and Kruskal–Wallis tests were used for statistical analysis.

Results

The cytotoxic dose of CEP-701 on resistant cells was significantly higher in comparison with parental and MV4-11R-cep + 5-Aza cells (p = 0.004). The resistant cells showed a significant higher viability and lower apoptosis compared with other cells (p < 0.001). Expression of SHP-1 was 7-fold higher in MV4-11R-cep + 5-Aza cells compared to parental and resistant cells (p = 0.011). STAT3 was activated in resistant cells. Methylation of SHP-1 was significantly decreased in MV4-11R-cep + 5-Aza cells (p = 0.002).

Conclusions

The restoration of SHP-1 expression induces sensitivity towards CEP-701 and could serve as a target in the treatment of AML. Our findings support the hypothesis that, the tumor-suppressor effect of SHP-1 is lost due to epigenetic silencing and its re-expression might play an important role in re-inducing sensitivity to TKIs. Thus, SHP-1 is a plausible candidate for a role in the development of CEP-701 resistance in FLT3-ITD+ AML patients.

Tumor Suppressor Inactivation in the Pathogenesis of Adult T-Cell Leukemia

Tumor suppressor functions are essential to control cellular proliferation, to activate the apoptosis or senescence pathway to eliminate unwanted cells, to link DNA damage signals to cell cycle arrest checkpoints, to activate appropriate DNA repair pathways, and to prevent the loss of adhesion to inhibit initiation of metastases. Therefore, tumor suppressor genes are indispensable to maintaining genetic and genomic integrity. Consequently, inactivation of tumor suppressors by somatic mutations or epigenetic mechanisms is frequently associated with tumor initiation and development. In contrast, reactivation of tumor suppressor functions can effectively reverse the transformed phenotype and lead to cell cycle arrest or death of cancerous cells and be used as a therapeutic strategy. Adult T-cell leukemia/lymphoma (ATLL) is an aggressive lymphoproliferative disease associated with infection of CD4 T cells by the Human T-cell Leukemia Virus Type 1 (HTLV-I). HTLV-I-associated T-cell transformation is the result of a multistep oncogenic process in which the virus initially induces chronic T-cell proliferation and alters cellular pathways resulting in the accumulation of genetic defects and the deregulated growth of virally infected cells. This review will focus on the current knowledge of the genetic and epigenetic mechanisms regulating the inactivation of tumor suppressors in the pathogenesis of HTLV-I.

Promoter-Specific Hypomethylation Is Associated with Overexpression of PLS3, GATA6, and TWIST1 in the Sezary Syndrome

The Sézary Syndrome (SS) is an aggressive CD4+ leukemic variant of cutaneous T-cell lymphoma. Epigenetic modification of cancer cell genome is often linked to the expression of important cancer-related genes. Here we addressed the hypothesis that, in SS, DNA hypomethylation is involved in upregulation of PLS3, GATA6, and TWIST1, genes that are undetected in normal lymphocytes. Pyrosequencing analysis of CpG rich regions, and CpG dinucleotides within the 5' regulatory regions, confirmed hypomethylation of all three genes in SS, compared with controls. We then studied how methylation regulates PLS3 transcription in vitro using PLS3-negative (Jurkat) and PLS3-positive (HT-1080) cell lines. Treatment with the hypomethylating agent 5-azacytidine induced PLS3 expression in Jurkat cells and in vitro methylation of the cloned PLS3 promoter suppressed luciferase expression in HT-1080 cells. In conclusion, we show that promoter hypomethylation is associated with PLS3, GATA6, and TWIST1 overexpression in SS CD4+ T cells and that methylation can regulate PLS3 expression in vitro. The mechanisms of DNA hypomethylation in vivo and the functional role of PLS3, TWIST1, and GATA6 in SS are being investigated.

Tumor antigen ROR1 targeted drug delivery mediated selective leukemic but not normal B-cell cytotoxicity in chronic lymphocytic leukemia

Selective cytotoxicity to cancer cells without compromising their normal counterparts pose a huge challenge for traditional drug design. Here we developed a tumor antigen-targeted delivery of immunonanoparticle carrying a novel non-immunosuppressive FTY720 derivative OSU-2S with potent cytotoxicity against leukemic B cells. OSU-2S induces activation of protein phosphatase 2A (PP2A), phosphorylation and nuclear translocation of SHP1(S591) and deregulation of multiple cellular processes in chronic lymphocytic leukemia (CLL) resulting in potent cytotoxicity. To preclude OSU-2S-mediated effects on these ubiquitous phosphatases in unintended cells and avoid potential adverse effects, we developed an OSU-2S-targeted delivery of immunonanoparticles (2A2-OSU-2S-ILP), that mediated selective cytotoxicity of CLL but not normal B cells through targeting receptor tyrosine kinase ROR1 expressed in leukemic but not normal B cells. Developing a novel spontaneous CLL mouse model expressing human ROR1 (hROR1) in all leukemic B cells, we demonstrate the therapeutic benefit of enhanced survival with 2A2-OSU-2S-ILP in vivo. The newly developed non-immunosuppressive OSU-2S, its delivery using human CLL directed immunonanoparticles and the novel transgenic (Tg) mouse model of CLL that expresses hROR1 exclusively in leukemic B cell surface are highly innovative and can be applied to CLL and other ROR1+ malignancies including mantle cell lymphoma and acute lymphoblastic leukemia.

Valproic acid increases NO production via the SH-PTP1-CDK5-eNOS-Ser(116) signaling cascade in endothelial cells and mice

Valproic acid (VPA) with its inhibitory activity of histone deacetylase has been used in the treatment of epilepsy and bipolar disorder associated with cerebrovascular dysfunction. Because nitric oxide (NO) produced by endothelial NO synthase (eNOS) plays a role in the maintenance of vascular function, NO is likely to mediate VPA׳s drug effect, but its effect on NO production remains controversial. We investigated whether and how VPA regulates NO production in bovine aortic endothelial cells (BAECs) and mice. VPA increased NO production in BAECs, which was accompanied by a decrease in phosphorylation of eNOS at serine 116 (eNOS-Ser(116)) and cyclin-dependent kinase 5 at tyrosine 15 (CDK5-Tyr(15)). Ectopic expression of p25, a CDK5 activator, restored the VPA-inhibited eNOS-Ser(116) phosphorylation. In silico analysis revealed that the CDK5-Tyr(15) residue might be a substrate for SH2 domain-containing protein tyrosine phosphatase 1 (SH-PTP1), and CDK5 actually interacted with SH-PTP1. VPA increased SH-PTP1 expression and its activity. Stibogluconate, a specific SH-PTP1 inhibitor, reversed the VPA-inhibited phosphorylation of CDK5-Tyr(15) and eNOS-Ser(116). Knockdown of SH-PTP1 using small interfering RNA also reversed all the observed effects of VPA. Finally, both serum NO level and acetylcholine-induced aortic relaxation increased in VPA-medicated male mice. These increases were accompanied by increased SH-PTP1 expression and decreased phosphorylation of CDK5-Tyr(15) and eNOS-Ser(116) in mouse aortas. In conclusion, VPA increases NO production by inhibiting the CDK5-Tyr(15)-eNOS-Ser(116) phosphorylation axis; this process is mediated by SH-PTP1. VPA may be useful in the treatment of NO-related cerebrocardiovascular diseases.

STAT3 in Cancer-Friend or Foe?

The roles and significance of STAT3 in cancer biology have been extensively studied for more than a decade. Mounting evidence has shown that constitutive activation of STAT3 is a frequent biochemical aberrancy in cancer cells, and this abnormality directly contributes to tumorigenesis and shapes many malignant phenotypes in cancer cells. Nevertheless, results from more recent experimental and clinicopathologic studies have suggested that STAT3 also can exert tumor suppressor effects under specific conditions. Importantly, some of these studies have demonstrated that STAT3 can function either as an oncoprotein or a tumor suppressor in the same cell type, depending on the specific genetic background or presence/absence of specific coexisting biochemical defects. Thus, in the context of cancer biology, STAT3 can be a friend or foe. In the first half of this review, we will highlight the “evil” features of STAT3 by summarizing its oncogenic functions and mechanisms. The differences between the canonical and non-canonical pathway will be highlighted. In the second half, we will summarize the evidence supporting that STAT3 can function as a tumor suppressor. To explain how STAT3 may mediate its tumor suppressor effects, we will discuss several possible mechanisms, one of which is linked to the role of STAT3β, one of the two STAT3 splicing isoforms. Taken together, it is clear that the roles of STAT3 in cancer are multi-faceted and far more complicated than one appreciated previously. The new knowledge has provided us with new approaches and strategies when we evaluate STAT3 as a prognostic biomarker or therapeutic target.

Staphylococcal enterotoxins stimulate lymphoma-associated immune dysregulation

Patients with cutaneous T-cell lymphoma (CTCL) are frequently colonized with Staphylococcus aureus (SA). Eradication of SA is, importantly, associated with significant clinical improvement, suggesting that SA promotes the disease activity, but the underlying mechanisms remain poorly characterized. Here, we show that SA isolates from involved skin express staphylococcal enterotoxins (SEs) that induce crosstalk between malignant and benign T cells leading to Stat3-mediated interleukin-10 (IL-10) production by the malignant T cells. The SEs did not stimulate the malignant T cells directly. Instead, SEs triggered a cascade of events involving cell-cell and asymmetric cytokine interactions between malignant and benign T cells, which stimulated the malignant T cells to express high levels of IL-10. Much evidence supports that malignant activation of the Stat3/IL-10 axis plays a key role in driving the immune dysregulation and severe immunodeficiency that characteristically develops in CTCL patients. The present findings thereby establish a novel link between SEs and immune dysregulation in CTCL, strengthening the rationale for antibiotic treatment of colonized patients with severe or progressive disease.

Methylation and decreased expression of SHP-1 are related to disease progression in chronic myelogenous leukemia

Despite the unprecedented success of tyrosine kinase inhibitors (TKIs) in treating chronic myelogenous leukemia (CML), some patients nevertheless progress to advanced stages of the disease. Thus far, the biological basis leading to CML progression remains poorly understood. SH2-containing tyrosine phosphatase 1 (SHP-1) is reported to bind to p210BCR‑ABL1 and to function as a tumor suppressor. Furthermore, its substrates have been found to be essential for p210BCR-ABL1 leukemogenesis or CML progression. In the present study, we found that SHP-1 mRNA and protein levels were markedly decreased in patients in the accelerated and blastic phases of CML (AP-CML and BP-CML) compared to those in the chronic phase (CP-CML). In vitro, we demonstrated that overexpression of SHP-1 reduced p210BCR-ABL1 protein expression and activity in the K562 CML cell line and negatively regulated the AKT, MAPK, MYC and JAK2/STAT5 signaling pathways. Moreover, using a methylation-specific polymerase chain reaction (MSP) assay, abnormal methylation of the SHP-1 gene promoter region was found both in K562 cells and bone marrow (BM) or peripheral blood (PB) cells from AP-CML and BP-CML patients. In conclusion, our findings suggest that decreased expression levels of SHP-1 caused by aberrant promoter hypermethylation may play a key role in the progression of CML by dysregulating BCR-ABL1, AKT, MAPK, MYC and JAK2/STAT5 signaling.

Epigenetic mechanisms of protein tyrosine phosphatase 6 suppression in diffuse large B-cell lymphoma: implications for epigenetic therapy

Protein tyrosine phosphatases such as PTPN6 can be downregulated in various neoplasms. PTPN6 expression by immunohistochemistry in 40 diffuse large B-cell lymphoma (DLBCL) tumors was lost or suppressed in 53% (21/40). To elucidate the molecular mechanisms of PTPN6 suppression, we performed a comprehensive epigenetic analysis of PTPN6 promoter 2 (P2). None of the DLBCL primary tumors (0/37) had PTPN6 hypermethylation on the CpG1 island using methylation-specific PCR, pyrosequencing, and high-resolution melting assays. However, hypermethylation in 57% (21/37) of cases was found in a novel CpG island (CpG2) in P2. PTPN6 gene suppression was reversed by 5-aza-deoxycytidine (5-Aza), a DNA methyltransferase inhibitor, and the histone deacetylase inhibitor (HDACi) LBH589. LBH589 and 5-Aza in combination inhibited DLBCL survival and PTPN6 hypermethylation at CpG2. The role of histone modifications was investigated with a chromatin-immunoprecipitation assay demonstrating that PTPN6 P2 is associated with silencing histone marks H3K27me3 and H3K9me3 in DLBCL cells but not normal B cells. 3-Deazaneplanocin A, a histone methyltransferase inhibitor, decreased the H3K27me3 mark, whereas HDACi LBH589 increased the H3K9Ac mark within P2 resulting in re-expression of PTPN6. These studies have uncovered novel epigenetic mechanisms of PTPN6 suppression and suggest that PTPN6 may be a potential target of epigenetic therapy in DLBCL.

Elucidating the role of interleukin-17F in cutaneous T-cell lymphoma

Inappropriately regulated expression of interleukin (IL)-17A is associated with the development of inflammatory diseases and cancer. However, little is known about the role of other IL-17 family members in carcinogenesis. Here, we show that a set of malignant T-cell lines established from patients with cutaneous T-cell lymphoma (CTCL) spontaneously secrete IL-17F and that inhibitors of Janus kinases and Signal transducer and activator of transcription 3 are able to block that secretion. Other malignant T-cell lines produce IL-17A but not IL-17F. Upon activation, however, some of the malignant T-cell lines are able to coexpress IL-17A and IL-17F, leading to formation of IL-17A/F heterodimers. Clinically, we demonstrate that IL-17F messenger RNA expression is significantly increased in CTCL skin lesions compared with healthy donors and patients with chronic dermatitis. IL-17A expression is also increased and a significant number of patients express high levels of both IL-17A and IL-17F. Concomitantly, we observed that the expression of the IL-17 receptor is significantly increased in CTCL skin lesions compared with control subjects. Importantly, analysis of a historic cohort of 60 CTCL patients indicates that IL-17F expression is associated with progressive disease. These findings implicate IL-17F in the pathogenesis of CTCL and suggest that IL-17 cytokines and their receptors may serve as therapeutic targets.

SHP-1 protein tyrosine phosphatase associates with the adaptor protein CrkL

SHP-1, encoded by the PTPN6 gene, is a protein tyrosine phosphatase with two src-homology-2 (SH2) domains that is implicated as providing suppression of hematopoietic malignancies. A number of reports have shown protein-protein interactions between SHP-1 SH2 domains and tyrosine-phosphorylated proteins. However, despite its having three proline-rich, potential SH3-binding motifs, no reports of protein-protein interactions through src-homology-3 (SH3)-binding domains with SHP-1 have been described. Herein we show that the SH3 domain-containing CT10 regulator of kinase-like (CrkL) adaptor protein associates with SHP-1. We also provide results that suggest this association is due to CrkL binding to PxxP domains located at amino acid residues 158-161 within the SHP-1 C-terminal SH2 domain, and amino acid residues 363-366 within its phosphatase domain. This study is the first to identify and define an interaction between SHP-1 and an SH3 domain-containing protein. Our findings provide an alternative way that SHP-1 can be linked to potential substrates.

Alterations of negative regulators of cytokine signalling in immunodeficiency-related non-Hodgkin lymphoma

We investigated immunodeficiency-related non-Hodgkin lymphoma for the presence of molecular alterations affecting negative regulators of the Janus family protein tyrosine kinase/signal transducer and activator of transcription pathway. Protein tyrosine phosphatase, non-receptor type 6/Src homology 2-containing tyrosine phosphatase-1 epigenetic silencing was recurrent in primary effusion lymphoma (100%), and diffuse large B-cell lymphoma (63%), with a higher prevalence in the non-germinal centre subtype, and was associated with the activation of the Janus family protein tyrosine kinase/signal transducer and activator of transcription 3 pathway. Suppressor of cytokine signalling (SOCS)1 and SOCS3 epigenetic silencing were occasionally detected, whereas SOCS1 was frequently mutated in diffuse large B-cell lymphoma and polymorphic post-transplant lymphoproliferative disorders, possibly as a cause of aberrant somatic hypermutation. However, the mutation profile of the coding region of the gene was different from that expected from the aberrant somatic hypermutation process, suggesting that, at least in some cases, SOCS1 mutations may have been selected for their functional activity.

SHP-1 as a critical regulator of Mycoplasma pneumoniae-induced inflammation in human asthmatic airway epithelial cells

Asthma is a chronic inflammatory disease in which airway epithelial cells are the first line of defense against exposure of the airway to infectious agents. Src homology protein (SHP)-1, a protein tyrosine phosphatase, is a negative regulator of signaling pathways that are critical to the development of asthma and host defense. We hypothesize that SHP-1 function is defective in asthma, contributing to the increased inflammatory response induced by Mycoplasma pneumoniae, a pathogen known to exacerbate asthma. M. pneumoniae significantly activated SHP-1 in airway epithelial cells collected from nonasthmatic subjects by bronchoscopy with airway brushing but not in cells from asthmatic subjects. In asthmatic airway epithelial cells, M. pneumoniae induced significant PI3K/Akt phosphorylation, NF-κB activation, and IL-8 production compared with nonasthmatic cells, which were reversed by SHP-1 overexpression. Conversely, SHP-1 knockdown significantly increased IL-8 production and PI3K/Akt and NF-κB activation in the setting of M. pneumoniae infection in nonasthmatic cells, but it did not exacerbate these three parameters already activated in asthmatic cells. Thus, SHP-1 plays a critical role in abrogating M. pneumoniae-induced IL-8 production in nonasthmatic airway epithelial cells through inhibition of PI3K/Akt and NF-κB activity, but it is defective in asthma, resulting in an enhanced inflammatory response to infection.

SHP-1 expression accounts for resistance to imatinib treatment in Philadelphia chromosome-positive cells derived from patients with chronic myeloid leukemia

We prove that the SH2-containing tyrosine phosphatase 1 (SHP-1) plays a prominent role as resistance determinant of imatinib (IMA) treatment response in chronic myelogenous leukemia cell lines (sensitive/KCL22-S and resistant/KCL22-R). Indeed, SHP-1 expression is significantly lower in resistant than in sensitive cell line, in which coimmunoprecipitation analysis shows the interaction between SHP-1 and a second tyrosine phosphatase SHP-2, a positive regulator of RAS/MAPK pathway. In KCL22-R SHP-1 ectopic expression restores both SHP-1/SHP-2 interaction and IMA responsiveness; it also decreases SHP-2 activity after IMA treatment. Consistently, SHP-2 knocking-down in KCL22-R reduces either STAT3 activation or cell viability after IMA exposure. Therefore, our data suggest that SHP-1 plays an important role in BCR-ABL-independent IMA resistance modulating the activation signals that SHP-2 receives from both BCR/ABL and membrane receptor tyrosine kinases. The role of SHP-1 as a determinant of IMA sensitivity has been further confirmed in 60 consecutive untreated patients with chronic myelogenous leukemia, whose SHP-1 mRNA levels were significantly lower in case of IMA treatment failure (P < .0001). In conclusion, we suggest that SHP-1 could be a new biologic indicator at baseline of IMA sensitivity in patients with chronic myelogenous leukemia.

Constitutive activation of STAT3 in Sézary syndrome is independent of SHP-1

Constitutive and persistent activation of STAT3 has been implicated in the pathogenesis of many malignancies. Studies of CTCL cell lines have previously suggested that aberrant activation of STAT3 is mediated via silencing of the negative regulator SHP-1 by promoter methylation. In this study of ex vivo tumour cell populations from 18 Sézary syndrome (SS) patients, constitutive phosphorylation of STAT3, JAK1 and JAK2 was present in all patients, but was absent in comparative CD4+ T-cells from healthy controls. Furthermore, no loss or significant difference in SHP-1 expression was observed between patients and healthy control samples. Methylation-specific PCR analysis of the SHP-1 CpG island in 47 SS patients and 11 healthy controls did not detect any evidence of methylation. Moreover, small interfering RNA knockdown of SHP-1 had no effect on phosphorylation of STAT3. In contrast, treatment of SS tumour cells with the pan-JAK inhibitor pyridone 6 led to downregulation of phosphorylated STAT3 (pSTAT3), its target genes and induction of apoptosis. No evidence for common JAK1/JAK2-activating mutations was found. These data demonstrate that constitutive activation of STAT3 in SS is not due to the loss of SHP-1, but is mediated by constitutive aberrant activation of JAK family members.

Spontaneous insertion of a b2 element in the ptpn6 gene drives a systemic autoinflammatory disease in mice resembling neutrophilic dermatosis in humans

We found a spontaneous autosomal mutation in a mouse leading to neutrophil infiltration with ulceration in the upper dermis of homozygous offspring. These animals had increased neutrophil numbers, associated with normal lymphocyte count, in peripheral blood and bone marrow, suggesting a myeloproliferative disorder; however, granulocyte precursor proliferation in bone marrow was actually reduced (because circulating neutrophils were less susceptible to apoptosis). Neutrophil infiltration of the skin and other organs and high serum levels of immunoglobulins and autoantibodies, cytokines, and acute-phase proteins were additional abnormalities, all of which could be reduced by high-dose corticosteroid treatment or neutrophil depletion by antibodies. Use of genome-wide screening localized the mutation within an 0.4-Mbp region on mouse chromosome 6. We identified insertion of a B2 element in exon 6 of the Ptpn6 gene (protein tyrosine phosphatase, non-receptor type 6; also known as Shp-1). This insertion involves amino acid substitutions that significantly reduced the enzyme activity in mice homozygous for the mutation. Disease onset was delayed, and the clinical phenotype was milder than the phenotypes of other Ptpn6-mutants described in motheaten (me, mev) mice; we designated this new genotype as Ptpn6(meB2/meB2) and the phenotype as meB2. This new phenotype encompasses an autoinflammatory disease showing similarities to many aspects of the so-called neutrophilic dermatoses, a heterogeneous group of skin diseases with unknown etiology in humans.

Tyrosine phosphatase SHP-1 is expressed higher in multisystem than in single-system Langerhans cell histiocytosis by immunohistochemistry

Langerhans cell histiocytosis (LCH) is a proliferative disorder of Langerhans cell (LC)-like CD1a-positive cell (LCH cell) with unknown causes. LCH consists of two subtypes: single-system LCH (LCH-SS) with favorable prognosis and multisystem LCH (LCH-MS) with poor prognosis. LCH has been indicated as a neoplastic disorder from monoclonal characteristics of LCH cells. This study aimed to investigate an expression of tyrosine phosphatase SHP-1 in LCH, since its expression levels were variously reported in many tumors, overexpression in ovarian cancers (a candidate oncoprotein), and downregulation by methylation in gastric cancers, prostate cancers, malignant lymphomas, and leukemias (a putative tumor suppressor). By immunohistochemistry (IHC), the SHP-1 expression in LCs and LCH cells was compared in LCH (two subtypes: LCH-SS = 21, LCH-MS = 12), dermatopathic lymphadenopathy (DLA) (n = 9) and normal epidermal LCs (n = 3) near LCH lesion. IHC results were analyzed semiquantitatively using a Photoshop software. The mean intensity score (IS) of DLA, LCH-SS, LCH-MS, and LCs were 47, 100, 139, and 167 (in arbitrary unit), respectively. The IS had significant differences among LCH-SS, LCH-MS, and DLA (p < 0.01). SHP-1 is expressed significantly higher in LCH-MS than in LCH-SS. SHP-1 can be a progression marker of LCH. SHP-1 is also useful for differential diagnosis between LCH in lymph nodes and DLA.

A novel xenograft model of cutaneous T-cell lymphoma

Cutaneous T-cell lymphomas (CTCLs) are characterized by accumulation of malignant T cells in the skin. Early disease resembles benign skin disorders but during disease progression cutaneous tumors develop, and eventually the malignant T cells can spread to lymph nodes and internal organs. However, because of the lack of suitable animal models, little is known about the mechanisms driving CTCL development and progression in vivo. Here, we describe a novel xenograft model of tumor stage CTCL, where malignant T cells (MyLa2059) are transplanted to NOD/SCID-B2m(-/-) (NOD.Cg-Prkdc(scid) B2m(tm1Unc) /J) mice. Subcutaneous transplantation of the malignant T cells led to rapid tumor formation in 43 of 48 transplantations, whereas transplantation of non-malignant T cells isolated from the same donor did not result in tumor development. Importantly, the tumor growth was significantly suppressed in mice treated with vorinostat when compared to mice treated with vehicle. Furthermore, in most mice the tumors displayed subcutaneous and/or lymphatic dissemination. Histological, immunohistochemical and flow cytometric analyses confirmed that both tumors at the inoculation site, as well as distant subcutaneous and lymphatic tumors, originated from the transplanted malignant T cells. In conclusion, we describe a novel mouse model of tumor stage CTCL for future studies of disease dissemination and preclinical evaluations of new therapeutic strategies.

Malignant cutaneous T-cell lymphoma cells express IL-17 utilizing the Jak3/Stat3 signaling pathway

IL-17 is a proinflammatory cytokine that is crucial for the host's protection against a range of extracellular pathogens. However, inappropriately regulated expression of IL-17 is associated with the development of inflammatory diseases and cancer. In cutaneous T-cell lymphoma (CTCL), malignant T cells gradually accumulate in skin lesions characterized by massive chronic inflammation, suggesting that IL-17 could be involved in the pathogenesis. In this study we show that IL-17 protein is present in 10 of 13 examined skin lesions but not in sera from 28 CTCL patients. Importantly, IL-17 expression is primarily observed in atypical lymphocytes with characteristic neoplastic cell morphology. In accordance, malignant T-cell lines from CTCL patients produce IL-17 and the synthesis is selectively increased by IL-2 receptor β chain cytokines. Small-molecule inhibitors or small interfering RNA against Jak3 and signal transducer and activator of transcription 3 (Stat3) reduce the production of IL-17, showing that the Jak3/Stat3 pathway promotes the expression of the cytokine. In summary, our findings indicate that the malignant T cells in CTCL lesions express IL-17 and that this expression is promoted by the Jak3/Stat3 pathway.

Inside the human cancer tyrosine phosphatome

Members of the protein tyrosine phosphatase (Ptp) family dephosphorylate target proteins and counter the activities of protein tyrosine kinases that are involved in cellular phosphorylation and signalling. As such, certain PTPs might be tumour suppressors. Indeed, PTPs play an important part in the inhibition or control of growth, but accumulating evidence indicates that some PTPs may exert oncogenic functions. Recent large-scale genetic analyses of various human tumours have highlighted the relevance of PTPs either as putative tumour suppressors or as candidate oncoproteins. Progress in understanding the regulation and function of PTPs has provided insights into which PTPs might be potential therapeutic targets in human cancer.

PTP1B suppresses prolactin activation of Stat5 in breast cancer cells

Basal levels of nuclear localized, tyrosine phosphorylated Stat5 are present in healthy human breast epithelia. In contrast, Stat5 phosphorylation is frequently lost during breast cancer progression, a finding that correlates with loss of histological differentiation and poor patient prognosis. Identifying the mechanisms underlying loss of Stat5 phosphorylation could provide novel targets for breast cancer therapy. Pervanadate, a general tyrosine phosphatase inhibitor, revealed marked phosphatase regulation of Stat5 activity in breast cancer cells. Lentiviral-mediated shRNA allowed specific examination of the regulatory role of five tyrosine phosphatases (PTP1B, TC-PTP, SHP1, SHP2, and VHR), previously implicated in Stat5 regulation in various systems. Enhanced and sustained prolactin-induced Stat5 tyrosine phosphorylation was observed in T47D and MCF7 breast cancer cells selectively in response to PTP1B depletion. Conversely, PTP1B overexpression suppressed prolactin-induced Stat5 tyrosine phosphorylation. Furthermore, PTP1B knockdown increased Stat5 reporter gene activity. Mechanistically, PTP1B suppression of Stat5 phosphorylation was mediated, at least in part, through inhibitory dephosphorylation of the Stat5 tyrosine kinase, Jak2. PTP1B knockdown enhanced sensitivity of T47D cells to prolactin phosphorylation of Stat5 by reducing the EC(50) from 7.2 nmol/L to 2.5 nmol/L. Immunohistochemical analyses of two independent clinical breast cancer materials revealed significant negative correlations between levels of active Stat5 and PTP1B, but not TC-PTP. Collectively, our data implicate PTP1B as an important negative regulator of Stat5 phosphorylation in invasive breast cancer.

Tyrosine phosphatase SHP-1 in allergic and anaphylactic inflammation

Protein tyrosine phosphatase SHP-1 is an essential regulatory molecule in many different signaling pathways. The biological importance of SHP-1 is underscored by the motheaten mutant mouse strains with immunological disorders involving multiple organs and by the close association of aberrant SHP-1 expression with several human diseases. Recent studies provided some compelling evidence that supports a role of SHP-1 in regulating mast cell development and function and also in regulating type 2 allergic inflammatory responses in both innate and adaptive immune responses. In this article, we summarize the recent advancement of our understanding of this interesting phosphatase in the important area of allergic inflammation.

Promoter-specific induction of the phosphatase SHP-1 by viral infection and cytokines in CNS glia

We have previously shown that the protein tyrosine phosphatase SHP-1 is highly expressed in CNS glia and is an important modulator of cytokine signaling. As such, mice genetically lacking SHP-1 display constitutive myelin abnormalities, severe virus-induced demyelinating disease, and defects in innate anti-viral responses in the CNS. In this study, we show the differential distribution of the SHP-1 promoter-specific transcripts and demonstrate that several cytokines significantly induce SHP-1 expression in CNS glia. Consistent with these cytokine effects, infection with a neurotropic virus both in vitro and in vivo up-regulates SHP-1 transcripts and protein in CNS cells. Using CNS glial cultures of gene knockout mice, we show that interferons-beta and interferons-gamma act through STAT-1 and interferon regulatory factor-1 to induce the SHP-1 promoter I transcripts. Conversely, interferons-beta and IL-6 act through STAT-3 to induce SHP-1 promoter II transcripts. This study demonstrates that interferons and other cytokines associated with virus infections in the CNS can significantly induce the expression of SHP-1 through STAT-1/3 activity and provides a better understanding of the molecular mechanisms regulating cytokine-induced expression important for multiple homeostatic functions of SHP-1 in the CNS.

The tyrosine 343 residue of nucleophosmin (NPM)-anaplastic lymphoma kinase (ALK) is important for its interaction with SHP1, a cytoplasmic tyrosine phosphatase with tumor suppressor functions

The cytoplasmic tyrosine phosphatase SHP1 has been shown to inhibit the oncogenic fusion protein nucleophosmin (NPM)-anaplastic lymphoma kinase (ALK), and loss of SHP1 contributes to NPM-ALK-mediated tumorigenesis. In this study, we aimed to further understand how SHP1 interacts and regulates NPM-ALK. We employed an in vitro model in which GP293 cells were transfected with various combinations of NPM-ALK (or mutants) and SHP1 (or mutants) expression vectors. We found that SHP1 co-immunoprecipitated with NPM-ALK, but not the enzymatically inactive NPM-ALK(K210R) mutant, or the mutant in which all three functionally important tyrosine residues (namely, Tyr(338), Tyr(342), and Tyr(343)) in the kinase activation loop (KAL) of ALK were mutated. Interestingly, whereas mutation of Tyr(338) or Tyr(342) did not result in any substantial change in the NPM-ALK/SHP1 binding (assessed by co-immunoprecipitation), mutation of Tyr(343) abrogated this interaction. Furthermore, the NPM-ALK/SHP1 binding was readily detectable when each of the remaining 8 tyrosine residues known to be phosphorylated were mutated. Although the expression of SHP1 effectively reduced the level of tyrosine phosphorylation of NPM-ALK, it did not affect that of the NPM-ALK(Y343F) mutant. In soft agar clonogenic assay, SHP1 expression significantly reduced the tumorigenicity of NPM-ALK but not that of NPM-ALK(Y343F). In conclusion, we identified Tyr(343) of NPM-ALK as the crucial site for mediating the NPM-ALK/SHP1 interaction. Our results also support the notion that the tumor suppressor effects of SHP1 on NPM-ALK are dependent on its ability to bind to this oncogenic protein.

Lack of TNFalpha expression protects anaplastic lymphoma kinase-positive T-cell lymphoma (ALK+ TCL) cells from apoptosis

Here we report that T-cell lymphomas characterized by the expression of anaplastic lymphoma kinase (ALK+ TCL) fail to express the TNFalpha and frequently display DNA methylation of the TNFalpha gene promoter. While only a subset of the ALK+ TCL-derived cell lines showed a high degree of the promoter methylation, all 6 showed low to nondetectable expression of the TNFalpha mRNA, and none expressed the TNFalpha protein. All 14 ALK+ TCL tissue samples examined displayed some degree of the TNFalpha promoter methylation, which was the most prominent in the distal portion of the the promoter. Treatment with a DNA methyltransferase inhibitor, 5'-aza-2'-deoxy-cytidine (5-ADC), reversed the promoter methylation and led to the expression of TNFalpha mRNA and protein. Furthermore, in vitro DNA methylation of the promoter impaired its transcriptional activity in the luciferase reporter assay. This impairment was seen even if only either distal or proximal portion were methylated, with methylation of the former exerting a more profound inhibitory effect. Notably, the ALK+ TCL cell lines uniformly expressed the type 1 TNFalpha receptor (TNF-R1) protein known to transduce the TNFalpha-induced pro-apoptotic signals. Moreover, exogenous TNFalpha inhibited growth of the ALK+ TCL cell lines in a dose-dependent manner and induced activation of the members of the cell apoptotic pathway: Caspase 8 and caspase 3. These findings provide additional rationale for the therapeutic inhibition of DNA methyltransferases in ALK+ TCL. They also suggest that treatment with TNFalpha may be highly effective in this type of lymphoma.