Aberrant expression of the tyrosine kinase receptor EphA4 and the transcription factor twist in Sézary syndrome identified by gene expression analysis

Novel TBL1XR1, EPHA7 and SLFN12 mutations in a Sezary syndrome patient discovered by whole exome sequencing

Sezary syndrome (SS) is an aggressive leukaemic variant of cutaneous T-cell lymphoma. Recurrent chromosomal aberrations have been found in SS, but the whole genetic mutation spectrum is unknown. To better understand the molecular pathogenesis of SS, we performed exome sequencing, copy number variation (CNV) and gene expression analysis of primary SS cells. In our index patient with typical SS, we found novel somatic missense mutations in TBL1XR1, EPHA7 and SLFN12 genes in addition to larger chromosomal changes. The mutations are located in biologically relevant genes affecting apoptosis and T-cell maturation. They may play a role in the pathobiology of the disease, but no recurrent mutations were discovered in nine additional patients with SS studied. Thus, screening of larger patient cohorts is needed to confirm their prevalence and biological significance in SS.

Lessons learned from gene expression profiling of cutaneous T-cell lymphoma

Gene expression studies of cutaneous T-cell lymphoma (CTCL) span a decade, yet the pathogenesis is poorly understood and diagnosis remains a challenge. This review examines the varied approaches to gene expression analysis of CTCL, with emphasis on cell populations, control selection and expression data collection. Despite discordant results, several dysregulated genes have been identified across multiple studies, including PLS3, KIR3DL2, TWIST1 and STAT4. Here, we provide an overview of the most consistently expressed genes across different studies and bring them together through common pathways biologically relevant to CTCL. Four pathways - evasion of activation-induced cell death, T helper 2 lymphocyte differentiation, transforming growth factor-β receptor expression, and tumour necrosis factor receptor ligands - appear to encompass the most frequently affected genes, hypothetically providing insight into the disease pathogenesis.

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.

Sézary Syndrome

Sézary syndrome (SS), a type of cutaneous T-cell lymphoma with a poor prognosis, is characterized by erythroderma and leukemic involvement. Because of the rarity of SS and difficulty in diagnosis, data on this aggressive malignancy are scarce. In this review, the diagnosis and pathology of SS are summarized and an update is provided, highlighting microscopic features and novel molecular findings. The diagnostic challenge of SS is described, with an emphasis on the differential diagnosis of erythroderma and key points in distinguishing SS from other cutaneous T-cell malignancies. Finally, the prognosis is discussed, focusing on large, recent studies of SS patients.

The emerging role of Twist proteins in hematopoietic cells and hematological malignancies

Twist1 and Twist2 (Twist1–2) are two transcription factors, members of the basic helix-loop-helix family, that have been well established as master transcriptional regulators of embryogenesis and developmental programs of mesenchymal cell lineages. Their role in oncogenesis in epithelium-derived cancer and in epithelial-to-mesenchymal transition has also been thoroughly characterized. Recently, emerging evidence also suggests a key role for Twist1–2 in the function and development of hematopoietic cells, as well as in survival and development of numerous hematological malignancies. In this review, we summarize the latest data that depict the role of Twist1–2 in monocytes, T cells and B lymphocyte activation, and in associated hematological malignancies.

Exploring the IL-21-STAT3 axis as therapeutic target for Sézary syndrome

Sézary syndrome is an aggressive cutaneous T-cell lymphoma. The malignant cells (Sézary cells) are present in skin, lymph nodes, and blood, and express constitutively activated signal transducer and activator of transcription (STAT)3. STAT3 can be activated by IL-21 in vitro and the IL-21 gene itself is a STAT3 target gene, thereby creating an autocrine positive feedback loop that might serve as a therapeutic target. Sézary cells underwent apoptosis when incubated with Stattic, a selective STAT3 inhibitor. STAT3 activation in Sézary cells did not affect expression of the supposed anti-apoptotic STAT3 target genes BCL2, BCL-xL, and SURVIVIN, whereas expression of (proto)oncogenes miR-21, TWIST1, MYC, and PIM1 was significantly increased. CD3/CD28-mediated activation of Sézary cells induced IL-21 expression, accompanied by STAT3 activation and increased proliferation. Blocking IL-21 in CD3/CD28-activated cells had no effects, whereas Stattic abrogated IL-21 expression and cell proliferation. Thus, specific inhibition of STAT3 is highly efficient in the induction of apoptosis of Sézary cells, likely mediated via the regulation of (proto)oncogenes. In contrast, blocking IL-21 alone seems insufficient to affect STAT3 activation, cell proliferation, or apoptosis. These data provide further insights into the pathogenic role of STAT3 in Sézary syndrome and strengthen the notion that STAT3 represents a promising therapeutic target in this disease.

Analysis of STAT4 expression in cutaneous T-cell lymphoma (CTCL) patients and patient-derived cell lines

Deregulation of STAT signaling has been implicated in the pathogenesis for a variety of cancers, including CTCL. Recent reports indicate that loss of STAT4 expression is an important prognostic marker for CTCL progression and is associated with the acquisition of T helper 2 cell phenotype by malignant cells. However, little is known about the molecular mechanism behind the downregulation of STAT4 in this cancer. In the current work we test the expression of STAT4 and STAT6 via RT-PCR and/or Western Blot in CTCL lesional skin samples and in immortalized patient-derived cell lines. In these malignant cell lines we correlate the expression of STAT4 and STAT6 with the T helper (Th) phenotype markers and test the effect of Histone Deacetylase (HDAC) inhibitors and siRNA-mediated knock down of miR-155 on STAT4 expression. Our findings demonstrate that STAT4 expression correlates with Th1 phenotype, while STAT6 is associated with the Th2 phenotype. Our results further document that STAT4 and STAT6 genes are inversely regulated in CTCL. Treatment with HDAC inhibitors upregulates STAT4 expression, while at the same time decreases STAT6 expression in MyLa cells. Also, siRNA-mediated knock down of miR-155 leads to upregulation in STAT4 expression in MyLa cells. In summary, our results suggest that loss of STAT4 expression and associated switch to Th2 phenotype during Mycosis Fungoides progression may be driven via aberrant histone acetylation and/or upregulation of oncogenic miR-155 microRNA.

Discovery and characterization of a novel cyclic peptide that effectively inhibits ephrin binding to the EphA4 receptor and displays anti-angiogenesis activity

The EphA4 receptor tyrosine kinase regulates a variety of physiological and pathological processes during neural development and the formation of tumor blood vessels; thus, it represents a new and promising therapeutic target. We used a combination of phage peptide display and computer modeling/docking approaches and discovered a novel cyclic nonapeptide, now designated TYY. This peptide selectively inhibits the binding of the ephrinA5 ligand with EphA4 and significantly blocks angiogenesis in a 3D matrigel culture system. Molecular docking reveals that TYY recognizes the same binding pocket on EphA4 that the natural ephrin ligand binds to and that the Tyr3 and Tyr4 side chains of TYY are both critical for the TYY/EphA4 interaction. The discovery of TYY introduces a valuable probe of EphA4 function and a new lead for EphA4-targeted therapeutic development.

A novel mouse model for Sézary syndrome using xenotransplantation of Sézary cells into immunodeficient RAG2(-/-) γc(-/-) mice

Sézary syndrome (SS) is an aggressive cutaneous T-cell lymphoma with CD4+ tumor cells localized in the skin, lymph nodes and peripheral blood. Characteristic molecular aberrancies in SS have been identified; however, paucity of functional models severely hampered the translation of these observations into pathogenic mechanisms, and subsequent validation of novel therapeutic targets. We therefore developed a mouse model for SS using intrahepatic injection of SS cells in newborn immunodeficient RAG2(-/-) γc(-/-) mice that are completely devoid of T-, B- and NK-cell activity. Injection of the SS cell line SeAx led to long-term and reproducible systemic repopulation of the mice. Injection of mice with the SS cell line HuT-78 led to the death of the mice owing to massive growth of internal tumors. Four weeks after injection of primary SS cells, human CD3+ T cells could be tracked back in the liver, peripheral blood, lymph nodes, spleen and skin of the mice, although the engraftment rate varied when using cells from different patients. In conclusion, we demonstrate that injection of SS cell lines or primary cells in newborn RAG2(-/-) γc(-/-) mice results in long-term systemic repopulation of the mice, thereby providing a novel mouse model for Sézary syndrome.

Transcriptome sequencing in Sezary syndrome identifies Sezary cell and mycosis fungoides-associated lncRNAs and novel transcripts

Sézary syndrome (SS) is an aggressive cutaneous T-cell lymphoma (CTCL) of unknown etiology in which malignant cells circulate in the peripheral blood. To identify viral elements, gene fusions, and gene expression patterns associated with this lymphoma, flow cytometry was used to obtain matched pure populations of malignant Sézary cells (SCs) versus nonmalignant CD4(+) T cells from 3 patients for whole transcriptome, paired-end sequencing with an average depth of 112 million reads per sample. Pathway analysis of differentially expressed genes identified mis-regulation of PI3K/Akt, TGFβ, and NF-κB pathways as well as T-cell receptor signaling. Bioinformatic analysis did not detect either nonhuman transcripts to support a viral etiology of SS or recurrently expressed gene fusions, but it did identify 21 SC-associated annotated long noncoding RNAs (lncRNAs). Transcriptome assembly by multiple algorithms identified 13 differentially expressed unannotated transcripts termed Sézary cell-associated transcripts (SeCATs) that include 12 predicted lncRNAs and a novel transcript with coding potential. High-throughput sequencing targeting the 3' end of polyadenylated transcripts in archived tumors from 24 additional patients with tumor-stage CTCL confirmed the differential expression of SC-associated lncRNAs and SeCATs in CTCL. Our findings characterize the SS transcriptome and support recent reports that implicate lncRNA dysregulation in human malignancies.

Distinctive binding of three antagonistic peptides to the ephrin-binding pocket of the EphA4 receptor

The EphA4 receptor tyrosine kinase interacts with ephrin ligands to regulate many processes, ranging from axon guidance and nerve regeneration to cancer malignancy. Thus antagonists that inhibit ephrin binding to EphA4 could be useful for a variety of research and therapeutic applications. In the present study we characterize the binding features of three antagonistic peptides (KYL, APY and VTM) that selectively target EphA4 among the Eph receptors. Isothermal titration calorimetry analysis demonstrated that all three peptides bind to the ephrin-binding domain of EphA4 with low micromolar affinity. Furthermore, the effects of a series of EphA4 mutations suggest that the peptides interact in different ways with the ephrin-binding pocket of EphA4. Chemical-shift changes observed by NMR spectroscopy upon binding of the KYL peptide involve many EphA4 residues, consistent with extensive interactions and possibly receptor conformational changes. Additionally, systematic replacement of each of the 12 amino acids of KYL and VTM identify the residues critical for EphA4, binding. The peptides exhibit a long half-life in cell culture medium which, with their substantial binding affinity and selectivity for EphA4, makes them excellent research tools to modulate EphA4 function.

Increased Twist expression in advanced stage of mycosis fungoides and Sézary syndrome

BACKGROUND

The mechanisms of tumor progression in mycosis fungoides (MF) and Sézary syndrome (SS) are poorly understood. Twist, a transcription factor, is thought to promote solid tumor progression by blocking p53 and inhibiting c-myc-induced apoptosis. Whether Twist expression is correlated to MF/SS stages remains unknown.

METHODS

Twist, c-myc and p53 proteins in 68 MF/SS lesions across all T stages were examined by immunohistochemistry, and mRNA levels in peripheral blood CD4+ T-cells from SS patients were measured by real-time quantitative polymerase chain reaction.

RESULTS

Positive staining for Twist was found in 12.5% (2/16) of T1 and 33.3% (7/21) of T2 early stage patches/plaques compared to 50.0% (9/18) of T3 tumors and 84.6% (11/13) of T4 erythroderma. Most T4 erythroderma were positive for Twist in dermal lymphocytes, with the strongest staining. Positive staining for c-myc was higher in T3/T4 lesions (29/31, 93.5%) than T1/T2 lesions (25/37, 67.6%, p < 0.05), with strongest staining in T3 tumors. Aberrant p53 expression was more common in T3/T4 lesions (8/31, 25.8%) than in T1/T2 lesions (2/37, 5.4%, p < 0.05). Twist mRNA was detected in all CD4+ T cells from SS patients but not in normal donors.

CONCLUSIONS

Increased Twist protein expression in advanced MF/SS lesions suggests that Twist expression may correlate with MF/SS stages.

Global evaluation of Eph receptors and ephrins in lung adenocarcinomas identifies EphA4 as an inhibitor of cell migration and invasion

The Eph family of receptors is the largest family of receptor tyrosine kinases, but it remains poorly studied in lung cancer. We aimed to systematically explore the human Eph receptors and their ligands, the ephrins, in lung adenocarcinoma. The prognostic impact of Eph receptor and ephrin gene expression was analyzed using 2 independent cohorts of lung adenocarcinoma. Gene expression profiles in lung adenocarcinoma compared with normal adjacent lung were studied in 3 independent cohorts and in cell lines. Gene expression profiles were validated with quantitative polymerase chain reaction (qPCR) and Western blotting in cell lines. Functional studies to assess the role of Eph receptor A4 (EphA4) were carried out in vitro. The biological effects of EphA4 in lung cancer cell lines were assayed following overexpression and knockdown. Of the 11 Eph receptors and 8 ephrins analyzed, only EphA4 and ephrin A1 gene expression were consistently associated with an improved outcome in patients with lung adenocarcinoma. Expression levels of EphA4 by microarray correlated well with expression levels measured by qPCR and Western blotting. EphA4 overexpression reduced cell migration and invasion but did not affect cell cycle, apoptosis, or drug sensitivity. Surprisingly, EphA4 was expressed at higher levels in cancer compared with non-cancer tissues and cell lines. EphA4 gene expression is associated with an improved outcome in patients with resected lung adenocarcinoma, possibly by affecting cancer cell migration and invasion.

Inducible expression and pathophysiologic functions of T-plastin in cutaneous T-cell lymphoma

A molecular feature of Sézary syndrome (SS) is the abnormal expression of T-plastin by malignant T cells. Herein, we investigated the molecular mechanisms involved in T-plastin synthesis and the functions of this actin-binding protein, with a special interest in chemoresistance and migration. We confirm the specific expression of T-plastin in peripheral blood lymphocytes (PBLs) from SS patients and its total absence in PBLs from patients with mycosis fungoides, inflammatory cutaneous or hematologic diseases, and from healthy volunteers. Only 3 of 4 SS patients did constitutively express T-plastin. To assess whether T-plastin expression was inducible, T-plastin-negative PBLs were stimulated by phorbol 12-myristate 13-acetate and ionomycin. Our results demonstrate that T-plastin synthesis was induced in negative PBLs from SS patients, other studied patients, and healthy volunteers. Both constitutive and calcium-induced T-plastin expression was down-regulated by calcineurin inhibitors and involved nuclear factor of activated T cells transcription pathway. Constitutive T-plastin expression in SS was associated with resistance to etoposide-induced apoptosis and cell migration toward chemokines (TARC/CCL17, IP-10). In conclusion, T-plastin is a marker restricted to malignant lymphocytes from SS patients and plays a role for cell survival and migration. This opens new strategies for the treatment of SS advanced stages.

Regulation of T-plastin expression by promoter hypomethylation in primary cutaneous T-cell lymphoma

T-plastin (PLS3) is an actin-bundling protein normally expressed in epithelial cells but absent in cells of hematopoietic origin. Aberrant PLS3 expression has been demonstrated in lymphocytes from Sézary syndrome (SS) patients and has been proposed as a biomarker for SS; however, the mechanism underlying dysregulation of PLS3 has not been determined. In this study, PLS3 mRNA expression was demonstrated in 21/35 (60%) SS patients and in 3/8 (38%) mycosis fungoides patients, all of whom had clonal blood involvement. No evidence for PLS3 mutations within coding or promoter regions was found, but significant hypomethylation of CpG dinucleotides 95-99 within the PLS3 CpG island was observed and this was restricted to the PLS3+ population. A polyclonal antibody specific to PLS3 was raised to examine coexpression of PLS3 with a panel of T-cell differentiation markers. All PLS3+ cells were CD3+CD4+ and CD26-, suggesting that loss of CD26 is consistently associated with gain of PLS3, whereas all other markers were distributed heterogeneously. However, a patient-specific TCR copy number assay also demonstrated heterogeneity in PLS3 expression in tumor cell populations. Importantly, our findings demonstrate PLS3 expression in the majority of SS patients and provide insight into the molecular regulation of PLS3 expression in CTCL.

Integrated genomic analysis of sézary syndrome

Sézary syndrome (SS) is a rare variant of primary cutaneous T-cell lymphoma. Little is known about the underlying pathogenesis of S. To address this issue, we used Affymetrix 10K SNP microarray to analyse 13 DNA samples isolated from 8 SS patients and qPCR with ABI TaqMan SNP genotyping assays for the validation of the SNP microarray results. In addition, we tested the impact of SNP loss of heterozygosity (LOH) identified in SS cases on the gene expression profiles of SS cases detected with Affymetrix GeneChip U133A. The results showed: (1) frequent SNP copy number change and LOH involving 1, 2p, 3, 4q, 5q, 6, 7p, 8, 9, 10, 11, 12q, 13, 14, 16q, 17, and 20, (2) reduced SNP copy number at FAT gene (4q35) in 75% of SS cases, and (3) the separation of all SS cases from normal control samples by SNP LOH gene clusters at chromosome regions of 9q31q34, 10p11q26, and 13q11q12. These findings provide some intriguing information for our current understanding of the molecular pathogenesis of this tumour and suggest the possibility of presence of functional SNP LOH in SS tumour cells.

Fragment based lead discovery of small molecule inhibitors for the EPHA4 receptor tyrosine kinase

The in silico identification, optimization and crystallographic characterization of a 6,7,8,9-tetrahydro-3H-pyrazolo[3,4-c]isoquinolin-1-amine scaffold as an inhibitor for the EPHA4 receptor tyrosine kinase is described. A database containing commercially available compounds was subjected to an in silico screening procedure which was focused on finding novel, EPHA4 hinge binding fragments. This resulted in the identification of 6,7,8,9-tetrahydro-3H-pyrazolo[3,4-c]isoquinolin-1-amine derivatives as EPHA4 inhibitors. Hit exploration yielded a compound with 2 μM (IC(50)) affinity for the EPHA4 receptor tyrosine kinase domain. Soaking experiments into a crystal of the EPHA4 kinase domain gave a 2.11Å X-ray structure of the EPHA4 - inhibitor complex, which confirmed the binding mode of the scaffold as proposed by the initial in silico work. The results underscore the strength of fragment based in silico screening as a tool for the discovery of novel lead compounds as small molecule kinase inhibitors.

Crystal structure of the EphA4 protein tyrosine kinase domain in the apo- and dasatinib-bound state

The Eph family of receptor tyrosine kinases regulates diverse cellular processes while the over-expression of a member of this family, EphA4, has been reported in a variety of malignant carcinomas. To gain insight into molecular mechanisms and to facilitate structure-based inhibitor design, we solved the crystal structure of the native EphA4 kinase domain in both the apo and dasatinib bound forms. Analysis of the two structures provides insight into structural features of inhibitor binding and revealed a hydrophobic back-pocket in the ATP- binding site of EphA4 which was previously unidentified. The structures suggest a route towards development of novel and specific inhibitors.

Regulatory T cells and immunodeficiency in mycosis fungoides and Sézary syndrome

Cutaneous T-cell lymphoma (CTCL) is the term for diseases characterized by primary accumulation of malignant T cells in the skin. Patients with the two predominant clinical forms of CTCL called mycosis fungoides (MF) and Sézary syndrome (SS) characteristically develop severe immunodeficiency during disease progression and consequently patients with advanced disease frequently die of infections and not from the tumor burden. For decades, it has been suspected that the malignant T cells actively drive the evolving immunodeficiency to avoid antitumor immunity, yet, the underlying mechanisms remain unclear. The identification of a subset of highly immunosuppressive regulatory T cells (Tregs) triggered a variety of studies investigating if MF and SS are malignant proliferations of Tregs but seemingly discordant findings have been reported. Here, we review the literature to clarify the role of Tregs in MF and SS and discuss the potential mechanisms driving the immunodeficiency.

Evolving insights in the pathogenesis and therapy of cutaneous T-cell lymphoma (mycosis fungoides and Sezary syndrome)

Cutaneous T-cell lymphomas (CTCL) are a heterogeneous group of malignancies derived from skin-homing T cells. The most common forms of CTCL are Mycosis Fungoides (MF) and Sezary Syndrome (SS). Accurate diagnosis remains a challenge due to the heterogeneity of presentation and the lack of highly characteristic immunophenotypical and genetic markers. Over the past decade molecular studies have improved our understanding of the biology of CTCL. The identification of gene expression differences between normal and malignant T-cells has led to promising new diagnostic and prognostic biomarkers that now need validation to be incorporated into clinical practice. These biomarkers may also provide insight into the mechanism of development of CTCL. Additionally, treatment options have expanded with the approval of new agents, such as histone deacetylase inhibitors. A better understanding of the cell biology, immunology and genetics underlying the development and progression of CTCL will allow the design of more rational treatment strategies for these malignancies. This review summarizes the clinical epidemiology, staging and natural history of MF and SS; discusses the immunopathogenesis of MF and the functional role of the malignant T-cells; and reviews the latest advances in MF and SS treatment.

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.

Increased androgen receptor transcription: a cause of castration-resistant prostate cancer and a possible therapeutic target

Few effective therapies exist for the treatment of castration-resistant prostate cancer (CRPC). Recent evidence suggests that CRPC may be caused by augmented androgen/androgen receptor (AR) signaling, generally involving AR overexpression. Aberrant androgen/AR signaling associated with AR overexpression also plays a key role in prostate carcinogenesis. Although AR overexpression could be attributed to gene amplification, only 10-20% of CRPCs exhibit AR gene amplification, and aberrant AR expression in the remaining instances of CRPC is thought to be attributed to transcriptional, translational, and post-translational mechanisms. Overexpression of AR at the protein level, as well as the mRNA level, has been found in CRPC, suggesting a key role for transcriptional regulation of AR expression. Since the analysis of the AR promoter region in the 1990s, several transcription factors have been reported to regulate AR transcription. In this review, we discuss the molecules involved in the control of AR gene expression, with emphasis on its transcriptional control by transcription factors in prostate cancer. We also consider the therapeutic potential of targeting AR expression.

Genomic loss of the putative tumor suppressor gene E2A in human lymphoma

The transcription factor E2A is essential for lymphocyte development. In this study, we describe a recurrent E2A gene deletion in at least 70% of patients with Sézary syndrome (SS), a subtype of T cell lymphoma. Loss of E2A results in enhanced proliferation and cell cycle progression via derepression of the protooncogene MYC and the cell cycle regulator CDK6. Furthermore, by examining the gene expression profile of SS cells after restoration of E2A expression, we identify several E2A-regulated genes that interfere with oncogenic signaling pathways, including the Ras pathway. Several of these genes are down-regulated or lost in primary SS tumor cells. These data demonstrate a tumor suppressor function of E2A in human lymphoid cells and could help to develop new treatment strategies for human lymphomas with altered E2A activity.

TWIST1 Gene: First Insights in Felis catus

TWIST1 is thought to be a novel oncogene. Understanding the molecular mechanisms regulating the TWIST1 gene expression profiles in tumor cells may give new insights regarding prognostic factors and novel therapeutic targets in veterinary oncology. In the present study we partially isolated the TWIST1 gene in Felis catus and performed comparative studies. Several primer combinations were used based on the alignments of homologous DNA sequences. After PCR amplification, three bands were obtained, purified and sequenced. Several bioinformatic tools were utilized to carry out the comparative studies. Higher similarity was found between the isolated TWIST1 gene in Felis catus and Homo sapiens (86%) than between Homo sapiens and Rattus norvegicus or Mus musculus (75%). Partial amino acid sequence showed no change in the four species analyzed. This confirmed that coding sequences presented high similarity (~96%) between man and cat. These results give the first insights regarding the TWIST1 gene in cat but further studies are required in order to establish, or not, its role in tumor formation and progression in veterinary oncology.

Epithelial to mesenchymal transition markers expressed in circulating tumour cells of early and metastatic breast cancer patients

Introduction

Epithelial to mesenchymal transition (EMT) is considered an essential process in the metastatic cascade. EMT is characterised by upregulation of vimentin, Twist, Snail, Slug and Sip1 among others. Metastasis is also associated with the presence of circulating tumour cells (CTCs) and disseminated tumour cells in the blood and bone marrow, respectively, of breast cancer patients, but the expression of EMT markers in these cells has not been reported so far.

Methods

The expression of Twist and vimentin in CTCs of 25 metastatic and 25 early breast cancer patients was investigated by using double-immunofluorescence experiments in isolated peripheral blood mononuclear cell cytospins using anti-cytokeratin (anti-CK) anti-mouse (A45-B/B3) and anti-Twist or anti-vimentin anti-rabbit antibodies.

Results

Among early breast cancer patients, vimentin-and Twist-expressing CK⁺ CTCs were identified in 77% and 73% of the patients, respectively, and in 100% of the patients with metastatic breast cancer for both markers (P = 0.004 and P = 0.037, respectively). Among patients with early disease, 56% and 53% of the CK⁺ CTCs were double-stained with vimentin and Twist, and the corresponding values for metastatic patients were 74% and 97%, respectively (P = 0.005 and P = 0.0001, respectively). The median expression of CK⁺vimentin⁺ and CK⁺Twist⁺ cells per patient in metastatic patients was 98% and 100%, and in an adjuvant chemotherapy setting the corresponding numbers were 56% and 40.6%, respectively. Triple-staining experiments revealed that all CK⁺Twist⁺ or CK⁺vimentin⁺ cells were also CD45^-, confirming their epithelial origin. Immunomagnetic separation of CTCs and triple-immunofluorescence with anti-CK/anti-Twist/anti-vimentin antibodies demonstrated that both mesenchymal markers could be coexpressed in the same CK⁺ cell, since 64% of the total identified CTCs were triple-stained. There was a significant correlation (P = 0.005) between the number of CTCs expressing Twist and vimentin within the same setting.

Conclusions

CTCs expressing Twist and vimentin, suggestive of EMT, are identified in patients with breast cancer. The high incidence of these cells in patients with metastatic disease compared to early stage breast cancer strongly supports the notion that EMT is involved in the metastatic potential of CTCs.

MicroRNA profiling reveals that miR-21, miR486 and miR-214 are upregulated and involved in cell survival in Sézary syndrome

Sézary syndrome (SS) is an incurable leukemic variant of cutaneous T-cell lymphoma and its pathogenesis is still unknown. Diagnosis/prognosis may strongly ameliorate the management of SS individuals. Here, we profiled the expression of 470 microRNAs (miRNAs) in a cohort of 22 SS patients, and we identified 45 miRNAs differentially expressed between SS and controls. Using predictive analysis, a list of 19 miRNAs, including miR-21, miR-214, miR-486, miR-18a, miR-342, miR-31 and let-7 members were also found. Moreover, we defined a signature of 14 miRNAs including again miR-21, potentially able to discriminate patients with unfavorable and favorable outcome. We validated our data for miR-21, miR-214 and miR-486 by qRT-PCR, including an additional set of array-independent SS cases. In addition, we also provide an in vitro evidence for a contribution of miR-214, miR-486 and miR-21 to apoptotic resistance of CTCL cell line.

TWIST1 is expressed in colorectal carcinomas and predicts patient survival

TWIST1 is a transcription factor that belongs to the family of basic helix-loop-helix proteins involved in epithelial-to-mesenchymal transition and invasion processes. The TWIST1 protein possesses oncogenic, drug-resistant, angiogenic and invasive properties, and has been related with several human tumors and other pathologies. Colorectal cancer is one of the tumors in which TWIST1 is over-expressed, but its involvement in the clinical outcome of the disease is still unclear. We tested, by RT-PCR, the expression levels of TWIST1 in normal and tumor paired-sample tissues from a series of 151 colorectal cancer patients, in order to investigate its prognostic value as a tumor marker. TWIST1 expression was restricted to tumor tissues (86.1%) and correlated with lymph node metastasis (LNM). Adjusted analysis showed that the expression levels of TWIST1 correlated with overall survival (OS) and disease-free survival (DFS). Importantly, TWIST1 expression levels predicted OS specifically at stages I and II. Moreover, patients with stage II tumors and high TWIST1 levels showed even shorter survival than patients with stage III tumors. These results suggest that TWIST1 expression levels could be a tumor indicator in stage II patients and help select patients at greater risk of poor prognosis who might benefit from adjuvant chemotherapy.

Histopathologic diagnosis of lymphomatous versus inflammatory erythroderma: a morphologic and phenotypic study on 47 skin biopsies

Erythroderma may be secondary to a cutaneous T-cell lymphoma (CTCL) and various other erythrodermic inflammatory dermatoses (EID), and their histopathologic distinction is often difficult. The aim of this study was to determine if morphological parameters, namely: the presence of b-catenin, and JunB (previously shown to be expressed by CTCL cells), the epidermal CD8:CD3 ratio, and CD30 expression may help in the histopathologic diagnosis of erythroderma, especially in differentiating CTCL and EID. We retrospectively reviewed a series of 47 skin biopsies from patients with erythroderma (18 CTCL and 29 EID). The diagnosis of each case was established using clinical, biological and histopathologic data. After a blind assessment of the hematoxylin--eosin--safran stained slides, a correct diagnosis of the underlying cause of erythroderma was made only in 31% of cases. A correct differential diagnosis between lymphoma and EID was done with certainty in 57% of cases. Various morphologic and phenotypic parameters were then recorded and we compared their frequency in the CTCL versus the EID group. With the exception of atypical lymphocytes, the moderate to high density of dermal infiltrates and Pautrier microabcesses, only found in CTCL, no morphologic parameter was found to be specific of CTCL, although single lymphocytes epidermotropism, telangiectasias, and slight lymphocytic dermal infiltrate were significantly more frequent in EID. A low (<10%) CD8:CD3 ratio in the epidermal lymphocytic infiltrate and dermal CD30+ lymphocytes were significantly more frequent in CTCL. JunB expression by lymphocytes was specific of CTCL, but was inconstant in our series (17%). We found β-catenin expression in a minority of cases from both the CTCL and EID groups. Among EID, dermal suprapapillary thinning was specific of psoriasis. Neutrophils exocytosis and edema of papillary dermis were significantly more frequent in psoriasis, and spongiosis was more frequent in eczema. In conclusion, few morphological and phenotypical parameters are helpful in making a differential diagnosis between erythrodermic CTCL and EID using paraffin embedded skin biopsies.

miRNA expression profiling of mycosis fungoides

MicroRNAs (miRNAs) are small RNA species that regulate gene expression post-transcriptionally and are aberrantly expressed in many malignancies including lymphoma. However, the role of miRNAs in the pathogenesis of T-cell lymphoid malignancies is poorly understood. Previously we examined the miRNA profile of Sézary syndrome (Sz), a leukemia of skin-homing memory T cells. In this study we determined the complete miRNome of mycosis fungoides (MF), the most common type of cutaneous T cell lymphoma. The miRNA profile of skin biopsies from 19 patients with tumor stage MF and 12 patients with benign inflammatory dermatoses (eczema and lichen planus) were compared by microarray analysis. We identified 49 miRNAs that are differentially expressed in tumor stage MF compared to benign inflammatory dermatoses using ANOVA analysis (P < 0.05, Benjamini-Hochberg corrected). The majority of the differentially expressed miRNAs (30/49) were up-regulated in tumor stage MF. The most significant differentially expressed were miR-155 and miR-92a (both up-regulated in tumor stage MF), while miR-93 showed the highest up-regulation in tumor stage MF with a fold difference of 5.8. Differential expression of a selection of these miRNAs was validated by miRNA-Q-PCR on additional test groups (tumors and controls). None of the miRNAs up-regulated in tumor stage MF was previously shown to be up-regulated in Sz, and only 2 of the 19 miRNAs down-regulated in tumor stage MF were also down-regulated in Sz. Taken together this report is the first describing the miRNA signature of tumor stage MF.

Genetic alterations in Sezary syndrome

Sezary syndrome (SS) is a rare form of cutaneous T-cell lymphoma characterized by erythroderma and the presence of Sezary cells in the skin, lymph nodes, and peripheral blood. Over the past few decades, cytogenetic and molecular cytogenetic findings have revealed many genetic alterations in patients with SS. The most frequent genetic lesions include monosomy 10, losses of 10q and 17p, gains of 8q24 and 17q, and diverse structural alterations involving these regions. Expression patterns in regions of genomic imbalance show that a large number of genes in SS are deregulated, and this might have a causative role in oncogenesis. Overall, chromosomal instability is characteristic of this lymphoma and related to a poor prognosis, but no specific abnormalities that may be directly involved in development of the disease have yet been found.

Deficiency of SATB1 expression in Sezary cells causes apoptosis resistance by regulating FasL/CD95L transcription

Sézary syndrome (SS) is an aggressive subtype of cutaneous T-cell lymphoma that is characterized by circulating leukemic Sézary cells. The accumulation of these malignant cells has been shown to be the result of the resistance to apoptosis, in particular, activation-induced cell death. However, the mechanism of apoptosis resistance remains unknown. By characterizing the gene transcription profiles of purified CD4(+)CD7(-) Sézary cells from patients with SS and cultured Sézary cells, it was found that Sézary cells are deficient in the expression of special AT-rich region binding protein 1 (SATB1), a key regulator of T-cell development and maturation. Retrovirus-mediated gene transduction revealed that SATB1 restoration in cultured Sézary cells (Hut78) triggered spontaneous cell death and sensitized Hut78 cells to activation-induced cell death, with associated activation of caspase 8 and caspase 3. Furthermore, endogenous expression of FasL in Sézary cells was increased in transcriptional and translational levels on restoration of SATB1 expression in cultured Sézary cells. These results suggest that deficiency in SATB1 expression in Sézary cells plays an important role in SS pathogenesis by causing apoptosis resistance. Thus, restoration of SATB1 expression may represent a potential molecular targeted therapy for SS, which does not have a cure at present.

Novel approach to gene expression profiling in Sézary syndrome

BACKGROUND

Microarray hybridization studies in Sézary syndrome (SS) have compared T lymphocytes from patients with cutaneous T-cell lymphoma with those of normal controls; a major limitation of this design is that significant inherent genetic variability of lymphocyte populations between individuals may produce differences in gene expression unrelated to disease state.

OBJECTIVE

The objective of this study was to minimize the heterogeneity of information derived from whole-genome expression analysis and to identify specific genetic differences between highly purified malignant and nonmalignant (control) T cells from the same patient with SS.

METHODS

Peripheral blood mononuclear cells were obtained from a patient with SS, stained with anti-T-cell receptor Vb (TCR-Vb) antibodies, and sorted by multiparameter flow cytometry. Malignant cells expressed the dominant TCR-Vb; control T cells lacked the dominant TCR-Vb but were otherwise phenotypically identical (CD3+CD4+CD45RO+). These cell populations were compared using the Illumina Inc. Sentrix Human-6 expression BeadChip system.

RESULTS

Transcriptome analysis using the J5 test, which was selected for data analysis based on an efficiency analysis of competing statistical methods, showed differential expression of 44 genes between the malignant and nonmalignant cell subsets. Promyelocytic leukaemia zinc finger protein (ZBTB16) was the most profoundly upregulated gene in the malignant cell population, while interferon regulatory factor 3 (IRF3) and interferon-induced protein 35 (IFI35), which are important elements of the cellular response to viral infection, were significantly downregulated.

CONCLUSIONS

The results of this study suggest the feasibility of this novel comparative approach to genomic profiling in SS. Using this method, we identified several differentially expressed genes and pathways not previously described in SS. While these findings require validation in larger studies, they may be important in SS pathogenesis.

Expression and function of the natural cytotoxicity receptor NKp46 on circulating malignant CD4+ T lymphocytes of Sézary syndrome patients

The natural cytotoxicity receptors NKp30, NKp44, and NKp46 were identified as activating receptors mainly expressed by natural killer (NK) lymphocytes. In this study we show that peripheral blood malignant CD4(+) T lymphocytes from patients with Sézary syndrome, an aggressive form of cutaneous T-cell lymphoma, express NKp46 at their cell surface. Although NKp46 does not behave as an independent functional receptor, its engagement provides a strong inhibiting signal on the malignant T lymphocyte CD3-induced proliferation. We show that this inhibition is correlated with a decreased phosphorylation of the CD3ζ chain associated with NKp46 and/or the TCR/CD3 complexes. Our results reveal that in addition to KIR3DL2/CD158k expression, NKp46 could represent an additional marker on the circulating malignant T lymphocytes of Sézary patients, where it displays an as yet unreported function of inhibitory co-receptor able to interfere with the processes governing their CD3-dependent proliferation.

Natural killer cell lymphoma shares strikingly similar molecular features with a group of non-hepatosplenic γδ T-cell lymphoma and is highly sensitive to a novel aurora kinase A inhibitor in vitro

Natural killer (NK) cell lymphomas/leukemias are rare neoplasms with an aggressive clinical behavior. The majority of the cases belong to extranodal NK/T-cell lymphoma, nasal type (ENKTL) in the current WHO classification scheme. Gene-expression profiling (GEP) of 21 ENKTL and NK-cell lymphoma/leukemia patients, 17 NK- and T-cell lines and 5 indolent NK-cell large-granular-lymphocytic proliferation was performed and compared with 125 peripheral T-cell lymphoma (PTCL) patients previously studied. The molecular classifier derived for ENKTL patients was comprised of 84 transcripts with the majority of them contributed by the neoplastic NK cells. The classifier also identified a set of γδ-PTCLs both in the ENKTL cases as well as in cases initially classified as PTCL-not otherwise specified. These γδ-PTCLs expressed transcripts associated with the T-cell receptor (TCR)/CD3 complex, suggesting T cell rather than NK-cell lineage. They were very similar to NK-cell tumors by GEP, but were distinct from cytotoxic (αβ)-PTCL and hepatosplenic T-cell lymphoma, indicating derivation from an ontogenically and functionally distinct subset of γδ T cells. They showed distinct expression of Vγ9, Vδ2 transcripts and were positive for TCRγ, but negative for TCRβ by immunohistochemistry. Targeted inhibition of two oncogenic pathways (AURKA and NOTCH-1) by small-molecular inhibitors induced significant growth arrest in NK-cell lines, thus providing a rationale for clinical trials of these inhibitors in NK-cell malignancies.

TrkC plays an essential role in breast tumor growth and metastasis

Tropomyosin-related kinase (Trk) C, a member of the Trk family of neurotrophin receptors, has been implicated in the growth and survival of human cancer tissues. Here, we report that TrkC is frequently overexpressed in human breast cancers and plays an essential role in tumor growth and metastasis. Ectopic expression of TrkC in non-malignant mammary epithelial cells suppressed anoikis, which correlated with activation of the Ras-mitogen-activated protein kinase and phosphatidylinositol-3-OH kinase (PI3K)/Akt pathways, and reduced expression of the metastatic regulator Twist. Furthermore, suppression of TrkC expression in highly metastatic mammary carcinoma cells inhibited their growth in vitro, as well as their ability to metastasize from the mammary gland to the lung in vivo. These results have identified TrkC as a critical regulator of breast cancer cell growth and metastasis.

MicroRNA expression in Sezary syndrome: identification, function, and diagnostic potential

MicroRNAs are commonly aberrantly expressed in many cancers. Very little is known of their role in T-cell lymphoma, however. We therefore elucidated the complete miRNome of purified T cells from 21 patients diagnosed with Sézary Syndrome (SzS), a rare aggressive primary cutaneous T-cell (CD4(+)) lymphoma. Unsupervised cluster analysis of microarray data revealed that the microRNA expression profile was distinct from CD4(+) T-cell controls and B-cell lymphomas. The majority (104 of 114) of SzS-associated microRNAs (P < .05) were down-regulated and their expression pattern was largely consistent with previously reported genomic copy number abnormalities and were found to be highly enriched (P < .001) for aberrantly expressed target genes. Levels of miR-223 distinguished SzS samples (n = 32) from healthy controls (n = 19) and patients with mycosis fungoides (n = 11) in more than 90% of samples. Furthermore, we demonstrate that the down-regulation of intronically encoded miR-342 plays a role in the pathogenesis of SzS by inhibiting apoptosis, and describe a novel mechanism of regulation for this microRNA via binding of miR-199a* to its host gene. We also provide the first in vivo evidence for down-regulation of the miR-17-92 cluster in malignancy and demonstrate that ectopic miR-17-5p expression increases apoptosis and decreases cell proliferation in SzS cells.

Twist modulates breast cancer stem cells by transcriptional regulation of CD24 expression

The cancer stem cell paradigm postulates that dysregulated tissue-specific stem cells or progenitor cells are precursors for cancer biogenesis. Consequently, identifying cancer stem cells is crucial to our understanding of cancer progression and for the development of novel therapeutic agents. In this study, we demonstrate that the overexpression of Twist in breast cells can promote the generation of a breast cancer stem cell phenotype characterized by the high expression of CD44, little or no expression of CD24, and increased aldehyde dehydrogenase 1 activity, independent of the epithelial-mesenchymal transition. In addition, Twist-overexpressing cells exhibit high efflux of Hoechst 33342 and Rhodamine 123 as a result of increased expression of ABCC1 (MRP1) transporters, a property of cancer stem cells. Moreover, we show that transient expression of Twist can induce the stem cell phenotype in multiple breast cell lines and that decreasing Twist expression by short hairpin RNA in Twist-overexpressing transgenic cell lines MCF-10A/Twist and MCF-7/Twist as well as in MDA-MB-231 partially reverses the stem cell molecular signature. Importantly, we show that inoculums of only 20 cells of the Twist-overexpressing CD44(+)/CD24(-/low) subpopulation are capable of forming tumors in the mammary fat pad of severe combined immunodeficient mice. Finally, with respect to mechanism, we provide data to indicate that Twist transcriptionally regulates CD24 expression in breast cancer cells. Taken together, our data demonstrate the direct involvement of Twist in generating a breast cancer stem cell phenotype through down-regulation of CD24 expression and independent of an epithelial-mesenchymal transition.

Eph receptors and ephrins in cancer: bidirectional signalling and beyond

The Eph receptor tyrosine kinases and their ephrin ligands have intriguing expression patterns in cancer cells and tumour blood vessels, which suggest important roles for their bidirectional signals in many aspects of cancer development and progression. Eph gene mutations probably also contribute to cancer pathogenesis. Eph receptors and ephrins have been shown to affect the growth, migration and invasion of cancer cells in culture as well as tumour growth, invasiveness, angiogenesis and metastasis in vivo. However, Eph signalling activities in cancer seem to be complex, and are characterized by puzzling dichotomies. Nevertheless, the Eph receptors are promising new therapeutic targets in cancer.

Activation of EphA receptors on CD4+CD45RO+ memory cells stimulates migration

We have demonstrated previously that binding of ephrin-A1 to EphA receptors on human CD4(+) and CD8(+) T cells stimulates migration. Two EphA receptors have been reported in T cells: EphA1 at the protein level and EphA4 at the mRNA level. In this study, we wanted to investigate the expression profile of these receptors in T cell subpopulations and to test if expression differences would affect the potential of cells to migrate upon ephrin-A1 binding. We have generated an anti-EphA4 mAb for expression analysis. Our data show that functional EphA4 is expressed on the cell surface of CD4(+) and CD8(+) T cells. In addition, EphA4 receptor expression is induced after overnight incubation in serum-free medium, in particular, on CD4(+)CD45RO(+) T cells. Migration of CD4(+) T cells in response to ephrin-A1 is observed for memory cells (CD45RO(+)) and much weaker for naïve cells (CD45RA(+)). A signaling complex associated with the EphA4 receptor has also been isolated and includes EphA1, the Src family kinases Fyn and Lck, Slp76, and Vav1. To conclude, T cells express EphA1 and EphA4 receptors. Expression differences of EphA4 are observed in subpopulations of CD4(+) T cells. This is related to the cell migration potential after ephrin-A1 binding.

Twist2 regulates CD7 expression and galectin-1-induced apoptosis in mature T-cells

In the periphery, a galectin-1 receptor, CD7, plays crucial roles in galectin-1-mediated apoptosis of activated T-cells as well as progression of T-lymphoma. Previously, we demonstrated that NF-kappaB downregulated CD7 gene expression through the p38 MAPK pathway in developing immature thymocytes. However, its regulatory pathway is not well understood in functional mature T-cells. Here, we show that CD7 expression was downregulated by Twist2 in Jurkat cells, a human acute T-cell lymphoma cell line, and in EL4 cells, a mature murine T-cell lymphoma cell line. Furthermore, ectopic expression of Twist2 in Jurkat cells reduced galectin-1-induced apoptosis. While full-length Twist2 decreased CD7 promoter activity, a C-terminal deletion form of Twist2 reversed its inhibition, suggesting an important role of the C-terminus in CD7 regulation. In addition, CD7 expression was enhanced by histone deacetylase inhibitors such as trichostatin A and sodium butyrate, which indicates that Twist2 might be one of candidate factors involved in histone deacetylation. Based on these results, we conclude that upregulation of Twist2 increases the resistance to galectin-1-mediated-apoptosis, which may have significant implications for the progression of some T-cells into tumors such as Sezary cells.

Castration resistance of prostate cancer cells caused by castration-induced oxidative stress through Twist1 and androgen receptor overexpression

There are few successful therapies for castration-resistant prostate cancer (CRPC). Recently, CRPC has been thought to result from augmented androgen/androgen receptor (AR) signaling pathway, for most of which AR overexpression has been observed. In this study, Twist1, a member of basic helix-loop-helix transcription factors as well as AR was upregulated in response to hydrogen peroxide, and the response to which was abolished by an addition of N-acetyl-L-cysteine and Twist1 knockdown. In addition, castration-resistant LNCaP derivatives and hydrogen peroxide-resistant LNCaP derivatives exhibited a similar phenotype to each other. Then, both castration and AR knockdown increased intracellular reactive oxygen species level. Moreover, Twist1 was shown to regulate AR expression through binding to E-boxes in AR promoter region. Silencing of Twist1 suppressed cell growth of AR-expressing LNCaP cells as well as castration-resistant LNCaP derivatives by inducing cell-cycle arrest at G1 phase and cellular apoptosis. These findings indicated that castration-induced oxidative stress may promote AR overexpression through Twist1 overexpression, which could result in a gain of castration resistance. Modulation of castration-induced oxidative stress or Twist1/AR signaling might be a useful strategy for developing a novel therapeutics in prostate cancer, even in CRPC, which remains dependent on AR signaling by overexpressing AR.