Abnormal protein tyrosine kinase gene expression during melanoma progression and metastasis

Enhanced EphB2-Specific Peptide Inhibitors through Stabilization of Polyproline II Helical Structure

Ephrin (Eph) receptors are the largest family of receptor tyrosine kinases. Interactions between Eph receptors and their membrane-bound ephrin protein ligands are associated with many developmental processes as well as various cancers and neurodegenerative diseases. With significant crosstalk between different Eph receptors and ephrin ligands, there is an urgent need for high-affinity ligands that bind specifically to individual Eph receptors to interrogate and modulate their functions. Here, we describe the rational development of potent EphB2 receptor inhibitors derived from the EphB2 receptor-specific SNEW peptide. To improve inhibitory potency, we evaluated 20+ cross-linkers with the goal of spanning and stabilizing a single polyproline II helical turn observed when SNEW binds to the EphB2 receptor. Of the cross-linkers evaluated, an 11-atom cross-linker, composed of a rigid 2,7-dimethylnaphthyl moiety between two cysteine residues, was found to yield the most potent inhibitor. Analysis of the cyclized region of this peptide by NMR and molecular dynamics simulations suggests that cross-linking stabilizes the receptor-bound polyproline II helix structure observed in the receptor-peptide complex. Cross-linked SNEW variants retained binding specificity for EphB2 and showed cross-linker-dependent resistance to trypsin proteolysis. Beyond the discovery of more potent EphB2 receptor inhibitors, these studies illustrate a novel cyclization approach with potential to stabilize polyproline II helical structure in various peptides for specific targeting of the myriad protein-protein interactions (PPIs) mediated by polyproline II helices.

Oncogenic functions and therapeutic targeting of EphA2 in cancer

More than 25 years of research and preclinical validation have defined EphA2 receptor tyrosine kinase as a promising molecular target for clinical translation in cancer treatment. Molecular, genetic, biochemical, and pharmacological targeting strategies have been extensively tested in vitro and in vivo, and drugs like dasatinib, initially designed to target SRC family kinases, have been found to also target EphA2 activity. Other small molecules, therapeutic targeting antibodies, and peptide-drug conjugates are being tested, and more recently, approaches harnessing antitumor immunity against EphA2-expressing cancer cells have emerged as a promising strategy. This review will summarize preclinical studies supporting the oncogenic role of EphA2 in breast cancer, lung cancer, glioblastoma, and melanoma, while delineating the differing roles of canonical and noncanonical EphA2 signaling in each setting. This review also summarizes completed and ongoing clinical trials, highlighting the promise and challenges of targeting EphA2 in cancer.

EphA2: A promising therapeutic target in breast cancer

Ephrin type-A receptor 2 (EphA2), a receptor tyrosine kinase, is overexpressed in human breast cancers often linked to poor patient prognosis. Accumulating evidence demonstrates that EphA2 plays important roles in several critical processes associated with malignant breast progression, such as proliferation, survival, migration, invasion, drug resistance, metastasis, and angiogenesis. As its inhibition through multiple approaches can inhibit the growth of breast cancer and restore drug sensitivity, EphA2 has become a promising therapeutic target for breast cancer treatment. Here, we summarize the expression, functions, mechanisms of action, and regulation of EphA2 in breast cancer. We also list the potential therapeutic strategies targeting EphA2. Furthermore, we discuss the future directions of studying EphA2 in breast cancer.

Neural activities are unfavorable for the prognosis of ovarian cancer through mRNA expression analysis

Aim: Ovarian cancer (OC) is the leading lethal gynecological cancer in women worldwide. Understanding the molecular mechanism of OC is very important for the identification of highly sensitive biomarkers for its prognosis. Methodology: We detected prognostic-related mRNA of OC in OncoLnc database. The main features between the unfavorable and favorable prognostic OC mRNAs were analyzed and Kyoto Encyclopedia of Genes and Genomes pathway enrichment as well as correlation analysis was conducted in our study. Conclusion: Our findings suggest that neural activities can promote OC progression, indicating poor prognosis, among which axon guidance functions most significantly govern the main neural activities, followed by neurogenesis and angiogenesis. Four neural genes (NTN1, UNC5B, EFNB2 and EFNA5) could serve as promising biomarkers and therapeutic targets for precision medicine to treat OC patients.

EphA3 inhibits migration and invasion of esophageal cancer cells by activating the mesenchymal‑epithelial transition process

Eph receptor tyrosine kinases are critical for cell‑cell communication during normal and oncogenic development. Eph receptor A3 (EphA3) expression is associated with tumor promotion in certain types of cancer; however, it acts as a tumor suppressor in others. The expression levels of EphA3 and its effects on tumor progression in esophageal squamous cell carcinoma (ESCC) cell lines were determined using reverse transcription‑quantitative polymerase chain reaction analysis and a Transwell invasion assay. The present study demonstrated that EphA3 expression was decreased in ESCC tissues and cell lines. Treatment with the DNA methylation inhibitor 5‑aza‑2'‑deoxycytidine increased the mRNA expression levels of EphA3 in the ESCC cell lines KYSE510 and KYSE30. In addition, overexpression of EphA3 in KYSE450 and KYSE510 cells inhibited cell migration and invasion. EphA3 overexpression also decreased RhoA GTPase. Furthermore, EphA3 overexpression induced mesenchymal‑epithelial transition, as demonstrated by epithelial‑like morphological alterations, increased expression of epithelial proteins (E‑cadherin and the tight junction protein 1 zonula occludens‑1) and decreased expression of mesenchymal proteins (Vimentin, N‑cadherin and Snail). Conversely, silencing EphA3 in KYSE410 cells triggered epithelial‑mesenchymal transition, and promoted cell migration and invasion. These results suggested that EphA3 may serve a tumor‑suppressor role in ESCC.

Comparative oncogenomics identifies tyrosine kinase FES as a tumor suppressor in melanoma

Identification and functional validation of oncogenic drivers are essential steps toward advancing cancer precision medicine. Here, we have presented a comprehensive analysis of the somatic genomic landscape of the widely used BRAFV600E- and NRASQ61K-driven mouse models of melanoma. By integrating the data with publically available genomic, epigenomic, and transcriptomic information from human clinical samples, we confirmed the importance of several genes and pathways previously implicated in human melanoma, including the tumor-suppressor genes phosphatase and tensin homolog (PTEN), cyclin dependent kinase inhibitor 2A (CDKN2A), LKB1, and others. Importantly, this approach also identified additional putative melanoma drivers with prognostic and therapeutic relevance. Surprisingly, one of these genes encodes the tyrosine kinase FES. Whereas FES is highly expressed in normal human melanocytes, FES expression is strongly decreased in over 30% of human melanomas. This downregulation correlates with poor overall survival. Correspondingly, engineered deletion of Fes accelerated tumor progression in a BRAFV600E-driven mouse model of melanoma. Together, these data implicate FES as a driver of melanoma progression and demonstrate the potential of cross-species oncogenomic approaches combined with mouse modeling to uncover impactful mutations and oncogenic driver alleles with clinical importance in the treatment of human cancer.

Immunohistochemical Expression of Vascular Endothelial Growth Factor (VEGF) and C-KIT in Cutaneous Melanocytic Lesions

Vascular endothelial growth factor (VEGF) and C-KIT are involved in tumor progression in several human neoplasms. The aim of the present study has been to investigate their immunohistochemical expression in melanocytic lesions. We examined 11 compound nevi, 12 dysplastic nevi, and 18 melanomas. Immunostaining for VEGF was observed only in melanomas; c-kit expression was detected in melanomas (higher in radial than in vertical growth phase) and in nevi (predominantly in the junctional component). Our data indicate that assessment of VEGF expression might aid in the differential diagnosis between dysplastic nevi and melanomas. Moreover, VEGF might be a candidate for targeted therapy. The loss of c-kit expression might contribute to melanoma progression.

Negative HER2/neu amplification using immunohistochemistry and chromogenic in situ hybridization techniques in skin melanoma cases

BACKGROUND

This study was performed to evaluate the amplification of HER-2/neu in patients with melanoma.

MATERIALS AND METHODS

Amplification of HER-2/neu was evaluated in a group of patients with melanoma, referred to two referral centers in Tehran, using immunohistochemistry (IHC) and chromogenic in situ hybridization (CISH) techniques.

RESULTS

Forty patients with mean age 57.9±19.5 years were enrolled in this study. The most frequent type of melanoma was acral, while lower limbs were the most frequent sites. The amplification of HER2/ neu was negative in 97.5% of patients with IHC and in 100% of patients with CISH technique. Only one case (2.5%) shows weak positive staining (+2) in IHC method. Fifty five percent of melanoma was ulcerative, and the most common stages of tumors were stages 4b and 3b. More than 47% of cases were in Clark level III, while the mean of Breslow thickness was 3.56±2.87 mm. The stage of the case that showed weakly positive staining (2+) in IHC was 4b.

CONCLUSIONS

The amplification of HER2/neu biomarker was negative in patients with melanoma, using both CISH and IHC techniques.

Pleural mesothelial cells in pleural and lung diseases

During development, the mesoderm maintains a complex relationship with the developing endoderm giving rise to the mature lung. Pleural mesothelial cells (PMCs) derived from the mesoderm play a key role during the development of the lung. The pleural mesothelium differentiates to give rise to the endothelium and smooth muscle cells via epithelial-to-mesenchymal transition (EMT). An aberrant recapitulation of such developmental pathways can play an important role in the pathogenesis of disease processes such as idiopathic pulmonary fibrosis (IPF). The PMC is the central component of the immune responses of the pleura. When exposed to noxious stimuli, it demonstrates innate immune responses such as Toll-like receptor (TLR) recognition of pathogen associated molecular patterns as well as causes the release of several cytokines to activate adaptive immune responses. Development of pleural effusions occurs due to an imbalance in the dynamic interaction between junctional proteins, n-cadherin and β-catenin, and phosphorylation of adherens junctions between PMCs, which is caused in part by vascular endothelial growth factor (VEGF) released by PMCs. PMCs play an important role in defense mechanisms against bacterial and mycobacterial pleural infections, and in pathogenesis of malignant pleural effusion, asbestos related pleural disease and malignant pleural mesothelioma. PMCs also play a key role in the resolution of inflammation, which can occur with or without fibrosis. Fibrosis occurs as a result of disordered fibrin turnover and due to the effects of cytokines such as transforming growth factor-β, platelet-derived growth factor (PDGF), and basic fibroblast growth factor; which are released by PMCs. Recent studies have demonstrated a role for PMCs in the pathogenesis of IPF suggesting their potential as a cellular biomarker of disease activity and as a possible therapeutic target. Pleural-based therapies targeting PMCs for treatment of IPF and other lung diseases need further exploration.

EphA2 Is a Therapy Target in EphA2-Positive Leukemias but Is Not Essential for Normal Hematopoiesis or Leukemia

Members of the Eph family of receptor tyrosine kinases and their membrane bound ephrin ligands have been shown to play critical roles in many developmental processes and more recently have been implicated in both normal and pathological processes in post-embryonic tissues. In particular, expression studies of Eph receptors and limited functional studies have demonstrated a role for the Eph/ephrin system in hematopoiesis and leukemogenesis. In particular, EphA2 was reported on hematopoietic stem cells and stromal cells. There are also reports of EphA2 expression in many different types of malignancies including leukemia, however there is a lack of knowledge in understanding the role of EphA2 in hematopoiesis and leukemogenesis. We explored the role of EphA2 in hematopoiesis by analyzing wild type and EphA2 knockout mice. Mature, differentiated cells, progenitors and hematopoietic stem cells derived from knockout and control mice were analyzed and no significant abnormality was detected. These studies showed that EphA2 does not have an obligatory role in normal hematopoiesis. Comparative studies using EphA2-negative MLL-AF9 leukemias derived from EphA2-knockout animals showed that there was no detectable functional role for EphA2 in the initiation or progression of the leukemic process. However, expression of EphA2 in leukemias initiated by MLL-AF9 suggested that this protein might be a possible therapy target in this type of leukemia. We showed that treatment with EphA2 monoclonal antibody IF7 alone had no effect on tumorigenicity and latency of the MLL-AF9 leukemias, while targeting of EphA2 using EphA2 monoclonal antibody with a radioactive payload significantly impaired the leukemic process. Altogether, these results identify EphA2 as a potential radio-therapeutic target in leukemias with MLL translocation.

EphA3 biology and cancer

Eph receptor tyrosine kinases control cell-cell interactions during normal and oncogenic development, and are implicated in a range of processes including angiogenesis, stem cell maintenance and metastasis. They are thus of great interest as targets for cancer therapy. EphA3, originally isolated from leukemic and melanoma cells, is presently one of the most promising therapeutic targets, with multiple tumor-promoting roles in a variety of cancer types. This review focuses on EphA3, its functions in controlling cellular behavior, both in normal and pathological development, and most particularly in cancer.

Dual-modality micro-positron emission tomography/computed tomography and near-infrared fluorescence imaging of EphB4 in orthotopic glioblastoma xenograft models

PURPOSE

In glioblastoma, EphB4 receptors, a member of the largest family of receptor tyrosine kinases, are overexpressed in both tumor cells and angiogenic blood vessels. The purpose of this study was to examine whether the EphB4-binding peptide TNYL-RAW labeled with both (64)Cu and near-infrared fluorescence dye Cy5.5 could be used as a molecular imaging agent for dual-modality positron emission tomography/computed tomography [PET/CT] and optical imaging of human glioblastoma in orthotopic brain tumor models.

MATERIALS AND METHODS

TNYL-RAW was conjugated to Cy5.5 and the radiometal chelator 1,4,7,10-tetraazadodecane-N,N',N″,N‴-tetraacetic acid. The conjugate was then labeled with (64)Cu for in vitro binding and in vivo dual μPET/CT and optical imaging studies in nude mice implanted with EphB4-expressing U251 and EphB4-negative U87 human glioblastoma cells. Tumors and brains were removed at the end of the imaging sessions for immunohistochemical staining and fluorescence microscopic examinations.

RESULTS

μPET/CT and near-infrared optical imaging clearly showed specific uptake of the dual-labeled TNYL-RAW peptide in both U251 and U87 tumors in the brains of the nude mice after intravenous injection of the peptide. In U251 tumors, the Cy5.5-labeled peptide colocalized with both tumor blood vessels and tumor cells; in U87 tumors, the tracer colocalized only with tumor blood vessels, not with tumor cells.

CONCLUSIONS

Dual-labeled EphB4-specific peptide could be used as a noninvasive molecular imaging agent for PET/CT and optical imaging of glioblastoma owing to its ability to bind to both EphB4-expressing angiogenic blood vessels and EphB4-expressing tumor cells.

Eph receptors and ephrins as targets for cancer therapy

Eph receptor tyrosine kinases and their ephrin ligands are involved in various signalling pathways and mediate critical steps of a wide variety of physiological and pathological processes. Increasing experimental evidence demonstrates that both Eph receptor and ephrin ligands are overexpressed in a number of human tumours, and are associated with tumour growth, invasiveness and metastasis. In this regard, the Eph/ephrin system provides the foundation for potentially exciting new targets for anticancer therapies for Eph-expressing tumours. The purpose of this review is to outline current advances in the role of Eph receptors and ephrin ligands in cancer, and to discuss novel therapeutic approaches of anticancer therapies.

Melanoma stem cells and metastasis: mimicking hematopoietic cell trafficking?

Malignant melanoma is a highly metastatic cancer that bears responsibility for the majority of skin cancer-related deaths. Amidst the research efforts to better understand melanoma progression, there has been increasing evidence that hints at a role for a subpopulation of virulent cancer cells, termed malignant melanoma stem or initiating cells (MMICs), in metastasis formation. MMICs are characterized by their preferential ability to initiate and propagate tumor growth and their selective capacity for self-renewal and differentiation into less tumorigenic melanoma cells. The frequency of MMICs has been shown to correlate with poor clinical prognosis in melanoma. In addition, MMICs are enriched among circulating tumor cells in the peripheral blood of cancer patients, suggesting that MMICs may be a critical factor in the metastatic cascade. Although these links exist between MMICs and metastatic disease, the mechanisms by which MMICs may advance metastatic progression are only beginning to be elucidated. Recent studies have shown that MMICs express molecules critical for hematopoietic cell maintenance and trafficking, providing a possible explanation for how circulating MMICs could drive melanoma dissemination. We therefore propose that MMICs might fuel melanoma metastasis by exploiting homing mechanisms commonly utilized by hematopoietic cells. Here we review the biological properties of MMICs and the existing literature on their metastatic potential. We will discuss possible mechanisms by which MMICs might initiate metastases in the context of established knowledge of cancer stem cells in other cancers and of hematopoietic homing molecules, with a particular focus on selectins, integrins, chemokines and chemokine receptors known to be expressed by melanoma cells. Biological understanding of how these molecules might be utilized by MMICs to propel the metastatic cascade could critically impact the development of more effective therapies for advanced disease.

Targeted delivery of let-7a microRNA encapsulated ephrin-A1 conjugated liposomal nanoparticles inhibit tumor growth in lung cancer

MicroRNAs (miRs) are small noncoding RNA sequences that negatively regulate the expression of target genes by posttranscriptional repression. miRs are dysregulated in various diseases, including cancer. let-7a miR, an antioncogenic miR, is downregulated in lung cancers. Our earlier studies demonstrated that let-7a miR inhibits tumor growth in malignant pleural mesothelioma (MPM) and could be a potential therapeutic against lung cancer. EphA2 (ephrin type-A receptor 2) tyrosine kinase is overexpressed in most cancer cells, including MPM and non-small-cell lung cancer (NSCLC) cells. Ephrin-A1, a specific ligand of the EphA2 receptor, inhibits cell proliferation and migration. In this study, to enhance the delivery of miR, the miRs were encapsulated in the DOTAP (N-[1-(2.3-dioleoyloxy)propyl]-N,N,N-trimethyl ammonium)/Cholesterol/DSPE (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[cyanur(polyethylene glycol)-2000])-PEG (polyethylene glycol)-cyanur liposomal nanoparticles (LNP) and ephrin-A1 was conjugated on the surface of LNP to target receptor EphA2 on lung cancer cells. The LNP with an average diameter of 100 nm showed high stability, low cytotoxicity, and high loading efficiency of precursor let-7a miR and ephrin-A1. The ephrin-A1 conjugated LNP (ephrin-A1–LNP) and let-7a miR encapsulated LNP (miR–LNP) showed improved transfection efficiency against MPM and NSCLC. The effectiveness of targeted delivery of let-7a miR encapsulated ephrin-A1 conjugated LNP (miR–ephrin-A1–LNP) was determined on MPM and NSCLC tumor growth in vitro. miR–ephrin-A1–LNP significantly increased the delivery of let-7a miR in lung cancer cells when compared with free let-7a miR. In addition, the expression of target gene Ras was significantly repressed following miR–ephrin-A1–LNP treatment. Furthermore, the miR–ephrin-A1–LNP complex significantly inhibited MPM and NSCLC proliferation, migration, and tumor growth. Our results demonstrate that the engineered miR–ephrin-A1–LNP complex is an effective carrier for the targeted delivery of small RNA molecules to lung cancer cells. This could be a potential therapeutic approach against tumors overexpressing the EphA2 receptor.

HER2 as a promising target for cytotoxicity T cells in human melanoma therapy

Anti-HER2/neu antibody therapy has been reported to mediate tumor regression of HER2/ neu(+) tumors. Here we demonstrated the expression of HER2 in a wide range of human melanoma cells including a primary culture and seven cell lines, and we further investigated whether HER2 could be served as a target for T cell mediated immunotherapy of human melanoma. Specific cytolytic activity of activated T cells (ATC) armed with anti-CD3 x anti-HER2 bispecific antibody (HER2Bi-Ab) against Malme-3M-luc cells was evaluated by bioluminescent signal generated by luciferase reporter which did not alter HER2 expression or proliferation ability of Malme-3M cells. Contrast with unarmed ATC, increased cytotoxic activity of HER2Bi-armed ATC against Malme-3M-luc cells was observed at effector/target (E/T) ratios of 1:1, 5:1, and 20:1. Moreover, HER2Bi-armed ATC expressed higher level of activation marker CD69 and secreted significantly higher level of IFN-γ than unarmed ATC counterpart at the E/T ratio of 20:1. In addition, compared with anti-HER2 mAb (Herceptin®) or unarmed ATC, HER2Bi-armed ATC showed remarkable suppression effect on Malme-3M-luc tumor cells. Furthermore, in melanoma tumor cell xenograft mice, infusion of HER2Bi-armed ATC successfully inhibited the growth of melanoma tumors. The anti-tumor effect of HER2Bi-armed ATC may provide a promising immunotherapy for melanoma in the future.

Eph-dependent cell-cell adhesion and segregation in development and cancer

Numerous studies attest to essential roles for Eph receptors and their ephrin ligands in controlling cell positioning and tissue patterning during normal and oncogenic development. These studies suggest multiple, sometimes contradictory, functions of Eph-ephrin signalling, which under different conditions can promote either spreading and cell-cell adhesion or cytoskeletal collapse, cell rounding, de-adhesion and cell-cell segregation. A principle determinant of the balance between these two opposing responses is the degree of receptor/ligand clustering and activation. This equilibrium is likely altered in cancers and modulated by somatic mutations of key Eph family members that have emerged as candidate cancer markers in recent profiling studies. In addition, cross-talk amongst Ephs and with other signalling pathways significantly modulates cell-cell adhesion, both between and within Eph- and ephrin-expressing cell populations. This review summarises our current understanding of how Eph receptors control cell adhesion and morphology, and presents examples demonstrating the importance of these events in normal development and cancer.

Delineating chromosomal breakpoints in radiation-induced papillary thyroid cancer

Recurrent translocations are well known hallmarks of many human solid tumors and hematological disorders, where patient- and breakpoint-specific information may facilitate prognostication and individualized therapy. In thyroid carcinomas, the proto-oncogenes RET and NTRK1 are often found to be activated through chromosomal rearrangements. However, many sporadic tumors and papillary thyroid carcinomas (PTCs) arising in patients with a history of exposure to elevated levels of ionizing irradiation do not carry these known abnormalities. We developed a rapid scheme to screen tumor cell metaphase spreads and identify candidate genes of tumorigenesis and neoplastic progression for subsequent functional studies. Using a series of overnight fluorescence in situ hybridization (FISH) experiments with pools comprised of bacterial artificial chromosome (BAC) clones, it now becomes possible to rapidly refine breakpoint maps and, within one week, progress from the low resolution Spectral Karyotyping (SKY) maps or Giemsa-banding (G-banding) karyotypes to fully integrated, high resolution physical maps including a list of candiate genes in the critical regions.

Clinicopathological significance and prognostic value of EphA3 and CD133 expression in colorectal carcinoma

AIMS

To investigate clinicopathological significance and prognostic implications of EphA3, CD133 and Ki-67 expression in colorectal cancer.

METHODS

EphA3, CD133 and Ki-67 expression was assessed in 201 cases of paraffin-embedded colorectal carcinoma and 60 cases of distal normal mucosal tissue by immunohistochemistry. Medical records were reviewed and clinicopathological analysis was performed. The differential expression of EphA3 and CD133 protein was detected in 20 cases of fresh resected colorectal carcinoma and 20 cases of matched normal mucosal tissue adjacent to the carcinoma by western blot.

RESULTS

The expression of EphA3 and CD133 in carcinoma was significantly higher than that in normal mucosal tissue (p=0.008; p=0.004). EphA3 and CD133 were positively correlated with tumour size (p=0.029; p=0.017), histological grade (all p=0.001), infiltrative depth (all p=0.00), lymph node metastasis (all p=0.00), distant metastasis (p=0.017; p=0.030) and TNM stage (all p=0.001). Patients with high expression of EphA3 and CD133 had the lowest survival (all p=0.001) (median survival time of EphA3 positive and negative cases: 34.0 and 72.0 months; median survival time of CD133 positive and negative cases: 34.0 and 77.0 months). Multivariate survival analysis showed that EphA3 and CD133 expression was correlated significantly with shortened survival in patients with colorectal cancer (Cox regression: p=0.001, HR=4.722, 95% CI 2.667 to 8.361; p=0.001, HR=5.224, 95% CI 2.622 to 10.405). EphA3, CD133 and Ki-67 expression in colorectal cancer had positive correlations with each other (all p=0.001).

CONCLUSIONS

EphA3 and CD133 may play an important role in the development and progression of tumours, and thus become useful indicators for clinical assessment of tumour biological behaviour and prognosis in patients with colorectal carcinoma.

Receptor tyrosine kinases and their activation in melanoma

Receptor tyrosine kinases (RTKs) and their downstream signalling pathways have long been hypothesized to play key roles in melanoma development. A decade ago, evidence was derived largely from animal models, RTK expression studies and detection of activated RAS isoforms in a small fraction of melanomas. Predictions that overexpression of specific RTKs implied increased kinase activity and that some RTKs would show activating mutations in melanoma were largely untested. However, technological advances including rapid gene sequencing, siRNA methods and phospho-RTK arrays now give a more complete picture. Mutated forms of RTK genes including KIT, ERBB4, the EPH and FGFR families and others are known in melanoma. Additional over- or underexpressed RTKs and also protein tyrosine phosphatases (PTPs) have been reported, and activities measured. Complex interactions between RTKs and PTPs are implicated in the abnormal signalling driving aberrant growth and survival in malignant melanocytes, and indeed in normal melanocytic signalling including the response to ultraviolet radiation. Kinases are considered druggable targets, so characterization of global RTK activity in melanoma should assist the rational development of tyrosine kinase inhibitors for clinical use.

c-RET molecule in malignant melanoma from oncogenic RET-carrying transgenic mice and human cell lines

Malignant melanoma is one of the most aggressive cancers and its incidence worldwide has been increasing at a greater rate than that of any other cancer. We previously reported that constitutively activated RFP-RET-carrying transgenic mice (RET-mice) spontaneously develop malignant melanoma. In this study, we showed that expression levels of intrinsic c-Ret, glial cell line-derived neurotrophic factor (Gdnf) and Gdnf receptor alpha 1 (Gfra1) transcripts in malignant melanomas from RET-transgenic mice were significantly upregulated compared with those in benign melanocytic tumors. These results suggest that not only introduced oncogenic RET but also intrinsic c-Ret/Gdnf are involved in murine melanomagenesis in RET-mice. We then showed that c-RET and GDNF transcript expression levels in human malignant melanoma cell lines (HM3KO and MNT-1) were higher than those in primary cultured normal human epithelial melanocytes (NHEM), while GFRa1 transcript expression levels were comparable among NHEM, HM3KO and MNT-1. We next showed c-RET and GFRa1 protein expression in HM3KO cells and GDNF-mediated increased levels of their phosphorylated c-RET tyrosine kinase and signal transduction molecules (ERK and AKT) sited potentially downstream of c-RET. Taken together with the finding of augmented proliferation of HM3KO cells after GDNF stimulation, our results suggest that GDNF-mediated c-RET kinase activation is associated with the pathogenesis of malignant melanoma.

The angiogenetic pathway in malignant pleural effusions: Pathogenetic and therapeutic implications

Increased permeability of the pleural microvasculature is generally attributed to the substances that are released in inflammatory and malignant pleural effusions, although the exact pathogenetic mechanisms of malignant pleural effusions are unclear. Current therapies used to prevent the re-accumulation of pleural fluid and relieve symptoms are of variable efficacy and may cause serious adverse effects. Understanding the mechanisms of fluid accumulation would hopefully permit the development of more specific, effective and safer treatment modalities. Angiogenesis, pleural vascular increased permeability and inflammation are considered central to the pathogenesis of malignant pleural effusions. Vascular endothelial growth factor (VEGF) is a member of the VEGF/platelet-derived factor gene family and consists of at least six isoforms. Since it was shown that VEGF contributes to the formation of malignant pleural effusions, there have been some attempts to implicate, therapeutically, this finding using different molecules (ZD6474, PTK 787 and bevacizumab). However, the role of the biological axis of VEGF and angiopoietins needs further investigation in both the pathogenesis and the treatment of malignant pleural effusion. In both non-small-cell lung carcinoma and breast cancer, it has been shown that the ligand for CXCR4, CXCL12 or SDF-1α, exhibited peak levels of expression in organs that were the preferred destination for their respective metastases. Recent findings imply that new therapeutic strategies aimed at blocking the SDF-1-CXCR4 axis may have significant applications for patients by modulating the trafficking of hemato/lymphopoietic cells and inhibiting the metastatic behavior of tumor cells as well. The purpose of this report is to review novel pathogenetic and therapeutic implications regarding the angiogenetic pathways in malignant pleural effusions.

EphA2 as a promoter of melanoma tumorigenicity

The greatest health threat from malignant melanoma is death due to metastatic disease. Consequently, the identification of markers predictive of metastatic disease is essential for identifying new therapeutic targets. EphA2, a protein tyrosine kinase receptor commonly expressed in epithelial cells, has been found to be overexpressed and constitutively active in melanoma tumor cells having a metastatic phenotype as characterized by increased invasion, proliferation and vasculogenic mimicry (VM). Based on this observation, we hypothesized that increased expression of EphA2 by melanoma tumor cells could promote these characteristics of a metastatic phenotype in addition to promoting tumorigenicity as a whole. We analyzed a panel of human melanoma tumor cell lines derived from patient tissues classified as primary (either radial growth phase or vertical growth phase) and/or metastatic for the expression of EphA2 and found a correlation between increased EphA2 expression and metastatic potential. Experiments using the most metastatic of the human melanoma cell lines demonstrated that downregulation of EphA2 results in a significant decrease in invasion, proliferation, clonogenicity and VM in vitro, in addition to suppressed tumorigenicity in an orthotopic mouse model. Lastly, utilization of a human phospho-kinase array revealed increased phosphorylation of several different protein kinases involved in mediating various aspects of cellular proliferation. To the best of our knowledge these results provide the first direct in vivo evidence demonstrating a role for EphA2 in promoting melanoma tumorigenicity and suggest EphA2 as a significant molecular target for the therapeutic intervention of malignant melanoma.

The EphA3 receptor is expressed in a subset of rhabdomyosarcoma cell lines and suppresses cell adhesion and migration

Elevated expression of the Eph receptor tyrosine kinase EphA3 is associated with lymphocytic leukaemia, but little is known about its expression or function in solid tumours. Out of a panel of cancer cell lines, we found that EphA3 was expressed only on two rhabdomyosarcoma (RMS) cell lines of the embryonal histological subtype and on one of the alveolar RMS subtype, whereas it was not detected on two other cell lines of the alveolar subtype. Other EphA receptors (1-7) were, either not expressed in any, or expressed in all five RMS cell lines. Stimulation of EphA3-expressing TE671 and RD RMS cells with ephrinA5 resulted in loss of adhesion to fibronectin, decreased migration towards the stromal cell-derived growth factor-I (SDF-I), increased EphA3 phosphorylation, and increased Rho GTPase activity. In contrast, ectopic expression of EphA3 in the EphA3 negative CRL2061 cell line resulted in decreased cell adhesion. Finally, suppression of EphA3 expression by siRNA in RD cells results in increased SDF-I-mediated motility. These data indicate that EphA3 expression may define subsets of RMS tumours, and that EphA3 suppresses motility through regulation of Rho GTPases in RMS cells.

Effects of dasatinib on EphA2 receptor tyrosine kinase activity and downstream signalling in pancreatic cancer

Eph receptors constitute the largest family of receptor tyrosine kinases in the human genome. EphA2 is one prominent member that is overexpressed and functionally altered in many invasive cancers, including pancreatic cancer. Dasatinib, which is a multi-targeted kinase inhibitor mainly developed for Bcr-Abl and Src family kinases, has recently been shown to have significant activity against EphA2. As selective small molecule EphA2 inhibitors are not currently available, we investigated the therapeutic potential to target EphA2 by dasatinib in pancreatic cancer cell lines. Using in vitro kinase assays, we found that EphA2 receptor tyrosine kinase was inhibited directly by dasatinib in a dose-dependent manner. Stimulation with ephrinA1 produced rapid increases of EphA2 phosphorylation that were inhibited by dasatinib, although the effects on activation of downstream signalling differed among the pancreatic cancer cell lines. Dasatinib also inhibited ligand-induced binding of EphA2 to the ubiquitin ligase Cbl, and the internalisation and degradation of EphA2, suggesting that these processes are dependent on kinase activity. Treatment with dasatinib decreased EphA2 phosphorylation in BxPC-3 xenografts, suggesting that dasatinib might have activity in pancreatic cancer due to EphA2 inhibition, besides its effects on Src.

The release of fibroblast growth factor-1 from melanoma cells requires copper ions and is mediated by phosphatidylinositol 3-kinase/Akt intracellular signaling pathway

Melanoma is a highly invasive tumor with elevated mortality rates. Progression and aggressiveness appear related to the achievement of an angiogenic phenotype. Melanoma cells express several angiogenic factors, including fibroblast growth factor (FGF)-1 and FGF-2. The autocrine production and release of FGFs and the subsequent activation of FGF receptors, have a central role in melanoma tumor progression. We demonstrated that FGF-1 is secreted from a human melanoma cell line, A375, under conditions of serum deprivation. The release of FGF-1 is inhibited by the copper chelator ammonium tetrathiomolybdate, suggesting a role of copper in the secretory pathway, and is triggered by activation of phosphatidylinositol 3-kinase (PI3K)/Akt intracellular signaling. Interestingly, overexpression or activation of Akt has been correlated with poor prognosis in melanoma patients. Our data indicate a novel role for Akt in supporting the progression of human melanomas and advocate the need for new treatments targeting PI3K/Akt signaling pathway, to control tumor development and progression.

Pathophysiology of the pleura

The pleural mesothelial cell is an essential cell in maintaining the normal homeostasis of the pleural space and it is also a central component of the pathophysiologic processes affecting the pleural space. In this review, we will review the defense mechanisms of the pleural mesothelium and changes in pleural physiology as a result of inflammatory, infectious, and malignant conditions with a focus on cytokine and chemokine networks. We will also review the processes involved in the pathogenesis of pleural fibrosis.

Receptor EphA2 activation with ephrinA1 suppresses growth of malignant mesothelioma (MM)

The objective of this study was to understand the possible mechanisms of activation of receptor EphA2 by its ligand ephrinA1 in malignant mesothelioma cell (MMC) growth. Activation of receptor EphA2 by its ligand ephrinA1 triggered the phosphorylation of EphA2. Ligand activation of EphA2 also induced phosphorylation of ERK1/2 and significantly decreased MMC proliferation. Ligand activated and ephrinA1 vector (pcDNA/EFNA1) transfected MMC demonstrated decreased clonal growth in 3-D matrigels when compared to resting MMC. These studies suggest that EphA2 activation by its ligand ephrinA1 transmits intracellular signals from cell membrane to nucleus via ERK1/2 signaling cascade and inhibits MM growth.

Comparison of EphA receptor tyrosine kinases and ephrinA ligand expression to EphB-ephrinB in vascularized corneas

PURPOSE

Eph cell surface receptors and their ligands, ephrins, are involved in neuronal patterning and neovascularization. Our purpose is to compare and characterize the expression of ephrinA ligands and EphA receptors to ephrinB ligands and EphB receptors in excised mouse corneal tissue, in corneal epithelial and keratocyte cell lines, and during corneal angiogenesis.

METHODS

Mouse corneal epithelial cells and keratocytes were immortalized using SV40T antigen viral infection of primary cultures. The immortalized epithelial cells and keratocytes were cloned and characterized using antibodies to keratin, vimentin, integrin alpha5beta1, and alpha-smooth muscle actin. Basic fibroblast growth factor pellets were implanted to induce corneal neovascularization. The eyes of wild-type, ephrinB2(tlacZ/+), and EphB4(tlacZ/+) heterozygous mice were harvested and sectioned 7 days after pellet implantation. Confocal immunohistochemistry was performed to compare the expression of the Eph/ephrinA family (EphA1-8, ephrinA1-5) and Eph/ephrinB family (EphB1-4, EphB6 ephrinB1-3).

RESULTS

EphA1, EphA3, ephrinA1, ephrinA2, EphB1, EphB4, ephrinB1, and ephrinB2 were detected in wild-type mouse corneal epithelial cells and keratocytes. EphA2 was immunolocalized only in epithelial cells. Also, EphA3, ephrinA1, EphB1, EphB4, and ephrinB1 were immunolocalized to the corneal epithelium and stroma. In the vascularized corneas, ephrinB1 was immunolocalized mainly to the keratocytes around the vessels, and ephrinB2, EphB1, and EphB4 were colocalized mainly with CD31 to the vascular endothelial cells.

CONCLUSIONS

The characterization of ephrin ligand and Eph receptor expression during cornea angiogensis in this study suggests that the Eph/ephrin family of receptor tyrosine kinases and their ligands may play a role in the regulation of corneal angiogenesis.

The EphB4 receptor-tyrosine kinase promotes the migration of melanoma cells through Rho-mediated actin cytoskeleton reorganization

Several studies have reported the up-regulation of EphB receptor-tyrosine kinases and ephrin-B ligands in a variety of tumors, suggesting a functional relation between EphB/ephrin-B signaling and tumor progression. The ability of the EphB receptors to regulate cell migration and promote angiogenesis likely contributes to tumor progression and metastasis. Here we show that EphB receptors, and especially EphB4, regulate the migration of murine melanoma cells. Highly malignant melanoma cells express the highest levels of EphB4 receptor and migrate faster than less malignant melanoma cells. Furthermore, inhibition of EphB receptor forward signaling by overexpression of a form of EphB4 lacking the cytoplasmic portion or by treatment with competitively acting soluble EphB2-Fc results in slower melanoma cell migration. In contrast, overexpression of active EphB4 significantly enhances cell migration. The effects of EphB4 receptor on cell migration and cell morphology require its kinase activity because the inhibition of EphB4 kinase activity by overexpression of kinase dead EphB4 inhibits cell migration and affects the organization of actin cytoskeleton. Activation of EphB4 receptor with its ligand ephrin-B2-Fc enhances the migratory ability of melanoma cells and increases RhoA activity, whereas inhibiting EphB receptor forward signaling decreases RhoA activity. Moreover, expression of dominant negative RhoA blocks the effects of active EphB4 on cell migration and actin organization. These data suggest that EphB4 forward signaling contributes to the high migratory ability of invasive melanoma cells by influencing RhoA-mediated actin cytoskeleton reorganization.

Analysis of protein tyrosine kinases expression in the melanoma metastases of patients treated with Imatinib Mesylate (STI571, GleevecTM)

BACKGROUND

Protein tyrosine kinase (PTK) inhibition has been identified as a promising strategy in the development of new selective therapies, targeting the signaling pathways in melanoma progression. Gleevec, a novel class of anti-tumor drugs, may have a potential therapeutic benefit in melanoma, which involves abnormal activation of abl, c-kit, and platelet-derived growth factor (PDGF) tyrosine kinases.

METHODS

Tumor biopsies from 13 patients with metastatic melanoma were screened by immunohistochemistry for PTK [c-kit, C-abl, Abl-related gene (ARG), PDGF receptor-alpha (PDGFR-alpha) and PDGFR-beta] expression before and after being treated with Gleevec @ 400 mg bid for 2 weeks. Both, percentage of positive cells and staining intensity were evaluated.

RESULTS

We found a statistically significant (p < 0.01) selective loss of PTK expression in the follow-up biopsy, both in intensity and number of positive cells. PDGFR-alpha and -beta had the highest level of expression reduction. One patient had a durable clinical response, and the follow-up biopsy showed negative expression for four of the PTKs, namely c-abl, ARG, PDGFR-alpha, and beta.

CONCLUSIONS

Our study reports for the first time the in vivo effect of Gleevec in the induction of apparently selective reduction of PTKs expression under anti-tyrosine kinases treatment, suggesting its potential role in melanoma treatment.

EphrinA1 Repulsive Response Is Regulated by an EphA2 Tyrosine Phosphatase

Ephrin kinases and their ephrin ligands transduce repulsion of cells in axon guidance, migration, invasiveness, and tumor growth, exerting a negative signaling on cell proliferation and adhesion. A key role of their kinase activity has been confirmed by mutant kinase inactive receptors that shift the cellular response from repulsion to adhesion. Our present study aimed to investigate the role of low molecular weight protein-tyrosine phosphatase (LMW-PTP) in ephrinA1/EphA2 signaling. LMW-PTP, by means of dephosphorylation of EphA2 kinase, negatively regulates the ephrinA1-mediated repulsive response, cell proliferation, cell adhesion and spreading, and the formation of retraction fibers, thereby confirming the relevance of the net level of tyrosine phosphorylation of Eph receptors. LMW-PTP interferes with ephrin-mediated mitogen-activated protein kinase signaling likely through inhibition of p120RasGAP binding to the activated EphA2 kinase, thereby confirming the key role of mitogen-activated protein kinase inhibition by ephrinA1 repulsive signaling. We conclude that LMW-PTP acts as a terminator of EphA2 signaling causing an efficient negative feedback loop on the biological response mediated by ephrinA1 and pointing on tyrosine phosphorylation as the main event orchestrating the repulsive response.

EPHA2/EFNA1 expression in human gastric cancer

The erythropoietin-producing hepatocellular (EPH)A2 receptor, tyrosine kinase, is overexpressed and phosphorylated in several types of human tumors and has been associated with malignant transformation. A recent report, however, indicated that stimulation of the EPHA2 receptor ligand, ephrinA1 (EFNA1), inhibits the growth of EPHA2-expressing breast cancer. The authors examined the expression of EPHA2 and EFNA1 using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) in four gastric cancer cell lines and 49 primary gastric cancer samples, as well as in normal gastric tissue. EPHA2 was more highly expressed in tumor tissue than in normal tissue in 27 cases (55%). EFNA1 was overexpressed in tumor tissue in 28 cases (57%). No significant correlation was detected between the expression levels and histologic features such as tumor size, age, vessel invasion, or lymph node involvement. However, EPHA2 overexpression was more prominent in macroscopic type 3 and 4 tumors than in type 1 or 2 advanced gastric cancer. The authors observed EPHA2 expression in three of the four gastric cancer cell lines (AGS, KATO3, and MKN74) that were examined. In one cell line, TMK1, EPHA2 expression was barely detectable using northern blotting, RT-PCR, and western blotting. In contrast, EFNA1 was detected in all cell lines. In the gastric cancer cell lines that endogenously expressed EPHA2, stimulation with ephrinA1-Fc led to decreased EPHA2 protein expression and increased EPHA2 phosphorylation. Finally, the growth of EPHA2-expressing cells was inhibited by repetitive stimulation with soluble ephrinA1-Fc. Taken together, these findings suggest that EPHA2 and EFNA1 expression may influence the behavior of human gastric cancer.

Expression profiling reveals novel pathways in the transformation of melanocytes to melanomas

Affymetrix and spotted oligonucleotide microarrays were used to assess global differential gene expression comparing normal human melanocytes with six independent melanoma cell strains from advanced lesions. The data, validated at the protein level for selected genes, confirmed the overexpression in melanoma cells relative to normal melanocytes of several genes in the growth factor/receptor family that confer growth advantage and metastasis. In addition, novel pathways and patterns of associated expression in melanoma cells not reported before emerged, including the following: (a) activation of the NOTCH pathway; (b) increased Twist expression and altered expression of additional transcriptional regulators implicated in embryonic development and epidermal/mesenchymal transition; (c) coordinated activation of cancer/testis antigens; (d) coordinated down-regulation of several immune modulation genes, in particular in the IFN pathways; (e) down-regulation of several genes implicated in membrane trafficking events; and (f) down-regulation of growth suppressors, such as the Prader-Willi gene NECDIN, whose function was confirmed by overexpression of ectopic Flag-necdin. Validation of differential expression using melanoma tissue microarrays showed that reduced ubiquitin COOH-terminal esterase L1 in primary melanoma is associated with worse outcome and that increased expression of the basic helix-loop-helix protein Twist is associated with worse outcome. Some differentially expressed genes reside on chromosomal regions displaying common loss or gain in melanomas or are known to be regulated by CpG promoter methylation. These results provide a comprehensive view of changes in advanced melanoma relative to normal melanocytes and reveal new targets that can be used in assessing prognosis, staging, and therapy of melanoma patients.

Invasiveness of breast carcinoma cells and transcript profile: Eph receptors and ephrin ligands as molecular markers of potential diagnostic and prognostic application

The Eph family of receptors, with 14 members in humans, makes up the largest group of receptor tyrosine kinases. These Eph receptors, along with their ligands, the 8 members of the ephrin family of ligands are involved in diverse developmental functions, including hindbrain development in vertebrates, tissue patterning, and angiogenesis. These Eph receptors and ephrin ligands have also been identified as important regulators in the development and progression of cancer. We have presented here a systematic and comprehensive investigation of the Eph/ephrin expression profiles of MCF-10A, MCF-7, and MDA-MB-231 cells representing normal breast, non-invasive breast tumor, and invasive tumor, respectively, based on their characteristic phenotypes in Matrigel matrix. The data have allowed us to correlate the gene expression profile with the cell phenotype that has potential application in tumor diagnostics. We demonstrate here that upregulation of EphA2, A7, A10, and ephrinA2 and B3 is likely involved in tumorigenesis and/or invasiveness, while downregulation of EphA1, A3, A4, A8, B3, B4, B6, and ephrinA1 and B1 may be particularly important in invasiveness. Based on these results we discuss the role of EphA2 and ephrinA1 combination in malignancy. The data have provided clues as to the importance of these molecules in the progression of breast cancer and specifically identified EphB6, a kinase-deficient receptor, which is downregulated in the most aggressive cell line, as reported for several other cancer types including neuroblastoma and melanoma suggesting its potential as a prognostic indicator in breast cancer as well.

Cell protection, resistance and invasiveness of two malignant mesotheliomas as assessed by 10K-microarray

Malignant pleural mesothelioma (MPM) is an aggressive serosal tumor, strongly associated with former exposure to asbestos fibers and for which there is currently no effective treatment available. In human, MPM is characterized by a high local invasiveness, poor prognosis and therapeutic outcomes. In order to assess molecular changes that specify this phenotype, we performed a global gene expression profiling of human MPM. Using a 10,000-element microarray, we analyzed mRNA relative gene expression levels by comparing a mesothelioma cell line to either a pleural cell line or tumor specimens. To analyze these gene expression data, we used various bioinformatics softwares. Hierarchical clustering methods were used to group genes and samples with similar expression in an unsupervised mode. Genes of known function were further sorted by enzyme, function and pathway clusters using a supervised software (IncyteGenomics). Taken together, these data defined a molecular fingerprint of human MPM with more than 700 up- or down-regulated genes related to several traits of the malignant phenotype, specially associated with MPM invasiveness, protection and resistance to anticancer defenses. This portrait is meaningful in disease classification and management, and relevant in finding new specific markers of MPM. These molecular markers should improve the accuracy of mesothelioma diagnosis, prognosis and therapy.

Correlation of EPHA2 overexpression with high microvessel count in human primary colorectal cancer

Evidence suggests that the erythropoietin-producing hepatocellular (EPH) receptor tyrosine kinases (RTKs) and their ephrin (EFN) ligands are involved in human carcinogenesis. Expression of two of them, EFNA1 ligand and its receptor, EPHA2, has been proposed to contribute to tumor-induced neovascularization. Colorectal cancers were examined for expressions of EPHA2 and its ligand EFNA1 by semi-quantitative RT-PCR, and double-immunostained for EPHA2 and CD34. Microvessels in the tumors were counted. Double-staining was also performed in 25 cases of adenoma with focal cancer for comparison. Trends of overexpression of both EPHA2 and EFNA1 was found in tumor tissue compared to the corresponding normal tissue in the same specimen [22/37 (59.5%) and 25/37 (67.5%), respectively; P = 0.100 for EPHA2 and P = 0.009 for EFNA1]. Overexpression of EPHA2 and EFNA1 was noted more frequently in the early stage than in the late stage [EPHA2, 15/21 (71.4%) vs. 7/16 (43.8%), P = 0.007; EFNA1, 15/21 (71.4%) vs. 10/16 (62.5%), P = 0.007]. Both EPHA2 and EFNA1 were more frequently overexpressed in smaller tumors (less than 5 cm) than in larger tumors [EPHA2, 15/21 (71.4%) vs. 7/16 (43.8%), P = 0.017; EFNA1, 16/21 (76.2%) vs. 8/16 (50%), P = 0.001]. Tumors less than 5 cm in diameter and in stages I and II were significantly more likely to overexpress EPHA2 and EFNA1 (P = 0.001 for EPHA2, P = 0.001 for EFNA1). Microvessel counts (MVCs) after immunostaining for CD34 were significantly correlated (r = 0.343, P = 0.037) with overexpression of EPHA2. EPHA2-expressing focal cancer also surrounded microvessels in adenomas with focal cancers. These findings suggest an involvement of EPHA2 in colon carcinogenesis, mainly in stages I and II, and probably through their effect on microvessel induction.

High-level expression of EphA2 receptor tyrosine kinase in prostatic intraepithelial neoplasia

EphA2 is a transmembrane receptor tyrosine kinase that is overexpressed in many carcinomas. Specific targeting of EphA2 with monoclonal antibodies is sufficient to inhibit the growth, migration and invasiveness of aggressive cancers in animal models. Using immunohistochemical analyses, we measured the expression of EphA2 in prostatic adenocarcinoma, high-grade prostatic intraepithelial neoplasia, and adjacent benign prostate tissue from ninety-three radical prostatectomy specimens. These results were related to multiple clinical and pathologicalcharacteristics. The fraction of cells staining positively with EphA2 in benign prostatic epithelium (mean, 12%) was significantly lower than that in high-grade prostatic intraepithelial neoplasia (mean, 67%, P < 0.001) and prostatic adenocarcinoma (mean, 85%, P < 0.001). Moreover, the intensity of EphA2 immunoreactivity in prostatic adenocarcinoma was significantly higher than in benign prostatic tissue (P < 0.001) or high-grade prostatic intraepithelial neoplasia (P < 0.001). Benign prostatic epithelium showed weak or no immunoreactivity for EphA2 in all cases examined. Whereas EphA2 immunoreactivity related to neoplastic transformation, it did not correlate with other clinical and pathological parameters examined. Our data suggest that EphA2 levels increase as prostatic epithelial cells progress toward a more aggressive phenotype. Progressively higher levels of EphA2 in high-grade prostatic intraepithelial neoplasia and prostatic carcinoma are consistent with recent evidence that EphA2 functions as a powerful oncogene. Moreover, the presence of high levels of EphA2 in these cells suggests opportunities for prostate cancer prevention and treatment.

Immunohistochemical determination of HER-2/neu overexpression in malignant melanoma reveals no prognostic value, while c-Kit (CD117) overexpression exhibits potential therapeutic implications

Background

HER-2/neu and c-kit (CD117) onco-protein are increasingly being recognized as targets for therapy in solid tumors, but data on their role in malignant melanoma is currently limited. We studied the prevalence of overexpression of HER-2/neu and c-Kit in 202 patients with malignant melanoma to evaluate a possible prognostic value of these molecular targets in malignant melanoma.

Methods

Overexpression of HER-2/neu and c-Kit was evaluated using immunohistochemical assays in 202 archival tissue specimens.

Results

Between 1991 and 2001, 202 subjects (109 males; 54% and 93 females; 46%) with malignant melanoma were studied with a mean age of 57 years (age range: 15–101 years). The most common histologic type was amelanotic melanoma (n = 62; 30.7%) followed by superficial spreading melanoma (n = 54; 26.7%). The depth of penetration of melanoma (Breslow thickness, pT Stage) ranged from 0.4 mm (stage pT1) to 8.0 mm (stage pT4A). Mean thickness was 2.6 mm (stage pT3A). The ECOG performance scores ranged from 0 to 3. Only 2 patients (0.9%) revealed HER-2/neu overexpression, whereas 46 (22.8%) revealed c-Kit overexpression. Multivariate analysis performed did not show a significant difference in survival between c-Kit positive and negative groups (p = 0.36). Interestingly, not only was c-Kit more likely to be overexpressed in the superficial spreading type, a preliminary association between the presence or absence of c-Kit overexpression and the existence of another second primary tumor was also observed.

Conclusions

The results of our large study indicate that the HER-2/neu onco-protein neither has a role in melanogenesis nor is a potential target for clinical trials with monoclonal antibody therapy. This indicates there is no role for its testing in patients with malignant melanoma. Although c-Kit, expressed preferentially in the superficial spreading type, may not have prognostic value, it does have significant therapeutic implications as a molecular target warranting further investigation.

Absence of HER2 overexpression in metastatic malignant melanoma

BACKGROUND AND OBJECTIVES

Currently available systemic therapies for malignant melanoma produce low response rates in patients, and more effective treatment modalities are clearly needed. Trastuzumab (Herceptin), the antibody to the HER2 oncoprotein, has had a significant impact on therapy for patients with HER2-overexpressing metastatic breast cancer. This study examined the incidences of HER2 protein overexpression and HER2 gene amplification in metastatic malignant melanoma, which remain unclear in the literature.

METHODS

The study evaluated patients with stage III and stage IV malignant melanoma who were treated between 1983 and 1999. Tissue blocks were retrieved and reviewed to confirm the diagnosis. From the 101 cases identified, 49 (31 stage III and 18 stage IV) had sufficient residual tumor sample to enable an assay to be performed. The blocks were tested for HER2 overexpression using the DAKO HercepTest immunohistochemical (IHC) assay. Any sample that tested 1+ or greater for HER2 expression on IHC and a randomly selected subset of HER2-negative samples were tested for the presence of HER2 gene amplification using the Vysis PathVysion fluorescence in situ hybridization (FISH) assay.

RESULTS

The median age of the 49 selected patients was 52.2 years, and the male-to-female ratio was 1.23:1 (27 men to 22 women). All of the 49 cases of malignant melanoma were negative for HER2 overexpression by IHC. However, two samples (3%) were found to have a weak level of HER2 expression (1+ level of staining). Subsequent FISH results on the samples that were 1+ on IHC were negative for HER2 gene amplification. FISH results on 21 other randomly selected IHC-negative samples were also negative for HER2 amplification. Flow cytometry failed to show HER2 overexpression in two melanoma cell lines, and treatment of these cells with trastuzumab did not affect their proliferation rate.

CONCLUSIONS

We found a low incidence of HER2 expression and no evidence of HER2 protein overexpression or HER2 gene amplification in metastatic malignant melanoma tissues. Therefore, routine testing for HER2 overexpression or HER2 amplification would not be of benefit in this patient population. These results also imply that anti-HER2 therapy with trastuzumab is highly unlikely to provide benefit for patients with metastatic melanoma.

Expression of neurotrophin receptor Trk-C in nevi and melanomas

BACKGROUND

Neurotrophins (NTs) are growth factors for neurons and other neural crest-derived cells. Their functions are mediated by 75-kDa low-affinity glycoprotein receptor (p75) NT receptor and a family of tyrosine kinase receptors (Trks) that includes Trk-A, -B, and -C. Signal transduction through the Trk receptors has been shown to regulate growth and apoptosis of tumors of neuronal origin. In addition, Trk oncogenes have been shown to be rearranged in some non-neuronal neoplasms. Recently, immunoexpression of NT-3 has been shown to be significantly higher in melanomas than in banal nevi on cryostat tissue.

METHODS

Since the biologic function of NT-3 is mediated primarily through Trk-C, we investigated Trk-C immunoexpression on paraffin sections of 10 compound nevi and 63 melanomas.

RESULTS

The expression of Trk-C was relatively low in compound nevi (30%). Trk-C expression was overall 62% in melanomas of various stages. Our data show that the expression of Trk-C increased as melanoma progressed from in situ (58%) to papillary dermal invasion (91%), and then declined in deeper (57%) and metastatic melanomas (31%).

CONCLUSION

These findings suggest a possible role of Trk-C in the progression of early stages of melanoma.

Overexpression and functional alterations of the EphA2 tyrosine kinase in cancer

Cancer is a disease of aberrant signal transduction. The expression and function of intracellular signaling pathways are frequently subverted as cells progress towards a metastatic phenotype. In particular, tyrosine kinases initiate powerful signals that govern many different aspects of cell behavior. In Recent studies have demonstrated that the EphA2 receptor tyrosine kinase is frequently overexpressed and functionally altered in aggressive tumor cells, and that these changes promote metastatic character. Herein, we provide an overview of our current understanding of EphA2, with emphasis upon the differential regulation of EphA2 expression and function. We also show that differential EphA2 expression and function may provide a unique opportunity for selective therapeutic targeting of EphA2 in metastatic disease.

An ephrin mimetic peptide that selectively targets the EphA2 receptor

Eph receptor tyrosine kinases represent promising disease targets because they are differentially expressed in pathologic versus normal tissues. The EphA2 receptor is up-regulated in transformed cells and tumor vasculature where it likely contributes to cancer pathogenesis. To exploit EphA2 as a therapeutic target, we used phage display to identify two related peptides that bind selectively to EphA2 with high affinity (submicromolar K(D) values). The peptides target the ligand-binding domain of EphA2 and compete with ephrin ligands for binding. Remarkably, one of the peptides has ephrin-like activity in that it stimulates EphA2 tyrosine phosphorylation and signaling. Furthermore, this peptide can deliver phage particles to endothelial and tumor cells expressing EphA2. In contrast, peptides corresponding to receptor-interacting portions of ephrin ligands bind weakly and promiscuously to many Eph receptors. Bioactive ephrin mimetic peptides could be used to selectively deliver agents to Eph receptor-expressing tissues and modify Eph signaling in therapies for cancer, pathological angiogenesis, and nerve regeneration.

Diverse roles for the Eph family of receptor tyrosine kinases in carcinogenesis

The Eph family of receptor tyrosine kinases and their cell-presented ligands, the ephrins, are frequently overexpressed in a wide variety of cancers, including breast, small-cell lung and gastrointestinal cancers, melanomas, and neuroblastomas. In particular, one Eph family member, EphA2, is overexpressed in many cancers, including 40% of breast cancers. EphA2 can also transform breast epithelial cells in vitro to display properties commonly associated with the development of metastasis. Remarkably, the oncogenic properties of EphA2 contravene traditional dogma with regard to the oncogenic properties of a growth factor and its receptor tyrosine kinase: while stimulation of EphA2 by its ligand (ephrin-A1) results in EphA2 autophosphorylation, the stimulation reverses the oncogenic transformation. As will be discussed in this review, the apparent dependence of oncogenicity on the dephosphorylated state of EphA2 most probably reflects the unique nature of Eph signaling. In particular, oncogenecity may depend on the capacity of unactivated EphA2 to interact with a variety of signaling molecules. As well as acting in oncogenic transformation, a growing body of evidence supports the importance of the concerted actions of ephrins and Eph molecules in tumor angiogenesis. Genetic studies, using targeted mutagenesis in mice, reveal that ephrin-B1, ephrin-B2, and EphB4 are essential for the normal morphogenesis of the embryonic vasculature into a sophisticated network of arteries, veins, and capillaries. Initial studies indicate that these molecules are also angiogenic in tumors, and as such represent important new targets for the development of chemotherapeutic treatments.

Activation of the EphA2 tyrosine kinase stimulates the MAP/ERK kinase signaling cascade

Intracellular signaling by receptor tyrosine kinases regulates many different aspects of cell behavior. Recent studies in our laboratory and others have demonstrated that the EphA2 receptor tyrosine kinase critically regulates tumor cell growth, migration and invasiveness. Although the cellular consequences of EphA2 signaling have been the focus of recent attention, the biochemical changes that are triggered by ligand-mediated activation of EphA2 remain largely unknown. Herein, we demonstrate that ligand stimulation of EphA2 promotes the nucleus translocation and phosphorylation of ERK kinases, followed by an increase in nuclear induction of the Elk-1 transcription factor. Ligand-mediated activation allows EphA2 to form a molecular complex with the SHC and GRB2 adaptor proteins. Specifically, we demonstrate that tyrosine phosphorylated EphA2 interacts with the PTB and SH2 domains of SHC. We also show that the interaction of EphA2 with GRB2 is indirect and mediated by SHC and that this complex is necessary for EphA2-mediated activation of ERK kinases. These studies provide a novel mechanism to demonstrate how EphA2 can convey information from the cell exterior to the nucleus.