Serum levels of the angiogenic factor pleiotrophin in relation to disease stage in lung cancer patients

miR-200-mediated inactivation of cancer-associated fibroblasts via targeting of NRP2-VEGFR signaling attenuates lung cancer invasion and metastasis

Cancer-associated fibroblasts (CAFs) play a substantial role in promoting cancer cell motility, drug resistance, angiogenesis, and metastasis; therefore, extensive research has been conducted to determine their mode of activation. We aimed to identify whether miRNA-200 (miR-200), a widely recognized suppressor of epithelial-mesenchymal transition, prevents CAFs from promoting cancer progression. Overexpression of miR-200 prevented CAFs from promoting lung cancer cell migration, invasion, tumorigenicity, and metastasis. Additionally, miR-200 suppressed the ability of CAFs to recruit and polarize macrophages toward the M2 phenotype, as well as the migration and tube formation of vascular endothelial cells. NRP2, a co-receptor of vascular endothelial growth factor receptor (VEGFR), was confirmed to be a target of miR-200, which mediates the functional activity of miR-200 in CAFs. NRP2-VEGFR signaling facilitates the secretion of VEGF-D and pleiotrophin from CAFs, leading to the activation of cancer cell migration and invasion. These findings suggest that miR-200 remodels CAFs to impede cancer progression and metastasis and that miR-200 and NRP2 are potential therapeutic targets in the treatment of lung cancer.

Understanding of molecular basis of histological graded horn cancer by transcriptome profiling

Horn cancer is most devastating and prominent cancer in Indian zebu cattle that affects socio-economic condition of small-scale farmers who depends on their cattle for farm work. Development in the field for genomics through next generation sequencing and bioinformatics advancement have helped to identify genes which have a role in horn cancer development. Histopathological examination of cancerous tissues of horn revealed myxomatous changes, well, moderate and poorly differentiated squamous cell carcinoma. Differential gene expression analysis showed 40, 11, 66 and 29 upregulated genes and 10, 14, 08 and 07 down-regulated genes in myxomatous, well, moderate and poorly differentiated squamous cell carcinoma as compared to normal. Significant differentially expressed genes are related to cell development, cell proliferation, cell-cell communication, cell signaling and angiogenesis which are linked to Akt pathway, mTOR pathway and Wnt pathway. Activity of these genes and related pathways have already been established about their role in development of cancer. Among the candidate genes; keratin family, keratin family related gene, chemokine signaling and cytokines signaling associated genes could be a prominent target for the development of stage specific prognosis marker after further detailed study at large sample population level. CSTA, PTN, SPP1 genes have upregulation in all stages of cancer and they have enrolled as biomarkers for horn cancer.

Pleiotrophin serum level is increased in Relapsing-Remitting Multiple Sclerosis and correlates with sex, BMI and treatment

BACKGROUND

Multiple Sclerosis (MS) is an immune-mediated demyelinating disease mainly affecting the Central Nervous System (CNS). 80% of MS patients present the Relapsing-Remitting form (RRMS). Pleiotrophin (PTN), a cytokine previously associated with other autoimmune and neurological diseases, could play a role in the pathophysiology of RRMS due to its neuro and immunomodulatory effect. However, PTN has never been explored in RRMS patients.

AIM OF THE STUDY

To determine PTN serum levels in patients with RRMS, treated with Glatiramer acetate (GA) or Interferon-beta (IFN-β), as well as in non-treated patients and healthy controls as a first attempt to explore PTN in RRMS.

METHODS

PTN serum levels were quantified by ELISA in 57 patients and 18 controls.

RESULTS

We demonstrated that PTN serum levels are significantly higher in RRMS patients. In IFN-β treated patients alone, PTN correlated positively with time of disease evolution and time of IFN-β use and correlated negatively with the MS severity score (MSSS). When comparing groups according to weight status, we observed that PTN is statistically increased in overweight female patients and that weight does not affect male patients. The Area Under the Curve (AUC) of the Receiver Operating Characteristic (ROC) curve analysis was higher for males compared to females.

CONCLUSION

PTN serum level is higher in RRMS patients and that is associated with sex, BMI and IFN-β treatment. Therefore, we propose that PTN could be playing a role in MS. Further studies must be performed to identify the exact role of PTN in this pathology.

Assessing the Angiogenic Efficacy of Pleiotrophin Released from Injectable Heparin-Alginate Gels

With this work, we design alginate-based hydrogels for therapeutically directing revascularization and repair processes in vivo. We immobilize pleiotrophin (PTN) in injectable hydrogel formulations as the target factor to stimulate proangiogenic responses in endothelial cells. The optimized heparin-alginate/chitosan hydrogels, produced by internal crosslinking with calcium carbonate, show good biocompatibility and injectability and allow controlling the release of immobilized proteins in the subcutaneous tissue over a period of 7 days. In vitro assays, performed with translational human induced pluripotent stem cell-derived endothelial cells, and the in vivo Matrigel plug assay are conducted to demonstrate the angiogenic effects of PTN on endothelial cells. Our results indicate that PTN stimulates endothelial cell morphogenesis in vitro and the migration of endothelial cells and macrophages as soon as 4 days after injections of the developed hydrogels, promoting the formation of structures similar to the healthy granulation tissue, which is an indicator of healing in ischemic wounds. These studies provide the rationale for further investigating this novel therapeutic for pursuing increased vascular density for efficient regeneration of ischemic tissues, by leveraging the host endothelial cell population to initiate angiogenic and reparative processes in vivo. Impact statement Localized, sustained, and controlled delivery of angiogenic factors is crucial for enabling the formation of novel vascular networks in ischemic tissues. This study describes the development of an injectable heparin-alginate/collagen hydrogel for controlling the in vivo release and bioactivity of pleiotrophin (PTN), a heparin-binding factor with significant angiogenic activity. We demonstrate that PTN promotes angiogenesis in an in vitro model of hypoxia and in preclinical subcutaneous models. These results advance our understanding of PTN function in guiding therapeutic angiogenesis and are critical to inform the development of novel translational strategies for ischemic tissue repair and regeneration.

Pleiotrophin selectively binds to vascular endothelial growth factor receptor 2 and inhibits or stimulates cell migration depending on ανβ3 integrin expression

Pleiotrophin (PTN) has a moderate stimulatory effect on endothelial cell migration through α_νβ₃ integrin, while it decreases the stimulatory effect of vascular endothelial growth factor A (VEGFA) and inhibits cell migration in the absence of α_νβ₃ through unknown mechanism(s). In the present work, by using a multitude of experimental approaches, we show that PTN binds to VEGF receptor type 2 (VEGFR2) with a K_D of 11.6 nM. Molecular dynamics approach suggests that PTN binds to the same VEGFR2 region with VEGFA through its N-terminal domain. PTN inhibits phosphorylation of VEGFR2 at Tyr1175 and still stimulates endothelial cell migration in the presence of a selective VEGFR2 tyrosine kinase inhibitor. VEGFR2 downregulation by siRNA or an anti-VEGFR2 antibody that binds to the ligand-binding VEGFR2 domain also induce endothelial cell migration, which is abolished by a function-blocking antibody against α_νβ₃ or the peptide PTN_112-136 that binds α_νβ₃ and inhibits PTN binding. In cells that do not express α_νβ₃, PTN decreases both VEGFR2 Tyr1175 phosphorylation and cell migration in a VEGFR2-dependent manner. Collectively, our data identify VEGFR2 as a novel PTN receptor involved in the regulation of cell migration by PTN and contribute to the elucidation of the mechanism of activation of endothelial cell migration through the interplay between VEGFR2 and α_νβ₃.

Evaluation of Serum Biomarkers (FGF-2, HGF, MIF and PTN) in Patients With Testicular Germ Cell Cancer

BACKGROUND/AIM

FGF-2, HGF, MIF and PTN have been suggested as biomarkers for testicular germ cell cancer patients in earlier studies. Our study was designed to validate these potential novel tumor markers.

MATERIALS AND METHODS

Serum FGF-2, HGF, MIF and PTN levels were analysed using an ELISA technique in a screening cohort of 20 testicular germ cell cancer patients and 10 healthy men. MIF levels were measured in a validation cohort of 84 patients with testicular cancer, 24 with non-malignant testicular tumors and 64 healthy men.

RESULTS

Serum FGF-2, HGF and PTN levels did not differ in cancer patients and healthy males within the screening cohort, whereas MIF was significantly increased among cancer patients. Within the validation cohort, a modest but insignificant increase of serum MIF was observed in TGCT patients compared to healthy men. MIF levels were not correlated with adverse clinical-pathological parameters.

CONCLUSION

FGF-2, HGF, MIF and PTN are not suitable as non-invasive biomarkers for testicular germ cell cancer patients.

Pleiotrophin: Activity and mechanism

Pleiotrophin (PTN) is a potent mitogenic cytokine with a high affinity for the polysaccharide glycosaminoglycan (GAG). Although it is most strongly associated with neural development during embryogenesis and the neonatal period, its expression has also been linked to a plethora of other physiological events including cancer metastasis, angiogenesis, bone development, and inflammation. A considerable amount of research has been carried out to understand the mechanisms by which PTN regulates these events. In particular, PTN has now been shown to bind a diverse collection of receptors including many GAG-containing proteoglycans. These interactions lead to the activation of many intracellular kinases and, ultimately, activation and transformation of cells. Structural studies of PTN in complex with both GAG and domains from its non-proteoglycan receptors reveal a binding mechanism that relies on electrostatic interactions and points to PTN-induced receptor oligomerization as one of the possible ways PTN uses to control cellular functions.

Tumor-associated macrophages increase the proportion of cancer stem cells in lymphoma by secreting pleiotrophin

Tumor-associated macrophages (TAMs) are closely related to the occurrence and development of lymphoma, but their mechanism is still unclear. Here we collected peripheral blood and lymphoma tissue from patients with diffuse large B lymphoma. Results showed that the proportion of TAMs in high-risk group was significantly higher than that in low-risk group. Moreover, the expressions of pleiotrophin (PTN), PTPRZ1 (PTN receptor) and β-catenin in lymphoma tissues of high-risk group were also significantly higher than those in low-risk group. Correlation analysis showed that the proportion of TAMs in lymphocyte was positively correlated with the expression of PTN and PTPRZ1 in lymphoma tissue. In vitro experimental results showed that TAM promoted the invasion and proliferation of lymphoma cells by secreting PTN. We also found that TAMs increased the proportion of cancer stem cells in lymphoma. Animal experiments showed that TAMs promoted lymphoma growth. Both Ki-67 proliferation index and CD44+cancer stem cells increased significantly in TAM group. Blocking PTN or β-catenin partly inhibited these effects of TAMs. In conclusion, TAMs increased the proportion of cancer stem cells through PTN/β-catenin pathway in lymphoma.

Serum pleiotrophin as a diagnostic and prognostic marker for small cell lung cancer

Pleiotrophin (PTN) is involved in tumour progression, angiogenesis and metastasis. The purpose of this study was to investigate the expression level of PTN in the serum of patients with small cell lung cancer (SCLC) and to explore the clinical significance of PTN. Serum samples from 128 patients with SCLC, 120 healthy volunteers (HV) and 60 patients with benign lung disease (BLD) were collected. The levels of serum PTN were determined with ELISA and its correlation with the clinical data was examined. The serum PTN levels in SCLC patients were significantly higher than that in BLD patients (P < 0.05) or HV (P < 0.05). With a cutoff value of 258.18 ng/mL, the sensitivity and specificity of PTN to SCLC patients and BLD patients, SCLC patients and HV were 79.2% and 91.7%, 86.7% and 95.8% respectively. An area under the curve for all stages of SCLC resulting from PTN, which was significantly better than the other tumour markers tested including progastrin‐releasing peptide and neuron‐specific enolase. High serum PTN levels appear to correlate with poor survival in patients with SCLC. These results suggest that PTN levels in the serum could be a new effective biomarker for the diagnosis and prognosis of SCLC.

A meta-analysis on the role of pleiotrophin (PTN) as a prognostic factor in cancer

Background

Some researchers reported that pleiotrophin (PTN) is associated with the development and metastasis of various tumors and it is a poor prognostic factor for the tumor patients. However, the results of other researches are inconsistent with them. It is obliged to do a meta-analysis to reach a definite conclusion.

Methods

The published studies relevant to PTN were searched in the databases including PubMed, Embase and Web of Science until March 20, 2018. A meta-analysis was conducted to evaluate the role of PTN in clinicopathological characteristics and overall survival (OS) of cancer patients.

Results

Our meta-analysis indicated that the high expression of PTN was remarkably associated with advanced TNM stage (OR = 2.79, 95%CI: 1.92–4.06, P<0.00001) and poor OS (HR = 1.77, 95%CI: 1.41–2.22, P<0.00001) in tumor patients. The expression of PTN was not associated with tumor size (OR = 1.12, 95% CI: 0.55–2.26, P = 0.76), lymph node metastasis (LNM) (OR = 1.95, 95%CI: 0.62–6.12, P = 0.25), distant metastasis (DM) (OR = 2.78, 95%CI: 0.72–10.74, P = 0.14) and histological grade (OR = 1.95, 95%CI: 0.98–3.87, P = 0.06).

Conclusion

The high expression of PTN is significantly relevant to the advanced TNM stage and poor OS in tumor patients. PTN can serve as a promising biomarker to predict unfavorable survival outcomes, and it may be a potential target for tumor treatment.

A 16-gene expression signature to distinguish stage I from stage II lung squamous carcinoma

The present study aimed to perform screening of a gene signature for the discrimination and prognostic prediction of stage I and II lung squamous carcinoma. A microarray meta‑analysis was performed to identify differentially expressed genes (DEGs) between stage I and II lung squamous carcinoma samples in seven microarray datasets collected from the Gene Expression Omnibus database via the MetaQC and MetaDE package in R. The important DEGs were selected according to the betweenness centrality value of the protein‑protein interaction (PPI) network. Support vector machine (SVM) analysis was performed to screen the feature genes for discrimination and prognosis. One independent dataset downloaded from The Cancer Genome Atlas was used to validate the reliability. Pathway enrichment analysis was also performed for the feature genes. A total of 924 DEGs were identified to construct a PPI network consisting of 392 nodes and 686 edges. The top 100 of the 392 nodes were selected as crucial genes to construct an SVM classifier, and a 16‑gene signature (caveolin 1, eukaryotic translation elongation factor 1γ, casein kinase 2α1, tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation η, tyrosine 3‑monooxygenase/tryptophan 5‑monooxygenase activation θ, pleiotrophin, insulin receptor, insulin receptor substrate 1, 3‑phosphoinositide‑dependent protein kinase‑1, specificity protein 1, COP9 signalosome subunit 6, N‑myc downstream regulated gene 1, retinoid X receptor α, heat shock protein 90α A1, karyopherin subunit β1 and erythrocyte membrane protein band 4.1) with high discrimination accuracy was identified. This 16‑gene signature had significant prognostic value, and patients with stage II lung squamous carcinoma exhibited shorter survival rates, compared with those with stage I disease. Seven DEGs of the 16-gene signature were significantly involved in the phosphoinositide 3‑kinase‑Akt signaling pathway. The 16‑gene signature identified in the present study may be useful for stratifying the patients with stage I or II lung squamous carcinoma and predicting prognosis.

Pleiotrophin as a potential biomarker in breast cancer patients

BACKGROUND

Pleiotrophin (PTN), a multifunctional growth factor, is up-regulated in many tumors. PTN is reported to play an important role in the regulation of several cellular processes. The objective of this study is to evaluate the clinical significance of PTN as a tumor marker in breast cancer (BC).

METHODS

Serum PTN levels were detected in 105 BC patients and 40 healthy volunteers using ELISA. In addition, PTN expression was examined in 80 BC tissues in a nested case-control study by immunohistochemistry.

RESULTS

Serum PTN levels were elevated in BC patients compared to healthy controls. Area under receiver operating characteristic (ROC) curve was 0.878 (95% CI: 0.824-0.932). The sensitivity of serum PTN was superior to CEA and CA15-3. High serum PTN levels were associated with TNM stage, histology grade, and distant metastasis. Moreover, serum PTN levels decreased significantly after surgical treatment. In BC tissues, PTN expression was significantly higher in BC tissues relative to paired paracancerous tissues. Tissue PTN expression proved to be a prognostic factor for breast cancer according to multivariable logistic regression analysis.

CONCLUSION

PTN could be considered as a potential biomarker for the presence of breast cancer.

Expression of receptor protein tyrosine phosphatase ζ is a risk factor for triple negative breast cancer relapse

Patients with triple negative breast cancer (TNBC) have a higher rate of distant recurrence and a poorer prognosis than those with other breast cancer subtypes. Therefore, it is important to study the mechanism of TNBC relapse. A retrospective immunohistochemical analysis of the expression of receptor protein tyrosine phosphatase ζ (PTPRZ1) and pleiotrophin (PTN) was performed for 325 cases of breast cancer. These samples included 66 cases of luminal A breast cancer, 67 cases of luminal B breast cancer, 78 cases of Her-2-enriched breast cancer, 78 cases of TNBC and 36 cases of relapsed TNBC (RTNBC). In addition, 30 control specimens and 30 cases of metastasized lymph nodes were examined. PTPRZ1 and PTN were highly expressed in the RTNBC group. Compared with the RTNBC group, significant differences in the expression of PTPRZ1 were observed between the TNBC, BC and control groups. A significant difference was observed in the expression of PTN in the BC group (P<0.05) compared to RTNBC, and there were no significant differences in the expression of PTPRZ1 and PTN among the molecular subtypes. No significant correlation was observed between the expression of PTPRZ1, PTN, ER, PR, Her-2 and ALN and the tumor size or menopause status. No significant correlation was identified between the expression of PTPRZ1 and PTN and the expression of CD24 and CD44. In summary, high expression of PTPRZ1 may be an independent risk indicator for TNBC recurrence and metastasis.

Serum pleiotrophin could be an early indicator for diagnosis and prognosis of non-small cell lung cancer

AIMS

Pleiotrophin (PTN), an angiogenic factor, is associated with various types of cancer, including lung cancer. Our aim was to investigate the possibility of using serum PTN as an early indicator regarding disease diagnosis, classification and prognosis, for patients with non-small cell lung cancer (NSCLC).

METHODS

Significant differences among PTN levels in patients with small cell lung cancer (SCLC, n=40), NSCLC (n=136), and control subjects with benign pulmonary lesions (n=21), as well as patients with different pathological subtypes of NSCLC were observed.

RESULTS

A serum level of PTN of 300.1 ng/ml, was determined as the cutoff value differentiating lung cancer patients and controls, with a sensitivity and specificity of 78.4% and 66.7%, respectively. Negative correlations between serum PTN level and pathological differentiation level, stage, and survival time were observed in our cohort of patients with NSCLC. In addition, specific elevation of PTN levels in pulmonary tissue in and around NSCLC lesions in comparison to normal pulmonary tissue obtained from the same subjects was also observed (n=2).

CONCLUSION

This study suggests that the serum PTN level of patients with NSCLC could be an early indicator for diagnosis and prognosis. This conclusion should be further assessed in randomized clinical trials.

PTPRZ1 regulates calmodulin phosphorylation and tumor progression in small-cell lung carcinoma

BACKGROUND

Small-cell lung carcinoma (SCLC) is a neuroendocrine tumor subtype and comprises approximately 15% of lung cancers. Because SCLC is still a disease with a poor prognosis and limited treatment options, there is an urgent need to develop targeted molecular agents for this disease.

METHODS

We screened 20 cell lines from a variety of pathological phenotypes established from different organs by RT-PCR. Paraffin-embedded tissue from 252 primary tumors was examined for PTPRZ1 expression using immunohistochemistry. shRNA mediated PTPRZ1 down-regulation was used to study impact on tyrosine phosphorylation and in vivo tumor progression in SCLC cell lines.

RESULTS

Here we show that PTPRZ1, a member of the protein tyrosine- phosphatase receptor (PTPR) family, is highly expressed in SCLC cell lines and specifically exists in human neuroendocrine tumor (NET) tissues. We also demonstrate that binding of the ligand of PTPRZ1, pleiotrophin (PTN), activates the PTN/PTPRZ1 signaling pathway to induce tyrosine phosphorylation of calmodulin (CaM) in SCLC cells, suggesting that PTPRZ1 is a regulator of tyrosine phosphorylation in SCLC cells. Furthermore, we found that PTPRZ1 actually has an important oncogenic role in tumor progression in the murine xenograft model.

CONCLUSION

PTPRZ1 was highly expressed in human NET tissues and PTPRZ1 is an oncogenic tyrosine phosphatase in SCLCs. These results imply that a new signaling pathway involving PTPRZ1 could be a feasible target for treatment of NETs.

Chicken pleiotrophin: regulation of tissue specific expression by estrogen in the oviduct and distinct expression pattern in the ovarian carcinomas

Pleiotrophin (PTN) is a developmentally-regulated growth factor which is widely distributed in various tissues and also detected in many kinds of carcinomas. However, little is known about the PTN gene in chickens. In the present study, we found chicken PTN to be highly conserved with respect to mammalian PTN genes (91–92.6%) and its mRNA was most abundant in brain, heart and oviduct. This study focused on the PTN gene in the oviduct where it was detected in the glandular (GE) and luminal (LE) epithelial cells. Treatment of young chicks with diethylstilbesterol induced PTN mRNA and protein in GE and LE, but not in other cell types of the oviduct. Further, several microRNAs, specifically miR-499 and miR-1709 were discovered to influence PTN expression via its 3′-UTR which suggests that post-transcriptional regulation influences PTN expression in chickens. We also compared expression patterns and CpG methylation status of the PTN gene in normal and cancerous ovaries from chickens. Our results indicated that PTN is most abundant in the GE of adenocarcinoma of cancerous, but not normal ovaries of hens. Bisulfite sequencing revealed that 30- and 40% of −1311 and −1339 CpG sites are demethylated in ovarian cancer cells, respectively. Collectively, these results indicate that chicken PTN is a novel estrogen-induced gene expressed mainly in the oviductal epithelia implicating PTN regulation of oviduct development and egg formation, and also suggest that PTN is a biomarker for epithelial ovarian carcinoma that could be used for diagnosis and monitoring effects of therapies for the disease.

PAX3-FKHR regulates the expression of pleiotrophin to mediate motility in alveolar rhabdomyosarcoma cells

More than 80% of the aggressive alveolar rhabdomyosarcoma (ARMSs) harbor a PAX3-FKHR fusion transcription factor, which regulates cell motility and promotes metastasis. Our hypothesis is that PAX3-FKHR regulates cell motility by regulating the expression of its transcriptional targets that are also its downstream effectors, which if identified, may lead to novel therapeutic approaches for treating ARMS. Here we report that PAX3-FKHR regulates the expression of pleiotrophin (PTN) by binding specifically to a paired-box domain binding-site in the PTN promoter, indicating that PTN is a transcriptional target of PAX3-FKHR. Significantly, we show that PTN regulates ARMS cell motility. Taken together, we have identified PTN as a novel transcriptional target of PAX3-FKHR that promotes ARMS cell motility. PTN may be a novel therapeutic target for the treatment of ARMS.

Menin represses tumorigenesis via repressing cell proliferation

Multiple endocrine neoplasia type 1 (MEN1) results from mutations in the tumor suppressor gene, MEN1, which encodes nuclear protein menin. Menin is important for suppressing tumorigenesis in various endocrine and certain non-endocrine tissues. Although menin suppresses MEN1 through a variety of mechanisms including regulating apoptosis and DNA repair, the role of menin in regulating cell proliferation is one of the best-studied functions. Here, we focus on reviewing various mechanisms underlying menin-mediated inhibition of cell proliferation. Menin inhibits cell proliferation to repress MEN1 through multiple mechanisms. 1) Menin interacts with various histonemodifying enzymes, such as MLL, EZH2 and HDACs, to affect gene transcription, leading to repression of cell proliferation. 2) Menin also interacts with various transcription factors, such as JunD, NF-κB, PPARγ and VDR, to induce or suppress gene transcription. As these various transcription factors are known to regulate cell proliferation, their interaction with menin may be relevant to menin's role in inhibiting cell proliferation. 3) Menin inhibits cell proliferation via TGF-β signaling and Wnt/β-catenin signaling pathways. 4) Menin represses certain pro-proliferative factors involved in endocrine tumors such as IGFBP-2, IGF2 and PTHrP to repress cell proliferation. 5) Menin affects cell cycle progression to inhibit cell proliferation. This review is helpful in our understanding of the comprehensive mechanisms whereby menin represses MEN1 through inhibiting cell proliferation.

Unlocking biomarker discovery: large scale application of aptamer proteomic technology for early detection of lung cancer

Background

Lung cancer is the leading cause of cancer deaths worldwide. New diagnostics are needed to detect early stage lung cancer because it may be cured with surgery. However, most cases are diagnosed too late for curative surgery. Here we present a comprehensive clinical biomarker study of lung cancer and the first large-scale clinical application of a new aptamer-based proteomic technology to discover blood protein biomarkers in disease.

Methodology/Principal Findings

We conducted a multi-center case-control study in archived serum samples from 1,326 subjects from four independent studies of non-small cell lung cancer (NSCLC) in long-term tobacco-exposed populations. Sera were collected and processed under uniform protocols. Case sera were collected from 291 patients within 8 weeks of the first biopsy-proven lung cancer and prior to tumor removal by surgery. Control sera were collected from 1,035 asymptomatic study participants with ≥10 pack-years of cigarette smoking. We measured 813 proteins in each sample with a new aptamer-based proteomic technology, identified 44 candidate biomarkers, and developed a 12-protein panel (cadherin-1, CD30 ligand, endostatin, HSP90α, LRIG3, MIP-4, pleiotrophin, PRKCI, RGM-C, SCF-sR, sL-selectin, and YES) that discriminates NSCLC from controls with 91% sensitivity and 84% specificity in cross-validated training and 89% sensitivity and 83% specificity in a separate verification set, with similar performance for early and late stage NSCLC.

Conclusions/Significance

This study is a significant advance in clinical proteomics in an area of high unmet clinical need. Our analysis exceeds the breadth and dynamic range of proteome interrogated of previously published clinical studies of broad serum proteome profiling platforms including mass spectrometry, antibody arrays, and autoantibody arrays. The sensitivity and specificity of our 12-biomarker panel improves upon published protein and gene expression panels. Separate verification of classifier performance provides evidence against over-fitting and is encouraging for the next development phase, independent validation. This careful study provides a solid foundation to develop tests sorely needed to identify early stage lung cancer.

Histone lysine methylation and demethylation pathways in cancer

The genetic changes leading to the development of human cancer are accompanied by alterations in the structure and modification status of chromatin, which represent powerful regulatory mechanisms for gene expression and genome stability. These epigenetic alterations have sparked interest into deciphering the regulatory pathways and function of post-translational modifications of histones during the initiation and progression of cancer. In this review we describe and summarize the current knowledge of several histone lysine methyltransferase and demethylase pathways relevant to cancer. Mechanistic insight into histone modifications will pave the way for the development and therapeutic application of "epidrugs" in cancer.

Lung cancer cell migration is regulated via repressing growth factor PTN/RPTP β/ζ signaling by menin

Menin encoded by the multiple endocrine neoplasia type 1 (MEN1) gene is associated with chromatin and the nuclear matrix and exerts multiple biological functions including regulation of cell proliferation and adhesion. Men1 mutations increase the likelihood of lung cancer development in mice. Menin expression is reduced in certain human non-small cell lung cancer cells, and reduction of menin is closely correlated with increased lung cancer metastasis to lymph nodes. However, it is poorly understood whether menin affects migration of lung cancer cells. In this study, we show that menin-regulated A549 lung cancer cell migration, which was mediated by growth factor pleiotrophin (PTN) and its cell surface receptor, protein tyrosine phosphatase beta/zeta (RPTP β/ζ). Ectopic menin expression significantly repressed PTN transcription, but indirectly inhibited RPTP β/ζ expression through repressing PTN expression. Further studies revealed that menin-regulated cell migration through PTN/RPTP β/ζ, in conjunction with integrin α_vβ₃, focal adhesion kinase, phosphatidylinositol 3-kinase and phosphorylated extracellular signal regulated kinase 1/2. These findings provide mechanistic insights into the molecular basis for menin/PTN-mediated regulation of A549 lung cancer cell migration.

Suppression of lung adenocarcinoma through menin and polycomb gene-mediated repression of growth factor pleiotrophin

Menin upregulates transcription of cell-cycle inhibitors to suppress endocrine tumors, but it is poorly understood how menin suppresses non-endocrine tumors such as lung cancer. Here, we show that menin inhibits proliferation of human lung cancer cells and growth of lung cancer in mice. The menin-mediated tumor suppression requires repression of growth factor pleiotrophin (PTN), which binds to its cell surface receptor, anaplastic lymphoma kinase (ALK) that is activated in certain lung adenocarcinomas. Menin represses PTN transcription and PTN-induced proliferation of human lung cancer cells, and menin expression is substantially reduced in primary human lung adenocarcinomas. Notably, menin binds the PTN locus and enhances Polycomb gene Enhancer of Zeste homolog 2 (EZH2)-mediated histone H3 lysine 27 trimethylation (H3K27m3), a negative mark for gene transcription but does not affect histone H3K4 methylation that is usually upregulated by menin in endocrine cells. Together, our findings indicate that menin suppresses lung cancer partly through increasing Polycomb gene-mediated H3K27 methylation and repressing PTN transcription, unraveling a novel, epigenetically regulated PTN-ALK signaling pathway in suppressing lung cancer.

Pleiotrophin produced by multiple myeloma induces transdifferentiation of monocytes into vascular endothelial cells: a novel mechanism of tumor-induced vasculogenesis

Enhanced angiogenesis is a hallmark of cancer. Pleiotrophin (PTN) is an angiogenic factor that is produced by many different human cancers and stimulates tumor blood vessel formation when it is expressed in malignant cancer cells. Recent studies show that monocytes may give rise to vascular endothelium. In these studies, we show that PTN combined with macrophage colony-stimulating factor (M-CSF) induces expression of vascular endothelial cell (VEC) genes and proteins in human monocyte cell lines and monocytes from human peripheral blood (PB). Monocytes induce VEC gene expression and develop tube-like structures when they are exposed to serum or cultured with bone marrow (BM) from patients with multiple myeloma (MM) that express PTN, effects specifically blocked with antiPTN antibodies. When coinjected with human MM cells into severe combined immunodeficient (SCID) mice, green fluorescent protein (GFP)-marked human monocytes were found incorporated into tumor blood vessels and expressed human VEC protein markers and genes that were blocked by anti-PTN antibody. Our results suggest that vasculogenesis in human MM may develop from tumoral production of PTN, which orchestrates the transdifferentiation of monocytes into VECs.

Metastasis signatures: genes regulating tumor-microenvironment interactions predict metastatic behavior

The possibility of predicting clinical outcome of cancer patients through the analysis of gene expression profiles in the primary tumor is a kind of ideological revolution as the multistep carcinogenesis model postulates that the proportion of cells within the primary tumor that actually acquire metastasis driving mutation(s) is small; too small to leave its imprint on the gene expression profile. The data collected to date have brought a new paradigm to reality in the metastasis field: metastasis must at least in part rely on mutations and/or gene regulation events present in the majority of cells which constitute the primary tumor mass. By analyses of differential expression of primary tumors versus metastases or by functional analyses of putative metastasis genes in experimental metastasis, many metastasis-associated gene expression events have been identified that correlate with the development of metastases. Among genes "favoring" metastasis, we find many molecules that are expressed not by the tumor cell itself but by the cells of the microenvironment, as well as genes over-expressed in the primary tumor that have a principle role in mediating tumor-host interactions. Here we review these concepts and advance hypotheses on how gene expression of the primary tumor and the microenvironment can favor the spread of the metastasis seeds and how this knowledge can provide tools to secondary prevention.

The receptor protein tyrosine phosphatase (RPTP)beta/zeta is expressed in different subtypes of human breast cancer

Increasing evidence suggests mutations in human breast cancer cells that induce inappropriate expression of the 18-kDa cytokine pleiotrophin (PTN, Ptn) initiate progression of breast cancers to a more malignant phenotype. Pleiotrophin signals through inactivating its receptor, the receptor protein tyrosine phosphatase (RPTP)beta/zeta, leading to increased tyrosine phosphorylation of different substrate proteins of RPTPbeta/zeta, including beta-catenin, beta-adducin, Fyn, GIT1/Cat-1, and P190RhoGAP. PTN signaling thus has wide impact on different important cellular systems. Recently, PTN was found to activate anaplastic lymphoma kinase (ALK) through the PTN/RPTPbeta/zeta signaling pathway; this discovery potentially is very important, since constitutive ALK activity of nucleophosmin (NPM)-ALK fusion protein is causative of anaplastic large cell lymphomas, and, activated ALK is found in other malignant cancers. Recently ALK was identified in each of 63 human breast cancers from 22 subjects. We now demonstrate that RPTPbeta/zeta is expressed in each of these same 63 human breast cancers that previously were found to express ALK and in 10 additional samples of human breast cancer. RPTPbeta/zeta furthermore was localized not only in its normal association with the cell membrane but also scattered in cytoplasm and in nuclei in different breast cancer cells and, in the case of infiltrating ductal carcinomas, the distribution of RPTPbeta/zeta changes as the breast cancer become more malignant. The data suggest that the PTN/RPTPbeta/zeta signaling pathway may be constitutively activated and potentially function to constitutively activate ALK in human breast cancer.

Pleiotrophin expression in astrocytic and oligodendroglial tumors and it’s correlation with histological diagnosis, microvascular density, cellular proliferation and overall survival

BACKGROUND

Pleiotrophin (PTN) is a secreted cytokine with several properties related with tumor development, including differentiation, angiogenesis, invasion, apoptosis and metastasis. There is evidence that PTN has also a relevant role in primary brain neoplasms and its inactivation could be important to treatment response. Astrocytic and oligodendroglial tumors are the most frequent primary brain neoplasms. Astrocytic tumors are classified as pilocytic astrocytoma (PA), diffuse astrocytoma (DA), anaplastic astrocytoma (AA) and glioblastoma (GBM). Oligodendroglial tumors are classified as oligodendroglioma (O) and anaplastic oligodendroglioma (AO). The aim of the present study was to compare PTN expression, in astrocytomas and oligodendrogliomas and its association with the histological diagnosis, microvascular density, proliferate potential and clinical outcome.

METHODS

Seventy-eight central nervous system tumors were analyzed. The histological diagnosis in accordance with WHO classification was: 13PA, 18DA, 8AA, 15GBM, 16O and 8AO. Immunohistochemistry was realized with these specific antibodies: pleiotrophin, CD31 to microvascular density and Ki-67 to cell proliferation.

RESULTS

PTN expression was significantly higher in GBM and AA when compared to PA and higher in GBM compared to DA. PTN expression did not differ between O and AO. Proliferate index and microvascular density were evaluated only in high grade tumors (AA, GBM and AO) divided in three groups according to PTN expression (low, intermediate and high). These results showed no statistical difference between PTN expression and index of cellular proliferation and neither to PTN expression and microvascular density. Overall survival (OS) analysis (months) showed similar results in high grade gliomas with different levels of PTN expression.

CONCLUSIONS

Our results suggest that PTN expression is associated with histopathological grade of astrocytomas. Proliferation rate, microvascular density and overall survival do not seem to be associated with PTN expression.

Dominant negative pleiotrophin induces tetraploidy and aneuploidy in U87MG human glioblastoma cells

Pleiotrophin (PTN, Ptn) is an 18kDa secretory cytokine that is expressed in many human cancers, including glioblastoma. In previous experiments, interruption of the constitutive PTN signaling in human U87MG glioblastoma cells that inappropriately express endogenous Ptn reversed their rapid growth in vitro and their malignant phenotype in vivo. To seek a mechanism for the effect of the dominant-negative PTN, flow cytometry was used to compare the profiles of U87MG cells and four clones of U87MG cells that express the dominant-negative PTN (U87MG/PTN1-40 cells); here, we report that the dominant-negative PTN in U87MG cells induces tetraploidy and aneuploidy and arrests the tetraploid and aneuploid cells in the G1 phase of the cell cycle. The data suggest that PTN signaling may have a critical role in chromosomal segregation and cell cycle progression; the data suggest induction of tetraploidy and aneuploidy in U87MG glioblastoma cells may be an important mechanism that contributes to the loss of the malignant phenotype of U87MG cells.

The pluripotent cytokine pleiotrophin is induced by wounding in human mesangial cells

Mesangial re-modeling and mesangial cell (MC) migration are features of several glomerular diseases including mesangiocapillary glomerulonephritis. In vitro investigations have recently identified ADAM-15, a multidomain adamalysin, as central to the migration of MC. The current study used array technology to investigate the expression of other genes in migrating cells and identified pleiotrophin (PTN), platelet-derived growth factor alpha polypeptide chain, colony stimulating factor, and four members of the tumor necrosis factor-alpha superfamily as major genes that were upregulated. Transcriptional induction of PTN was confirmed by reverse transcription-polymerase chain reaction and Northern blotting and induction of the protein by Western blotting and immunohistochemical localization. PTN was observed associated with mesangial 'hillocks' in confluent MC cultures. In contrast, in models of migration, migrating cells had the highest expression of cell-associated PTN. PTN protein was less evident, however, in the conditioned medium of MCs. Treatment of MC with heparanase removed PTN from the cells suggesting that its localization was owing to an association with heparan sulfates on the cell surface or in the extracellular matrix. This is the first description of the expression of PTN by human MCs and the data suggest that it is rapidly induced in cells that are triggered to migrate. The result of this induction is currently under investigation.

Dominant-stable beta-catenin expression causes cell fate alterations and Wnt signaling antagonist expression in a murine granulosa cell tumor model

Wnt/beta-catenin signaling is normally involved in embryonic development and tissue homeostasis, and its misregulation leads to several forms of cancer. We have reported that misregulated Wnt/beta-catenin signaling occurs in ovarian granulosa cell tumors (GCT) and have created the Catnb(flox(ex3)/+);Amhr2(cre/+) mouse model, which expresses a dominant-stable mutant of beta-catenin in granulosa cells and develops late-onset GCT. To study the mechanisms leading to GCT development, gene expression analysis was done using microarrays comparing Catnb(flox(ex3)/+);Amhr2(cre/+) ovaries bearing pretumoral lesions with control ovaries. Overexpressed genes identified in Catnb(flox(ex3)/+);Amhr2(cre/+) ovaries included the Wnt/beta-catenin signaling antagonists Wif1, Nkd1, Dkk4, and Axin2, consistent with the induction of negative feedback loops that counteract uncontrolled Wnt/beta-catenin signaling. Expression of the antagonists was localized to cells forming the pretumoral lesions but not to normal granulosa cells. Microarray analyses also revealed the ectopic expression of bone markers, including Ibsp, Cdkn1c, Bmp4, and Tnfrsf11b, as well as neuronal/neurosecretory cell markers, such as Cck, Amph, Pitx1, and Sp5. Increased expression of the gene encoding the cytokine pleiotrophin was also found in Catnb(flox(ex3)/+);Amhr2(cre/+) ovaries and GCT but was not associated with increased serum pleiotrophin levels. In situ hybridization analyses using GCT from Catnb(flox(ex3)/+);Amhr2(cre/+) mice revealed that Wnt/beta-catenin antagonists and neuronal markers localized to a particular cell population, whereas the bone markers localized to a distinct cell type associated with areas of osseous metaplasia. Together, these results suggest that misregulated Wnt/beta-catenin signaling alters the fate of granulosa cells and that the GCT that arise in Catnb(flox(ex3)/+);Amhr2(cre/+) mice result from the clonal expansion of metaplastic cells.

PTEN deletion leads to up-regulation of a secreted growth factor pleiotrophin

Tumor suppressor gene PTEN is highly mutated in a wide variety of human tumors. To identify unknown targets or signal transduction pathways that are regulated by PTEN, microarray analysis was performed to compare the gene expression profiles of Pten null mouse embryonic fibroblasts (MEFs) cell lines and their isogenic counterparts. Expression of a heparin binding growth factor, pleiotrophin (Ptn), was found to be up-regulated in Pten-/- MEFs as well as Pten null mammary tumors. Further experiments revealed that Ptn expression is regulated by the PTEN-PI3K-AKT pathway. Knocking down the expression of Ptn by small interfering RNA resulted in the reduction of Akt and GSK-3beta phosphorylation and suppression of the growth and the tumorigenicity of Pten null MEFs. Our results suggest that PTN participates in tumorigenesis caused by PTEN loss and PTN may be a potential target for anticancer therapy, especially for those tumors with PTEN deficiencies.

Molecular characterization of salivary gland malignancy using the Smgb-Tag transgenic mouse model

The molecular mechanisms underlying salivary gland tumorigenesis remain unclear. In order to identify genetic changes that occur during the development of invasive adenocarcinoma from normal salivary gland, we used the Smgb-Tag transgenic mouse model. This transgene induces the progressive development of dysplasia to invasive adenocarcinoma in the submandibular salivary gland. Gene expression patterns from 20 submandibular glands (two normal, nine dysplasia and nine adenocarcinoma samples) were assessed using a mouse 15 K cDNA array. Unsupervised hierarchical clustering was used to group gene expression based on 157 differentially expressed genes distinguishing between dysplasias and adenocarcinomas. Further analysis identified 25 significantly overexpressed and 28 underexpressed cDNA sequences in adenocarcinoma as compared to dysplasia. Differential expression of five genes (Lcn2, Ptn, Cd24a, Mapk6 and Rnps1) was validated by quantitative real-time RT-PCR in a total of 48 mouse salivary gland tissues (seven histologically normal, 13 dysplasias and 28 adenocarcinomas), including the 20 samples analyzed by cDNA arrays. Immunohistochemical analysis was used to validate the expression of Ptn and Cd24a at the protein level in a subset of 16 mouse salivary glands (four normal, five dysplasia and seven adenocarcinoma samples), as well as in 23 human submandibular gland tumors (16 pleomorphic adenomas, three adenoid cystic carcinomas, one acinic cell carcinoma, one adenocarcinoma NOS, one myoepithelial and one mucoepidermoid carcinoma). We thus demonstrated that the Smgb-Tag transgenic mouse model is a useful tool for the identification of genes that are deregulated in salivary gland adenocarcinomas. Our data suggest that Ptn and Cd24a may be genetic markers associated with salivary gland tumorigenesis and/or progression.

Midkine, a newly discovered regulator of the renin–angiotensin pathway in mouse aorta: Significance of the pleiotrophin/midkine developmental gene family in angiotensin II signaling

We previously demonstrated that pleiotrophin (PTN the protein, Ptn the gene) highly regulates the levels of expression of the genes encoding the proteins of the renin-angiotensin pathway in mouse aorta. We now demonstrate that the levels of expression of these same genes are significantly regulated in mouse aorta by the PTN family member midkine (MK the protein, Mk the gene); a 3-fold increase in expression of renin, an 82-fold increase in angiotensinogen, a 6-fold decrease in the angiotensin converting enzyme, and a 6.5-fold increase in the angiotensin II type 1 and a 9-fold increase in the angiotensin II type 2 receptor mRNAs were found in Mk-/- mouse aorta in comparison with the wild type (WT, +/+). The results in Mk-/- mice are remarkably similar to those previously reported in Ptn-/- mouse aorta, with the single exception of that the levels of the angiotensinogen gene expression in Ptn-/- mice are equal to those in WT+/+ mouse aorta, and thus, in contrast to Mk gene expression unaffected by levels of Ptn gene expression. The data indicate that MK and PTN share striking but not complete functional redundancy. These data support potentially high levels importance of MK and the MK/PTN developmental gene family in downstream signals initiated by angiotensin II either in development or in the many pathological conditions in which MK expression levels are increased, such as atherosclerosis and many human neoplasms that acquire constitutive endogenous Mk gene expression by mutation during tumor progression and potentially provide a target through the renin-angiotensin pathway to treat advanced malignancies.

Pleiotrophin expression correlates with melanocytic tumor progression and metastatic potential

BACKGROUND

Gene expression profiling of melanoma and nevic tissue has demonstrated that pleiotrophin (PTN) is significantly overexpressed in human melanomas.

METHODS

To further evaluate PTN expression in melanocytic lesions, protein immunohistochemistry was performed on the spectrum of melanocytic lesions.

RESULTS

Melanocytic nevi were consistently negative (n=58). In contrast, the great majority of metastatic melanomas were positive (33/34, 97%). The analysis of 34 primary melanomas demonstrated PTN positivity in 20 lesions while 14 lesions were negative. Within the primary melanomas, PTN immunoreactivity was associated with metastasis (p=0.0004) and decreased melanoma-related survival (p=0.0444). Univariate analysis of PTN immunoreactivity predicted an increased risk for metastasis (relative risk 9.1, p=0.003).

CONCLUSIONS

The results of this study confirm previous gene profiling data showing differential PTN expression between melanocytic nevi and melanomas. In addition, lesional PTN expression is associated with metastatic potential and may be a prognostic factor for melanomas.

Ribozyme-targeting reveals the rate-limiting role of pleiotrophin in glioblastoma

Glioblastomas (GBMs) are the most frequent malignant brain tumors with very limited treatment options and nearly all GBM patients dying within 1 year. Pleiotrophin (PTN, HB-GAM, HBNF, OSF-1) is a secreted growth factor that shows mitogenic, chemotactic and transforming activity. While PTN expression is tightly regulated during embryogenesis and very limited in normal adult tissues, a marked PTN upregulation is seen in tumors including glioblastomas. Targeting of the PTN receptors, ALK and RPTP-zeta, indicates a contribution of PTN-activated signaling pathways in glioblastomas. However, the relevance of PTN expression itself is unknown especially since, besides PTN, at least one more growth factor, midkine (MK), signals through ALK and is expressed in glioblastoma. Here we demonstrate the biologic relevance of PTN in 2 glioblastoma cell lines in vitro and in vivo. We show that stable ribozyme-targeting leads to a robust reduction of PTN mRNA and protein levels. This results in decreased cell proliferation, cell migration and soft agar colony formation in vitro. Comparing clonal ribozyme-transfected cells with different residual PTN levels, we establish a PTN gene-dose effect of glioblastoma cell proliferation. In a subcutaneous tumor xenograft mouse model, in vivo growth is markedly reduced upon PTN depletion, which is paralleled by decreased PTN serum levels. Furthermore, the immunohistochemical analysis of the tumors shows reduced angiogenesis in PTN-depleted tumors. We conclude that PTN is a rate-limiting growth factor in glioblastoma. Since PTN is overexpressed in glioblastomas but rarely found in normal tissue, PTN may represent an attractive therapeutic target.

Ribozyme targeting of the growth factor pleiotrophin in established tumors: a gene therapy approach

The growth and metastasis of solid tumors relies on the activities of polypeptide growth factors to recruit stromal tissue and expand the tumor mass. Pleiotrophin (PTN) is a secreted growth factor with angiogenic activity that has been found to contribute to the growth and metastasis of tumors including melanoma. Here, we present a gene therapy approach of targeting PTN in established tumors using ribozymes. Tetracycline-regulated ribozyme expression vectors were used to deplete conditionally PTN mRNA from melanoma xenograft tumors in vivo. We found that tetracycline-mediated initiation of ribozyme expression in established tumors reduced further tumor growth. Next, we generated synthetic anti-PTN ribozymes that inhibit PTN-dependent colony formation of cells in soft agar. Intraperitoneal administration of these synthetic ribozymes into nude mice inhibited growth of PTN-positive, subcutaneous melanoma. Furthermore, PTN released from the tumors into the circulation of mice was reduced after ribozyme treatment. These data show that ribozyme targeting of rate-limiting tumor growth factors could provide an efficient tool for cancer therapy and that the efficacy may be reflected in the reduction of the serum levels of the targeted protein, PTN.

The mRNA profile of genes in betel quid chewing oral cancer patients

Oral cancer is one of the most common types of human cancer in the world. Although the risk factors for oral cancer are well-recognized in different countries, the molecular mechanism responsible for this malignancy remains elusive particularly in the countries where betel quid chewing is prevalent. The cDNA microarray analysis was used to analyse the mRNA expression patterns of 1177 genes in ten oral cancer patients with betel quid chewing history. Eighty-four genes involving cell adhesion, cell shape, growth, apoptosis, angiogenesis, metastasis, and metabolism were deregulated. Although the expression profile of these genes was shared by certain clinical patients, there was no significant association of the expression profile with clinical staging. Functional implication of four validated genes including caspase-1, STAT-1, COX-2 and pleiotrophin was discussed. This study provides pilot data for understanding the pathogenesis of oral cancer in countries like Taiwan where betel quid chewing is prevalent.

Marked increase of the growth factors pleiotrophin and fibroblast growth factor-2 in serum of testicular cancer patients

BACKGROUND

Malignant tumors of the testis are among the most common cancers in men between the ages of 15 and 30 years. The sensitivity of detection of known tumor markers depends upon the tumor histology and stage. In other cancers, increased serum concentrations of various angiogenic growth factors have been described as potential markers for tumor progression and metastasis. One main histological feature of testicular cancer is profound angiogenesis.

DESIGN

In this study, we investigated by sensitive enzyme-linked immunosorbent assays (ELISAs) the levels of various growth and angiogenesis factors in the serum of testicular cancer patients as compared with normal control subjects. For the most profoundly increased growth factors, pleiotrophin (PTN) and fibroblast growth factor-2 (FGF-2), we furthermore analyzed tumor lysates by northern blotting, RT-PCR and ELISA.

RESULTS

We demonstrate a marked elevation of average serum levels of PTN ( approximately 20-fold) and of FGF-2 ( approximately 7-fold) in patients and expression of both growth factors in tumor biopsies. To a lesser extent, vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) serum levels were increased, whereas FGF-4 and transforming growth factor-beta levels were similar to those in normal control subjects. Elevation of PTN, FGF-2, EGF and VEGF was detected in seminomatous as well as non-seminatous tumors, and even in early stages.

CONCLUSIONS

PTN and FGF-2 may represent promising new diagnostic markers for testicular cancer with high sensitivity even in early-stage testicular cancer. Further studies are warranted to extend our analyses.

Midkine binds to anaplastic lymphoma kinase (ALK) and acts as a growth factor for different cell types

Midkine (MK) is a developmentally regulated, secreted growth factor homologous to pleiotrophin (PTN). To investigate the potential role of MK in tumor growth, we expressed MK in human SW-13 cells and studied receptor binding, signal transduction, and activity of MK. The MK protein stimulates soft agar colony formation in vitro and tumor growth of SW-13 cells in athymic nude mice, as well as proliferation of human endothelial cells from brain microvasculature and umbilical vein (HUVEC) in the low ng/ml range. MK binds to anaplastic lymphoma kinase (ALK), the receptor for PTN, with an apparent K(d) of 170 pm in intact cells, and this receptor binding of MK is competed by PTN with an apparent K(d) of approximately 20 pm. Monoclonal antibodies raised against the extracellular ligand-binding domain of ALK inhibit ALK receptor binding of MK as well as MK-stimulated colony formation of SW-13 cells. Furthermore, MK stimulates ALK phosphorylation in WI-38 human fibroblasts and activates PI3-kinase and MAP kinase signal transduction in WI-38, HUVEC, neuroblastoma (SH SY-5Y) and glioblastoma (U87MG) cells that express the ALK protein. We conclude that MK can act as a growth, survival, and angiogenic factor during tumorigenesis and signals through the ALK receptor.