Pleiotrophin, a candidate gene for poor tumor vasculature and in vivo neuroblastoma sensitivity to irinotecan

Protein Tyrosine Phosphatases in Neuroblastoma: Emerging Roles as Biomarkers and Therapeutic Targets

Neuroblastoma is a type of cancer intimately related with early development and differentiation of neuroendocrine cells, and constitutes one of the pediatric cancers with higher incidence and mortality. Protein tyrosine phosphatases (PTPs) are key regulators of cell growth and differentiation by their direct effect on tyrosine dephosphorylation of specific protein substrates, exerting major functions in the modulation of intracellular signaling during neuron development in response to external cues driving cell proliferation, survival, and differentiation. We review here the current knowledge on the role of PTPs in neuroblastoma cell growth, survival, and differentiation. The potential of PTPs as biomarkers and molecular targets for inhibition in neuroblastoma therapies is discussed.

Pleiotrophin promotes vascular abnormalization in gliomas and correlates with poor survival in patients with astrocytomas

Glioblastomas are aggressive astrocytomas characterized by endothelial cell proliferation and abnormal vasculature, which can cause brain edema and increase patient morbidity. We identified the heparin-binding cytokine pleiotrophin as a driver of vascular abnormalization in glioma. Pleiotrophin abundance was greater in high-grade human astrocytomas and correlated with poor survival. Anaplastic lymphoma kinase (ALK), which is a receptor that is activated by pleiotrophin, was present in mural cells associated with abnormal vessels. Orthotopically implanted gliomas formed from GL261 cells that were engineered to produce pleiotrophin showed increased microvessel density and enhanced tumor growth compared with gliomas formed from control GL261 cells. The survival of mice with pleiotrophin-producing gliomas was shorter than that of mice with gliomas that did not produce pleiotrophin. Vessels in pleiotrophin-producing gliomas were poorly perfused and abnormal, a phenotype that was associated with increased deposition of vascular endothelial growth factor (VEGF) in direct proximity to the vasculature. The growth of pleiotrophin-producing GL261 gliomas was inhibited by treatment with the ALK inhibitor crizotinib, the ALK inhibitor ceritinib, or the VEGF receptor inhibitor cediranib, whereas control GL261 tumors did not respond to either inhibitor. Our findings link pleiotrophin abundance in gliomas with survival in humans and mice, and show that pleiotrophin promotes glioma progression through increased VEGF deposition and vascular abnormalization.

The role of pleiotrophin in bone repair

Bone has an enormous capacity for growth, regeneration, and remodelling, largely due to induction of osteoblasts that are recruited to the site of bone formation. Although the pathways involved have not been fully elucidated, it is well accepted that the immediate environment of the cells is likely to play a role via cell–matrix interactions, mediated by several growth factors. Formation of new blood vessels is also significant and interdependent to bone formation, suggesting that enhancement of angiogenesis could be beneficial during the process of bone repair. Pleiotrophin (PTN), also called osteoblast-specific factor 1, is a heparin-binding angiogenic growth factor, with a well-defined and significant role in both physiological and pathological angiogenesis. In this review we summarise the existing evidence on the role of PTN in bone repair.

Pleiotrophin is a potential colorectal cancer prognostic factor that promotes VEGF expression and induces angiogenesis in colorectal cancer

PURPOSE

Pleiotrophin (PTN) is an important developmental secretory cytokine expressed in many types of cancer and involved in angiogenesis and tumor growth; however, the significance of PTN expression in colorectal cancer (CRC) has not been established.

METHODS

Immunohistochemistry, western blot, and enzyme-linked immunosorbent assay were used to detect PTN expression in CRC patients. The relationship between PTN expression and clinicopathological characteristics and survival time was statistically analyzed, and the relationship between PTN and vascular endothelial growth factor (VEGF) in tumor angiogenesis was further analyzed.

RESULTS

Of CRC tissues, 74.70% (62/83) stained positive, with a strong positive ratio of 60.24% (50/83). The expression of PTN in CRC tissues was much higher than in normal colorectal tissues. PTN serum levels in CRC patients (mean = 254.59 ± 261.76 pg/ml) were significantly higher than those of normal volunteers (mean = 115.23 ± 79.53 pg/ml; p < 0.001). PTN expression was related to CRC differentiation and TNM staging. High level of PTN is a predictor of a poor prognosis and high expression of PTN is accompanied by high expression of VEGF in CRC patients. Investigation of the relationship between PTN and VEGF revealed that PTN, through the PTN/RPTPβ/ζ signaling pathway, increased tyrosine phosphorylation of β-catenin, leading to an increase in VEGF.

CONCLUSIONS

Our study identifies PTN as an essential growth factor for CRC. PTN promotes VEGF expression and cooperates with VEGF in promoting CRC angiogenesis. PTN could serve as a prognostic factor for this cancer. Considering that PTN shows very limited expression in normal tissue, it may represent an attractive new target for CRC therapy.

Stromal compartment as a survival prognostic factor in advanced ovarian carcinoma

OBJECTIVE

We investigated the prognostic significance of stromal compartment on the overall survival of patients with advanced epithelial ovarian cancer.

METHODS

We evaluated retrospectively the stroma proportion of the tumor surgical specimens of 194 patients with stages III and IV disease, using histochemical staining and fully automatic virtual slide processing. The prognostic significance of stroma proportion and clinical parameters were evaluated using log-rank test and Cox regression.

RESULTS

Stroma proportion was found to be an independent prognostic factor by both univariate (P = 0.016) and multivariate analyses (hazards ratio = 1.45, P = 0.011).

CONCLUSION

The present data indicate that a high stroma proportion is related to a poor prognosis of stage III and IV ovarian carcinomas.

Anaplastic lymphoma kinase: role in cancer pathogenesis and small-molecule inhibitor development for therapy

Anaplastic lymphoma kinase (ALK), a receptor tyrosine kinase in the insulin receptor superfamily, was initially identified in constitutively activated oncogenic fusion forms - the most common being nucleophosmin-ALK - in anaplastic large-cell lymphomas, and subsequent studies have identified ALK fusions in diffuse large B-cell lymphomas, systemic histiocytosis, inflammatory myofibroblastic tumors, esophageal squamous cell carcinomas and non-small-cell lung carcinomas. More recently, genomic DNA amplification and protein overexpression, as well as activating point mutations, of ALK have been described in neuroblastomas. In addition to those cancers for which a causative role for aberrant ALK activity is well validated, more circumstantial links implicate the full-length, normal ALK receptor in the genesis of other malignancies - including glioblastoma and breast cancer - via a mechanism of receptor activation involving autocrine and/or paracrine growth loops with the reported ALK ligands, pleiotrophin and midkine. This review summarizes normal ALK biology, the confirmed and putative roles of ALK in the development of human cancers and efforts to target ALK using small-molecule kinase inhibitors.

New approaches to pharmacotherapy of tumors of the nervous system during childhood and adolescence

Tumors of the nervous system are among the most common and most chemoresistant neoplasms of childhood and adolescence. Malignant tumors of the brain collectively account for 21% of all cancers and 24% of all cancer-related deaths in this age group. Neuroblastoma, a peripheral nervous system tumor, is the most common extracranial solid tumor of childhood, and 65% of children with this tumor have only a 10 or 15% chance of living 5 years beyond the time of initial diagnosis. Novel pharmacological approaches to nervous system tumors are urgently needed. This review presents the role of and current challenges to pharmacotherapy of malignant tumors of the nervous system during childhood and adolescence and discusses novel approaches aimed at overcoming these challenges.

Subclassification and individual survival time prediction from gene expression data of neuroblastoma patients by using CASPAR

PURPOSE

To predict individual survival times for neuroblastoma patients from gene expression data using the cancer survival prediction using automatic relevance determination (CASPAR) algorithm.

EXPERIMENTAL DESIGN

A first set of oligonucleotide microarray gene expression profiles comprising 256 neuroblastoma patients was generated. Then, CASPAR was combined with a leave-one-out cross-validation to predict individual times for both the whole cohort and subgroups of patients with unfavorable markers, including stage 4 disease (n = 67), unfavorable genetic alterations, intermediate-risk or high-risk stratification by the German neuroblastoma trial, and patients predicted as unfavorable by a recently described gene expression classifier (n = 83). Prediction accuracy of individual survival times was assessed by Kaplan-Meier analyses and time-dependent receiver operator characteristics curve analyses. Subsequently, classification results were validated in an independent cohort (n = 120).

RESULTS

CASPAR separated patients with divergent outcome in both the initial and the validation cohort [initial set, 5y-OS 0.94 +/- 0.04 (predicted long survival) versus 0.38 +/- 0.17 (predicted short survival), P < 0.0001; validation cohort, 5y-OS 0.94 +/- 0.07 (long) versus 0.40 +/- 0.13 (short), P < 0.0001]. Time-dependent receiver operator characteristics analyses showed that CASPAR-predicted individual survival times were highly accurate (initial set, mean area under the curve for first 10 years of overall survival prediction 0.92 +/- 0.04; validation set, 0.81 +/- 0.05). Furthermore, CASPAR significantly discriminated short (<5 years) from long survivors (>5 years) in subgroups of patients with unfavorable markers with the exception of MYCN-amplified patients (initial set). Confirmatory results with high significance were observed in the validation cohort [stage 4 disease (P = 0.0049), NB2004 intermediate-risk or high-risk stratification (P = 0.0017), and unfavorable gene expression prediction (P = 0.0017)].

CONCLUSIONS

CASPAR accurately forecasts individual survival times for neuroblastoma patients from gene expression data.

Early evaluation of the effects of chemotherapy with longitudinal FDG small-animal PET in human testicular cancer xenografts: early flare response does not reflect refractory disease

AIM

We aimed to evaluate the usefulness of FDG PET in the early prediction of the effects of chemotherapy on human testicular cancer xenografts.

MATERIAL AND METHODS

Nude rats bearing subcutaneous human embryonal carcinoma xenografts received either cisplatin (5 mg/kg) or saline serum. Small-animal PET studies were performed on days 0, 2, 4 and 7 and compared to immunochemistry studies, flow cytometry studies and hexokinase assays.

RESULTS

Cisplatin treatment resulted in biphasic FDG uptake evolution: a peak was observed on day 2, followed by a marked decrease on day 7 despite an insignificant change in tumour volume. Similarly, a peak in cyclin A immunostaining was observed on days 2 and 4), followed by a significant decrease on day 7. Flow cytometry showed that the cyclin A peak was not related to increased cell proliferation but was due to a transient S and G(2)/M cell cycle arrest. A marked increase in cell apoptosis was observed from day 2 to day 7. GLUT-1 showed a significant decrease on day 7. Macrophagic infiltrate remained stable except for an increase observed on day 7. In control tumours, continuous growth was observed, all immunostaining markers remaining stable over time. Hexokinase activity was significantly lower on day 7 in treated tumours than in controls.

CONCLUSION

FDG PET may be useful in the early evaluation of treatment in patients with testicular cancer. In our model, a very early increased [(18)F]-FDG uptake was related to a transient cell cycle arrest and early stage apoptosis but did not reveal refractory disease.

Activating mutations in ALK provide a therapeutic target in neuroblastoma

Neuroblastoma, an embryonal tumor of the peripheral sympathetic nervous system, accounts for approximately 15% of all deaths due to childhood cancer1. High-risk neuroblastomas, prevalent in the majority of patients, are rapidly progressive; even with intensive myeloablative chemotherapy, relapse is common and almost uniformly fatal2,3. Here we report the detection of previously unknown mutations in the ALK gene, which encodes a receptor tyrosine kinase, in 8% of primary neuroblastomas. Five non-synonymous sequence variations were identified in the kinase domain of ALK, of which three were somatic and two were germline. The most frequent mutation, F1174L, was also identified in three different neuroblastoma cell lines. ALK cDNAs encoding the F1174L and R1275Q variants, but not the wild-type ALK cDNA, transformed IL-3-dependent murine hematopoietic Ba/F3 cells to cytokine-independent growth. Ba/F3 cells expressing these mutations were sensitive to a small-molecule inhibitor of ALK, TAE6844. Furthermore, two human neuroblastoma cell lines harboring the F1174L mutation were sensitive to the inhibitor. Cytotoxicity was associated with increased levels of apoptosis as measured by TUNEL-labeling. shRNA-mediated knockdown of ALK expression in neuroblastoma cell lines with the F1174L mutation also resulted in apoptosis and impaired cell proliferation. Thus, activating alleles of the ALK receptor tyrosine kinase are present in primary neuroblastoma tumors and in established neuroblastoma cell lines, and confer sensitivity to ALK inhibition with small molecules, providing a molecular rationale for targeted therapy of this disease.

A phase II study of irinotecan in children with relapsed or refractory neuroblastoma: a European cooperation of the Société Française d'Oncologie Pédiatrique (SFOP) and the United Kingdom Children Cancer Study Group (UKCCSG)

PURPOSE

To evaluate the efficacy and safety of irinotecan in paediatric recurrent or refractory neuroblastoma.

PATIENTS AND METHODS

Thirty seven patients aged between 6 months and < or = 20 years, with relapsed or refractory neuroblastoma, received irinotecan at 600 mg/m(2) administered as a 60-min infusion, every 3 weeks. Tumour response was evaluated by conventional radiological and mIBG scans every two cycles.

RESULTS

No objective response was observed during the study. Stable disease was observed in 13% of evaluable patients. Median times to progression and survival were 1.4 months (range, 1.2-1.5 months) and 8.8 months (range, 6.7-11.3 months), respectively. One forty two cycles were administered, with a median of two cycles per patient (range, 1-17 cycles). The most common grade 3-4 toxicities were neutropenia (65% of patients), anaemia (43%), thrombocytopenia (38%), vomiting (14%), abdominal pain or cramping (8%), and nausea (5%).

CONCLUSION

Irinotecan administered intravenously as a single agent every 3 weeks induced no objective response in relapsed or refractory neuroblastoma.

Usefulness of automatic quantification of immunochemical staining on whole tumor sections for correlation with oncological small animal PET studies: an example with cell proliferation, glucose transporter 1 and FDG

AIM

To highlight the use of automatic quantification of immunochemical staining on digitized images of whole tumor sections in preclinical positron emission tomography (PET) studies.

MATERIALS AND METHODS

Xenografted human testicular tumors (36) were imaged with 2-deoxy-2[F-18]fluoro-D: -glucose (FDG) small animal PET (SA-PET). Tumor cell proliferation and glucose transportation were assessed with cyclin A and Glut-1 immunostaining. Tumor slides were digitized and processed with PixCyt software enabling whole slide quantification, then compared with junior and senior pathologist manual scoring. Manual and automatic quantification results were correlated to FDG uptake.

RESULTS

For cyclin A, inter- and intra-observer agreement for manual scoring was 0.52 and 0.72 and concordance between senior pathologist and automatic quantification was 0.84. Correlations between Tumor/Background ratio and tumor cell proliferation assessed by automatic quantification, junior and senior pathologists were 0.75, 0.55, and 0.61, respectively. Correlation between Tumor/Background ratio and Glut-1 assessed by automatic quantification was 0.74.

CONCLUSION

Automatic quantification of immunostaining is a valuable tool to overcome inter- and intra-observer variability for correlation of cell proliferation or other markers with tumor tracer uptake.

Heparin affin regulatory peptide/pleiotrophin negatively affects diverse biological activities in C6 glioma cells

Heparin affin regulatory peptide (HARP) or pleiotrophin seems to be involved in the progression of several tumors of diverse origin. In this study, we tried to determine the role of HARP in rat C6 glioma cells by using an antisense strategy for inhibition of HARP expression. Decrease of the expression of endogenous HARP in C6 cells (AS-C6 cells) significantly increased proliferation, migration, and anchorage-independent growth of cells. Implantation of AS-C6 cells onto chicken embryo chorioallantoic membranes resulted in a significant increase of tumor-induced angiogenesis compared with that induced by non-transfected or C6 cells transfected with the plasmid alone (PC-C6 cells). In the same line, conditioned medium from AS-C6 cells significantly increased endothelial cell proliferation, migration, and tube formation in vitro compared with the effect of conditioned medium from C6 or PC-C6 cells. Interestingly, vascular endothelial growth factor (VEGF) induced C6 cell proliferation and migration, and SU1496, a selective inhibitor of VEGF receptor 2 (VEGFR2), blocked increased glioma cell growth, migration, and angiogenicity observed in AS-C6 cell cultures. The above results seem to be due to a direct interaction between HARP and VEGF in the culture medium of C6 and PC-C6 cells, while AS-C6 cells secreted comparable amounts of VEGF that do not interact with HARP. Collectively, these data suggest that HARP negatively affects diverse biological activities in C6 glioma cells, mainly due to binding of HARP to VEGF, which may sequester secreted VEGF from signalling through VEGFR2.

Heparin-binding protein pleiotrophin: an important player in the angiogenic process

Angiogenesis, the formation of new blood vessels from pre-existing ones, is a fundamental process in life, being also significantly important in several pathological situations. Pleiotrophin is a heparin-binding growth factor with pleiotrophic actions and significant role(s) in the formation of new blood vessels, being regulated by angiogenic stimuli and acting directly on endothelial cells. In this minireview, we summarize data on the regulation and mode of action of pleiotrophin and its involvement in physiological and tumor angiogenesis.

The chemokine receptor CXCR4 strongly promotes neuroblastoma primary tumour and metastatic growth, but not invasion

Neuroblastoma (NB) is a heterogeneous, and particularly malignant childhood neoplasm in its higher stages, with a propensity to form metastasis in selected organs, in particular liver and bone marrow, and for which there is still no efficient treatment available beyond surgery. Recent evidence indicates that the CXCR4/CXCL12 chemokine/receptor axis may be involved in promoting NB invasion and metastasis. In this study, we explored the potential role of CXCR4 in the malignant behaviour of NB, using a combination of in vitro functional analyses and in vivo growth and metastasis assessment in an orthotopic NB mouse model. We show here that CXCR4 overexpression in non-metastatic CXCR4-negative NB cells IGR-NB8 and in moderately metastatic, CXCR4 expressing NB cells IGR-N91, strongly increased tumour growth of primary tumours and liver metastases, without altering the frequency or the pattern of metastasis. Moreover shRNA-mediated knock-down experiments confirmed our observations by showing that silencing CXCR4 in NB cells impairs in vitro and almost abrogates in vivo growth. High levels of CXCL12 were detected in the mouse adrenal gland (the primary tumour site), and in the liver suggesting a paracrine effect of host-derived CXCL12 on NB growth. In conclusion, this study reveals a yet unreported NB-specific predominant growth and survival-promoting role of CXCR4, which warrants a critical reconsideration of the role of CXCR4 in the malignant behaviour of NB and other cancers.