Human-specific c-neu proto-oncogene protein overexpression in human malignant astrocytomas before and after xenografting

ROS receptor tyrosine kinase: a new potential target for anticancer drugs

ROS kinase is one of the last two remaining orphan receptor tyrosine kinases with an as yet unidentified ligand. The normal functions of human ROS kinase in different body tissues have not been fully identified so far. However, the ectopic expression, as well as the production of variable mutant forms of ROS kinase has been reported in a number of cancers, such as glioblastoma multiforme, and non-small cell lung cancer, suggesting a role for ROS kinase in deriving such tumors. It is thought also that c-ROS gene may have a role in some cardiovascular diseases, and the fact that homozygous male mice targeted against c-ROS gene are healthy but infertile, has inspired researchers to think about ROS inhibition as a method for development of new male contraceptives. The recent discovery of new selective and potent inhibitors for ROS kinase, along with the development of new specific diagnostic methods for the detection of ROS fusion proteins, raises the importance of using these selective inhibitors for targeting ROS mutations as a new method for treatment of cancers harboring such genes. This review focuses on the ectopic expression of ROS and its fusion proteins in different cancer types and highlights the importance of targeting these proteins for treatment of substantial cancers. It describes also the recent advances in the field of ROS kinase inhibition, and the potential clinical applications of ROS kinase inhibitors.

Differential distribution of erbB receptors in human glioblastoma multiforme: expression of erbB3 in CD133-positive putative cancer stem cells

Glioblastomas are the most common primary central nervous system tumors in adults, and they remain resistant to current treatments. erbB1 signaling is frequently altered in glioblastomas, suggesting thaterbB receptor family members may represent targets for molecular therapy. We performed a comprehensive analysis of erbB receptor and ligand expression profiles in a panel of 9 glioblastomas andcompared them to nonneoplastic cerebral tissue containing neocortex and adjacent white matter. Quantitative reverse transcription-polymerase chain reaction and Western blot analysis showed that erbB1signaling and erbB2 receptors exhibited highly variable deregulation profiles in the tumors, with patterns ranging from underexpression to overexpression; in contrast, erbB3 and erbB4 were downregulated. We next performed immunohistochemistry to determinethe distribution patterns of erbB receptors among the main neuralcell types in the tumors with special reference to the putative tumor stem cell population. Results revealed intertumoral and intratumoral heterogeneity in all 4 erbB expression profiles, but each receptor exhibited a distinct distribution pattern among glial fibrillary acidic protein-, Olig2-, NeuN-, and CD133-positive populations. Although erbB1 immunoreactivity was detected in only small subsets of CD133-positive putative tumor stem cells, erbB3 immunoreactivity was prominent in this population, suggesting that erbB3 may represent a new potential therapeutic target.

c-erbB-2 as a target for immunotherapy

The c-erbB-2 proto-oncogene encodes a 185 kDa transmembrane Type 1 tyrosine kinase receptor whose amplification and/or overexpression has been linked with poor prognosis in a variety of cancers. The oncoprotein has been suggested to play a key role in tumour cell invasion, motility and metastasis, and in responsiveness to therapeutic agents. Over-expression of c-erbB-2 therefore identifies an important subset of patients with a high probability of relapse, but low probability of response to certain conventional therapies. The cell surface location of the oncoprotein, its stability of expression and low levels in normal adult tissues render it an attractive target for immunotherapeutic intervention. Although a 'self' antigen, there is evidence that c-erbB-2 p185 can induce both humoral and cell-mediated immune responses in cancer patients. Approaches to exploit p185 as an immunotherapeutic target include vaccination with peptides, plasmid DNA or vectors (viruses/bacteria) carrying the gene; with cytokines, co-stimulatory factors and superantigens being evaluated as adjuvants. Many monoclonal antibody (mAb)-based strategies are also in clinical development. Monoclonal antibodies can serve multiple functions; direct inhibition of c-erbB-2 activity, recruitment of host effector mechanisms and direct or indirect delivery of toxic payloads. Clinical trials in patients with late stage disease have shown that many of these approaches are safe, feasible and relatively non-toxic, and, in some cases, objective responses have been seen. As with all immunotherapy, the greatest benefit is likely to be obtained in patients with minimal residual disease in an adjuvant setting; such studies are awaited with interest.

The Raf signal transduction cascade as a target for chemotherapeutic intervention in growth factor-responsive tumors

This review focuses on the Ras-Raf-mitogen-activated protein kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) signal transduction pathway and the consequences of its unregulation in the development of cancer. The roles of some of the cell membrane receptors involved in the activation of this pathway, the G-protein Ras, the Raf, MEK and ERK kinases, the phosphatases that regulate these kinases, as well as the downstream transcription factors that become activated, are discussed. The roles of the Ras-Raf-MEK-ERK pathway in the regulation of apoptosis and cell cycle progression are also analyzed. In addition, potential targets for pharmacological intervention in growth factor-responsive cells are evaluated.

c-erbB-2 and episialin challenge host immune response by HLA class I expression in human non-small-cell lung cancer

The role of major histocompatibility complex expression in cancer prognosis and pathogenesis is contradictory. The aim of the current study was to compare the expression of HLA class I molecules and of oncoproteins that may be sources of peptides presented by HLA class I antigens in non-small-cell lung cancer. For this purpose, the expression of HLA class I antigen and TAP-1 molecule (a transporter in the antigen-processing 1 transport protein) were studied with epidermal growth factor, receptor; c-erbB-2; episialin; wild-type and mutant p53; bcl-2 oncoprotein expression; and angiogenic factor expression (vascular endothelial growth factor and thymidine phosphorylase). The degree of lymphocytic stromal infiltration and of platelet-endothelial cell adhesion molecule-expressing lymphocytes was also studied. A strong association of c-erbB-2 and MUC1 (episialin) expression with HLA class I expression was observed (p = 0.005 and 0.009, respectively). Intense CD31-positive lymphocytic infiltration was also more frequent in HLA class I-positive cases (p = 0.05). Although there was no association of HLA class I expression with survival, loss of the HLA class I expression in MUC1 or c-erbB-2 overexpressing cases conferred a poorer clinical outcome (p = 0.04). Both c-erbB-2 and MUC1 are well-known targets of T-cell-mediated cytotoxicity and cell-cell or cell-matrix adhesion-regulating proteins. The authors provide evidence that the sequence of cell adhesion-disrupting oncoprotein expression, HLA class I induction, and enhanced epitope presentation followed by lymphocytic response is an important pathogenetic three-step sequence of events that define, in part, the clinical outcome in non-small-cell lung cancer.

Correlation of TGF-alpha and EGF-receptor expression with proliferative activity in human astrocytic gliomas

Fifty-nine paraffin-embedded astrocytic gliomas (four WHO grade 1, 21 WHO grade 2, 17 WHO grade 3 and 17 glioblastomas, WHO grade 4) were immunohistochemically investigated for expression of transforming growth factor-alpha (TGF-alpha), epidermal growth factor receptor (EGF-R) and oncoprotein c-erbB-2 by semiquantitative assessment. Proliferative activity was simultaneously analyzed by using the antibody Ki-67 (MIB-1). Immunostaining in neoplastic cells was quantified by image analysis. Concerning the antibodies used, the percentage of immunoreactive cells increased with histologic malignancy. There was no expression of EGF-R and c-erbB-2 in the majority of low-grade astrocytomas. However, small focal expressions of TGF-alpha and EGF-R were observed in several low-grade astrocytomas (11/25), suggesting an early stimulation of malignant transformation. With regard to percentage, a strong positive correlation between TGF-alpha and EGF-R-stained cells was found, indicating an autocrine stimulation of the mitogenic pathway of the TGF-alpha/EGF-R system. Likewise, indices of EGF-R and c-erbB-2 positive cells correlated significantly. Less significant correlations were also seen between EGF-R, c-erbB-2 frequencies and the Ki-67 labeling index. However, there was no correlation between TGF-alpha and Ki-67 indices. The results suggest that TGF-alpha expression is not directly related to the proliferative potential as judged by the Ki-67 labeling index. Furthermore, besides EGF-R and c-erbB-2, other growth factors and their receptors or mutant EGF-R might participate in the proliferative activity of gliomas.

Implantation of cultured human leptomeningeal cells into rat brain

Since previous studies have shown that cells cultured from human leptomeninges can express neuronal and glial antigens under appropriate culture conditions [DeGiorgio L. A. et al. (1994) J. Neurol. Sci. 124, 141 148; Bernstein J. J. et al. (1996) Int. J. Derl Neurosci. 14(5), 681 687], we have studied the developmental characteristics of these cells further by grafting them into young adult rat brains. Cells were labeled in culture with Fast Blue and were identified unequivocally by hybridization with nick-translated human DNA. Intensely Fast Blue positive human leptomeningeal cells were concentrated in the implant pocket and adjacent rat leptomeninges al one and two weeks postimplant. Human and rat leptomeningeal cells were similar morphologically and were equally immunopositive for vimentin and fibronectin. Implanted human cells did not express the neuronal and glial proteins they had in vitro. Cells which hybridized with human DNA corresponded to the intensely Fast Blue positive cells. Small groups of human DNA hybridizing cells were also observed in the choroid plexus. Less intensely Fast Blue positive neurons and glia were found in the brain but these hybridized with rat DNA. A minority of human leptomeningeal cells implanted into rat brain are subsequently found in host leptomeninges where they demonstrate properties characteristic of leptomeningeal fibroblasts. Small numbers of implanted cells can survive for two weeks.

c-erbB-2 in astrocytomas: infrequent overexpression by immunohistochemistry and absence of gene amplification by fluorescence in situ hybridization

Recent studies suggest that aberrations of c-erbB-2 may be involved in astrocytic brain tumours. We screened immunohistochemically c-erbB2 protein (p185) expression in 94 astrocytic grade 1-4 neoplasms of the brain. The amplification of the c-erbB-2 oncogene was investigated in protein overexpression cases by dual colour fluorescence in situ hybridisation (FISH). p185 overexpression was correlated with p53 and epidermal growth factor receptor (EGFR) expression, as well as with clinicopathological features. Only two anaplastic (grade 3) astrocytomas and one glioblastoma (grade 4) showed overexpression of p185 protein by immunohistochemistry (monoclonal MAb1 antibody TA250), whereas none of the grade 1-2 astrocytomas was positive. Interestingly, the expression of p185 was confined solely to the cytoplasm of neoplastic astrocytic cells and not to the cell membranes as found in malignancies with amplification of the c-erbB-2 oncogene. Two of the three overexpression cases were also positive by EGFR. No amplification of the c-erbB-2 gene was observed by FISH in the three tumours with immunohistochemical p185 overexpression or seven weakly positive/negative tumours. In conclusion, our results suggest that p185 overexpression is infrequent in astrocytomas, that it is of no important diagnostic or prognostic value and that c-erbB-2 oncogene amplification is not seen in the few cases in which there is overexpression.

Chromosome breakpoint at 17q11.2 and insertion of DNA from three different chromosomes in a glioblastoma with exceptional glial fibrillary acidic protein expression

A glioblastoma that retained glial fibrillary acidic protein (GFAP) in culture has a break in the long arm of chromosome 17 at band 17q11.2. DNA inserted at this breakpoint came from chromosome bands 3p21, 3q23, 16q11.2, and 22q11.2. These chromosome fragments were inserted in band 17q11.2 proximal to the neurofibromatosis-1 (NF-1) gene and neu (HER2; erbB2) oncogene loci. The glioblastoma also contained a reciprocal translocation between 16p12 and 20p12. These structural abnormalities, previously undescribed in gliomas, were demonstrated by high-resolution chromosome banding, microdissection, and fluorescence in situ hybridization (FISH). Numerical changes typical of glioblastoma were present: gain of chromosome 7 and losses of chromosomes 10, 13, and 22. The complex chromosome origin of DNA inserted in this glioma chromosome is described. The association of two infrequent events in this single glioblastoma line, this complex insertion and retention of GFAP expression, is not likely to be a chance occurrence. It raises the possibility of an association between the two events.

Expression of the ROS1 oncogene for tyrosine receptor kinase in adult human meningiomas

Oncogenes have been implicated in the promotion and progression of cancer in humans. Expression of the ROS1 oncogene, a member of the receptor tyrosine kinase superfamily, was examined in human meningiomas by coupled reverse transcription and polymerase chain reaction (RT-PCR) assays. Two sets of region-specific oligonucleotides, specific for different regions of the ROS1 messenger ribonucleic acid (mRNA), were used in RT-PCR assays to independently examine ROS1 transcripts from primary human meningiomas. ROS1 was expressed at high levels in approximately 55% (17 of 31) of the meningiomas examined, but not expressed in non-neoplastic brain samples. The commonplace expression of the ROS1 oncogene in meningiomas suggests a role for this oncogene in the etiology of these tumors.

Glioblastoma cells do not intravasate into blood vessels

Glioblastoma is very rarely found outside the central nervous system. The ability of rat C6 glioblastoma cells to intravasate into central nervous system and pial blood vessels is tested using a rat homografting model and two in vitro models. In vivo, scanning electron microscopy demonstrates that upon grafting C6 cells into implantation pockets in rat cortex, blood vessels can be spared in large digestion cysts formed in host brain parenchyma. Immunocytochemistry of the grafted rat cortex reveals that the glioblastoma cells are upon the blood vessel basement membrane, surrounded by the extracellular matrix material, fibronectin. The endothelial cells of the blood vessel are inside the laminin and fibronectin, and there were areas of endothelial cell hyperplasia. C6 cells are not observed inside blood vessels. In vitro, C6 cell cultures seeded with blood vessels from fresh rat pia exhibit the same relationship of the C6 glioblastoma cells to the blood vessel as those in the other models. The C6 cells migrate upon the pial blood vessel basement membrane but do not intravasate into the blood vessel. To ascertain whether structure and components of the blood vessel basement membrane are important factors in glioblastoma cell exclusion from blood vessels, C6 cells are seeded upon artificial basement membrane hydrated gel wafers. C6 cells migrate into the artificial basement membrane gel wafer by 1 day after seeding. These data indicate that glioblastoma cells are confined to the central nervous system by an inability to pass through vital basement membrane.

Analysis of c-erbB2 protein content of human glioma cells and tumor tissue

This study was designed to determine whether or not overexpression of the c-erbB2 protein plays a role in the etiology of human gliomas. The c-erbB2 gene codes for a 185 kDa cell membrane glycoprotein (gp185c-erbB2), which is similar to the receptor for epidermal growth factor. In initial studies, four human glioma cell lines (A-172, U118MG, U138MG and SW608) were used to develop techniques for detecting and quantifying gp185c-erbB2, using immunofluorescence microscopy, immunoblot analysis and flow cytometry. A-172 cells were found to have the highest content of gp185c-erbB2. More detailed studies utilizing A-172 cells indicated that cellular gp185c-erbB2 content changed little in response to conditions affecting cellular proliferative status, including serum deprivation, growth in low glucose medium and treatment with dimethyl sulfoxide. Ten human glioma specimens were then analyzed for cellular gp185c-erbB2 fluorescence and DNA content, using A-172 cells as a biological standard. Results indicated that gp185c-erbB2 was expressed at levels comparable to that of A-172 cells in many specimens, and at a very high level in one specimen. These data reiterate the problem of the molecular heterogeneity of human gliomas and indicate that gp185c-erbB2 may have a role in at least a subset of malignant glial tumors.

A 50 kDa protein present in conditioned medium of COLO-16 cells stimulates cell spreading and motility, and activates tyrosine phosphorylation of Neu/HER-2, in human SK-BR-3 mammary cancer cells

A factor present in conditioned medium of COLO-16 human cancer cells causes fast spreading, fast plasma membrane ruffling, cell shape change, net translocation, stimulation of chemotaxis and growth arrest in human SK-BR-3 mammary cancer cells. Based on the spreading effect, the factor was purified to homogeneity and migrated as a 50 kDa protein in SDS-polyacrylamide gel electrophoresis. Addition of the purified 50 kDa factor to the target cells in culture results in tyrosine phosphorylation of the p185erbB2 receptor concomitant with a fast redistribution and clustering of the receptor. The 50 kDa factor is also specifically retained by affinity chromatography on the immobilized extracellular domain of p185erbB2. Antibodies directed against this domain also inhibit the induction of motility. These data suggest that the 50 kDa factor is a putative ligand of p185erbB2 in SK-BR-3 cells. Biochemical and immunological evidence further indicate that this factor differs from p185erbB2 ligands described so far. Its activity could play a role in the pathogenesis of breast cancer.

Amplification and differential expression of members of the erbB-gene family in human glioblastoma

The objective of the present study was to determine the frequency of amplifications of three different members of the erbB gene family in human glioblastoma multiforme (GBM). We investigated 47 glial tumors (37 GBM WHO grade IV, 5 anaplastic astrocytomas WHO III and 5 astrocytomas WHO II) by Southern and Western analysis, and immunocytochemistry. Gene amplification of erbB genes in human malignant gliomas was restricted to the EGF receptor (EGFR) gene, erbB-1. We found amplification of the EGFR gene in 49% (18/37) of GBM but not in the astrocytomas WHO II/III. The erbB-2 and erbB-3 genes showed no amplification in the tumor specimens investigated in this study. At the protein level we found overexpression of the EGF receptor in 86% (32/37) by Western analysis and in 92% (34/37) by immunocytochemistry. Expression of the ERBB2 protein was present in 54% (20/37) but immunoreactivity was much weaker than for EGF receptor and in most cases barely detectable by Western analysis and immunocytochemistry. The ERBB3 protein was not expressed in the glial tumors investigated in this study. Of the three erbB genes only gene amplification and overexpression of the EGF receptor seems to have an impact on tumor progression of human gliomas. Our data from immunohistochemistry indicate that ERBB2 expression in GBM is closely correlated with EGF receptor levels and is therefore not useful as an independent prognostic parameter.

Migration of human malignant astrocytoma cells in the mammalian brain: Scherer revisited

Fresh suspensions of human glioblastoma multiforme were preincubated in the plant lectin Phaseolus vulgaris leucoagglutinin (PHAL) and implanted into cortical pockets in adult rat brain. Brains were investigated periodically over 30 postoperative days and the migration of the human glioblastoma cells was traced with anti-PHAL immunofluorescence or the overexpression of human specific p185c-neu a specific marker of a class of human malignant astrocytoma cells. The principal pathway of migration of the implanted human cells in the rat brain was ventrally through cortical gray matter and into the corpus callosum, with rapid lateral distribution in this and other parallel and intersecting white matter fascicles. Human glioblastoma cells also migrated on basement membrane lined blood vessels, pia-glia membrane and spaces of Virchow-Robin, as well as the subependymal space of the ventricles. These paths of migration of human glioblastoma cells in the rat brain are consistent with the pathways of spread of glioblastoma in the human brain as described by Scherer over 50 years ago, indicating that multifocal malignant astrocytomas have common migratory pathways in mature mammalian brain.

Migration of fresh human malignant astrocytoma cells into hydrated gel wafers in vitro

Individual astrocytoma cells expressing a cytoplasmic form of p185c-neu migrated along basement membrane lined surfaces after xenografing fresh low or high grade human malignant astrocytomas into host rat brain. We now study the migratory capacity of fresh human malignant astrocytoma cells seeded on hydrated gel wafers composed of artificial basement membrane or collagen I, a normal and lesion-related CNS extracellular matrix component. Approximately 10(7) mechanically disrupted cells (with small clumps) of 3 fresh low grade and 6 fresh high grade astrocytomas were seeded on the surface of artificial basement membrane and collagen I wafers (11 x 16 mm). The wafers were then prepared for scanning electron microscopy and immunohistochemistry at 1, 3, 5, and 7 days after seeding. Regardless of tumor grade, a morphologically similar class of cells was observed to migrate through collagen I gels in 24 hours and 0.5-1.5 mm into artificial basement membrane gels in 7 days. Immunohistochemistry revealed that the migrated cells from low and high grade astrocytomas were positive for glial fibrillary acidic protein (GFAP)) and expressed cytoplasmic human-specific p185c-neu. These data indicate that fresh human malignant astrocytoma cells that contain GFAP and express cytoplasmic p185c-neu have a high degree of migratory capacity and could be the cell in the tumor involved in intraparenchymal metastasis and poor patient survival in high grade astrocytomas of the human brain.