Differences between phosphotyrosine accumulation and Neu/ErbB-2 receptor expression in astrocytic proliferative processes. Implications for glial oncogenesis

Evolution of anti-HER2 therapies for cancer treatment

The development of HER2-directed monoclonal antibodies and tyrosine kinase inhibitors have provided benefits to cancer patients, as well as produced many insights into the biology of the ErbB receptor family. Current therapies based on ErbB family members have resulted in improved overall survival with associated improvements in quality of life for the cancer patients that respond to treatment. Compared to monotherapy using either two antibodies to block the HER2 receptor blockade or combinatorial approaches with HER2 antibodies and standard therapies has provided additional benefits. Despite the therapeutic success of existing HER2 therapies, personalising treatment and overcoming resistance to these therapies remains a significant challenge. The heterogeneous intra-tumoural HER2 expression and lack of fully predictive and prognostic biomarkers remain significant barriers to improving the use of HER2 antibodies. Imaging modalities using radiolabelled pertuzumab and trastuzumab allow quantitative assessment of intra-tumoural HER2 expression, HER2 antibody saturation and the success of different drug delivery systems to be assessed. Molecular imaging with HER2 antibodies has the potential to be a non-invasive, predictive and prognostic technique capable of influencing therapeutic decisions, predicting response and failure of treatments as well as providing insights into receptor recycling and signalling. Similarly, conjugating HER2 antibodies with novel toxic payloads or combining HER2 antibodies with cellular immunotherapy provide exciting new opportunities for the management of tumours overexpressing HER2. Future research will lead to higher therapeutic responses, lower toxicities and providing insight into the mechanisms of resistance to HER2-targeted treatments.

Immunoglobulin genes implicated in glioma risk

Both genetic and environmental factors are thought to be causal in gliomagenesis. Several genes have been implicated in glioma development, but the putative role of a major immunity-related gene complex member, immunoglobulin heavy chain γ (IGHG) has not been evaluated. Prior observations that IGHG-encoded γ marker (GM) allotypes exhibit differential sensitivity to an immunoevasion strategy of cytomegalovirus, a pathogen implicated as a promoter of gliomagenesis, has lead us to hypothesize that these determinants are risk factors for glioma. To test this hypothesis, we genotyped the IGHG locus comprising the GM alleles, specifically GM alleles 3 and 17, of 120 glioma patients and 133 controls via TaqMan® genotyping assay. To assess the associations between GM genotypes and the risk of glioma, we applied an unconditional multivariate logistic regression analysis adjusted for potential confounding variables. In comparison to subjects who were homozygous for the GM 17 allele, the GM 3 homozygotes were over twice as likely, and the GM 3/17 heterozygotes were over three times as likely, to develop glioma. Similar results were achieved when analyzed by combining the data corresponding to alleles GM 3 and GM 3/17 in a dominant model. The GM 3/17 genotype and the combination of GM 3 and GM 3/17 were found to be further associated with over 3 times increased risk for high-grade astrocytoma (grades III-IV). Allele frequency analyses also showed an increased risk for gliomas and high-grade astrocytoma in association with GM 3. Our findings support the premise that the GM 3 allele may present risk for the development of glioma, possibly by modulating immunity to cytomegalovirus.

Epidermal growth factor receptor inhibitor ameliorates excessive astrogliosis and improves the regeneration microenvironment and functional recovery in adult rats following spinal cord injury

BACKGROUND

Astrogliosis is a common phenomenon after spinal cord injury (SCI). Although this process exerts positive effects on axonal regeneration, excessive astrogliosis imparts negative effects on neuronal repair and recovery. Epidermal growth factor receptor (EGFR) pathway is critical to the regulation of reactive astrogliosis, and therefore is a potential target of therapeutics to better control the response. In this report, we aim to investigate whether blocking EGFR signaling using an EGFR tyrosine kinase specific inhibitor can attenuate reactive astrogliosis and promote functional recovery after a traumatic SCI.

METHOD

The astrocyte scratch injury model in vitro and the weight-drop SCI model in vivo were used as model systems. PD168393 was used to inhibit EGFR signaling activation. Astrocytic activation and phosphorylated EGFR (pEGFR) were observed after immunofluorescence staining and Western blot analysis. The rate of proliferation was determined by immunofluorescence detection of BrdU-incorporating cells located next to the wound. The levels of TNF-α, iNOS, COX-2 and IL-1β in the culture medium under different conditions were assayed by ELISA. Western blot was performed to semi-quantify the expression of EGFR/pEGFR, glial fibrillary acid protein (GFAP) and chondroitin sulfate proteoglycans (CSPGs). Myelin was stained by Luxol Fast Blue Staining. Cresyl violet eosin staining was performed to analyze the lesion cavity volume and neuronal survival following injury. Finally, functional scoring and residual urine recording were performed to show the rats' recovery.

RESULTS

EGFR phosphorylation was found to parallel astrocyte activation, and EGFR inhibitor PD168393 potently inhibited scratch-induced reactive astrogliosis and proinflammatory cytokine/mediator secretion of reactive astrocytes in vitro. Moreover, local administration of PD168393 in the injured area suppressed CSPGs production and glial scar formation, and resulted in reduced demyelination and neuronal loss, which correlated with remarkable hindlimb motor function and bladder improvement in SCI rats.

CONCLUSIONS

The specific EGFR inhibitor PD168393 can ameliorate excessive reactive astrogliosis and facilitate a more favorable environment for axonal regeneration after SCI. As such, EGFR inhibitor may be a promising therapeutic intervention in CNS injury.

C-erbB2/HER2 in human gliomas, medulloblastomas, and meningiomas: a minireview

C-erbB2/HER2 serves as an important prognostic and predictive biomarker in various human tumors, especially in breast cancer, whereas its role in human intracranial tumors is more uncertain. We therefore performed a search in PubMed to get an update. This literature review comprises immunohistochemical studies on the clinical significance of c-erbB2/HER2 overexpression in gliomas, medulloblastomas, and meningiomas. In general, the findings were discrepant with regard to correlations between overexpression, tumor grade, and prognosis. Use of various antibodies may be a contributing factor to these discrepancies. Standardization of the immunohistochemical procedures is a relevant topic for discussion.

c-erbB-2 protein expression in astrocytic tumors of the brain

Background

Astrocytic tumors are the primary brain tumors, which often progress to glioblastoma, a highly malignant neoplasm of the central nervous system. There is much new data regarding to the formation and progression of these tumors; however, glioblastoma remains one of the most fatal neoplasms in humans.

The aim of the study was to evaluate the role of c-erbB-2 protein expression in various groups of astrocytic tumors.

Material/Methods

65 cases of astrocytic tumors were divided into 3 groups: diffuse astrocytoma (group I; n=17 cases), anaplastic astrocytoma (group II; n=23 cases) and glioblastoma (group III; n=25 cases). C-erbB-2 protein expression was estimated semiquantitatively on immunohistochemically stained tissue sections using antibodies against c-erbB-2 protein. Statistical analysis was performed in all examined groups.

Results

The c-erbB-2 protein expression was observed in 15 out of 17 cases (88.3%) in group I, 22 out of 25 cases (88%) cases in group II, and in 19 out of 23 cases (82.6%) in group III. There were no statistically significant differences between the examined groups. The strongest c-erbB-2 immunoexpression was observed in low grade astrocytomas (diffuse astrocytomas G2); in the glioblastoma group the c-erbB-2 protein expression was weak and 17.4% of cases were negative.

Conclusions

C-erbB-2 protooncogene alteration is an early phenomenon in glial tumor development and progression.

Current and emerging molecular targets in glioma

Gliomas are the most common and lethal neurological cancers. Despite research efforts, the prognosis for patients with malignant gliomas remains poor. Advances in the understanding of cellular and molecular alterations in gliomas have led to the emergence of experimental molecularly targeted therapies. This article summarizes recent progress in the development of targeted therapies for glioma, focusing on emerging molecular targets, including neuropeptide and neurotrophin pathways, glutamate receptors, epigenetic mechanisms and glioma stem cell targets. Recent clinical trials of small molecules and antibodies targeted at growth factor pathways and intracellular signaling cascades are also discussed.

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.

ErbB receptor signaling in astrocytes: a mediator of neuron-glia communication in the mature central nervous system

Astrocytes are now recognized as active players in the developing and mature central nervous system. Each astrocyte contacts vascular structures and thousands of synapses within discrete territories. These cells receive a myriad of inputs and generate appropriate responses to regulate the function of brain microdomains. Emerging evidence has implicated receptors of the ErbB tyrosine kinase family in the integration and processing of neuronal inputs by astrocytes: ErbB receptors can be activated by a wide range of neuronal stimuli; they control critical steps of glutamate-glutamine metabolism; and they regulate the biosynthesis and release of various glial-derived neurotrophic factors, gliomediators and gliotransmitters. These key properties of astrocytic ErbB signaling in neuron-glia interactions have significance for the physiology of the mature central nervous system, as exemplified by the central control of reproduction within the hypothalamus, and are also likely to contribute to pathological situations, since both dysregulation of ErbB signaling and glial dysfunction occur in many neurological disorders.

Flow cytometry analysis of neural differentiation markers expression in human glioblastomas may predict their response to chemotherapy

Glioblastoma multiforme (GBM) represents an extremely chemoresistant tumour type. Here, authors analysed the immunophenotype of GBM tumours by flow cytometry and correlated the immunophenotypic characteristics with sensitivity to chemotherapy. The expression of selected neural and non-neural differentiation markers including A2B5, CD34, CD45, CD56, CD117, CD133, EGFR, GFAP, Her-2/neu, LIFR, nestin, NGFR, Pgp and vimentin was analysed by flow cytometry in eleven GBM (WHO gr.IV) patients. The sensitivity of tumour cells to a panel of chemotherapeutic agents was tested by the MTT assay. All tumours were positive for A2B5, CD56, nestin and vimentin. CD133, EGFR, LIFR, NGFR and Pgp were expressed only by minor tumour cell subpopulations. CD34, CD45, CD117, GFAP and Her-2/neu were constantly negative. Direct correlations were found between the immunophenotypic markers and chemosensitivity: A2B5 vs lomustine (r(2) = 0.642, P = 0.033), CD56 vs cisplatin (r(2) = 0.745, P = 0.013), %Pgp(+) vs vincristine (r(2) = 0.846, P = 0.008), and %NGFR(+) vs daunorubicine (r(2) = 0.672, P = 0.047) and topotecan (r(2) = 0.792, P = 0.011). In contrast, inverse correlations were observed between: EGFR vs paclitaxel (r(2) = -0.676, P = 0.046), CD133 vs dacarbazine (r(2) = -0.636, P = 0.048) and LIFR vs daunorubicine (r(2) = -0.878, P = 0.004). Finally, significant associations were also found among sensitivities to different chemotherapeutic agents and among different immunophenotypic markers. In conclusion, histopathologically identical GBM tumours displayed a marked immunophenotypic heterogeneity. The expression of A2B5, CD56, NGFR and Pgp appeared to be associated with chemoresistance whereas CD133, EGFR and LIFR expression was characteristic of chemosensitive tumours. We suggest that flow cytometric imunophenotypic analysis of GBM may predict chemoresponsiveness and help to identify patients who could potentially benefit from chemotherapy.

Low HER2-expressing glioblastomas are more often secondary to anaplastic transformation of low-grade glioma

BACKGROUND

Anti-Human Epithelial Receptor Type 2 (HER2) antibodies have the ability to induce in vitro apoptosis of glioblastoma (GBM) cells. This study was designed to evaluate the variability of HER2 expression in GBM and its role as a possible prognosis factor.

METHODS

Data of 57 patients with GBM and 16 patients with grade III gliomas were retrospectively analyzed. The expression of HER2 was determined by immunohistochemistry and intensity was noted from 0+ to 3+. We compared the HER2 expression in de novo GBM and in GBM resulting from anaplastic transformation of low-grade glioma ("secondary GBM"). Statistical analysis was performed using univariate analysis and the Kaplan-Meier method.

FINDINGS

All GBM expressing highly HER2 (2+ and 3+) were de novo GBM. All secondary GBM expressed HER2 with low intensity (0+ and 1+). Survival time was significantly longer when HER2 expression was low (Log Rank test P = 0.04). The patterns of HER2 expression were similar between grade III gliomas and secondary GBM.

CONCLUSIONS

To our best knowledge, our study showed for the first time a significant association between HER2 expression and the type of GBM, with subsequent influence on survival rate. GBM with low-HER2 expression are more likely to be secondary GBM, carrying a better prognosis than de novo GBM.

Modulation of glioma BK channels via erbB2

Glioma cells show up-regulation and constitutive activation of erbB2, and its expression correlates positively with increased malignancy. A similar correlation has been demonstrated for the expression of gBK, a calcium-sensitive, large-conductance K(+) channel. We show here that glioma BK channels are a downstream target of erbB2/neuregulin signaling. Tyrphostin AG825 was able to disrupt the constituitive erbB2 activation in a dose-dependent manner, causing a 30-mV positive shift in gBK channel activation in cell-attached patches. Conversely, maximal stimulation of erbB2 with a recombinant neuregulin (NRG-1beta) caused a 12-mV shift in the opposite direction. RT-PCR studies reveal no change in the BK splice variants expressed in treated glioma cells. Furthermore, isolation of surface proteins through biotinylation did not show a change in gBK channel expression, and probing with phospho-specific antibodies showed no alteration in channel phosphorylation. However, fura-II Ca(2+) fluorescence imaging revealed a 35% decrease in the free intracellular Ca(2+) concentration after erbB2 inhibition and an increase in NRG-1beta-treated cells, suggesting that the observed changes most likely were due to alterations in [Ca(2+)](i). Consistent with this conclusion, neither tyrphostin AG825 nor NRG-1beta was able to modulate gBK channels under inside-out or whole-cell recording conditions when intracellular Ca(2+) was fixed. Thus, gBK channels are a downstream target for the abundantly expressed neuregulin-1 receptor erbB2 in glioma cells. However, unlike the case in other systems, this modulation appears to occur via changes in [Ca(2+)](i) without changes in channel expression or phosphorylation. The enhanced sensitivity of gBK channels in glioma cells to small, physiological Ca(2+) changes appears to be a prerequisite for this modulation.

Determination of HER-2/neu overexpression and clinical predictors of survival in a cohort of 347 patients with primary malignant brain tumors

INTRODUCTION

HER-2/neu overexpression has been associated with poor prognosis in a variety of malignancies. The extent and relevance of HER-2/neu overexpression in human central nervous system (CNS) malignancies is unclear. We retrospectively analyzed a large cohort of patients with primary malignant brain tumors to evaluate the role of HER-2/neu overexpression, clinical characteristics at presentation, and other predisposing factors as predictors of survival.

MATERIALS AND METHODS

Records of 347 adult patients (193 males, 154 females) diagnosed and followed between 1986 and 2001 with a biopsy-proven diagnosis of a primary malignant brain tumor at a tertiary care oncology center were reviewed. Archival pathologic samples were analyzed for HER-2/neu overexpression using the Hercep immunohistochemical (IHC) assay (DAKO). A score of 2+ or greater on the assay was considered positive for HER-2/neu overexpression. Mortality and its predictors were evaluated using multiple logistic regression. (This study was approved and reviewed by the Institutional Review Board Committee [IRB] of University of North Dakota School of Medicine and Health Sciences.)

RESULTS

Among the 347 adult patients with a mean age of 53 years (range; 41-73 years), overall mean survival was 23 months (range; 0-151 months). It was found that 10.4% of the archival pathologic samples showed presence of HER-2/neu overexpression by IHC. The HER-2/neu overexpression predicted significantly increased mortality [p = 0.01, analysis of variance (ANOVA)]. Other clinical predictors associated with increased mortality included site of tumor (occipital and parietal lobes) (p = 0.02, ANOVA), tumor histology (glioblastoma) (p < 0.01, ANOVA), and presenting symptom (nausea/vomiting) (p < 0.01, ANOVA). Also, there was a higher incidence of associated primary malignancies (outside the CNS) in the HER-2/neu overexpression group (30% vs. 7%).

CONCLUSIONS

HER-2/neu overexpression seen in 10.4% appears to predict a slight increased mortality in patients with primary malignant brain tumors, especially glioblastoma multiforme, and is associated with a high incidence of a second primary malignancy outside the CNS. Additionally, our data suggests that other clinical variables were predictive of increased mortality, including tumor location (occipital), histology (glioblastoma), and presenting symptoms (nausea/vomiting). The large, heterogeneous sample employed in our study allows more definitive conclusions to be made with regard to the usefulness of HER-2/neu and other clinical predictors of survival in patients with primary brain tumors.

Recombinant humanised anti-HER2/neu antibody (Herceptin) induces cellular death of glioblastomas

Glioblastoma multiforme (GBM) remains the most devastating primary tumour in neuro-oncology. Targeting of the human epithelial receptor type 2 (HER2)-neu receptor by specific antibodies is a recent well-established therapy for breast tumours. Human epithelial receptor type 2/neu is a transmembrane tyrosine/kinase receptor that appears to be important for the regulation of cancer growth. Human epithelial receptor type 2/neu is not expressed in the adult central nervous system, but its expression increases with the degree of astrocytoma anaplasia. The specificity of HER2/neu for tumoral astrocytomas leads us to study in vitro treatment of GBM with anti-HER2/neu antibody. We used human GBM cell lines expressing HER2/neu (A172 express HER2/neu more than U251MG) or not (U87MG) and monoclonal humanised antibody against HER2/neu (Herceptin®). Human epithelial receptor type 2/neu expression was measured by immunohistochemistry and flow cytometry. Direct antibody effect, complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity were evaluated by different cytometric assays. We have shown, for the first time, the ability of anti-HER2/neu antibodies to induce apoptosis and cellular-dependent cytotoxicity of HER2/neu-expressing GBM cell lines. The results decreased from A172 to U251 and were negative for U87MG, in accordance with the decreasing density of HER2/neu receptors.

Role of Her-2/neu overexpression and clinical determinants of early mortality in glioblastoma multiforme

Her-2/neu or c-erbB-2, a 185-kD protein is an important prognostic indicator/target for therapy in metastatic breast carcinoma. Recent reports have also identified a role for Her-2/neu overexpression in other solid tumors. We performed a retrospective analysis to evaluate the prevalence and prognostic role of Her-2/neu overexpression in patients with glioblastoma multiforme (GBM). Data collection (chart review) included demographic information, symptoms at presentation, histologic grade, survival time, and treatment offered. Testing for Her-2/neu overexpression was performed on paraffin-embedded archival tumor tissue using immunohistochemistry (IHC) (Hercep test). An IHC score of 2+ or greater was considered overexpression. An experienced pathologist who was blinded from the clinical history performed all the IHC testing. Between 1990 and 2001, 149 subjects (68 females, 81 males) with a biopsy-proven diagnosis of GBM were identified. Age range was 26 to 79 years (mean: 64 years) and overall mean survival was 12 months. Her-2/neu overexpression was detected in 23 patients (15.4%). Interestingly, the median survival for patients whose pathologic specimens revealed Her-2/neu overexpression was 4 months compared to those who lacked overexpression, in whom survival was 8 months. After adjusting for age, performance status, smoking history, and treatment, logistic regression analysis (with a survival of <3 months as the dependent variable) revealed that Her-2/neu overexpression significantly (p < 0.01) increased the odds of early mortality (<3 months). The results of our large study indicate that Her-2/neu overexpression may be a poor prognostic marker in patients with GBM. In addition, in a proportion of subjects (15.4%), Her-2/neu may be a potential target for tumor-specific monoclonal antibody therapy. The role of trastuzumab (alone or in combination with conventional therapy) needs to be evaluated.

Autocrine heregulin generates growth factor independence and blocks apoptosis in colon cancer cells

The aim of this study was to determine whether constitutive ErbB2 activation controls growth and apoptosis in colon cancer cells. Growth arrested GEO cells showed constitutive activation of ErbB2 in the absence of exogenous growth factors or serum supplementation. Higher levels of heregulin and ErbB2 activation were observed in the growth-arrested state and cell cycle re-entry was independent of exogenous growth factors. Blockade of ErbB2 activation by heregulin neutralizing antibodies and by AG879 resulted in prevention of cell cycle re-entry. This indicated that autocrine heregulin activity was responsible for growth factor independence and for cell cycle re-entry. Activation of ErbB2 was the result of heregulin mediated interaction with ErbB3 and generated downstream activation of the ERK and the PI3K/AKT pathways. Heregulin neutralizing antibody treatment of growth arrested GEO cells also generated apoptosis as reflected by PARP cleavage and DNA fragmentation indicating a cell survival signal was also induced by the constitutively activated ErbB2. The activation of AKT but not the MAPK pathway was responsible for cell survival in these cells.

Regulation of neuregulin expression in the injured rat brain and cultured astrocytes

In this report, we investigated whether reactive astrocytes produce neuregulins (glial growth factor 2/heregulin/acetylcholine receptor-inducing activity or neu differentiation factor) and its putative receptors, ErbB2 and ErbB3 tyrosine kinases, in the injured CNS in vivo. Significant immunoreactivities with anti-neuregulin, anti-ErbB2, and anti-ErbB3 antibodies were detected on astrocytes at the injured site 4 d after injury to the adult rat cerebral cortex. To elucidate the mechanisms for the upregulation of neuregulin expression in astrocytes, primary cultured astrocytes were treated with certain reagents, including forskolin, that are known to elevate the intracellular level of cAMP and induce marked morphological changes in astrocytes. Western blot analysis showed that the expression of a 52 kDa membrane-spanning form of a neuregulin protein was enhanced in cultured astrocytes after administration of forskolin. The upregulation of glial fibrillary acidic protein was also observed in astrocytes treated with forskolin. In contrast, inactivation of protein kinase C because of chronic treatment with phorbol ester 12-O-tetradecanoyl phorbol 13-acetate downregulated the expression of the 52 kDa isoform, although other splice variants with apparent molecular sizes of 65 and 60 kDa were upregulated. These results suggest that the enhancement of neuregulin expression at injured sites is induced, at least in part, by elevation in intracellular cAMP levels and/or a protein kinase C signaling pathway. The neuregulin expressed on reactive astrocytes may stimulate their proliferation and support the survival of neurons surrounding cortical brain wounds in vivo.

What role(s) for TGFalpha in the central nervous system?

Transforming growth factor alpha (TGFalpha) is a member of the epidermal growth factor (EGF) family with which it shares the same receptor, the EGF receptor (EGFR or erbB1). Identified since 1985 in the central nervous system (CNS), its functions in this organ have started to be determined during the past decade although numerous questions remain unanswered. TGFalpha is widely distributed in the nervous system, both glial and neuronal cells contributing to its synthesis. Although astrocytes appear as its main targets, mediating in part TGFalpha effects on different neuronal populations, results from different studies have raised the possibility for a direct action of this growth factor on neurons. A large array of experimental data have thus pointed to TGFalpha as a multifunctional factor in the CNS. This review is an attempt to present, in a comprehensive manner, the very diverse works performed in vitro and in vivo which have provided evidences for (i) an intervention of TGFalpha in the control of developmental events such as neural progenitors proliferation/cell fate choice, neuronal survival/differentiation, and neuronal control of female puberty onset, (ii) its role as a potent regulator of astroglial metabolism including astrocytic reactivity, (iii) its neuroprotective potential, and (iv) its participation to neuropathological processes as exemplified by astroglial neoplasia. In addition, informations regarding the complex modes of TGFalpha action at the molecular level are provided, and its place within the large EGF family is precised with regard to the potential interactions and substitutions which may take place between TGFalpha and its kindred.

Targeted drug delivery for brain cancer treatment

The blood brain barrier (BBB) and the systemic toxicity of conventional chemotherapy present obstacles to the success of future blood-borne drug therapies of brain tumors. The work with polymer-encapsulated cancer drugs suggests an alternative and more focused treatment approach. Our experimental strategy integrates direct intracerebral drug delivery, sustained drug release from liposomes or polymer implants, and increased targeting of the drug either by chemically modifying the drug or by using tumor-specific carriers. This review will present some of the recent work on targeted drug delivery for brain cancer treatment.

Evidence for the differential expression of a variant EGF receptor protein in human prostate cancer

Earlier studies have demonstrated an unexplained depletion of the epidermal growth factor receptor (EGFR) protein expression in prostatic cancer. We now attribute this phenomenon to the presence of a variant EGFR (EGFRvIII) that is highly expressed in malignant prostatic neoplasms. In a retrospective study, normal, benign hyperplastic and malignant prostatic tissues were examined at the mRNA and protein levels for the presence of this mutant receptor. The results demonstrated that whilst EGFRvIII was not present in normal prostatic glands, the level of expression of this variant protein increased progressively with the gradual transformation of the tissues to the malignant phenotype. The selective association of high EGFRvIII levels with the cancer phenotype underlines the role that this mutant receptor may maintain in the initiation and progression of malignant prostatic growth, and opens the way for new approaches in the management of this disease including gene therapy.

Bone marrow-derived dendritic cells pulsed with a tumor-specific peptide elicit effective anti-tumor immunity against intracranial neoplasms

Although the central nervous system (CNS) is often regarded as an immunologically privileged site, it is well established that specific CNS immunoreactivity can be generated through peripheral vaccination with CNS antigens. Dendritic cells (DC) are potent antigen presenting cells of hematopoietic origin that have emerged as a promising tool for cancer immunotherapy capable of evoking significant anti-tumor immunity when pulsed with tumor-associated peptides. To explore a role for DC-based immunization strategies for the treatment of CNS tumors, we developed a brain tumor model using the C3 sarcoma cell line which expresses the tumor-specific, major histocompatibility complex (MHC) class I-restricted peptide epitope E7(49-57). Syngeneic C57Bl/6 mice receiving intravenous (i.v.) injections of bone marrow-derived DCs pulsed with E7 peptide were effectively protected against a subsequent intracerebral challenge with C3 tumor cells. More importantly, this systemic immunization strategy was effective in a therapy model as 67% of animals (10 of 15) with established (day 7) intracerebral C3 tumors treated with 3 weekly injections of E7 peptide-pulsed DCs achieved a long-term survival (>90 days) while no control animals survived beyond day 41. In vivo depletion of CD8+ cells, but not CD4+ or asialo-GM1+ cells, abrogated the efficacy of E7 peptide-pulsed DC therapy of established tumors, indicating a pivotal role of specific CD8+ T-cell responses in mediating the anti-tumor effect. Our findings support the hypothesis that effective CNS anti-tumor immunoreactivity can be generated with DC-based tumor vaccines.