Biomedical subjects

Ian F Pollack

Publications and source records attributed to Ian F Pollack.

47 records · Page 3Linked to original sources

PubMed2002

Glioma-associated hyaluronan induces apoptosis in dendritic cells via inducible nitric oxide synthase: implications for the use of dendritic cells for therapy of gliomas.

As a means of enhancing immunity to gliomas, we investigated local delivery of rat, bone marrow-derived dendritic cells (DCs) into rat 9L gliosarcoma tumors and into 9L tumors induced to undergo apoptosis by gamma knife radiosurgery. Contrary to other tumors, local delivery of DCs had no therapeutic effect on 9L gliomas, even when tumor apoptosis was induced via radiosurgery, which leads to efficient "loading" of the DCs with tumor antigen. To determine whether antigen-presenting cells, such as DCs, were viable in tumors, we carried out multiparametric staining of 9L tumors, using phycoerythrin-conjugated OX6 (MHC class II) or OX62 (DC specific) and FITC-labeled Val-Ala-Asp-fluoromethyl ketone (FITC-VAD-FMK; activated caspases). It was determined that DCs were undergoing apoptosis in these tumors. We therefore sought to determine which glioma cell surface receptors or components of the extracellular matrix in gliomas influenced DC viability. Hyaluronan (HA) is a major component of glioma extracellular matrix and has been found to support tumor cell migration and metastasis. However, its influence on the immune system, and particularly on DCs, via its receptor CD44 is not well documented. Using reverse transcription-PCR, Northern blot, and Western blot analyses, we determined that HA stimulated production of inducible nitric oxide synthase (iNOS) in DCs. NO production by HA-stimulated DCs was then verified biochemically. NO production was dependent on the size of HA; intermediate HA fragments had the greatest capacity to induce NO production in DC, whereas completely digested HA oligosaccharides failed to induce NO. Furthermore, N-monomethyl-L-arginine, an inhibitor of iNOS, completely blocked HA-induced NO production by DCs. Because induction of NO results in the induction of apoptosis in macrophages as well as other cells, DCs treated with HA were examined for apoptosis in terminal deoxynucleotidyl transferase (TdT)-mediated dUTP biotin nick-end labeling assays. It was demonstrated that HA induced apoptosis in DCs and that induction of apoptosis was dependent on the production of NO because it was entirely inhibited by N-monomethyl-L-arginine. Using flow cytometric analyses with FITC-VAD-FMK, which is specific for activated caspases, we also determined that induction of apoptosis in DCs with HA could be titrated. Coincubation of 9L tumor cells with DCs was found to induce apoptosis in DCs as indicated by fluorescent staining with FITC-VAD-FMK. Specificity of this reaction for CD44-HA interactions was determined by pretreatment of DCs with anti-CD44 or pretreatment of 9L tumor cells with hyaluronidase, which blocked the induction of apoptosis in DCs. These data indicate that HA expressed by gliomas may contribute to their immunosuppressive effects by promoting apoptosis among professional antigen-presenting cells such as DCs via iNOS induction after CD44-HA interactions.

Animals↗

PubMed2002

Expression of p53 and prognosis in children with malignant gliomas.

BACKGROUND: The prognosis of children with high-grade gliomas is uncertain, even when clinical and histologic findings are considered. We investigated whether mutations in the TP53 gene or the degree of expression of p53 protein in high-grade gliomas is associated with progression-free survival in children with these tumors. METHODS: Paraffin-embedded specimens of malignant gliomas from children treated in the Children's Cancer Group study CCG-945 were assessed by mutational analysis of TP53 (121 specimens) and immunohistochemical analysis of p53 (115 specimens). For mutational studies, areas of tissue that contained malignant glioma were isolated by microdissection, and the DNA was subjected to polymerase-chain-reaction-based amplification and sequencing of TP53 exons 5, 6, 7, and 8. Immunohistochemical analysis was performed with the use of a microwave-enhanced antigen retrieval and an antibody that bound both wild-type and mutant p53. RESULTS: We found a significant association between overexpression of p53 and outcome; this association was independent of histologic features, age, sex, the extent of resection, and tumor location. The rate ( +/- SE) of progression-free survival at five years was 44 +/- 6 percent in the group of 74 patients whose tumors had low levels of expression of p53 and 17 +/- 6 percent in the group of 41 patients whose tumors had overexpression of p53 (P<0.001). A nonsignificant association was observed between mutations in TP53 and outcome. CONCLUSIONS: Overexpression of p53 in malignant gliomas during childhood is strongly associated with an adverse outcome, independently of clinical prognostic factors and histologic findings.

Adolescent↗

PubMed2002

Risk assignment in childhood brain tumors: the emerging role of molecular and biologic classification.

Brain tumors as a group are the most common solid tumors of childhood and currently have the highest mortality rate. A major emphasis has historically been placed on stratifying therapy for these tumors based on histologic and clinical prognostic factors. However, with the increasing application of molecular approaches to refine the categorization of these tumors, it has become apparent that histologically comparable lesions may exhibit diverse patterns of gene expression and genomic alterations, which may correspond with important prognostic distinctions. This paper summarizes these observations and discusses how they are being applied in a preliminary fashion as a foundation for risk-adapted stratification of childhood brain tumor therapy.

Biomarkers, Tumor↗

PubMed2002

Molecular abnormalities and correlations with tumor response and outcome in glioma patients.

Molecular analysis approaches hold promise to refine the management of patients with malignant gliomas. An important step in the application of these techniques to guide clinical decision-making involves transitioning these approaches from the research setting into the clinical diagnostic arena, using methods that can be performed rapidly and reliably on surgically obtained tumor specimens. Many centers have begun this process for the detection of chromosome 1p and 19q deletions in oligodendroglial neoplasms. It is likely that the current limited portfolio of prognostic markers will be increased substantially during the next several years as innovative techniques for tumor genotyping and gene expression profiling help to identify additional correlates of tumor prognosis. An associated challenge involves demonstrating that biological stratification can support therapeutic stratification that will influence, rather than merely predict, the outcome of patients with brain tumors. The realization of this long-range goal will require the identification of novel therapeutic strategies that hold promise for improving the outcome of molecularly defined subsets of high-grade gliomas, which as a group remain largely resistant to conventional therapies.

Brain Neoplasms↗

PubMed2002

Impact of proliferation index on outcome in childhood malignant gliomas: results in a multi-institutional cohort.

OBJECTIVE: Prognoses of pediatric high-grade gliomas are unpredictable, even when clinical and histological factors are taken into account. In preliminary studies with an institutional cohort of pediatric high-grade gliomas, we observed a strong association between outcome and proliferation index, as assessed by immunolabeling with the MIB-1 antibody. To determine whether this marker could provide prognostically useful information independent of tumor histology, we examined the prognostic usefulness of this marker in the multi-institutional cohort of Children's Cancer Group Study 945, the largest group of childhood high-grade gliomas analyzed to date. METHODS: The study group consisted of tumors within this cohort that were classified as high-grade gliomas on central review according to contemporary World Health Organization guidelines and that had sufficient histopathological material to permit proliferation index assessment. Paraffin-embedded sections were cut and processed, microwave antigen enhancement was used, and MIB-1 indices were calculated by percent labeling in approximately 2000 cells (5-10 high-power fields) in the areas with greatest labeling. To ensure that the review diagnostic classification and proliferation labeling index were assigned independently for each tumor, these analyses were performed by two different neuropathologists at separate institutions, and each was blinded to the results of the other. RESULTS: Ninety-eight tumors met eligibility criteria for this study. Among these high-grade gliomas, there was a strong association between MIB-1 labeling and patient outcome: 5-year progression-free survival was 33 +/- 7% in 43 patients whose tumors had MIB-1 indices of less than 18%, 22 +/- 8% in the 27 patients whose tumors had indices between 18 and 36%, and 11 +/- 6% in the 28 patients whose tumors had indices greater than 36% (P = 0.003). As anticipated, a strong association was also observed between histology and MIB-1 labeling index in these cases. Mean labeling indices were 19.4 +/- 2.66 for tumors classified as anaplastic astrocytoma versus 32.1 +/- 3.08 for those classified as glioblastoma multiforme (P = 0.0024). Notwithstanding this correlation, a significant association was noted between labeling index and progression-free survival, even after the analysis had been stratified by histology (P = 0.001). Although histology had an independent association with outcome, the prognostic value of MIB-1 labeling transcended histological subgrouping and was apparent both in tumors classified as anaplastic astrocytoma (P = 0.02) and in those classified as glioblastoma multiforme (P = 0.046). Multivariate regression modeling confirmed the strong independent association between MIB-1 labeling index and outcome. As a group, tumors with labeling indices higher than 36% had an almost uniformly poor outcome, regardless of histology. CONCLUSION: MIB-1 labeling index and histological categorization are each prognostically relevant in childhood high-grade gliomas. MIB-1 labeling index can help to refine the accuracy of histologically based prognostic assessments.

Antigens, Nuclear↗

PubMed2002

7-Hydroxystaurosporine-induced apoptosis in 9L glioma cells provides an effective antigen source for dendritic cells and yields a potent vaccine strategy in an intracranial glioma model.

OBJECTIVE: On the basis of recent studies indicating that tumoral apoptotic bodies may provide a potent source of antigen for delivery to antigen-presenting cells, as well as observations that signal transduction modulation may constitute a promising approach for inducing glioma cell apoptosis, we explored the efficacy of vaccination with glioma apoptotic body-pulsed dendritic cells (DCs) for inhibiting tumor growth in the syngeneic 9L glioma/Fischer rat model. METHODS: For induction of apoptosis, 7-hydroxystaurosporine (UCN-01) (200-300 ng/ml), a selective protein kinase C inhibitor, was co-incubated with 9L cells in vitro for 72 or 96 hours. After this pretreatment period, glioma cells and DCs were mixed, and the interaction between DCs and apoptotic 9L tumor cells was assessed using two-color flow cytometry. In a series of experiments, the efficacy of vaccination strategies using DCs co-cultured with apoptotic 9L cells was then examined in animals harboring intracranial tumors. RESULTS: Pretreatment of 9L cells with UCN-01 resulted in approximately 50% of cells' being observed to undergo apoptosis as compared with less than 3% of controls. After subsequent co-culture, two-color flow cytometry demonstrated a time-dependent physical association of DCs with the apoptotic glioma cells. Survival in animals harboring intracranial tumors was significantly longer for the animals treated with a glioma apoptotic body-pulsed DC vaccine than in the animals that received apoptotic glioma cells and DCs alone or vehicle (i.e., the controls), especially those that underwent a sequential vaccination strategy (P < 0.0001). Long-term survival (>90 d) was demonstrated in 6 (75%) of 8 animals that underwent this vaccination approach versus 0 (0%) of 16 controls. In contrast, no survival benefit was observed in animals that received DCs that were co-cultured with vehicle-treated (non-apoptotic) 9L cells. Three of four long-term survivors that were rechallenged intracranially with tumor cells also survived over the long term. CONCLUSION: These studies suggest that induction of apoptosis in glioma cells by use of UCN-01 may promote the uptake of tumor antigens by DCs. This finding is important because apoptotic body-stimulated DCs may hold promise in promoting a host response against an established intracranial glioma, particularly if the parameters for apoptotic induction, duration of co-culture, and vaccination can be optimized.

Alkaloids↗

PubMed2002

Delayed intracranial migration of cervical sublaminar and interspinous wires and subsequent cerebellar abscess. Case report.

Delayed complications associated with sublaminar and interspinous wiring in the pediatric cervical spine are rare. The authors present a case of delayed complication in which a cervical fusion wire migrated into the cerebellum, causing subsequent cerebellar abscess 2 years after posterior cervical arthrodesis. A craniotomy was required to remove the wire and drain the abscess. Despite their history of safety and successful fusion, procedures involving sublaminar and interspinous wiring carry a risk of neurological injury secondary to wire migration. A thorough neuroimaging evaluation is required in patients who have undergone fusion and who have neurological complaints to detect late instrumentation-related sequelae.

Adolescent↗

PubMed2002

Identification of a novel HLA-A*0201-restricted, cytotoxic T lymphocyte epitope in a human glioma-associated antigen, interleukin 13 receptor alpha2 chain.

PURPOSE: Interleukin 13 receptor alpha2-chain (IL-13Ralpha2) has been reported to be abundantly and specifically overexpressed in glioblastoma multiforme. Here we report the identification of a CTL epitope derived from the IL-13Ralpha2. EXPERIMENTAL DESIGN: Mature dendritic cells (DCs) were pulsed with each of the synthetic peptides that were designed, based on a binding affinity-based prediction and a proteosomal cleavage site prediction system, and used to stimulate autologous CD8+ T cells from an HLA-A2+ healthy donor. After four to six cycles of restimulation, the immunoreactivity of the T cells was analyzed for specific IFN-gamma production and CTL reactivity. RESULTS: Of the five peptides tested, IL-13Ralpha(345-354) (WLPFGFILI) induced a CD8(+) T-cell line that specifically produced IFN-gamma in response to HLA-A2+ T2 cells pulsed with the relevant peptide and lysed these cells. Peptide titration assays demonstrated that half-maximal lysis of IL-13Ralpha(345-354) peptide-reactive CD8(+) T cells required peptide loading concentration of approximately 5 nM. Perhaps most importantly, this CD8(+) T-cell line also displayed lytic activity against the HLA-A2+ human glioma cell lines that express IL-13Ralpha2. CONCLUSIONS: This novel CTL epitope may therefore serve as an attractive component of peptide-based vaccines to treat glioma and as a surrogate marker of T-cell immune responses in patients before and after therapy.

Amino Acid Sequence↗

PubMed2002

Resolution of Chiari malformation after repair of a congenital thoracic meningocele: case report and literature review.

OBJECTIVE AND IMPORTANCE: Many theories have been proposed regarding potential causative factors for Chiari malformations. An unusual case is described in which regression of a congenital Chiari malformation was observed after repair of a thoracic meningocele without direct surgical intervention to decompress the craniocervical junction. This supports the importance of an in utero craniospinal pressure gradient as a potential cause for congenital, but reversible, cerebellar herniation. CLINICAL PRESENTATION: A newborn baby was observed to have a thoracic meningocele. Magnetic resonance imaging scan revealed a concomitant Chiari malformation. No neurological deficits were present at initial examination. INTERVENTION: The patient underwent surgical closure of the thoracic meningocele and untethering of the spinal cord at the site of the dural defect. A postoperative magnetic resonance imaging scan obtained 3 months after the operation revealed complete resolution of the cerebellar herniation. CONCLUSION: The resolution of the Chiari malformation in this child may have resulted from restoration of normal cerebrospinal fluid flow and elimination of the meningocele-related cerebrospinal fluid pressure gradient between the intracranial and intraspinal compartments.

Arnold-Chiari Malformation↗

PubMedDate not supplied

Autologous glioma cell vaccine admixed with interleukin-4 gene transfected fibroblasts in the treatment of recurrent glioblastoma: preliminary observations in a patient with a favorable response to therapy.

We designed a phase I clinical trial of vaccinations with autologous glioma cells expressing transgene-derived interleukin-4 (IL-4), and treated one patient with a right temporal lobe recurrent glioblastoma. This 62-year-old man underwent craniotomy and partial tumor removal, at which time autologous tumor cells were obtained for vaccine preparation. After confirming the patient's cellular immune function by skin test, two cycles of vaccination with irradiated autologous glioma cells admixed with gene transfected fibroblasts were given intradermally. The patient demonstrated no evidence of allergic encephalitis throughout this course. Immunohistochemistry with biopsy samples taken from the vaccine sites demonstrated that the infiltration level of CD4, CD8 and CD1a positive cells increased proportionally to the amount of IL-4 produced at the each site, suggesting that there was local immune response induced at the vaccine site. While it is premature to assess effectiveness of the vaccine, this initial patient's course suggested a transient response to the vaccine, and he survived 10 months after treatment.

Antibody Formation↗

PubMedDate not supplied

Expression of a soluble transforming growth factor-beta (TGFbeta) receptor reduces tumorigenicity by regulating natural killer (NK) cell activity against 9L gliosarcoma in vivo.

Immunotherapy of gliomas has been forwarded as an attractive alternative to standard therapeutic modalities. Numerous observations indicate some therapeutic efficacy with this approach, but it is not curative in most reports. It is well established that gliomas suppress immune reactivity via a number of mechanisms, including expression CD95 ligand (CD95L), which induces apoptosis of immune effector cells, and secretion of immunosuppressive factors such as transforming growth factor-beta (TGFbeta). It has been hypothesized that abrogation of production or function of TGFbeta would improve immune reactivity to gliomas. To investigate this in a fashion that is translatable into clinical practice, we utilized a retroviral vector encoding a truncated, soluble form of the Type II receptor for TGFbeta (TFGbeta sr) and expressed it in the rat 9L gliosarcoma line (9L-TGFbeta sr). We then determined whether expression of TGFbeta sr affected in vitro sensitivity of 9L to lysis by immune effector cells, whether expression of TGFbeta sr affected tumorigenesis of 9L in vivo, and whether TGFbeta sr affected expression of immunity to 9L. In these experiments, we determined that 9L-TGFbeta sr was more susceptible than sham transfected 9L (9L-neo) to lysis by natural killer (NK) cells. We also determined that subcutaneously implanted 9L-TGFbeta sr was less tumorigenic than 9L-neo in syngeneic rats. Similarly, survival was extended by approximately 40% in rats given intracranial 9L-TGFbeta sr compared to 9L-neo. Finally, we determined that elimination of CD161+ cells resulted in comparable growth of 9L-neo and 9L-TGFbeta sr in vivo, indicating that NK or NK-like cells were responsible for the anti-tumor effects in this model.

Animals↗