Characterization of a new human glioblastoma cell line that expresses mutant p53 and lacks activation of the PDGF pathway

dp53 Restrains ectopic neural stem cell formation in the Drosophila brain in a non-apoptotic mechanism involving Archipelago and cyclin E

Accumulating evidence suggests that tumor-initiating stem cells or cancer stem cells (CSCs) possibly originating from normal stem cells may be the root cause of certain malignancies. How stem cell homeostasis is impaired in tumor tissues is not well understood, although certain tumor suppressors have been implicated. In this study, we use the Drosophila neural stem cells (NSCs) called neuroblasts as a model to study this process. Loss-of-function of Numb, a key cell fate determinant with well-conserved mammalian counterparts, leads to the formation of ectopic neuroblasts and a tumor phenotype in the larval brain. Overexpression of the Drosophila tumor suppressor p53 (dp53) was able to suppress ectopic neuroblast formation caused by numb loss-of-function. This occurred in a non-apoptotic manner and was independent of Dacapo, the fly counterpart of the well-characterized mammalian p53 target p21 involved in cellular senescence. The observation that dp53 affected Edu incorporation into neuroblasts led us to test the hypothesis that dp53 acts through regulation of factors involved in cell cycle progression. Our results show that the inhibitory effect of dp53 on ectopic neuroblast formation was mediated largely through its regulation of Cyclin E (Cyc E). Overexpression of Cyc E was able to abrogate dp53's ability to rescue numb loss-of-function phenotypes. Increasing Cyc E levels by attenuating Archipelago (Ago), a recently identified transcriptional target of dp53 and a negative regulator of Cyc E, had similar effects. Conversely, reducing Cyc E activity by overexpressing Ago blocked ectopic neuroblast formation in numb mutant. Our results reveal an intimate connection between cell cycle progression and NSC self-renewal vs. differentiation control, and indicate that p53-mediated regulation of ectopic NSC self-renewal through the Ago/Cyc E axis becomes particularly important when NSC homeostasis is perturbed as in numb loss-of-function condition. This has important clinical implications.

Antigenic profiling of glioma cells to generate allogeneic vaccines or dendritic cell-based therapeutics

PURPOSE

Allogeneic glioma cell lines that are partially matched to the patient at class I human leukocyte antigen (HLA) loci and that display tumor-associated antigens (TAA) or antigenic precursors [tumor antigen precursor proteins (TAPP)] could be used for generating whole tumor cell vaccines or, alternatively, for extraction of TAA peptides to make autologous dendritic cell vaccines.

EXPERIMENTAL DESIGN

Twenty human glioma cell lines were characterized by molecular phenotyping and by flow cytometry for HLA class I antigen expression. Twelve of the 20 cell lines, as well as analyses of freshly resected glioma tissues, were further characterized for protein and/or mRNA expression of 16 tumor antigen precursor proteins or TAA.

RESULTS

These 20 human glioma cell lines potentially cover 77%, 85%, and 78% of the U.S. Caucasian population at HLA-A, HLA-B, and HLA-C alleles, respectively. All cells exhibited multiple TAA expressions. Most glioma cells expressed antigen isolated from immunoselected melanoma-2 (Aim-2), B-cyclin, EphA2, GP100, beta1,6-N-acetylglucosaminyltransferase V (GnT-V), IL13Ralpha2, Her2/neu, hTert, Mage, Mart-1, Sart-1, and survivin. Real-time PCR technology showed that glioblastoma specimens expressed most of the TAA as well. Tumor-infiltrating lymphocytes and CD8(+) CTL killed T2 cells when loaded with specific HLA-A2(+) restricted TAA, or gliomas that were both HLA-A2(+) and also positive for specific TAA (Mart-1, GP100, Her2/neu, and tyrosinase) but not those cells negative for HLA-A2 and/or lacking the specific epitope.

CONCLUSIONS

These data provide proof-in-principle for the use of allogeneic, partially HLA patient-matched glioma cells for vaccine generation or for peptide pulsing with allogeneic glioma cell extracts of autologous patient dendritic cells to induce endogenous CTL in brain tumor patients.

Isolation of immunoresistant human glioma cell clones after selection with alloreactive cytotoxic T lymphocytes: cytogenetic and molecular cytogenetic characterization

Intratumoral heterogeneity and genetic instability within gliomas may allow intrinsically immunoresistant (IR) cells to escape alloreactive cytotoxic T lymphocyte (aCTL) cellular immunotherapy. The potential existence of aCTL-resistant variants prompted us to investigate whether cellular immunotherapy resistant glioma models could be isolated. To generate the models, repeated intermittent or continuous selective pressure (ISP or CSP) with multiple aCTL populations was applied to a low-passage glioblastoma cell explant, 13-06-MG, obtained from a patient at initial diagnosis. IL-6 and IL-8 secretion was greater in coincubates of aCTL cells with 13-06-ISP and 13-06-CSP immunoselected cells than those with 13-06-MG parental cells. Initially, the immunoselected cells were less sensitive to aCTL lysis; however, the reduced aCTL-sensitivity was not maintained upon further selection. We therefore isolated IR clones from continuously immunoselected cells (13-06-CSP). The frequency of IR clones was 1-6 cells per 10,000 immunoselected cells. Two clones selected for further study, 13-06-IR29 and 13-06-IR30, resisted aCTL lysis in the absence of immunoselective pressure. Cytogenetic analyses revealed structural anomalies and genomic imbalances unique to the IR clones. Based on these findings, a hypothetical model is proposed that traces the origin of the IR clones to a clonal variant within the 13-06-CSP and 13-06-MG populations.

Opinion: emerging mechanisms of tumour lymphangiogenesis and lymphatic metastasis

Malignant tumours can spread to lymph nodes through lymphatic vessels. Recent studies show that tumours produce a range of growth factors that directly or indirectly stimulate lymphatic vessel growth (lymphangiogenesis) and lymphatic metastasis. These findings indicate that tumour lymphangiogenesis, similar to haemangiogenesis, is a complex process that is regulated by multiple growth factors. Understanding the underlying mechanisms by which tumours induce lymphangiogenesis might provide important information for the therapeutic intervention of metastatic spread.

Receptor expression, cytogenetic, and molecular analysis of six continuous human glioma cell lines

Six human glioma cell lines were established from tissues obtained from five patients diagnosed with Kernohan grade IV glioblastoma multiforme and one from a patient with a grade II astrocytoma. One line was from a recurrent patient who had received prior therapy; the other lines were derived from patients at initial diagnosis and/or before cytoreductive therapies other than surgery were given. Considerable variability in phenotypic, karyotypic, and cell surface marker expression was displayed between the six human glioma cell lines. The karyotypes ranged from apparently normal (grade II astrocytoma) to those with complex rearrangements. Trisomy of chromosome 7 was the most common abnormality. The extensive cytogenetic and molecular characterization of these lines may facilitate their utilization in cellular and molecular biologic studies.

Establishment and characterization of a human glioblastoma multiforme cell line

Cell lines provide a useful system for further understanding the biology of glioblastoma multiforme. In this study, a new glioblastoma multiforme cell line, GATAGM-96 (Gulhane Askeri Tip Akademisi-Gliblastoma Multiforme-96), was established from a tumor specimen removed from an 80-year-old male patient who underwent surgery for intracranial tumor. Morphologic examination, immunocytochemical staining, growth kinetics, and karyotypic characteristics of this cell line were studied. The cytoskeleton was positive for neuron-specific enolase, vimentin, and neurofilament, and it was negative for glial fibrillary acidic protein, S-100 protein, p53 protein, epidermal growth factor, and transforming growth factor alpha. Growth kinetic studies demonstrated an approximate population doubling time of 38 to 42 h and a colony forming efficiency of 83.3%. The karyotype of the cells demonstrated it as hyperdiploid, with a large subpopulation of polyploid cells. There were numerous structural and numerical chromosome aberrations; most of them were present as clonal events. The phenotypic and chromosomal features detailed on the GATAGM-96 cell line should make it a useful addition to the cell lines currently available for in vitro and in vivo studies of glioblastoma multiforme.