Immunocytochemical characterization of long-term medulloblastoma cultures: preliminary report

In vitro karyotypic and immunophenotypic characterisation of primitive neuroectodermal tumours: similarities to malignant gliomas

Monoclonal antibody (Mab) mediated immunotherapy of brain tumours requires the identification of tumour-restricted cell surface antigens. We have characterised four primitive neuroectodermal tumours, which included pineoblastoma, medulloblastoma and ependymoblastoma cultures, that demonstrated in vitro evidence of malignant behaviour (anchorage-independent growth and nu/nu xenograft tumour formation). The cytogenetic findings ranged from normal G-banded and Q-banded karyotypes through mixed near-diploid/hyperdiploid. These cultures resembled the cell surface immunophenotypic spectrum of malignant gliomas. They were distinguished from normal glia in vitro by the expression of restricted fetal mesenchymal, neuronal, myoblastic, melanocytic, epidermal, chondrocytic, lymphoid and epithelial antigens. Certain antigens appeared sufficiently represented among central nervous system (CNS) neoplasms to afford potential targets for Mab-mediated immunotherapy.

Comparison of in vitro activity of epipodophyllotoxins with other chemotherapeutic agents in human medulloblastomas

Surgical specimens from 15 medulloblastoma patients were used to establish early passage cultures. In vitro sensitivity to a battery of cytotoxic agents, including some in current medulloblastoma treatment protocols, was measured. Drug sensitivity was assessed at clinically relevant drug concentrations using the 3H-thymidine uptake method. Tumours were predicted to be sensitive if greater than 37% were killed by exposure to drugs at clinically achievable levels. A poor response to vincristine (Vcr), cis-platin (CDDP), hydroxyurea (HU) or diaziquone (AZQ) (no responders), and cytosine arabinoside (AraC) (1/12), was seen. Nine of ten tumours tested were sensitive to mafosfamide (Mfs); seven out of 12 were sensitive to carmustine (BCNU), 12 of 13 to teniposide (VM-26) and seven of 13 to etoposide (VP16-213). VM-26 was the best of the agents tested with most tumours responding to very low concentrations of drug, suggesting that the role of epipodophyllotoxins in treatment of brain tumours be further investigated. Despite the marked sensitivity of the medulloblastomas to the epipodophyllotoxins, three early passage cultures were much more resistant to these drugs than the average for the group. The basis of this resistance was investigated. Deficient cellular uptake of drug was excluded as a cause of resistance. One resistant early passage culture displayed low cellular activity of topoisomerase II and decreased levels of drug induced enzyme-DNA strand break activity. This was not the case for the other resistant early passage cultures: the basis of resistance in these cells does not appear to be due to any previously reported mechanism.

The prognostic significance of glial fibrillary acidic protein staining in medulloblastoma

Histologic and immunohistochemical properties of 53 medulloblastomas were analyzed with regard to clinical features and survival rate. No correlation was found between survival rate and histologic features of the tumor, such as desmoplastic reaction, number of mitoses, hemorrhages, necrosis, endothelial proliferation, glomerular arrangement, calcifications, rosettes, or oligodendroglial cells. However 82% of the patients with positive glial fibrillary acidic protein (GFAP) staining in numerous tumor cells survived more than 5 years; only 30% survived that long if their tumor cells were GFAP negative (P = 0.0093). This significant difference was not related to the mode of therapeutic protocol used. The authors suggest that GFAP staining may be a useful prognostic tool in medulloblastoma.