[Common mechanism underlying oligodendrocyte development and oligodendrogliomagenesis]

A number of extrinsic factors and intracellular mechanisms have been revealed to be involved in oligodendrocyte development. For instance, sonic hedgehog induces the expression of basic helix-loop-helix (bHLH) transcription factors, Olig1 and Olig2, and a homeobox transcription factor Nkx2.2, both of which induce neural stem cells (NSCs) to differentiate into oligodendrocyte precursor cells when the factors work together. In contrast, Notch and bone morphogenic proteins (BMP) block oligodendrocyte differentiation by inducing the expression of the transcription inhibitors Hes5 and Id4, respectively. Moreover, it was shown that other extrinsic and intrinsic factors, including platelet derived growth factor, thyroid hormone (TH), TH receptors, p53, and Wnt, are also involved in the development, positively or negatively. It has been thought that oligodendroglioma, one of brain tumors, is generated from oligodendrocyte lineage cells as the tumor cells share characteristics of oligodendrocyte, such as the honeycomb structure, and the expression of oligodendrocyte-related factors, including Olig2 and NG2 proteoglycan. However, recent progress in the field revealed that oligodendroglioma might be generated from NSCs and astrocytes as well as oligodendrocyte lineage cells. Therefore, it is crucial to investigate the cell-of-origin of oligodendroglioma and to identify target genes and markers for the therapy. In this review, I summarize the mechanism of oligodendrocyte development and present how the oligodendrocyte research can help to understand and to investigate the mechanism of oligodendroglioma development.

Anaplastic oligoastrocytoma: previous treatment as a possible cause in a child with acute lymphoblastic leukemia

INTRODUCTION

The authors present a 14-year-old patient who developed an anaplastic oligoastrocytoma of the left parietal lobe 9 years after a successful treatment of acute lymphoblastic leukemia (ALL). He had a history of induction chemotherapy, intrathecal methotrexate and prophylactic whole brain irradiation (1,800 cGy in 10 fractions over 2 weeks).

DISCUSSION

Radiation-induced neoplasia is suggested to be the late complication of ALL treatment, and evaluation of large clinical series revealed a relationship between young age at ALL diagnosis (<6 years) and increased high-grade glioma occurrence risk.

CONCLUSION

The authors have reviewed previously reported cases of secondary central nervous system malignancies focusing on age at ALL diagnosis, and they think that synergistic action of therapeutic modalities could have played a role in the oncogenetic process. Detailed systematic radiological follow-up should be done in these patients especially if a personal history of cranial irradiation is present.

A case of diffuse leptomeningeal oligodendrogliomatosis associated with HHV-6 variant A

We describe a rare case of diffuse leptomeningeal oligodendrogliomatosis associated with the human herpes virus 6 variant A (HHV-6 A). A 2-year-old boy presented with progressive neurological symptoms and hydrocephalus. The patient had a VP shunt placement but did not fully recover. HHV-6 A was detected in both CSF and serum by nested PCR. His symptoms improved repeatedly, but temporarily, on antiviral treatment. An open brain biopsy, ten months after presentation, revealed leptomeningeal tumour as well as the presence of viral DNA in the tumour tissue. The role of HHV-6 A could be that of a reactivated opportunist. However, this case also raises the question whether this neurotropic virus, with malignant transforming properties in vitro, may have a role in pathogenesis in some cases of brain malignancy.

Astrocytes give rise to oligodendrogliomas and astrocytomas after gene transfer of polyoma virus middle T antigen in vivo

The cells of origin for oligodendrogliomas and astrocytomas are not known but are presumed to be oligodendrocyte and astrocyte precursors, respectively. In this paper we report the generation of mixed gliomas from in vivo transformation of glial fibrillary acidic protein (GFAP)-positive cells (differentiated astrocytes) with polyoma virus middle T antigen (MTA). MTA is a powerful oncogene that activates a number of signal transduction pathways, including those proposed to be involved in gliomagenesis, and has been shown to induce tumors in many cell types. We have achieved transfer of MTA expression specifically to GFAP(+) cells in vivo using somatic cell gene transfer, and find resultant formation of anaplastic gliomas with mixed astrocytoma and oligodendroglioma morphological features. We conclude that GFAP- expressing astrocytes, with appropriate signaling abnormalities, can serve as the cell of origin for oligodendrogliomas, astrocytomas, or mixed gliomas.

Spontaneous brain and spinal cord/nerve neoplasms in aged Sprague-Dawley rats

Primary malignant neoplasms of the brain and spinal cord occurred in 20/718 male (2.8%) and in 13/717 female (1.8%) Crl:CD Br strain Sprague-Dawley rats. Of 33 neoplasms, 30 were found in brain while 3 were in the spinal cord. In males and females, the most common brain neoplasm was astrocytoma (13 males, 9 females). Other neoplasms, granular cell tumor (1 male), mixed glioma (2 males, 1 female), reticulosis (1 male, 2 females), and oligodendroglioma (2 males), were especially uncommon. Spinal cord neoplasms included 2 schwannomas (1 male, 1 female) and an astrocytoma (1 male). The overall brain neoplasm incidence was similar for males (2.8%) compared to data compiled for this strain, and there was a 2-fold increase for females (1.8% vs 0.9%) compared to available incidence data.

Incidence of brain tumours in rats exposed to an aerosol of 239PuO2

Incidence of brain tumours was investigated in 3390 female and male Wistar rats exposed to an aerosol of 239PuO2, or as sham-exposed controls. Lung doses ranged from 0.05 to 22 Gy. In females, six brain tumours were found in 1058 control rats (incidence, 0.6%) and 24 brain tumours in 2134 rats exposed to Pu (incidence, 1.1%); the survival-adjusted level of significance was p = 0.29 for comparing control with exposed females. In males, two brain tumours were found in 60 control rats (incidence, 3.3%) and seven brain tumours in 138 rats exposed to Pu (incidence, 5.1%); the survival-adjusted level of significance was p = 0.33. Brain tumour incidence was about five times greater in male than in female rats (p = 0.0001), demonstrating a highly significant sex difference in brain tumour incidence. Tumour types were distributed similarly among control and Pu-exposed groups of both sexes; most tumours were astrocytomas. Mean lifespans for rats with brain tumours were not significantly different between control and Pu-exposed rats. Plutonium was not detected on autoradiograms of the brain. These results, like those for plutonium workers, show an increase of brain tumours which cannot be demonstrated statistically to be related to radiation exposure.

Oligodendroglioma occurring after radiation therapy for pituitary adenoma

A 38 year old male dentist developed an oligodendroglioma of the left medial temporal lobe and parasellar region 12 years after radiotherapy with 6600 rads of acromegaly. The 30 cases of radiation-induced gliomas reported in the English literature are reviewed and analysed. The criteria for defining radiation-induced tumours of the central nervous system are proposed as follows: the tumour has a long quiescent "latency period", a location in the previously irradiated field, a verified histological difference from a primary condition, and does not arise from a primary condition associated with a genetic syndrome such as neurofibromatosis or tuberous sclerosis. The reported case fulfilled these criteria but appears to be the only reported radiation-induced oligodendroglioma.

Oligodendrogliomas arising in the scar of a brain contusion. Report of two surgically verified cases

Several years after sustaining head injuries, two patients developed oligodendrogliomas in the scar of brain contusions. Both cases seem to fulfill the criteria currently established for accepting the traumatic origin of a brain tumor. The literature concerning the relationship between head injury and intracranial tumor is reviewed.

Influence of chronic Toxoplasma infection on ethylnitrosourea-induced central nervous system tumors in rats

Because prior work with mice had revealed remarkable inhibition of central nervous system (CNS) tumor by chronic Toxoplasma infection, the effect of immunomodulation produced by this obligate intracellular parasite was studied in rats which developed CNS tumors following transplacental exposure to the chemical carcinogen ethylnitrosourea. Groups of Fischer 344 rats which had been exposed to ethylnitrosourea were either uninfected or infected at 1 month of age with a virulent strain of Toxoplasma gondii. Rats were sacrificed when morbid symptoms from tumor growth developed, and neural tissue was prepared for light microscopy. Chronic Toxoplasma infection had no effect on the survival of rats or on the amount, location, or histological type of CNS tumor which developed. Although serum antibody to Toxoplasma was present in all infected rats for the duration of the experiment, there was no histological evidence in the brain of a cellular response to infection or to the presence of tumor. When these results are compared to prior experiments of CNS tumor in mice, they suggest that mechanisms of protection against Toxoplasma infection differ in mice and rats and that an inflammatory component produced by the Toxoplasma organism in the brain is a necessary prerequisite for tumor inhibition.

Concurrence of multiple sclerosis and glioma

Three cases are reported of concurrence of malignant gliomas (astrocytomas and glioblastomas) with multiple sclerosis (MS). This situation may lead to considerable diagnostic difficulties, yet an accurate appraisal is of prognostic, if not therapeutic, value. There is suggestive but inconclusive evidence that the two conditions may be causally related, malignant astrocytic tumours arising from plaques of MS. The small number of reported cases makes statistical analysis impossible, but the scanty literature may not reflect the true incidence.