High-grade Oligodendrogliomas Research Articles

Arterial Spin-Labeling and MR Spectroscopy in the Differentiation of Gliomas

Noninvasive grading of gliomas remains a challenge despite its important role in the prognosis and management of patients with intracranial neoplasms. In this study, we evaluated the ability of cerebral blood flow (CBF)-guided voxel-by-voxel analysis of multivoxel proton MR spectroscopic imaging ((1)H-MRSI) to differentiate low-grade from high-grade gliomas. A total of 35 patients with primary gliomas (22 high grade and 13 low grade) underwent continuous arterial spin-labeling perfusion-weighted imaging (PWI) and (1)H-MRSI. Different regions of the gliomas were categorized as "hypoperfused," "isoperfused," and "hyperperfused" on the basis of the average CBF obtained from contralateral healthy white matter. (1)H-MRSI indices were computed from these regions and compared between low- and high-grade gliomas. Using a similar approach, we applied a subgroup analysis to differentiate low- from high-grade oligodendrogliomas because they show different physiologic and genetic characteristics. Cho(glioma (G)/white matter (WM)), Glx(G/WM), and Lip+Lac(G)/Cr(WM) were significantly higher in the "hyperperfused" regions of high-grade gliomas compared with low-grade gliomas. Cho(G/WM) and Lip+Lac(G)/Cr(WM) were also significantly higher in the "hyperperfused" regions of high-grade oligodendrogliomas. However, metabolite ratios from the "hypoperfused" or "isoperfused" regions did not exhibit any significant differences between high-grade and low-grade gliomas. The results suggest that (1)H-MRSI indices from the "hyperperfused" regions of gliomas, on the basis of PWI, may be helpful in distinguishing high-grade from low-grade gliomas including oligodendrogliomas.

Comparison of Magnetic Resonance Spectroscopy and Perfusion-weighted Imaging in Presurgical Grading of Oligodendroglial Tumors

Oligodendroglial tumors form an uncommon, but distinct, subgroup of gliomas with longer survival, better treatment response, and characteristic genetic alterations. Noninvasive grading of oligodendroglial tumors using functional and metabolic magnetic resonance imaging may be helpful in guiding the treatment approach and predicting malignant transformation of these tumors. We used perfusion-weighted magnetic resonance imaging and proton magnetic resonance spectroscopic imaging (MRSI) to predict the oligodendroglioma grade. Twenty-four patients with pathologically confirmed oligodendrogliomas underwent dynamic contrast-enhanced perfusion-weighted magnetic resonance imaging and/or proton MRSI before surgery. We assessed the ability of tumor contrast enhancement, normalized cerebral blood volume, normalized choline, and the presence of either lactate or lipid metabolites to correctly predict the World Health Organization tumor grade. The accuracy of tumor grading using each method was also compared. Tumor contrast enhancement (P = 0.069) and normalized cerebral blood volume (P = 0.181) were not significantly different between low and high-grade oligodendrogliomas. The MRSI measurement of normalized choline was significantly higher in high-grade (2.82 +/- 0.64) than in low-grade (1.62 +/- 0.46) oligodendrogliomas (P < 0.001), and the presence of lactate or lipid metabolites also correctly predicted high-grade tumors (P = 0.014). The maximum accuracy of contrast enhancement, normalized cerebral blood volume, normalized choline, and lactate or lipid metabolites in grading oligodendroglioma was 71, 83, 90, and 85%, respectively. MRSI measurements are more accurate than perfusion-weighted magnetic resonance imaging or conventional contrast enhancement in differentiating oligodendroglial tumor grade. In these inherently vascular tumors, metabolic measurements of mitosis and necrosis may be better than measures of neovascularity in presurgical grading.

Galectin‐3 as an Immunohistochemical Tool to Distinguish Pilocytic Astrocytomas from Diffuse Astrocytomas, and Glioblastomas from Anaplastic Oligodendrogliomas

The distinction of astrocytomas and oligodendrogliomas, mainly pilocytic astrocytomas (PILOs) from infiltrating astrocytomas and oligodendrogliomas (ODs), and high-grade oligodendrogliomas from glioblastomas (GBMs), poses a serious clinical problem. There is no useful immunohistochemical (IHC) marker to differentiate these gliomas, and sometimes the differential diagnosis between them is arbitrary. We identified galectin-3 (Gal-3) as a possible tool to differentiate them based on gene expression profiles of GBMs. We confirmed the differential expression in 45 surgical samples (thirteen GBMs; seven PILOs; 5 grade II ODs; 5 anaplastic oligodendrogliomas [AODs], including 2 Oligo-astrocytomas; 8 diffuse astrocytomas [ASTs], and 7 non-neoplastic samples) by quantification of Gal-3 gene expression by real-time quantitative PCR (rt-PCR). Higher expression of Gal-3 was observed in GBMs and PILOs than in OD, AODs and ASTs. The IHC expression of Gal-3 was evaluated in 90 specimens (fifteen PlLOs, fourteen ASTs, 10 anaplastic astrocytomas, fifteen GBMs, eleven ODs, fifteen AODs, and 10 dysembryoplastic neuroepithelial tumors). The mean labeling score for Gal-3 determined according to the percentage of labeled cells in the tumor bulk was significantly different in GBMs versus AODs and in PILOs versus ASTs. Hence, Gal-3 is differentially expressed in central nervous system tumors, making IHC detection of Gal-3 a useful tool in distinguishing between these gliomas.

Dose-dependent effects of platelet-derived growth factor-B on glial tumorigenesis.

Platelet-derived growth factor (PDGF) is expressed in many different tumors, but its precise roles in tumorigenesis remain to be fully defined. Here, we report on a mouse model that demonstrates dose-dependent effects of PDGF-B on glial tumorigenesis. By removing inhibitory regulatory elements in the PDGFB mRNA, we are able to substantially elevate its expression in tumor cells using a retroviral delivery system. This elevation in PDGF-B production results in tumors with shortened latency, increased cellularity, regions of necrosis, and general high-grade character. In addition, elevated PDGF-B in these tumors also mediates vascular smooth muscle cell recruitment that supports tumor angiogenesis. PDGF receptor (PDGFR) signaling appears to be required for the maintenance of these high-grade characteristics, because treatment of high-grade tumors with a small molecule inhibitor of PDGFR results in reversion to a lower grade tumor histology. Our data show that PDGFR signaling quantitatively regulates tumor grade and is required to sustain high-grade oligodendrogliomas.

Expression of cyclin A and topoisomerase IIalpha of oligodendrogliomas is correlated with tumour grade, MIB-1 labelling index and survival.

This study was designed to investigate immunoexpression of cyclin A and D1, and topoisomerase IIalpha in oligodendrogliomas and to evaluate the correlation with MIB-1 (Ki67), tumour grade, and survival of the patients. Forty cases of oligodendrogliomas (20 high- and 20 low-grade) were studied immunohistochemically with the above-mentioned monoclonal antibodies. Normal brain tissues included in tumour sections did not express any of cyclin A, MIB-1 and topoisomerase IIalpha except cyclin D1, which was shown in perineuronal and interfascicular normal oligodendroglial cells. In low-grade and high-grade oligodendrogliomas, the mean cyclin A labelling index (LI) was 1.18 +/- 0.98% versus 4.65 +/- 1.99%, respectively; the mean topoisomerase IIalpha LI was 1.32 +/- 1.04% versus 6.63 +/- 4.31%, respectively; and the mean MIB-1 LI was 1.69 +/- 1.55% versus 9.46 +/- 4.66%, respectively. Interestingly, cyclin D1 was not expressed in any oligodendrogliomas. Both cyclin A and topoisomerase IIalpha LI showed a significant positive correlation with MIB-1 LI and histological grade of oligodendrogliomas (P < 0.01) and an inverse correlation with overall survival (P < 0.01). Univariate analysis showed that cyclin A and topoisomerase IIalpha LIs with a cut-off point at 3% were a significant prognostic factor (P: cyclin A = 0.0040, topoisomerase IIalpha = 0.0033). Cyclin A and topoisomerase IIalpha expression are closely correlated with anaplastic oligodendrogliomas and worse clinical outcomes. Cyclin D1 seems not to be involved in the tumorigenesis of oligodendrogliomas.

Immunohistochemical markers for prognosis of oligodendroglial neoplasms.

Despite numerous previous studies, oligodendrogliomas continue to generate considerable controversy in the identification of prognostic factors, including single histopathological patterns, and grade of tumor malignancy. The prognostic significance of various pathological and immunohistochemical factors has been intensively examined but numerous studies have yielded conflicting results. In the present study, biopsy samples of 123 oligodendrogliomas were examined immunohistochemically to evaluate a possible association between expression of various tumor-associated antigens and clinical outcome. Both the progression-free and overall survival times were significantly reduced for high-grade tumors, for Ki-S1 labeling index (LI) > 10%, for p27 LI < 20% and for p18, p53, and vascular endothelial growth factor (VEGF)-positive tumors. For low-grade tumors survival rates were significantly reduced for p27 LI less than 20%, whereas high-grade oligodendrogliomas with Ki-S1 LI greater than 10%, and with p18 positivity revealed significantly shortened survival times. We found no differences in survival times in patients with or without p 14ARF, p21, mdm2, and pRb immunoreactivity. Multivariate analysis revealed that risk of oligodendroglioma progression is associated with high-grade tumors, with Ki-S1 LI > 10%, and with p27 LI < 20%; whereas risk of death is associated with high-grade tumors, with Ki-S1 LI > 10%, and with p18 positivity. CART modeling process identified four final groups of oligodendroglioma patients: (1) thirty-nine patients with low-grade tumors and p27 LI > 20%; (2) twenty patients with low-grade tumors and p27 LI < 20%; (3) thirty-four patients with high-grade tumors and Ki-S1 LI < 10%; and (4) thirty patients with high-grade tumors and Ki-S1 LI >10%. In summary, both the p27 and Ki-S1 scores were found to be the strong predictors of oligodendroglioma outcome together with the WHO tumor grade and they seem to be useful for assessing individual prognosis in routinely processed specimens.

The prognostic significance of DNA topoisomerase II-alpha (Ki-S1), p21/Cip-1, and p27/Kip-1 protein immunoexpression in oligodendrogliomas.

To evaluate a possible association between clinical outcome of patients with oligodendroglioma and expression of 2 cyclin-dependent kinase inhibitors, p21/Cip-1 (p21) and p27/Kip-1 (p27), and of DNA topoisomerase II-alpha (Ki-S1), which has been recently used as a marker of cellular proliferation. Ninety-one specially selected patients with cerebral oligodendrogliomas treated with surgery and radiotherapy were studied retrospectively. Tumor specimens were immunohistochemically examined with antibodies to p21, p27, and Ki-S1. A computerized color image analyzer was used to count immunostained nuclei. The mean Ki-S1 labeling index (LI) was found to be significantly prominent for World Health Organization (WHO) high-grade tumors (9.5% vs. 3.2% for WHO low-grade tumors). In contrast, the mean p27 LI was significantly higher for low-grade tumors (43.3% vs 25.7% for high-grade tumors). The number of p21-positive cases and the mean p21 LI were found to be relatively equal for low- and high-grade tumors. For low-grade oligodendrogliomas, the progression-free and overall survival times were found to be significantly shorter for tumors with p27 LIs less than 20%. For high-grade oligodendrogliomas, survival times were significantly reduced for tumors with Ki-S1 LIs greater than 10%. Regression-tree analysis identified 4 groups of oligodendrogliomas with distinctly different outcomes: (1) 32 patients with low-grade tumors and p27 LIs greater than 20%; (2) 14 patients with low-grade tumors and p27 LIs less than 20%; (3) 25 patients with high-grade tumors and Ki-S1 LIs less than 10%; and (4) 20 patients with high-grade tumors and Ki-S1 LIs greater than 10%. Immunoreactivity for Ki-S1 and p27 was found to be useful for further subdividing oligodendroglioma prognoses among low-grade and high-grade tumors. It seems unlikely that p21 immunohistochemistry will be of value for determining clinical outcomes for patients with oligodendrogliomas.

Oligodendroglioma: an analysis of prognostic factors and treatment results.

This study, an analysis of variable prognostic factors affecting the treatment outcome for patients with oligodendroglioma, included a retrospective analysis of the medical charts of patients diagnosed with oligodendroglioma treated at our institution between 1975 and 1997. The endpoints analyzed were the progression-free survival (PFS), as well as the overall survival. The factors analyzed included extent of surgery, postoperative radiotherapy, pathologic grade, performance status, age, and sex. Of a total of 37 cases, 19 were male and 18 were female. The median age at diagnosis was 30 years. The most common presenting symptoms were headache (78%), seizures (43%), motor symptoms (38%), and to a lesser extent behavioral changes (16%). The median duration of symptoms was 9 months. The most common location on computed tomography or magnetic resonance imaging scans was the frontal region (43%). Low grade tumors (grades I and II) were found in 60% of patients, and the remaining 40% had high grade tumors (grades III and IV). Eight patients had complete surgical excision, whereas 27 patients had partial excision, and two patients had biopsy only. The operative mortality rate was 14%. There were 24 patients who received postoperative radiotherapy, and only 3 patients received adjuvant chemotherapy. The median postoperative radiation dose was 5,580 cGy. With a median follow-up of 7 years, the 5-year PFS and overall survival for the whole group were 58% and 67%, respectively. The pathologic grade of the tumor was the only prognostic factor significantly affecting both PFS and overall survival. The 5-year PFS for patients with low grade tumors was 79% in comparison to 32% for patients with high grade tumors (p < 0.01). Patients with good performance status at initial presentation (performance status of 1 and 2) had a higher 5-year PFS in comparison to those with poor performance status (62% vs. 38%, respectively); however, this difference did not reach statistical significance. Similarly, patients who were subjected to complete surgical excision had a marginally higher PFS in comparison to those who had biopsy or partial excision (75% vs. 53%). There was no difference in the 5-year PFS between patients who received postoperative irradiation versus those who did not (51% vs. 47%, respectively). Patients with high grade oligodendrogliomas have a relatively poor prognosis. The pathologic grade of the tumor was the single most important prognostic factor significantly affecting both the PFS and overall survival. A prospective randomized clinical trial is needed to address the impact of postoperative irradiation on PFS of those tumors. In view of the poor outcome for patients with high grade oligodendroglioma, the use of adjuvant systemic chemotherapy should be studied in future multicenter randomized trials.

Homozygous deletions of the CDKN2C/p18INK4C gene on the short arm of chromosome 1 in anaplastic oligodendrogliomas.

Allelic deletions of the short arm of chromosome 1 are common in oligodendrogliomas and have been correlated with chemosensitivity and better prognosis in patients with high-grade oligodendrogliomas. In these tumors, 1p loss is also inversely related to deletions of the CDKN2A gene on 9p, which encodes the key cell cycle regulatory molecule p16INK4A. Because the CDKN2C gene, which encodes the homologous p18INK4C cell cycle regulatory protein, maps to chromosomal band 1p32, CDKN2C is an attractive candidate for the oligodendroglioma suppressor gene on chromosome 1. To evaluate this possibility, we studied 39 high-grade oligodendrogliomas for homozygous deletions and point mutations of the CDKN2C gene, as well as for allelic loss of 1p. Although no mutations were detected in the CDKN2C coding region, two tumors had homozygous deletions that involved CDKN2C. Interestingly, these cases did not have CDKN2A gene deletions. Coupled with the recent report of rare point mutations of CDKN2C in oligodendrogliomas, these findings suggest that CDKN2C inactivation may be oncogenic in a small percentage of human oligodendrogliomas.

Expression of interleukin-1beta mRNA and protein in human gliomas assessed by RT-PCR and immunohistochemistry.

To characterize the expression and localization of interleukin (IL)-1beta in human gliomas, both reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry were used on surgically excised human gliomas, human malignant glioma xenografts, and human glioblastoma cell lines. The RT-PCR products for IL-1beta mRNA were quantified by computerized image analysis. IL-1beta mRNA was detectable in 30 out of 35 (86%) surgically resected gliomas. An abundant expression of IL-1beta mRNA was often found in the glioblastomas, anaplastic astrocytomas, and pilocytic astrocytomas, but not in other types of gliomas. Quantitatively, in both the grade 2 astrocytomas and the oligodendrogliomas, the IL-1beta mRNA levels were significantly (p < 0.05) lower than those of the grade 3/4 astrocytomas. Immunohistochemically, IL-1beta was localized in the pleomorphic tumor cells of the astrocytic tumors and in macrophages. In contrast to the astrocytic tumors, low and high grade oligodendrogliomas showed no or little expression of IL-1beta antigen. IL-1beta was present less frequently than IL-1alpha and IL-1 receptor type 1 in 4 malignant gliomas transplanted into nude mice by RT-PCR. All 2 cell lines showed IL-1beta expression at both the mRNA and protein levels. It is concluded that in human gliomas, both high-grade astrocytomas and pilocytic astrocytomas often express high IL-1beta production, and that IL-1beta is mainly localized in astrocytic tumor cells and macrophages.

Screening for loss of heterozygosity and microsatellite instability in oligodendrogliomas

To assess the frequency of loss of heterozygosity (LOH) and microsatellite instability (MI) in oligodendrogliomas, we performed an extensive screening of 16 oligodendrogliomas and nine anaplastic oligodendrogliomas by using 132 microsatellite markers on chromosomes 1 through 12 and 15 through 21. In total, 3,135 loci were examined in 25 tumor samples. Only 33/1,965 (1.7%) of oligodendroglioma (low-grade) and 11/1,070 (1.0%) of anaplastic oligodendroglioma (high-grade) loci exhibited MI. High-frequency LOH regions were identified on chromosome arms 1p (31-73% for oligodendrogliomas and 60-100% for anaplastic oligodendrogliomas) and 19q (23-69% for oligodendrogliomas and 100% for anaplastic oligodendrogliomas). In addition, regions on chromosomes 4, 6, and 11 were found to be lost in 30-80% of both oligodendrogliomas and anaplastic oligodendrogliomas. Increased LOH frequency of chromosome 17 (38-40%) was found only in high-grade oligodendrogliomas. The differences in LOH frequencies between low-grade and high-grade oligodendrogliomas in all loci combined and at three loci (DIS447, DIS226, and DIS252) on chromosome arm 1p were determined to be statistically significant [chi 2(1) = 20.2, P < 0.0001, and Fisher's exact test respective P values: 0.01, 0.03, and 0.02]. Our results provide evidence that microsatellite instability does not play an important role in the development of oligodendrogliomas. Furthermore, high LOH frequency on chromosomes 6 and 11 in addition to that identified previously on chromosomes 1, 19, and 4 suggests that multiple candidate tumor suppressor genes on these chromosomes may underlie the processes of initiation and/or progression in oligodendroglioma tumorigenesis.

Screening for loss of heterozygosity and microsatellite instability in oligodendrogliomas.

To assess the frequency of loss of heterozygosity (LOH) and microsatellite instability (MI) in oligodendrogliomas, we performed an extensive screening of 16 oligodendrogliomas and nine anaplastic oligodendrogliomas by using 132 microsatellite markers on chromosomes 1 through 12 and 15 through 21. In total, 3,135 loci were examined in 25 tumor samples. Only 33/1,965 (1.7%) of oligodendroglioma (low-grade) and 11/1,070 (1.0%) of anaplastic oligodendroglioma (high-grade) loci exhibited MI. High-frequency LOH regions were identified on chromosome arms 1p (31-73% for oligodendrogliomas and 60-100% for anaplastic oligodendrogliomas) and 19q (23-69% for oligodendrogliomas and 100% for anaplastic oligodendrogliomas). In addition, regions on chromosomes 4, 6, and 11 were found to be lost in 30-80% of both oligodendrogliomas and anaplastic oligodendrogliomas. Increased LOH frequency of chromosome 17 (38-40%) was found only in high-grade oligodendrogliomas. The differences in LOH frequencies between low-grade and high-grade oligodendrogliomas in all loci combined and at three loci (DIS447, DIS226, and DIS252) on chromosome arm 1p were determined to be statistically significant [chi 2(1) = 20.2, P < 0.0001, and Fisher's exact test respective P values: 0.01, 0.03, and 0.02]. Our results provide evidence that microsatellite instability does not play an important role in the development of oligodendrogliomas. Furthermore, high LOH frequency on chromosomes 6 and 11 in addition to that identified previously on chromosomes 1, 19, and 4 suggests that multiple candidate tumor suppressor genes on these chromosomes may underlie the processes of initiation and/or progression in oligodendroglioma tumorigenesis.

Chemotherapy for aggressive or anaplastic high grade oligodendrogliomas and oligoastrocytomas: better than a salvage treatment

This series reports a pilot study of chemotherapy conducted for newly diagnosed and relapsing patients with oligodendrogliomas and oligoastrocytomas. Twenty-three patients with clinically or histologically aggressive tumours were eligible to receive procarbazine CCNU and vincristine (PCV) chemotherapy followed by radiotherapy in previously non irradiated patients. Sixteen (69%) responded to chemotherapy with complete responses in two patients and partial responses in 14. Previously irradiated patients were as likely to respond to PCV as those previously non irradiated. An over 1-year history of seizures was the main clinical prognostic factor of response. All toxicities were manageable and no treatment related deathsoccurred.Chemotherapy is an effective treatmentin aggressive oligodendrogliomas. Further studiesmustassessthe role of chemotherapy in the multidisciplinary management of oligodendroglioma.

In vitro and in vivo MRS study of human glioma metabolites

In this study an in vitro multinuclear magnetic resonance spectroscopy (MRS) characterization of water soluble metabolites and of the lipid fraction obtained from 19 human gliomas (12 glioblastomas, 3 anaplastic astrocytomas, 2 anaplastic oligodendrogliomas and 2 oligodendrogliomas) with a total of 27 surgical specimens, is reported. Moreover, some in vivo H-1 MRS results are shown. The regional metabolic heterogeneity of glioblastomas, according to their morphological heterogeneity, is documented. For glioblastomas a specific in vitro H-1 MRS metabolite profile cannot be defined. Low and high grade oligodendrogliomas showed characteristic choline/creatine and alanine/creatine metabolite ratios. The spectroscopical characterization of histopathological factors concerning malignant gliomas is shown.

High-grade Human Brain Tumors Exhibit Increased Expression of Myelin Transcription Factor 1 (MYT1), a Zinc Finger DNA-binding Protein

Detection and characterization of distinct central nervous system (CNS) tumor cell types is clinically important since distinct tumor types are associated with different prognoses and treatments. However, there is currently a lack of markers to identify certain glioma types and insufficient understanding as to which cells give rise to different glioma cell types. In the present study, biopsy specimens from human brain tumors were analyzed for expression of Myelin Transcription Factor 1 (MYT1) to explore the extent to which glioma cells reflect characteristic expression of MYT1 in developing glial progenitor cells. Immunostaining with an antibody against MYT1 revealed widespread immunoreactivity that was most prominent in high-grade oligodendrogliomas, astrocytomas, and mixed oligoastrocytomas as well as in a dysembryoplastic neuroepithelial tumor. MYT1 immunoreactivity in tumor regions generally correlated with the prevalence of cells exhibiting nuclear immunolabeling with an antibody against Ki-67, suggesting an association of MYT1 with cell proliferation that was also observed in normal adult human and rat brain in the germinal subependymal zone. The MYT1 immunoreactivity was frequently nuclear, appearing as dotted or punctate, but in some cases it was localized to the cytoplasm. In combination with histopathological studies and analysis of Ki-67 immunoreactivity, examination of MYT1 immunolabeling may provide additional information to aid in the detection and diagnosis of CNS tumors.

Allelic loss at 1p and 19q frequently occurs in association and may represent early oncogenic events in oligodendroglial tumors.

The molecular mechanisms underlying the genesis and progression of oligodendroglial tumors are poorly understood, since only restricted information on loss of heterozygosity from isolated cases is available. The commonest alterations appear to involve deletion of 1p and 19q, while loss of heterozygosity for 9p, chromosome 10 or epidermal growth factor receptor gene amplification have been described in single tumors. We have applied restriction fragment length polymorphism analysis to 14 loci covering chromosome 1 and 7 loci on chromosome 19 in a series of 25 tumors with an oligodendroglial component to determine precisely the participation of these suppressor genes in the genesis of tumors. Twenty-two and 19 of the 25 samples displayed LOH at 1p and 19q, respectively, and both anomalies were detected in association in 17 samples, including low- and high-grade oligodendrogliomas as well as mixed oligo-astrocytomas. Our findings suggest that inactivation of tumor suppressor genes located on 1p and 19q represent cooperative alterations occurring at early stages of oncogenic transformation of oligodendroglial neoplasms.

Antigenic staining patterns of human glioma cultures: primary cultures, long-term cultures and cell lines

The immunocytochemical staining patterns of cultured glioma cells were investigated. Fifty nine individual cases were stained at different in vitro ages for glial fibrillary acidic protein, fibronectin, galactocerebroside, HNK-1/Leu 7, A2B5, vimentin, factor VIII and A4. Histologically, the cases were composed of eight low-grade astrocytomas, 11 high-grade astrocytomas, four low-grade oligodendrogliomas, seven high-grade oligodendrogliomas and 29 glioblastomas. The 45 cases were analysed within the first 3 weeks of culture, many of them as primary cultures. In 11 cases stainings were performed repeatedly at intervals of up to 6 months. Glial fibrillary acidic protein staining was positive in most of the early cultures of astrocytomas (low and high grade) and glioblastomas; expression in more than 50% of the cells was found in 1 of 5 low-grade astrocytomas, 5 of 11 high-grade astrocytomas and 14 of 29 glioblastomas. Two of the high-grade astrocytomas were stained once more after 6 weeks in culture and were found to be only 1% positive for glial fibrillary acidic protein but strongly positive for fibronectin. The same was true for five of the glioblastoma cases. Two of these cases remained glial fibrillary acid protein positive and developed into stable permanent cell lines. Only one case started with 1% of glial fibrillary acidic protein positive cells and later developed into a 99% glial fibrillary acidic protein positive cell line. Neither HNK-1/Leu 7 expression nor A2B5 staining appeared to have a relationship to the glial fibrillary acidic protein staining. It was observed that glial fibrillary acidic protein and HNK-1/Leu 7 were both 100% in some cases but that later one of the two antigens disappeared but not the other. The amount of glial fibrillary acidic protein staining does not allow the prediction of A2B5 staining. The study shows that initiation of primary cultures on an extracellular matrix yields more glial fibrillary acidic protein positive cells in primary cultures than have been found in other studies. It is concluded that only a rigid standardization of culture conditions will ensure the validity of comparisons of in vitro data obtained in primary cultures.