Glioblastoma multiforme is the most malignant astrocytic glioma and usually resistant to chemotherapy. A small fraction of glioblastomas may contain areas with histological features of oligodendroglial differentiation. To determine the molecular genetic alterations in such "glioblastomas with oligodendroglial component", we investigated 13 of these tumors for genetic alterations and/or expression of the TP53, CDKN2A, PTEN, and EGFR genes. In addition, we performed microsatellite analyses for loss of heterozygosity (LOH) on chromosome arms 1p, 19q and 10q. None of tumors showed evidence for LOH on 10q. LOH on 1p was detected in 3 tumors, 1 of which additionally showed LOH on 19q. The 3 tumors with LOH on 1p showed neither TP53 mutations nor nuclear p53 accumulation. In contrast, 9 of 10 tumors without demonstrated losses on 1p showed nuclear p53 accumulation. TP53 mutations were identified in 3 of these cases. Further aberrations detected were epidermal growth factor receptor (EGFR) overexpression (3 of 13 tumors), homozygous CDKN2A deletion (2 of 11 tumors), and PTEN mutation (1 of 13 tumors). Taken to-gether, our results indicate that "glioblastomas with oligodendroglial component" carry heterogeneous genetic alterations. LOH on 10q, PTEN mutation, and homozygous CDKN2A deletion appear to be less common in these tumors as compared to ordinary glioblastomas. Furthermore, a subset of these tumors demonstrates LOH on 1p, i.e., an alteration that has recently been linked to chemosensitivity and good prognosis in anaplastic oligodendrogliomas.

Despite multimodal therapy, glioblastoma multiforme (GBM) is associated with a poor prognosis with a median survival of less than 1 year. However, a small number of patients with GBM shows survival times of several years. Although clinical features like age and performance status at diagnosis are well known prognostic parameters, molecular markers for prognosis of overall survival are still lacking. Therefore, we compared 2 age- and gender-matched groups of GBM patients with different post-operative time to tumor progression (TTP), defined as 'short-term' for TTP of less than 6 months (n = 21), and 'long-term' for TTP of more than 24 months (n = 21) for genetic alterations of the PTEN, CDKN2A and TP53 genes as well as overexpression of the EGFR, p53 and Mdm2 proteins. For the GBMs with 'short-term' TTP vs. 'long-term' TTP, the studies revealed PTEN mutations in 4/21 vs. 2/21, TP53 mutations in 5/21 vs. 8/21, homozygous deletion of the CDKN2A gene in 5/21 vs. 6/21, overexpression of EGFR in 7/20 vs. 10/20, accumulation of p53 protein in 9/20 vs. 7/20 and of Mdm2 protein in 0/20 vs. 1/20 cases studied. Taken together, our data indicate that mutations of the PTEN and TP53 tumor suppressor genes, homozygous deletion of the CDKN2A gene as well as overexpression of the EGFR, p53 and Mdm2 proteins lack prognostic significance for overall survival time in patients with GBMs.

Glioblastoma multiforme (WHO grade IV; GBM) is the most common primary brain tumor with a median survival of less than one year despite multimodal treatment regimens. However, a small subgroup of GBM patients has a better clinical outcome, with a small number of patients surviving several years. Apoptosis, a genetically determined program of cell suicide, may be induced as a consequence of critical DNA damage. However, due to defects in the signaling pathways, cancer cells may escape apoptosis, despite carrying irreversible DNA damage. In the present study, we have analyzed tumors of two age-matched, equally treated groups of GBM patients with different postoperative time to tumor progression (TTP), defined as 'short-term' for TTP of less than 6 months (n = 54), and 'long-term' for TTP of more than 12 months (n = 39) for alterations in apoptosis regulatory pathways: Mutations of the TP53 tumor suppressor gene and/or nuclear accumulation of its gene product p53, expression of Waf/p21, CD95 (Apo1/Fas), and Bcl-2. TP53 mutations were found in 12 out of 54 (22%) GBMs of short-term survivors and 8 out of 35 (23%) tumors of long-term survivors; the respective numbers for nuclear p53 protein accumulation were 12/53 (23%) and 10/37 (27%). Waf1/p21 expression was found in 13/53 (25%) tumors of short-term survivors and 9/35 (26%) GBMs of long-term survivors. The respective numbers for Bcl-2 expression were 25/42 (60%) and 22/36 (61%) and for CD95 (Apo1/Fas) expression 20/49 (41%) and 14/36 (39%) GBMs. The percentage of alterations in genes/proteins involved in the apoptotic pathway investigated here was virtually identical in the two groups of clinically different GBM patients. Thus, our data imply that none of these alterations investigated per se has a strong impact on the overall survival of GBM patients.