[Loss of heterozygosity of chromosome 1p/19q and p53 protein expression in oligodendroglioma]

Abstract

Objective: To study the status of loss of heterozygosity (LOH) of chromosome 1p/19q and p53 protein expression in oligodendroglioma, as compared to astrocytoma.

Methods: One hundred and ninety-one cases of glioma of different histologic types and grades, including 116 cases of low-grade of oligodendroglioma (86 paraffin-embedded and 30 fresh tissues), 45 cases of anaplastic oligodendroglioma (all paraffin-embedded tissues) and 30 cases of astrocytoma of various grades (all paraffin-embedded tissues), were enrolled into the study. The LOH of chromosome 1p/19q was investigated by polymerase chain reaction (PCR)-based microsatellite analysis. The p53 protein expression was demonstrated by immunohistochemical staining.

Results: The rates of 1p loss, 19q loss and 1p/19q loss were 69.8%, 64%, and 57.0% respectively in the 86 paraffin-embedded low-grade oligodendroglioma samples, as compared to 71.1%, 60.0% and 55.6% respectively in the 45 paraffin-embedded anaplastic oligodendroglioma samples. There was no difference of LOH of 1p/19q between low-grade oligodendroglioma and anaplastic oligodendroglioma (P>0.05). In the 30 cases of low-grade oligodendroglioma with fresh tissues available, the rates of 1p loss, 19q loss and 1p/19q loss were 70.0%, 63.3% and 60.0% respectively. The LOH of 1p/19q between paraffin-embedded and fresh samples was not statistically significant (P>0.05). In the 30 cases of astrocytoma, the rates of 1p loss, 19q loss and 1p/19q loss were 23.3%, 33.3% and 20.0% respectively, which were significantly less than those in oligodendroglioma (P<0.05). The expression of p53 protein was significantly lower in low-grade oligodendroglioma (8.1%) than in anaplastic oligodendroglioma (31.1%, P=0.007). The expression of p53 protein in oligodendroglioma was also lower than in astrocytoma (P=0.001). Furthermore, p53 protein expression negatively correlated with 1p/19q loss in anaplastic oligodendroglioma (P<0.05).

Conclusions: Both paraffin-embedded and fresh tissues are suitable for analysis of LOH of chromosome 1p/19q. Oligodendroglioma demonstrates a higher frequency of LOH of chromosome 1p/19q and lower expression of p53 protein than astrocytoma. The LOH of chromosome 1p/19q negatively correlates with the expression of p53 protein. These parameters have both diagnostic and prognostic values.