Objective: To study the expression level of folate receptor α (FR-α) in glioma tissue and its clinical significance.
Methods: Forty-eight human glioma specimens were collected from patients who underwent surgery from March 2012 to March 2013. These specimens were as follows:12 cases of glioblastoma (WHO IV), 6 cases of astrocytoma of each malignancy grade(WHO II, III), 6 cases of oligodendroastrocytoma of each malignancy grade (WHO II, III), 6 cases of oligodendroglioma of each malignancy grade (WHO II, III ). In addition, 6 cases of normal brain tissue resected from brain traumatic patients were taken as negative control, and one case of placental tissue (had got the consent of the parents and their families) was taken as positive control. The expression level of FR-α in tumor tissues was evaluated by Western blot analysis. The results of Western blot analysis were analyzed by t-test. The expression level of FR-α and Ki-67 in tumor tissues was evaluated immunohistochemistry, the results were analyzed by Kruskal-Wallis test and Nemenyi test. The correlation between the expression level of FR-α and cell proliferation index Ki-67 was analyzed by Pearson correlation analysis.
Results: Western blot analysis showed that the FR-α was not expressed in normal brain tissue and oligodendroglioma tissue, but highly expressed in astrocytoma, oligodendroastrocytoma and gliomablastoma. The expression level in WHO III astrocytoma was significantly higher than in WHO II (t = 4.497, P < 0.05). FR-α was also highly expressed in oligodendroastrocytoma and its expression level in WHO III was also significantly higher than in the WHO II (t = 2.876, P < 0.05). Foremore, immunohistochemistry analysis also showed that FR-α was not expressed in oligodendroglioma, but expressed in astrocytoma, oligodendroastrocytoma and gliomablastoma. The positive rate of FR-α of WHO III was significantly higher than the WHO II astrocytoma(57.8% ± 2.2% vs. 45.7% ± 2.3%,χ(2) = 3.871, P = 0.034). In oligodendroastrocytoma, the positive rate of FR-α of WHO III was significantly higher than the WHO II(56.5% ± 5.4% vs. 37.1% ± 5.2%,χ(2) = 4.454, P = 0.021). Moreover, the expression level of FR-α in gliomablastoma was highest in all histological types of gliomas, the positive rate of FR-α was up to 65.0% ± 4.5%. Pearson correlation analysis showed that the positive rate of FR-α was positively correlated with Ki-67 index (r = 0.903, P < 0.05).
Conclusions: FR-α is expressed in astrocytoma, oligodendroastrocytoma and glioblastoma, and the expression level of FR-α is positively correlated with malignancy grade and Ki-67 index. Therefore, FR-α may be applied as a special target for diagnosis and treatment of glioma.