Induction of autophagy in temozolomide treated malignant gliomas

Autophagy is a dynamic process of protein degradation. Induction of autophagy by temozolomide (TMZ) has been noted in glioma cell lines. Twenty-eight specimens, obtained from 14 patients before and after TMZ treatment, were analyzed to investigate whether induction of autophagy could be detected in surgical specimens by immunohistochemical analysis. Macroautophagy was monitored by immunohistochemical analysis employing anti-light chain 3 isoform B (LC3B) and anti-lysosome-associated membrane protein 1 (LAMP1) antibodies; chaperone-mediated autophagy was monitored by anti-LAMP2A antibody immunostaining. Furthermore, detection of LC3B protein by Western blotting was performed on six specimens obtained from the preserved frozen tissues of three patients. All specimens showed dot-like staining for each immunostain in the cytoplasm of glioma cells, indicating induction of autophagy. LC3B, LAMP1 and LAMP2A immunostains were semiquantitatively scored from 1 to 3 points. Combination of the three scores after TMZ treatment (6.4 ± 1.2) showed a significant increase (P = 0.020) compared to pre-treatment scores (5.2 ± 1.5). Western blotting for LC3B showed increased LC3B-I and LC3B-II expression after TMZ treatment. The present study proved that autophagy monitoring by immunohistochemical staining of surgical specimens was feasible. These results suggest that autophagy is induced by TMZ.