Expressions of microtubule-associated protein 1 light chain 3B and autophagy-related gene Beclin 1 and their clinical significance in astrocytic tumors

Abstract

Objective To investigate the expressions of microtubule -associated protein 1 (MAP1) light chain 3B (LC3B) and autophagy-related gene Beclin1 in astrocytic tumors, and explore their correlations with the pathological features and clinical manifestations of astrocytic tumors to further reveal their roles in tumorigenesis and development of astrocytic tumors. Methods Sixty-two specimens with different-grade astrocytic tumors, including 4 with grade Ⅰ (pilocytic astrocytoma), 23 with grade Ⅱ (astrocytoma), 12 with grade Ⅲ (anaplastic astrocytoma) and 23 with grade Ⅳ (glioblastoma multiforme), were selected in our study. Immunohistochemistry was employed to detect the expression of Beclin1; the expressions of MAP 1-LC3B and Beclin1 were detected by Western blotting.The correlations between expressions of MAP 1-LC3B and Beclin 1 and both the pathological features and clinical manifestations of astrocytic tumors were analyzed. Results Immunohistochemistry showed decreased Beclin1 expression in the astrocytic tumors following the increase of tumor grades (P＜0.05).Western blotting indicated that the expressions of Beclin1 in tumors with different grades and these patients with different life cycles were significantly different (P＜0.05) and the average optical density ratio of Beclin1 in high-grade astrocytic tumors (grade Ⅲ/Ⅳ) was obviously lower than that in low-grade astrocytic tumors (grade Ⅰ/Ⅱ, P＜0.05). The expressions of LC3B-Ⅰ showed significant differences in different-grade astrocytic tumors, and the expression of LC3B-Ⅰ of grade Ⅳ tumor was statistically lower than that of grade Ⅰ, Ⅱ and Ⅲ tumors(P＜0.05). The expressions of LC3B-Ⅱ and Beclin 1 were negatively correlated to the pathological grade of the tumors (r=-0.334, P=0.007; r=-0.448, P=0.000), but positively correlated to the survival time(r=0.285, P=0.027; r=0.359, P=0.005). The expressions of LC3B-Ⅱ and Beclin 1 had a positive correlation (r=0.272, P=0.035). Conclusion Expressions of LC3B-Ⅱ and Beclin1 are down-regulated in glioblastoma multiforme; the decrease of autophagic capacity may relate to the tumorigenesis and development of astrocytic tumors. Key words: Astrocytic tumor; Glioblastoma multiforme; Autophagy; Beclin1; LC3; Survival time