Overexpression of LC3 in Papillary Thyroid Carcinomas and Lymph Node Metastases

Abstract

Background : Autophagy is believed to be important in tumorigenesis and tumor progression. An antibody to the microtubule-associated protein 1 light chain 3 (LC3), the mammalian homologue of yeast Atg8, recognizing both the soluble (LC3-I) and the membrane-bound form (LC3-II) of the protein, is involved in autophagosome formation during autophagy. The aim of this study was to investigate LC3 expression in papillary thyroid carcinoma (PTC) to elucidate the role of autophagy in human cancer development.Methods : We investigated the expression of LC3 in human PTC. Tissue samples from 86 cases of papillary thyroid carcinoma were used for the present study. 57 cases of papillary thyroid carcinoma were with lymph node metastasis. The expression of LC3 in tumor, normal tissue adjacent to tumor, distant normal tissue, metastatic lymph node and normal lymph node was examined with immunohistochemistry. The LC3 expression between tumor and normal tissue, metastatic and normal lymph node was also analyzed.Results : The expression of LC3 was detected in 90.7% (78/86) of the tumors and 96.5% (55/57) of metastatic lymph nodes. In contrast, normal tissues adjacent to tumor, distant normal tissues and normal lymph nodes showed no or very weak expression of LC3. LC3 was significantly correlated with tumorigenesis and lymph node metastasis in human PTC. Conclusions: High expression of LC3 in PTC and metastatic lymph node suggest that Autophagy may play a role in tumorigenesis and lymph node metastasis in human PTC.