Correlation Analysis of Apoptosis and Cell Proliferating Marker (Ki-67) in Thyroid Tumors

갑상선 종양에서 아포프토시스(Apoptosis)와 세포증식 표지자(Ki-67)의 상관관계 분석

To clarify the growth mechanisms of thyroid tumors, we investigated apoptotic cells in 88 thyroid tumors, consisting of 24 adenomas, 58 papillary thyroid carcinomas, and 6 undifferentiated carcinoma, using terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate digoxigenin-nick end labeling (TUNEL). The cell proliferating marker was also evaluated immunohistochemically using the monoclonal antibody to Ki-67 antigen (MIB-1) in the same tumors. The apoptosis was expressed as a percentage of the TUNEL-positive cells in the tumor cells, and a proliferating marker, being the percentage of Ki-67 positive cells, was counted up each tumor. The statistical analysis were used analysis of variance (ANOVA) and student's t-test that were analyze the differences in the rate of each histological types of the thyroid tumors. The overall level of apoptosis was extremely low in all histological types of the thyroid tumors analyzed, the mean apoptosis being $0.31{\pm}0.40$ in adenoma, $0.55{\pm}0.48 $in papillary thyroid carcinoma, and $4.60{\pm}3.27$ in undifferentiated carcinoma. The Ki-67 protein in the thyroid tumor subtypes was significantly lower in adenoma and papillary carcinoma, at $2.45{\pm}2.99$ and $6.27{\pm}4.42$, respectively, than that in undifferentiated carcinoma at $26.47{\pm}23.88$ (p<0.0001). There was no correlation between clinicopathological factors and apoptosis or Ki-67 in papillary thyroid carcinoma. In conclusion, our findings suggest that apoptosis occurs infrequently in thyroid tumor, and that cell proliferating maker Ki-67 markedly differs according to the thyroid tumor subtypes. Moreover, the ratio between proliferating cells and apoptotic cells may reflect thyroid tumor progression.