목적: 종양세포에서 F-18-FDG 섭취 기전을 규명하기 위하여 F-18-FDG 섭취와 포도당운반체-1 (Glut-1), hexokinase의 발현과의 상관관계를 조사하였다. 대상 및 방법: 사람의 대장암(SNU-C2A, SNU-C4, SNU-C5), 간암(SNU-387, SNU-423, SNU-449), 폐암(NCI-H522, NCI-H358, NCI-H1299), 자궁경부암(HeLa, HeLa 229, HeLa S3), 그리고 뇌암(A172, Hs 683)에서 기원한 암 세포주 $5{ imes}10^5$ 세포를 24 well plate에 24시간 배양하였다. 여기에 37 kBq의 F-18-FDG를 첨가한 후 각 세포의 섭취 정도를 감마 카운터를 사용하여 측정하였다. Hexokinase의 활성은 분광광도계를 사용하여 측정하였다. 디토콘드리아에서의 hexokinase 활성은 고속원심분리기를 이용하여 미토콘드리아 분획을 분리하여 조사하였다. Glut-1의 발현은 면역조직염색법으로 측정하였다. 결과: 종양세포의 종류에 따라 F-18-FDG 섭취, 전체 그리고 미토콘드리아 hexokinase 활성, 그리고 Glut-1의 발현 정도에 차이가 있었다. 종양세포주에서 F-18-FDG 섭취와 세포전체, 세포내 미토콘드리아 hexokinase 활성과의 상관관계(각각 r=0.27, r=0.26)는 낮게 나타났으며, Glut-1의 발현은 F-18-FDG의 섭취와 상관관계(p=0.81, p=0.0015)가 높았다. 대장암 세포주에서 F-18-FDG 섭취와 hexokinase 활성의 상관관계가 없다는 보고를 토대로 대장암 세포주 결과를 제외했을 경우에 F-18-FDG의 섭취와 세포전체 그리고 세포내 미토콘드리아에서의 hexokinase 활성과는 높은 상관관계(각각 r=0.81, p=0.0027, 그리고 r=0.81, p=0.0049)를 보였다. 결론: Glut-1이나 hexokinase 활성이 사람 종양 세포주에서 F-18-FDG의 섭취를 결정하는 주 요인이며, 종양세포의 종류에 따라 이들의 기여도는 서로 다름을 알 수 있었다.
Purpose: To investigate the mechanisms related to F-18-FDG uptake by tumors, F-18-FDG accumulation was compared with glucose transporter-1 (Glut-1) expression and hexokinase activity in various human cancer cell lines. Materials and Methods: Human colon cancer (SNU-C2A, SNU-C4, SNU-C5), hepatocellular carcinoma (SNU-387, SNU-423, SNU-449), lung cancer (NCI-H522, NCI-H358, NCI-H1299), uterine cervical cancer (HeLa, HeLa 229, HeLa S3) and brain tumor (A172, Hs 683) cell lines were used. After 24 hr incubation of $5{ imes}10^5$ cells, 37 kBq F-18-FDG was added and the uptake by cells at 10 min was measured using a gamma counter. Hexokinase activity was measured by continuous spectrophotometric rate determination. To measure mitochondrial hexokinase activity, mitochondrial fraction was separated by a high speed centrifuge. Immunohistochemical staining of Glut-1 was performed, and graded as 0, 1, 2, or 3 according to expression. Results: There was difference among F-18-FDG uptake, total and mitochondrial hexokinase activity, and Glut-1 expression with different cancer cell lines. The correlations of F-18-FDG with total hexokinase and mitochondrial hexokinase activity were low (r=0.27 and 0.26, respectively). Glut-1 expression showed a good correlation with F-18-FDG uptake (p=0.81, p=0.0015). Previously, we reported no correlation of F-18-FDG uptake with hexokinase activity in colon cancer cell lines. Thus, when colon cancer cells were excluded, F-18-FDG uptake showed higher correlation with total hexokinase and mitochondrial hexokinase activity (r=0.81, p=0.0027 and r=0.81, p=0.0049, respectively). Conclusion: Both Glut-1 expression and hexokinase activity were contributing factors related to F-18-FDG accumulation in human cancer cell lines. The relative contribution of Glut-1 expression and hexokinase activity, however, was different among different cancer cell types.
