Experimental Study Of Somatostatin Receptor Imaging In Small Cell Lung Cancer With ～(99m)Tc-octreotide

Objective: To investigate the expression of somatostatin receptor 2subtype in the cell line of NCI-H446 and the biodistribution of ^99mTc-octreotide in normal and the human small cell lung cancer (sclc) bearing nude mice.Methods: (1)Immunofluorescence and electron microscopic autoradiography(EM-ARG) were used to detect the expression and distribution of somatostatin receptor 2 subtype in NCI-H446 cells. (2)Dynamic and static scintigraphy at 0.5h, 2h, 3h, 4h, 6h,24h were performed in both normal and tumor bearing nude mice after intravenous injection of 16.8MBq ^99mTc-octreotide. The technique of drawing region of interest (ROI) was used to obtain the averaged pixel counts and the activity-time (A-T) curve of brain, heart, lung, liver, kidney, tumor, respectively.Results: (1)Specific fluorescence was observed in all of the cell samples aswell as in the majority of normal lung tissue of nude mice. The positive rate of somatostatin receptor 2 in the cell line of NCI-H446 and normal lung tissue of nude mice is 100% , 93.7% .respectively (X²=0.0036, p>0.05);the intensive positive rate is 61.1%å’Œ 20% respectively (X²=5.6613, p<0.05). (2) Sliver grains were clearly detected in the membrane of group Al and in the nucleolus and cytoplasm of group Bl.The number of sliver grains in the cells of A2 and B2 groups was obviously less than group Al and Bl.(3) The biodistribution study in normal nude mice showed high uptake in kidney and liver, low in lung, heart and brain . Most ^99mTc-octreotide was excreted via kidney. ? All tumors were displayed clearly at 3h postinjection of ^99mTc-octreotide . The averaged T/N ratio at 0.5h, 2h, 3h, 4h postinjection of ^99mTc-octreotide were 1.163±0.03, 2.08±0.12, 3.03±0.23 2.689±0.31, respectively(F=51.69 ,P<0.0001) . The radioactivity of tumor was lower than liver, and similar with the lung . The curve of tumor showed a radioactivity peak at 2³min postinjection.Conclusions: Somatostatin receptor 2 subtype was expressed in NCI-H446 cells with high concentrations. 99mTc-octreotide may well be a promising imaging agent in the diagnosis of sclc.