Comparison of the Uptakes of 99mTc-sestamibi and 99mTc-tetrofosmin in Cancer Cell Lines Expressing Multidrug Resistance / 대한핵의학회잡지

PURPOSE: Cellular uptakes of 99mTc-sestamibi (MIBI) and 99mTc-tetrofosmin into cancer cell lines expressing multidrug resistance (MDR) were investigated and compared. The effects of verapamil and cyclosporin A, well-known multidrug resistant reversing agents, on cellular uptakes of both tracers were also compared. MATERIALS AND METHODS: Doxorubicin-resistant HCT15/CL02 human colorectal cell and doxorubicin-resistant K562 (Adr) and vincristine-resistant K562 (Vcr) human leukemic cells were studied. RT-PCR analysis was used for the detection of mdr1 mRNA expression. MDR-reversal effects with verapamil and cyclosporine A were evaluated at different drug concentrations after incubation with MIBI and tetrofosmin for 1, 15, 30, 45 and 60 min, using single-cell suspensions at 1x10 (6) cells/ml incubated at 37 degrees C. Radioactivity in supernatants and pellets were measured with gamma well counter. RESULTS: The cellular uptakes of MIBI and tetrofosmin in K562 (Adr) and K562 (Vcr) were lower than those of parental K562 cell. In HCT15/CL02 cells and K562 (Adr) cells, there were no significant difference in cellular uptakes of both tracers, but cellular uptake of MIBI was higher than that of tetrofosmin in K562 (Vcr) cells. Coincubation with verapamil resulted in a increase in cellular uptakes of MIBI and tetrofosmin. Verapamil increased cellular uptakes of MIBI and tetrofosmin by HCT15/CL02 cell by 11.9- and 6.8-fold, by K562 (Adr) cell by 14.3- and 8-fold and by K562 (Vcr) cell by 7- and 5.7-fold in maximum, respectively. Cyclosporin A increased cellular uptakes of MIBI and tetrofosmin by HCT15/CL02 cell by 10- and 2.4-fold, by K562 (Adr) cell by 44- and 13-fold and by K562 (Vcr) cell by 18.8- and 11.8-fold in maximum, respectively. CONCLUSION: Taking together, MIBI and tetrofosmin are considered as suitable radiopharmaceuticals for detecting multidrug resistance. However, MIBI seems to be a better tracer than tetrofosmin for evaluating MDR reversal effect of the modulators. Since cellular uptakes of both tracers might differ in different cell types, further experiments regarding differences in cellular uptakes between cell types should be explored.

Evaluation of Liver Function Using 99mTc-Lactosylated Serum Albumin Liver Scintigraphy in Rat with Acute Hepatic Injury Induced by Dimethylnitrosamine / 대한핵의학회잡지

OBJECTS: 99mTc-lactosylated human serum albumin (LSA) is a newly synthesized radiopharmaceutical that binds to asialoglycoprotein receptors, which are specifically presented on the hepatocyte membrane. Hepatic uptake and blood clearance of LSA were evaluated in rat with acute hepatic injury induced by dimethylnitrosamine (DMN) and results were compared with corresponding findings of liver enzyme profile and these of histologic changes. MATERIALS AND METHODS: DMN (27 mg/kg) was injected intraperitoneally in Sprague-Dawley rat to induce acute hepatic injury. At 3 (DMN-3), 8 (DMN-8), and 21 (DMN-21) days after injection of DMN, LSA injected intravenously, and dynamic images of the liver and heart were recorded for 30 minutes. Time-activity curves of the heart and liver were generated from regions of interest drawn over liver and heart area. Degree of hepatic uptake and blood clearance of LSA were evaluated with visual interpretation and semiquantitative analysis using parameters (receptor index : LHL3 and index of blood clearance : HH3), analysis of time-activity curve was also performed with curve fitting using Prism program. RESULTS: Visual assessment of LSA images revealed decreased hepatic uptake in DMN treated rat, compared to control group. In semiquantitative analysis, LHL3 was significantly lower in DMN treated rat group than control rat group (DMN-3: 0.842, DMN-8: 0.898, DMN-21: 0.91, Control: 0.96, p< 0.05), whereas HH3 was significantly higher than control rat group (DMN-3: 0.731, DMN-8: 0.654, DMN-21: 0.604, Control: 0.473, p< 0.05). AST and ALT were significantly higher in DMN-3 group than those of control group. Centrilobular necrosis and infiltration of inflammatory cells were most prominent in DMN-3 group, and were decreased over time. CONCLUSION: The degree of hepatic uptake of LSA was inversely correlated with liver transaminase and degree of histologic liver injury in rat with acute hepatic injury.

Comparison of the Uptakes of Tc-99m MIBI and Tc-99m Tetrofosmin in A549, an MRP-expressing Cancer Cell, In Vitro and In Vivo / 대한핵의학회잡지

PURPOSE: Uptakes of Tc-99m MIBI (MIBI) and Tc-99m tetrofosmin (tetrofosmin) in human non-small cell lung cancer A549, multidrug-resistance associated protein (MRP) expressing cell, were investigated in vitro and in vivo. MATERIALS AND METHODS: Western blot analysis and immunohistochemistry were used for detection of MRP in A549 cells with anti-MRPr1 antibody. Cellular uptakes of two tracers were evaluated at 100 umM of verapamil (Vrp), 50 umM of cyclosporin A (CsA) and 25 umM of butoxysulfoximide (BSO) after incubation with MIBI and tetrofosmin for 30 and 60 min at 37degrees C, using single cell suspensions at 1x10 (6) cells/ml. Radioactivities in supernatants and pellets were measured with gamma well counter. A549 cells were inoculated in each flanks of 24 nude mice. Group 1 (Gr1) and Gr3 mice were treated with only MIBI or tetrofosmin, and Gr2 and Gr4 mice were treated with 70mg/kg of CsA i.p. for 1 hour before injection of 370KBq of MIBI or tetrofosmin. Mice were sacrificed at 10, 60 and 240 min. Radioactivities of organs and tumors were expressed as percentage injected dose per gram of tissue (%ID/gm). RESULTS: Western blot analysis of the A549 cells detected expression of MRPr1 (190 kDa) and immunohistochemical staining of tumor tissue for MRPr1 revealed brownish staining in cell membrane but not P-gp. Upon incubating A549 cells for 60 min with MIBI and tetrofosmin, cellular uptake of MIBI was higher than that of tetrofosmin. Coincubation with modulators resulted in an increase in cellular uptakes of MIBI and tetrofosmin. Percentage increase of MIBI was higher than that of tetrofosmin with Vrp by 623% and 427%, CsA by 753% and 629% and BSO by 219% and 140%, respectively. There was no significant difference in tumoral uptakes of MIBI and tetrofosmin between Gr1 and Gr3. Percentage increases in MIBI (114% at 10 min, 257% at 60 min, 396% at 240 min) and tetrofosmin uptake (110% at 10 min, 205% at 60 min, 410% at 240 min) were progressively higher by the time up to 240 min with CsA. CONCLUSION: These results indicate that MIBI and tetrofosmin are suitable tracers for imaging MRP-mediated drug resistance in A549 tumors. MIBI may be a better tracer than tetrofosmin for evaluating MRP reversal effect of modulators.