Using 99Tcm-MIBI to evaluate tumor multidrug resistance and monitor the reversring of chemosensitizer

Objective: To study the correlation between, uptake of 99Tcm-MIBI and multidrug-resistant P-glycoprotein and evaluate the effect of chemosensitizer. Methods: Tumor bearing mice models were established by inplanting human cancer cell line MCF-7/Adr, the mice were randomized into two groups: chemosensitizer verapamil group and control. Before and after giving verapamil, 99Tcm-MIBI scintigraphy were performed at 15 min, 60 min, 90 min, 120 min, respectively. Mice Were sacrificed after scintigraphy to get %ID/g of tumor and major organs. The level of P-gp were measured with immunocytochemical assay and mRNA of mdrl gene determined with RT-PCR were obtained simultaneously. Results: After giving verapamil the T/N ratio of tumor increased significantly except 120 min scintigraphy.The 99Tcm-MIBI uptake difference between the verapamil group and controls was obvious (P value were 0.045, 0.015, 0.042, respectively ). The expression of mdrl mRNA decreased dramastically after verapamil reversing (t=4.873, P=0.008). The level of P-gp declined from 0.1038±0.0078 to 0.0096±0.0059 (t=3.579, P=0.023). The 99Tcm-MIBI uptake of tumor, liver and kidney rose obviously after reversing, %ID/g increaments were 106.83%, 40.35%, 166.07% respectively, whereas it was slightly declined by -12.82% in heart . Conclusions: 99Tcm-MIBI scintigraphy may evaluate MDR mediated by P-gp and potentialy be used to monitor the reversing effect of chemosensitizer in P-gp positive tumors. (authors)