Expression of multidrug resistance protein and messenger RNA correlate with Tc-99m-MIBI imaging in patients with lung cancer

In vitro studies have shown that Tc-99m-sestamibi (MIBI) is a transport sub strate for the P-glycoprotein (Pgp) pump and the multidrug resistance-assoc iated protein (MRP) pump. However, whether MRP and lung resistance protein (LRP) affect tumor accumulation and efflux of Tc-99m-MIBI in lung cancer is not known. In this study, we explored whether Pgp and the other pumps, MRP and LRP, affect tumor accumulation and efflux of 99mTc-MIBI in lung cancer . Methods: Thirty-four lung cancer patients who underwent surgery were exam ined. Before surgery, 99mTc-MIBI SPECT was performed 15 min and 180 min aft er injection, and early uptake, delayed uptake (L/Nd), and washout rate (L/ Nwr) of Tc-99m-MIBI were obtained. Pgp, MRP, and LRP expression were invest igated by immunohistochemistry. The messenger RNA (mRNA) level of Pgp, MRP, and LRP was determined by real-time reverse-transcription polymerase chain reaction. The lung cancer Tc-99m-MIBI images were correlated with protein and mRNA expression. Results: The mean L/Nd of the Pgp (-) group was signif icantly higher than that of the Pgp (+ +) group (P = 0.0324). The Pgp (+ +) group had a higher L/Nwr than did the Pgp (-) group (P = 0.0269). The mean L/Nd of the Pgp mRNA low-expression group was significantly higher than th at of the Pgp mRNA high-expression group (P = 0.0127). The Pgp mRNA high-ex pression group had a higher L/Nwr than did the Pgp mRNA low-expression grou p (P = 0.0825). No appreciable correlation was found between the lung cance r 99mTc-MIBI images and the expression of MRP or LRP on the level of protei n or mRNA. Conclusion: These data suggest that an increased level of Pgp ex pression correlates with a low accumulation on delayed scans and a high L/N wr of Tc-99m-MIBI in lung cancer. Neither MRP nor LRP expression on the lev el of either protein or mRNA correlated significantly with tumor accumulati on or efflux of Tc-99m-MIBI in lung cancer.