Objective: To explore the presence of MDR-1 drug resistance in human glioma utilizing a Single Photon Emission Computerized Tomography (SPECT) imaging agent, sesta-MIBI, and testing cases interpreted as positive for drug resistance with molecular characterization of subsequent tissue biopsy, including RNA, Northern blot analysis, and polymerase chain reaction, and in situ hybridization.
Methods: Six patients that carried a diagnosis of biopsy-proven glioma underwent dual isotope SPECT imaging with thallium 201 and technetium sesta-MIBI. All six patients underwent subsequent surgical reexcision of their tumors, and tissue was immediately flash frozen for further analysis. PolyA RNA was isolated and subsequently analyzed by both Northern blot analysis and RT-PCR utilizing an MDR-1 probe (ATCC) and MDR-1 primers.
Results: Four patients with SPECT concordance yielded tumors without MDR-1 expression whereas two patients with SPECT discordance yielded tumors with MDR-1 gene expression. In one discordant case we subsequently performed RT-PCR in situ amplification/ hybridisation and immunohistochemistry with, respectively, an MDR-1 sense primer with Biotin labeled probes and an MDR-1 monoclonal antibody, and both analyses revealed MDR-1 expression in tumor cells.
Conclusion: These data support the use of SPECT technetium sesta-MIBI to evaluate the presence of MDR-1 gene expression in gliomas.