In vitro and in vivo tracer characteristics of an established multidrug-resistant human colon cancer cell line

D. E. Lorke, M. Krüger, R. Buchert, K. H. Bohuslavizki, M. Clausen, U. Schumacher

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Abstract

99mTc-methoxyisobutylisonitrile (99mTc-MIBI) has been suggested as a tracer for the scintigraphic detection of multidrug resistance (MDR). The aim of this study was to compare MDR characteristics in vitro and in vivo by immunohistochemic and functional uptake assays in established tumor cell lines cultured and grown in severe combined immunodeficient (SCID) mice. Methods: The presence of MDR was assessed in vitro in drug-resistant HT-29mdr1 colon carcinoma cells and in nonresistant HT-29par cells by JSB-1 immunohistochemistry, uptake of the fluorescent dye Rhodamine 123, and quantitative measurement of 99mTc-MIBI accumulation. For in vivo imaging, SCID mice bearing subcutaneous xenografts of these cell lines were injected with 99mTc-MIBI and 18F-FDG for scintigraphic and PET examination. After imaging, tumors were analyzed by immunohistochemistry and electron microscopy. Results: All HT-29mdr1 cells cultured in vitro exhibited distinct JSB-1 immunoreactivity, although to a variable degree, whereas HT-29par cells were completely devoid of JSB-1 staining. Rhodamine 123 accumulated poorly in HT-29mdr1 cells but strongly in HT-29par cells. Accumulation of 99mTc-MIBI was 0.05% ± 0.01% of the activity of the external medium in HT-29mdr1 cells, but about eight times higher in HT-29par cells (0.40% ± 0.09%), a very low percentage compared with other tumor cell lines. No difference in 201TlCl accumulation was observed between both cell lines. In vivo, neither HT-29par nor HT-29mdr1 tumors grown in SCID mice could be detected by 99mTc-MIBI scintigraphy. In FDG PET, both HT-29mdr1 and HT-29par tumors were clearly visible. FDG uptake was, however, markedly higher in HT-29par than in HT-29mdr1 tumors. Both tumor types were poorly vascularized, as shown histologically. JSB-1 immunoreactivity was absent in all HT-29par tumors examined, whereas the majority of HT-29par tumor cells were stained. Electron microscopy showed that HT-29par tumors contained significantly less mitochondria than hepatocytes of the SCID mouse liver, which displayed high 99mTc-MIBI uptake in our scintigraphy studies. Conclusion: Sufficient 99mTc-MIBI uptake is the major prerequisite for distinguishing successfully between drug-resistant and sensitive cells. Negative 99mTc-MIBI scintigrams are not necessarily associated with MDR expression. In some tumors, FDG may be an in vivo marker for MDR as suggested by PET.

Original languageBritish English
Pages (from-to)646-654
Number of pages9
JournalJournal of Nuclear Medicine
Volume42
Issue number4
StatePublished - 2001

Keywords

  • TlCl
  • Tc-methoxyisobutylisonitrile
  • Electron microscopy
  • FDG
  • Human HT-29 colon cancer cell line
  • Immunohistochemistry
  • Multidrug resistance
  • PET
  • Rhodamine 123
  • Severe combined immunodeficient mouse

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