Abstract
Motexafin gadolinium (MGd) is a unique therapeutic agent that localizes in cancer cells and increases tumor response to ionizing radiation and certain chemotherapeutics. The in vitro intracellular localization, accumulation, and retention of MGd in murine EMT6 mammary sarcoma and Rif-1 fibrosarcoma cell lines were studied using interferometric Fourier fluorescence microscopy. MGd cellular uptake was semiquantified using its characteristic fluorescence emission band centered at 758 nm. Colocalization studies were performed using mitochondrial, endoplasmic reticulum, Golgi apparatus, nuclear, and lysosomal fluorescent organelle probes, and verified using interferometric Fourier spectroscopy. Cellular uptake was gradual and increased significantly with incubation time. MGd localized primarily within the lysosomes and endoplasmic reticulum, and to a lesser extent within the Golgi apparatus and mitochondria. Mitochondrial staining was increased in media without serum. No nuclear uptake was detected in the Rif-1 cells, but after 48 h nuclear uptake was observed in 15% of EMT6 cells. These results indicated that MGd accumulates within cytoplasmic compartments. The sustained intracellular localization of MGd may, in part, account for its unique radiation and chemotherapy enhancement properties. Interferometric Fourier fluorescence microscopy is a potentially powerful tool in delineating and verifying localization sites of therapeutic agents.
Footnotes
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Send reprint requests to: Kathryn W. Woodburn, Ph.D., Pharmacyclics, 995 East Arques Ave., Sunnyvale, CA 94086. E-mail:KWoodburn{at}pcyc.com
- Abbreviations:
- MGd
- motexafin gadolinium
- MTG
- MitoTracker Green FM
- LTR
- LysoTracker red DND-99
- C5-ceramide
- BODIPY FL C5-ceramide
- R6
- Rhodamine B, hexyl ester, perchlorate
- HO342
- Hoechst 33342
- FBS
- fetal bovine serum
- CCD
- charge-coupled device
- FWHM
- full-width half-maximum
- Received October 20, 2000.
- Accepted February 20, 2001.
- The American Society for Pharmacology and Experimental Therapeutics
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