| Summary: | 博士 === 國立清華大學 === 化學系 === 98 === BMVC, 3,6-bis(1-methyl-4-vinylpyridinium)carbazole diiodide, is a novel organic molecule with special tumor recognition characteristic. BMVC appears bright fluorescence in the nucleus of cancer cells while only weak fluorescence in the cytoplasm of normal cells. The strong fluorescence of BMVC in the nucleus is mainly due to significant enhancement of BMVC fluorescence upon binding to DNA. Therefore, distinct properties of BMVC in cells allow us to differentiate cancer cells from normal cells. We further apply BMVC as a potential fluorescent tumor marker for clinical cancer diagnosis1,2.
It is of interest to elucidate the reason why BMVC can act as a potential fluorescence tumor marker. Confocal microscopic images by merging with organelle trackers suggested that BMVC mainly localizes in the nucleus and mitochondria of cancer cells, but in the lysosome of normal cells. Several leading experiments suggested that the major pathway for BMVC uptake is endocytosis. In addition, the carbonyl-cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) and microinjection experiments showed that the endocytosed BMVC is trapped in the lysosome of normal cells. However, it is not clear why BMVC is not trapped in the lysosome of cancer cells. Recently, it is suggested that the lysosomal membrane permeabilization (LMP) is highly related to cell death and cancer3. We performed the cathepsin immunofluorescence and vacuolization experiments to elucidate whether there is lysosomal membrane permeability difference between cancer and normal cells. Our results suggested that the lysosomal membrane permeability difference is likely the mechanism for trapping BMVC in the lysosome of normal cells, but releasing BMVC to the nucleus and mitochondria of cancer cells.
Furthermore, the structure localization relationship (SLR) studies show that BMVC derivatives with large hydrogen bonding capacity (HBC) are less lysosomal membrane permeable in normal cells. In addition, we found that the more lipophilic of BMVC derivatives the more mitochondria localization in cancer cells. It is likely that the HBC and the lipophilicity are two important characters in determining intracellular localization of BMVC derivatives in cells. These findings may allow us to design better fluorescent tumor markers in cancer diagnosis.
Finally, BMVC-porphyrin binary system (o-2B-P) was designed according to the idea of “cancer selective” therapy. The 450-500 nm transparent windows of porphyrin derivatives allow us to perform irradiation wavelength selectivity for photodynamic therapy (PDT). Moreover, the cell images showed that o-2B-P appeared red fluorescence in the cytoplasm before irradiation but became green-yellow fluorescence in the nucleus after light irradiation. This photoinduced translocation is further assigned as the results of PDT effect. Of particular interest is the time-lag of the photo-induced translocation of o-2B-P between cancer cells and normal cells, implying that the o-2B-P may achieve the ideal PDT treatment, which kills the cancer cells without dramatic side effects on normal cells.
In summary, this research begins with application of BMVC as a potential fluorescent tumor marker. The confocal microscopy studies suggested that BMVC mainly localizes in the nucleus and mitochondria of cancer cells, but in the lysosome of normal cells. Further studies showed that this localization difference may be due to the different lysosomal membrane permeability of BMVC between cancer and normal cells. Accordingly, the lysosomal membrane permeabilization difference to small molecules between cancer and normal cells could be applied as a new target for developing probes in cancer diagnosis or drugs in selective cancer therapy. Furthermore, several BMVC derivatives were synthesized for better fluorescent tumor markers. During the screening, different cellular responses from different BMVC derivatives illustrated the importance of lipophilicity and HBC for the intracellular localization of drugs. It further suggested that one can modify these chemical properties of a small molecule for manipulating its intracellular localization. Finally, o-2B-P, provided a new platform for cancer selective drug through the combination of a cancer targeting molecule and anticancer drug.
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