| 研究実績の概要 |
We synthesized a water-soluble micellar drug called styrene maleic acid (SMA) copolymer conjugated glucosamine and boric acid (SGB-complex). It showed tumor selective accumulation based on EPR effect and excellent tumoricidal activity in vitro as well as various mouse tumor models. However, the precise chemical structure of SGB-complex and the detailed mode of action of cytotoxicity without neutron irradiation was not understood.
During FY2022 period, I focused on the determination of molecular structure of SGB-complex by UV-vis, IR, NMR spectroscopy and liquid chromatography mass spectroscopy. We confirmed that the SMA-polymer bound to the glucosamine via amide bond and the boric acid was attached to glucosamine by di-ol bond (This works we reported at ACS Applied Biomaterials journal). Next, we try to find out the possible mechanism of in vitro cytotoxicity of SGB-complex. We hypothesized that SGB-complex might induce ER or mitochondrial stress in mild-hypoxia state. To support our hypothesis, we measure the ER stress marker phosphorylated eukaryotic initiation factor 2 alpha (p-eIF2), C/-EBP homologous protein (CHOP), and Caspase 3 and 7 expressions after treating of our drug. Interestingly, we found the SGB-complex significantly increased various ER stress markers that confirmed our drug induces ER stress in hypoxia adapted cancer cells. We also measured the mitochondrial membrane potential after treatment of our drug, and data showed very less changes occurred compare to non-treated group. TEM image will be able to confirm whether any mitochondrial damage occur or not.
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| 今後の研究の推進方策 |
Currently, I am preparing chemically azoxymethane/dextran sodium sulfate (AOM/DSS) induced colon tumor in mice which mimic the clinical tumor instead of implanted xenograft tumor. I will investigate the anticancer effect of SGB-complex in the chemically induce colon tumor in combination with various nitric oxide (NO) donors.
Previously, we hypothesized that, free boric acid releases from SGB-complex at tumor tissue pH and the released boric might compete with phosphate in glycolysis pathway which inhibit the glucose-1-phosphate conversion from glucose. To support our hypothesis, we showed the SGB-complex inhibited the glucose uptake and lactate production in hypoxia adapted cancer cells, however, which step of glycolysis was inhibited was not clearly understood. Now, I am going to measure all metabolite of glycolysis after treatment with SGB-complex by means of LC-MS.
As I mention earlier, our SGB-complex very slightly change the membrane potential which is not significant compare the non-treated group. So, I would like to investigate whether any mitochondrial damage occur or not by using transmission electron microscopy (TEM). In this case, I will treat the cancer cells with SGB-complex and then the mitochondrial image will be taken by TEM.
Finally, I will prepare manuscript to submit to the journal as early as possible.
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