Preparation and In Vitro Evaluation of 131I-BmK CT as a Glioma-Targeted Agent

Objective: Buthus martensi Karsch (BmK) CT, a kind of scorpion toxin peptide, was found to inhibit glioma cell proliferation in previous researches. I-131-BmK CT may have more inhibition effect and could be used as a glioma cell-targeted therapy and imaging agent. The purpose of this study was to investigate whether I-131-BmK CT could specifically conjugate with C6 glioma cell and induce glioma cell inhibition in vitro. Methods: After cloning, expression, and purification, BmK CT was labeled with I-131 by indirect labeling (Bolton-Hunter method). The cell conjugation experiment was performed to investigate the connection between the reciprocal of cell conjugation rate and the reciprocal of cell count. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) method and flow cytometry were used to detect the inhibition effect of BmK CT and I-131-BmK CT on glioma cell proliferation. Results: I-131-BmK CT was successfully prepared with the overall yield of 34.5%. The cell conjugation experiment indicated that I-131-BmK CT could specifically conjugate with C6 cells. MTT tests indicated that both BmK CT and I-131-BmK CT could inhibit C6 growth. The ability of I-131-BmK CT to inhibit cell growth is superior to that of BmK CT. The inhibitory rate (IR) of glioma cells was 60.5% (p < 0.01) at the concentration of 2 mu g/mL with BmK CT. And the IR was 71.2% (p < 0.01) at the radioactivity concentration of 50 mu Ci/mL (concentration was much lower than 2 mu g/mL) with I-131-BmK CT. BmK CT could block the C6 glioma cell cycle in the G0/G1 stage. I-131-BmK CT blocked the cell cycle in the S stage (the proportions of C6 in the S, G0/G1, and G2/M phases were 24.5% +/- 0.4% vs. 44.0% +/- 2.3%, 63.9% +/- 0.6% vs. 51.8% +/- 1.6%, and 11.6% +/- 1.0% vs. 4.3 +/- 0.7% [p < 0.05], respectively, at an initial radioactivity concentration of 50 mu Ci/mL). Conclusions: On the basis of cytology experiments, it was found that I-131-BmK CT could specifically conjugate with C6 glioma cell and inhibit cell growth. Hence, it may be used as a glioma-targeted agent.