The Study On Synthesis And Anti-tumor Activity Of Mimics Of Manganese Superoxide Dismutase

Oberjectives:To study the synthesis and anti-tumor activity of mimics of manganese superoxide dismutase (MnSOD_m) on human leukemia cells and solid tumor cells in vitro, and to investigate the possible molecular mechanisms of MnSOD_m-mediated anti-tumor effects.Methods:According to the usual procedure of Schiff bases, one Ligand and its complexes MnSODm-1,MnSODm-2 and MnSODm-3 that have dinuclear structure were sythnsized. They measured by ES-MS spectrum, IR spectrum and X-ray analysis. Human leukemia K562 cells, human multidrug-resistant leukemia K562/ADM cells, human gastric cancer SGC7901 cells and human liver cancer HepG2 cells were used as the target cells. The cell proliferating activity was assessed with a MTT colorimetric assay. The cytomorphology was observed with optical, fluorescent and electronic microscopes, and apoptosis was explored by double staining of FITC-Annexin V and propidium iodide (PI). The expression of Bcl-2 protein and ROS level in K562/ADM cells were measured by Flow cytometry (FCM).Results:â‘ The MnSOD_m complexes was stable in solid and solution. They were easy to span through the cell membrane, and they have better water and fate solubility, low formulary weight, but have dinuclear structure .Thus, there were two active centers in one complex molecule. These complexes show high activity in anti-cancer experiments;â‘¡MnSOD_m obviously inhibited the proliferation of K562 cells, K562/ADM cells, SGC7901 cells and HepG2 cells in a manner depending on both dose and time (P<0.05). The 50% inhibitory concentration (IC₅₀) of MnSOD_m-1 (C₄₀H₆₃Cl₃ Mn₂N₆O₁₆) to K562 cells was 10.712mg/L, 1.138 mg/L and 0.618 mg/L for 24h, 48h and 72h, respectively; and to K562/ADM cells 22.410mg/L, 8.450 mg/L and 4.307mg/L; to SGC7901 cells 1.145mg/L, 2.266 mg/L and 7.388mg/L; to HepG2 cells 3.315mg/L, 12.515 mg/L and 7.235 mg/L. The IC₅₀ of MnSOD_m-2 (C₄₀H₄₈Br₄Mn₂N₆O₁₀) to K562 cells was 32.111mg/L, 1.109 mg/L and 0.587mg/L for 24h, 48h and 72h, respectively; and to K562/ADM cells 27.107mg/L, 9.051 mg/L and 4.216mg/L; to SGC7901 cells 1.139mg/L, 2.251 mg/L and 9.029mg/L; to HepG2 cells 1.682mg/L, 14.728 mg/L and 17.421mg/L. The IC₅₀ of MnSOD_m-3 (C₄₀H₅₇Mn₂N₉O₂₁)to K562 cells was 4.492mg/L, 0.815mg/L and 0.422mg/L for 24h, 48h and 72h, respectively; to K562/ADM cells 23.969mg/L, 9.966mg/L and 3.611mg/L; to SGC7901 cells 1.238mg/L, 1.767mg/L and 4.223mg/L; to HepG2 cells 4.818mg/L, 18.13mg/L and 28.786mg/L. The above results confirmed that MnSOD_m possessed the better anti-tumor activities to leukemia, gastric cancer and liver cancer cells, and the leukemia cells were the most sensitive to MnSOD_m, secondly the gastric cancer cells, and the liver cancer cells were some resistant to MnSOD_m.â‘¢After treated with MnSOD_m-3, K562/ADM cells showed the typical apoptotic morphological changes, including plasma membrane blebbing, chromatin condensation, nuclear shrinkage, and formation of apoptotic bodies. The apoptotic rate of K562/ADM cells assed with Annexin V/PI staining was greatly increased, from 3.32% to 13.91% and 55.0% after exposure to 10 mg/L and 50 mg/L MnSOD_m-3 for 48 hours. The cellular ROS level of MnSOD_m-3-treated K562/ADM cells was significantly increased from 61.0% to 95.8%and 98.6%, respectively. No significant changes of expression of Bcl-2 protein were observed in K562/ADM cells. The data indicated that the main mechanism of MnSOD_m-mediated anti-tumor effects was the induction of cellular apoptosis, and the molecular mechanism of induced apoptosis in leukemia (tumor) cells was not related with the Bcl-2 protein but associated with the production of ROS. Conclusions:The mimics of manganese superoxide dismutase with dinuclear structure were successfully synthesized. The synthesized MnSOD_m exerts a significant growth-inhibition in K562 cells, K562/ADM cells, SGC7901 cells and HepG2 cells, and possesses strong anti-tumor activities in vitro. The main mechanism of anti-tumor effects of MnSOD_m was the induction of cellular apoptosis, and the MnSOD_m-mediated apoptosis of K562/ADM cells maybe associated with the increased production of cellular ROS.