| Abstract
| - Endostatin can specifically inhibit endothelial proliferation and potently inhibit angiogenesis and tumor growth.N-Terminal site-specific mono-PEGylation of recombinant human endostatin (mPEG-rhES) was accomplishedby using methoxy poly-ethylene glycol (mPEG) propionaldehyde with an average molecular weight of 5000 Dathrough a reactive terminal aldehyde group. The site-specific mPEG conjugation was conducted under optimalconditions, which were identified through a statistical L9(34) orthogonal test. In this study, we have investigatedthe stability and antitumor activity of mPEG-rhES. SDS−PAGE, RP-HPLC, and UV spectrophotometric analysiswere used to identify the purity and stability of mPEG-rhES. When incubated with protease or placed in anextreme environment, mPEG-rhES was more stable than rhES. The unmodified and PEGylated rhES were testedfor their ability to inhibit the tumor growth of mouse H22 liver cancer in male mice. In a multiple versus singledoses comparison study, daily administration of 0.25, 0.50, and 1.00 μmol/kg of unmodified rhES for 7 daysresulted in 26.9%, 43.0%, and 64.9% reductions in tumor weight, respectively, while single doses of 0.13, 0.25,and 0.50 μmol/kg of the PEGylated protein per day resulted in 24.8%, 38.0%, and 64.5% reductions, respectively.Both treatments resulted in statistically significant reductions in mean tumor weight as compared to the physiologicalsaline solution (control)-treated mice, with the dose of mPEG-rhES being a half of rhES, respectively, while thetumor inhibition rates were similar. Therefore, it is suggested that PEGylation enhances the stability of rhES andimproves its antitumor activity.
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