OBJECTIVETo prepare 99Tcm-annexinV and evaluate its application in the early prediction of therapeutic effect of chemical agent on lung cancer.

METHODSAnnexin V was obtained by recombinant pichia pastoris expression, ammonium sulfate precipitation, and size-exclusion chromatography. The purified protein was labeled with 99Tc(m) at the N-terminal site by stannous chloride reduction and purified by desalting. The labeling yield and radiochemical purity of 99Tc(m)-annexinV were determined by instant thin-layer chromatography. The biological activity of 99Tc(m)-annexinV was tested by phosphatidylserine-exposed erythrocytes bound radioactivity counting. The lung cancer mice models were established by inoculating LA795 cells to right flank of 615 mice subcutaneously and tumor tissue transplantation. The biodistribution of 99Tc(m)-annexinV in lung cancer mice models were investigated at 6, 12, 24, and 48 h after cyclophosphamide administration.

RESULTSThe annexin V was secreted from pichia pastoris and purified by ammonium sulfate precipitation and size-exclusion chromatography with high yield. The annexin V could be labeled at room temperature with 50.2% radioactivity yield. The radiochemical purity of 99Tc(m)-annexinV reached up to 93.9% with intact biological activity. The biodistribution analysis demonstrated that 99Tc(m)-annexinV was excreted from kidney. The uptake of 99Tc(m)-annexinV at tumor reached maximum 48 h after cyclophosphamide administration while tumor to muscle ratio was 6.34 and tumor to blood ratio was 4.09.

CONCLUSIONS99Tc(m)-annexinV derived from pichia pastoris was successfully prepared. It is useful in predicting the therapeutic effect of chemical agent on lung cancer.