平阳霉素与单克隆抗体Fab′片段偶联物的抗肿瘤作用

ANTITUMOR EFFECTS OF PINGYANGMYCIN CONJUGATED WITH Fab′ FRAGMENT OF MONOCLONAL ANTIBODY

目的 研制一种以单抗Fab′片段为基础的抗肿瘤导向药物。方法 制备单抗 3A5Fab′片段及其与平阳霉素 (PYM )偶联物Fab′ PYM后 ,测定Fab′ PYM与肿瘤细胞的免疫反应性、偶联物中PYM的抑菌活性、对肿瘤细胞的杀伤作用和体内抑瘤作用。结果 Fab′及Fab′ PYM保持了与靶细胞C2 6的免疫反应性 ;偶联物中PYM的抑菌活性为游离PYM的 15 % ;Fab′ PYM对C2 6细胞的杀伤作用强于PYM ;对非靶细胞KB的杀伤作用与PYM相似 ;ip和iv给药 ,Fab′ PYM对小鼠皮下接种的肠癌 2 6生长抑制作用均强于 3A5 PYM和PYM。结论 Fab′ PYM具有比PYM及 3A5

AIM To develop an immunoconjugate with targeting antitumor effects by linking the Fab′ fragment of McAb to pingyangmycin (PYM). METHODS McAb 3A5 was digested with pepsin to obtain Fab′ fragment. Linking between Fab′ and PYM was mediated by dextran T 40. Immunoreactivity of Fab′ was determined by ELISA. Bacteria inhibitory activity of the conjugate was determined by TTC assay. Cytotoxicity to carcinoma cells was determined by MTT assay and antitumor effects in vivo were assessed in BALB/c mice transplanted with colon carcinoma 26(C26). RESULTS The Fab′ PYM conjugate retained immunoreactivity with C26 cells, the target cells. The IC 50 values of Fab′ PYM and PYM to C26 cells were 2 51 μg·mL -1 and 32 46 μg·mL -1 , respectively. Fab′ PYM and PYM displayed similar cytotoxicity to KB cells,the non target cells. By intraperitoneal dose of 5 mg·kg -1 ×6, Fab′ PYM and PYM suppressed the growth of colon carcinoma 26 by 77% and 56%, respectively. By intravenous dose of 5 mg·kg -1 ×7, Fab′ PYM, 3A5 PYM and PYM inhibited the growth of colon carcinoma 26 by 89%, 73% and 70%, respectively. Fab′ PYM was found to be more effective against target tumor than 3A5 PYM and PYM ( P <0 01). With higher tolerable dose of 10 mg·kg -1 ×7 , iv, the inhibition of tumor growth by Fab′ PYM reached 91%. CONCLUSION Fab′ PYM conjugate characterized by smaller size of the molecule displayed higher antitumor effects than 3A5 PYM and free PYM.