新抗癌抗生素C1027及其单克隆抗体组装偶联物的抗肿瘤活性

ANTITUMOR ACTIVITY OF NEW ANTITUMOR ANTIBIOTIC C1027 AND ITS MONOCLONAL ANTIBODY ASSEMBLED CONJUGATE

C1027是链霉菌株产生的大分子肽类新抗癌抗生素,对肿瘤细胞具有显著的杀伤作用,它由一条肽链和一个发色团组成,后者是主要活性部分。本研究用甲醇拆分C1027并重新组建,重建的C1027与天然C1027活性相似;C1027的重建是特异的,肽链与发色团的结合不受BSA竟争影响。肽链不能与表阿霉素组建;单抗H16(IgG_1)不能与发色团组建。我们用不同的方法分别制备了C1027与抗人肝癌单抗H16直接偶联物和组装偶联物(单抗与肽链连接后再加入发色团);克隆形成测定,前者IC_(50)为42pmol·L^(-1),后者为5.5pmol·L^(-1);C1027与无关抗体M3组装偶联物的IC_(50)为240pmol·L^(-1)。结果表明H16-C1027组装偶联物对肝癌细胞的抑制作用比直接偶联物明显增强,并具有选择性杀伤作用。

C1027, a new macromolecular peptide antitumor antibiotic producedby Streptomyces globisporus C1027, shows extremely potent cytotoxicity to cultured cancercells. The antibiotic is composed of an apoprotein and a chromophore and the latter servesas the active part of the compound. C1027 was separated into apoprotein andchromophore by methanol extraction and the separated parts can be reconstituted to formthe active C1027 molecule in phosphate buffer. For determiation of the specificity ofC1027 reconstitution, the apoprotein was incubated with epirubicin and the chromophorewas incubated with H16, a McAb directed against hepatoma cells. Notably, thereconstitution of C1027 occurred neither between apoprotein and epirubicin nor betweenchromophore and IgG molecule. In addition, bovine serum albumin showed no competi-tion with C1027 apoprotein in binding to the chromophore. Various methods for linkingC1027 to McAb were studied and two kinds of immunoconjugates have been preparted: (1)direct conjugate was made by linking C1027 to McAb, using SPDP as a linker agent, (2)assembled conjugate was made by linking and reconstitution, including 3 steps. Firstly,the chromophore was extracted with methanol and stored at-70°C in drak. Secondly, theapoprotein was conjugated to McAb by SPDP and finally the extracted chromophore wasadded to the McAb-apoprotein conjugate. Determined by clonogenic assay, the IC_(50)valuesfor hopatoma cells were 42 pmol/L, and 5. 5 pmol/L, respectively, for direct conjugate andassembled conjugate. The IC_(50) value of M3-MC1027 assembled conjugate prepared bylinking the irrelevant McAb M3 to C1027 was 1 400 pmol/L. The results indicate that thecytotoxicity of assembled conjugate is much stronger than that of direct conjugate and thatH16-C1027 assembled conjugate showed highly selective effect on hepatoma cells.