[Antitumor activity of new antitumor antibiotic C1027 and its monoclonal antibody assembled conjugate].
C1027, a new macromolecular peptide antitumor antibiotic produced by Streptomyces globisporus C1027, shows extremely potent cytotoxicity to cultured cancer cells. The antibiotic is composed of an apoprotein and a chromophore and the latter serves as the active part of the compound. C1027 was separated into apoprotein and chromophore by methanol extraction and the separated parts can be reconstituted to form the active C1027 molecule in phosphate buffer. For determination of the specificity of C1027 reconstitution, the apoprotein was incubated with epirubicin and the chromophore was incubated with H16, a McAb directed against hepatoma cells. Notably, the reconstitution of C1027 occurred neither between apoprotein and epirubicin nor between chromophore and IgG molecule. In addition, bovine serum albumin showed no competition with C1027 apoprotein in binding to the chromophore. Various methods for linking C1027 to McAb were studied and two kinds of immunoconjugates have been prepared: (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 degrees C in drak. Secondly, the apoprotein was conjugated to McAb by SPDP and finally the extracted chromophore was added to the McAb-apoprotein conjugate. Determined by clonogenic assay, the IC50 values for hepatoma cells were 42 pmol/L, and 5.5 pmol/L, respectively, for direct conjugate and assembled conjugate. The IC50 value of M3-C1027 assembled conjugate prepared by linking the irrelevant McAb M3 to C1027 was 1,400 pmol/L.(ABSTRACT TRUNCATED AT 250 WORDS)
Shao
R G
RG
Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences, Beijing.
Zhen
Y S
YS
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D000911:Antibodies, Monoclonal; D053281:Enediynes; D006801:Humans; D000922:Immunotoxins / Q000494:pharmacology*; D008113:Liver Neoplasms / Q000473:pathology*; D011506:Proteins / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D000903:Antibiotics, Antineoplastic; D000911:Antibodies, Monoclonal; D053281:Enediynes; D000922:Immunotoxins; D011506:Proteins; C058024:C 1027