Doxorubicin-conjugated anti-midkine monoclonal antibody as a potential anti-tumor drug.
BACKGROUND
Midkine is a heparin-binding growth factor preferentially expressed in tumor cells. The present study was performed to utilize anti-midkine antibody for tumor therapy.


METHODS
A monoclonal antibody to midkine was raised by immunizing mice deficient in the midkine gene. The binding site of the antibody was studied by using N-terminal half and C-terminal half of midkine, both of which were chemically synthesized. Doxorubicin (DOX)-conjugate of the antibody was produced by chemical conjugation. The effects of the antibody and the conjugate on cell growth were examined using a midkine-secreting tumor cell, i.e. human hepatocellular carcinoma cell (HepG2).


RESULTS
The monoclonal antibody bound to the N-terminal half of midkine. The antibody did not inhibit the growth of HepG2 cells probably because the active domain of midkine is in the C-terminal half. We produced the antibody conjugated with DOX with the hope that the conjugate would be internalized accompanied with midkine. Indeed, the antibody-DOX conjugate significantly inhibited the growth of HepG2 cells compared with DOX-conjugated control IgG.


CONCLUSIONS
The result raises the possibility of using anti-midkine antibody conjugated with DOX for cancer therapy.
Inoh
Kazuhiko
K
Department of Biochemistry, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
Muramatsu
Hisako
H
Torii
Shuhei
S
Ikematsu
Shinya
S
Oda
Munehiro
M
Kumai
Hideshi
H
Sakuma
Sadatoshi
S
Inui
Tatsuya
T
Kimura
Terutoshi
T
Muramatsu
Takashi
T
D000903:Antibiotics, Antineoplastic / Q000494:pharmacology* / Q000627:therapeutic use; D000911:Antibodies, Monoclonal / Q000494:pharmacology / Q000627:therapeutic use; D006528:Carcinoma, Hepatocellular / Q000473:pathology*; D002470:Cell Survival / Q000187:drug effects; D016207:Cytokines / Q000276:immunology*; D004317:Doxorubicin / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D000922:Immunotoxins / Q000494:pharmacology* / Q000627:therapeutic use; D008113:Liver Neoplasms / Q000473:pathology*; D000078792:Midkine; D014407:Tumor Cells, Cultured
D000903:Antibiotics, Antineoplastic; D000911:Antibodies, Monoclonal; D016207:Cytokines; D000922:Immunotoxins; D000078792:Midkine; D004317:Doxorubicin