Midkine and LDL-receptor-related protein 1 contribute to the anchorage-independent cell growth of cancer cells.
The growth factor midkine (MK) is highly associated with cancer progression. Knockdown of MK expression strikingly suppresses tumor growth in nude mice. Thus, MK is a candidate target for cancer treatment. LDL-receptor-related protein 1 (LRP1) is a receptor for MK. We found that among the four ligand-binding domains of LRP1, the N-terminal half of the second domain (designated as MK-TRAP) had the strongest affinity to MK. MK-TRAP bound to MK, but not to HB-GAM/pleiotrophin, basic fibroblast growth factor or platelet-derived growth factor (PDGF)-BB. Exogenous MK-TRAP inhibited the binding between MK and LRP1. G401 cells that transiently or stably overexpress MK-TRAP showed decreased cell growth in monolayer culture and reduced colony formation in soft agar, which could be rescued by exogenous MK administration. MK-TRAP collected from conditioned medium also inhibited anchorage-independent growth of G401 cells and CMT-93 cells. Anti-MK antibody also inhibited the anchorage-independent growth. CMT-93 cells stably expressing MK-TRAP formed smaller tumors in a xenograft nude mouse model than control cells. Moreover, GST-RAP, a potent inhibitor of LRP1, inhibited the anchorage-independent growth of control G401 cells but not that of MK-TRAP stable transformants. Collectively, these data demonstrate a crucial role of MK-LRP1 signaling in anchorage-independent cell growth.
Chen
Sen
S
Department of Biochemistry, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
Bu
Guojun
G
Takei
Yoshifumi
Y
Sakamoto
Kazuma
K
Ikematsu
Shinya
S
Muramatsu
Takashi
T
Kadomatsu
Kenji
K
D000818:Animals; D016466:CHO Cells; D019556:COS Cells; D002448:Cell Adhesion; D016923:Cell Death; D049109:Cell Proliferation; D002522:Chlorocebus aethiops; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D008024:Ligands; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D000078792:Midkine; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000473:pathology*; D009414:Nerve Growth Factors / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D014410:Tumor Stem Cell Assay
D008024:Ligands; D026503:Low Density Lipoprotein Receptor-Related Protein-1; C066254:MDK protein, human; D009414:Nerve Growth Factors; D000078792:Midkine