title: Anti-human CD73 monoclonal antibody inhibits metastasis formation in human breast cancer by inducing clustering and internalization of CD73 expressed on the surface of cancer cells.
abstract: Recent studies have shown that Abs that target the cell-surface enzyme CD73 (ecto-5'-nucleotidase) reduce growth of primary tumors and metastasis in syngenic mice by inhibiting the catalytic activity of CD73, and thus increasing the activity of cytotoxic T lymphocytes. In this article, we report another anticancer mechanism of anti-CD73 Abs and show that an anti-CD73 mAb (AD2) inhibits metastasis formation by a mechanism independent of CD73 catalytic activity and inhibition of primary tumor growth. This mechanism involves clustering and internalization of CD73, but does not require cross-linking of CD73, because both whole IgG anti-CD73 AD2 mAb and Fab' fragments thereof exhibited this effect. Ex vivo treatment of different breast cancer cell lines with anti-CD73 AD2 mAb before i.v. injection into mice inhibited extravasation/colonization of circulating tumor cells and significantly reduced metastasis development. This effect was also observed when the cancer cell-surface expression of CD73 was significantly reduced by small interfering RNA knockdown. The antimetastatic activity is epitope specific, as another Ab that efficiently binds CD73-expressing live cancer cells did not lead to CD73 internalization and metastasis inhibition. Furthermore, anti-CD73 AD2 mAb inhibited development of metastasis in a spontaneous animal model of human metastatic breast cancer. Our study shows that some anti-CD73 mAbs cause cell-surface clustering of CD73 followed by internalization, thus inhibiting the ability of circulating tumor cells to extravasate and colonize, leading to inhibition of metastasis. Ab-based CD73 cancer therapy should include a combination of Abs that target the catalytic activity of CD73, as well as those with the characteristics described in this article.
authors.affiliation: Department of Cancer and Inflammation Research, Institute of Molecular Medicine, University of Southern Denmark, DK-5000 Odense C, Denmark;
authors.forename: Mikkel G
authors.initials: MG
authors.lastname: Terp
authors.forename: Kristina A
authors.initials: KA
authors.lastname: Olesen
authors.forename: Eva C
authors.initials: EC
authors.lastname: Arnspang
authors.forename: Rikke R
authors.initials: RR
authors.lastname: Lund
authors.forename: B Christoffer
authors.initials: BC
authors.lastname: Lagerholm
authors.forename: Henrik J
authors.initials: HJ
authors.lastname: Ditzel
authors.forename: Rikke
authors.initials: R
authors.lastname: Leth-Larsen
mesh_terms: D015720:5'-Nucleotidase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D001692:Biological Transport; D001943:Breast Neoplasms / Q000276:immunology / Q000628:therapy*; D045744:Cell Line, Tumor; D002465:Cell Movement; D005260:Female; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D051379:Mice; D009362:Neoplasm Metastasis / Q000276:immunology / Q000517:prevention & control*; D009368:Neoplasm Transplantation; D009360:Neoplastic Cells, Circulating; D034622:RNA Interference; D034741:RNA, Small Interfering; D023041:Xenograft Model Antitumor Assays
chemical_list: D000911:Antibodies, Monoclonal; D007140:Immunoglobulin Fab Fragments; D034741:RNA, Small Interfering; D015720:5'-Nucleotidase