Terp, Mikkel G7; Olesen, Kristina A7; Christensen, Eva Arnspang8; Lund, Rikke R7; Lagerholm, B Christoffer9; Ditzel, Henrik J7; Leth-Larsen, Rikke10
1 Ditzel group, Department of Molecular Medicine, Det Sundhedsvidenskabelige Fakultet, SDU2 Department of Physics, Chemistry and Pharmacy, Faculty of Science, SDU3 MEMPHYS Center, Department of Physics, Chemistry and Pharmacy, Faculty of Science, SDU4 Oncology, Department of Clinical Research, Det Sundhedsvidenskabelige Fakultet, SDU5 Institute of Chemical Engineering, Biotechnology and Environmental Technology, Faculty of Engineering, SDU6 Institute of Regional Health Research, Det Sundhedsvidenskabelige Fakultet, SDU7 Ditzel group, Department of Molecular Medicine, Det Sundhedsvidenskabelige Fakultet, SDU8 Institute of Chemical Engineering, Biotechnology and Environmental Technology, Faculty of Engineering, SDU9 Department of Physics, Chemistry and Pharmacy, Faculty of Science, SDU10 Institute of Regional Health Research, Det Sundhedsvidenskabelige Fakultet, SDU
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.
Journal of Immunology, 2013, Vol 191, Issue 8, p. 4165-4173
5'-Nucleotidase; Animals; Antibodies, Monoclonal; Biological Transport; Breast Neoplasms; Cell Line, Tumor; Cell Movement; Female; Humans; Immunoglobulin Fab Fragments; Mice; Neoplasm Metastasis; Neoplasm Transplantation; Neoplastic Cells, Circulating; RNA Interference; RNA, Small Interfering; Xenograft Model Antitumor Assays