TNFRSF9 (tumor necrosis factgor receptor superfamily member 9), also called CD137 or 4-1BB, is mainly expressed on the surface of activated T, NK, and mononuclear cells. Activation of 4-1BB by its ligand CD137L or an activated CD137 monoclonal antibody provides a costimulatory signal for T cell activation. Crosslinking of CD137 enhances T cell proliferation, IL-2 secretion, survival and cytolytic activity. 4-1BB can also enhance immune activity to eliminate tumors in mice, providing a new target for tumor immunological therapies.
mRNA expression verification:
Fig 1. Molecular identification of the B-h4-1BB humanized mice. Mouse 4-1BB mRNA was detected in both the wild type and the B-h4-1BB heterozygous mice, while human 4-1BB mRNA was detected only in the B-h4-1BB heterozygous mice.
Protein expression verification:
Fig 2. Spleen cells from both wild type (WT) C57BL/6 and the B-h4-1BB homozygous mice were analyzed by flow cytometry. Mouse 4-1BB+ T cells were detected in the WT mice, while human 4-1BB+ T cells were detected in the B-h4-1BB homozygous mice.
4-1BB antibody efficacy validation:
Fig 3.Mouse colon cancer MC38 cells were subcutaneously engrafted into B-h4-1BB heterozygous mice, and animals were grouped into control and treatment groups (n=5), which include 2 antibodies and 2 doses, when the tumor size is approximately 100 mm3.
Anti-h4-1BB antibody Ab2 shows substantially inhibitory effects at both doses, while Ab1 only inhibits tumor growth at the higher dose but not lower dose. The average±SEM of tumor sizes are shown in the figure.
B-h4-1BB mouse model is a useful tool for h4-1BB antibody efficacy evaluation.