A novel monoclonal antibody against mouse B7-H3 developed in rats

Preclinical assessment of the efficacy and specificity of GD2-B7H3 SynNotch CAR-T in metastatic neuroblastoma

The ability to utilize preclinical models to predict the clinical toxicity of chimeric antigen receptor (CAR) T cells in solid tumors is tenuous, thereby necessitating the development and evaluation of gated systems. Here we found that murine GD2 CAR-T cells, specific for the tumor-associated antigen GD2, induce fatal neurotoxicity in a costimulatory domain-dependent manner. Meanwhile, human B7H3 CAR-T cells exhibit efficacy in preclinical models of neuroblastoma. Seeking a better CAR, we generated a SynNotch gated CAR-T, GD2-B7H3, recognizing GD2 as the gate and B7H3 as the target. GD2-B7H3 CAR-T cells control the growth of neuroblastoma in vitro and in metastatic xenograft mouse models, with high specificity and efficacy. These improvements come partly from the better metabolic fitness of GD2-B7H3 CAR-T cells, as evidenced by their naïve T-like post-cytotoxicity oxidative metabolism and lower exhaustion profile.

B7-H3 modulates endothelial cell angiogenesis through the VEGF cytokine

B7-H3 is a cell surface molecule in the immunoglobulin superfamily that has been shown to perform both immunological and non-immunological functions. It has also been found that vascular endothelial growth factor (VEGF) is an important molecule in the modulation of endothelial cell behavior. In this study, we analyzed the serum expression of B7-H3 in 113 rheumatoid arthritis and systemic lupus erythematous patients using the ELISA and found a positive correlation between B7-H3 and VEGF. Next, we investigated the involvement of B7-H3 in angiogenesis using human umbilical vein endothelial cells (HUVECs) with transient knockdown of B7-H3 and an in vivo Matrigel model. Data from the in vitro experiments showed that B7-H3 increased cell proliferation, migration, and tube formation, and correlated with the expression of VEGF. Furthermore, B7-H3 affected the formation of functional vascular networks in Matrigel plugs, which were dissected from mice injected with different HUVECs. Our data suggest that B7-H3 promotes angiogenesis through the enhancement of VEGF secretion. This is the first study proposing a significant role for B7-H3 in the promotion of angiogenesis and may provide further understanding of this gene's biological function.

Murine b7-h3 is a co-stimulatory molecule for T cell activation

The B7 family member B7-H3 (CD276) plays a key role during an immune response but its function remains controversial. In this study, we found that murine B7-H3 up-regulated the proliferation and cytokine production of T cells. Our study suggested that there was no interaction of murine B7-H3 with a triggering receptor expressed on myeloid cells (TREM)-like transcript 2 (TLT-2). Further studies demonstrated that mouse B7-H3 specifically bound to T cells and its receptor was not murine TLT-2. Moreover, murine B7-H3 was a positive co-stimulatory molecule in the regulation of T cell-mediated immune responses.