CD276 Knockout Cell Line-MG63

Breast cancer (BC) is the most common malignancy in women. Immunotherapy has revolutionized the treatment of many malignancies, and the introduction of immune checkpoint inhibition has also brought beneficial effects to BC. However, many BC patients are not suitable for such T-cell-based therapies, while some patients do not respond to immunotherapy or have a short response. Therefore, there is still a huge medical need for novel therapies, especially for triple-negative BC. CD276 (B7-H3) is overexpressed on tumor cells and tumor vessels in a variety of tumors and is a promising target for immunotherapy. Here, tumor samples from 25 patients were analyzed by immunohistochemistry to evaluate the levels of CD276. The potential of the novel bispecific CD276xCD3 antibody CC-3 in BC treatment was evaluated using multiple in vitro functional assays. Significant expression of CD276 was observed in all analyzed tumor samples, including triple-negative BC. In BC cell analysis, CC-3 induced profound T cell activation, proliferation, and formation of T cell memory subsets. Furthermore, CC-3 treatment induced cytokine secretion and potent tumor cell lysis.

Since cytokines regulate key aspects of T cell function, such as proliferation and effector cell differentiation, the researchers analyzed whether CC-3 activation of T cells would have a corresponding effect on cytokine release. To this end, PBMCs were co-cultured with target cells and treated with CC-3 or isotype control (1 nM each). After 24 hours, culture supernatants were analyzed by Legendplex analysis, which showed a significant increase in the immune effector cytokines IL-2, IFN-γ, and TNF. No effect was observed when CD276 knockout (KO) cells were used, which again confirmed that the bsAb here has target cell-restricted activity (Figure 1).

Figure 1. The levels of IL-2, IFN-γ and TNF in culture supernatants were measured after 24 hours using Legendplex assays. (Hagelstein I, et al., 2024)