4-1BB/TNFRSF9 Protein, Human (HEK293, mFc)

4-1BB, encoded by TNFRSF9 (CD137, ILA), belongs to the tumor necrosis factor (TNF) receptor superfamily. 4-1BB is a surface glycoprotein expressed in a variety of cells, such as T cells, B cells, natural killer (NK) cells, dendritic cells (DCs), eosinophils and mast cells; and even a variety of tumor cells such as human leukemia cells. It is widely distributed in vascular smooth muscle, tumor vascular walls and liver tissue of hepatocellular carcinoma. 4-1BB preferentially selects CD8+ cells rather than CD4+ cells. It provides co-stimulatory signals and activates the cytotoxic effect of CD8+ T cells and contributes to the formation of memory T cells. Finally, it promotes the immune system to fight tumors. In addition, CD137 binds CD137L to signal monocytes, increasing their survival, proliferation and stimulating their migration and extravasation. In addition, it induces the release of multiple proinflammatory factors, leading to the influx of inflammatory monocytes into tissues and forming an inflammatory environment . Specifically, CD137 promotes the migration of monocytes/macrophages into the tumor microenvironment by upregulating the expression of Fra1. It also promotes the differentiation of monocytes/macrophages into osteoclasts, thereby providing a favorable microenvironment for breast cancer cells to colonize and grow in the bone. It provides a promising therapeutic strategy for breast cancer metastasis . In addition, CD137 signaling promotes endothelial cell (EC) apoptosis through pro-oxidative and pro-inflammatory mechanisms mediated by the Nrf2 and NF-κB pathways, respectively . The 4-1BB protein has low homology in humans and mice, with a sequence similarity of 56.75%.