RANKL Bioassay, Propagation Model
Receptor activator of nuclear factor-κB (NF-κB; RANK/TRANCE receptor/TNFRSF11A) is a member of the tumor necrosis factor receptor (TNFR) family. Binding of its ligand (RANKL) to the receptor regulates osteoclast formation, activation and survival in bone modeling and remodeling, and several other pathologic conditions characterized by increased bone turnover. The osteoclastogenesis signaling pathway is activated by osteoblasts producing RANKL, which binds to and activates the RANK receptor on osteoclast precursors. The adapter protein TRAF6 is recruited to the RANK receptor and activates NF-κB, which leads to NF-κB translocation to the nucleus. This increases the expression of c-FOS which, together with NFATc1, increases the transcription of osteoclastogenic genes. Osteoprotegerin (OPG) binds to and inhibits RANKL. In cells with excess RANKL or insufficient OPG, upregulated RANKL/RANK signaling leads to superfluous osteoclast formation and bone resorption, causing pathologic bone loss and destruction. In osteosarcoma, in addition to cancer-induced bone destruction, RANKL is also involved in tumorigenesis and metastasis. RANKL inhibition significantly delays mammary tumor formation in carcinogen and hormone-induced breast cancer mouse models. Denosumab is a human IgG2 monoclonal antibody that targets and inhibits RANKL. It is used to treat osteoporosis and hypercalcemia, as well as bone cancer and other cancer-associated bone disease. Denosumab blocks the RANK-RANKL interaction, inhibiting osteoclast formation, function and survival; thus, it decreases bone resorption and interrupts cancer-induced bone destruction. The RANKL Bioassay is a bioluminescent cell-based assay designed to measure RANK/RANKL pathway stimulation or inhibition. The RANKL Bioassay Cells are provided in a thaw-and-use format as cryopreserved cells that can be thawed, plated and used in an assay without the need for cell propagation. The RANKL Bioassay is also available in a Cell Propagation Model (CPM) format, which includes cryopreserved cells that can be thawed, propagated, and banked for long-term use (RANKL Bioassay, Propagation Model, Cat.# J3102). The RANKL Bioassay is comprised of a human cell line engineered to express the RANK receptor and a luciferase reporter driven by a response element (RE). When RANKL binds the RANK receptor, transduced intracellular signals activate the RE, resulting in luminescence.