Homotypic RANK signaling differentially regulates proliferation, motility and cell survival in osteosarcoma and mammary epithelial cells

Abstract

Summary RANKL (receptor activator of NF-kB ligand) is a crucial cytokine for regulating diverse biological systems such as innate immunity, bone homeostasis and mammary gland differentiation, operating through activation of its cognate receptor RANK. In these normal physiological processes, RANKL signals through paracrine and/or heterotypic mechanisms where its expression and function is tightly controlled. Numerous pathologies involve RANKL deregulation, such as bone loss, inflammatory diseases and cancer, and aberrant RANK expression has been reported in bone cancer. Here, we investigated the significance of RANK in tumor cells with a particular emphasis on homotypic signaling. We selected RANK-positive mouse osteosarcoma and RANK-negative preosteoblastic MC3T3-E1 cells and subjected them to loss-and gain-of-RANK function analyses. By examining a spectrum of tumorigenic properties, we demonstrate that RANK homotypic signaling has a negligible effect on cell proliferation, but promotes cell motility and anchorage-independent growth of osteosarcoma cells and preosteoblasts. By contrast, establishment of RANK signaling in non-tumorigenic mammary epithelial NMuMG cells promotes their proliferation and anchorage-independent growth, but not motility. Furthermore, RANK activation initiates multiple signaling pathways beyond its canonical target, NF-kB. Among these, biochemical inhibition reveals that Erk1/2 is dominant and crucial for the promotion of anchorage-independent survival and invasion of osteoblastic cells, as well as the proliferation of mammary epithelial cells. Thus, RANK signaling functionally contributes to key tumorigenic properties through a cell-autonomous homotypic mechanism. These data also identify the likely inherent differences between epithelial and mesenchymal cell responsiveness to RANK activation.

Receptor activator of nuclear factor κB expression is a prognostic factor in human osteosarcoma

“…Dysregulation of this system has been observed in multiple tumours of various origins, including malignant bone tumours, multiple myeloma, breast cancer and prostate cancer. The RANK/RANKL system induces osteolytic bone lesions, and blocking of this system prevents bone destruction (4)(5)(6)(7)(8)(9)(10). The results of the present study confirm previous data indicating that the chemotherapy responsiveness of patients with tumours that are RANK positive is equal to that of patients with RANK-negative tumours, whereas RANK-positive tumours are associated with a significantly higher mortality rate (11).…”

“…Activation of RANK, which is expressed on the surface of osteoclast precursors, by the binding of its ligand results in activation of the nuclear factor κB (NF-κB) and c-Jun N-terminal kinase signalling pathways, leading to differentiation of osteoclast precursor cells into pro-osteoclasts, which mature into active osteoclasts (5). RANK is activated by its ligand RANKL, a member of the TNF ligand superfamily (also known as OPGL or TRANCE), which is negatively controlled by osteoprotegerin (OPG).…”

RANK Ligand Blockade with Denosumab in Combination with Sorafenib in Chemorefractory Osteosarcoma: A Possible Step Forward?

“…Osteoblasts secrete RANKL, which leads to the differentiation and activation of osteoclasts promoting the release of bone-derived growth factors and osteolysis [6]. RANK signalling has been associated in preclinical osteosarcoma models with increased cell mobility and anchorage-independent growth [7]. In vitro studies in osteosarcoma cell lines using either osteoprotegrin (a physiological antagonist of RANK) or RANK-Fc protein to inhibit RANK signalling resulted in a reduction in osteosarcoma cell migration, invasion ability and anchorage-independent viability [8,9].…”

Alpha B‐crystallin promotes the invasion and metastasis of gastric cancer via NF‐κB‐induced epithelial‐mesenchymal transition

“…Given that NF‐κB signalling pathway is involved in cancer migration and invasion,18 we reasoned that CRYAB might contribute to EMT changes via the activation of NF‐κB signal pathway in gastric cancer. To test this hypothesis, we initially examined the protein expression levels of NF‐κB p65 and phosphorylated NF‐κB p65 (p‐NF‐κB p65) with CRYAB knockdown or overexpression in gastric cancer cells.…”