The inhibition of RANKL/RANK signaling by osteoprotegerin suppresses bone invasion by oral squamous cell carcinoma cells

Abstract

Oral squamous cell carcinomas (OSCCs) are malignant tumors that frequently invade the maxilla and mandibular bone. However, the molecular mechanisms underlying bone invasion by OSCC are unclear. Recent studies showed that receptor activator of nuclear factor κB (RANK) was expressed not only in osteoclast precursors but also in tumor cells. Therefore, we examined whether RANK ligand (RANKL)/RANK signaling regulates bone invasion by OSCC cells in vivo and in vitro. We first injected human OSCC B88 cells into the masseter region of nude mice. Mice were treated for 3 weeks with osteoprotegerin (OPG), the decoy receptor for RANKL. Treatment with OPG decreased bone invasion by B88 cells, reduced the number of osteoclasts and increased B88 cell apoptosis. However, OPG did not affect apoptosis and proliferation in B88 cells in vitro, suggesting that the effects of OPG on apoptosis in B88 cells are restricted in a bone environment. RANK was expressed in the B88 cells and in OSCC cells from patients. RANKL induced NF-κB activation and extracellular signal-regulated kinase phosphorylation in B88 cells and enhanced B88 cell migration in a modified chemotaxis chamber equipped with a gelatin-coated filter. OPG inhibited RANKL-induced NF-κB activation, extracellular signal-regulated kinase phosphorylation and cell migration. Our data clearly indicate that RANKL/RANK inhibition suppresses bone invasion by inhibiting osteoclastogenesis and cancer cell migration and by inducing apoptosis of cancer cells via indirect anticancer action in vivo.

The RANKL/RANK system as a therapeutic target for bone invasion by oral squamous cell carcinoma

“…Thus, the suppressive effect of OPG on B88 tumor burden is attributed to increased cell death rather than inhibition of proliferation. However, OPG did not affect apoptosis and proliferation of B88 cells in vitro, suggesting that effects of OPG on apoptosis in B88 cells are restricted to the bone environment (48).…”

“…To support these results, RANKL enhanced B88 cell migration in a modified chemotaxis chamber equipped with a gelatin-coated filter. This effect was inhibited by OPG (48).…”

Potential molecular targets for inhibiting bone invasion by oral squamous cell carcinoma: a review of mechanisms

“…RANKL inhibition by using recombinant OPG was also examined in patients with breast cancer or multiple myeloma with osteoclastic bone lesions [93]. Shin et al found that treatment with OPG decreased bone invasion of human OSCC B88 cells, while being injected into the masseter region of nude mice [94]. These examples have reminded researchers of the area of bone invasion.…”

Chorioamniotic membrane senescence: a signal for parturition?

“…OPG, a soluble form of TNF receptor family of proteins, is a decoy receptor for the receptor activator of nuclear factor (NF)-kB ligand. 72,73 By binding receptor activator of NF-kB ligand, OPG inhibits NF-kB and therefore prevents inflammation. 74 OPG also promotes osteoclast formation by preventing apoptosis through TNFrelated apoptosis-inducing ligand.…”