Oral squamous cell carcinoma cells induce osteoclast differentiation by suppression of osteoprotegerin expression in osteoblasts

Abstract

The invasion of oral squamous cell carcinoma (SCC) cells into the mandibular bone is a common clinical problem. It has been reported that BHY cells, a human oral SCC cell line, are capable of invading mandibular bone of nude mice. These results led us to examine possible mechanisms of osteoclastogenesis induced by BHY cells using in vitro culture systems. When BHY cells were cocultured with mouse bone marrow cells (BMCs), only few osteoclasts were formed, even though BHY cells express the receptor activator of NF-jB ligand (RANKL). However, adding BHY cells to a coculture of mouse primary osteoblasts (POBs) and BMCs markedly induced osteoclastogenesis in the absence of osteotropic factors. Furthermore, another oral SCC cell line, HSC-2, which does not express RANKL, also induced osteoclastogenesis in our cocultures. These effects were significantly, but not completely, inhibited by adding osteoprotegerin (OPG). In addition, we also found that TNFa released from these cells partially contributes to osteoclastogenesis via a RANKL-independent mechanism. Adding BHY or HSC-2 cells suppressed mouse OPG mRNA expression and protein production by POBs in cocultures of POBs and human oral SCC cells. This finding is consistent with the result that BHY cells and HSC-2 cells did not enhance osteoclastogenesis in cocultures of BMCs and POBs from OPG-deficient mice. Immunohistochemical analysis showed a reduction of OPG expression in osteolytic lesions as compared to normal lesions from oral SCC patients. Therefore, oral SCC-induced suppression of OPG expression in POBs appears critical for osteoclastogenesis, rather than expression of RANKL in SCC cells. ' 2005 Wiley-Liss, Inc.Key words: squamous cell carcinoma; RANKL; OPG; osteoclastogenesis Oral cancer most commonly involves the tissue of the tongue and the lips, and it can also occur on the floor of the mouth, gingiva or plate.1,2 The vast majority of oral cancers are squamous cell carcinomas (SCCs) 1,2 and oral SCCs frequently invade the mandibular bone. Advanced oral SCC has a high mortality and treatment is complicated by the disruption of speech and swallowing after surgical resection. It is generally agreed that patients with mandibular invasion should be treated surgically, but the extent of mandibular resection required remains controversial. Resection of the mandibular bone leads to physical damage as well as frequent psychological problems for the patients.It is well known that oral SCC invades the mandibular bone by direct extension and not by metastasis.3,4 Previous studies have suggested that the bone destruction associated with carcinoma invasion is mediated by osteoclasts rather than directly by the carcinoma.3,4 Invasion of the mandible by oral SCC is currently established only by radiological inspection. The cellular and molecular mechanisms regulating bone invasion and osteoclastic bone resorption by oral SCC are poorly understood.Osteoclasts are multinucleated cells that are responsible for bone resorption. [5][6][7] Osteoclastic bone resorption consists...

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

“…However, adding BHY cells to a coculture of mouse POBs and BMCs markedly induced osteoclastogenesis in the absence of osteotropic factors. Consistent with these results, HSC-2 cells, which do not express RANKL, also induced osteoclast formation in cocultures of mouse BMCs and POBs without any osteotropic factors (39). The addition of BHY cells suppressed mouse OPG mRNA expression and protein production by POBs.…”

“…Several oral SCC cells in patients and oral SCC cell lines express RANKL (38)(39)(40). Recently, Chuang et al compared RANKL expression between buccal SCC without bone invasion (25 cases) and gingival SCC with invasion (15 cases).…”

“…On the other hand, not all cancers express RANKL, and cell-to-cell contact between cancer cells and host cells does not always lead to RANKL expression (43,44). We showed in a previous study that BHY cells, which were highly invasive to the mandibular bone when inoculated into the masseter of nude mice, expressed RANKL on their cell surface but failed to induce osteoclastogenesis in cocultures of mouse bone marrow cells (BMCs) and BHY cells (39). However, adding BHY cells to a coculture of mouse POBs and BMCs markedly induced osteoclastogenesis in the absence of osteotropic factors.…”

A Novel Function of CXCL13 to Stimulate RANK Ligand Expression in Oral Squamous Cell Carcinoma Cells

“…Activation of bone-resorbing osteoclasts at the tumor-bone interface facilitates the osteolytic process and bone invasion of cancer cells (14). Recent studies indicated CXCR5 chemokine receptor expression by colon carcinoma cells and potential role in tumor growth (19).…”

“…Tumor cells activate bone resorbing osteoclasts, thereby facilitating the osteolytic process and bone invasion (14). RANKL is a critical osteoclastogenic factor in the bone microenvironment (7).…”