Characterization of bone resorption in novel in vitro and in vivo models of oral squamous cell carcinoma

Abstract

Objectives Oral squamous cell carcinoma (OSCC) is the most commonly diagnosed oral malignancy in humans and cats and frequently invades bone. The objective of this study was to determine if feline OSCC serves as a relevant model of human OSCC in terms of osteolytic behavior and expression of bone resorption agonists. Materials and Methods Novel feline OSCC cell lines (SCCF2 and SCCF3) were derived from spontaneous carcinomas. Gene expression and osteolytic behavior were compared to an established feline OSCC cell line (SCCF1) and three human OSCC cell lines (UMSCC-12, A253 and SCC25). Interaction of OSCC with bone and murine pre-osteoblasts (MC3T3) was investigated using in vitro co-culture techniques. In vivo bioluminescent imaging, faxitron radiography and microscopy were used to measure xenograft growth and bone invasion in nude mice. Results Human and feline OSCC expressing the highest levels of parathyroid hormone-related protein (PTHrP) were associated with in vitro and in vivo bone resorption and osteoclastogenesis. MC3T3 cells had increased receptor activator of nuclear factor κB ligand (RANKL) expression and reduced osteoprotegerin (OPG) expression in conditioned medium from bone-invasive SCCF2 cells compared to minimally bone invasive SCCF3 cells, which was partially reversed with a neutralizing anti-PTHrP antibody. Human and feline OSCC cells cultured in bone-conditioned medium had increased PTHrP secretion and proliferation. Conclusion Feline OSCC-induced bone resorption was associated with tumor cell secretion of PTHrP and with increased RANKL : OPG expression ratio in mouse preosteoblasts. Bone-CM increased OSCC proliferation and secretion of PTHrP. The preclinical models of feline OSCC recapitulated the bone-invasive phenotype characteristic of spontaneous OSCC and will be useful to future preclinical and mechanistic studies of bone invasive behavior.

Animal Models of Bone Metastasis

“…14, 15). 75 Bone resorption was associated with PTHrP expression, and the EGFR ligands, amphiregulin and TGF-α, were found to further increase PTHrP. In contrast, OPG mRNA expression was very low in the SCCF2 cells.…”

“…75 More than half of the patients with HNSCC were diagnosed at the later stages of disease characterized by local bone invasion, bone destruction, and metastasis to local lymph nodes. 125,147 …”

“…Treatment with a bone resorption–inhibiting bisphosphonate, zoledronate, was found to reduce tumor growth, prevent bone loss, and inhibit bone invasion in mice carrying feline SCC orthotopic xenografts. 75,77 …”

Upregulation of osteoprotegerin expression correlates with bone invasion and predicts poor clinical outcome in oral cancer

“…OPG-mediated resistance to TRAIL-induced apoptosis provides cancer cells with a critical growth advantage, contributes to tumor progression, and correlates with tumor aggressiveness and poor patient prognosis [18]. In OSCC cells, RANKL, RANK and OPG expression has been detected in vitro and in vivo studies [19][20][21][22]. Recent reports have demonstrated the crucial role of the RANKL/RANK/ OPG triad in osteoclast-mediated bone destruction associated with OSCCs, which frequently invade the mandible or the maxilla [23][24][25].…”

Combined zoledronic acid and meloxicam reduced bone loss and tumour growth in an orthotopic mouse model of bone‐invasive oral squamous cell carcinoma

“…16 Nontumor-bearing mice were similarly anesthetized and injected with cell-free PBS. Treatment was initiated 3 days following injection of SCCF2Luc cells, and consisted of twice weekly subcutaneous injections of ZOL at 0.1 mg/kg diluted in 0.9% sodium chloride (saline).…”