Mechanisms of bone invasion and tumor growth in models of head and neck cancer.

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DESCRIPTION (provided by applicant): Squamous cell carcinoma of the head and neck (HNSCC) commonly invades bone, which is associated with severe morbidity and reduced patient survival. The primary objective of this project is to inhibit bone invasion and growth of HNSCC by identifying and targeting mechanisms of tumor-induced bone resorption. These investigations will utilize in vitro and in vivo models of bone-invasive HNSCC, employing human cell lines derived from spontaneous HNSCC tumors. The following overall hypothesis will be tested: HNSCC invasion into bone is caused by a vicious cycle of tumor-induced bone resorption and expression of tumor-derived cytokines. Specifically, HNSCC-derived parathyroid hormone-related protein (PTHrP) and prostaglandin E2 (PGE2) induce osteoclastic bone resorption which releases transforming growth factor-beta (TGF-P) from the bone matrix. TGF-J3 induces additional tumor-synthesis of PTHrP and PGE2 which are known to support tumor growth as well as bone resorption. Furthermore, combining a bone resorption inhibitor, zoledronic acid, with a cyclooxygenase-2 inhibitor, meloxicam, will block the vicious cycle and reduce bone invasion and tumor growth. Three specific aims are proposed. First, determine if cytokine blockade will inhibit HNSCC-induced bone resorption. Resorption will be evaluated by measuring stromal cell expression of RANKL and OPG (mediators of osteoclast activity), differentiation of pre-osteoclast cells, and TGF-J3 release from bone cultures. PTHrP will be reduced with siRNA, and PGE2 will be inhibited by meloxicam. Second, examine how bone resorption affects HNSCC proliferation and expression of PTHrP and COX-2. The effects of conditioned medium from lytic and non-lytic bone will be compared, with and without antibody neutralization of TGF-p. Third, determine the effect of multimodal therapy (zoledronic acid combined with meloxicam) on tumor growth and bone invasion in vitro and in vivo. Co-cultures will be used to determine the effect of treatment on HNSCC proliferation and apoptosis in the presence of bone. In vivo tumor growth and bone invasion will be measured using orthotopic, xenograft nude mouse models of luciferase-expressing HNSCC, quantitated with in vivo bioluminescent imaging and micro-CT. HNSCC represents over 90% of head and neck cancers, the 6th most common cancer in the world. Patient survival has not significantly improved over the past 30 years. Bone invasion frequently occurs and is associated with a poorer prognosis. This study will determine if simultaneous inhibition of bone resorption and COX-2 activity will successfully block bone invasion and reduce tumor growth in models of HNSCC.