Oral squamous cancer cell-bone interactions and resistance to alendronate (Fosamax) drug therapy in 3D-live bone-microenvironment
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Bisphosphonates (BPs) have been used clinically as anti-resorptive/cancer agents with confounded clinical outcomes and uncertain/conflicting biological understanding. This study was designed to evaluate the impact of clinically used anti-resorption drug alendronate (ALN) on cancer-bone metastasis and bone biology using novel 3D cancer-bone interaction model systems. To test the effects of ALN on the cancer-bone metastasis/interactions and bone biology we have utilized a novel 3D Co-cultures of live mouse neonatal calvarial bone organs with oral squamous cancer cells in a roller tube model systems (Curtin et al, 2012) in the absence and presence of ALN. These model systems under bone resorption and formation conditions were evaluated by chemical, biochemical, and histological analyses of the used media and calvarial bones. At the end of 8 days, the calvarial bones co-cultured with oral cancer cell lines in the absence and presence of ALN were processed for histological observations, TRAP and ALP enzyme activities, and neutral red staining. These studies were complemented by the effects of ALN on oral cancer cells under 2D classic cell culture conditions. In 3D-bone organ cultures under resorption conditions, oral cancer cells induce differentiation of osteoclasts and bone resorption and inclusion of ALN inhibited cancer-induced bone resorption. However, in both bone resorption and formation models the oral cancer cells colonized the bone and while treatment with ALN inhibits bone resorption, no effect on bone colonization was evident. Contrary to those under 2D cell culture conditions exposure to ALN of confluent and non-confluent oral cancer cells in the absence of live bone impacted oral cancer cells significantly in a dose dependent manner. Our studies using live bone organ cultures with oral cancer cells under specific dissociated bone remodeling stages, viz., resorption or formation only, revealed major and significant biological events which led to the conclusions that: (a) In the absence of bone in 2D cultures oral cancers are sensitive to ALN treatment whereas in the 3D live bone microenvironment tumors are resistant to ALN drug therapy, and (b) oral cancer-bone metastasis is independent of bone remodeling stage.