Current theories of tumor progression postulate that normal epithelial cells need to acquire mechanisms to evade apoptosis and acquire several other essential biologic properties in order to progress to invasive and metastatic tumors. Programmed cell death after detachment from the basement membrane is known as an oikis. The central hypothesis is of this application is that evasion of anoikis is associated with local tumor progression, and metastasis of squamous cell carcinoma of the oral cavity (SCCOC). Four individual inter-related hypotheses would be evaluated in four separate Aims. The first hypothesis is that anoikis-resistance is necessary but not sufficient for tumor progression, including local growth as well as regional and distant metastases. To demonstrate that anoikis-resistance is associated with disease progression, we will investigate the growth of human SCCOC cell lines in an orthotopic, nude mouse model that we have developed. Human SCCOC cell lines and anoikis resistant cells that have been selected in vitro will be injected into the tongues of nude mice, and these mice will be examined for tumor growth, length of survival and the presence of regional nodal and distant metastases. Conversely, we will demonstrate the anoikis resistance of cell lines that we have derived from in vivo orthotopic selection of regional and distant metastases by quantitation of their survival in suspension culture. The second hypothesis guiding the next Aim of this application is that the pro-survival signals mediating anoikis resistance are not constitutive but rather are induced by the process of cell detachment data to date, suggest that this is due to the induction of apoptosis suppression that is far downstream, as we have found that cell detachment induces resistance to multiple forms of apoptosis induction by both the extrinsic and intrinsic pathways. The third hypothesis is that the BiR containing proteins c-IAP-2, survivin, and XIAP are mediating the detachment-induced survival in the face of multiple forms of apoptotic signaling. This hypothesis will be tested by increasing and decreasing expression or activity of either of these two regulatory molecules in5cell lines and examining the resultant cell lines for their anoikis resistance in vitro and their tumorigenicity and metastatic potential in vivo. The final hypothesis is that expression of the downstream apoptotic regulatory molecules c-IAP-2, survivin, and XIAP is associated with tumor progression and metastasis in human SCCOC and in an orthotopic model of oral cancer. To demonstrate that these apoptotic regulatory molecules are expressed in human SCCOT tumors and that their expression is linked with poorer clinic pathologic outcomes, archival human SCCOT tumor will be evaluated for expression of these apoptotic regulatory molecules by in situ hybridization and immunhistochemistry. It is anticipated that high expression of apoptotic inhibitory molecules in tumor specimens from patients with poor clinicopathologic outcomes will provide insight into the potential roles of the IAPsas prognostic indicators and/or therapeutic targets. Further support for these roles of IAPs will result from demonstration that increased expression of these molecules leads to more aggressive tumor growth and metastasis in an orthotopic metastatic model of SCCOT.
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