We have demonstrated that EGFR up-regulation in OSCC is due to activated gene transcription and that down-modulation of EGFR results in decreased proliferation of OSCC but not normal cells. Further investigation in our laboratory revealed inhibition of tumor growth in vivo following intratumoral inoculation of an EGFR antisense expression construct based on the U6 small nuclear RNA promoter in complexed with DC-chol liposomes. This anti-tumor effect was accompanied by decreased EGFR protein expression in the tumors and increased apoptosis. Preliminary results suggest that EGFR signaling in OSCC involves constitutive activation of Stat3alpha-beta and that down-modulation of Stat3 using antisense oligonucleotides or dominant negative mutants result in inhibition of OSCC proliferation. The importance of this autocrine pathway is underscore by our finding that protein expression levels of EGFR in the primary OSCC tumor is a significant and independent predictor of decreased survival. Therefore, we propose to test the hypothesis that the loss of growth control in OSCC is mediated through acquisition of an EGFR autocrine signaling pathway, which can be targeted using an antisense gene therapy approach.
In specific aim 1 we propose to characterize the effects of EGFR antisense therapy in OSCC in vitro and in murine xenograft models by determining: a) the association between EGFR expression levels and anti-tumor activity; and b) the dose, schedule, and time-dependent parameters for optimal effect.
In specific aim 2 we propose to determine the mechanism of the anti-tumor effects of EGFR antisense gene therapy in vitro and in murine xenograft models by: a) characterizing the impact of treatment on expression and activation of specific STAT protein isoforms; and b) examination the consequences of therapy on apoptosis.
In specific aim 3 we propose to determine in the phase I setting, the maximally tolerated dose (MTD) and biologic effects of intratumoral liposome-mediated EGFR antisense gene therapy in OSCC patients.
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