This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Dicer is a highly conserved RNase III type enzyme found in almost all eukaryotes that is essential for the RNA interference (RNAi) and microRNA pathways. During the last several years an increasing number of reports have found Dicer to be aberrantly expressed in different types of cancer, including oral squamous cell carcinomas (OSCCs). Recently, the dicer gene has been predicted to produce 11 mRNA splice variants bearing modified coding sequences. Our preliminary data suggests that one of these predicted Dicer mRNA splice variants is expressed in cells and appears to be upregulated in OSCC cell lines. Because the expression and function of the Dicer mRNA splice variants have not been well characterized and it currently remains unclear as to their biological significance, this proposal will explore the role of this particular Dicer mRNA splice variant in relation to oral cancer biology. Therefore, to better assess and correlate the expression patterns of the Dicer mRNA splice variant relative to OSCCs and disease progression this proposal will characterize its mRNA and protein expression levels in both OSCC cell lines and tissues ranging from dysplastic to invasive OSCCs in relation to non-cancerous counterparts. Furthermore, to enhance our understanding of the mechanisms regulating its aberrant expression this study will also analyze whether its aberrant expression in oral cancer cells is due to transcriptional and/or post-transcriptional regulatory mechanisms. Because the significance of the dysregulation of this splice variant in terms of cancer cell properties is not understood, this proposal will further seek to examine the biological effects of reducing the levels of the Dicer mRNA splice variant in oral cancer cells using RNAi knockdown strategies and analyze the effects of overexpressing it in both primary and immortalized human oral keratinocytes. The biological metrics will include cell proliferation, apoptosis, cell migration and invasion, and oncogenic transformation assays. By successfully addressing these specific aims this will lead to a better understanding of oral cancer biology. Furthermore, it will shed new insights into the function of Dicer mRNA splice variants and what roles they play in oral cancer development and progression.