The 5-year survival rate of oral cavity cancer is poorer than breast, colon, or prostate cancer, and has only slightly improved by 5% in the last three decades. Hence, new therapeutic strategies are urgently needed. Our long-term goal is to identify innovative targets for therapeutic intervention by dissecting the molecular mechanism of how the RNA-binding protein La contributes to oral tumor progression. The La protein is a RNA chaperone, known to regulate mRNA translation of a number of cellular proteins. Our preliminary data show that the human La protein is overexpressed in squamous cell carcinoma (SCC) tissue of the oral cavity and strongly suggest that La is involved in proliferation, migration, and invasion of oral SCC cells. Interestingly, in oral SCC cells, La expression correlates with protein expression of matrix metalloproteinase type 2 (MMP-2). MMP-2 is well known to be overexpressed in many different types of cancer, including oral cancer, and is implicated in tumor progression of oral SCC. Based on our preliminary data we hypothesize that overexpression of the RNA chaperone La in oral SCC cells stimulates MMP-2 mRNA translation and contributes to tumor progression. To test our hypothesis we will-in Specific Aim 1-demonstrate that La regulates MMP-2 mRNA translation in oral SCC cells. We will focus on the interaction of La with MMP-2 mRNA by applying La-specific RNA-binding protein immunoprecipitation (RIP) and will define whether the presence of La stimulates active MMP2-mRNA translation in oral SCC cells by performing sucrose-density gradients. Once complete, this aim will establish the underlying molecular mechanism of La-dependent MMP-2 translation in oral SCC cells. To further test our hypothesis we will-in Specific Aim 2-establish that La overexpression contributes to tumor progression of oral SCC in vivo. Herein, we will define that aberrant elevated La contributes to tumor growth and bone invasion in vivo, by creating a La-overexpressing orthotopic floor-of- mouth mouse model. To monitor tumor progression, we will apply in vivo bioluminescence imaging and micro- computed tomography, followed by histology of tongue, floor of mouth, and mandible. To define in vivo interaction of La and MMP-2 mRNA we will perform RIP assays of oral tumor tissue. Whereas significant effort has been placed on understanding control of MMP-2 enzyme activity, our proposed studies will elucidate the impact of translational control of MMP-2 mRNA in tumor progression;an highly innovative area that has received relatively less attention. Whereas the cancer-associated La protein is likely to be involved in translational misregulation of a variety of mRNAs, this project will focus to elucidate the underlying mechanism of La-dependent MMP-2 mRNA translation in oral SCC progression. This knowledge will foster our future research on identification of novel molecular decoys to specifically inhibit the interaction of the La protein and its target mRNAs to improve the survival rate and response to chemotherapy of oral cavity cancer patients.
In this study, we will create a floor-of-mouth mouse model to establish that the cancer-associated La protein contributes to oral tumor progression. Furthermore, we will study the underlying molecular mechanism for how the RNA-binding protein La misregulates cellular pathways to elucidate novel avenues for more effective chemotherapeutics in oral cancer patients.
|Sommer, Gunhild; Rossa, Carlos; Chi, Angela C et al. (2011) Implication of RNA-binding protein La in proliferation, migration and invasion of lymph node-metastasized hypopharyngeal SCC cells. PLoS One 6:e25402|