Abstract SS02-02: A long walk from FGFR2 alternative splicing to cancer progression

Abstract Previously, our group developed fluorescence-based alternative splicing reporters of epithelial plasticity to visualize phenotypic transitions in real time in vivo (Oltean et al., 2008; Oltean et al., 2006; Somarelli et al., 2013). We reasoned that our mesenchymal-epithelial transition (MET) reporters could be extremely useful to test the hypothesis that MET is a modulator of metastatic colonization in undifferentiated, sarcomatoid-like cancers. Along these lines, we generated a lineage-tracing reporter based on combined transcription and alternative splicing regulatory elements to measure the frequency of MET-like events during tumor growth and metastasis in the post-EMT Dunning rat AT3 model of prostate cancer. In a parallel set of experiments, we also used the combinatorial control strategy to drive a suicide reporter that kills cells undergoing MET to test the hypothesis that MET is required for metastatic colonization in undifferentiated, mesenchymal-like cancers. The combinatorial use of both transcription and alternative splicing regulation provided exquisite cell-type discrimination in the expression of enzymes, such as the Cre recombinase and Diphtheria A (DipA) toxin. Using the lineage tracing reporter system, we were able to quantify, for the first time, overall frequencies of MET during primary tumor and metastatic growth. Remarkably, we observed that the frequency of MET within primary tumors and metastatic nodules was not significantly different, with very low rates of MET taking place during the growth of tumors and metastases. Moreover, targeted killing of cells undergoing MET did not reduce the number of macrometastatic colonies in the lungs. This work demonstrates the ability of tumors to metastasize efficiently without the need for MET, and we suggest that this may be similar to the behavior of highly aggressive prostate carcinosarcomas or undifferentiated carcinomas. Using this system we will describe new experiments that will address differential behavior in different types of prostate cancer. Citation Format: Jason A. Somarelli, Jason A. Somarelli, Daneen Schaeffer, Daneen Schaeffer, Mathew S. Marengo, Mathew S. Marengo, Tristan Bepler, Tristan Bepler, Douglas Rouse, Anne F. Buckley, Jonathan I. Epstein, Andrew J. Armstrong, Mariano A. Garcia-Blanco, Mariano A. Garcia-Blanco. A long walk from FGFR2 alternative splicing to cancer progression. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr SS02-02. doi:10.1158/1538-7755.DISP13-SS02-02