Abstract 1580: A novel C. elegans animal model for human RET receptor function.

Abstract RET (Rearranged in Transfection) is a receptor tyrosine kinase mutated in the cancer syndrome multiple endocrine neoplasia 2 and linked to many other cancers, including medullary thyroid carcinoma and cancers of the adrenal gland. There are two distinct isoforms of RET, RET9 and RET51, with in vitro evidence indicating isoforms induce unique phosphorylation patterns on select tyrosine residues, possess different cell transforming and differentiation abilities, and bind/activate a unique set of substrates. However, these processes are challenging to dissect in complex organisms because both RET isoforms are ubiquitously co-expressed. We have generated a novel Caenorhabditis elegans model for RET expression to dissect the role of individual RET isoforms. C. elegans do not encompass a homologue of RET, thus we injected chimeric constructs in which human RET isoform sequences were fused to a N-terminal myristoylation signal for membrane targeting and expressed under the control of the C. elegans mechanosensory neuron-specific promoter, mec-4. The resultant transgenic animals were scored for phenotypes of RET-expressing neurons. We found that RET9 expressing animals have near WT phenotype, while RET51 expressing animals exhibited an axon termination phenotype where the PLM mechanosensory neuron of the tail fails to migrate to its correct location. This is indicative of early neuron terminal differentiation attributed to RET downstream signalling. Furthermore, strains harboring constitutively active oncogenic versions of RET9 or RET51 had severe PLM axon defects, with the RET51 phenotype being significantly more penetrant. Through generating strains with point mutations at select tyrosine residues and assessing the resulting phenotype, we have determined Y1062 and Y1096 to be main signalling hubs contributing to the RET-mediated phenotype in C. elegans. We are currently testing known kinase inhibitors, assessing efficacy and toxicity of potential RET inhibiting therapeutics. Using C. elegans as a platform to model RET is a quick and efficient system to gain insight on RET isoforms, delineate molecular events contributing to cancer progression, and investigate therapeutic agents that can be used to treat RET associated cancers. Citation Format: Jordan D.S. Zelt, Ian D. Chin-Sang, Lois M. Mulligan. A novel C. elegans animal model for human RET receptor function. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1580. doi:10.1158/1538-7445.AM2013-1580