The Role of Insulin/IGF-1 Signaling in Tumor Supression and Aging

University Of California, San Francisco, San Francisco CA

Investigators

Abstract

[unreadable] DESCRIPTION (provided by applicant): The insulin/IGF-1 receptor daf-2 controls the lifespans of several model organisms, including the nematode Caenorhabditis elegans. Inhibition of daf-2 activity results in a doubling of lifespan and delays the onset of age-related diseases. In a C. elegans cancer model, daf-2 mutants have enhanced resistance to tumor growth. In gld-1 (-) tumor model worms, germ cells overproliferate and the resulting tumors completely overtake the worm body and cause premature death. Remarkably, the short lifespan of gld-1 (-) worms is completely suppressed by daf-2 inhibition, and in fact, daf-2(-); gld-1 (-) double mutant worms live twice as long as wild-type and four times as long as gld-1 (-) worms. It is known that daf-2 signaling affects gene expression mediated by the FOXO-family transcription factor DAF-16 and that daf-16 is completely required for the enhanced tumor resistance of daf-2 mutant animals. A long-term goal of this project is to understand precisely how the daf-2/daf-16 pathway controls tumors. Specifically, this project will (1) characterize the network of DAF-16 interacting proteins and examine genetically the role of DAF-16 binding partners and downstream targets in tumor control and lifespan regulation; and (2) elucidate steps in the regulation of DAF-16 activity (specifically) and tumor proliferation / lifespan (generally) using pharmacologically active small molecules. To achieve theis aims, downstream target genes that are transcriptionally regulated by DAF-16 will be tested by RNAi knockdown for their contribution to DAF-16's tumor suppression function. Additionally, novel protein binding partners of DAF-16 itself will also be characterized and analyzed for their role in tumor suppression. Finally, a chemical genetic screen will be used to target tumor proliferation and lifespan regulatory signaling, with the aim of investigating upstream signaling from insulin/IGF-1 pathway to downstream components in the DAF-16 network. Relevance: DAF-2 mutations extend lifespan and completely protect the animals from early tumor-related death by enhancing p53-mediated cell death (apoptosis) and reducing the division rate of tumor cells; both processes are hallmarks of tumor suppression in most organisms. More directly, we know that insulin hormone signaling also influences aging and cancer in mammals. Much of the same machinery used by C. elegans for insulin signaling/lifespan regulation is conserved in higher organisms, and some components of this pathway have even been directly implicated in tumor suppression in mammals, including humans. Therefore, the elucidation of mechanisms behind inhibition of tumor growth in C. elegans likely will benefit similar studies in mammals, and identify new potential anti-cancer therapeutic targets and compounds. [unreadable] [unreadable] [unreadable]