Metastasis is responsible for as much as 90% of cancer-associated mortality; yet progress has remained slow in developing effective drugs either specifically targeting metastasis or targeting cells with metastatic potential. Although thee are numerous studies showing the migratory potential of metastatic cells and relating metastasis to the biology of the epithelial-mesenchymal transition (EMT), little is known about how tumor cells engage this fundamental cellular program. Recently, we have described a new non-canonical Wnt pathway involving signals through Wnt5-Frizzled2 (Fzd2) that drives EMT, cellular migration, invasion in vitro and metastasis of human hepatocellular carcinoma cells as xenografts in mouse. Using focused proteomic approaches, we delineated the Fzd2 signaling pathway in a panel of metastatic cancer cell lines, identifying several novel signaling proteins downstream of Fzd2, including Fyn, Stat3, Axl and Pyk2. Thus far, these efforts have yielded information about individual proteins in Fzd2 signaling required for Fzd2-mediated cell migration; they have been less successful at providing mechanistic understanding of how this pathway drives the metastatic phenotype. Expression of Fzd2 in epithelial cells such as Huh7 and Dld1 causes increased motility and morphological changes triggering an EMT program. Preliminary data has shown that both Axl and Pyk2 are downstream of Fzd2 and affect Fzd2-mediated cell migration. Further, Axl and Pyk2 have been previously shown to affect both tumor growth and metastasis. With our data showing neutralizing anti-Fzd2 antibodies can strongly block metastasis in mouse xenograft, we were able to suggest that Fzd2-mediated EMT and metastasis may in part be regulated by Axl and Pyk2 kinases. I propose to address this by multiplex biochemical measurement, cellular phenotypic response assays and in vivo metastasis measurement to: (1) provide more complete information on how proteins in the Fzd2 network are connected and; (2) determine how the flow of information in the pathway drives enhanced cell migration and EMT. Overall, our analysis of the Fzd2 signaling network should highlight critical nodes and pathways that are linked to metastatic phenotypes especially increased motility and EMT. Equally important, my overall approach has the potential to guide future efforts to develop targeted therapies for metastatic cancer. My long-term goal is to develop a mechanistic and predictive understanding of signal transduction pathways driving the conversion of local tumors into metastatic ones by generating network-level and mechanistic models of the changes in signal transduction processes that accompany the EMT as part of metastatic transformation.
Wnt-Frizzled signaling plays a critical role in embryonic development and aberrant activation of this network has been broadly implicated in multiple types of cancers including colorectal and liver cancers. I propose a hypothesis-driven approach that uses multiplex proteomics coupled with phenotypic measurements to gain insight into how components of Frizzle2 signaling interconnect and how these connections regulate metastatic phenotypes. The results of such a combined approach will provide new insight into Frizzled signaling and could aid future efforts to develop targeted therapies for metastatic cancers.
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| Arang, Nadia; Kain, Heather S; Glennon, Elizabeth K et al. (2017) Identifying host regulators and inhibitors of liver stage malaria infection using kinase activity profiles. Nat Commun 8:1232 |
