The interface of neurons and cancer

Project Summary The F99 portion of this proposal investigates the role of the brain enriched E3 ubiquitin ligase TRIM9 in melanoma progression. The K00 portion of this proposal investigates the interface of tumors and neurons, and how this interface influences cancer progression. Tumors are composed of multiple cell types and heterogenous cancer

cells. Cellular heterogeneity may be attributed to the dedifferentiation of cancerous cells, where characteristics of their differentiated states are lost, and new ones acquired. Melanoma, a cancer of melanocytes, cells derived from the neural crest, has been suggested to have undergone dedifferentiation. Interestingly, the brain-enriched E3

ubiquitin ligase TRIM9 is highly expressed in aggressive melanoma patient samples and multiple melanoma cell lines. Intriguingly, neurons, which also express TRIM9, are also derived from the neural crest. The Gupton lab identified TRIM9 as a potent regulator of exocytosis, actin dynamics, and directed axon navigation in developing

neurons. The lab found that TRIM9 negatively regulates the actin polymerase VASP via non-degradative ubiquitination and negatively regulates exocytosis by preventing SNARE complex formation. My preliminary data suggest that TRIM9 modulates focal adhesion morphology and number, cell size, random migration, directed

migration in response to extracellular stiffness, proliferation, and protease secretion in melanoma. In addition, preliminary TRIM9 immunoprecipitation mass spectrometry experiments identified several potential protein interactors that regulate focal adhesion dynamics, cell cycle progression, and trafficking in melanoma. The goal

of this predoctoral training proposal is to define the role of TRIM9 in focal adhesion dynamics, migration, and exocytosis in vitro and tumor growth and metastasis in vivo in melanoma. I will use a combination of cell and molecular biology techniques, biochemistry, microscopy, and a mouse model of melanoma. The interaction

between cancerous cells and other cells in the tumor microenvironment has been suggested to influence tumor progression. In patients, innervated tumors are correlated with morbidity. In addition, neuronal activity in small cell lung cancer tumors increases proliferation and metastasis in mice. Although progress has been made in

delineating the mechanisms that underly cancer- nerve interactions resulting in increased tumorigenesis and poor prognosis, there is much yet to understand. The postdoctoral training proposal aims to identify mechanisms by which the reciprocal interactions between neurons and cancer cells increase tumor progression. To identify

mechanisms, I will use cellular and molecular biology techniques, biochemistry, and MS assays, gained in the F99 phase, in combination with neuroscience techniques, which I will gain in the K00 phase. Together, the predoctoral and postdoctoral work aim to answer how cellular phenotypes and cancer progression are affected

by either gaining the expression of a brain- enriched E3 ubiquitin ligase or interactions between neurons and cancerous cells in the tumor microenvironment.