Regulation of the Selenocysteine Stress Response in Cancer Metastasis

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PROJECT SUMMARY The adaptations that metastasizing cancer cells undergo are not well understood, contributing to a lack of effective therapies, making metastasis the leading cause of cancer-related deaths. Genetic drivers of metastatic progression have not been identified, thus it is imperative to study the disease at the transcriptional and translational level where cells are able to make reversible adaptations that allow them to survive throughout the metastatic cascade. Our long-term goal is to find novel and targetable vulnerabilities in cancer metastasis by identifying these molecular and metabolic adaptations. Early work from our lab shows that metastasizing cells undergo high levels of oxidative stress. Selenocysteine, the 21st amino acid, is incorporated into a family of proteins that are involved in detoxifying reactive oxygen species and maintaining redox balance in the cell. Translation of selenoproteins under cellular stress is regulated by a single 2’-O-ribose methylation on the wobble uridine (Um34) of the selenocysteine tRNA (tRNASec), completed by an unknown methyltransferase. Using our lab’s patient-derived tumor model of melanoma metastasis, I will test the hypothesis that Um34 methylation is increased in metastasizing cells and that this modification increases cell survival under oxidative stress by regulating a subset of stress response selenoproteins. To address this question, I will utilize an established patient-derived melanoma model where metastasis is predictive of patient outcome in parallel with melanoma cell lines in vitro. In Aim 1, I will determine the functional role of Um34 in metastasis and the oxidative stress response. I will develop tools to measure Um34 levels and I will perturb the modification event by targeting related enzymes, tRNASec and selenium availability. In Aim 2, I will identify the unknown Um34 methyltransferase by testing a candidate protein and through targeted immunoprecipitation approaches. I will use mass spectrometry to quantify Um34 levels and identify related protein complexes. I will then characterize the selenocysteine stress response and through depletion of the identified methyltransferase, I will determine its functional role in metastasis and the oxidative stress response. This work will be completed at Weill Cornell Medicine where I will develop scientifically and professionally into an independent researcher. I will receive expert guidance throughout my project from my committee of world-renowned scientists whose expertise span the many fields covered in my proposal. Through this work I will master biochemical analytical techniques, modeling a complicated disease in vivo and clearly communicating my ideas and results – all of which will prepare me for a career as an independent investigator in academic science. Identifying novel targets in metastatic disease is an urgent therapeutic need and I believe that this work will not only find one, but expand the current understanding of how metastasizing cancer cells adapt and survive.