My research investigates the molecules that cancer cells use to interact with neighboring cells and tissues. Studies have shown that tumor growth and progression are strongly influenced by the cells that surround them, but little is known about the molecules that participate in this malignant molecular exchange. Part of the challenge is determining "who said what"-- particularly when most cells use the same basic molecules to communicate. To separate the signal from the noise, I have engineered melanoma cells whose small molecules can be uniquely identified by mass using a bioanalytical technique known as mass spectrometry. Notably, with mass spectrometry, thousands of small molecules can be measured simultaneously with an approach called metabolomics, which provides a quantitative readout of cellular biochemistry. Now, using an innovative metabolomics system I developed for analyzing small molecules collected from living tissues-- in combination with biochemical, genetic, and cell biological techniques-- I will characterize the crosstalk that takes place in an animal injected with these engineered cancer cells. This work will expand our understanding of tumor biology and potentially provide novel avenues for therapy. The technique will also provide a new way to study cell-cell communication in a living organism and explore how this signaling goes awry in a host of diseases from cancer to infection.