Novel Proteomic Methodology Used to Characterize Sarcoma Phosphoproteins

A novel proteomic approach was used to characterize the entire family of phosphotyrosine proteins present in sarcomas, relatively rare forms of cancer that are derived from bone, fat, muscle, or vascular tissues.

Despite the fact that protein phosphorylation plays a significant role in a wide range of cellular processes and is commonly disrupted in diseases such as cancer, the pattern of tyrosine phosphorylation in sarcomas has not been studied thoroughly. To understand better the signaling pathways active in sarcomas, investigators at Moffitt Cancer Center (Tampa, FL, USA) examined global tyrosine phosphorylation in sarcoma cell lines and human tumor samples. Antiphosphotyrosine antibodies were used to purify tyrosine-phosphorylated peptides, which were then identified using liquid chromatography and tandem mass spectrometry.

Results published in the March 29, 2012, online edition the Journal Cancer Research identified 1,936 unique tyrosine phosphorylated peptides, corresponding to 844 unique phosphotyrosine proteins. In sarcoma cells alone, peptides corresponding to 39 tyrosine kinases were found. Four of 10 cell lines demonstrated dependence on tyrosine kinases for growth and/or survival.

“Tyrosine kinases play an important role in controlling the hallmarks of cancer, and they have a proven track record as druggable targets for cancer treatment,” said senior author Dr. Eric B. Haura, professor of thoracic oncology at Moffitt Cancer Center. “Our goal was to produce a “landscape” of tyrosine phosphorylated proteins and tyrosine kinases prioritized for subsequent functional validation. In our study, we identified numerous tyrosine kinases that can be important for cellular signaling in human sarcomas that could drive the natural progression of sarcoma and, therefore, could be targeted by small molecule inhibitors aimed at altering sarcoma progression.”

“Sarcomas are rare, diverse malignancies that arise from connective tissues,” said Dr. Haura. “We hypothesized that we could identify important proteins that drive the growth and survival of these poorly understood sarcomas using an approach to characterize signaling proteins using mass spectrometry. We think this approach could hold promise in profiling tumors directly from patients and can complement existing genetic data on sarcomas. Our results show this is feasible in tumor tissues, and we hope to advance this further by directly studying additional tumors from sarcoma patients.”

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