Diseased cells, such as cancer cells, release glycoproteins that can serve as biomarkers for diagnosis, disease progression and treatment efficacy. However, isolating the proteins released by specific cell types from those released by other, healthy cells can make it difficult to research and identify these useful biomarkers. A team of scientists from Francis Crick Institute and Imperial College London have developed a new glycoprotein tagging method based on bioorthogonal and click chemistry that allows only glycoproteins from specific cell lines to be identified and analyzed in the presence of other cell types.
While researchers can perform experiments analyzing proteins from only one cell type, these monoculture experiments are not representative of the real life scenarios where multiple cell types interact and influence one another’s behavior, explained Ben Schumann, the lead author of the study. In order to examine glycoproteins from one cell line in the presence of various other cell lines, the researchers created an artificial biosynthetic pathway that would cause only cells transfected with this pathway to release tagged glycoproteins. With this pathway in place, bioorthogonal tags attached to sugar molecule precursors are incorporated into the transfected cells’ glycoproteins through click reactions. Carolyn Bertozzi from Stanford University, one of the recipients of this year’s Nobel Prize in Chemistry for the development of bioorthogonal and click chemistry, is a co-author on the study.
The method, called Bio-Orthogonal Cell line-specific Tagging of Glycoproteins (BOCTAG), was tested in both co-cultures containing transfected breast cancer cells and in mice with tumors containing the transfected cells. The researchers successfully tagged proteins from particular cancer cells, which could be visualized via fluorescence microscopy as well as used to facilitate annotation of cell-specific glycosylation sites in mass spectrometry-glycoproteomics analyses, the authors wrote. This technique could help further understanding of how cancer cells interact with other cells in the body and help to discover new glycoprotein biomarkers. This study was published in Nature Communications.
“In this study, we looked at proteins made by cancer cells, but our method could also be used in other fields including immunology or the study of infectious disease,” said first author Anna Cioce, a postdoctoral training fellow at the Francis Crick Institute. “It could also be used to better understand disease biology, including how tumour cells change as a result of complex interactions in the body.”
The team plans to continue developing the BOCTAG method and use it to learn more about how cells modulate their protein production based on their environment, said Schumann.