Facile sample preparation for quantitative single-cell proteomics

Large numbers of cells are generally required for quantitative global proteome profiling due to the significant surface adsorption losses associated with sample processing. Such bulk measurement obscures important cell-to-cell variability (cell heterogeneity) and makes proteomic profiling impossible for rare cell populations, such as circulating tumor cells (CTCs) and early metastatic cells. Herein we report a facile mass spectrometry (MS)-based single-cell proteomics method that capitalizes on a MS-compatible nonionic surfactant, n-Dodecyl-β-D-maltoside, for greatly reducing the surface adsorption losses by ~20-fold for effective single-tube processing of single cells, thus significantly improving detection sensitivity for single-cell proteomic analysis. With standard MS platforms, the method allows for the first time precise, label-free, reliable quantification of hundreds of proteins from single human cells in a simple, convenient manner. When applied to a patient CTC-derived xenograft (PCDX) model, the method can reveal distinct protein signatures between primary tumor cells and early metastases to the lungs at the single-cell resolution. The approach paves the way for routine, precise quantitative single-cell proteomic analysis.