title: Phosphoproteome analysis of formalin-fixed and paraffin-embedded tissue sections mounted on microscope slides.
abstract: Formalin-fixed and paraffin-embedded (FFPE) sections mounted on microscope slides are one of the largest available resources for retrospective research on various diseases, but quantitative phosphoproteome analysis of FFPE sections has never been achieved because of the extreme difficulty of procuring sufficient phosphopeptides from the limited amounts of proteins on the slides. Here, we present the first protocol for quantitative phosphoproteome analysis of FFPE sections by utilizing phase-transfer surfactant-aided extraction/tryptic digestion of FFPE proteins followed by high-recovery phosphopeptide enrichment via lactic acid-modified titania chromatography. We established that FFPE sections retain a similar phosphoproteome to fresh tissue specimens during storage for at least 9 months, confirming the utility of our method for evaluating phosphorylation profiles in various diseases. We also verified that chemical labeling based on reductive dimethylation of amino groups was feasible for quantitative phosphoproteome analysis of FFPE samples on slides. Furthermore, we improved the LC-MS sensitivity by miniaturizing nanoLC columns to 25 μm inner diameter. With this system, we could identify 1090 phosphopeptides from a single FFPE section obtained from a microscope slide, containing 25.2 ± 5.4 μg of proteins. This protocol should be useful for large-scale phosphoproteome analysis of archival FFPE slides, especially scarce samples from patients with rare diseases.
authors: Graduate School of Pharmaceutical Sciences, Kyoto University , Sakyo-ku, Kyoto 606-8501, Japan.
authors: Masaki
authors: M
authors: Wakabayashi
authors: Hiroki
authors: H
authors: Yoshihara
authors: Takeshi
authors: T
authors: Masuda
authors: Mai
authors: M
authors: Tsukahara
authors: Naoyuki
authors: N
authors: Sugiyama
authors: Yasushi
authors: Y
authors: Ishihama
mesh_terms: D000818:Animals; D002853:Chromatography, Liquid; D005557:Formaldehyde / Q000737:chemistry*; D051379:Mice; D008810:Mice, Inbred C57BL; D016612:Paraffin Embedding; D010750:Phosphoproteins / Q000378:metabolism*; D020543:Proteome; D053719:Tandem Mass Spectrometry; D016707:Tissue Fixation
chemical_list: D010750:Phosphoproteins; D020543:Proteome; D005557:Formaldehyde