NanoLC-MS coupling of liquid microjunction microextraction for on-tissue proteomic analysis

- Automatic microextraction coupled to LC-MS can be setup and allow for Shotgun Microproteomics to be performed.
- Regions as small as 250 μm corresponding to about 300-600 cells were extracted, yielding > 500 protein group identifications.
- This strategy allow for identification of proteins content within the ROIs determined by MALDI MSI.
- Regulated factors of serous ovarian cancers identified validate the strategy.

Mass spectrometry (MS)-based microproteomics on localized regions of tissue sections was achieved by direct coupling of liquid microjunction microextraction with a nanoscale liquid chromatography-tandem MS, resulting in the identification of > 500 protein groups from a region as small as 250 μm in diameter representing only a few hundred of cells. The method was applied on the examination of benign and tumor regions initially defined by imaging mass spectrometry (IMS) analysis of a consecutive high grade serous ovarian tumor tissue section. Results identified the higher abundance of eukaryotic translation initiation factors eIF4A, its isoform eIF4A2, and eIF5A and its isoform eIF5A2, and lower abundance of actin-binding proteins OBSCN, TAGLN and CNN3 on tumor regions, concomitant with previous findings. This demonstrates the use of the method for downstream characterization of distinct regions identified by IMS. This article is part of a Special Issue entitled: MALDI Imaging, edited by Dr. Corinna Henkel and Prof. Peter Hoffmann.