PAT-H-MS coupled with laser microdissection to study histone post-translational modifications in selected cell populations from pathology samples

Aberrations in histone post-translational modifications (hPTMs) have been linked with various pathologies, including cancer, and could represent not only useful biomarkers, but also suggest possible targetable epigenetic mechanisms. We have recently developed an approach, termed pathology tissue analysis of histones by mass spectrometry (PAT-H-MS), that allows performing a comprehensive and quantitative analysis of histone H3 PTMs from formalin-fixed paraffin-embedded pathology samples. Despite its great potential, the application of this technique is limited by tissue heterogeneity. In this study, we implemented the PAT-H-MS approach by coupling it with techniques aimed at reducing sample heterogeneity and selecting specific portions or cell populations within the samples, such as manual macrodissection and lased micro-dissection (LMD). When applied to the analysis of a small set of breast cancer samples, LMD- PAT-H-MS allowed detecting more marked changes between Luminal A and Triple Negative patients as compared with the classical approach.