Spatial characterisation of β-catenin-mutated hepatocellular adenoma subtypes by proteomic profiling of the tumour rim.

Background & Aims: Hepatocellular adenomas (HCAs) are rare, benign, liver tumours classified at the clinicopathological, genetic, and proteomic levels. The β-catenin-activated (b-HCA) subtypes harbour several mutation types in the β-catenin gene ( Methods: Using mass spectrometry imaging, genetic, and proteomic analyses combined with laser capture microdissection, we compared the tumour centre with the tumour rim and with adjacent non-tumoural tissue. Results: The tumour rim harboured the same mutation as the tumour centre, meaning both parts belong to the same tumour. Mass spectrometry imaging showed different spectral profiles between the rim and the tumour centre. Proteomic profiling revealed the significant differential expression of 40 proteins at the rim compared with the tumour centre. The majority of these proteins were associated with metabolism, with an expression profile comparable with a normal perivenous hepatocyte expression profile. Conclusions: The difference in phenotype between the tumour centres and tumour rims of exon 3 S45-mutated b-HCA and exon 7/8-mutated b-HCA does not depend on Impact and implications: Tumour heterogeneity was revealed in β-catenin-mutated hepatocellular adenomas (b-HCAs) via the differential expression of glutamine synthase at tumour rims. The combination of several spatial approaches (mass spectrometry imaging, genetic, and proteomic analyses) after laser capture microdissection allowed identification of a potential role for peripheral venous drainage underlying this difference. Through this study, we were able to illustrate that beyond a mutational context, many factors can downstream regulate gene expression and contribute to different clinicopathological phenotypes. We believe that the combinations of spatial analyses that we used could be inspiring for all researchers wanting to access heterogeneity information of liver tumours.