MALDI imaging mass spectrometry to characterize a hepatocellular carcinoma arising in a dysplastic nodule. MALDI Imaging-Massenspekrometrie zur Charkterisierung eines hepatozellulären Karzinoms in einem dysplastischen Knoten

Aim: We present the case of a 60-year-old male patient, who was transplanted for alcohol-induced liver cirrhosis. During pathological work-up a 1.4 cm measuring lesion was detected. Histology revealed a high-grade dysplastic nodule with nodule-in-nodule progression to hepatocellular carcinoma (HCC). We aimed at the identification of differentially expressed peptides during stepwise hepatocarcinogenesis in this patient using MALDI imaging mass spectrometry. Method: The tumor-containing liver tissue was sectioned and stained with hematoxylin and eosin. A serial section was subjected to in situ trypsin digestion at 37 °C for 1.5 h in a humidity chamber, following deparaffination and antigen retrieval. Trypsin (0.5µg/µl) was applied onto the sections by vibrational spraying (ImagePrep, Bruker Daltonik GmbH). Matrix solution (7 mg/ml in 50/50 acetonitrile /0.5% TFA) was deposited onto digested sections using the same devise. MALDI imaging data were acquired at a spatial resolution of 200 µm using an Autoflex Speed TOF/TOF system and visualized with FlexImaging software. Spectral analysis was performed with FlexAnalysis 3.3 and ClinProTools 3.3 software programs (Bruker Daltonik GmbH). Results: We detected several differentially expressed m/z ion peptides between non-tumorous surrounding liver, dysplastic nodule, and HCC. While some m/z values were unique for the HCC, but could not be identified in the area of the dysplastic nodule or the surrounding liver tissue, other m/z values were exclusively present in the dysplastic nodule and/or in the surrounding liver tissue but not in the area containing the HCC. Conclusion: Using MALDI imaging we successfully identified peptides differentially expressed between non-tumorous surrounding liver, dysplastic nodule, and HCC. Larger series are needed to evaluate whether these peptides or the corresponding proteins might serve as diagnostic markers in daily practice.