Spatial and molecular resolution of diffuse malignant mesothelioma heterogeneity by integrating label-free FTIR imaging, laser capture microdissection and proteomics

Our plain-English summary of Spatial and molecular resolution of diffuse malignant mesothelioma heterogeneity by integrating label-free FTIR imaging, laser capture microdissection and proteomics, by F. Großerueschkamp, T. Bracht, H.C. Diehl, et al (Scientific Reports, 2017).

The study

• Authors: F. Großerueschkamp, T. Bracht, H.C. Diehl, C. Kuepper, M. Ahrens, A. Kallenbach-Thieltges, A. Mosig, M. Eisenacher, K. Marcus, T. Behrens, T. Brüning, D. Theegarten, B. Sitek, K. Gerwert
• Journal: Scientific Reports
• Published: 2017;7:44829
• Cited by: 44 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Diffuse malignant mesothelioma (DMM) is a heterogeneous malignant neoplasia manifesting with three subtypes: epithelioid, sarcomatoid and biphasic. DMM exhibit a high degree of spatial heterogeneity that complicates a thorough understanding of the underlying different molecular processes in each subtype. We present a novel approach to spatially resolve the heterogeneity of a tumour in a label-free manner by integrating FTIR imaging and laser capture microdissection (LCM). Subsequent proteome analysis of the dissected homogenous samples provides in addition molecular resolution. FTIR imaging resolves tumour subtypes within tissue thin-sections in an automated and label-free manner with accuracy of about 85% for DMM subtypes. Even in highly heterogeneous tissue structures, our label-free approach can identify small regions of interest, which can be dissected as homogeneous samples using LCM. Subsequent proteome analysis provides a location specific molecular characterization. Applied to DMM subtypes, we identify 142 differentially expressed proteins, including five protein biomarkers commonly used in DMM immunohistochemistry panels. Thus, FTIR imaging resolves not only morphological alteration within tissue but it resolves even alterations at the level of single proteins in tumour subtypes. Our fully automated workflow FTIR-guided LCM opens new avenues collecting homogeneous samples for precise and predictive biomarkers from omics studies.

In plain English

This laboratory methods study tested a way to sort mesothelioma tissue by subtype without chemical stains, then analyse its proteins. The authors used infrared (FTIR) imaging and a computer classifier to map frozen tissue sections of diffuse malignant mesothelioma of the pleura parietalis and visceralis. They then used laser microdissection to cut out regions of the epithelioid and sarcomatoid subtypes for protein analysis. Against clinical diagnoses of 17 samples from 14 patients, all male and aged 36 to 83, subtype classification accuracy was 88%. Protein analysis of samples from nine patients found 142 proteins that differed in abundance between the two subtypes. Of these, 120 were more abundant in epithelioid tumours and 22 in sarcomatoid tumours. Calretinin was the most significant marker, and cytokeratins 5, 6, 8 and 19 were more abundant in epithelioid tumours. The study did not report the patients' asbestos exposure. The authors noted the sample set was small. They concluded that the method can resolve tumour and tissue heterogeneity for protein analysis.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory methods-development (proof-of-concept) study combining label-free FTIR imaging, laser capture microdissection and proteome analysis of human tumour tissue
• Who was studied: Diffuse malignant mesothelioma tissue of the pleura parietalis and visceralis, taken during surgery. Ethics approval came from Ruhr-University Bochum and University Duisburg-Essen, Germany; dates are not given. Classifier testing used 17 samples from 14 patients, all male, aged 36 to 83. Proteome analysis used epithelioid and sarcomatoid samples from nine patients: four sarcomatoid and six epithelioid DMMs. Colon tissue was used only to demonstrate the workflow.
• Exposure: Not studied. The article does not report the patients' asbestos exposure, fiber types or occupations. It compares tumour subtypes (epithelioid vs sarcomatoid), not exposures.
• Main results:
  • FTIR imaging classified mesothelioma subtypes with 88% accuracy relative to the clinical diagnoses of 17 samples from 14 patients
  • Proteome analysis identified 15,432 peptides, corresponding to 2,925 protein groups (3,317 proteins)
  • Of 142 proteins with significant differences in abundance between subtypes, 120 were more abundant in epithelioid tumours and 22 in sarcomatoid tumours
  • Calretinin was the most significant marker distinguishing epithelioid from sarcomatoid DMM (Table 1: p value 0.0004, fold change 22.4)
  • Cytokeratins 5, 6, 8 and 19 were more abundant in epithelioid DMMs, matching immunohistochemistry results
  • HYOU1, NDUFA8 and TGM1 were significantly overexpressed in epithelioid samples; COL6A1 was significantly overexpressed in sarcomatoid samples
  • In one case (La0086), the clinical diagnosis on an adjacent section was epithelioid DMM, but FTIR imaging classified it as biphasic with a majority of sarcomatoid cells
• The authors' conclusion: The authors concluded that FTIR-guided laser capture microdissection can effectively resolve tumour and tissue heterogeneity for proteome analysis of neoplastic tissue
• Limitations the authors state:
  • The sample set was small because mesothelioma is rare and heterogeneous
  • The subtype groups could not be made equal in size
  • The authors gave up some spatial resolution to shorten measurement time, because fresh tissue can degrade rapidly
  • The additional candidate marker proteins still need validation on a larger number of samples

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Epithelioid, Sarcomatoid, Biphasic Mesothelioma, Biomarker, Immunohistochemistry.

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