MALDI MSI of MeLiM melanoma: Searching for differences in protein profiles.

Roman Guran,Vojtech Adam,Zbynek Heger,Ondrej Zitka,Lucie Vanickova,Sona Krizkova,Petr Michalek,Vratislav Horak,Roger Chammas

doi:10.1371/journal.pone.0189305

Roman Guran, Vojtech Adam + Show 7 more

Open Access

https://doi.org/10.1371/journal.pone.0189305

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Abstract

BackgroundTreatment of advanced cutaneous melanoma remains challenging, and new data on melanoma biology are required. The most widely accepted criteria for the prognostic evaluation of melanoma are histopathological and clinical parameters, and the identification of additional tumor markers is thus of paramount importance. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI), an important tool in cancer research, is useful for unraveling the molecular profile of melanoma.Methodology/Principal findingsIn this report, we used the melanoma-bearing Libechov minipig (MeLiM), a unique animal model that allows observation of the complete spontaneous regression of invasive cutaneous melanoma, to investigate i) the differences between melanoma and healthy skin protein profiles and ii) the proteins potentially involved in spontaneous regression. The MeLiM tissues were cryosected, histologically characterized, analyzed by MALDI MSI, and immunohistologically stained. Multivariate statistical analyses of the MALDI MSI data revealed ten relevant m/z ions, of which the expression levels varied significantly among the studied MeLiM tissues. These ion peaks were used to create mass ion images/maps and visualize the differences between tumor and healthy skin specimens, as well as among histologically characterized tissue regions.Conclusions/SignificanceProtein profiles comprising ten statistically significant mass ion peaks useful for differentiating cutaneous melanoma and healthy skin tissues were determined. Peaks at m/z 3044, 6011, 6140 and 10180 were overexpressed in melanoma compared with healthy skin tissue. More specifically, m/z 6140 was expressed at significantly (p < 0.05) higher levels in normally growing melanoma regions than in regions with early and late spontaneous regression. This study demonstrates the clinical utility of MALDI MSI for the analysis of tissue cryosections at a molecular level.

Highlights

Melanoma is one of the most aggressive forms of cancer, being responsible for 1.2% of all cancer deaths in the European Union
Fresh frozen melanoma tissues from two melanoma-bearing Libechov minipig (MeLiM) were analyzed using MALDI MSI, and the resulting data were compared with data from matching healthy skin tissues stored under the same conditions
The overexpression of S100-A6 in the of growing melanoma tissue (GMT) and early spontaneous regression (ESR) regions in MeLiM tissue confirms the findings of the abovementioned studies suggesting the use of calcyclin overexpression as an indicator of melanoma growth. This pilot study demonstrates that MALDI MSI can successfully visualize the spatial distribution of various proteins in melanoma and healthy skin tissue from MeLiM

Summary

Introduction

Melanoma is one of the most aggressive forms of cancer, being responsible for 1.2% of all cancer deaths in the European Union. Cancerous growth develops when unrepaired DNA damage to skin cells (most often caused by ultraviolet radiation from sunlight or tanning beds) triggers mutations that cause the skin cells to multiply rapidly and form malignant tumors [1]. Protein changes associated with the transition from melanocyte to atypia or dysplasia and to melanoma could be used to aid in diagnosis or to screen high-risk patients. Proteins associated with pathophysiology and malignant properties could be used to further classify melanoma, stratifying patients by risk of recurrence in order to better select surgical and adjuvant treatments [3]. Beyond the diagnostic and prognostic value in assessing melanoma progression, these protein signatures may provide valuable insights into the choice of optimal treatment strategies for individual patients. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI), an important tool in cancer research, is useful for unraveling the molecular profile of melanoma

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