Affiliations: Center for Structural Biology and Bioinformatics, Laboratory for the Structure and Function of Biological Membranes, Campus Plaine CP206/02, Université Libre de Bruxelles, B-1050 Brussels, Belgium
Correspondence:
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Corresponding author: Dr. Erik Goormaghtigh, Center for Structural Biology and Bioinformatics, Laboratory for the Structure and Function of Biological Membranes, Campus Plaine CP206/02, Université Libre de Bruxelles, Bld du Triomphe 2, CP206/2, B1050 Brussels, Belgium. Tel.: +32 2 650 53 86; Fax: +32 2 650 53 82; E-mail: egoor@ulb.ac.be.
Abstract: BACKGROUND:It is now recognized that tumor cells can actively alter their microenvironment and that this remodelled microenvironment can subsequently play a critical role in cancer progression and influence therapeutic responses. To date, the molecular heterogeneity within a 3D cancer cell colony and its influence on the extracellular matrix have not been studied by infrared imaging. OBJECTIVE:The objective of this study is to investigate by mid-infrared imaging 3D Matrigel-embedded colonies of pure MCF-7 human mammary adenocarcinoma cell line and the surrounding microenvironment after undergoing formalin fixation and paraffin embedding (FFPE). METHODS:In order to better reproduce the procedure used for preservation and storage of clinical tissue specimens for pathologic analysis, 7- and 10-day MCF-7 colonies embedded and grown in Matrigel were FFPE-treated; 4-µm-thick sections were cut, mounted on barium fluoride window and deparaffinized. The Fourier transform infrared (FTIR) images of 4096 spectra were collected in transmission mode using a FPA-based FTIR imaging system. They were pre-processed and analysed by principal component and K-mean cluster analyses. RESULTS:At 1654 cm−1 and 1234 cm−1, the intensity of absorption in the colonies is significantly higher than in Matrigel. It can be also noted, on the one hand, that there is a spectral heterogeneity in the intracolonial distribution of the absorbances at 1654, 1644, 1640 and 1634 cm−1 (Amide I range) possibly due to changes in protein secondary structures. On the other hand, we observe that Matrigel close to MCF-7 colonies appears altered with respect to more distant Matrigel matrix. CONCLUSIONS:FTIR imaging allowed us to highlight changes in the chemical content in MCF-7 colonies and their direct vicinity in Matrigel-embedded 3D cultures.
Keywords: FTIR imaging, 3D cell culture, extracellular matrix
