Abstract 3981: In situ mass spectrometry using desorption electrospray ionization mass spectrometry (DESI-MS) can detect specific lipid profiles across breast cancer molecular subtypes
Authors: Andrade Victor P. , Santoro Adriana L. , Moretti Sabrina T. , Schwab Nicolas V. , Eberlin Marcos N. 
Published: July 2016

Abstract
INTRODUCTION Lipid profiling as a source for biomarkers identification is an evolving field with some enthusiastic results in cancer. Alterations on lipid metabolism have been increasingly recognized as a hallmark of cancer cells and may help to understand breast cancer carcinogenesis. Analytical chemistry and Pathology have been recently combined in the development of chemical microscopy using in situ mass spectrometry (MS) and may help to decipher breast cancer molecular initiation and progression. OBJECTIVE We aimed to use in situ Desorption Electrospray Ionization Mass Spectrometry (DESI-MS) to investigate lipid profiles across invasive breast cancer (IBC) molecular subtypes and related normal parenchyma (NBP) and ductal carcinoma in situ (DCIS). METHODS: We selected frozen samples from 9 IBC with various ER/PR/HER2 status (ER 0 to 100%, PR 0 to 90%, HER2 0 and 3+, Ki67 10 to 70%). Unstained slides obtained from frozen tissue at 10μm were submitted to DESI-MS analysis with no pretreatment and spatial resolution of 100μm. Molecular profiles (mass to charge [m/z] ratio versus signal intensity) were generated in triplicate directly from tissues to detect changes from areas of interest: IBC (and adjacent normal breast parenchyma and DCIS whenever present) regions were identified by a breast pathologist on HE-stained sequential slides. Experiment was conducted in full-scan mode and m/z range of 100-1200. DESI mass spectra were obtained using a Thermo ScientificTM Q ExactiveTM Hybrid Quadrupole Orbitrap Mass Spectrometer in the positive ion mode. The Biomap software was used to visualize the images and to export the spectrums to metaboanalyst, where the data were statiscally analyzed. RESULTS: The images obtained by lipid profiling presented a direct correlation with HE stained slides, with some ions m/z clearly overlaying areas of normal parenchyma, DCIS and invasive breast cancer. The unsupervised hierarchical clustering analysis showed all technical triplicates remained grouped. All NBP but one clustered together. Triple negative IBC and its related NBP formed a distinct cluster from all other ER+ samples. The ER+/HER2 + tumor segregated from other ER+/HER2- tumors. DCIS and IBC from ER+/PR+/HER2- tumor clustered together. The Ions with m/z 186.9 and m/z 303.2 were consistently related to NBP and IBC respectively. CONCLUSIONS: Chemical microscopy using DESI-MS is a powerful tool to identify specific lipid profiles across molecular subtypes of IBC and can contribute to understand breast cancer carcinogenesis.
Citation Format: Victor P. Andrade, Adriana L. Santoro, Sabrina T. Moretti, Nicolas V. Schwab, Marcos N. Eberlin. In situ mass spectrometry using desorption electrospray ionization mass spectrometry (DESI-MS) can detect specific lipid profiles across breast cancer molecular subtypes. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3981.