High‐resolution imaging mass spectrometry reveals detailed spatial distribution of phosphatidylinositols in human breast cancer

Abstract

High-resolution matrix-assisted laser desorption ⁄ ionization imaging mass spectrometry (MALDI IMS) is an emerging application for lipid research that provides a comprehensive and detailed spatial distribution of ionized molecules. Recent lipidomic approach has identified several phospholipids and phosphatidylinositols (PIs) are accumulated in breast cancer tissues and are therefore novel biomarker candidates. Because their distribution and significance remain unclear, we investigated the precise spatial distribution of PIs in human breast cancer tissues using highresolution MALDI IMS. We evaluated tissues from nine human breast cancers and one normal mammary gland by negative ion MALDI IMS at a resolution of 10 lm. We detected 10 PIs with different fatty acid compositions, and their proportions were remarkably variable in the malignant epithelial regions. Highresolution imaging enabled us to discriminate cancer cell clusters from the adjacent stromal tissue within epithelial regions; moreover, this technique revealed that several PIs were specifically localized to cancer cell clusters. These PIs were heterogeneously distributed within cancer cell clusters, allowing us to identify two different populations of cancer cells that predominantly expressed either PI(18:0 ⁄ 18:1) or PI(18:0 ⁄ 20:3). Tracing the expression level of PIs during cancer cell progression suggested that the latter population is associated with the invasion. Our study documents a novel model for phospholipid analysis of breast cancer tissues by using high-resolution MALDI IMS and identifies candidate PIs that can describe a specific phenotype of cancer cells. (Cancer Sci 2013; 104: 1372-1379 S ince Warburg's report on the upregulation of glycolysis and the increase in lactate production in cancer cells, (1) cancer-related metabolic processes have been studied intensively.(2) In terms of lipid metabolism, de novo fatty acid synthesis is frequently upregulated in cancer cells, even in the early stages of cancer progression.(2,3) This "reprogramming" of lipid metabolism could be associated with the proliferation, membrane fluidity, and apoptosis of cancer cells by affecting membrane lipid remodeling.(3) Recent studies demonstrated the accumulation of several phospholipids in breast cancer tissues and their association with sex hormone receptor expression, tumor grade, and prognosis. (4,5) Mass spectrometry (MS) is often used to investigate phospholipid profiles in living materials, and MALDI is the common ionization technique used for MS analysis. Matrixassisted laser desorption ⁄ ionization imaging mass spectrometry (MALDI IMS) is a new modality that facilitates the acquisition of mass spectra directly from tissue specimens and provides reconstructed density maps of detected ions.(6) In contrast to conventional MS analysis, which requires lipid extraction, MALDI IMS does not destroy the histological structures of living materials, and the acquired mapping images can be compared with the corresponding histological images. (7) Consequently, MALDI ...

Advances in Lipidomics for Cancer Biomarkers Discovery

“…Results showed that several PIs were specifically localized into cancer cell clusters, with a heterogeneous distribution, which identified two different populations of cancer cells: the first predominantly expressed PI 18:0/18:1, the second PI 18:0/20:3. Moreover, the latter population was associated with tumor invasion [54]. …”

Phospholipids as cancer biomarkers: Mass spectrometry‐based analysis

“…PC levels and total choline-containing PL metabolite levels were found to be increased in human breast cancer epithelial cells (Williams & Maunder, 1993). PI levels were also increased in some breast, lung, ovarian, prostate, and gastric cancer tissues (Ringel et al, 2001;Altomare et al, 2004;Dill et al, 2009;Yan et al, 2009;Kawashima et al, 2013;Liao et al, 2013). PIs involve the PI3kinase pathway, which regulates many cellular functions, including lipid metabolism, which is frequently mutated or activated in breast cancer tissues (Miller, Balko, & Arteaga, 2011;Network, 2012).…”

Assessment of amiodarone-induced phospholipidosis in chimeric mice with a humanized liver

“…IMS was previously used to analyze intracellular phospholipids (Shimma et al, 2007;Snel and Fuller, 2010;Miyamura et al, 2011;Kawashima et al, 2013;Goto et al, 2014).…”

“…Buck et al (2015) and Groseclose et al (2015) reported localization of SN-38, which is an active metabolite of a colon cancer drug, and deposition of dabrafenib in renal tubules from a toxicological study, respectively. Furthermore, a comparison of endogenous substrates between normal and tumorous tissues (Shimma et al, 2007;Kawashima et al, 2013;Goto et al, 2014), and changes in the endogenous substrates in response to drugs were also examined by IMS (Sun et al, 2016). Therefore, it is possible to evaluate susceptibility to DIPL by distinguishing mouse and human hepatocyte regions on the liver slices prepared from chimeric mice after the administration of amiodarone and analyzing hepatic localization of amiodarone, desethylamiodarone, and PhCs by IMS.…”