Elevation of sulfatides in ovarian cancer: An integrated transcriptomic and lipidomic analysis including tissue-imaging mass spectrometry

Abstract

BackgroundSulfatides (ST) are a category of sulfated galactosylceramides (GalCer) that are elevated in many types of cancer including, possibly, ovarian cancer. Previous evidence for elevation of ST in ovarian cancer was based on a colorimetric reagent that does not provide structural details and can also react with other lipids. Therefore, this study utilized mass spectrometry for a structure-specific and quantitative analysis of the types, amounts, and tissue localization of ST in ovarian cancer, and combined these findings with analysis of mRNAs for the relevant enzymes of ST metabolism to explore possible mechanisms.ResultsAnalysis of 12 ovarian tissues graded as histologically normal or having epithelial ovarian tumors by liquid chromatography electrospray ionization-tandem mass spectrometry (LC ESI-MS/MS) established that most tumor-bearing tissues have higher amounts of ST. Because ovarian cancer tissues are comprised of many different cell types, histological tissue slices were analyzed by matrix-assisted laser desorption ionization-tissue-imaging MS (MALDI-TIMS). The regions where ST were detected by MALDI-TIMS overlapped with the ovarian epithelial carcinoma as identified by H & E staining and histological scoring. Furthermore, the structures for the most prevalent species observed via MALDI-TIMS (d18:1/C16:0-, d18:1/C24:1- and d18:1/C24:0-ST) were confirmed by MALDI-TIMS/MS, whereas, a neighboring ion(m/z 885.6) that was not tumor specific was identified as a phosphatidylinositol. Microarray analysis of mRNAs collected using laser capture microdissection revealed that expression of GalCer synthase and Gal3ST1 (3'-phosphoadenosine-5'-phosphosulfate:GalCer sulfotransferase) were approximately 11- and 3.5-fold higher, respectively, in the ovarian epithelial carcinoma cells versus normal ovarian stromal tissue, and they were 5- and 2.3-fold higher in comparison with normal surface ovarian epithelial cells, which is a likely explanation for the higher ST.ConclusionsThis study combined transcriptomic and lipidomic approaches to establish that sulfatides are elevated in ovarian cancer and should be evaluated further as factors that might be important in ovarian cancer biology and, possibly, as biomarkers.

Quantification of sulfatides and lysosulfatides in tissues and body fluids by liquid chromatography-tandem mass spectrometry

“…The C16:0, C16:0-OH, and C24:1 molecular species were higher in MLD plasma compared with human control plasma, whereas hydroxy fatty acids containing sulfatides were generally lower in MLD plasma. In addition to the molecular species shown in Table 3 , we observed in human plasma of sulfatides species separated according to hydrophobicity, which facilitates the study of changes in the tissue content of individual molecular species of sulfatides in conditions like insulin resistance and diabetes, cancer and metastasis, and multiple sclerosis ( 4,8,33,34 ). A consistent, although rather small, difference between sulfatide levels in plasma from age-matched wild-type ( +/+ ) C57BL/6J and ASA knockout mice (…”

“…Several methods have been used to quantify sulfatides, including TLC ( 19 ), HPLC ( 14,20 ), and, more recently, MS ( 4,13,15,(21)(22)(23)(24)(25). Here we describe a LC/MS/MS method to quantify sulfatides and their molecular species over a wide range of concentrations in normal and diseased tissues, plasma, and urine.…”

MALDI imaging MS reveals candidate lipid markers of polycystic kidney disease

“…Due to a mass usually below 1,500 Da, lipids are also amenable to MALDI-IMS in refl ectron mode, resulting in higher resolution and enabling fragmentation of selected ions for identifi cation by tandem mass spectrometry ( 25 ). Therefore, MALDI-IMS of tissue slices may be a useful tool for unbiased preclinical and clinical lipidomic studies ( 26 ). In contrast to the analysis of lipid extracts that requires time-consuming handling steps and where distinct classes of lipids might be depleted during certain purifi cation steps (for example, alkaline hydrolysis of phospholipids), MALDI-IMS facilitates exploratory data analysis of numerous lipid classes within their biological environment.…”

Methods in Comprehensive Mass Spectrometry-Based Measurement of Sphingolipids

“…revealed that the cerebellar cortex contained low levels of sphingomyelins and sulfatides, but high levels of gangliosides whereas the cerebellar peduncle contained large amounts of sulfatides and smaller quantities of gangliosides [27]. In another tissue imaging study, Liu and colleagues observed that sulfatides were mainly located in ovarian carcinoma epithelium, but not in histologically normal ovarian epithelium [28]. The development of MALDI tissue imaging greatly enhances the application spectrum of sphingolipidomic analysis.…”