Identification of Biomarkers of Necrosis in Xenografts Using Imaging Mass Spectrometry

Abstract

Abstract. Xenografts are commonly used to test the effect of new drugs on human cancer. However, because of their heterogeneity, analysis of the results is often controversial. Part of the problem originates in the existence of tumor cells at different metabolic stages: from metastatic to necrotic cells, as it happens in real tumors. Imaging mass spectrometry is an excellent solution for the analysis of the results as it yields detailed information not only on the composition of the tissue but also on the distribution of the biomolecules within the tissue. Here, we use imaging mass spectrometry to determine the distribution of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and their plasmanyl-and plasmenylether derivatives (PC-P/O and PE-P/O) in xenografts of five different tumor cell lines: A-549, NCI-H1975, BX-PC3, HT29, and U-87 MG. The results demonstrate that the necrotic areas showed a higher abundance of Na + adducts and of PC-P/O species, whereas a large abundance of PE-P/O species was found in all the xenografts. Thus, the PC/PC-ether and Na + /K + ratios may highlight the necrotic areas while an increase on the number of PEether species may be pointing to the existence of viable tumor tissues. Furthermore, the existence of important changes in the concentration of Na + and K + adducts between different tissues has to be taken into account while interpreting the imaging mass spectrometry results.

Duramycin-porphyrin conjugates for targeting of tumour cells using photodynamic therapy

“…Though it was not shown directly in this study that there was an upregulation of PE on the cancer cell lines compared to their nor-mal counterparts, we have previously shown that PE expression occurs on a broad range of cancer cell lines [16]. Also it has been recently shown that PE was present in much higher abundance in xenografts formed from a number of different tumour types (lung, colon, pancreatic and glioblastoma) than in their normal tissue counterparts [54]. It is well established that duramycin binds to PE when exposed on the sur-face of cells and on the luminal surface of the endothelium [1,15,47,49,55].…”

Optimized Protocol To Analyze Changes in the Lipidome of Xenografts after Treatment with 2-Hydroxyoleic Acid

“…We have recently demonstrated 27 that necrotic tissue is enriched in Na + adducts. Consistently, a careful examination of the present results showed that the PC-Na + /PC-K + adduct ratio was sufficient to classify the areas according to cell viability.…”

“…This assignment to necrotic/viable was further confirmed by comparison with sequential sections stained with acridine orange, a dye widely used to assess DNA damage in many cell types. 27,49 …”

“…Identification of the necrotic areas was confirmed by comparison with sequential sections dyed with acridine orange (data not shown). 27 …”

“…12,20,21 On the other hand, lipids are good indicators of the metabolic stage of a cell, as they are involved in all major cellular processes: from cell growth to apoptosis. 22–26 Consequently, their distribution inside the xenograft may give invaluable information about the viability of the cells 27 and on the potential effect of a drug.…”