Investigating the Distribution of Chemical Forms of Sulfur in Prostate Cancer Tissue Using X-ray Absorption Spectroscopy

Abstract

The use of synchrotron radiation may shed more light on the study of prostate cancer, one of the leading diseases among men. In the presented study the microbeam setup at the PSI Swiss Light Source combined with fluorescence detected X-ray absorption spectroscopy (XAS) was applied to determine two-dimensional (2D) imaging of distributions of various chemical sulfur forms in prostate cancer tissue sections, since sulfur is considered important and essential in cancer progression. The research focused on prostate tissues obtained during routine prostatectomies on patients suffering from prostate cancer.Our previous studies using μ-XAS point measurements on prostate cancer cell lines showed the differences in fractions of various forms of sulfur between cancerous and non-cancerous cells. Therefore, in this experiment the chosen areas of prostate cancer tissues were scanned to get the full picture of the chemical composition of tissue, which is highly heterogeneous. The incident X-ray beams of energies tuned to spectroscopic features of the near-edge region of sulfur K-edge absorption spectra were used to provide contrast between chemical species presented in the tissue. Next, the relative content of the three main sulfur forms, found in biological systems, was calculated and the results are presented in a form of 2D color maps. These maps are correlated with the microscopic histological image of the scanned area.The main findings show that sulfur occurs in prostate tissue mainly in reduced form. The oxidized form of sulfur is present mostly in prostatic stroma, while sulfur in intermediate oxidation state is present in trace amount.

X‐Ray Spectroscopy on Biological Systems

“…Ideal experimental method to identify such changes should be highly sensitive, specific, and characterized by as minimal as possible sample manipulation. The studies presented in this section take advantage of X-ray spectroscopy to study sulfur species in prostate cancer cell lines and tissue [6,8,55,56]. Sulfur is a key element in human organism.…”

“…Our experiment [56] was performed on the tissue sections obtained during routine prostatectomies that were in a form of 15-μm-thick air-dried slices placed on Mylar foil. The first step was to measure full XAS spectra in few different points on the tissue in order to establish the value of incidence energies that should be used in XAS imaging.…”

“…Spectra 1, 3, and 4 are measured in nodular part while spectrum 2 in stroma. Reproduced from elsewhere with permission [56].…”

“…(a-c) Samples derived from three different patients diagnosed with prostate cancer undergoing prostatectomy. Reproduced from elsewhere with permission[56].…”

Soft X-ray Fluorescence and Near-Edge Absorption Microscopy for Investigating Metabolic Features in Biological Systems: A Review

“…Besides the proteogenic function, cysteine is a precursor of many biologically important molecules, such as the powerful oxidant glutathione and coenzyme A, an integral part of lipid and glucose metabolism. In pathology, it is considered essential in prostate cancer progression where, in particular, oxidative stress leads to continuous damage of critical cellular constituents, such as proteins, nucleotides, lipids, and metabolites [ 17 ].…”