Determination of Changes in Sulphur Oxidation States in Prostate Cancer Cells

Abstract

Prostate cancer cell lines along with selected organic and inorganic compounds used as references were studied with sulphur K-edge X-ray absorption near edge structure spectroscopy. The experiment was performed at the SUL-X beamline of the synchrotron radiation source ANKA, Karlsruhe (Germany). The sulphur was chosen for the studies because it is an essential biological element and out of many relevant factors, it is believed that it can take an important part in cancer transformations. The main goal was to determine which sulphur forms occur in prostate cancer cells and to compare these results with the ones obtained for non-cancerous cells. Therefore oxidation state of this element was analysed with S K-edge X-ray absorption near edge structure spectroscopy. The analysis of K-edge structure was done in order to investigate also the chemical structure of the elements neighbouring the central atom. The preliminary results from sulphur X-ray absorption near edge structure in prostate cancer cell line PC-3 and prostatic epithelial cell line PZ-HPV-7 (which was used as a control) show that there are various oxidation states of sulphur occurring in cells. The set of reference compounds with various sulphur oxidation states was used to establish the relation between the energy of the white line maximum and the oxidation state of sulphur. The equation of linear fit was used to compute the unknown oxidation state. In order to obtain a more detailed information the method of deconvolution of X-ray absorption near edge structure spectra was used. Experimental spectra were fitted with two Gaussian peaks and one arctangent step function. Fitting procedure was performed in Athena code and the deconvolution was used to assign the fraction of each sulphur form. The next step was to compare the results calculated for cancerous and non-cancerous cells. In this work, the first results of these studies are presented.

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

“…The mapping technique used allowed us to localize all of these forms in different morphological parts of the tissue that was impossible in case of point measurements. Our results are similar to the ones obtained for cultured prostate cancer cell lines, 22,23 but give a larger view since in case of tissue we are dealing with different cell types and also with the components of extracellular matrix that gives us more complex image of sulfur biochemistry in living organism. Results obtained in presented studies demonstrate the need to perform experiments on various biological systems-from cell lines cultured in artificial conditions to complex tissue samples from patients.…”

X‐Ray Spectroscopy on Biological Systems

“…Although the positions of the main features are identical in all spectra, they differ by the intensity. Preliminary analysis performed with the use of peak fitting method to determine the area under the peaks showed that the content of reduced sulfur forms does not vary much between cell lines but significant differences are present in the content of oxidized sulfur forms between cancerous and non-cancerous cells [6,8]. These preliminary results suggested that there might be changes in redox balance, and therefore, the detailed analysis by linear combination fit method was performed with the use of ATHENA software [61].…”

“…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.…”

“…All of the spectra are characterized by two strong features at energies 2472.4 and 2480.0 eV that, after the comparison with the spectra of reference compounds [6], were identified as the signature of reduced and oxidized forms of sulfur. Although the positions of the main features are identical in all spectra, they differ by the intensity.…”

“…X-ray spectroscopy is a powerful method giving the insight into the chemical and electronic structure of studied samples. Since twentieth century, it has been extensively used in a plethora or research fields starting from solid-state physics [1,2] and followed by chemical [3] and environmental sciences [4], archeological and art research [5], as well as biological and health studies [6]. The advantages of this technique is its elemental specificity and high penetration depth of probe X-rays resulting in the possibility to undertake in situ experiments that provide information about the sample under ambient/operational conditions, that is, direct observation of species at the molecular level in low (biological) concentrations without the need for preconcentration, extraction, or crystallization [7,8].…”