Investigation of the role and chemical form of iron in the ovarian carcinogenesis process

Background: Ovarian cancer is one of the most frequent types of gynaecological malignancy among women. Despite the advances in diagnostic techniques, ovarian tumours are still detected at a late stage, thus the survival rate is very low. Iron is an essential metal in the human body, yet its potential role in ovarian carcinogenesis is yet to be determined. The aim of this study was to check if iron oxidation state in tissue and cystic fluid can be treated as an indicator of the malignancy of the ovarian tumours. Another aspect of this study was to investigate the role of iron in carcinogenesis mechanism in ovarian tumour transformation.

Methods: Synchrotron radiation X-ray absorption near edge structure (SR-XANES) spectroscopy was used to analyze the human ovarian tumour tissues and cystic fluids of different types and grades of malignancy. Fresh, non-fixed, frozen samples were used to analyze the state of iron oxidation in all the biological materials. The samples were obtained from patients requiring surgical intervention. The High Energy X-ray Absorption Spectroscopy (XANES) measurements were performed at the beamline P65 at Petra III Extension, DESY - Deutsches Elektronen - Synchrotron.

Results: Fe XANES spectra were collected at selected points of a few different regions of the samples. For each specimen, an average of these points was probed. Having been measured, the spectra were compared with organic and inorganic reference materials. Also, the position of the absorption edge was calculated using the integration method. In all specimens, iron occurred in the oxidation states, Fe2+ and Fe3+, although the fraction of iron in the third oxidation state was substantial, especially in malignant cases. The results also show differences in the chemical form of iron in the tissue and cystic fluids of the same patient.

Conclusions: The cryo-XANES measurement carried out for ovarian cancer tissues and cystic fluids showed changes in the chemical form of iron between non-malignant and malignant tumours. For both types of sample can be observed that they contain iron on second and iron on third oxidation state. Moreover, the tendency was observed that malignant tumours of the ovary contain a larger fraction of iron in the second oxidation state compared to non-malignant ones.