Trace elements and cutaneous cancer

The mineral macro- and micro-elements are playing essential biological roles. Some are co-factors of enzymes or act as organizers of the molecular structures of the cell or have an important role in ionic transport while some could be even beneficial as anti-tumor agents. Their concentration in the organism is closely linked to the long-term dietary intake, the environmental exposure, (e.g. cumulative exposure to chemicals from industrial sources could increase the incidence of skin cancer) and the health profile of the concerned subject. The research objective consisted in the examination of the content levels of some micro- and macro-elements found in the tumor tissue of patients having skin cancer disease, namely basal cell carcinoma (BCC), squamous cell carcinoma (SCC), malignant melanoma (MM), as well as benign tumor nevi. The analytical method of proton induced X-ray emission (PIXE) was used. The skin samples were collected from 22 cancer patients, aged 32-88 years, 11 males and 11 females. Controls were health skin samples (histopathological diagnosis) from patients having skin cancer. The samples were freeze-dried and then mineralized for PIXE analysis, using nitric acid at 1200 deg C temperature. The internal standard (Yttrium) technique was used for quantitative determination. Thin targets were measured in vacuum using a 3 MeV proton beam delivered by the Van de Graaff Tandem accelerator of the Institute for Physics and Nuclear Engineering in Bucharest - Magurele. A collimated beam (of 3 mm diameter) bombarded the target oriented at an angle of 45 angle with respect to the beam direction. The beam current entering the scattering chamber was maintained at several nAs. The samples were typically irradiated for a collected charge of 10 μC. The emitted X-rays have been detected by a Canberra Ge(HP) detector with energy resolution of 180 eV / 5.9 keV placed perpendicularly to the beam direction. Data manipulation and storage were performed with a Canberra S100 counting system, based on an IBM personal computer. For efficiency calibration, samples of known concentrations prepared in our laboratory were used. To calculate elemental concentrations, the ratios of element/standard (Yttrium) peak areas, detector efficiency and X-ray attenuation in Be windows (reaction chamber and detector) as well as in air were taken into account. The results obtained for tumor samples were compared with those for normal samples (histopathological diagnosis) from patients having skin cancer (control group). In spite of large standard deviations, the present results put in evidence the following: - a large significant increase (within the error bars) of P, S and K concentrations in all tumor samples (ratios between 2.3 ± 0.7 and 9.1 ± 6.6); - a large increase of Ca and Zn concentrations in nevi (6.1 ± 3.3 and 2.3 ± 1.6, respectively), and of Fe concentrations in BCC, MM and nevi (6.2 ± 5.7, 3.3 ± 2.5 and 4.0 ± 1.6, respectively); some of these higher concentrations have been found previously, e.g. Zn in skin carcinoma, levels of Cl, Ti, Cr, Mn and Cu not significantly different (in the limits of rather large standard deviations of present results) in the tumor compared to control samples. The present preliminary results obtained for only a limited number of samples should be confirmed in more cases before reaching a definite conclusion. If higher concentration levels of P, S, K, Fe and possible Zn in tumor compared to normal tissue will be confirmed by future analyses, then this result is similar to that found for Mg. The element capture by the tumor is due to a greater need of it in the growing tumor tissue. As a result, a depletion of these elements in the healthy tissue possibly occurs. (authors)