Ratios of Selenium/Trace Element Contents in Prostate Gland as Carcinoma's Markers
Vladimir Zaichick1* and Sofia Zaichick2
1Radionuclide Diagnostics Department, Medical Radiological Research Centre, Russia
2Laboratory of Dr. Gabriela Caraveo Piso, Northwestern University, USA
Submission: March 07, 2017; Published: May 08, 2017
*Corresponding author: Vladimir Zaichick, Radionuclide Diagnostics Department, Medical Radiological Research Centre, 4, Korolyev St., MRRC,Obninsk 249036, Russia, Fax: +7 (495) 956 1440; Tel: +7 (48439) 60289; ; Email: vezai@obninsk.com
How to cite this article: Zaichick V, Zaichick S. Ratios of Selenium/Trace Element Contents in Prostate Gland as Carcinoma's Markers. J Tumor Med Prev. 2017; 1(2): 555556. DOI: 10.19080/JTMP.2017.01.555556
Abstract
The aim of the study was to evaluate whether significant changes in the prostatic tissue levels of ratios Se/trace element contents exist in the malignantly transformed prostate. Contents of Se and other 42 trace elements (Ag, Al, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cs, Dy, Er, Fe, Gd, Hg, Ho, La, Li, Mn, Mo, Nb, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Sm, Sn, Tb, Th, Ti, Tl, Tm, U, Y, Yb, Zn, and Zr) in normal (N, n=37, age range 41-87 years), benign hypertrophic (BPH, n=32, age range 56-78), and cancerous human prostate (PCa, n=60, age range 40-70) were investigated.The aim of the study was to evaluate whether significant changes in the prostatic tissue levels of ratios Se/trace element contents exist in the malignantly transformed prostate. Contents of Se and other 42 trace elements (Ag, Al, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cs, Dy, Er, Fe, Gd, Hg, Ho, La, Li, Mn, Mo, Nb, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Sm, Sn, Tb, Th, Ti, Tl, Tm, U, Y, Yb, Zn, and Zr) in normal (N, n=37, age range 41-87 years), benign hypertrophic (BPH, n=32, age range 56-78), and cancerous human prostate (PCa, n=60, age range 40-70) were investigated.
Measurements of trace element contents were performed using a combination of instrumental neutron activation analysis and inductively coupled plasma mass spectrometry. Then the levels of ratios Se/trace element contents in every sample were calculated. It was observed that the ratio to Se of Ag, Al, Au, B, Be, Bi, Br, Ce, Cr, Dy, Er, Fe, Gd, Ho, La, Li, Mn, Nd, Ni, Pb, Pr, Sb, Sm, Sn, Tb, Th, Ti, Tl, Tm, U, Y, Yb, and Zr mass fraction were significantly lower in cancerous tissues than in normal and BPH prostate. Finally, we propose to use the Se/Ag, Se/Al, Se/B, Se/Bi, Se/Cr, Se/Li, Se/Mn, Se/Sb, Se/Tl, and Se/Zr mass fraction ratios in a needle-biopsy core as an accurate tool to diagnose prostate cancer. Further studies on larger number of samples are required to confirm our findings and to investigate the impact of the trace element relationships on prostate cancer etiology.
Keywords: Trace elements; Trace element content ratios; Prostate; Benign prostatic hypertrophy; Prostatic carcinoma; Neutron activation analysis; Inductively coupled plasma mass spectrometry
Abbreviations: INAA-LLR: The Instrumental Neutron Activation Analysis with High Resolution Spectrometry Of Long-Lived Radionuclides; ICP-MS: The Inductively Coupled Plasma Mass Spectrometry; CRM: The Certified Reference Materials
Introduction
The prostate gland may be a source of many health problems in men past middle age, the most common benign prostatic hyperplasia (BPH), and prostatic carcinoma (PCa). BPH is a noncancerous enlargement of the prostate gland leading to obstruction of the urethra and can significantly impair quality of life. The prevalence of histological BPH is found in approximately 50-60% of males age 40-50 and greater than 90% of men over 70 years old [1,2]. In many Western industrialized countries, including North America, PCa is the most frequently diagnosed form of noncutaneous malignancy in males. Except for lung cancer, PCa is the leading cause of death from cancer [3-8]. Although the etiology of BPH and PCa is unknown, some trace elements have been highlighted in the literature in relation to the development of these prostate diseases [9-29].
Trace elements have essential physiological functions such as maintenance and regulation of cell function and signaling, gene regulation, activation or inhibition of enzymatic reactions, neurotransmission, and regulation of membrane function.Essential or toxic (mutagenic, carcinogenic) properties of trace elements depend on tissue-specific need or tolerance, respectively [30]. Excessive accumulation, deficiency or an imbalance of the trace elements may disturb the cell functions and may result in cellular degeneration, death and malignant transformation [30].Trace elements have essential physiological functions such as maintenance and regulation of cell function and signaling, gene regulation, activation or inhibition of enzymatic reactions, neurotransmission, and regulation of membrane function.Essential or toxic (mutagenic, carcinogenic) properties of trace elements depend on tissue-specific need or tolerance, respectively [30]. Excessive accumulation, deficiency or an imbalance of the trace elements may disturb the cell functions and may result in cellular degeneration, death and malignant transformation [30].
In earlier reported studies [31-69] significant changes of trace element contents in hyper plastic and cancerous prostate in comparison with those in the normal prostatic tissue were observed. In particular, it was shown that the average mass fraction of some trace elements in BPH were higher than normal levels, while those in adenocarcinoma were lower than in healthy prostatic parenchyma [60,61,66-68]. Obtained results formed the basis for a new method for differential diagnosis of BPH and PCa, the essence of which was to determine the ratios of chemical element contents changed in opposite directions during malignant transformation of prostate. For example, a significant informative value of Zn/Se content as a tumor marker for PCa diagnostics was shown by us [70]. Hence it is possible that besides Zn, the ratio of Se to other trace elements also can be used as tumor markers for distinguish between benign and malignant prostate.
Currently number of methods was applied for the measurement of chemical elements contents in samples of human tissue. Among these methods, the instrumental neutron activation analysis with high resolution spectrometry of long- lived radio nuclides (INAA-LLR) is a non-destructive and one of the most sensitive techniques. It allows measure the chemical element contents in few milligrams tissue without any treatment of sample. Nondestructive method of analysis avoids the possibility of changing the content of trace elements in the studied samples [71-74], which allowed for the first time to obtain reliable results. However, INAA-LLR allows only determine the mean mass fractions of 10-11 trace elements in the samples of normal and cancerous prostate glands [15,28]. The inductively coupled plasma mass spectrometry (ICP-MS) is more power analytical tool than INAA-LLR [18], but sample digestion is a critical step in elemental analysis by this method. In the present study two these analytical methods were used and the results, obtained for some trace elements by ICP-MS, were under the control of INAA-LLR data.
The present study had three aims. The main objective was to obtain reliable results about the 43 trace elements: Ag, Al, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cs, Dy, Er, Fe, Gd, Hg, Ho, La, Li, Mn, Mo, Nb, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Sm, Sn, Tb, Th, Ti, Tl, Tm, U, Y, Yb, Zn, and Zr contents in intact prostate of healthy men aged over 40 years and also in the prostate gland of age-matched patients, who had either BPH or PCa, combining in consecutive order non-destructive INAA-LLR with destructive ICP-MS method. The second aim was to calculate Se/trace element content ratios for every sample and compare the levels of these ratios in normal, hyper plastic, and cancerous prostate. The third and final aim was to evaluate the ratios of Se/trace element contents for diagnosis of prostate cancer. All studies were approved by the Ethical Committees of the Medical Radiological Research Centre, Obninsk.
Material and Methods
Samples
The patients studied (n=92) were hospitalized in the Urological Department of the Medical Radiological Research Centre (Obninsk, Russia). All of them were European-Caucasian, citizens of Moscow and Obninsk (a small city in a non-industrial region 105km south-west of Moscow). Trans rectal puncture biopsy of suspicious indurated regions of the prostate was performed for every patient, to permit morphological study of prostatic tissue at these sites and to estimate their chemical element contents. In all cases the diagnosis has been confirmed by clinical and morphological results obtained during studies of biopsy and resected materials. The age of 32 patients with BPH ranged from 56 to 78 years, the mean being 66±6 (M±SD) years. The 60 patients aged 40-79 suffered from PCa (stage T1-T4).Their mean age was 65±10 (M±SD) years.
Intact prostates (N) were removed at necropsy from 37 men aged 41-87 who had died suddenly. All deceased were European- Caucasian, citizens of Moscow. Their mean age was 55±11 (M±SD) years. The majority of deaths were due to trauma. Tissue samples were collected from the peripheral zone of dorsal and lateral lobes of their prostates, within 2 days of death and then the samples were divided into two portions. One was used for morphological study while the other was intended for chemical element analysis. A histological examination was used to control the age norm conformity, as well as to confirm the absence of micro adenomatosis and latent cancer [14,15,20,28].
Sample preparation
All tissue samples were divided into two portions. One was used for morphological study while the other was intended for trace element analysis. After the samples intended for trace element analysis were weighed, they were freeze-dried and homogenized. The sample weighing about 10mg (for biopsy materials) and 50-100mg (for resected materials) was used for trace element measurement by INAA-LLR. The samples for INAA-LLR were wrapped separately in a high-purity aluminum foil washed with double rectified alcohol before hand and placed in a nitric acid-washed quartz ampoule.
After INAA-LLR investigation, the prostate samples were taken out and used for ICP-MS method. The samples were decomposed in autoclaves; 1.5mL of concentrated HNO3 (nitric acid at 65%, maximum (max) of 0.0000005%Hg; GR, ISO, Merck) and 0.3mL of H2O2 (pure for analysis) were added to prostate tissue samples, placed in one-chamber autoclaves (Ancon- AT2, Ltd., Russia) and then heated for 3h at 160-200°C. After autoclaving, they were cooled to room temperature and solutions from the decomposed samples were diluted with deionized water (up to 20mL) and transferred to the plastic measuring bottles. Simultaneously, the same procedure was performed in autoclaves without tissue samples (only HNO3+H2O2+ deionized water), and the resultant solutions were used as control samples.
Instrumentation and methods
A vertical channel of a nuclear reactor was applied to determine the trace element mass fractions by INAA-LLR. The quartz ampoule with prostate samples and certified reference materials was soldered, positioned in a transport aluminum container, and exposed to a 24 hour neutron irradiation in a vertical channel with a neutron flux of 1.3.1013 n.cm'-2.s-1. Ten days after irradiation samples were reweighed and repacked. The samples were measured for period from 10 to 30 days after irradiation. The duration of measurements was from 20 min to 10 hours subject to pulse counting rate. The gamma spectrometer used for INAA-LLR included the 100cm3 Ge (Li) detector and online computer-based multichannel analyzer. The spectrometer provided a resolution of 1.9keV on the 60Co 1332keV line. Other details of the INAA-LLR analysis were presented in our previous publication [15].A vertical channel of a nuclear reactor was applied to determine the trace element mass fractions by INAA-LLR. The quartz ampoule with prostate samples and certified reference materials was soldered, positioned in a transport aluminum container, and exposed to a 24 hour neutron irradiation in a vertical channel with a neutron flux of 1.3.1013 n.cm'-2.s-1. Ten days after irradiation samples were reweighed and repacked. The samples were measured for period from 10 to 30 days after irradiation. The duration of measurements was from 20 min to 10 hours subject to pulse counting rate. The gamma spectrometer used for INAA-LLR included the 100cm3 Ge (Li) detector and online computer-based multichannel analyzer. The spectrometer provided a resolution of 1.9keV on the 60Co 1332keV line. Other details of the INAA-LLR analysis were presented in our previous publication [15].
An ICP-MS Thermo-Fisher "X-7" Spectrometer (Thermo Electron, USA) was used to determine the content of trace elements by ICP-MS. The element concentrations in aqueous solutions were determined by the quantitative method using multi elemental calibration solutions ICP-MS-68A and ICP- AM-6-A produced by High-Purity Standards (Charleston, SC 29423, USA). Indium was used as an internal standard in all measurements. Information detailing with the ICP-MS method used was presented in our previous publication [18].
Certified reference materials
For quality control, ten subsamples of the certified reference materials (CRM) IAEA H-4 Animal muscle and IAEA HH-1 Human hair from the International Atomic Energy Agency (IAEA), and also five sub-samples INCT-SBF-4 Soya Bean Flour, INCT-TL-1 Tea Leaves and INCT-MPH-2 Mixed Polish Herbs from the Institute of Nuclear Chemistry and Technology (INCT, Warszawa, Poland) were analyzed simultaneously with the investigated prostate tissue samples. All samples of CRMs were treated in the same way as the prostate samples. Detailed results of this quality assurance program were presented in earlier publications [15,18].
Computer programs and statistic
A dedicated computer program for INAA mode optimization was used [75,76]. All prostate samples for INAA-LLR were prepared in duplicate and mean values of trace element contents were used in final calculation. For elements investigated by both INAA-LLR and ICP-MS methods the mean of all results was used. Using the Microsoft Office Excel software Se/trace element contents for each trace element in every sample were calculated. Then arithmetic mean±standard error of mean was calculated for trace element mass fraction and for ratios of Se/ trace element mass fraction in normal, benign hyper plastic and cancerous prostate. The difference in the results between BPH and N, PCa and N, as well as PCa and BPH was evaluated by parametric Student's t-test and non-parametric Wilcoxon- Mann-Whitney U-test. Values of p<0.05 were considered to be statistically significant. For the construction of "individual data sets for Se/trace element mass fraction ratios in normal, benign hypertrophic and cancerous prostate” diagrams the Microsoft Office Excel software was also used.
Results
M: Arithmetical Mean; SD: Standard Deviation, a: Information Values
M: Arithmetical Mean; SD: Standard Deviation, a: Information Values
M: Arithmetic Mean, SEM: Standard Error of Mean, *Titanium tools were used for sampling and sample preparation.
Table 1 & 2 depict our data for trace element mass fractions in CRMs measured using INAA-LLR and ICP-MS, respectively, as well as the certified values of these materials. Table 3 represents mean values±standard error of mean (M±SEM) of the Ag, Al, Au,B, Be, Bi, Br, Cd, Ce, Co, Cr, Cs, Dy, Er, Fe, Gd, Hg, Ho, La, Li, Mn, Mo,Nb, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Sm, Sn, Tb, Th, Ti, Tl, Tm, U, Y,Yb, Zn and Zr mass fraction in normal, benign hypertrophic and cancerous prostate.
M: Arithmetic Mean, SEM: Standard Error of Mean, *Titanium tools were used for sampling and sample preparation
Table 4 depicts mean values±standard error of mean (M±SEM) of the ratio to Se of Ag, Al, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cs, Dy, Er, Fe, Gd, Hg, Ho, La, Li, Mn, Mo, Nb, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Sm, Sn, Tb, Th, Ti, Tl, Tm, U, Y, Yb, Zn, and Zr mass fraction in normal,benign hypertrophic and cancerous prostate
t-test: Student's t-test, U-test: Wilcoxon-Mann-Whitney U-test, Bold: significant differences
The ratios of means and the difference between mean values of the Se/trace element mass fraction ratios in normal, benign hypertrophic and cancerous prostate are presented in Table 5. Individual data sets for Se/Ag, Se/Al, Se/B, Se/Bi, Se/ Cr, Se/Li, Se/Mn, Se/Sb, Se/Tl, and Se/Zr mass fraction ratios in all investigated samples of normal, benign hypertrophic and cancerous prostate, respectively, are shown in Figure 1.
Table 6 contains parameters of the importance (sensitivity, specificity and accuracy of Se/Ag, Se/Al, Se/B, Se/Bi, Se/Cr, Se/ Li, Se/Mn, Se/Sb, Se/Tl, and Se/Zr mass fraction ratios for the diagnosis of PCa calculated in this work.
Discussion
As was shown by us [14,15,17,18], the use of CRM IAEA H-4 Animal muscle, IAEA HH-1 Human hair, 1NCT-SBF-4 Soya Bean Flour, 1NCT-TL-1 Tea Leaves, and lNCT-MPH-2Mixed Polish Herbs as certified reference materials for the analysis of samples of prostate tissue can be seen as quite acceptable. Good agreement of the trace element contents in these CRMs, measured by us using INAA-LLR and ICP-MS methods, with the certified data (Table 1 & 2) indicates an acceptable accuracy of the results obtained in the present study
The mean values and standard error of mean (±SEM) were calculated for 43 trace element contents including Se ( Table 3), as well as for 42 ratios of Se/trace element mass fractions ( Table 4). The mass fraction of Se and other 42 trace elements were measured in all, or a major portion of normal prostate samples. The masses of BPH and PCa samples varied very strong from a few milligrams (sample from needle biopsy material) to 100mg (sample from resected material). Therefore, in BPH and PCa prostates mass fraction ratios of Se/Ag, Se/Co, Se/Cr, Se/ Fe, Se/Hg, Se/Rb, Se/Sb, Se/Sc, and Se/Zn were measured in all, or a major portion of samples, while ratios to Se of other trace element content were determined in 21 samples (11 BPH and 10 PCa samples, respectively).
From Table 5, it is observed that in benign hypertrophic tissues the Se/Ag, Se/Au, Se/Be, Se/Br, Se/Cd, Se/Co, Se/Fe, Se/ La, Se/Li, Se/Mn, Se/Nb, Se/Ni, Se/Pb, Se/Rb. Se/Sb, Se/Th, Se/ Ti, Se/Tl, Se/Tm, Se/Yb, Se/Zn, and Se/Zr mass fraction ratios not differ from normal levels, but the mass fraction ratios ofSe/Al,Se/Ce, Se/Cs, Se/Dy, Se/Er, Se/Gd, Se/Ho, Se/Mo, Se/Nd, Se/Pr, Se/Sc, Se/Sm, Se/Sn, Se/Tb, and Se/U are higher, while the mass fraction ratios of Se/B, Se/Bi, Se/Cr, and Se/Hg are significantly lower. In cancerous tissue the all Se/trace element mass fraction ratios investigated in the study are significantly lower, than in BPH and normal prostate, with the exception of Se/Cd, Se/Co, Se/Cs, Se/Hg, Se/Mo, Se/Nb, Se/Rb, Se/Sc, Se/Yb, and Se/Zn ratios.
Analysis of the mass fraction ratios for trace element in prostate tissue could become a powerful diagnostic tool. To a large extent, the resumption of the search for new methods for early diagnosis of PCa was due to experience gained in a critical assessment of the limited capacity of the prostate specific antigen (PSA) serum test [77,78]. In addition to the PSA serum test and morphological study of needle-biopsy cores of the prostate, the development of other highly precise testing methods seems to be very useful. Experimental conditions of the present study were approximated to the hospital conditions as closely as possible. In BPH and PCa cases we analyzed a part of the material obtained from a puncture trans rectal biopsy of the indurated site in the prostate. Therefore, our data allow us to evaluate adequately the importance of Se/trace element mass fraction ratios for the diagnosis of PCa. As is evident from Table 5 and, particularly, from individual data sets (Figure 1), the for Se/Ag, Se/Al, Se/B, Se/Bi, Se/Cr, Se/Li, Se/Mn, Se/Sb, Se/Tl, and Se/Zr mass fraction ratios are potentially the most informative test for a differential diagnosis. For example, if 8.0 is the value of Se/Ag mass fraction ratio assumed to be the upper limit for PCa (Figure 1) and an estimation is made for "PCa or intact and BPH tissue”, the following values are obtained:
Sensitivity = {True Positives (TP)/[TP+False Negatives (FN)]} o100%=92±5%.
Specificity = {True Negatives (TN)/[TN False Positives (FP)]} o100%=94±3%.
Accuracy = [(TP+TN)/(TP+FP+TN+FN)] o100%=92±3%.
The number of people (samples) examined was taken into account for calculation of confidence intervals [79]. In other words, if Se/Ag mass fraction ratio in a prostate biopsy sample is lower 8.0, one could diagnose a malignant tumor with an accuracy 92±3%. Thus, using the Se/Ag mass fraction ratio-test makes it possible to diagnose cancer in 92±5% cases (sensitivity). The same way parameters of the importance (sensitivity, specificity and accuracy) of for Se/Al, Se/B, Se/Bi, Se/Cr, Se/Li, Se/Mn, Se/ Sb, Se/Tl, and Se/Zr mass fraction ratios for the diagnosis of PCa were calculated (Table 6).
Conclusion
The combination of nondestructive INAA-LLR and destructive ICP-MS methods is satisfactory analytical tool for the precise determination of 43 trace element mass fractions in the tissue samples of normal, BPH and carcinomatous prostate glands. The sequential application of these methods allowed precise quantitative determinations of mean mass fraction of Ag, Al, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cs, Dy, Er, Fe, Gd, Hg, Ho, La, Li, Mn, Mo, Nb, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Sm, Sn, Tb, Th, Ti, Tl, Tm, U, Y, Yb, Zn and Zr. It was observed that the ratio to Se of Ag, Al, Au, B, Be, Bi, Br, Ce, Cr, Dy, Er, Fe, Gd, Ho, La, Li, Mn, Nd, Ni, Pb, Pr, Rb, Sb, Sm, Sn, Tb, Th, Ti, Tl, Tm, U, Y, Yb, and Zr mass fraction were significantly lower in cancerous tissues than in normal and BPH prostate. It was proposed to use the Se/Ag, Se/Al, Se/B, Se/ Bi, Se/Cr, Se/Li, Se/Mn, Se/Sb, Se/Tl, and Se/Zr mass fraction ratios in a needle-biopsy core as an accurate tool to diagnose prostate cancer. Further studies on larger number of samples are required to confirm our findings and to investigate the impact of the trace element relationships on prostate cancer etiology.
Acknowledgement
We are grateful to Dr. Tatyana Sviridova, Medical Radiological Research Center, Obninsk, and to the late Prof. A.A. Zhavoronkov, Institute of Human Morphology, Russian Academy of Medical Sciences, Moscow, for supplying prostate samples. We are also grateful to Dr. Karandaschev V, Dr. Nosenko S, and Moskvina I, Institute of Microelectronics Technology and High Purity Materials, Chernogolovka, Russia, for their help in ICP-MS analysis.
References
- Roehrborn C, McConnell J (2002) Etiology, pathophysiology, epidemiology and natural history of benign prostatic hyperplasia. In: Walsh P, Retik A, Vaughan E, Wein A (Eds.), Campbell's Urology (8th edn.), Saunders, Philadelphia, USA, pp. 1297-1336.
- Lepor H (2005) Pathophysiology of benign prostatic hyperplasia in the aging male population. Rev Urol 7(Suppl 4): S3-S12.
- Oliver SE, Gunnell D, Donovan JL (2000) Comparison of trends in prostate-cancer mortality in England and Wales and the USA. Lancet 355(9217): 1788-1789.
- Kumar RJ, Barqawi AB, Crawford ED (2004) Epidemiology of prostate cancer Business Briefing: US Oncology Review, p. 1-6.
- Maddams J, Brewster D, Gavin A, Steward J, Elliott J, et al. (2009) Cancer prevalence in the United Kingdom: estimates for 2008. Br J Cancer 101(3): 541-547.
- Lutz JM, Francisci S, Mugno E, Usel M, Pompe-Kirn V, et al. (2003) Cancer prevalence in Central Europe: the EUROPREVAL Study. Ann Oncol 14(2): 313-322.
- Moller T, Anderson H, Aareleid T, Hakulinen T, Storm H, et al. (2003) Cancer prevalence in Northern Europe: the EUROPREVAL study. Ann Oncol 14(6): 946-957.
- De Angelis R, Grande E, Inghelmann R, Francisci S, Micheli A, et al. (2007) Cancer prevalence estimates in Italy from 1970 to 2010. Tumori 93(4): 392-397.
- Waalkes MP, Rehm S (1994) Cadmium and prostate cancer. J Toxicol Environ Health 43(3): 251-269.
- Zaichick V, Zaichick S (1999) Role of zinc in prostate cancerogenesis. In: Anke M, et al. (eds.), Mengen und Spurenelemente. 19. Arbeitstagung. Friedrich-Schiller-Universitat. Jena, pp. 104-115.
- Platz EA, Helzlsouer KJ (2001) Selenium, zinc, and prostate cancer Epidemiol Rev23(1): 93-101.
- Zaichick V (2004) INAA and EDXRF applications in the age dynamics assessment of Zn content and distribution in the normal human prostate. J Radioanal Nucl Chem 262(1): 229-234.
- Gray MA, Centeno JA, Slaney DP, Ejnik JW, Todorov T, et al. (2005) Environmental exposure to trace elements and prostate cancer in three New Zealand ethnic groups. Int J Environ Res Public Health 2(3- 4): 374-384.
- Zaichick S, Zaichick V (2011) INAA application in the age dynamics assessment of Br, Ca, Cl, K, Mg, Mn, and Na content in the normal human prostate. J Radioanal Nucl Chem 288(1): 197-202.
- Zaichick S, Zaichick V (2011) The effect of age on Ag, Co, Cr, Fe, Hg, Sb, Sc, Se, and Zn contents in intact human prostate investigated by neutron activation analysis. Appl Radiat Isot 69: 827-833.
- Zaichick S, Zaichick V (2011) The Br, Fe, Rb, Sr, and Zn content and interrelation in intact and morphologic normal prostate tissue of adult men investigated by energy dispersive X-ray fluorescent analysis. X-Ray Spectrom 40(6): 464-469.
- Zaichick V, Nosenko S, Moskvinal (2012) The effect of age on 12 chemical element contents in intact prostate of adult men investigated byinductively coupled plasma atomic emission spectrometry. Biol Trace Elem Res 147(1-3): 49-58.
- Zaichick S, Zaichick V, Nosenko S, Moskvina I (2012) Mass Fractions of 52 Trace Elements and Zinc Trace Element Content Ratios in Intact Human Prostates lnvestigated by lnductively Coupled Plasma Mass Spectrometry. Biol Trace Elem Res 149(2): 171-183.
- Zaichick V, Zaichick S (2014) Age-related histological and zinc content changes in adult nonhyperplastic prostate glands. Age 36(1): 167-181.
- Zaichick V, Zaichick S (2014) INAA application in the assessment of chemical element mass fractions in adult and geriatric prostate glands. Appl Radiat Isot 90: 62-73.
- Zaichick V, Zaichick S (2014) Determination of trace elements in adults and geriatric prostate combining neutron activation with inductively coupled plasma atomic emission spectrometry. Open Journal of Biochemistry 1(2): 16-33.
- Zaichick V, Zaichick S (2014) Use of INAA and ICP-MS for the assessment of trace element mass fractions in adult and geriatric prostate. J Radioanal Nucl Chem 301(2): 383-397.
- Zaichick V (2015) The variation with age of 67 macro- and microelement contents in nonhyperplastic prostate glands of adult and elderly males investigated by nuclear analytical and related methods. Biol Trace Elem Res 168(1): 44-60.
- Zaichick V, Zaichick S (2015) Dietary intake of minerals and prostate cancer: insights into problem based on the chemical element contents in the prostate gland. J Aging Res Clin Practice 4(3): 164-171.
- Zaichick V, Zaichick S (2015) Global contamination from uranium: insights into problem based on the uranium content in the human prostate gland. J Environ Health Sci 1(4): 1-5.
- Zaichick V, Zaichick S (2016) Variations in concentration and distribution of several androgen-dependent and -independent trace elements in nonhyperplastic prostate gland tissue throughout adulthood. J Androl Gynaecol 4(1): 1-10.
- Zaichick V, Zaichick S (2016) Age-related changes in concentration and histological distribution of Br, Ca, Cl, K, Mg, Mn, and Na in nonhyperplastic prostate of adults. European Journal of Biology and Medical Science Research 4(2): 31-48.
- Zaichick V, Zaichick S (2016) Variations in concentration and histological distribution of Ag, Co, Cr, Fe, Hg, Rb, Sb, Sc, Se, and Zn in nonhyperplastic prostate gland throughout adulthood. Jacobs Journal of Cell and Molecular Biology 2(1): 011.
- Zaichick V, Zaichick S (2016) Age-relatedchanges inconcentration andhistological distribution of 54 trace elements in nonhyperplastic prostate of adults. Int Arch Urol Complic 2(2): 019.
- Zaichick V (2006) Medical elementology as a new scientific discipline. J Radioanal Nucl Chem 269(2): 303-309.
- Stitch SR (1957) Trace elements in human tissue. I. A semi-quantitative spectrographic survey. Biochem J 67(1): 97-103.
- Tipton IH, Cook MJ (1963) Trace elements in human tissue. Part II. Adult subjects from the United States. Health Phys 9: 103-145.
- Györkey F, Min KW, Huff JA, Györkey P (1967) Zinc and magnesium in human prostate gland: normal, hyperplastic, and neoplastic. Cancer Res 27(8): 1349-1353.
- Sangen H (1967) The influence of the trace metals upon the aconitase activity in human prostate glands. Jap J Urol 58: 1146-1159.
- Schneider HJ, Anke M, Holm W (1970) The inorganic components of testicle, epididymis, seminal vesicle, prostate and ejaculate of young men. Int Urol Nephrol 2(4): 419-427.
- Hienzsch E, SchneiderHJ, Anke M (1970) Vergleichende Untersuchungen zum Mengen- und Spurenelementgehalt der normalen Prostata, des Prostataadenoms und des Prostatakarzinoms. Zeitschrift für Urologie und Nephrologie 63: 543-546.
- Soman SD, Joseph KT, Raut SJ, Mulay GD, Parameswaran M, et al. (1970) Studies of major and trace element content in human tissues. Health Phys 19(5): 641-656.
- Forssen A (1972) Inorganic elements in the human body: I. occurrence of Ba, Br, Ca, Cd, Cs, Cu, K, Mn, Ni, Sn, Sr, Y and Zn in the human body. Annales medicinae Experimentalis et Biologie (Finland) 50(3): 99-162.
- Dhar NK, Goel TC, Dube PC, Chowdhury AR, Kar AB (1973) Distribution and concentration of zinc in the subcellular fractions of benign hyperplastic and malignant neoplastic human prostate. Exp Mol Pathol 19(2): 139-142.
- Jafa A, Mahendra NM, Chowdhury AR, Kamboj VP (1980) Trace elements in prostatic tissue and plasma in prostatic diseases of man. Indian J Cancer 17(1): 34-37.
- Marezynska A, Kulpa J, Lenko J (1983) The Concentration of zimc in relation to fundamental elements in the diseases human prostate. Int Urol Nephrol 15(3): 257-265.
- Hienzsch E, Schneider HJ, Anke M (1991)Vergleichende Untersuchungen zum Mengen- und Spurenelementgehalt der normalen Prostata, des Prostataadenoms und des Prostatakarzinoms. Z Urol Nephrol 63(7): 543-546.
- Picurelli L, Olcina PV, Roig MD, Ferrer J (1991) Determination of Fe, Mg, Cu, and Zn in normal and pathological prostatic tissue. Actas Urol Esp 15(4): 344-350.
- Zaichick V, Sviridova T, Zaichick S (1997) Zinc in human prostate gland: normal, hyperplastic and cancerous. Int Urol Nephrol 29(5): 565-574.
- Galvan-Bobadilla AI, Garcia-Escamilla RM, Gutierrez-Garcia N, Mendoza-Magana ML, Rosiles-Martinez R (2005) Cadmium and zinc concentrations in prostate cancer and benign prostatehyperplasia. Rev Latinoamer Patol Clin 52(2): 109-117.
- Yaman M, Atici D, Bakirdere S, Akdeniz I (2005) Comparison of trace metal concentrations in malignant and benign human prostate. J Med Chem 48(2): 630-634.
- Kwiatek WM, Banas A, Banas K, Podgorczyk M, Dyduch G, et al. (2006) Distinguishing prostate cancer from hyperplasia. Acta Physica Polonica 109(3): 377-381.
- Guntupalli JNR, Padala S, Gummuluri AVRM, Muktineni RK, Byreddy SR, et al. (2007) Trace elemental analysis of normal, benign hypertrophic and cancerous tissues of the prostate gland using the particle-induced X-ray emission technique. Eur J Cancer Prev 16(2): 108-115.
- Tohno S, Kobayashi M, Shimizu H, Tohno Y, Suwannahoy P, et al. (2009) Age-related changes of the concentrations of select elements in the prostates of Japanese. Biol Trace Elem Res 127(3): 211-227.
- Kiziler AR, Aydemir B, Guzel S, Alici B, Ataus S, et al. (2010) May the level and ratio changes of trace elements be utilized in identification of disease progression and grade in prostatic cancer? Trace Elements and Electrolytes 27(2): 65-72.
- Zaichick S, Zaichick V (2010) Method and portable facility for energy- dispersive X-ray fluorescent analysis of zinc content in needle-biopsy specimens of prostate. X-Ray Spectrom 39: 83-89.
- Zaichick S, Zaichick V (2012) Trace elements of normal, benign hypertrophic and cancerous tissues of the human prostate gland investigated by neutron activation analysis. Appl Radiat lsot 70(1): 8187.
- Zaichick V, Zaichick S (2013) The effect of age on Br, Ca, Cl, K, Mg, Mn, and Na mass fraction in pediatric and young adult prostate glands investigated by neutron activation analysis. Appl Radiat Isot 82: 145151.
- Zaichick V, Zaichick S (2013) NAA-SLR and ICP-AES Application in the assessment of mass fraction of 19 chemical elements in pediatric and young adult prostate glands. Biol Trace Elem Res 156(1-3): 357-366.
- Leitao RG, Palumbo A, Souza PAVR, Pereira GR, Canellas CGL, et al.(2014) Elemental concentration analysis in prostate tissues using total reflection X-ray fluorescence. Radiation Physics and Chemistry 95: 6264.
- Zaichick S, Zaichick V (2014) EDXRF determination of trace element contents in benign prostatic hypertrophic tissue. In: Fundamental lnteractions and Neutrons, Neutron Spectroscopy, Nuclear Structure, Ultracold Neutrons, Related Topics. Joint Institute for Nuclear Research, Dubna, Russia, pp. 311-316.
- Denoyer D, Clatworthy SAS, Masaldan S, Meggyesy PM, Cater MA(2015) Heterogeneous Copper Concentrations in Cancerous Human Prostate Tissues. Prostate 75(14): 1510-1517.
- Zaichick S, Zaichick V (2015) Prostatic Tissue Level of some Androgen Dependent and lndependent Trace Elements in Patients with Benign Prostatic Hyperplasia. Androl Gynecol: Curr Res 3: 3.
- Singh BP, Dwivedi S, Dhakad U, Murthy RC, Choubey VK, et al. (2016) Status and lnterrelationship of Zinc, Copper, lron, Calcium and Selenium in Prostate Cancer. Indian J Clin Biochem 31(1): 50-56.
- Zaichick V, Zaichick S (2016) Trace element contents in adenocarcinoma of human prostate investigated by energy dispersive X-ray fluorescent analysis. Journal of Adenocarcinoma 1(1): 1-7.
- Zaichick V, Zaichick S (2016) The Bromine, Calcium, Potassium, Magnesium, Manganese, and Sodium Contents in Adenocarcinoma of Human Prostate Gland. J Hematology and Oncology Research 2(2): 1-12.
- Zaichick V, Zaichick S (2016) Trace element contents in adenocarcinoma of the human prostate gland investigated byneutron activation analysis. Cancer Research & Oncology 1(1): 1-10.
- Zaichick V, Zaichick S (2016) Prostatic tissue levels of 43 trace elements in patients with prostate adenocarcinoma. Cancer and Clinical Oncology 5(1): 79-94.
- Zaichick V, Zaichick S (2016) Prostatic tissue level of some major and trace elements in patients with BPH. Jacobs Journal of Nephrology and Urology 3(1): 025.
- Zaichick V, Zaichick S (2016) Levels of 43 Trace Elements in Hyperplastic Prostate Tissues. British Journal of Medicine and Medical Research 15(2): 1-12.?
- Zaichick V, Zaichick S (2016) Chemical elemental content/Calcium ratios in tissues of human hyperplastic prostate gland. Journal of Applied Life Sciences International 4(4): 1-11.
- Zaichick V, Zaichick S (2016) Distinguishing malignant from benign prostate using Br, Ca, K, Mg, Mn, and Na content in prostatic tissue. Integrative Molecular Medicine 3(3): 733-738.
- Zaichick V, Zaichick S (2016) Distinguishing malignant from benign prostate using content of 17 chemical elements in prostatic tissue. Integr Cancer Sci Therap3(5): 579-587.
- Rossmann M, Zaichick S, Zaichick V (2016) Distinguishing malignant from benign prostate tumors using Br, Fe, Rb, Sr, and Zn content in prostatic tissue. Clinics in Oncology 1(1): 1054.
- Zaichick V, Zaichick S (2017) Ratios of Zn/trace element contents in prostate gland as carcinoma's markers. Cancer Rep Rev 1(1): 1-7.
- Zaichick V (1997) Sampling, sample storage and preparation of biomaterials for INAA in clinical medicine, occupational and environmental health. In: Harmonization of Health-Related Environmental Measurements Using Nuclear and Isotopic Techniques. IAEA, Vienna, pp. 123-133.
- Zaichick V, Zaichick S (1996) Instrumental effect on the contamination of biomedical samples in the course of sampling. The Journal of Analytical Chemistry 51(12): 1322-1327.
- Zaichick V, Zaichick S (1997) A search for losses of chemical elements during freeze-drying of biological materials. J Radioanal Nucl Chem 218(2): 249-253.
- Zaichick V (2004) Losses of chemical elements in biological samples under the dry aching process. Trace Elements in Medicine 5(3): 17-22.
- Zaichick V(1995) Application of synthetic reference materials in the Medical Radiological Research Centre. Fresenius J Anal Chem 352(1): 219-223.
- Korelo AM, Zaichick V (1993) Software to optimize the multielement lNAA of medical and environmental samples. ln: Activation Analysis in Environment Protection. Joint lnstitute for Nuclear Research, Dubna, Russia, pp. 326-332.
- Catalona WJ (1996) Clinical utility of measurements of free and total prostate-specific antigen (PSA): A review. Prostate 7: 64-69.
- Hjertholm P, Fenger-Gron M, Vestergaard M, Christensen MB, Borre M, et al. (2015) Variation in general practice prostate-specific antigen testing and prostate cancer outcomes: An ecological study. lnt J Cancer 136(2): 435-442.
- Genes VS (1967) Simple methods for cybernetic data treatment of diagnostic and physiological studies. Nauka, Moscow, p. 208.