Metal dyshomeostasis based biomarkers of lung cancer using human biofluids

Abstract

Lung cancer (LC) is one of the most common causes of cancer-related deaths in the world and it is well known that trace elements play important roles in the carcinogenic process activating and inhibiting enzymatic reactions and metalloproteins, in which they usually participate as cofactors. A cross-sectional study was conducted on 48 lung cancer patients and 39 controls (56 men and 31 women), aged 44-76 years between March 2011 and June 2012. Eleven elements have been included in the study: V, Cr, Mn, Fe, Co, Cu, Zn, Se, Mo, Cd, and Pb, some of them considered toxic (V, Cd, Cr and Pb), while others are essential (Co, Mo, Se, Fe and Zn), and they have been analyzed by ICP-QQQ-MS in serum, urine and for the first time in bronchoalveolar lavage fluid (BALF). In order to understand the involvement of metals in this process, an analytical metallomic approach based on non-denaturing precipitation of proteins (NDPP) has been optimized for the fractionation of high molecular mass (HMM) and low molecular mass (LMM) metal species, in order to distinguish between metal species that affect the biological activity and toxicological potential of the elements. In this work, the NDPP followed by the analysis of metals by ICP-QQQ-MS has been applied for the first time to serum, urine and BALF samples from lung cancer patients and controls in order to get metal-size molecule profiles (MSMP), which can be used as metal-based biomarkers of altered metabolic processes such as oxidative stress and homeostasis. In this sense, we have demonstrated that several metals are good biomarkers when they are related to labile complexes, complexed with low molecular mass ligands, or in the form of metalloproteins (i.e. V and Cr in HMM and Cu in LMM), which has been described for the first time. On the other hand, metal dyshomeostasis biomarkers are proposed using metal ratios and correlations. Finally, the ratios between elements were shown to be important biomarkers for lung cancer in serum (V/Mn, V/Pb, V/Zn, Cr/Pb), urine (Cr/Cd, Mn/Cd, V/Cd, Co/Cd, Cd/Pb) and BALF (V/Cu), which reflects the dyshomeostasis of metals in lung cancer. In this sense, several metals are correlated to others suggesting also the existence of an interconnected homeostasis in lung cancer.

The Metallome of Lung Cancer and its Potential Use as Biomarker

“…The relationship between metal exposure and lung cancer (LC) has been deeply studied, especially in occupational medicine and environmental studies. The use of metals for diagnosis is more scarce, but several authors have classified lung cancer patients and healthy people using metals content in tumor tissues [71,72], serum, hair [24,73], urine [74], and bronchoalveolar lavage fluid (BALF) [75], because they found statistically significant differences from the normal distribution of elements for the diagnosis of LC. Then, in the literature, it is possible to find levels of essential and non-essential elements in different biofluids and tissues of lung cancer (LC) patients, for example in plasma [76,77], serum [18,24,42,75,78], urine [74,75,79], pleural effusion [80], or hair [24,73], and recently in bronchoalveolar lavage fluid (BALF) for the first time [75].…”

“…For the determination of the relationships between trace elements and redox status parameters, authors have recommended the use of different samples [18]. On the other hand, there are several papers describing the analysis of metals in bronchoalveolar lavage fluid [83,84], but only one is related to lung cancer patients [75].…”

“…However, other studies revealed higher concentrations of V in the serum of LC patients [75]. Finally, Cr is another element that is usually increased in the serum of LC patients [24,75,76].…”

“…The determination of 11 elements in the BALF of LC patients demonstrated that increased levels of Mn can be used as a biomarker, since it showed a VIP (Variable Importance on the Projection) value of 1.29, a fold change of 1.5, a p-value of 0.003, and an AUC (Area Under the Curve) value of 0.75 [75]. Other authors also reported decreased levels of manganese in BALF from patients with diffuse lung diseases [91] or calves with mycoplasma bronchopneumonia [92].…”

Organ Metallome Processed with Chemometric Methods Enable the Determination of Elements that May Serve as Markers of Exposure to Iron Oxide Nanoparticles in Male Rats

“…The method was also used for quantitative imaging of the influence of chronic Mn exposure on metal accumulation in hippocampal formation [43]. In turn, discriminant analysis was adapted inter alia, for characterization of metal profiles within serum in Alzheimer's disease [34] and gouty arthritis [44] as well as identification of metal biomarkers of different cancers in human tissues [39,45,46]. In the literature, there are also many examples of the chemometric method application in the research utilizing X-ray fluorescencebased techniques [24,36,38,47,48].…”