Comparison of different sample preparation methods for platinum determination in cultured cells by graphite furnace atomic absorption spectrometry

Effective monitoring of Platinum-DNA adducts formation under simulated physiological conditions by CE-ICP-MS/MS

The leading Pt(II)-based anticancer drugs have been used for decades; however, chemotherapy with their application is burdened with severe side effects. The administration of compounds capable of DNA platination in the form of prodrugs has the potential to overcome the drawbacks associated with their use. Progress toward their clinical application depends on establishing proper methodologies that would allow assessing their ability to bind to DNA in the biological environment. Herein, we propose implementing the approach based on the hyphenation of capillary electrophoresis with inductively coupled plasma tandem mass spectrometry (CE-ICP-MS/MS) for studying Pt-DNA adduct formation. The presented methodology opens the possibility to employ the multielement monitoring for studying the differences in the behavior of Pt(II) and Pt(IV) complexes and, interestingly, revealed the formation of various adducts with DNA and cytosol components for the latter one.

Assessment of Heavy Metals and Related Impacts on Antioxidants and Physiological Parameters in Oil Refinery Workers in Iraq

BACKGROUND

Some heavy metals can be harmful to human health in elevated doses such as zinc (Zn) and magnesium (Mg), while others such as lead (Pb), cadmium (Cd), mercury (Hg), and copper (Cu) have harmful consequences to health even in small doses. Heavy metals and additives are incorporated into crude oil to enhance performance.3,4,5 Crude oil is well known to contain heavy metals like Cu, Cd, Ni and Pb.3,6,7.

OBJECTIVE

The current study aimed to assess levels of heavy metals and the impact of these metals on antioxidant levels and physiological variables in the serum of oil refinery workers in Iraq.

METHODS

Heavy metals such as Pb, Cd, Hg, Zn, Cu and Mg were assessed in the serum of a sample of refinery workers (N=40) and a control group (N=20) using atomic absorption spectrometry (AAS). Additionally, levels of malondialdehyde (MDA), δ-aminolaevulinic acid dehydratase (ALAD) and total antioxidant capacity (TAC), and physiological variables such as blood urea, serum creatinine, glutamate-oxaloacetic transaminase (GOT), glutamate-pyruvic transaminase (GPT), and gamma-glutamyl transferase (GGT) were measured to assess impact of these heavy metals.

RESULTS

Mercury, Cd, and Pb were significantly elevated in the refinery worker group in comparison with the control group, while the levels of Zn, Cu, and Mg were significantly lower in the refinery worker group compared to the control group. There was a significant difference between the control group and the worker group for most of the antioxidants and functional variables. Total antioxidant capacity (TAC), δ-aminolevulinic acid dehydratase (ALAD), and malondialdehyde (MDA) were significantly lower in the worker group while blood urea, serum creatinine, glutamate pyruvate transaminase (GPT), and gamma-glutamyl transferase (GGT) showed a significant elevation in the workers' group. Glutamic oxaloacetic transaminase (GOT) showed no significant difference between the control group and the worker group.

CONCLUSIONS

Refinery workers are at increased risk of having higher serum levels of Pb, Cd, and Hg compared to controls which can lead to an increase in oxidative stress, decrease in TAC, and decrease in the essential trace elements Zn, Cu and Mg.

PARTICIPANT CONSENT

Obtained.

ETHICS APPROVAL

This study was approved by the ethics committee within the Nineveh Health Department, Mosul, Iraq.

COMPETING INTERESTS

The authors declare no competing financial interests.

Chloroxine overrides DNA damage tolerance to restore platinum sensitivity in high-grade serous ovarian cancer

High-grade serous cancer (HGSC) accounts for ~67% of all ovarian cancer deaths. Although initially sensitive to platinum chemotherapy, resistance is inevitable and there is an unmet clinical need for novel therapies that can circumvent this event. We performed a drug screen with 1177 FDA-approved drugs and identified the hydroxyquinoline drug, chloroxine. In extensive validation experiments, chloroxine restored sensitivity to both cisplatin and carboplatin, demonstrating broad synergy in our range of experimental models of platinum-resistant HGSC. Synergy was independent of chloroxine's predicted ionophore activity and did not relate to platinum uptake as measured by atomic absorption spectroscopy. Further mechanistic investigation revealed that chloroxine overrides DNA damage tolerance in platinum-resistant HGSC. Co-treatment with carboplatin and chloroxine (but not either drug alone) caused an increase in γH2AX expression, followed by a reduction in platinum-induced RAD51 foci. Moreover, this unrepaired DNA damage was associated with p53 stabilisation, cell cycle re-entry and triggering of caspase 3/7-mediated cell death. Finally, in our platinum-resistant, intraperitoneal in vivo model, treatment with carboplatin alone resulted in a transient tumour response followed by tumour regrowth. In contrast, treatment with chloroxine and carboplatin combined, was able to maintain tumour volume at baseline for over 4 months. In conclusion, our novel results show that chloroxine facilitates platinum-induced DNA damage to restore platinum sensitivity in HGSC. Since chloroxine is already licensed, this exciting combination therapy could now be rapidly translated for patient benefit.

Effects of Single Nucleotide Polymorphism Ala270Ser (rs316019) on the Function and Regulation of hOCT2

The human organic cation transporter 2 (hOCT2) is highly expressed in proximal tubules of the kidneys, where it plays an important role in the secretion of organic cations. Since many drugs are organic cations, hOCT2 has relevant pharmacological implications. The hOCT2 gene is polymorphic, and the nonsynonymous single nucleotide polymorphism (SNP) causing the substitution of alanine at position 270 of the protein sequence with serine (Ala270Ser) is present with high frequency in the human population. Therefore, Ala270Ser has potentially important pharmacologic consequences. Here, we analyzed the transport properties and rapid regulation of hOCT2 wildtype and hOCT2 Ala270Ser expressed in human embryonic kidney cells using real-time uptake measurements. Moreover, we compared the expression of hOCT2 in the plasma membrane determined by biotinylation experiments and the cellular transport and toxicity of cisplatin measured by inductively coupled plasma mass spectrometry and a viability test, respectively. The transport characteristics and regulation of the wildtype and mutated hOCT2 were very similar. Interestingly, a higher affinity of hOCT2 Ala270Ser for creatinine was observed. Compared with hOCT2 wildtype, the plasma membrane expression, cisplatin transport, and cisplatin-associated toxicity of hOCT2 Ala270Ser were significantly lower. In conclusion, these findings suggest that Ala270Ser has subtle but important effects on hOCT2 function, which are probably difficult to detect in studies with patients.

Enhancer of zeste homolog 2 promotes cisplatin resistance by reducing cellular platinum accumulation

Enhancer of zeste homolog 2 (EZH2), which is overexpressed in a wide range of tumors, contributes to ovarian cancer malignancy in several different ways. We aimed to illustrate the role of EZH2 in ovarian cancer cisplatin resistance and to identify possible underlying mechanisms of this role that may provide a rationale for targeting EZH2 in cancer treatment. Here, we present data indicating that EZH2 overexpression is associated with cisplatin resistance and intracellular platinum drug accumulation. Measurements of EZH2 in 84 ovarian cancer patients suggested that patients with high EZH2 levels tend to have poor responses to cisplatin. The EZH2 level progressively increased in cells receiving repeated cisplatin exposure. Downregulation of EZH2 not only sensitized cellular reactions to cisplatin and increased cellular platinum accumulation when cells were exposed to both cisplatin and BODIPY-Pt (a fluorescent cisplatin complex) but also protected copper transporter 1, a high-affinity copper transporter closely related to cisplatin resistance, from cisplatin-induced proteasomal degradation. Overall, these findings identify a new mechanism that expands the unrecognized role of EZH2 in ovarian cancer cisplatin resistance.