Choice of mobile phase: Implications for size exclusion chromatography-inductively coupled plasma-mass spectrometry analyses of copper, zinc and iron metalloproteins

Proteomics mining of cancer hallmarks on a single-cell resolution

Dysregulated proteome is an essential contributor in carcinogenesis. Protein fluctuations fuel the progression of malignant transformation, such as uncontrolled proliferation, metastasis, and chemo/radiotherapy resistance, which severely impair therapeutic effectiveness and cause disease recurrence and eventually mortality among cancer patients. Cellular heterogeneity is widely observed in cancer and numerous cell subtypes have been characterized that greatly influence cancer progression. Population-averaged research may not fully reveal the heterogeneity, leading to inaccurate conclusions. Thus, deep mining of the multiplex proteome at the single-cell resolution will provide new insights into cancer biology, to develop prognostic biomarkers and treatments. Considering the recent advances in single-cell proteomics, herein we review several novel technologies with particular focus on single-cell mass spectrometry analysis, and summarize their advantages and practical applications in the diagnosis and treatment for cancer. Technological development in single-cell proteomics will bring a paradigm shift in cancer detection, intervention, and therapy.

Impact of laboratory involvement in the characterization of B12 hypervitaminosis in clinical practice

Objectives

Unexplained B12 hypervitaminosis (HB12) in asymptomatic patients leads to a cascade of medical consultations and diagnostic tests aimed at determining its etiology. The objective of this study was to assess the efficacy of the laboratory getting involved in the detection and elimination of immune complexes with vitamin B12 in clinical practice and its economic impact.

Methods

A retrospective longitudinal study was undertaken to assess the laboratory strategy of detecting B12 macrovitamin (macro-B12) in patients with HB12 >1,000 pg/mL. The clinical characteristics of patients with HB12 referred to Internal Medicine (IM) in the pre- and post-implantation period of the new strategy were compared. Additionally, the healthcare costs of one-year follow-up were estimated.

Results

The prevalences of HB12 in the pre- and post-implantation period were 3.9 % and 3 %, respectively. Macro-B12 explained 25 % of the HB12 cases initially detected. A 41 % reduction was observed in the number of patients with HB12 after the implantation of the new strategy, thereby resulting in a cost reduction of 5,000 €.

Conclusions

The laboratory intervention for the detection of macro-B12 provides clear economic and clinical benefits in clinical practice.

Impacto de la intervención del laboratorio en la caracterización de la hipervitaminosis B12 en la práctica asistencial

Objectivos

El hallazgo de hipervitaminosis B12 (HB12) no justificado en pacientes asintomáticos desencadena consultas médicas y pruebas diagnósticas, a fin de determinar la etiología. Nuestro objetivo fue probar la eficacia de la intervención del laboratorio en la detección y eliminación de inmunocomplejos con vitamina B12 en la práctica clínica, así como su impacto económico.

Métodos

Es un estudio retrospectivo y longitudinal diseñado para evaluar la estrategia del laboratorio para detectar macrovitamina B12 (macro-B12) en aquellos pacientes con HB12 mayor a 1.000 pg/mL. Se compararon las características clínicas de los pacientes con HB12 derivados a las consultas de Medicina Interna (MI) en el año anterior y posterior a la implantación de la estrategia y se calcularon los costes asistenciales generados en el año de seguimiento de los pacientes.

Resultados

La prevalencia de HB12 en el periodo previo y posterior a la implantación fue del 3,9 % y 3 %, respectivamente. La macro-B12 fue responsable del 25 % de la HB12 iniciales detectadas. El número de pacientes con HB12 derivados a las consultas de MI se redujo en el 41 % tras la implantación, traduciéndose en un ahorro de más de 5.000€.

Conclusiones

La intervención del laboratorio de detección de macro-B12 tiene un claro beneficio asistencial y económico en la práctica clínica.

Rapid determination of toxic and essential metal binding proteins in biological samples by size exclusion chromatography-inductively coupled plasma tandem mass spectrometry

Metalloproteins binding with trace elements play a crucial role in biological processes and on the contrary, those binding with exogenous heavy metals have adverse effects. However, the methods for rapid, high sensitivity and simultaneous analysis of these metalloproteins are still lacking. In this study, a fast method for simultaneously determination of both essential and toxic metal-containing proteins was developed by coupling size exclusion chromatography (SEC) with inductively coupled plasma tandem mass spectrometry (ICP-MS/MS). After optimization of the separation and detection conditions, seven metalloproteins with different molecular weight (from 16.0 to 443.0 kDa) were successfully separated within 10 min and the proteins containing iron (Fe), copper (Cu), zinc (Zn), iodine (I) and lead (Pb) elements could be simultaneously detected with the use of oxygen as the collision gas in ICP-MS/MS. Accordingly, the linear relationship between log molecular weight and retention time was established to estimate the molecular weight of unknown proteins. Thus, the trace metal and toxic metal containing proteins could be detected in a single run with high sensitivity (detection limits in the range of 0.0020-2.5 μg/mL) and good repeatability (relative standard deviations lower than 4.5 %). This method was then successfully used to analyze metal (e.g., Pb, Zn, Cu and Fe) binding proteins in the blood of Pb-intoxicated patients, and the results showed a negative correlation between the contents of zinc and lead binding proteins, which was identified to contain hemoglobin subunit. In summary, this work provided a rapid and sensitive tool for screening metal containing proteins in large number of biological samples.

Recent Advances in Metalloproteomics

Interactions between proteins and metal ions and their complexes are important in many areas of the life sciences, including physiology, medicine, and toxicology. Despite the involvement of essential elements in all major processes necessary for sustaining life, metalloproteomes remain ill-defined. This is not only owing to the complexity of metalloproteomes, but also to the non-covalent character of the complexes that most essential metals form, which complicates analysis. Similar issues may also be encountered for some toxic metals. The review discusses recently developed approaches and current challenges for the study of interactions involving entire (sub-)proteomes with such labile metal ions. In the second part, transition metals from the fourth and fifth periods are examined, most of which are xenobiotic and also tend to form more stable and/or inert complexes. A large research area in this respect concerns metallodrug-protein interactions. Particular attention is paid to separation approaches, as these need to be adapted to the reactivity of the metal under consideration.

Arsenic Exposure Causes Global Changes in the Metalloproteome of Escherichia coli

Arsenic is a toxic metalloid with differential biological effects, depending on speciation and concentration. Trivalent arsenic (arsenite, AsIII) is more toxic at lower concentrations than the pentavalent form (arsenate, AsV). In E. coli, the proteins encoded by the arsRBC operon are the major arsenic detoxification mechanism. Our previous transcriptional analyses indicate broad changes in metal uptake and regulation upon arsenic exposure. Currently, it is not known how arsenic exposure impacts the cellular distribution of other metals. This study examines the metalloproteome of E. coli strains with and without the arsRBC operon in response to sublethal doses of AsIII and AsV. Size exclusion chromatography coupled with inductively coupled plasma mass spectrometry (SEC-ICPMS) was used to investigate the distribution of five metals (56Fe, 24Mg, 66Zn, 75As, and 63Cu) in proteins and protein complexes under native conditions. Parallel analysis by SEC-UV-Vis spectroscopy monitored the presence of protein cofactors. Together, these data reveal global changes in the metalloproteome, proteome, protein cofactors, and soluble intracellular metal pools in response to arsenic stress in E. coli. This work brings to light one outcome of metal exposure and suggests that metal toxicity on the cellular level arises from direct and indirect effects.