Serum-binding properties of isosteric ruthenium and osmium anticancer agents elucidated by SEC–ICP–MS

Abstract

Size-exclusion chromatography–inductively coupled plasma–mass spectrometry (SEC–ICP–MS) was used to study the serum-binding preferences of two metallodrugs with anticancer activities in vivo, namely the organoruthenium compound plecstatin-1 and its isosteric osmium analog. The complexes were administered intraperitoneally into mice bearing a CT-26 tumor. Comparing the total metal content of mouse whole blood and serum underlined that the metallodrugs are mainly located in serum and not in the cellular fraction of the blood samples. In mouse serum, both compounds were not only found to bind extensively to the serum albumin/transferrin fraction but also to immunoglobulins. Free drug was not observed in any of the samples indicating rapid protein binding of the metallodrugs. These findings were validated by spiking human serum with the respective compounds ex vivo. An NCI-60 screen is reported for the osmium analog, which revealed a relative selectivity for cancer cell lines of the ovary and the central nervous system with respect to plecstatin-1. Finally, a COMPARE 170 analysis revealed disruption of DNA synthesis as a possible treatment effect of the osmium-based drug candidate.Graphical abstract

A metalloproteomic analysis of interactions between plasma proteins and zinc: elevated fatty acid levels affect zinc distribution

“…S4, ESI †). This is in agreement with previous crystallographic 72 and molecular modelling studies, 41 which suggested that FFAs with a chain length rC8 are too short to elicit the allosteric switch on albumin. Previous ITC experiments had confirmed that octanoate indeed did not affect the Zn 2+ -binding capacity of BSA.…”

“…67 ICP-MS has also been used to inspect variations in the levels of free metal ions in serum obtained from patients with bipolar disorder undergoing different treatments. 68 Other researchers have employed size exclusion chromatography (SEC) paired with ICP-MS/AES to study metal binding to plasma proteins, [69][70][71][72][73] and the effect of chelating agents on plasma metal speciation. 74,75 In this study, we have also utilised SEC in conjunction with offline ICP-MS analysis to investigate zinc speciation changes in foetal calf serum (FCS) and human blood plasma, upon addition of free fatty acids (FFAs).…”

Time-dependent shotgun proteomics revealed distinct effects of an organoruthenium prodrug and its activation product on colon carcinoma cells

“…24 However, a 2 h treatment revealed a virtually identical organ distribution pattern for plecstatin-1 and its isosteric osmium-analogue, suggesting that the compounds remain largely intact in vivo for this time period. 23 The compounds are probably stabilized by rapid non-covalent binding to serum proteins, 31 which was already observed for the ruthenium(III)-based KP1019. 32 In order to investigate the impact of the hydrolysis behaviour on the target selectivity of plecstatins, time-dependent target profiling experiments were performed using cell lysates of HCT116 colon carcinoma cells.…”

Binding Kinetics of Ruthenium Pyrithione Chemotherapeutic Candidates to Human Serum Proteins Studied by HPLC-ICP-MS

“…For a metalloprotein speciation analysis, the most frequently applied was high-performance liquid chromatography (HPLC) hyphenated to inductively coupled plasma mass spectrometry (ICP-MS) detector. Among HPLC techniques, size exclusion chromatography (SEC) in combination with ICP-MS was used for speciation of metalloproteins [28] and in the investigations of serum binding properties of anticancer agents [29]. However, the low resolution of the SEC, which does not always allow selective separation of proteins, and possible irreversible binding of proteins to the column stationary phase, are the major limitations of this technique.…”