Transferrin binding and transferrin-mediated cellular uptake of the ruthenium coordination compound KP1019, studied by means of AAS, ESI-MS and CD spectroscopy

Abstract

Indazolium trans-[tetrachlorobis(1H-indazole)ruthenate(III)] (KP1019) shows particular promise as an antitumour agent against colorectal cancer. It is known that KP1019 reacts with human serum proteins, whereby the major amount binds to albumin (present in large excess) and a smaller amount to transferrin. It has been hypothesised that transferrin-mediated uptake by transferrin receptor expressing tumour cells may in part explain the apparent tumour selectivity of this compound. Circular dichroism spectroscopy and electrospray ionisation mass spectrometry studies demonstrate that two equivalents of KP1019 bind specifically to human apotransferrin, while additional amounts of the ruthenium complex bind unspecifically. Uptake studies in the transferrin receptor-expressing human colon carcinoma cell line SW480 revealed a higher cellular accumulation of KP1019 in comparison to a KP1019-transferrin adduct (2:1), while the uptake of a KP1019-Fe(III)-transferrin conjugate (1:0.3:1) significantly exceeded that of KP1019, suggesting that iron binding is necessary to obtain a protein conformation which favours recognition by the transferrin receptors on the cell surface. Our study showed that KP1019 is transported into the cell by both transferrin-independent and transferrin-dependent mechanisms. Transferrin-mediated uptake is more efficient when transferrin is saturated with iron to a physiological degree (y30%). Cell fractionation experiments demonstrated that after a 2 h treatment of human colon cancer cells with 10 mM KP1019 on average 55% of the intracellular ruthenium is located in the cellular nucleus, while 45% remain in the cytosol and other cellular components.

Capillary electrophoresis hyphenated to inductively coupled plasma‐mass spectrometry: A novel approach for the analysis of anticancer metallodrugs in human serum and plasma

“…1) which showed promise in a clinical phase I trial in terms of activity but also low toxicity [38][39][40]. The latter properties are thought to be related to its selective mode of action comprising the transport into the tumor via the Tf cycle and the reduction in the tumoral tissue [19,41,42]. Recent studies on the binding to plasma proteins showed a kinetic preference for the binding to Tf but higher binding constants for albumin, both being important transport proteins for drugs [10,11,31].…”

Interactions of arene ruthenium metallaprisms with human proteins

“…46 Interestingly, the results found for these three metallaprisms are in contrast to those observed with other ruthenium complexes. For instance, KP1019 was shown to bind to apoTf as evidenced by ESI-mass and CD spectra, 47 and RAPTA-C was shown to bind to Ub and metallothionein-2. 48 All NMR and MS experiments strongly suggest that no covalent binding takes place between the metallaprisms and the five selected proteins.…”

Sawhorse-type diruthenium tetracarbonyl complexes containing porphyrin-derived ligands as highly selective photosensitizers for female reproductive cancer cells

“…The 3-(4,5-dimethyl-2-thiazoyl)-2,5-diphenyltetrazolium bromide cell survival test was performed 24 h after the irradiation. The LD 50 values (light dose necessary to inhibit 50% cell survival) were determined using the medium effect algorithm [27] that the complexes are taken up by HeLa, Ovcar, and A2780 cells and concentrate in the cell cytoplasm and organelles, but not in the nucleus, as did our previously reported compounds [19,20] but this contrasts with some ruthenium-based drugs known to accumulate in the nucleus [33,34]. Photodynamic studies provided coherent results compared with uptake studies since our complexes induce phototoxicities in HeLa cervix and A2780 ovary carcinoma cell lines and not in other cancer and normal fibroblast cells.…”