Transient, multi-protein complexes are important facilitators of cellular functions. This includes the chaperome, an abundant protein family comprising chaperones, co-chaperones, adaptors, and folding enzymes—dynamic complexes of which regulate cellular homeostasis together with the protein degradation machinery1–6. Numerous studies have addressed the role of chaperome members in isolation, yet little is known about their relationships regarding how they interact and function together in malignancy7–17. As function is probably highly dependent on endogenous conditions found in native tumours, chaperomes have resisted investigation, mainly due to the limitations of methods needed to disrupt or engineer the cellular environment to facilitate analysis. Such limitations have led to a bottleneck in our understanding of chaperome-related disease biology and in the development of chaperome-targeted cancer treatment. Here we examined the chaperome complexes in a large set of tumour specimens. The methods used maintained the endogenous native state of tumours and we exploited this to investigate the molecular characteristics and composition of the chaperome in cancer, the molecular factors that drive chaperome networks to crosstalk in tumours, the distinguishing factors of the chaperome in tumours sensitive to pharmacologic inhibition, and the characteristics of tumours that may benefit from chaperome therapy. We find that under conditions of stress, such as malignant transformation fuelled by MYC, the chaperome becomes biochemically ‘rewired’ to form a network of stable, survival-facilitating, high-molecular-weight complexes. The chaperones heat shock protein 90 (HSP90) and heat shock cognate protein 70 (HSC70) are nucleating sites for these physically and functionally integrated complexes. The results indicate that these tightly integrated chaperome units, here termed the epichaperome, can function as a network to enhance cellular survival, irrespective of tissue of origin or genetic background. The epichaperome, present in over half of all cancers tested, has implications for diagnostics and also provides potential vulnerability as a target for drug intervention.

NKP-1339 is the first-in-class ruthenium-based anticancer drug in clinical development against solid cancer and has recently been studied successfully in a phase I clinical trial. Ruthenium compounds such as KP1019 (indazolium trans-[tetrachloridobis(1H-indazole)ruthenate(III)]) and NKP-1339 (the sodium salt analogue of KP1019, sodium trans-[tetrachloridobis(1H-indazole)ruthenate(III)]) have a high tumour targeting potential based (1) on their strong binding to serum proteins such as albumin and transferrin as well as (2) on their activation in the reductive tumour milieu. The redox activity of ruthenium compounds is believed to represent one major mode of action leading to disturbance of the cellular redox balance and, consequently, induction of G 2 /M cell cycle arrest, blockage of DNA synthesis, and induction of apoptosis via the mitochondrial pathway. Moreover, potent synergistic activities of NKP-1339 with the clinically approved tyrosine kinase inhibitor sorafenib were recently reported in vitro and in vivo. Taken together, KP1019 and NKP-1339 are promising drug candidates, and especially the very limited side effects observed so far in clinical phase I trials seem to be a major advantage of this class of ruthenium drugs as compared to other chemotherapeutics and targeted anticancer compounds.

The first metal complexes of 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (Triapine) were synthesized. Triapine was prepared by a novel three-step procedure in 64% overall yield. In addition, a series of related ligands, namely, 2-formylpyridine thiosemicarbazone, 2-acetylpyridine thiosemicarbazone, 2-pyridineformamide thiosemicarbazone, and their N(4)-dimethylated derivatives (including the N(4)-dimethylated analogue of Triapine) were prepared, along with their corresponding gallium(III) and iron(III) complexes with the general formula [M(L)(2)](+), where HL is the respective thiosemicarbazone. The compounds were characterized by elemental analysis, (1)H and (13)C NMR, IR and UV-vis spectroscopies, mass spectrometry, and cyclic voltammetry. In addition, Triapine and its iron(III) and gallium(III) complexes were studied by X-ray crystallography. All ligands and complexes were tested for their in vitro antiproliferative activity in two human cancer cell lines (41M and SK-BR-3), and structure-activity relationships were established. In general, the coordination to gallium(III) increased the cytotoxicity while the iron(III) complexes show reduced cytotoxic activity compared to the metal-free thiosemicarbazones. Selected compounds were investigated for the capacity of inhibiting ribonucleotide reductase by incorporation of (3)H-cytidine into DNA.

Ru(II)(arene)-flavonoids with high in vitro antitumour activity were synthesised. These compounds are capable of inhibiting human topoisomerase IIα and binding covalently to DNA.

Intracellular generation of reactive oxygen species (ROS) via thiol-mediated reduction of copper(II) to copper(I) has been assumed as the major mechanism underlying the anticancer activity of copper(II) complexes. The aim of this study was to compare the anticancer potential of copper(II) complexes of Triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone; currently in phase II clinical trials) and its terminally dimethylated derivative with that of 2-formylpyridine thiosemicarbazone and that of 2,2'-bipyridyl-6-carbothioamide. Experiments on generation of oxidative stress and the influence of biologically relevant reductants (glutathione, ascorbic acid) on the anticancer activity of the copper complexes revealed that reductant-dependent redox cycling occurred mainly outside the cells, leading to generation and dismutation of superoxide radicals resulting in cytotoxic amounts of H(2)O(2). However, without extracellular reductants only weak intracellular ROS generation was observed at IC(50) levels, suggesting that cellular thiols are not involved in copper-complex-induced oxidative stress. Taken together, thiol-induced intracellular ROS generation might contribute to the anticancer activity of copper thiosemicarbazone complexes but is not the determining factor.