Abstract The central role of iron in tumor progression and metastasis motivates the development of iron‐binding approaches in cancer chemotherapy. Disulfide‐based prochelators are reductively activated upon cellular uptake to liberate thiol chelators responsible for iron sequestration. Herein, a trimethyl thiosemicarbazone moiety and the imidazole‐2‐thione heterocycle are incorporated in this prochelator design. Iron binding of the corresponding tridentate chelators leads to the stabilization of a low‐spin ferric center in 2 : 1 ligand‐to‐metal complexes. Native mass spectrometry experiments show that the prochelators form stable disulfide conjugates with bovine serum albumin, thus affording novel bioconjugate prochelator systems. Antiproliferative activities at sub‐micromolar levels are recorded in a panel of breast, ovarian and colorectal cancer cells, along with significantly lower activity in normal fibroblasts.
Tridentate aroyl hydrazones are effective metal chelators in biological settings, and their activity has been investigated extensively for medicinal applications in metal overload, cancer, and neurodegenerative diseases. The aroyl hydrazone motif is found in the recently reported prochelator (AH1-S)
Abstract Transition metals are essential for the function for numerous metalloproteins and cofactors in living systems. Their acquisition, transport, and storage are tightly regulated and the homeostasis of redox‐active cations such as iron and copper is especially critical to prevent the damaging effects of oxidative stress. Indeed the dyshomeostasis of metals has been observed in the pathophysiology of several diseases, and multiple metal‐binding compounds are currently under investigation as therapeutic candidates. Herein, we focus on the altered metal metabolisms of malignant cells and on metal‐binding strategies for the design of cancer chemotherapeutics. Iron, copper, and zinc chelators with a variety of binding motifs have been studied for their antiproliferative effects in malignant cells, and several compounds have reached clinical trials. Recent pro‐chelation approaches, in which the chelator is activated under specific conditions, are poised to increase therapeutic indexes and avoid unwanted side effects. As additional information emerges on the roles of metals in cancer biology, the design of metal‐binding drug candidates is evolving to improve their selectivity and efficacy and to consider their effects on the immune cells present in the tumor microenvironment. In addition, extensive studies to develop inhibitors of metalloenzymes relevant to cancer growth have led to several new anticancer therapeutics that coordinate the zinc centers in the active site of the enzymes. As illustrated by the examples collected herein, approaches that target either labile or protein‐bound transition metals have significant potential to produce new therapeutic options for cancer treatment.
The Front Cover shows the bioconjugation of an antiproliferative prochelator to serum albumin via formation of a disulfide bond with a reduced cysteine on the protein. The abundance of albumin in blood is represented by the red background featuring red blood cells. The disulfide-masked prochelators of this class have antiproliferative activities at submicromolar levels in a panel of cancer cell lines. Cover design by Matthew W. Lluis. More information can be found in the Communication by Elisa Tomat et al..
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