Based on the multifaceted molecular machinery that tightly controls iron cellular homeostasis, this review delves into its paradoxical, potentially dangerous role in biological systems, with a special focus on double-edged sword correlations with cancer. Indeed, though iron is a vital micronutrient and a required cofactor participating in several essential cell functions, its tendency to cause oxidative stress can be related both to cancer risk and to the activation of cancer cell death pathways. In this scenario, ferroptosis refers to an iron-dependent form of regulated cell death (RCD) powered by an overload of lethal peroxides sharing distinctive oxidized phospholipid profiles. As a unique cell death pathway, ferroptosis is both morphologically and mechanistically different from other types of programmed cell death involving executioner family proteins. The accumulation of cytotoxic lipid peroxides encompasses a cellular antagonism between ferroptosis execution and defense systems, with iron-dependent death occurring when ferroptosis-promoting activities significantly exceed the cellular antioxidant defenses. The most recent molecular breakthroughs in the execution of ferroptosis have aroused great consideration in tumor biology, as targeting ferroptosis can provide new tools for exploring therapeutic strategies for tumor suppression. Mutations and death/survival pathway alterations, as well as distinctive metabolic regulations of cancer cells, including the propensity to generate ROS, are seen as features that can render cancer cells unprotected to ferroptosis, thereby exposing vulnerabilities which deserve further attention to be regarded as targetable for cancers with limited therapeutic options.

This research focuses on the target deconvolution of the natural compound myrianthic acid, a triterpenoid characterized by an ursane skeleton isolated from the roots of Myrianthus arboreus and from Oenothera maritima Nutt. (Onagraceae), using MS-based chemical proteomic techniques. Application of drug affinity responsive target stability (DARTS) and targeted-limited proteolysis coupled to mass spectrometry (t-LiP-MS) led to the identification of the enzyme fatty acid synthase (FAS) as an interesting macromolecular counterpart of myrianthic acid. This result, confirmed by comparison with the natural ursolic acid, was thoroughly investigated and validated in silico by molecular docking, which gave a precise picture of the interactions in the MA/FAS complex. Moreover, biological assays showcased the inhibitory activity of myrianthic acid against the FAS enzyme, most likely related to its antiproliferative activity towards tumor cells. Given the significance of FAS in specific pathologies, especially cancer, the myrianthic acid structural moieties could serve as a promising reference point to start the potential development of innovative approaches in therapy.

This study explores the potential of Arbutus unedo L. pomace, a by-product of the food industry, as a natural ingredient for skincare applications. In Portugal, A. unedo L. fruits are traditionally used to produce “Aguardente de Medronho”, a spirit with a protected geographical indication. The distillation process generates pomace, comprising skins, pulp remnants, seeds, and residual alcohol rich in phenolic compounds, whose levels are significantly increased during distillation. In addition to their documented high antioxidant content, these residues also display notable antimicrobial properties. However, their potential benefits for skin health have not yet been explored. The methodology entailed the preparation of the pomace extract and a comprehensive analysis of its polyphenolic content and antioxidant capacity under laboratory conditions and in preclinical cellular models. The by-products demonstrated a high polyphenol content and potent antioxidant activity, comparable to vitamin C. Bioscreening on human skin models (i.e., dermal fibroblasts and keratinocytes) revealed their ability to reduce reactive oxygen species (ROS) formation under oxidative stress in skin cells, highlighting their potential to mitigate skin aging and damage caused by environmental pollutants. Moreover, bioscreens in vitro revealed a high safety profile, without any interference with cell viability at concentrations up to 100 µg/mL. These findings support the use of A. unedo L. pomace extract as a sustainable ingredient for the development of antioxidant-rich and eco-friendly cosmetic or dermatologic products.

Background/Objectives: In the context of preclinical studies, we have hitherto showcased that a low-molecular-weight ruthenium(III) complex we named AziRu holds significant potential for further developments as an anticancer candidate drug. When appropriately converted into stable nanomaterials and delivered into tumor cells, AziRu exhibits superior antiproliferative activity, benefiting from a multimodal mechanism of action. The activation of regulated cell death (RCD) pathways (i.e., apoptosis and autophagy) has been proved in metastatic phenotypes, including triple-negative breast cancer (TNBC) cells. This study focuses on a bioengineered lipophilic derivative of AziRu, named PalmiPyRu, that we are currently developing as a potential anticancer drug in preclinical studies. When delivered in this way, AziRu confirms a multimodal mechanism of action in effectively blocking the growth and proliferation of TNBC phenotypes. Special focus is reserved for the activation of the ferroptotic pathway as a consequence of redox imbalance and interference with iron homeostasis, as well as the glutathione biosynthetic pathway. Methods: Human preclinical models of specific TNBC phenotypes and healthy cell cultures of different histological origin were selected. After in vitro treatments, cellular responses were carefully analyzed, and targeted biochemical and molecular biology experiments coupled to confocal microscopy allowed us to explore the antiproliferative effects of PalmiPyRu. Results: In this study, we unveil that PalmiPyRu can enter TNBC cells and interfere with both the iron homeostasis and the cystine-glutamate antiporter system Xc-, causing significant oxidative stress and the accumulation of lipid oxidation products. The increase in intracellular reactive free iron and depletion of glutathione engender a lethal condition, driving cancer cells toward the activation of ferroptosis. Conclusions: Overall, these outcomes allow us, for the first time, to couple the antiproliferative effect of a ruthenium-based candidate drug with the inhibition of the Xc- antiporter system and Fenton chemistry, thereby branding PalmiPyRu as an effective multimodal inducer of ferroptosis. Molecular mechanisms of action deserve further investigations, and new studies are underway to uncover how interference with Xc- controls cell fate, allowing us to explore the connection between iron metabolism regulation, oxidative stress and RCD pathways activation.