The action of proteases can be controlled by several mechanisms, including regulation through gene expression; post-translational modifications, such as glycosylation; zymogen activation; targeting specific compartments, such as lysosomes and mitochondria; and blocking proteolysis using endogenous inhibitors. Protease inhibitors are important molecules to be explored for the control of proteolytic processes in organisms because of their ability to act on several proteases. In this context, plants synthesize numerous proteins that contribute to protection against attacks by microorganisms (fungi and bacteria) and/or invertebrates (insects and nematodes) through the inhibition of proteases in these organisms. These proteins are widely distributed in the plant kingdom, and are present in higher concentrations in legume seeds (compared to other organs and other botanical families), motivating studies on their inhibitory effects in various organisms, including humans. In most cases, the biological roles of these proteins have been assigned based mostly on their in vitro action, as is the case with enzyme inhibitors. This review highlights the structural evolution, function, and wide variety of effects of plant Kunitz protease inhibitors, and their potential for pharmaceutical application based on their interactions with different proteases.

The NRF2 pathway has emerged as a central regulator of cellular redox homeostasis, coordinating the expression of a broad array of genes that protect cells from oxidative and electrophilic stress. In the context of cancer, NRF2 has been recognized as a key driver of chemoresistance, as its sustained activation enhances antioxidant defenses, detoxification pathways, and metabolic adaptation, thereby promoting tumor cell survival under therapeutic stress. Beyond its canonical role in redox regulation, NRF2 also orchestrates the expression of multiple genes involved in ferroptosis, a non-apoptotic, iron-dependent form of cell death that has recently gained attention as a promising strategy to overcome drug resistance. Mechanistically, NRF2 modulates ferroptosis through several interconnected pathways, including the regulation of glutathione biosynthesis, lipid metabolism, and iron homeostasis, yet its impact is highly context-dependent and can vary according to cell type and metabolic state. In this review, we provide an overview of the interplay between NRF2 and ferroptosis, tracing the historical development of this network and highlighting the pivotal roles of specific NRF2 targets in controlling ferroptotic susceptibility. Finally, we discuss how targeted modulation of NRF2 may influence ferroptosis, offering a potential avenue for the design of innovative therapies aimed at selectively eradicating resistant tumors.

In the search for alternatives to overcome the challenge imposed by drug resistance development in cancer treatment, the modulation of autophagy has emerged as a promising alternative that has achieved good results in clinical trials. Nevertheless, most of these studies have overlooked a novel and selective type of autophagy: chaperone-mediated autophagy (CMA). Following its discovery, research into CMA’s contribution to tumor progression has accelerated rapidly. Therefore, we now understand that stress conditions are the primary signal responsible for modulating CMA in cancer cells. In turn, the degradation of proteins by CMA can offer important advantages for tumorigenesis, since tumor suppressor proteins are CMA targets. Such mutual interaction between the tumor microenvironment and CMA also plays a crucial part in establishing therapy resistance, making this discussion the focus of the present review. Thus, we highlight how suppression of LAMP2A can enhance the sensitivity of cancer cells to several drugs, just as downregulation of CMA activity can lead to resistance in certain cases. Given this panorama, it is important to identify selective modulators of CMA to enhance the therapeutic response.

In this study, cyclometallated gold(III) compounds were evaluated for their capability to promote C-Se coupling reactions under biocompatible conditions, and their chemoselectivity towards selenium-containing substrates compared to sulfur-containing analogs. The compounds exhibited varying degrees of selectivity towards selenium-containing compounds, with [Au(bnopy)Cl₂] showing rapid C-Se bond formation. Competitive reactions with selenium and sulfur substrates highlighted the preference for selenium, especially for [Au(Mephpy)Cl₂], even in the presence of excess sulfur substrates. This selectivity was further confirmed in selenopeptide models mimicking the GPx active site, where arylation of selenocysteine was observed. The compounds were further investigated as inhibitors of selenoprotein glutathione peroxidase (GPx) isoenzymes, specifically GPx1 and GPx4. The six-membered metallacycles [Au(bnpy)Cl₂] and [Au(bnopy)Cl₂] exhibited potent inhibition of the GPx1 isoenzyme, particularly when co-incubated with reducing agents, while in vitro GPx4 inhibition was overall less pronounced. Notably, [Au(Mephpy)Cl₂] showed inhibition of GPx1 with no cross-inhibition of the non-selenoprotein glutathione reductase (GR). LC/MS studies identified selenocysteine (Sec51) as the primary arylation site on GPx1 by [Au(bnpy)Cl₂], highlighting its chemoselectivity. Finally, we demonstrated that the selectivity towards Sec could also be translated to an intracellular setting, using a A375 GPx4 WT cell line and an A375 GPx4 U46C mutant. Viability assays revealed a modest decrease in the IC50 for GPx4 WT cells compared to U46C mutants for both [Au(bnpy)Cl₂] and [Au(Mephpy)Cl₂]. More clearly, a proliferation assay over six days showed greater effect in GPx4 WT cells compared to the U46C mutant when treated with [Au(Mephpy)Cl₂], an effect further enhanced by co-treatment with iFSP1. This indicates a GPx4 Sec-dependent response to treatment in A375 cells and warrants further mechanistic studies.

Although great advances have been made in cancer treatment, lung cancer and glioblastoma patients continue to present a dismal prognosis, mainly due to drug resistance. Evidence suggests that NRF2 and glutathione (GSH) play a fundamental role in chemotherapy resistance. Notably, GSH depletion by buthionine sulfoximine (BSO) has been demonstrated to sensitize human tumor cells to a wide variety of chemotherapeutic agents. However, the incorporation of BSO into standard chemotherapy regimens lacks a robust clinical rationale. In this study, we aimed to investigate the mechanisms governing differential sensitivity to chemotherapy in lung cancer and glioblastoma cells to identify novel strategies to enhance outcomes in these malignancies. For this purpose, we analyzed several cellular responses in cell lines exhibiting distinct sensitivities to temozolomide (TMZ) and cisplatin. Our findings indicate that the NRF2/GSH pathway plays a crucial role in TMZ and cisplatin resistance and that pharmacological GSH depletion enhances the sensitivity of NRF2-high, chemotherapy-resistant cells to these agents. Furthermore, BSO in combination with TMZ or cisplatin enhanced chemotherapy-induced cytotoxicity and engaged both apoptotic and ferroptosis-related responses in NSCLC cells. These findings provide preclinical evidence supporting further investigation of NRF2/GSH targeting as a strategy to overcome chemotherapy resistance. Graphical abstract

Modulating the intracellular labile iron pool (LIP) has emerged as a promising strategy to induce ferroptosis in cancer cells, offering a way to overcome resistance to apoptosis-based therapies. One of the main contributors to LIP is heme catabolism mediated by heme oxygenase-1 (HMOX1), which promotes ferroptosis sensitivity by releasing free iron. Beyond its role as an iron donor, heme can influence diverse proteins and signaling pathways that drive tumor progression, but how heme regulates ferroptosis remains poorly understood. Here, we uncover a paradoxical, protective function of heme in the absence of HMOX1 activity. When HMOX1 is inactive, heme becomes stabilized, leading to ferritin up-regulation, suppression of ferroptosis, and rescue of cell death induced by both pharmacological and genetic inhibition of GPX4. Our findings reveal an unrecognized heme-HMOX1-ferritin axis that controls ferroptosis sensitivity. Targeting this pathway may offer a new therapeutic strategy to modulate ferroptosis in cancer.