Motexafin gadolinium induces oxidative stress and apoptosis in hematologic malignancies

Crosstalk Between Autophagy and Oxidative Stress in Hematological Malignancies: Mechanisms, Implications, and Therapeutic Potential

Autophagy is a fundamental cellular process that maintains homeostasis by degrading damaged components and regulating stress responses. It plays a crucial role in cancer biology, including tumor progression, metastasis, and therapeutic resistance. Oxidative stress, similarly, is key to maintaining cellular balance by regulating oxidants and antioxidants, with its disruption leading to molecular damage. The interplay between autophagy and oxidative stress is particularly significant, as reactive oxygen species (ROS) act as both inducers and by-products of autophagy. While autophagy can function as a tumor suppressor in early cancer stages, it often shifts to a pro-tumorigenic role in advanced disease, aiding cancer cell survival under adverse conditions such as hypoxia and nutrient deprivation. This dual role is mediated by several signaling pathways, including PI3K/AKT/mTOR, AMPK, and HIF-1α, which coordinate the balance between autophagic activity and ROS production. In this review, we explore the mechanisms by which autophagy and oxidative stress interact across different hematological malignancies. We discuss how oxidative stress triggers autophagy, creating a feedback loop that promotes tumor survival, and how autophagic dysregulation leads to increased ROS accumulation, exacerbating tumorigenesis. We also examine the therapeutic implications of targeting the autophagy-oxidative stress axis in cancer. Current strategies involve modulating autophagy through specific inhibitors, enhancing ROS levels with pro-oxidant compounds, and combining these approaches with conventional therapies to overcome drug resistance. Understanding the complex relationship between autophagy and oxidative stress provides critical insights into novel therapeutic strategies aimed at improving cancer treatment outcomes.

Potential New Therapies "ROS-Based" in CLL: An Innovative Paradigm in the Induction of Tumor Cell Apoptosis

Chronic lymphocytic leukemia, in spite of recent advancements, is still an incurable disease; the majority of patients eventually acquire resistance to treatment through relapses. In all subtypes of chronic lymphocytic leukemia, the disruption of normal B-cell homeostasis is thought to be mostly caused by the absence of apoptosis. Consequently, apoptosis induction is crucial to the management of this illness. Damaged biological components can accumulate as a result of the oxidation of intracellular lipids, proteins, and DNA by reactive oxygen species. It is possible that cancer cells are more susceptible to apoptosis because of their increased production of reactive oxygen species. An excess of reactive oxygen species can lead to oxidative stress, which can harm biological elements like DNA and trigger apoptotic pathways that cause planned cell death. In order to upset the balance of oxidative stress in cells, recent therapeutic treatments in chronic lymphocytic leukemia have focused on either producing reactive oxygen species or inhibiting it. Examples include targets created in the field of nanomedicine, natural extracts and nutraceuticals, tailored therapy using biomarkers, and metabolic targets. Current developments in the complex connection between apoptosis, particularly ferroptosis and its involvement in epigenomics and alterations, have created a new paradigm.

Texaphyrins and water-soluble zinc(II) ionophores: development, mechanism of anticancer activity, and synergistic effects

Texaphyrins, first prepared by Sessler and coworkers in the 1980s, represent early examples of expanded porphyrins. This class of pentaaza, oligopyrrolic macrocycles demonstrates excellent tumor localization and metal-chelating properties. In biological milieus, texaphyrins act as redox mediators and are able to produce reactive oxygen species. Furthermore, texaphyrins have been shown to upregulate zinc in vivo, an important feature that inspired us to develop new zinc ionophores that might allow the same function to be elicited but via a simpler chemical means. In this review, the basic properties of texaphyrins and the zinc ionophores they helped spawn will be discussed in the cadre of developing an understanding that could lead to the preparation of new, redox-active anticancer agents.

Crown ether functionalized texaphyrin monomers and dimers

The synthesis and characterization of two 18-crown-6 functionalized analogues of an extensively studied gadolinium texaphyrin derivative, motexafin gadolinium (1, MGd), are reported. These are the monomeric and dimeric species, compounds 2 and 3, respectively. Both crown ether functionalized species proved to be stable at physiological pH and revealed distinct shifts in the UV spectrum when treated with sodium-, potassium-, ammonium- or zinc(II)-salts. Zinc(II) is believed to play a major role regulating apoptosis mechanisms in cancerous cells. Therefore, cytotoxicity studies of 2 and 3 were carried out using Ramos cell lines in the presence and absence of zinc(II).

Reactive oxygen species: are they important for haematopoiesis?

The production of reactive oxygen species (ROS) has traditionally been related to deleterious effects for cells. However, it is now widely accepted that ROS can play an important role in regulating cellular signalling and gene expression. NADPH oxidase ROS production seems to be especially important in this regard. Some lines of evidence suggest that ROS may be important modulators of cell differentiation, including haematopoietic differentiation, in both physiologic and pathologic conditions. Here we shall review how ROS can regulate cell signalling and gene expression. We shall also focus on the importance of ROS for haematopoietic stem cell (HSC) biology and for haematopoietic differentiation. We shall review the involvement of ROS and NADPH oxidases in cancer, and in particular what is known about the relationship between ROS and haematological malignancies. Finally, we shall discuss the use of ROS as cancer therapeutic targets.

Investigational therapies for brain metastases

Contrary to the incidence of primary cancers, the incidence of brain metastasis has been increasing. This increase is likely because of the effects of an aging population, improved neuroimaging surveillance, and better control of systemic cancer, allowing time for brain metastasis to occur. Unlike systemic cancers, for which chemotherapy is the mainstay of treatment, the therapeutic strategies available to treat brain metastasis have traditionally been limited to surgical resection, whole brain radiation therapy, or stereotactic radiosurgery, either individually or in combination. It is important to put the treatment in the context of the prognosis for patients with brain metastases.

Bismuth- and lead-texaphyrin complexes: towards potential α-core emitters for radiotherapy

Lead(II)-texaphyrins and the first discrete binuclear μ-oxo bismuth(III)-texaphyrin are reported. The latter was characterized via single crystal X-ray diffraction analysis. Cell proliferation assays using the A2780 ovarian cancer cell line were used to determine the cytotoxicity of the complexes.

Redox-directed cancer therapeutics: molecular mechanisms and opportunities

Redox dysregulation originating from metabolic alterations and dependence on mitogenic and survival signaling through reactive oxygen species represents a specific vulnerability of malignant cells that can be selectively targeted by redox chemotherapeutics. This review will present an update on drug discovery, target identification, and mechanisms of action of experimental redox chemotherapeutics with a focus on pro- and antioxidant redox modulators now in advanced phases of preclinal and clinical development. Recent research indicates that numerous oncogenes and tumor suppressor genes exert their functions in part through redox mechanisms amenable to pharmacological intervention by redox chemotherapeutics. The pleiotropic action of many redox chemotherapeutics that involves simultaneous modulation of multiple redox sensitive targets can overcome cancer cell drug resistance originating from redundancy of oncogenic signaling and rapid mutation.Moreover, some redox chemotherapeutics may function according to the concept of synthetic lethality (i.e., drug cytotoxicity is confined to cancer cells that display loss of function mutations in tumor suppressor genes or upregulation of oncogene expression). The impressive number of ongoing clinical trials that examine therapeutic performance of novel redox drugs in cancer patients demonstrates that redox chemotherapy has made the crucial transition from bench to bedside.

Mechanism of inhibition of ribonucleotide reductase with motexafin gadolinium (MGd)

Motexafin gadolinium (MGd) is an expanded porphyrin anticancer agent which selectively targets tumor cells and works as a radiation enhancer, with promising results in clinical trials. Its mechanism of action is oxidation of intracellular reducing molecules and acting as a direct inhibitor of mammalian ribonucleotide reductase (RNR). This paper focuses on the mechanism of inhibition of RNR by MGd. Our experimental data present at least two pathways for inhibition of RNR; one precluding subunits oligomerization and the other direct inhibition of the large catalytic subunit of the enzyme. Co-localization of MGd and RNR in the cytoplasm particularly in the S-phase may account for its inhibitory properties. These data can elucidate an important effect of MGd on the cancer cells with overproduction of RNR and its efficacy as an anticancer agent and not only as a general radiosensitizer.

Motexafin gadolinium-induced cell death correlates with heme oxygenase-1 expression and inhibition of P450 reductase-dependent activities

Heme oxygenase-1 (HO1), which oxidizes heme to biliverdin, CO, and free iron, conveys protection against oxidative stress and is antiapoptotic. Under stress conditions, some porphyrin derivatives can inhibit HO1 and trigger cell death. Motexafin gadolinium (MGd) is an expanded porphyrin that selectively targets cancer cells through a process of futile redox cycling that decreases intracellular reducing metabolites and protein thiols. Here, we report that hematopoietic-derived cell lines that constitutively express HO1 are more susceptible to MGd-induced apoptosis than those that do not. MGd used in combination with tin protoporphyrin IX, an inhibitor of HO1, resulted in synergistic cell killing. Consistent with these cell culture observations, we found that MGd is an inhibitor of heme oxygenase-1 activity in vitro. We demonstrate that inhibition of HO1 reflects an interaction of MGd with NADPH-cytochrome P450 reductase, the electron donor for HO1, that results in diversion of reducing equivalents from heme oxidation to oxygen reduction. In accord with this mechanism, MGd is also an in vitro inhibitor of CYP2C9, CYP3A4, and CYP4A1. Inhibition of HO1 by MGd may contribute to its anticancer activity, whereas its in vitro inhibition of a broad spectrum of P450 enzymes indicates that a potential exists for drug-drug interactions.

Motexafin gadolinium, a tumor-selective drug targeting thioredoxin reductase and ribonucleotide reductase

Motexafin gadolinium (MGd) is a chemotherapeutic drug that selectively targets tumor cells and mediates redox reactions generating reactive oxygen species. Thioredoxin (Trx), NADPH, and thioredoxin reductase (TrxR) of the cytosol/nucleus or mitochondria are major thiol-dependent reductases with many functions in cell growth, defense against oxidative stress, and apoptosis. Mammalian TrxRs are selenocysteine-containing flavoenzymes; MGd was an NADPH-oxidizing substrate for human or rat TrxR1 with a Km value of 8.65 microM (kcat/Km of 4.86 x 10(4) M(-1) s(-1)). The reaction involved redox cycling of MGd by oxygen producing superoxide and hydrogen peroxide. MGd acted as a non-competitive inhibitor (IC50 of 6 microM) for rat TrxR. In contrast, direct reaction between MGd and reduced human Trx was negligible. The corresponding reaction with reduced Escherichia coli Trx was also negligible, but MGd was a better substrate (kcat/Km of 2.23 x 10(5) M(-1) s(-1)) for TrxR from E. coli and a strong inhibitor of Trx-dependent protein disulfide reduction. Ribonucleotide reductase (RNR), a 1:1 complex of the non-identical R1- and R2-subunits, catalyzes the essential de novo synthesis of deoxyribonucleotides for DNA synthesis using electrons from Trx and TrxR. MGd inhibited recombinant mouse RNR activity with either 3 microM reduced human Trx (IC50 2 microM) or 4 mM dithiothreitol (IC50 6 microM) as electron donors. Our results demonstrate MGd-induced enzymatic generation of reactive oxygen species by TrxR plus a powerful inhibition of RNR. This may explain the effects of the drug on cancer cells, which often overproduce TrxR and have induced RNR for replication and repair.