Advancing the frontiers of colorectal cancer treatment: harnessing ferroptosis regulation

Icariin promoted ferroptosis by activating mitochondrial dysfunction to inhibit colorectal cancer and synergistically enhanced the efficacy of PD-1 inhibitors

BACKGROUND

A controlled type of cell death called ferroptosis is linked to increased reactive oxygen species (ROS), lipid peroxidation, and iron buildup. Furthermore, evidence indicates that ferroptosis may act as an immunogenic form of cell death with potential physiological functions in tumors and immunosuppression. Inducing ferroptosis in tumor cells may have the potential to complement cancer immunotherapy strategies. The development of colorectal cancer (CRC) and the poor efficacy of immunotherapy are associated with the crosstalk of cellular ferroptosis. Currently, Icariin (ICA), the main bioactive component extracted from Epimedium, has been shown to inhibit a variety of cancers. However, the specific role and potential mechanism of ICA in regulating ferroptosis in CRC remains unclear.

PURPOSE

The aim of this investigation was to clarify the mechanism underlying the anti-CRC cancer properties of ICA and how it induces ferroptosis to enhance immunotherapy.

METHODS

To evaluate cell viability, the Cell Counting Kit-8 (CCK-8) test was utilized. The transwell test and the wound healing assay were used to assess cell migration. A subcutaneous graft tumor model was constructed with C57BL/6 mice using MC38 colorectal cancer cell lines. The inhibitory effect of ICA on CRC, ferroptosis level and immunomodulatory effects were detected by serum biochemical assay, cytokine assay, hematoxylin-eosin (H&E) staining, immunofluorescence staining, CyTOF mass spectrometry flow screening and Western blotting. Western blotting, proteomics, molecular docking and microscale thermophoresis (MST) were used to forecast and confirm ICA's binding and interaction with HMGA2, STAT3, and HIF-1α. Moreover, the levels of lipid peroxidation and ferroptosis were assessed through the use of the C11-BODIPY fluorescent probe, the FerroOrange fluorescent probe, the iron level, the malondialdehyde (MDA) and reduced glutathione (GSH) assay kit, and Western blotting analysis. To assess alterations in mitochondrial structure and membrane potential, transmission electron microscopy (TEM) and JC-1 immunofluorescence were employed.

RESULTS

It was demonstrated in the current study that ICA treatment inhibits CRC and enhances anti-PD-1 therapy efficacy by inciting ferroptosis. As shown in vitro, ICA inhibits CRC cell proliferation, migration, and apoptosis. As demonstrated in vivo, ICA has a dose-dependent tumor suppressor effect when combined with anti-PD-1, it can significantly inhibit tumor growth, increase the expression of serum TNF-α, IFN-γ, and granzyme B, and promote CD69+CD8+ T, CD69+CD8+Tem, CD69+CD8+Teff, TCRβ+CD8+ T, TCRβ+CD8+ T, TCRβ+CD8+Tem, TCRβ+CD8+Teff. The inhibitory effect of ICA on CRC was associated with the binding of HMGA2, STAT3, and HIF-1α proteins, which inhibited CRC by increasing the levels of reactive oxygen species (ROS) and malondialdehyde (MDA), promoting the accumulation of iron (Fe2+), depletion of reduced glutathione (GSH), inhibiting SLC7A11 and GPX4 expressions, thereby inducing ferroptosis in CRC. As a consequence of ICA-induced ferroptosis, mitochondria are dysfunctional, with increased ROS production, membrane potential depolarization (MMP), and ATP production reduced. This process can be efficiently reversed by the mitochondria-targeted antioxidant Mito-Q. It is noteworthy that the ferroptosis inhibitor liproxstatin-1 (lip-1), anti-CD8, and anti-IFN-γ exhibited a significant inhibitory effect on the level of ferroptosis and antitumor capacity of ICA combined with anti-PD-1. This finding suggests that the antitumor immunopotentiating effect of ICA on anti-PD-1 is dependent on the secretion of IFN-γ-induced ferroptosis of CRC cells by the CD8+ T cell.

CONCLUSION

Our study represents the inaugural demonstration of the mechanism whereby ICA exerts anti-CRC effects and synergistically enhances the efficacy of anti-PD-1, inducing mitochondrial damage and leading to ferroptosis. ICA promotes ferroptosis of CRC cells by inducing mitochondrial dysfunction, and ICA combined with anti-PD-1 significantly promotes CD69, TCRβ signalling, activates effector CD8+ T cells to secrete IFN-γ, and achieves immunopotentiation by promoting ferroptosis of CRC cells, thus inhibiting CRC development. This study is built upon existing research into the pharmacodynamic mechanisms of ICA in the context of CRC, and offers a novel therapeutic approach in addressing the issue of CRC immunotherapy potentiation.

Ferroptosis and immunosenescence in colorectal cancer

Colorectal cancer (CRC), ranked as the globe's third leading malignancy. Despite advancements in therapeutic approaches, the mortality rate remains distressingly high for those afflicted with advanced stages of the disease. Ferroptosis is a programmed form of cell death. The ways of ferroptosis mainly include promoting the accumulation of cellular ROS and increasing the level of cellular Labile iron pool (LIP). Immunosenescence is characterized by a gradual deterioration of the immune system's ability to respond to pathogens and maintain surveillance against cancer cells. In CRC, this decline is exacerbated by the tumor microenvironment, which can suppress the immune response and promote tumor progression. This paper reviews the relationship between iron prolapse and immune senescence in colorectal cancer, focusing on the following aspects: firstly, the different pathways that induce iron prolapse in colorectal cancer; secondly, immune-immune senescence in colorectal cancer; and lastly, the interactions between immune senescence and iron prolapse in colorectal cancer, e.g., immune-immune senescent cells often exhibit increased oxidative stress, leading to the accumulation of ROS, and consequently to lipid peroxidation and induction of iron-induced cell death. At the same time, ferroptosis induces immune cell senescence as well as alterations in the immune microenvironment by promoting the death of damaged or diseased cells and leading to the inflammation usually associated with it. In conclusion, by exploring the potential targets of ferroptosis and immune senescence in colorectal cancer therapy, we hope to provide a reference for future research.

Vulnerability of Antioxidant Drug Therapies on Targeting the Nrf2-Trp53-Jdp2 Axis in Controlling Tumorigenesis

Control of oxidation/antioxidation homeostasis is important for cellular protective functions, and disruption of the antioxidation balance by exogenous and endogenous ligands can lead to profound pathological consequences of cancerous commitment within cells. Although cancers are sensitive to antioxidation drugs, these drugs are sometimes associated with problems including tumor resistance or dose-limiting toxicity in host animals and patients. These problems are often caused by the imbalance between the levels of oxidative stress-induced reactive oxygen species (ROS) and the redox efficacy of antioxidants. Increased ROS levels, because of abnormal function, including metabolic abnormality and signaling aberrations, can promote tumorigenesis and the progression of malignancy, which are generated by genome mutations and activation of proto-oncogene signaling. This hypothesis is supported by various experiments showing that the balance of oxidative stress and redox control is important for cancer therapy. Although many antioxidant drugs exhibit therapeutic potential, there is a heterogeneity of antioxidation functions, including cell growth, cell survival, invasion abilities, and tumor formation, as well as the expression of marker genes including tumor suppressor proteins, cell cycle regulators, nuclear factor erythroid 2-related factor 2, and Jun dimerization protein 2; their effectiveness in cancer remains unproven. Here, we summarize the rationale for the use of antioxidative drugs in preclinical and clinical antioxidant therapy of cancer, and recent advances in this area using cancer cells and their organoids, including the targeting of ROS homeostasis.

Targeting ferroptosis regulators by natural products in colorectal cancer

Colorectal cancer (CRC) poses a significant global health challenge, ranking as the third most diagnosed cancer and the second leading cause of cancer-related deaths. Despite advancements in treatment, challenges such as delayed diagnosis, multidrug resistance, and limited therapeutic effectiveness persist, emphasizing the need for innovative approaches. This review explores the potential of natural products, nutraceuticals, and phytochemicals for targeting ferroptosis-related regulators as a novel strategy in CRC. Ferroptosis, a form of regulated cell death characterized by iron-dependent lethal lipid peroxide accumulation, holds substantial importance in CRC progression and therapy resistance. Natural products, known for their diverse bioactive effects and favorable safety profiles, emerge as promising candidates to induce ferroptosis in CRC cells. Exploring amino acid, iron, lipid metabolism regulators, and oxidative stress regulators reveals promising avenues for inducing cell death in CRC. This comprehensive review provides insights into the multifaceted effects of natural products on proteins integral to ferroptosis regulation, including GPX4, SLC7A11, ACSL4, NCOA4, and HO-1. By elucidating the intricate mechanisms through which natural products modulate these proteins, this review lays the foundation for a promising therapeutic strategy in CRC.

Exploring the landscape of drug resistance in gastrointestinal cancer immunotherapy: A review

Gastrointestinal (GI) cancers pose a significant challenge due to high prevalence and mortality. While advancements in detection and conventional treatments have been made, prognosis often remains poor, particularly for advanced-stage cancers. Immunotherapy has emerged as a transformative approach, leveraging the body immune system against cancer, including immune checkpoint inhibitors (ICIs), cancer vaccines, and adoptive cell transfer. These modalities have shown promise, achieving sustained responses and improved survival in some patients. However, their efficacy in GI cancers is less pronounced, hindered by drug resistance mechanisms that are either intrinsic or acquired over time. This review examines the latest understanding of immunotherapy in GI cancers, focusing on ICIs, cancer vaccines, and adoptive cell transfer, along with their associated outcomes and limitations. It delves into the mechanisms behind drug resistance, including alterations in immune checkpoints, the immunosuppressive tumor microenvironment, and genetic/epigenetic changes. The role of the gut microbiome is also considered as an emerging factor in resistance. To combat drug resistance, strategies such as enhancing immune response, targeting the tumor microenvironment, and modulating resistance mechanisms are explored. The review underscores the potential of ferroptosis induction as a novel approach. Looking forward, it highlights the need for personalized immunotherapies, understanding the influence of the gut microbiome, and further exploration of ferroptosis in overcoming resistance. While challenges persist, the continuous evolution in GI cancer immunotherapy research promises innovative treatments that could significantly improve patient outcomes.