Pumping Iron: Ferritinophagy Promotes Survival and Therapy Resistance in Pancreatic Cancer

Autophagy and the pancreas: Healthy and disease states

Macroautophagy/autophagy is an intracellular degradation pathway that has an important effect on both healthy and diseased pancreases. It protects the structure and function of the pancreas by maintaining organelle homeostasis and removing damaged organelles. A variety of pancreas-related diseases, such as diabetes, pancreatitis, and pancreatic cancer, are closely associated with autophagy. Genetic studies that address autophagy confirm this view. Loss of autophagy homeostasis (lack or overactivation) can lead to a series of adverse reactions, such as oxidative accumulation, increased inflammation, and cell death. There is growing evidence that stimulating or inhibiting autophagy is a potential therapeutic strategy for various pancreatic diseases. In this review, we discuss the multiple roles of autophagy in physiological and pathological conditions of the pancreas, including its role as a protective or pathogenic factor.

G3BP2 promotes tumor progression and gemcitabine resistance in PDAC via regulating PDIA3-DKC1-hENT in a stress granules-dependent manner

Pancreatic ductal adenocarcinoma (PDAC) is distinguished by its aggressive malignancy, limited treatment avenues and a tendency towards chemotherapy resistance, underscoring the critical need for advanced research to uncover new therapeutic approaches. Stress granules (SGs) that is implicated in cellular self-protection mechanism, along with its associated family molecules have shown pro-cancer effects and are closely related to tumor chemotherapy resistance. In this study we investigated the relationship between Ras GTPase-activating protein-binding proteins 2 (G3BP2), a core component of SGs, and the malignancy of PDAC as well as its resistance to the chemotherapy drug gemcitabine. Analyzing TCGA dataset revealed that the expression of G3BP1 and G3BP2 was significantly upregulated in PDAC compared with adjacent normal pancreatic tissues, and the high expression of G3BP2 rather than G3BP1 was significantly associated with poorer overall survival (OS) in PDAC patients. We demonstrated that knockdown of G3BP2 inhibited the proliferation and invasion of PANC-1 and CFPAC-1 cells in vitro and in vivo. By analyzing the differentially expressed genes in G3BP2 knockdown and overexpressed PANC-1 cells, we identified DKC1 that was associated with RNA stability and regulation as the target of G3BP2. We demonstrated that G3BP2 bound to PDIA3 mRNA and recruited them into SGs, increasing the stability of PDIA3 mRNA and attenuating its translation efficiency, thereby promoting DKC1 expression. Furthermore, DKC1 could bind to hENT mRNA and inhibited its expression, which enhanced gemcitabine resistance of PDAC. Therefore, we propose a novel mechanism wherein G3BP2 facilitates PDAC's resistance to chemotherapy by modulating PDIA3-DKC1-hENT in a SGs-dependent way, suggesting G3BP2 SGs a protentional therapeutic target for the treatment in PDAC.

A promising new approach to cancer therapy: Manipulate ferroptosis by hijacking endogenous iron

Ferroptosis, a form of regulated cell death characterized by iron-dependent phospholipid peroxidation, has emerged as a focal point in the field of cancer therapy. Compared with other cell death modes such as apoptosis and necrosis, ferroptosis exhibits many distinct characteristics in the molecular mechanisms and cell morphology, offering a promising avenue for combating cancers that are resistant to conventional therapeutic modalities. In light of the serious side effects associated with current Fenton-modulating ferroptosis therapies utilizing exogenous iron-based inorganic nanomaterials, hijacking endogenous iron could serve as an effective alternative strategy to trigger ferroptosis through targeting cellular iron regulatory mechanisms. A better understanding of the underlying iron regulatory mechanism in the process of ferroptosis has shed light on the current findings of endogenous ferroptosis-based nanomedicine strategies for cancer therapy. Here in this review article, we provide a comprehensive discussion on the regulatory network of iron metabolism and its pivotal role in ferroptosis, and present recent updates on the application of nanoparticles endowed with the ability to hijack endogenous iron for ferroptosis. We envision that the insights in the study may expedite the development and translation of endogenous ferroptosis-based nanomedicines for effective cancer treatment.

Targeted ferritinophagy in gastrointestinal cancer: from molecular mechanisms to implications

Gastrointestinal cancer is a significant global health burden, necessitating the development of novel therapeutic strategies. Emerging evidence has highlighted the potential of targeting ferritinophagy as a promising approach for the treatment of gastrointestinal cancer. Ferritinophagy is a form of selective autophagy that is mediated by the nuclear receptor coactivator 4 (NCOA4). This process plays a crucial role in regulating cellular iron homeostasis and has been implicated in various pathological conditions, including cancer. This review discusses the molecular mechanisms underlying ferritinophagy and its relevance to gastrointestinal cancer. Furthermore, we highlight the potential therapeutic implications of targeting ferritinophagy in gastrointestinal cancer. Several approaches have been proposed to modulate ferritinophagy, including small molecule inhibitors and immunotherapeutic strategies. We discuss the advantages and challenges associated with these therapeutic interventions and provide insights into their potential clinical applications.

Hypoxia inhibits ferritinophagy-mediated ferroptosis in esophageal squamous cell carcinoma via the USP2-NCOA4 axis

Esophageal squamous cell carcinoma (ESCC) is a prevalent malignancy of the digestive system. Hypoxia is a crucial player in tumor ferroptosis resistance. However, the molecular mechanism of hypoxia-mediated ferroptosis resistance in ESCC remains unclear. Here, USP2 expression was decreased in ESCC cell lines subjected to hypoxia treatment and was lowly expressed in clinical ESCC specimens. Ubiquitin-specific protease 2 (USP2) depletion facilitated cell growth, which was blocked in USP2-overexpressing cells. Moreover, USP2 silencing enhanced the iron ion concentration and lipid peroxidation accumulation as well as suppressed ferroptosis, while upregulating USP2 promoted ferroptotic cell death in ESCC cells. Furthermore, knockout of USP2 in ESCC models discloses the essential role of USP2 in promoting ESCC tumorigenesis and inhibiting ferroptosis. In contrast, overexpression of USP2 contributes to antitumor effect and ferroptosis events in vivo. Specifically, USP2 stably bound to and suppressed the degradation of nuclear receptor coactivator 4 (NCOA4) by eliminating the Lys48-linked chain, which in turn triggered ferritinophagy and ferroptosis in ESCC cells. Our findings suggest that USP2 plays a crucial role in iron metabolism and ferroptosis and that the USP2/NCOA4 axis is a promising therapeutic target for the management of ESCC.

Myeloid NCOA4 sequesters KEAP1 to reduce ferroptosis for protection against salmonellosis in mice

Salmonellosis, caused by Salmonella enterica serovar Typhimurium, is a significant global threat. Host immunity limits bacterial replication by inducing hepcidin, which degrades ferroportin, reducing iron transfer. However, this boosts macrophage iron storage, aiding intracellular pathogens like Salmonella. Mice lacking ferritin heavy chain (FTH1) in myeloid cells suffer worsened Salmonella infection. Nuclear receptor co-activator 4 (NCOA4) regulates iron release via FTH1 degradation during low iron, but its role in salmonellosis is unclear. Here, we reveal that myeloid NCOA4 deficiency augments spleen iron levels and increases cellular iron accumulation, oxidative stress, and ferroptosis in bone marrow-derived macrophages. This deficiency also increases susceptibility to Salmonella-induced colitis in mice. Mechanistically, NCOA4 suppresses oxidative stress by directly binding to the E3 ubiquitin ligase Kelch-like ECH-associated protein 1 (KEAP1) and stabilizing the antioxidant transcription factor nuclear factor-erythroid 2-related factor 2 (NRF2). Activation of NRF2 protects myeloid NCOA4 knockout mice from Salmonella-induced colitis. Antioxidant Tempol and myeloid cell-targeted curcumin offer protection against colitis in myeloid NCOA4-deficient mice. A low iron diet and ferroptosis inhibition also mitigate the heightened colitis in these mice. Overexpression of myeloid cell-specific NCOA4 confers protection against Salmonella-induced colitis via upregulating NRF2 signaling. Serum iron was reduced in myeloid NCOA4-overexpressing mice, but not in NCOA4-deficient mice. Targeted serum metabolomics analysis revealed that many lipids were decreased in myeloid NCOA4-deficient mice, while several of them were increased in myeloid NCOA4-overexpressing mice. Together, this study not only advances our understanding of NCOA4/KEAP1/NRF2/ferroptosis axis but also paves the way for novel myeloid cell-targeted therapies to combat salmonellosis.

Ferritinophagy: research advance and clinical significance in cancers

Ferritinophagy, a process involving selective autophagy of ferritin facilitated by nuclear receptor coactivator 4 (NCOA4), entails the recognition of ferritin by NCOA4 and subsequent delivery to the autophagosome. Within the autophagosome, ferritin undergoes degradation, leading to the release of iron in the lysosome. It is worth noting that excessive iron levels can trigger cell death. Recent evidence has elucidated the significant roles played by ferritinophagy and ferroptosis in regulation the initiation and progression of cancer. Given the crucial role of ferritinophagy in tumor biology, it may serve as a potential target for future anti-tumor therapeutic interventions. In this study, we have provided the distinctive features of ferritinophagy and its distinctions from ferroptosis. Moreover, we have briefly examined the fundamental regulatory mechanisms of ferritinophagy, encompassing the involvement of the specific receptor NCOA4, the Nrf2/HO-1 signaling and other pathways. Subsequently, we have synthesized the current understanding of the impact of ferritinophagy on cancer progression and its potential therapeutic applications, with a particular emphasis on the utilization of chemotherapy, nanomaterials, and immunotherapy to target the ferritinophagy pathway for anti-tumor purposes.

Recent advances in targeting autophagy in cancer

Autophagy is a cellular homeostasis mechanism that fuels the proliferation and survival of advanced cancers by degrading and recycling organelles and proteins. Preclinical studies have identified that within an established tumor, tumor cell autophagy and host cell autophagy conspire to support tumor growth. A growing body of evidence suggests that autophagy inhibition can augment the efficacy of chemotherapy, targeted therapy, or immunotherapy to enhance tumor shrinkage. First-generation autophagy inhibition trials in cancer using the lysosomal inhibitor hydroxychloroquine (HCQ) have produced mixed results but have guided the way for the development of more potent and specific autophagy inhibitors in clinical trials. In this review, we will discuss the role of autophagy in cancer, newly discovered molecular mechanisms of the autophagy pathway, the effects of autophagy modulation in cancer and host cells, and novel autophagy inhibitors that are entering clinical trials.