Hypoxia-inducible factor 3α1 increases epithelial-to-mesenchymal transition and iron uptake to drive colorectal cancer liver metastasis.

BACKGROUND/OBJECTIVES: Hypoxia-inducible factor (HIF)-3α1's role in colorectal cancer (CRC) cells, especially its effects on epithelial-mesenchymal transition (EMT), zinc finger E-box binding homeobox 2 (ZEB2) gene expression, and iron metabolism, remains largely unstudied. This research sought to elucidate these relationships. METHODS: RNA-seq was conducted to investigate the impact of HIF-3α1 overexpression in CRC cells. Dual-luciferase reporter assays assessed the direct targeting of ZEB2 by HIF-3α1. Scratch assays measured changes in cell migration following HIF-3α1 overexpression and ZEB2 knockdown. The effects of HIF-3α1 overexpression on colon tumour growth and liver metastasis were examined in vivo. Iron chelation was used to explore the role of iron metabolism in HIF-3α1-mediated EMT and tumour growth. RESULTS: HIF-3α1 overexpression induced EMT and upregulated ZEB2 expression, enhancing cancer cell migration. ZEB2 knockdown reduced mesenchymal markers and cell migration. HIF-3α1 promoted colon tumour growth and liver metastasis, increased transferrin receptor (TFRC) expression and cellular iron levels, and downregulated HIF-1α, HIF-2α, and NDRG1. Iron chelation mitigated HIF-3α1-mediated EMT, tumour growth, and survival. CONCLUSIONS: HIF-3α1 plays a critical role in colon cancer progression by promoting EMT, iron accumulation, and metastasis through ZEB2 and TFRC regulation, suggesting potential therapeutic targets in CRC.

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.

The emerging role of hypoxia and environmental factors in inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a chronic and debilitating disorder characterized by inflammation of the gastrointestinal tract. Despite extensive research, the exact cause of IBD remains unknown, hampering the development of effective therapies. However, emerging evidence suggests that hypoxia, a condition resulting from inadequate oxygen supply, plays a crucial role in intestinal inflammation and tissue damage in IBD. Hypoxia-inducible factors (HIFs), transcription factors that regulate the cellular response to low oxygen levels, have gained attention for their involvement in modulating inflammatory processes and maintaining tissue homeostasis. The two most studied HIFs, HIF-1α and HIF-2α, have been implicated in the development and progression of IBD. Toxicological factors encompass a wide range of environmental and endogenous agents, including dietary components, microbial metabolites, and pollutants. These factors can profoundly influence the hypoxic microenvironment within the gut, thereby exacerbating the course of IBD and fostering the progression of colitis-associated colorectal cancer. This review explores the regulation of hypoxia signaling at the molecular, microenvironmental, and environmental levels, investigating the intricate interplay between toxicological factors and hypoxic signaling in the context of IBD, focusing on its most concerning outcomes: intestinal fibrosis and colorectal cancer.

Iron promotes glycolysis to drive colon tumorigenesis.

Colorectal cancer (CRC) is the third most common cancer and is also the third leading cause of cancer-related death in the USA. Understanding the mechanisms of growth and progression of CRC is essential to improve treatment. Macronutrients such as glucose are energy source for a cell. Many tumor cells exhibit increased aerobic glycolysis. Increased tissue micronutrient iron levels in both mice and humans are also associated with increased colon tumorigenesis. However, if iron drives colon carcinogenesis via affecting glucose metabolism is still not clear. Here we found the intracellular glucose levels in tumor colonoids were significantly increased after iron treatment. 13C-labeled glucose flux analysis indicated that the levels of several labeled glycolytic products were significantly increased, whereas several tricarboxylic acid cycle intermediates were significantly decreased in colonoids after iron treatment. Mechanistic studies showed that iron upregulated the expression of glucose transporter 1 (GLUT1) and mediated an inhibition of the pyruvate dehydrogenase (PDH) complex function via directly binding with tankyrase and/or pyruvate dehydrogenase kinase (PDHK) 3. Pharmacological inhibition of GLUT1 or PDHK reactivated PDH complex function and reduced high iron diet-enhanced tumor formation. In conclusion, excess iron promotes glycolysis and colon tumor growth at least partly through the inhibition of the PDH complex function.

Transferrin Receptor-Mediated Iron Uptake Promotes Colon Tumorigenesis.

Transferrin receptor (TFRC) is the major mediator for iron entry into a cell. Under excessive iron conditions, TFRC is expected to be reduced to lower iron uptake and toxicity. However, the mechanism whereby TFRC expression is maintained at high levels in iron-enriched cancer cells and the contribution of TFRC to cancer development are enigmatic. Here the work shows TFRC is induced by adenomatous polyposis coli (APC) gene loss-driven ß-catenin activation in colorectal cancer, whereas TFRC-mediated intratumoral iron accumulation potentiates ß-catenin signaling by directly enhancing the activity of tankyrase. Disruption of TFRC leads to a reduction of colonic iron levels and iron-dependent tankyrase activity, which caused stabilization of axis inhibition protein 2 (AXIN2) and subsequent repression of the ß-catenin/c-Myc/E2F Transcription Factor 1/DNA polymerase delta1 (POLD1) axis. POLD1 knockdown, iron chelation, and TFRC disruption increase DNA replication stress, DNA damage response, apoptosis, and reduce colon tumor growth. Importantly, a combination of iron chelators and DNA damaging agents increases DNA damage response and reduces colon tumor cell growth. TFRC-mediated iron import is at the center of a novel feed-forward loop that facilitates colonic epithelial cell survival. This discovery may provide novel strategies for colorectal cancer therapy.