Quilamine HQ1-44, an iron chelator vectorized toward tumor cells by the polyamine transport system, inhibits HCT116 tumor growth without adverse effect

Iron metabolism in colorectal cancer: a balancing act

BACKGROUND

Colorectal cancer (CRC) is the third most commonly diagnosed cancer and the second deadliest malignancy worldwide. Current dietary habits are associated with increased levels of iron and heme, both of which increase the risk of developing CRC. The harmful effects of iron overload are related to the induction of iron-mediated pro-tumorigenic pathways, including carcinogenesis and hyperproliferation. On the other hand, iron deficiency may also promote CRC development and progression by contributing to genome instability, therapy resistance, and diminished immune responses. In addition to the relevance of systemic iron levels, iron-regulatory mechanisms in the tumor microenvironment are also believed to play a significant role in CRC and to influence disease outcome. Furthermore, CRC cells are more prone to escape iron-dependent cell death (ferroptosis) than non-malignant cells due to the constitutive activation of antioxidant genes expression. There is wide evidence that inhibition of ferroptosis may contribute to the resistance of CRC to established chemotherapeutic regimens. As such, ferroptosis inducers represent promising therapeutic drugs for CRC.

CONCLUSIONS AND PERSPECTIVES

This review addresses the complex role of iron in CRC, particularly in what concerns the consequences of iron excess or deprivation in tumor development and progression. We also dissect the regulation of cellular iron metabolism in the CRC microenvironment and emphasize the role of hypoxia and of oxidative stress (e.g. ferroptosis) in CRC. Finally, we underline some iron-related players as potential therapeutic targets against CRC malignancy.

An iron-deficient diet prevents alcohol- or diethylnitrosamine-induced acute hepatotoxicity in mice by inhibiting ferroptosis

The liver is easily injured by exogenous chemicals through reactive oxygen species (ROS), which lead to ferroptosis, a ROS-dependent programmed cell death characterized by iron accumulation and lipid peroxidation. However, whether iron restriction has a positive role in chemicals-induced liver injuries is unknown. The present study investigated the effects of an iron-deficient diet on liver injuries induced by alcohol or diethylnitrosamine (DEN). Mice were fed an iron-deficient diet for four weeks, then treated with three doses of alcohol (5 g/kg, 24 h interval, gavage) to mimic mild liver injury or five doses of DEN (50 mg/kg, 24 h interval, i. p.) to mimic severe liver failure. The results showed that mice were iron-deficient after four weeks of feeding. Interestingly, as evaluated by H&E staining of liver slices, liver/body weight ratio, serum ALT and AST, iron deficiency significantly alleviated liver injuries triggered by alcohol or DEN. The activities of alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH), and the expression of CYP2E1 were increased by iron deficiency. Mechanistically, iron deficiency prevented the decrease of glutathione peroxidase 4 (GPX4), which eliminated malondialdehyde (MDA) by utilizing glutathione (GSH). In summary, alcohol- or DEN-induced liver injuries were mitigated by the iron-deficient diet by inhibiting ferroptosis, which might be a promising measure for preventing liver injuries induced by alcohol, DEN, or other exogenous chemicals.

Recent advances in cancer treatment by iron chelators

The development of new therapeutic alternatives for cancers is a major public health priority. Among the more promising approaches, the iron depletion strategy based on metal chelation in the tumoral environment has been particularly studied in recent decades. After a short description of the importance of iron for cancer cell proliferation, we will review the different iron chelators developed as potential chemotherapeutics. Finally, the recent efforts to vectorize the chelating agents specifically in the microtumoral environment will be discussed in detail.