Publications

The transition from traditional animal-based approaches and assessments to New Approach Methodologies (NAMs) marks a scientific revolution in regulatory toxicology, with the potential of enhancing human and environmental protection. However, implementing the effective use of NAMs in regulatory toxicology has proven to be challenging, and so far, efforts to facilitate this change frequently focus on singular technical, psychological or economic inhibitors. This article takes a system-thinking approach to these challenges, a holistic framework for describing interactive relationships between the components of a system of interest. In this case, the regulatory toxicology system. We do so by analysing and interpreting a very large qualitative data set of experts’ observations, collected in a 3-day interactive workshop and three follow-up online workshops with a heterogeneous sample of experts representing major actors from the global regulatory toxicology system. We identified leverage points (where a small change within a system can have a disproportionately large effect) in the six core aspects—infrastructure, processes, culture, technology, goals, and actors—in the regulatory toxicology system to facilitate the effective use of NAMs. Identified systematic leverage points include the need for a functioning incentive structure for effectively discovering, developing, validating and using NAMs within academia, regulation, and industry; and measures that prevent or mitigate unwanted effects of using NAMs that acknowledge clashes between scientific, regulatory, political and social processes. The results serve as a basis for follow-up activities that reflect on the actual effectiveness of these levers and that develop measures for the regulatory toxicology system.

Acute myeloid leukaemia (AML) remains a challenging haematological malignancy, with most patients developing resistance to standard-of-care (SOC) treatments. This resistance is often attributed to the overexpression of anti-apoptotic BCL-2 family proteins, which regulate the intrinsic apoptotic pathway by inhibiting pro-apoptotic effector proteins such as BAX and BAK. AML cells exploit this imbalance to evade apoptosis and sustain survival, necessitating the development of novel therapeutic strategies. BH3 mimetics are small-molecule inhibitors targeting the pro-survival BCL-2 family proteins and have emerged as promising agents in patients with AML who are unable to receive high-intensity induction chemotherapy. Co-treatment with the BCL-2-specific inhibitor venetoclax and various SOC therapies has been proven effective, with several combinations now approved by the US Food and Drug Administration for adults with AML who are ≥75 years of age and/or are ineligible for intensive induction chemotherapy, on the basis of improved response rates and survival outcomes compared with the previous SOC. In this Review, we highlight the transformative potential of BH3 mimetics in AML therapy, including ongoing studies investigating novel combination regimens and efforts to further refine treatment strategies, with the ultimate goal of improving outcomes for patients with AML.

Background

Sorafenib, a ferroptosis agonist, is a first-line treatment for advanced hepatocellular carcinoma (HCC). However, its clinical efficacy is limited due to drug resistance, resulting in modest improvements in patient survival. Hence, the present study has been designed to identify critical molecular targets associated with sorafenib resistance and investigate the potential inhibitors in overcoming this therapeutic challenge.

Methods

In vivo whole-genome CRISPR/Cas9 library screens were conducted to identify resistance factors to ferroptosis agonists, such as RSL3 and sorafenib, in HCC. The effects and underlying molecular mechanisms of these resistance factors were investigated in HCC cells using ferroptosis detection assays, xenograft tumor models, chromatin immunoprecipitation (ChIP), and dual-luciferase reporter assays. Potential inhibitors targeting these factors were evaluated through computer-aided virtual screening, molecular dynamics simulations, surface plasmon resonance analysis, and functional evaluations.

Results

A retinoic acid metabolism gene cluster, including ADH4, ALDH1A1, ALDH1A3, FABP5, RBP1, and RDH10, was found demonstrating upregulation in HCC cells treated with ferroptosis agonist, sorafenib. This gene cluster contributes to the ferroptosis resistance by producing the strong reducing agent retinoic acid. The transcription factor POU3F3 was identified as a key regulator for the retinoic acid metabolism gene cluster, which simultaneously binds to their promoters, increasing their transcription and promoting retinoic acid production. Knockdown of POU3F3 significantly enhanced the pro-ferroptotic and inhibitory effects of sorafenib on HCC cells by suppressing retinoic acid metabolism. Furthermore, rosarin was identified as a POU3F3 inhibitor, with an equilibrium dissociation constant of 7.57 µM, and demonstrated a synergistic effect with sorafenib against HCC cells both in vitro and in vivo.

Conclusions

According to the results, POU3F3 acts as a protective regulator against sorafenib-induced ferroptosis in HCC cells by enhancing the transcription of multiple retinoic acid metabolism genes and promoting retinoic acid production. The POU3F3 inhibitor, rosarin, shows potential as an ideal candidate for overcoming sorafenib resistance in HCC.