Hepatic nuclear factor 4 alpha promotes the ferroptosis of lung adenocarcinoma via transcriptional activation of cytochrome P450 oxidoreductase.

Background: Lung adenocarcinoma is one of the most prevalent cancers while ferroptosis is crucial for cancer therapies. This study aims to investigate the function and mechanism of hepatic nuclear factor 4 alpha (HNF4A) in lung adenocarcinomas' ferroptosis. Materials and Methods: HNF4A expression in ferroptotic A549 cells was detected. Then HNF4A was knocked down in A549 cells while overexpressed in H23 cells. Cells with changed HNF4A expression were tested for cytotoxicity and the level of cellular lipid peroxidation. The expression of cytochrome P450 oxidoreductase (POR) expression was examined after HNF4A was knocked down or overexpressed. Chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR) and dual-luciferase assays were performed to validate the regulation of HNF4A on POR. Finally, POR was restored in HNF4A-altered cells to check whether it restores the effect of HNF4A on ferroptosis. Results: We found that HNF4A expression significantly decreased in the ferroptosis of A549 cells, and this change can be blocked by deferoxamine, an inhibitor of ferroptosis. Knockdown of HNF4A inhibited ferroptosis in A549 cells while overexpression of HNF4A promoted ferroptosis in H23 cells. We identified a key ferroptosis-related gene, POR serves as a potential target gene of HNF4A, whose expression was significantly changed in lung adenocarcinoma cells knocking down or overexpressing HNF4A. We demonstrated that HNF4A was bound to the POR's promoter to enhance POR expression, and identified the binding sites via ChIP-qPCR and luciferase assays. Restoration of POR expression blocked the promoting effect of HNF4A on ferroptosis in lung adenocarcinoma. Conclusion: HNF4A promotes POR expression through binding to the POR's promoter, and subsequently promotes the ferroptosis of lung adenocarcinoma.

Retinol Saturase Mediates Retinoid Metabolism to Impair a Ferroptosis Defense System in Cancer Cells.

Ferroptosis is an iron-dependent form of regulated cell death induced by the lethal overload of lipid peroxides in cellular membranes. In recent years, modulating ferroptosis has gained attention as a potential therapeutic approach for tumor suppression. In the current study, retinol saturase (RETSAT) was identified as a significant ferroptosis mediator using a publicly accessible CRISPR/Cas9 screening dataset. RETSAT depletion protected tumor cells from lipid peroxidation and subsequent cell death triggered by various ferroptosis inducers. Furthermore, exogenous supplementation with retinoids, including retinol (the substrate of RETSAT) and its derivatives retinal and retinoic acid, also suppressed ferroptosis, whereas the product of RETSAT, 13, 14-dihydroretinol, failed to do so. As effective radical-trapping antioxidant, retinoids protected the lipid membrane from autoxidation and subsequent fragmentation, thus terminating the cascade of ferroptosis. Pseudotargeted lipidomic analysis identified an association between retinoid regulation of ferroptosis and lipid metabolism. Retinoic acid, but not 13, 14-dihydroretinoic acid, interacted with its nuclear receptor and activated transcription of stearoyl-CoA desaturase, which introduces the first double bond into saturated fatty acid and thus catalyzes the generation of monounsaturated fatty acid, a known ferroptosis suppressor. Therefore, RETSAT promotes ferroptosis by transforming retinol to 13, 14-dihydroretinol, thereby turning a strong anti-ferroptosis regulator into a relatively weak one. SIGNIFICANCE: Retinoids have ferroptosis-protective properties and can be metabolized by RETSAT to promote ferroptosis, suggesting the possibility of targeting retinoid metabolism in cancer as a treatment strategy to trigger ferroptosis.

The immunomodulatory role of all-trans retinoic acid in tumor microenvironment.

Retinoids are essential nutrients for human beings. Among them, all-trans retinoic acid (ATRA), considered one of the most active metabolites, plays important roles in multiple biological processes. ATRA regulates the transcription of target genes by interacting with nuclear receptors bonded to retinoic acid response elements (RAREs). Besides its differentiation-inducing effect in the treatment of acute promyelocytic leukemia and some solid tumor types, its immunoregulatory role in tumor microenvironment (TME) has attracted considerable attention. ATRA not only substantially abrogates the immunosuppressive effect of tumor-infiltrating myeloid-derived suppressor cells but also activates the anti-tumor effect of CD8 + T cells. Notably, the combination of ATRA with other therapeutic approaches, including immune checkpoint inhibitors (ICIs), tumor vaccines, and chemotherapy, has been extensively investigated in a variety of tumor models and clinical trials. In this review, we summarize the current understanding of the role of ATRA in cancer immunology and immunotherapy, dissect the underlying mechanisms of ATRA-mediated activation or differentiation of different types of immune cells, and explore the potential clinical significance of ATRA-based cancer therapy.

miR-6077 promotes cisplatin/pemetrexed resistance in lung adenocarcinoma via CDKN1A/cell cycle arrest and KEAP1/ferroptosis pathways.

Lung adenocarcinoma (LUAD) is one of the most common malignancies worldwide. Combination chemotherapy with cisplatin (CDDP) plus pemetrexed (PEM) remains the predominant therapeutic regimen; however, chemoresistance greatly limits its curative potential. Here, through CRISPR-Cas9 screening, we identified miR-6077 as a key driver of CDDP/PEM resistance in LUAD. Functional experiments verified that ectopic overexpression of miR-6077 desensitized LUAD cells to CDDP/PEM in both cell lines and patient-derived xenograft models. Through RNA sequencing in cells and single-cell sequencing of samples from patients with CDDP/PEM treatments, we observed CDDP/PEM-induced upregulation of CDKN1A and KEAP1, which in turn activated cell-cycle arrest and ferroptosis, respectively, thus leading to cell death. Through miRNA pull-down, we identified and validated that miR-6077 targets CDKN1A and KEAP1. Furthermore, we demonstrated that miR-6077 protects LUAD cells from cell death induced by CDDP/PEM via CDKN1A-CDK1-mediated cell-cycle arrest and KEAP1-NRF2-SLC7A11/NQO1-mediated ferroptosis, thus resulting in chemoresistance in multiple LUAD cells both in vitro and in vivo. Moreover, we found that GMDS-AS1 and LINC01128 sensitized LUAD cells to CDDP/PEM by sponging miR-6077. Collectively, these results imply the critical role of miR-6077 in LUAD's sensitivity to CDDP/PEM, thus providing a novel therapeutic strategy for overcoming chemoresistance in clinical practice.

Clinicopathological and prognostic implications of ALK rearrangement in patients with completely surgically resected lung adenocarcinoma.

BACKGROUND: The prognostic significance of ALK rearrangement is still contradictory. Here, we aimed to investigate the clinical characteristics and outcomes of lung adenocarcinoma patients with ALK rearrangement, and analyze whether these patients benefited from targeted therapy. METHODS: This was a retrospective cohort study of 80 ALK-rearranged lung adenocarcinoma patients who had undergone radical surgery and another 3031 ALK mutation-negative patients were retrospectively reviewed for inclusion in this case-controlled analyses. Overall survival (OS) was evaluated using the Kaplan--Meier method. Univariate analysis (UVA) and multivariate analysis (MVA) by the Cox proportional hazards regression identified risk factors that predicted OS. RESULTS: Compared to ALK-negative patients, the ALK rearranged patients were younger, with more non-smokers, more females, a larger primary tumor was demonstrated, and were a higher pathological stage. In particular, the risk of lymph node metastasis was higher. For patients with surgically-resected tumors, the prognosis was better for ALK rearranged patients (HR = 0.503; 95% CI: 0.259-0.974, p = 0.041). In addition, for stage II-III patients, targeted therapy was an independent prognostic factor of better OS (HR = 0.159; 95% CI: 0.032-0.801, p = 0.026). CONCLUSIONS: ALK rearranged lung adenocarcinoma patients who have undergone radical surgery have distinct clinical features. Patients with ALK rearrangement may have a favorable prognosis, and stage II-III patients may benefit from targeted treatment.