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Subtype-specific clinical significance of RRM1 and RRM2 expression in non-small cell lung cancer: a TCGA-based analysis.

BACKGROUND: Non-small cell lung cancer (NSCLC), including lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), exhibits significant molecular heterogeneity. Ribonucleotide reductase (RNR), composed of RRM1 and RRM2, is essential for DNA synthesis and repair, but its subtype-specific clinical significance in NSCLC remains unclear. OBJECTIVE: To investigate the clinical and prognostic significance of RRM1 and RRM2 expression in NSCLC, with a focus on subtype-specific differences between LUAD and LUSC. METHODS: We analyzed RNA expression and clinical data from 980 NSCLC patients in The Cancer Genome Atlas (TCGA). Associations with clinicopathologic characteristics, overall survival, and oncogenic driver alterations were assessed. RESULTS: In LUAD, high RRM2 expression was significantly associated with advanced pathologic stage (p = 0.004), nodal involvement (p = 0.005), higher T stage (p = 0.030), and gender (p = 0.046). In LUSC, RRM2 was associated with age (p = 0.008), pathologic stage (p = 0.006), and N stage (p = 0.001). RRM1 showed no significant associations with stage-related parameters in either subtype. Correlation analyses revealed modest associations between RRM1 and multiple oncogenic drivers, whereas RRM2 showed stronger subtype-specific correlations, particularly with KRAS/BRAF in LUAD and CDKN2A/SOX2 in LUSC. Kaplan-Meier analysis demonstrated that high expression of both RRM1 and RRM2 was associated with poorer overall survival in LUAD, but not in LUSC. However, neither marker remained significant after adjustment for clinicopathological variables in multivariate analysis. CONCLUSION: RRM2 is associated with tumor progression in both NSCLC subtypes, while the prognostic associations of RRM1 and RRM2 are confined to LUAD. Although neither marker demonstrated independent prognostic significance in multivariate analysis, the findings support subtype-dependent roles of RNR components and highlight the potential biological and therapeutic relevance of nucleotide metabolism pathways in LUAD.

Carcinoma, Non-Small-Cell Lung

The M1 subunit of ribonucleotide reductase refines mapping of genetic rearrangements at chromosome 11p15.

We report the first use of the ribonucleotide reductase M1 subunit (RRM1) locus as a marker to assist in defining genetic rearrangements at 11p15. Our sample consisted of 21 Wilms' tumors from 18 patients, and one adrenal adenoma from a patient with Beckwith-Wiedemann syndrome, preexisting chromosome 11 maps being refined by the use of the RRM1 locus in all cases. Significantly, one Wilms' tumor showed loss of heterozygosity at the RRM1 locus only, whereas the adrenal adenoma showed a maintenance of heterozygosity at the RRM1 locus, loss having been previously demonstrated at the c-Ha-ras locus. The relevance of this finding to the location of one or more disease-associated loci at 11p15 is discussed.

Adenoma

3D epigenomic remodelling mediated by Foxa1 drives gemcitabine resistance in pancreatic cancer.

Gemcitabine remains a cornerstone treatment for pancreatic ductal adenocarcinoma (PDAC), yet the emergence of resistance constitutes a major clinical challenge with poorly understood epigenomic mechanisms. Here, we identified the pioneer transcription factor Foxa1 as a master regulator of gemcitabine resistance through multi-omics analysis. Mechanistically, Foxa1 drives widespread super-enhancer (SE) reprogramming and 3D genome remodelling in resistant cells, which coordinately activates the expression of key resistance genes, notably Rrm1 and Cdadc1. This is accompanied by increased chromatin accessibility, elevated H3K27ac enrichment at SEs, and enhanced Foxa1 binding at regulatory elements. Moreover, post-translational stabilization of Foxa1 via USP7-mediated deubiquitination sustains this epigenomic program. Genetic ablation of Foxa1 or specific SE regions near Rrm1 resensitizes resistant cells to gemcitabine. Building upon this mechanism, we demonstrate that bromodomain and extraterminal (BET) inhibitors, which disrupt SE function, potently reverse resistance. Notably, the clinical-stage BET inhibitor AZD5153, in combination with gemcitabine, achieves robust tumor suppression and overcomes resistance in cell-derived xenograft (CDX) models by dismantling the Foxa1-mediated resistant transcriptome and reinvigorating drug sensitivity. Our findings establish Foxa1-orchestrated enhancer reprogramming as a fundamental mechanism of gemcitabine resistance and unveil a promising epigenetic therapy to restore treatment efficacy in PDAC.

Hepatocyte Nuclear Factor 3-alpha

Quantitative determination that one of two potential RNA-binding domains of the A protein component of the U1 small nuclear ribonucleoprotein complex binds with high affinity to stem-loop II of U1 RNA.

Many RNA-associated proteins contain a ribonucleoprotein (RNP) consensus octamer encompassed by a conserved 80 amino acid sequence, which we have termed an RNA recognition motif (RRM). RRM family members contain either one (class I) or multiple (class II) copies of this motif. We report here that a class II component of the U1 small nuclear RNP (snRNP), the A protein of U1 snRNP (U1snRNP-A), contains two RRMs (RRM1 and -2), yet has only one binding domain (RRM1) that interacts specifically with stem-loop II of U1 RNA. Quantitative analysis of binding affinities of fragments of U1snRNP-A demonstrated that an 86-amino acid polypeptide was competent to bind to U1 RNA with an affinity comparable to that of the full-length protein (Kd approximately 80 nM). The carboxyl-terminal RRM2 of U1snRNP-A did not bind to U1 RNA and may recognize an unidentified heterologous RNA. We propose that class II proteins may function as bridges between RNA components of RNP complexes such as the spliceosome.

Binding Sites

Ribonucleotide Reductase Inhibition Triggers Ferroptosis in Genetically Defined Subsets of Non-Small Cell Lung Cancer.

UNLABELLED: Non-small cell lung cancer (NSCLC) is responsible for the majority of cancer-related mortality worldwide. Lung adenocarcinoma is the most common NSCLC subtype. Despite advances in targeted therapies, treatment resistance remains a critical challenge. Ribonucleotide reductase (RNR), a crucial enzyme in deoxyribonucleotide triphosphate biosynthesis, is frequently upregulated in cancer, contributing to genomic instability and poor prognosis in multiple malignancies. However, the role of the RNR complex in driving tumorigenesis is not fully understood in oncogene-driven lung adenocarcinoma. Transcriptomic analysis of more than 27,000 real-world samples of patients with NSCLC revealed that RNR subunits (RRM1 and RRM2) are significantly upregulated in TP53-mutated NSCLC and are correlated with significantly poor prognosis in multiple oncogene-driven lung adenocarcinoma. Using pharmacologic and genetic approaches to inhibit RNR in lung adenocarcinoma models, we assessed functional consequences through molecular, biochemical, and imaging techniques. RNR inhibition induced appreciable replication stress and triggered DNA damage, leading to cell death in lung adenocarcinoma cells. Notably, we uncovered that RNR suppression preferentially induced ferroptosis, an iron-dependent cell death driven by lipid peroxidation. This represents a previously unrecognized mechanism of RNR-mediated cell death by which mutant lung adenocarcinoma cells can be selectively targeted. Our study establishes RNR inhibition as a potent strategy to selectively induce ferroptosis in oncogene-addicted lung adenocarcinoma, offering a new therapeutic avenue for genetically defined patient subgroups. Targeting nucleotide metabolism could serve as an effective approach to overcome treatment resistance and improve clinical outcomes for patients with high-risk lung adenocarcinoma. SIGNIFICANCE: Our findings highlight RNR as a promising therapeutic target in oncogene-driven lung adenocarcinoma. By demonstrating that RNR inhibition induces ferroptosis, our study opens up new possibilities for developing targeted therapies that selectively eliminate cancer cells in lung adenocarcinoma, paving the way for personalized treatment strategies and potentially overcoming resistance to current therapies.

Humans