Epitranscriptomic data indicate that aberrant tRNA modifications in malignant diseases can promote tumor growth by facilitating oncogene translation. NSUN2, a 5-methylcytosine (m5C) methyltransferase of tRNA, is elevated in an array of solid cancers, including triple-negative breast cancer (TNBC). However, it remains unclear how NSUN2 drives aggressive behavior and if NSUN2 could be an effective therapeutic target for TNBC. Functional experiments, including RNA interference, lentivirus transduction, and in vivo xenograft models, were conducted to evaluate the role of NSUN2 in TNBC cell proliferation, metastasis, and chemoresistance. Ribosome sequencing (Ribo-seq), tRNA m5C bisulfite sequencing, and codon usage bias analysis were employed to explore the translational mechanisms underlying NSUN2-mediated tRNA modifications. Glycolysis assays and molecular docking were used to investigate metabolic reprogramming and protein interactions. NSUN2 was significantly upregulated in TNBC and correlated with poor patient prognosis. Mechanistically, NSUN2 mediates m5C modification of tRNAVal−CAC, enhancing the codon-frequency-dependent translation of key glycolysis-related genes, including ALDH3A2, ALDH7A1, HK1, and PFKM. Depletion of NSUN2 disrupted tRNAVal−CAC m5C modification, impairing the translation of these metabolic enzymes and suppressing glycolysis, which ultimately inhibited TNBC cell proliferation, migration, and invasion both in vitro and in vivo. Furthermore, NSUN2 overexpression conferred resistance to docetaxel, while its inhibition sensitized TNBC cells to docetaxel treatment. Clinically, elevated expression levels of NSUN2 and glycolysis-related genes were observed in docetaxel-resistant TNBC tissues, further supporting the role of NSUN2 in chemoresistance. This study identifies NSUN2 as a critical regulator of TNBC progression through tRNAVal−CAC m5C modification and codon-biased translation of glycolysis-related mRNAs. Our findings reveal a novel NSUN2–tRNAVal−CAC axis that orchestrates metabolic reprogramming and translational control in TNBC, offering a promising prognostic biomarker and therapeutic target.

In the dynamic process of metastasis, circulating tumor cells (CTCs) emanate from the primary solid tumor and subsequently acquire the capacity to disengage from the basement membrane, facilitating their infiltration into the vascular system via the interstitial tissue. Given the pivotal role of CTCs in the intricate hematogenous metastasis, they have emerged as an essential resource for a deeper comprehension of cancer metastasis while also serving as a cornerstone for the development of new indicators for early cancer screening and new therapeutic targets. In the epoch of precision medicine, as CTC enrichment and separation technologies continually advance and reach full fruition, the domain of CTC research has transcended the mere straightforward detection and quantification. The rapid advancement of CTC analysis platforms has presented a compelling opportunity for in-depth exploration of CTCs within the bloodstream. Here, we provide an overview of the current status and research significance of multi-omics studies on CTCs, including genomics, transcriptomics, proteomics, and metabolomics. These studies have contributed to uncovering the unique heterogeneity of CTCs and identifying potential metastatic targets as well as specific recognition sites. We also review the impact of various states of CTCs in the bloodstream on their metastatic potential, such as clustered CTCs, interactions with other blood components, and the phenotypic states of CTCs after undergoing epithelial-mesenchymal transition (EMT). Within this context, we also discuss the therapeutic implications and potential of CTCs.

Background: Triple-negative breast cancer (TNBC) is characterized by aggressive behavior and limited treatment options, with chemotherapy resistance posing a significant clinical challenge. UBR5, an E3 ubiquitin ligase, has been consistently reported to be amplified and overexpressed in breast cancers. Materials and methods: This study analyzed 185 TNBC patients to investigate the association between UBR5 expression levels and clinical outcomes. Experimental approaches included in vitro assays using UBR5 knockout or knockdown TNBC cell models treated with doxorubicin and cisplatin, alongside in vivo xenograft models to assess therapeutic responses. Results: High UBR5 expression correlated significantly with poor 5-year disease-free survival (44.0% vs. 82.0% in low UBR5 group) and reduced pathological complete response rates to anthracycline-based neoadjuvant chemotherapy (8.8% vs. 33.3%). In vitro , UBR5 knockout or knockdown sensitized TNBC cells to doxorubicin and cisplatin, enhancing apoptosis and DNA damage accumulation, as evidenced by elevated γ-H2AX levels and impaired DNA damage repair (DDR) pathways, including ATM/CHK2 signaling and key repair proteins (53BP1, RAD51, BRCA1). Mechanistically, UBR5 loss suppressed p38/NF-κB signaling, further compromising DDR and exacerbating chemosensitivity. In vivo , UBR5-deficient xenografts exhibited enhanced doxorubicin responsiveness, an effect mimicked by p38 inhibition. Conclusions: UBR5 serves as a critical mediator of chemoresistance in TNBC by regulating the DNA damage response through the p38 signaling pathway. Targeting UBR5 or p38 signaling presents a promising therapeutic approach to overcome treatment resistance.

Background: Inflammatory breast cancer (IBC), of which HER2 + is the predominant subtype, is extremely aggressive and difficult to treat. Previous studies have suggested that targeting the tumour microenvironment (TME) may provide new directions for IBC diagnosis and treatment. Methods: In this study, we used single-cell transcriptome technology (scRNA-seq) to investigate the molecular features of the TME of HER2 + IBC patients and performed a comprehensive and detailed comparison of the cellular components and molecular phenotypes of the TME between IBC patients and noninflammatory breast cancer (nIBC) patients to elucidate the cell types that are specifically enriched in the TME of IBC patients, as well as the molecular features that are responsible for the preferential remodelling of the cellular functional state in the TME. Results: A total of 15,832 cells, including epithelial cells, endothelial cells, stromal cells, T cells, B cells, antibody secreting cells (ASCs) and myeloid cells, were obtained from tumour tissues from 3 HER2 + IBC patients for scRNA analysis. By comparing the TME with that of HER2 + nIBC patients in a public database, we found that the TME of HER2 + IBC patients had a greater level of lymphocyte infiltration than that of nIBC patients did, and an especially significant enrichment of ASCs (mainly plasmablasts or plasma cells). In the TME of HER2 + IBC patients, tumour-infiltrating T cells exhibited a dual molecular phenotype of high activation and high exhaustion, with tumour-infiltrating B cells preferring the extrafollicular developmental pathway, and tumour-infiltrating myeloid and mesenchymal cells exhibiting a greater immunosuppressive status. By performing a cellular interaction analysis, we revealed that PTN molecules were significantly overexpressed in HER2 + IBC tumour cells and that the cellular interactions mediated by these molecules were strongly correlated with the functional polarisation of the cellular components in the TME. We observed that HER2 + IBC tumour cells have an active interferon response and epithelial mesenchymal transition (EMT) signalling, and that their malignant process is strongly correlated with the inflammatory response. Moreover, we found that HER2 + IBC tumour-infiltrating B cells promoted necroptosis of endothelial cells through high expression of TNF, thus promoting inflammatory responses. Conclusion: We found a strong correlation between high expression of PTN molecules in HER2 + IBC tumour cells and their highly invasive characteristics and highly immunosuppressive TME. These results suggest that HER2 + IBC tumour cells can promote an inflammatory response by upregulating the expression of TNF molecules in B cells via PTN molecules and that the enhanced inflammatory response in turn promotes tumour progression, a malignant cycle that shapes a more immunosuppressive TME. Therefore, diagnostic and therapeutic strategies targeting the PTN-TNF molecular axis may have considerable potential for development in HER2 + IBC patients.

Background: Despite significant advancements in treatment, patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC) continue to face the challenge of drug resistance, highlighting the need to develop new drugs and treatment strategies. Pyrotinib has exhibited notable efficacy in managing HER2-positive MBC, especially in individuals with brain metastasis (BM). However, real-world evidence on the effectiveness of pyrotinib re-treatment remains limited. Objectives: This study aims to assess the efficacy of pyrotinib re-treatment—including treatment beyond progression (TBP) and rechallenge—in patients with HER2-positive MBC, particularly those with BMs, in a real-world clinical setting. Design: A retrospective, multicenter, real-world study. Methods: Patients with HER2-positive MBC who experienced progression during pyrotinib treatment and subsequently continued or resumed pyrotinib-based regimens were enrolled. Patients were divided into two groups according to the re-treatment pattern: the pyrotinib TBP group and the pyrotinib rechallenge group. The endpoints were progression-free survival (PFS) and overall survival (OS). Results: A total of 226 participants received pyrotinib TBP, whereas 33 received pyrotinib rechallenge. The median PFS of pyrotinib re-treatment (7.2 vs 6.3 months, p = 0.31) and the median OS, measured from the start of pyrotinib re-treatment (31.6 vs 21.0 months, p = 0.062), were comparable between the two groups. Among patients with BMs before pyrotinib re-treatment, the median PFS for pyrotinib re-treatment was 7.2 months, and the median OS was 25.2 months. Conclusion: Pyrotinib TBP and pyrotinib rechallenge both demonstrate potential benefits for patients with HER2-positive MBC, including those with BM.