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BackgroundTripartite motif-containing protein 21 (TRIM21), an E3 ubiquitin ligase, has been implicated in autoimmune diseases. Dysregulation of TRIM21 contributes to the progression of human malignancies, but its role and clinical significance in breast cancer remain unclear.MethodsThe expression of TRIM21 was examined by quantitative real-time PCR, Western blot, and immunohistochemistry. The role of TRIM21 in the progression of breast cancer was determined using in vitro and in vivo models. The upstream regulation of TRIM21 was investigated by luciferase reporter assay.ResultsHere, we showed that TRIM21 expression in breast cancer tissues was decreased at both the mRNA and protein levels in comparison to that in nontumorous tissues. TRIM21 expression was closely associated with tumor size, estrogen receptor, human epidermal growth factor receptor 2, and clinical stage. Low TRIM21 expression was correlated with poor overall and disease-free survival in two independent cohorts containing 1,219 patients with breast cancer. A multivariate Cox regression model suggested TRIM21 as an independent factor for overall survival. In vitro data revealed that TRIM21 expression was suppressed by miR-494-3p directly targeting the 3′ untranslated region of TRIM21. Overexpression of TRIM21 impeded cell proliferation and tumor growth in breast cancer, whereas TRIM21 depletion enhanced these capacities.ConclusionCollectively, our findings indicate that TRIM21 serves as a potential prognostic biomarker and functions as a tumor suppressor in breast cancer.

Background: Circulating tumor cell (CTC)-based patient-derived cells are ideal models for investigating the molecular basis of cancer. However, the rarity and heterogeneity of CTCs as well as the difficulties of primary culture limit their practical application. Establishing efficient in vitro culture methods and functionally characterizing CTCs is essential for cancer studies. To this end, we developed an experimental protocol for the isolation, expansion, and identification of breast cancer CTCs.Methods: The CTC-3 cell line was established from peripheral blood cells of a breast cancer patient. A karyotype analysis was performed. The molecular profile was assessed by flow cytometry, quantitative real-time PCR, and western blot. The characteristics of tumors formed by CTC-3 cells were evaluated by cell growth and tumor sphere formation assays and in a mouse xenograft model. The tumors were analyzed by immunohistochemistry, immunofluorescence analysis, and hematoxylin and eosin staining.Results: The CTC-3 cell line showed more aggressive growth both in vitro and in vivo than the widely used MCF-7 breast cancer cell line. CTC-3 cells were also more resistant to chemotherapeutic agents, and gene profiling indicated higher expression levels of the epithelial-to-mesenchymal transition and stemness markers as compared to MCF-7 cells.Conclusions: CTC-3 cells are a better model for investigating the malignant behavior of breast cancer than existing cell lines.

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Anthracycline is a mainstay of treatment for breast cancer patients because of its antitumor activity. However, anthracycline resistance is a critical barrier in treating breast cancer. Thus, it is of great importance to uncover the molecular mechanisms underlying anthracycline resistance in breast cancer. Herein, we integrated transcriptome data, genetic alterations data, and clinical data of The Cancer Genome Atlas (TCGA) to identify the molecular mechanisms involved in anthracycline resistance in breast cancer. Two hundred and four upregulated genes and 1376 downregulated genes were characterized between the anthracycline-sensitive and anthracycline-resistant groups. It was found that drug resistance-associated genes such as ABCB5, CYP1A1, and CYP4Z1 were significantly upregulated in the anthracycline-resistant group. The gene set enrichment analysis (GSEA) suggested that the P53 signaling pathway, DNA replication, cysteine, and methionine metabolism pathways were associated with anthracycline sensitivity. Somatic TP53 mutation was a common genetic abnormality observed in the anthracycline-sensitive group, while CDH1 mutation was presented in the anthracycline-resistant group. Immune infiltration patterns were extremely different between the anthracycline-sensitive and anthracycline-resistant groups. Immune-associated chemokines and cytokines, immune regulators, and human leukocyte antigen genes were significantly upregulated in the anthracycline-sensitive group. These results reveal potential molecular mechanisms associated with anthracycline resistance.