Low expression of PCK2 in breast tumors contributes to better prognosis via inducing senescence of cancer cells

PCK2 promotes invasion and epithelial-to-mesenchymal transition in triple-negative breast cancer by promoting TGF-β/SMAD3 signaling through inhibiting TRIM67-mediated SMAD3 ubiquitination

PCK2, which encodes mitochondrial phosphoenolpyruvate carboxykinase (PEPCK-M), is upregulated in various cancers. We demonstrated high expression of PEPCK-M in approximately half of triple-negative breast cancers (TNBCs) previously. TNBC is associated with an aggressive phenotype and a high metastasis rate. In this study, we investigated the role of PCK2 in TNBC. PCK2 knockdown suppressed proliferation and mTOR signaling in TNBC cells. In addition, cell invasion/migration ability and the expression of epithelial-to-mesenchymal transition (EMT) markers were positively correlated with PCK2 expression in TNBC cells via regulation of transforming growth factor-β (TGF-β)/SMAD3 signaling. SMAD3 was positively regulated by PCK2 in TNBC cells. Knockdown of SMAD3 in PCK2-overexpressing TNBC cells reduced the expression levels of EMT markers, Snail and Slug, and suppressed cell invasion/migration. In addition, PCK2 knockdown attenuated the stimulatory effect of TGF-β on SMAD3 phosphorylation in TNBC cells. PEPCK-M promotes the protein and mRNA expression of SMAD3 via competitive binding to tripartite motif-containing 67 (TRIM67), an E3 ubiquitin ligase, to reduce SMAD3 ubiquitination, which leads to promoting nuclear translocation of SMAD3 and autoregulation of SMAD3 transcription. Moreover, high PCK2 mRNA expression was significantly associated with poor survival in TNBC patients. In conclusion, our study revealed for the first time that PCK2 activates TGF-β/SMAD3 signaling by regulating the expression and phosphorylation of SMAD3 by inhibiting TRIM67-mediated SMAD3 ubiquitination and promoting the stimulatory effect of TGF-β to promote TNBC invasion. The regulatory effect of PCK2 on mTOR and TGF-β/SMAD3 signaling suggests that PCK2 is a potential therapeutic target for suppressing TNBC progression.

XRCC1 is linked to poor prognosis in adenocarcinoma of the esophagogastric junction after radiotherapy: transcriptome and alternative splicing events analysis

PURPOSE

This study aimed to (i) investigate the relationship between X-ray repair cross-complementing protein 1 gene (XRCC1) and prognosis in patients with adenocarcinoma of the esophagogastric junction (AEG), and (ii) analyze the roles of XRCC1 in human gastric adenocarcinoma (AGS) cells following X-ray radiation.

METHODS

A total of 46 AEG patients were enrolled and examined for XRCC1 protein by immunohistochemistry. XRCC1 was knocked down in AGS cells by transfection, and AGS cells were subsequently exposed to 6 Gy of X-ray radiation. XRCC1 mRNA and protein expression was examined via quantitative real-time PCR (qRT-PCR) and Western blot analysis. The apoptosis of AGS cells was examined by flow cytometer. RNA-sequencing technology was used to identified differentially expressed genes and alternative splicing events following XRCC1 knockdown and radiation exposure.

RESULTS

XRCC1 positivity was strongly associated with distant metastasis, pathological tumor-node-metastasis (pTNM) classification, and radiotherapy resistance in AEG patients. A significant difference in progression-free survival was observed between AEG patients with low and high XRCC1 protein expression. The knockdown of XRCC1 notably exacerbated the effects of X-ray radiation on apoptosis in AGS cells. Additionally, X-ray radiation modified the expression of genes related to apoptosis and immune response in XRCC1-knockdown AGS cells. Furthermore, the generation of splice variants was influenced by XRCC1 knockdown in AGS cells.

CONCLUSION

XRCC1 may serve as a key oncogene that elucidates the role of alternative splicing events in the progression of AEG following X-ray treatment.

Two-Dimensional-PAGE Coupled with nLC-MS/MS-Based Identification of Differentially Expressed Proteins and Tumorigenic Pathways in MCF7 Breast Cancer Cells Transfected for JTB Protein Silencing

The identification of new cancer-associated genes/proteins, the characterization of their expression variation, the interactomics-based assessment of differentially expressed genes/proteins (DEGs/DEPs), and understanding the tumorigenic pathways and biological processes involved in BC genesis and progression are necessary and possible by the rapid and recent advances in bioinformatics and molecular profiling strategies. Taking into account the opinion of other authors, as well as based on our own team's in vitro studies, we suggest that the human jumping translocation breakpoint (hJTB) protein might be considered as a tumor biomarker for BC and should be studied as a target for BC therapy. In this study, we identify DEPs, carcinogenic pathways, and biological processes associated with JTB silencing, using 2D-PAGE coupled with nano-liquid chromatography tandem mass spectrometry (nLC-MS/MS) proteomics applied to a MCF7 breast cancer cell line, for complementing and completing our previous results based on SDS-PAGE, as well as in-solution proteomics of MCF7 cells transfected for JTB downregulation. The functions of significant DEPs are analyzed using GSEA and KEGG analyses. Almost all DEPs exert pro-tumorigenic effects in the JTBlow condition, sustaining the tumor suppressive function of JTB. Thus, the identified DEPs are involved in several signaling and metabolic pathways that play pro-tumorigenic roles: EMT, ERK/MAPK, PI3K/AKT, Wnt/β-catenin, mTOR, C-MYC, NF-κB, IFN-γ and IFN-α responses, UPR, and glycolysis/gluconeogenesis. These pathways sustain cancer cell growth, adhesion, survival, proliferation, invasion, metastasis, resistance to apoptosis, tight junctions and cytoskeleton reorganization, the maintenance of stemness, metabolic reprogramming, survival in a hostile environment, and sustain a poor clinical outcome. In conclusion, JTB silencing might increase the neoplastic phenotype and behavior of the MCF7 BC cell line. The data is available via ProteomeXchange with the identifier PXD046265.

Senescence-related gene c-Myc affects bladder cancer cell senescence by interacting with HSP90B1 to regulate cisplatin sensitivity

Patients with advanced bladder cancer gradually become less sensitive to chemotherapeutic agents, leading to tumor recurrence. Initiating the senescence program in solid tumors may be an important means of improving short-term drug sensitivity. The important role of c-Myc in bladder cancer cell senescence was determined using bioinformatics methods. The response to cisplatin chemotherapy in bladder cancer sample was analyzed according to the Genomics of Drug Sensitivity in Cancer database. Cell Counting Kit-8 assay, clone formation assay, and senescence-associated β-galactosidase staining were used to assess bladder cancer cell growth, senescence, and sensitivity to cisplatin, respectively. Western blot and immunoprecipitation were performed to understand the regulation of p21 by c-Myc/HSP90B1. Bioinformatic analysis showed that c-Myc, a cellular senescence gene, was significantly associated with bladder cancer prognosis and sensitivity to cisplatin chemotherapy. c-Myc and HSP90B1 expression were highly correlated in bladder cancer. Reducing the level of c-Myc significantly inhibited bladder cancer cell proliferation, promoted cellular senescence, and enhanced cisplatin chemosensitivity. Immunoprecipitation assays confirmed that HSP90B1 interacted with c-Myc. Western blot analysis showed that reducing the level of HSP90B1 could redeem the p21 overexpression caused by c-Myc overexpression. Further studies showed that reducing HSP90B1 expression could alleviate the rapid growth and accelerate cellular senescence of bladder cancer cells caused by c-Myc overexpression, and that reducing HSP90B1 levels could also improve cisplatin sensitivity in bladder cancer cells. HSP90B1/c-Myc interaction regulates the p21 signaling pathway, which affects cisplatin chemosensitivity by modulating bladder cancer cell senescence.