ABSTRACT
Metastasis is the leading cause of cancer-related death, where TGFß-induced epithelial-mesenchymal transition (EMT) process confers on cancer cells increased metastatic potential. However, the involvement of circRNAs in this process is still obscure. Here, we identify a TGFß-induced circRNA called circITGB6 as an indispensable factor during the TGFß-mediated EMT process. circITGB6 is significantly upregulated in metastatic cancer samples and its higher abundance is closely correlated to worse prognosis of colorectal cancer (CRC) patients. Through gain- and loss-of-function assays, circITGB6 is found to potently promote EMT process and tumor metastasis in various models in vitro and in vivo. Mechanistically, circITGB6 enhances the mRNA stability of PDPN, an EMT-promoting gene, by directly interacting with IGF2BP3. Notably, interfering circITGB6 with PEI-coated specific siRNA effectively represses liver metastasis. Therefore, our study reveals the function of a TGFß-regulated circRNA in tumor metastasis and suggests that targeting circITGB6 is a promising strategy for cancer therapy.
Subject(s)
Colorectal Neoplasms , RNA, Circular , Humans , RNA, Circular/genetics , Transforming Growth Factor beta/metabolism , Epithelial-Mesenchymal Transition/genetics , Cell Line, Tumor , Colorectal Neoplasms/genetics , Colorectal Neoplasms/pathology , Cell Movement , Gene Expression Regulation, Neoplastic , Neoplasm Metastasis , Membrane Glycoproteins/geneticsABSTRACT
Distant metastasis is a major contributor to cancer-related mortality. However, the role of circRNAs in this process remains unclear. Herein, we profiled the circRNA expression in a cohort of 68 colorectal carcinoma (CRC) primary tumors and their paired liver metastatic lesions. By overlapping with the TGFß-responsive circRNAs, circNEIL3 (hsa_circ_0001460) was identified as a TGFß-repressive and metastasis-related circRNA. Functionally, circNEIL3 effectively inhibited tumor metastasis in both and in vivo and in vivo models of various cancer types. Mechanistically, circNEIL3 exerts its metastasis-repressive function through its direct interaction with oncogenic protein, Y-box-binding protein 1 (YBX1), which consequently promotes the Nedd4L-mediated proteasomal degradation of YBX1. Importantly, circNEIL3 expression was negatively correlated to YBX1 protein level and metastatic tendency in CRC patient samples. Collectively, our findings indicate the YBX1-dependent antimetastatic function of circNEIL3 and highlight the potential of circNEIL3 as a biomarker and therapeutic option in cancer treatment.
Subject(s)
Colorectal Neoplasms , Ubiquitin-Protein Ligases , Humans , Ubiquitin-Protein Ligases/genetics , RNA, Circular/genetics , RNA, Circular/metabolism , Colorectal Neoplasms/genetics , Colorectal Neoplasms/metabolism , Y-Box-Binding Protein 1/genetics , Y-Box-Binding Protein 1/metabolismABSTRACT
The tumor-infiltrating Tregs are linked to colorectal cancer progression and outcome. FOXP3 is regarded as a critical developmental and functional factor for Tregs. FOXP3-TSDR demethylation is required for stable expression of FOXP3 and maintenance of Treg function. In our study, we found specific DNA hypomethylation of FOXP3-TSDR in CD4+ T cells from colon tumor tissues as compared with normal colonic tissues. Moreover, we also found that the expression of STAT5 and TET2 was increased in CD4+ T cells from colon tumor tissues, and the superfluous STAT5 and TET2 binding to FOXP3-TSDR resulted in DNA hypomethylation. In conclusion, we have demonstrated that excessive amounts of STAT5 may bind more TET2 to the FOXP3-TSDR and upregulate FOXP3 expression via DNA demethylation. Our study improved the mechanism of FOXP3-TSDR hypomethylation in tumor-infiltrating CD4+ T cells of CRC patients.
Subject(s)
CD4-Positive T-Lymphocytes/metabolism , Colorectal Neoplasms/genetics , Colorectal Neoplasms/metabolism , DNA Methylation , DNA-Binding Proteins/metabolism , Forkhead Transcription Factors/genetics , Proto-Oncogene Proteins/metabolism , STAT5 Transcription Factor/metabolism , Aged , Demethylation , Dioxygenases , Female , Forkhead Transcription Factors/metabolism , Humans , Lymphocytes, Tumor-Infiltrating/metabolism , Male , Middle AgedABSTRACT
When purified from a tumor, certain heat shock protein 70 (HSP70)-peptide complexes (PCs) can function as effective vaccines against the tumor from which the complexes were isolated. The immunogenic mechanisms of HSP70 preparations imply that tumor-derived HSP70-PCs exhibit antigens associated with antigen-presenting cells such as dendritic cells (DCs), inducing antigen-specific cytotoxic CD8+ T cells. However, some important membrane-resident tumor-associated peptides, such as the HER-2/neu (c-erbB2) oncogenic protein, cannot be purified from HSP70 by traditional methods. In the present study, a new approach for the purification of HSP70-PCs from HER-2-overexpressing breast cancer cells was established. The detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) was used to obtain more effectual tumor peptides. The new purified product was named HSP70-HER-2-PC, and its immunological activities were determined. Traditionally purified HSP70-PCs (without CHAPS) and recombinant human HSP70-HER-2 protein complexes (recombined in vitro) were used as controls. These three HSP70-associated tumor antigenic complex pulsed dendritic cells (DCs) were used to stimulate an antitumor response. The mature DCs pulsed with HSP70-HER-2-PCs stimulated autologous T cells to secrete higher levels of type I cytokine compared to the two control groups. Moreover, DCs pulsed with HSP70-HER-2-PCs induced the most specific CD8+ T cells that specifically killed the same tumor cells. These findings provide a basis for new approaches in enhancing HSP70-based immunotherapy for HER-2-associated or other membrane antigenic peptide-related cancers.