RESUMO
RBBP6 has been implicated in tumorigenesis but its role in tumor metastasis and progression has not been evaluated. Interestingly, here we show that RBBP6 is upregulated in colorectal cancer (CRC) where its expression level is positively correlated with distant metastasis. In this study, we identified RBBP6, a RING Finger-domain E3 ubiquitin ligase, served as an independent prognostic factor and predicted poor outcome for CRC patients. RBBP6 promoted cell proliferation, migration, and invasion in CRC cells and promoted tumor growth, lung metastasis, and liver metastasis in mouse models. Mechanistically, we revealed that RBBP6 bound and ubiquitylated IκBα, an inhibitor of the NF-κB-signaling pathway. RBBP6-mediated ubiquitination and degradation of IκBα significantly enhanced p65 nuclear translocation, which triggered the activation of NF-κB pathway and then induced the epithelial-mesenchymal transition (EMT) process and cell metastasis. Furthermore, by DNA methylation results and ChIP analysis, we demonstrated that the promoter of RBBP6 was hypomethylated, and was activated by multi-oncogenic transcription factors. In conclusion, our findings suggest that RBBP6 may be a potential prognostic biomarker and therapeutic target for CRC invasion and metastasis.
Assuntos
Neoplasias Colorretais/enzimologia , Proteínas de Ligação a DNA/metabolismo , Transição Epitelial-Mesenquimal , Proteínas de Neoplasias/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Animais , Células CACO-2 , Neoplasias Colorretais/genética , Neoplasias Colorretais/patologia , Proteínas de Ligação a DNA/genética , Células HT29 , Humanos , Masculino , Camundongos , Camundongos Nus , Metástase Neoplásica , Proteínas de Neoplasias/genética , Ubiquitina-Proteína Ligases/genéticaRESUMO
Radiotherapy (RT) can be used as preoperative treatment to downstage initially unresectable locally rectal carcinoma, but radioresistance and recurrence remain significant problems. Retinoblastoma binding protein 6 (RBBP6) has been implicated in the regulation of cell cycle, apoptosis and chemoresistance both in vitro and in vivo. The present study investigated whether the inhibition of RBBP6 expression would improve radiosensitivity in human colorectal cancer cells. After SW620 and HT29 cells were exposed to radiation, the levels of RBBP6 mRNA and protein increased over time in both cells. Moreover, a significant reduction in clonogenic survival and a decrease in cell viability in parallel with an obvious increase in cell apoptosis were demonstrated in irradiated RBBP6-knockdown cells. Transfection with RBBP6 shRNA improved the levels of G2-M phase arrest, which blocked the cells in a more radiosensitive period of the cell cycle. These observations indicated that cell cycle and apoptosis mechanisms may be connected with tumor cell survival following radiotherapy. In vivo, the tumor growth rate of nude mice in the RBBP6-knockdown group was significantly slower than that in other groups. These results indicated that RBBP6 overexpression could resist colorectal cancer cells against radiation by regulating cell cycle and apoptosis pathways, and inhibition of RBBP6 could enhance radiosensitivity of human colorectal cancer.
Assuntos
Proteínas de Transporte/genética , Neoplasias Colorretais/genética , Neoplasias Colorretais/radioterapia , Proteínas de Ligação a DNA/genética , Tolerância a Radiação/genética , Animais , Apoptose/genética , Contagem de Células/métodos , Pontos de Checagem do Ciclo Celular/genética , Sobrevivência Celular/genética , Pontos de Checagem da Fase G2 do Ciclo Celular/genética , Células HT29 , Humanos , Masculino , Camundongos , Camundongos Nus , Recidiva Local de Neoplasia/genética , RNA Mensageiro/genética , Transfecção/métodos , Ubiquitina-Proteína LigasesRESUMO
AIM: To detect the expression of Fas ligand (FasL) in colon cancer tissues and cell lines and analyze the function of FasL-expressing colon cancer cells in inducing Fas-sensitive T lymphocyte apoptosis. METHODS: Ninety surgically resected colon cancer tissues and 15 hepatic metastasis specimens were investigated by immunohistochemical method with normal colon mucosa and colon adenoma as control. The relationship between FasL expression and pathologic features was also analyzed. FasL expression of 4 colon cancer cell lines, SW620, Lovo, LS-174T and SW1116, were detected by Western blotting assay. The function of FasL expressed on colon cancer cells was determined by coculture assay with Jurkat T lymphocytes, the apoptotic rate of which was detected by flow cytometry assay. RESULTS: Fifty-six (62.22%) cases of all the 90 colon cancer tissues and all (100%) the liver metastasis specimens expressed FasL, significantly higher than normal colon mucosa and colonic adenoma. Higher expression of FasL was found in more advanced stage of colon cancer and in cancer tissues with lymphatic or hepatic metastasis. All the colon cancer cell lines were found to express FasL. After coculture with the SW1116 cells for 24 h with an effector: target ratio 10:1, the rate of apoptosis of Jurkat cells rose from 1.9% to 21.0%. CONCLUSION: The expression of FasL is upregulated in colon cancer and the functionally expressed FasL can induce apoptosis of Fas-expressing T lymphocytes.
