RESUMO
Hepatocellular carcinoma (HCC) is believed to arise from tumor-initiating cells (T-ICs), which are responsible for tumor relapse and metastases. Portal vein tumor thrombus (PVTT) is raised from HCC and strongly correlated to a poor prognosis. However, the mechanism underling the formation of PVTT is largely unknown. Herein, we provide evidence that RNA polymerase II subunit 5 (RPB5)-mediating protein (RMP) was progressively upregulated in PVTT and overexpressed RMP appeared to increase T-ICs self-renewal. Moreover, RMP promoted metastases of PVTT cells and HCC cells in vitro and in vivo. Knockdown of RMP attenuated T-ICs self-renewal and reversed epithelial-mesenchymal transition (EMT) in HCC and PVTT cells. The neutralizing assays suggested that interleukin-6 (IL-6) had an indispensable role in RMP regulating metastases and self-renewal of HCC cells. Furthermore, the transcription of IL-6 was verified to be modulated by RMP via interaction with p65 and RPB5, through which expanding the T-IC/cancer stem cell populations, as well as inducing EMT was promoted. These results suggested that RMP may promote PVTT formation by promoting IL-6 transcription. Thus, RMP serves as a potent factor contributed to develop PVTT and a promising therapeutic target for HCC patients.
Assuntos
Carcinoma Hepatocelular/metabolismo , Interleucina-6/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Neoplasias Hepáticas/metabolismo , Veia Porta/patologia , Proteínas Repressoras/metabolismo , Animais , Carcinoma Hepatocelular/patologia , Linhagem Celular Tumoral , Transição Epitelial-Mesenquimal , Técnicas de Silenciamento de Genes , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Neoplasias Hepáticas/patologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Metástase Neoplásica , Transplante de Neoplasias , Células-Tronco Neoplásicas/metabolismo , Veia Porta/metabolismo , Proteínas Repressoras/genéticaRESUMO
BACKGROUND: Asparagine synthetase (ASNS) is associated with drug resistance in leukaemia, and the function of this enzyme in the context of hepatocellular carcinoma (HCC) is not clear. In this study, the relationship between ASNS expression and clinical outcomes after surgical resection was investigated, and the therapeutic value of ASNS was also evaluated. METHODS: The expression of ASNS was evaluated in HCC samples by real-time PCR and immunohistochemistry assays. The correlation between ASNS expression and clinicopathological features was investigated. Potential clinicopathological prognostic factors were examined by univariate and multivariate survival analysis. Asparagine synthetase was overexpressed and knocked down in HCC cell lines to assess the influence of the enzyme on cell proliferation, migration and tumourigenicity. L-asparaginase was used to treat HCC cells with high or low levels of ASNS in vitro and in vivo to examine the therapeutic efficacy. RESULTS: The expression of ASNS was higher in HCC tumour tissues and was closely correlated with the serum AFP level, tumour size, microscopic vascular invasion, tumour encapsulation, TNM stage and BCLC stage. Patients with low ASNS expression levels had a poor prognosis with respect to overall survival (OS). The multivariate survival analysis indicated that ASNS is an independent prognostic factor for OS. Furthermore, functional studies demonstrated that ASNS significantly inhibits the proliferation, migration and tumourigenicity of HCC cells. The knockdown of ASNS markedly increased sensitivity to L-asparaginase, indicating that cells with different ASNS protein levels have different sensitivities to L-asparaginase. CONCLUSION: The expression of ASNS is an independent factor affecting the survival of HCC patients, and low ASNS expression in HCC was correlated with worse surgical outcomes. The ASNS may be a promising therapeutic target for the treatment of HCC.
