ABSTRACT
AIM: Acquisition of anoikis resistance is the hallmark of cancer and has been shown to be involved in metastasis of melignant cells. Our previous work showed that anoikis resistance is associated with the metastasis of hepatocellular carcinoma (HCC) cells. The aim of this study is to elucidate the mechanisms of this course. MATERIALS & METHODS: Expression of BNIP3 and HIF-1α at the mRNA and protein level in HCC cells were detected by realtime PCR and western blot, respectively. Autophagy activation and signaling transduction pathway were detected by western blot. Cell viabilities were detected by CCK8 assay and trypan blue exclusion assay. RESULTS: Upregulation of BNIP3 promoted the activation of autophagy, one type of cell survival strategy in response to external stress, by suppressing mTOR/S6K1 signaling system. The upregulation of BNIP3 was mediated by ERK/HIF-1α pathway, which further contributed to anoikis resistance of HCC cells through the mTORC1 signaling pathway. CONCLUSION: Upregulation of BNIP3 contributs to anoikis resistance of HCC cells, and BNIP3 may serve as a novel therapeutic target for manipulation of cancer metastasis.
Subject(s)
Carcinoma, Hepatocellular/genetics , Carcinoma, Hepatocellular/metabolism , Extracellular Signal-Regulated MAP Kinases/metabolism , Hypoxia-Inducible Factor 1, alpha Subunit/metabolism , Liver Neoplasms/genetics , Liver Neoplasms/metabolism , Membrane Proteins/genetics , Proto-Oncogene Proteins/genetics , Signal Transduction , Anoikis/genetics , Autophagy/genetics , Carcinoma, Hepatocellular/pathology , Cell Line, Tumor , Gene Expression Regulation, Neoplastic , Humans , Liver Neoplasms/pathology , Mechanistic Target of Rapamycin Complex 1 , Membrane Proteins/metabolism , Models, Biological , Multiprotein Complexes/metabolism , Neoplasm Metastasis , Proto-Oncogene Proteins/metabolism , TOR Serine-Threonine Kinases/metabolismABSTRACT
Extracellular adenosine triphosphate (eATP) transduces purinergic signal and plays an important regulatory role in many biological processes, including tumor cell growth and cell death. A large amount of eATP exists in the fast-growing tumor center and inflammatory tumor microenvironment. Tumor cells could acquire anoikis resistance and anchorage independence in tumor microenvironment and further cause metastatic lesion. Whether such a high amount of eATP has any effect on the anchored and non-anchored tumor cells in tumor microenvironment has not been elucidated and is investigated in this study. Our data showed that autophagy helped hepatoma cells to maintain survival under the treatment of no more than 1 mM of eATP. Only when eATP concentration reached a relatively high level (2.5 mM), cell organelle could not be further maintained by autophagy, and apoptosis and cell death occurred. In hepatoma cells under treatment of 2.5 mM of eATP, an AMP-activated protein kinase (AMPK) pathway was dramatically activated while mTOR signaling pathway was suppressed in coordination with apoptosis. Further investigation showed that the AMPK/mTOR axis played a key role in tipping the balance between autophagy-mediated cell survival and apoptosis-induced cell death under the treatment of eATP. This work provides evidence to explain how hepatoma cells escape from eATP-induced cytotoxicity as well as offers an important clue to consider effective manipulation of cancer.
