Abstract
BackgroundAutophagy is an important adaptive survival mechanism, which has been postulated to be involved in cancer metastasis. The purpose of this study was to investigate autophagy in metastasis of hepatocellular carcinoma (HCC).MethodsImmunohistochemical analysis of autophagic activity in metastatic and paired primary HCC tissues using LC3 as autophagosome marker was performed in samples from 216 HCC patients diagnosed with metastasis (including 158 intravascular, 42 intrabiliary, 8 lymph node, 4 bone and 4 lung metastases). Then a mouse model of pulmonary metastasis was established using a highly metastatic HCC cell line (HCCLM3). Autophagy in pulmonary metastases and paired primary tumors were analyzed by LC3 immunohistochemistry, transmission electron microscopy (TEM) and western blot analysis. Further, mouse model of pulmonary metastasis and in vitro cell migration, invasion and detachment models were established using a stable GFP-LC3-expressing HCCLM3 cell line (HCCLM3-GFP-LC3). Autophagic alterations during metastatic colonization, migration, invasion and detachment were determined by GFP-LC3 analysis and western blot analysis.ResultsLC3 immunohistochemistry of metastases and primary tumors from HCC patients revealed significantly higher LC3 expression in metastases than primary HCC, which suggested a higher level of autophagy in HCC metastases. Further immunohistochemical, TEM, western blot and in vivo GFP-LC3 analyses of lung metastases and primary tumors in mouse model of pulmonary metastasis confirmed that metastatic colonies displayed higher level of autophagy than primary tumors and the early metastatic colonies displayed highest level. The dynamic monitoring of autophagy in cell migration, invasion and detachment showed that autophagy did not significantly alter in those processes.ConclusionsAutophagy is activated in metastatic colonization but not in invasion, migration and detachment of HCC cells. Autophagy may play a role in HCC metastasis via promoting metastatic colonization of HCC cells.
Highlights
Autophagy is a self-degradative process by which cells break down cytoplasmic materials in the lysosome
We compared the autophagic activities in metastasis and primary tumor through a combination of light chain 3 (LC3) immunohistochemical analysis, transmission electron microscopy (TEM), western blot analysis and in vivo GFP-LC3 analysis
Immunohistochemical analysis of primary and metastatic hepatocellular carcinoma (HCC) samples from HCC patients using LC3 as autophagosome marker showed that LC3 expressions in metastases were significantly higher than those in primary HCC tissues (Figure 1)
Summary
Autophagy is a self-degradative process by which cells break down cytoplasmic materials in the lysosome. Autophagy may be activated to function as an alternative energy source to overcome metabolic stress which is often faced by metastatic tumor cells, especially tumor cells that metastasize to organs that provide a poor supply of nutrients [15]. It may be activated after cell detachment from the extracellular matrix (ECM) to resist anoikis induction and sustain cell survival as metastatic cancer cells disseminate in the circulatory system without proper cell-ECM contact [16]. Autophagy may play a role in HCC metastasis via promoting metastatic colonization of HCC cells
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
