Hepatic stellate cells stimulate HCC cell migration via laminin-5 production

Abstract

Activated HSCs (hepatic stellate cells) are the main source of extracellular matrix proteins present in cirrhotic liver on which HCC (hepatocellular carcinoma) commonly develops. HCC cells behave differently according to differences in the surrounding microenvironment. In the present study, we have investigated a mechanism whereby HSCs modulate the migratory activity of HCC cells. We used primary cultures of human HSCs to investigate their effect on Hep3B, Alexander, HLE and HLF HCC cells. The expression of Ln-5 (laminin-5) was documented at transcript and protein levels both in vitro and in vivo. HCC cells strongly adhere, migrate and spread in the presence of HSC-conditioned medium and of co-culture. HSCs produce and secrete Ln-5 in the CM (conditioned medium). The electrophoretic pattern of secreted Ln-5 is consistent with that of a migratory substrate, showing the presence of the γ2x fragment. Blocking antibodies against Ln-5 inhibit HCC migration in the presence of HSC-CM. HCC cells migrate very poorly in the presence of Ln-5 immunodepleted HSC-CM. HCC migration in the presence of HSCs is dependent on the MEK [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase]/ERK pathway, but not the PI3K (phosphoinositide 3-kinase)/Akt pathway. HSC-CM, as well as Ln-5, activates the MEK/ERK but not the PI3K/Akt pathway. In human HCC tissues, Ln-5 is mainly distributed along α-SMA (smooth muscle actin)-positive cells, whereas in peritumoural tissues, Ln-5 is absent. HSCs stimulate HCC migration via the production and secretion of Ln-5.