GLP-1 reduces the migration of hepatocellular carcinoma cells via suppression of the stress-activated protein kinase/c-Jun N-terminal kinase pathway.

Incretins, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), are hormones secreted from small intestine accompanied with oral intake. We previously showed that transforming growth factor (TGF)-α stimulates the migration of hepatocellular carcinoma (HCC) cells via mitogen-activated protein (MAP) kinases, AKT and Rho-kinase. However, it remains to be elucidated whether incretins affect HCC cell functions. In the present study, therefore, we investigated whether incretins affect the migration of HCC cells using human HCC-derived HuH7 cells. GLP-1, but not GIP, reduced both TGF-α- and hepatocyte growth factor (HGF)-induced cell migration. IBMX, an inhibitor of cyclic nucleotide phosphodiesterase, enhanced the suppressive effect of GLP-1. GLP-1 attenuated the phosphorylation of stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) by TGF-α and HGF. Our results strongly suggest that GLP-1 suppresses TGF-α- and HGF-induced migration of HCC cells through inhibiting the SAPK/JNK signaling pathway, and that the inhibition by GLP-1 is due to cAMP production.

Cellular Functions of Small Heat Shock Proteins (HSPB) in Hepatocellular Carcinoma.

Heat shock proteins (HSPs) play an essential role as molecular chaperones in proteostasis. Small HSPs are a group of low-molecular-weight HSPs in the range of 12- 43 kDa and are classified as HSPB. Within the ten members of the family, HSPB1(HSP27), HSPB5 (αB-crystallin), HSPB6 (HSP20), and HSPB8 (HSP22) ubiquitously exist in various tissues, including liver tissue. These small HSPs undergo phosphorylation as a post-translational modification, and their functions are modulated. Hepatocellular carcinoma (HCC) is one of the most frequent cancers and the fourth leading cause of cancer-related death worldwide. HSPs play a cytoprotective role as molecular chaperones. Thus, HSPB has been generally considered to protect HCC cells and help the progression of HCC. On the other hand, recent studies from our laboratories have demonstrated suppressive roles of phospho-HSPB1, HSPB6, and HSPB8 in the progression of HCC. These findings may provide a basis for a novel defense system by HSPB against HCC progression. This review focuses on the cellular functions of HSPB in HCC and summarizes the current research.

Heat shock protein 70 positively regulates transforming growth factor-α-induced hepatocellular carcinoma cell migration via the AKT signaling pathway.

Heat shock proteins (HSPs) are induced in response to extracellular stress and manage the quality of proteins as molecular chaperones. HSP70, a highly conserved HSP, has been reported to correlate with the proliferation and migration of human cancer cells, such as oral, prostate, lung and liver cancer. Regarding hepatocellular carcinoma (HCC), the HSP70 levels in the tumor tissues from patients are significantly higher than those in the normal liver tissues. HSP70 reportedly upregulates the migration and invasion of HCC. The AKT, p38 mitogen-activated protein kinase (MAPK), c-jun N-terminal kinase (JNK) and Rho-kinase signaling pathways regulate the transforming growth factor (TGF)-α-induced migration of human HCC-derived HuH7 cells. However, the exact mechanism underlying the role of HSP70 in growth factor-induced HCC migration remains unclear. Therefore, in the present study, the mechanism underlying the involvement of HSP70 in TGF-α-induced HCC cell migration was investigated. Treatment with the HSP70 inhibitors VER155008 and YM-08 and the downregulation of HSP70 protein were confirmed to significantly suppress the TGF-α-induced cell migration of HuH7 cells. Both VER155008 and YM-08 reduced the TGF-α-induced phosphorylation of AKT without affecting the phosphorylation of p38 MAPK, JNK or Rho-kinase. These results strongly suggest that HSP70 positively regulates the TGF-α-induced migration of HCC cells via the AKT signaling pathway.