Abstract.Increasing data indicate that stress hormones and their corresponding receptors play an important role in the carcinogenesis and progression of hepatocellular carcinoma (HCC). However, there is presently no study investigating the influence of stress hormones in correlation with ß2-AR on human HCC cells. We examined the expression of ·1-and ß-ARs in human HCC cell line HepG2 and MHCC97H cells in comparison with that in human normal hepatic cell line HL-7702 cells (L-02), and the influence of isoproterenol (ISO) on the growth of these HCC cells using blocking agents in correlation with ß2-AR and its downstream signaling pathways. We found that ·1-AR was down-regulated and ß2-AR was up-regulated in HepG2 and MHCC97H cells. ISO dosedependently promoted the growth of both HepG2 and MHCC97H cells. ISO-induced growth and survival of HCC cells were effectively attenuated by ICI 118551, U0126 and PD153035, but not by H-89 or LY294002. ISO transiently activated MAPK/ERK1/2 in tumor cells which could be blocked either by ICI 118551 or U0126, but not by H-89, LY294002, or PD153035. These findings indicate that ISO mimicking a mitogen promoted the growth of HepG2 and MHCC97H cells via ß2-AR-mediated activation of both MAPK/ERK1/2 dependent and independent signaling pathways, and ISO activated MAPK/ERK1/2 by an EGFRindependent mechanism.

Ambient air particulate matter 2.5 (PM2.5) contains many harmful components that can enter the circulatory system and produce reactive oxygen species (ROS) in body. Oxidative stress and DNA damage induced by ROS may affect any cellular macromolecule and lead to DNA double-strand breaks (DSBs). Flavonoids, widely distributed in some herbs and berries, have been proved having anti-oxidative or anti-cancer efficacy. In this study, we investigated whether Flavone, a kind of flavonoids, can protect human bronchial epithelial cells (HBE) from DSBs caused by PM2.5 and how this function is probably implemented. We found that cells exposed to PM2.5 obviously induced viability inhibition, DNA damage and part of apoptosis. However, Flavone treatment prior to PM2.5 apparently improved cell viability, and mitigated the formation of 8-hydroxy-2-deoxyguanosine, the expression of DNA damage-relative protein and cell apoptosis. Our studies demonstrated that PM2.5 induced oxidative DSBs while Flavone ameliorated the DNA damage and increased cell viability probably through influencing DNA repair mechanism of cells.

GRP is a multi-functional peptide, which acts as a stress mediator as well as a growth factor linking stressor to cancer progression. GRP and its high-affinity receptor are useful targets for the diagnosis and treatment of cancers.

Gastrin-releasing peptide (GRP) is a kind of neural peptide that plays an important role in the growth of various human cancer cells. However, very little is known about the relationship between GRP and apoptosis in human hepatocellular carcinoma cells. This study investigated the influences of GRP on apoptosis, as well as the mechanism that triggers HepG2 growth. The effects of GRP on cell proliferation were examined by analysis of lactate dehydrogenase. The GRP, caspase 12, and CHOP protein were detected in HepG2 and HL-7702 cells by Western blot, and endoplasmic reticulum (ER) stress-related mRNA transcription was detected by reverse transcription polymerase chain reaction. To explore the specific pathway by which GRP induces the cell growth, we investigated the apoptosis-related pathway. The expression of GRP in HL-7702 cells inhibited tunicamycin triggered ER stress-associated XBP1, ATF4, and TRAF2 mRNA transcription. Three main ER stress-unfolded protein response pathway proteins, including spliced XBP1, cleaved ATF6, IRE1-α, PERK, and eIF2-α, were increased significantly. Furthermore, the cleaved caspase 12 activation was blocked and CHOP expression was inhibited when GRP was expressed either in HepG2 or HL-7702 cells. In conclusion, GRP triggers the growth of HepG2 cells through blocking the ER stress-mediated pathway.

Abstract. Gastrin-releasing peptide (GRP) plays an important role in regulating tumor growth and migration. However, little is known about its role in human hepatocellular carcinoma (HCC) cells. This study explored the effect of GRP on the growth of HCC HepG2 cells and the underlying mechanisms. Expression of GRP and its cognate receptor (GRPR) were detected by immunocytochemisty, reverse transcription-PCR and Western blotting and compared between two human HCC cell lines (HepG2 and MHCC97H) and a normal hepatic cell line (HL-7702). The effects of GRP on cell proliferation and signaling pathways were examined by Western blotting, MTT assay and flow cytometry. Both GRP and GRPR were overexpressed in HepG2 and MHCC97H cells. GRP activated MAPK/ERK1/2 in HepG2 cells, leading to enhanced proliferation, reduced apoptosis and accelerated cell cycle progression. The effect of GRP on ERK1/2 was effectively attenuated by the GRPR antagonist PD176252 or MEK inhibitor U0126, but not by the TNF-· protease inhibitor TAPI-1 or the EGFR tyrosine kinase inhibitor PD153035. The effect of GRP on the growth of HepG2 cells was significantly attenuated by PD176252 or U0126. GRP serves as a mitogen for HepG2 and MHCC97H cells. GRP promotes the growth of HepG2 cells through interaction with GRPR co-expressed in tumor cells, and subsequently activates MAPK/ERK1/2 via EGFRindependent mechanisms.