Despite extensive studies on the antitumor properties of berberine, a small molecule derived from Coptidis rhizoma (Huanglian in Chinese) and many other plants, the underlying mechanism remains poorly understood. Here, we found that berberine-induced cell apoptosis in human gastric cancer cells with the increase of the expression level of cleaved poly ADP-ribose polymerase and caspase-3, and the impairment of mitochondrial membrane potential (Δψm) in berberine-treated gastric cancer cells. In our further studies, the results demonstrated that Akt-related mitochondrial pathway may partly involve in the berberine-induced apoptosis in human gastric cancer cells. Moreover, berberine inhibited the Akt/mTOR/p70S6/S6 pathway in berberine-treated BGC-823 cells. Meanwhile, berberine significantly inhibited the activation of Akt and suppressed tumor growth in xenograft nude mice injected with human gastric cancer cells. Thus, our findings reveal that the underlying mechanism that Akt signaling may contribute to berberine-induced cell apoptosis in gastric cancer cells and might represent an important molecular basis for berberine to act as an anticancer agent.

Abstract:It is known that phosphoinositide-specific phospholipases g1 (PLCg1) can trigger several signalling pathways to regulate cell proliferation, differentiation, and metastasis. However, whether this kinase is highly expressive and active in human gastric adenocarcinomas, and whether it can play an important role in the development of the cancer, have not yet been investigated. The aim of the study was to investigate the expression of PLCg1 in human gastric adenocarcinoma, while the question of whether PLCg1 can be activated through protein kinase B (Akt) signalling pathways to regulate cell migration was further explored using human gastric adenocarcinoma BGC-823 cell line. The expression of PLCg1 in human adenocarcinoma was detected using immunohistochemical staining. The BGC-823 cells were cultured and treated with inhibitors or transfected with plasmid construction. The cell migration of BGC-823 cells was measured with wound healing assay, cell migration assay, and the ruffling assay. The expression levels of PLCg1 and its related signal molecules in BGC-823 cells were assessed using Western blot analysis or gelatine zymography assay. PLCg1 was highly expressed in human gastric adenocarcinomas, especially in the region with lymph node metastasis. It was shown that migration of BGC-823 cells in vitro depends on PLCg1 activation. This activation is mediated through Akt, an upstream of PLCg1 that triggers the PLCg1/extracellular signal-regulated kinase (ERK)/matrix metalloproteinase (MMP) pathway in BGC-823 cells. PLCg1 activities play an important role in the metastasis of gastric adenocarcinoma, and may serve as a potential therapeutic target in this type of cancer.

Phosphoinositide specific phospholipase Cγ (PLCγ) activates diacylglycerol (DAG)/protein kinase C (PKC) and inositol 1,4,5-trisphosphate (IP3)/Ca2+/calmodulin-dependent protein kinase II (CaMK II) axes to regulate import events in some cancer cells, including gastric adenocarcinoma cells. However, whether DAG/PKCδ and IP3/Ca2+/CaMK IIβ axes are simultaneously involved in PLCγ1-driven cell proliferation and migration of human gastric adenocarcinoma cells and the underlying mechanism are not elucidated. Here, we investigated the role of DAG/PKCδ or CaMK IIβ in PLCγ1-driven cell proliferation and migration of human gastric adenocarcinoma cells, using the BGC-823 cell line. The results indicated that the inhibition of PKCδ and CaMK IIβ could block cell proliferation and migration of BGC-823 cells as well as the effect of inhibiting PLCγ1, including the decrease of cell viability, the increase of apoptotic index, the down-regulation of matrix metalloproteinase (MMP) 9 expression level, and the decrease of cell migration rate. Both DAG/PKCδ and CaMK IIβ triggered protein kinase B (Akt)/mammalian target of rapamycin (mTOR)/S6 pathway to regulate protein synthesis. The data indicate that DAG/PKCδ and IP3/Ca2+/CaMK IIβ operate in parallel to each other in PLCγ1-driven cell proliferation and migration of human gastric adenocarcinoma cells through Akt/mTOR/S6 pathway, with important implication for validating PLCγ1 as a molecular biomarker in early gastric cancer diagnosis and disease surveillance.