Key Role of CD151-integrin Complex in Lung Cancer Metastasis and Mechanisms Involved.

Tetraspanin CD151 was found to be upregulated in malignant cell types and has been identified as a tumor metastasis promoter. In this study, we aimed to examine the role of the CD151-integrin complex in lung cancer metastasis and the underlying mechanisms. CD151 QRD194-196 →AAA194-196 mutant was generated and used to transfect A549 human lung adenocarcinoma cells. We found that there was no significant difference in CD151 protein expression between CD151 and CD151-AAA mutant groups. In vitro, CD151-AAA mutant delivery abrogated the migration and invasion of A549 cells, which was promoted by CD151 gene transfer. Furthermore, CD151-AAA delivery failed to activate FAK and p130Cas signaling pathways. Western blot and immunohistochemical staining showed strong CD151 expression in lung cancerous tissues but not in adjacent normal tissues. Increased level of CD151 protein was observed in 20 of the patients and the positive rate of CD151 protein in specimens was 62.5% (20/32). In addition, CD151 was co-localized with α3 integrin at the cell-cell contact site in carcinoma tissues. These results suggested that the disruption of the CD151-α3 integrin complex may impair the metastasis-promoting effects and signaling events induced by CD151 in lung cancer. Our findings identified a key role for CD151-α3 integrin complex as a promoter in the lung cancer.

Ezetimibe Protects Endothelial Cells against Oxidative Stress through Akt/GSK-3ß Pathway.

Ezetimibe was reported to pharmacologically defend against oxidative stress. This study was designed to investigate whether ezetimibe can protect against the oxidative stress induced by oxidized low-density lipoprotein (oxLDL) in vitro and the underlying mechanism. Human umbilical vein endothelial cells (HUVECs) were pretreated with ezetimibe and then exposed to oxLDL for 24 h. TUNEL assay and detectionfor the protein levels of cleaved caspase-3, Bcl-xl and Bcl-2 were employed to assess the oxLDL-induced endothelial apoptosis. Intracellular reactive oxygen species (ROS) generation was evaluated by measuring dichlorofluorescein (DCF) fluorescence. The activities of endothelial antioxidant enzymes [superoxide dismutase (SOD) and catalase] were tested via an enzymatic assay. The mitochondrial membrane potential (MMP) was monitored by flow cytometry using JC-1 staining. Phosphorylation levels of glycogen synthase kinase-3p (p-GSK-3P) and Akt (p-Akt), as well as total GSK-3p and Akt were determined by Western blotting. The results showed that ezetimibe treatment inhibited HUVECs apoptosis, intracellular ROS production, and enhanced antioxidant enzyme activities elicited by oxLDL. HUVECs exposed to oxLDL alone had reduced mitochondrial function, while ezetimibe pre-intervention could significantly rescue the MMP. Furthermore, the protein levels of p-GSK-3p and p-Akt in ezetimibe-pretreated HUVECs were markedly increased as compared with those in oxLDL-induced HUVECs. However, no significant effect on total GSK- 3P and Akt was found in ezetimibe-pretreated HUVECs. Taken together, it was concluded that ezetimibe protects against oxLDL-induced oxidative stress through restoring the MMP, which may be mediated by Akt-dependent GSK-3P phosphorylation.

Role of tetraspanin CD151-α3/α6 integrin complex: Implication in angiogenesis CD151-integrin complex in angiogenesis.

Tetraspanin CD151 mainly associates with laminin-binding integrins and forms CD151-integrin complex. We previously reported that CD151 could be a potential target for angiogenesis, but the mechanisms involved are still unclear. This study investigated the role of CD151-integrin complex in angiogenesis and the signaling mechanisms involved. Here we showed that CD151 and CD151-AAA mutant were both well expressed at the protein level. CD151 gene transfer promoted angiogenesis and improved skin temperature of the lateral ischemic hindlimb, whereas CD151-AAA mutant abrogated the increase in capillary density and skin temperature. Further, CD151-AAA mutant failed to activate the FAK, ERK, PI3K/Akt/eNOS, and Rac1/Cdc42 signaling pathways. Moreover, CD151-AAA mutant was unavailable to promote bovine aortic endothelial cells (BAECs) proliferation and migration, in contrast to the effects of CD151. The results suggested that formation of CD151-integrin complex was likely to be a prerequisite for CD151-induced angiogenesis and signaling pathways.

Adeno associated viral vector-delivered and hypoxia response element-regulated CD151 expression in ischemic rat heart.

AIM: The aim of this study was to improve the delivery efficacy and target specificity of the pro-angiogenic gene CD151 to the ischemic heart. METHODS: To achieve the inducible expression of adeno-associated viral (AAV)-delivered CD151 gene in only the ischemic myocardium, we generated an AAV construct in which CD151 expression can be controlled by the hypoxia response element (HRE) sequence from the human Enolase gene. The function of this vector was examined in rat H9C2 cardiac myoblasts and in ischemic rat myocardium. The expression of CD151 in the areas of ischemic myocardium was confirmed at the mRNA level by real-time PCR and on the protein level by Western blot, whereas the CD151 expression in the microvessels within the areas of ischemic myocardium was detected by immunohistochemistry. RESULTS: HRE significantly enhances the expression of CD151 under hypoxic conditions or in the ischemic myocardium, and forced CD151 expression increases the number of microvessels in the ischemic myocardium. CONCLUSION: The AAV-mediated, HRE regulated delivery of the CD151 gene shows higher expression in the ischemic myocardium and more efficiently targets CD151 to the hypoxic regions after myocardial infarction.