Receptor kinase activity is necessary to mediate production of NO through the insulin receptor. Both PI3K and Akt contribute importantly to this process, whereas the contribution of Ras is small.

Hypertension is associated with insulin-resistant states such as diabetes and obesity. Nitric oxide (NO) contributes to regulation of blood pressure. To gain insight into potential mechanisms linking hypertension with insulin resistance we directly measured and characterized NO production from human umbilical vein endothelial cells (HUVEC) in response to insulin using an amperometric NO-selective electrode. Insulin stimulation of HUVEC resulted in rapid, dose-dependent production of NO with a maximal response of ‫ف‬ 100 nM NO (200,000 cells in 2 ml media; ED 50 ‫ف‬ 500 nM insulin). Although HUVEC have many more IGF-1 receptors than insulin receptors ( ‫ف‬ 400,000, and ‫ف‬ 40,000 per cell respectively), a maximally stimulating dose of IGF-1 generated a smaller response than insulin (40 nM NO; ED 50 ‫ف‬ 100 nM IGF-1). Stimulation of HUVEC with PDGF did not result in measurable NO production. The effects of insulin and IGF-1 were completely blocked by inhibitors of either tyrosine kinase (genestein) or nitric oxide synthase (L-NAME). Wortmannin (an inhibitor of phosphatidylinositol 3-kinase [PI 3-kinase]) inhibited insulin-stimulated production of NO by ‫ف‬ 50%. Since PI 3-kinase activity is required for insulin-stimulated glucose transport, our data suggest that NO is a novel effector of insulin signaling pathways that are also involved with glucose metabolism. ( J. Clin. Invest. 1996. 98:894-898.)

EGFR is a potent stimulator of invasion and metastasis in head and neck squamous cell carcinomas (HNSCC). However, the mechanism by which EGFR may stimulate tumor cell invasion and metastasis still need to be elucidated. In this study, we showed that activation of EGFR by EGF in HNSCC cell line SCC10A enhanced cell migration and invasion, and induced loss of epitheloid phenotype in parallel with downregulation of E-cadherin and upregulation of N-cadherin and vimentin, indicating that EGFR promoted SCC10A cell migration and invasion possibly by an epithelial to mesenchymal transition (EMT)-like phenotype change. Interestingly, activation of EGFR by EGF induced production of matrix metalloproteinase-9 (MMP-9) and soluble E-cadherin (sE-cad), and knockdown of MMP-9 by siRNA inhibited sE-cad production induced by EGF in SCC10A. Moreover, both MMP-9 knockdown and E-cadherin overexpression inhibited cell migration and invasion induced by EGF in SCC10A. The results indicate that EGFR activation promoted cell migration and invasion through inducing MMP-9-mediated degradation of E-cadherin into sE-cad. Pharmacologic inhibition of EGFR, MEK, and PI3K kinase activity in SCC10A reduced phosphorylated levels of ERK-1/2 and AKT, production of MMP-9 and sE-cad, cell migration and invasion, and expressional changes of EMT markers (E-cadherin and N-cadherin) induced by EGF, indicating that EGFR activation promotes cell migration and invasion via ERK-1/2 and PI3K-regulated MMP-9/E-cadherin signaling pathways. Taken together, the data suggest that EGFR activation promotes HNSCC SCC10A cell migration and invasion by inducing EMT-like phenotype change and MMP-9-mediated degradation of E-cadherin into sE-cad related to activation of ERK-1/2 and PI3K signaling pathways.

Purpose: Lignans such as secoisolariciresinol diglucoside in flaxseed, are metabolizes to bioactive mammalian lignans of END and ENL. Because mammalian lignans have chemical structural similarity to the natural estrogen, they are thought to behave like selective estrogen receptor modulators and therefore have anticancer effect against hormone-related cancers. We isolated a series of lignan compounds, named as Vitexins, from the seed of Chinese herb Vitex Negundo. Experimental Design: We purified several Vitexin lignan compounds. Cytotoxic and antitumor effects were analyzed in cancer cells and in tumor xenograft models. In vivo metabolism of Vitexins was determined in rat. Results: Contrasts to the classic lignans, Vitexins were not metabolized to END and ENL. A mixture of Vitexins EVn-50 and purified Vitexin compound 6-hydroxy-4-(4-hydroxy-3-methoxyphenyl)-3-hydroxymethyl-7-methoxy-3, 4-dihydro-2-naphthaldehyde have cytotoxic effect on breast, prostate, and ovarian cancer cells and induces apoptosis with cleavage in poly ADP ribose polymerase protein, up-regulation of Bax, and down-regulation of Bcl-2. This induction of apoptosis seems to be mediated by activation of caspases because inhibition of caspases activity significantly reduced induced apoptosis. We showed a broad antitumor activity of EVn-50 on seven tumor xenograft models including breast, prostate, liver, and cervical cancers. Consistent with in vitro data, EVn-50 treatment induced apoptosis, down-regulated of Bcl-2, and up-regulated Bax in tumor xenografts. Conclusion: Vitexin is a class of nature lignan compounds, whose action and anticancer effect is mediated by the mechanisms different from the classic lignans. Vitexininduced antitumor effect and cytotoxic activity is exerted through proapoptotic process, which is mediated by a decreased Bcl-2/Bax ratio and activation of caspases. (Clin Cancer Res 2009;15(16):5161-9)