Inhibition of breast tumor growth by N(G)-nitro-l-arginine methyl ester (l-NAME) is accompanied by activation of fibroblasts.

Nitric Oxide (NO) is involved in many physiological and pathological processes. It is generated by a family of NO synthases (NOS), being the inducible isoform, iNOS, responsible for higher amounts of NO. Here, we report that pharmacological inhibition of NO production by l-NAME reduces both viability and MAPK activated signalling pathways in iNOS positive human and murine cancer cell lines. In vivo, using syngeneic models, in parallel with tumor reduction induced by l-NAME, collagen deposition and α-SMA positive stromal cells are observed. This observation takes place only when tumor cells express iNOS. In vitro, l-NAME induces viability and differentiation on fibroblast. Our results reveal that NO inhibition contributes to stimulate proliferation and activation of fibroblasts in parallel with tumor reduction of iNOS positive breast cancer.

Extracellular-Signal Regulated Kinase: A Central Molecule Driving Epithelial-Mesenchymal Transition in Cancer.

Epithelial-mesenchymal transition (EMT) is a reversible cellular process, characterized by changes in gene expression and activation of proteins, favoring the trans-differentiation of the epithelial phenotype to a mesenchymal phenotype. This process increases cell migration and invasion of tumor cells, progression of the cell cycle, and resistance to apoptosis and chemotherapy, all of which support tumor progression. One of the signaling pathways involved in tumor progression is the MAPK pathway. Within this family, the ERK subfamily of proteins is known for its contributions to EMT. The ERK subfamily is divided into typical (ERK 1/2/5), and atypical (ERK 3/4/7/8) members. These kinases are overexpressed and hyperactive in various types of cancer. They regulate diverse cellular processes such as proliferation, migration, metastasis, resistance to chemotherapy, and EMT. In this context, in vitro and in vivo assays, as well as studies in human patients, have shown that ERK favors the expression, function, and subcellular relocalization of various proteins that regulate EMT, thus promoting tumor progression. In this review, we discuss the mechanistic roles of the ERK subfamily members in EMT and tumor progression in diverse biological systems.

Diphenyl diselenide induces apoptotic cell death and modulates ERK1/2 phosphorylation in human neuroblastoma SH-SY5Y cells.

Diphenyl diselenide (PhSe)(2) is a synthetic organoselenium compound displaying glutathione peroxidase-like activity. Protective and antioxidant potential of (PhSe)(2) have been extensively investigated in in vivo and in vitro studies. In spite of this, there is a lack of studies addressed to the investigation of potential cytotoxic effect and signaling pathways modulated by this compound. Herein, we aimed to analyze the effects of 24-h treatment with (PhSe)(2) on cell viability and a possible modulation of signaling pathways in human neuroblastoma cell line SH-SY5Y. For this purpose, cells were incubated with (PhSe)(2) (0.3-30 µM) for 24 h and cell viability, apoptotic cell death and modulation of MAPKs (ERK1/2 and p38(MAPK)), and PKC substrates phosphorylation was determined. (PhSe)(2) treatment significantly decreased cell viability and increased the number of apoptotic cells with induction of PARP cleavage. An increase in ERK1/2 phosphorylation was observed at (PhSe)(2) 3 µM. In contrast, higher concentrations of the chalcogenide inhibited ERK1/2, p38(MAPK) and PKC substrate phosphorylation. Pre-treatment with ERK1/2 inhibitor, U0126, increased cell susceptibility to (PhSe)(2). Together, these data indicate a cytotoxic potential of (PhSe)(2) in a neuronal cell line, which appears to be mediated by the ERK1/2 pathway.

A new MAP kinase protein involved in estradiol-stimulated reproduction of the helminth parasite Taenia crassiceps.

MAP kinases (MAPK) are involved in the regulation of cellular processes such as reproduction and growth. In parasites, the role of MAPK has been scarcely studied. Here, we describe the participation of an ERK-like protein in estrogen-dependent reproduction of the helminth parasite Taenia crassiceps. Our results show that 17beta-estradiol induces a concentration-dependent increase in the bud number of in vitro cultured cysticerci. If parasites are also incubated in presence of an ERK-inhibitor, the stimulatory effect of estrogen is blocked. The expression of ERK-like mRNA and its corresponding protein was detected in the parasite. The ERK-like protein was over-expressed by all treatments. Nevertheless, a strong induction of phosphorylation of this protein was observed only in response to 17beta-estradiol. Cross-contamination by host cells was discarded by flow cytometry analysis. Parasite cells expressing the ERK-like protein were exclusively located at the subtegument tissue by confocal microscopy. Finally, the ERK-like protein was separated by bidimensional electrophoresis and then sequenced, showing the conserved TEY activation motif, typical of all known ERK 1/2 proteins. Our results show that an ERK-like protein is involved in the molecular signalling during the interaction between the host and T. crassiceps, and may be considered as target for anti-helminth drugs design.

Entamoeba histolytica: focal adhesion kinase and Erk phosphorylation are altered in the cytoskeleton mutant BG-3.

The Entamoeba histolytica mutant BG-3 has several altered cytoskeletal properties, including the distribution of actin and certain surface characteristics such as osmolarity and electrophoretic mobility. By Western blot analysis and assays for cell adhesion to collagen, we demonstrate that mutant BG-3 shows an increase in the phosphorylation levels of protein kinases that participate in proliferation, adhesion and migration, such as focal adhesion kinase and MAP kinase (Erk2), and that it has also altered its capacity of binding to collagen type I. These results indicate that E. histolytica cytoskeleton integrity plays an important role in adhesion and thus invasion of the host.