Plexin-B1 and semaphorin 4D cooperate to promote perineural invasion in a RhoA/ROK-dependent manner

Perineural invasion (PNI) is a tropism of tumor cells for nerve bundles located in the surrounding stroma. It is a pathological feature observed in certain tumors, referred to as neurotropic malignancies, that severely limits the ability to establish local control of disease and results in pain, recurrent growth, and distant metastases. Despite the importance of PNI as a prognostic indicator, its biological mechanisms are poorly understood. The semaphorins and their receptors, the plexins, compose a family of proteins originally shown to be important in nerve cell adhesion, axon migration, and proper central nervous system development. Emerging evidence has demonstrated that these factors are expressed in tissues outside of the nervous system and represent a widespread signal transduction system that is involved in the regulation of motility and adhesion in different cell types. We believe that the plexins and semaphorins, which are strongly expressed in both axons and many carcinomas, play a role in PNI. In this study, we show that plexin-B1 is overexpressed in tissues and cell lines from neurotropic malignancies and is attracted to nerves that express its ligand, semaphorin 4D, in a Rho/Rho kinase-dependent manner. We also demonstrate that nerves are attracted to tumors through this same system of proteins, suggesting that both plexin-B1 and semaphorin 4D are important in the promotion of PN

THE ANABOLIC-ANDROGENIC STEROIDS EXERT DIRECT TOXIC EFFECTS ON NEURON-LIKE CELLS

INTRODUCTION Intake of AAS by atheletes and others in an attempt to gain muscle strength and improve perfor- mance is often associated with toxic effects on the liver, the cardiovascular system, the male and female reproductive systems, and the central nervous system (Trifunovic et al., 1995). In vivo administration of high doses of androgens has been linked to neurobehavioral changes that could be the outward manifestation of neuronal damage. METHODS PC12 cells are a cell line that have been widely used as a model in neurobiological investigations (Fujita et al., 1989; Vaudry et al., 2002). Following exposure to nerve growth factor (NGF), PC12 cells differentiate into a sympathetic-like neuron and develop extensive neuritic processes. Differenciated PC12 cultures, were treat- ed with steroid hormones, methandienone and 17-α-methyltestosterone at final concentrations of 75 μM in complete medium, for 24 h. After treatment several analysis were performed on total proteins and RNA samples, as well as immunofluorescence analysis and vitality assay. RESULTS Genomic effects of AAS treatment, was found. The experimental procedures described above showed that anabolic steroid hormones induced cell death by activation of the apoptotic pathway that include caspase-3 activation, HSP90 cleaved as well as PARP (Santamarina RD et al., 2008). DISCUSSION These preliminary experiments demonstrate that AAS cause an alteration of cellular pathways that control cell survival and differentiation. Particularly, we showed that cell extracts prepared from anabolic steroid hor- mones-treated PC12 cells showed caspase-3 activity and the PARP (the main substrate of protease activity) is cleaved during this death process. In our studies, we also confirmed the cleavage of HSP90 after 24 hours PC12 cells treatment with methandienone and 17-alpha- methyltestosterone, when we used a suprapharmacological concentrations, that means an activation of the apoptotic pathway. Howev- er, we saw a neuritin increases correlated with a loss of neurites. This protein is an important effector of androgen in enhancing periph- eral nerve regeneration following injur. This discrepency could be attributable to the high concentrations of AAS used in our study, which were an attempt to approximate the excessive amounts of steroids used by athletes to enhance performance