We show here that the neurotrophin nerve growth factor (NGF), which has been shown to be a mitogen for breast cancer cells, also stimulates cell survival through a distinct signaling pathway. Breast cancer cell lines (MCF-7, T47-D, BT-20, and MDA-MB-231) were found to express both types of NGF receptors: p140 trkA and p75 NTR . The two other tyrosine kinase receptors for neurotrophins, TrkB and TrkC, were not expressed. The mitogenic effect of NGF on breast cancer cells required the tyrosine kinase activity of p140 trkA as well as the mitogen-activated protein kinase (MAPK) cascade, but was independent of p75 NTR . In contrast, the anti-apoptotic effect of NGF (studied using the ceramide analogue C2) required p75 NTR as well as the activation of the transcription factor NF-kB, but neither p140 trkA nor MAPK was necessary. Other neurotrophins (BDNF, NT-3, NT-4/5) also induced cell survival, although not proliferation, emphasizing the importance of p75 NTR in NGF-mediated survival. Both the pharmacological NF-B inhibitor SN50, and cell transfection with IkBm, resulted in a diminution of NGF anti-apoptotic effect. These data show that two distinct signaling pathways are required for NGF activity and confirm the roles played by p75 NTR and NF-B in the activation of the survival pathway in breast cancer cells. Nerve growth factor (NGF)1 is the archetypal member of the neurotrophin superfamily, which also includes brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), NT-4/5, and NT-6 (1). NGF interacts with two classes of membrane receptor: the TrkA proto-oncogene product p140 trkA , which possesses intrinsic tyrosine kinase activity, and a secondary receptor, p75 NTR , that belongs to the tumor necrosis factor (TNF) receptor family (2). The stimulation of cell survival and cell differentiation by NGF and other neurotrophins have been described primarily in neuronal cell systems (3). Although the neurotrophic effect through p140trkA is known to involve the MAPK cascade, the role of p75 NTR is still controversial; there is evidence that it can both positively and negatively regulate neuronal cell death and differentiation, depending on the cell type examined (4). In some cases, p75NTR is an inducer of apoptosis, even without NGF stimulation (5), whereas in other cases the activation of p75 NTR by NGF results in a protection from cell death (6). In addition to its neurotrophic function, other activities of NGF have been described. For example, NGF can modulate gene expression in monocytes (7), it is chemotactic for melanocytes (8), and its inhibition on p75 NTR can block the migration of Schwann cells (9). NGF also stimulates the proliferation of chromaffin cells (10), lymphocytes (11), and keratinocytes (12). We have previously shown that NGF is mitogenic for cancerous but not normal human breast cells (13), and these data, as well as others showing a role for NGF in the stimulation of prostatic cancer cells (14 -17), implicate NGF in non-neuronal carcinogenesis.Both cellular proliferation as well as tumor c...

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In type 2 diabetes (T2D), hepatic insulin resistance is strongly associated with nonalcoholic fatty liver disease (NAFLD). In this study, we hypothesized that the DNA methylome of livers from patients with T2D compared with livers of individuals with normal plasma glucose levels can unveil some mechanism of hepatic insulin resistance that could link to NAFLD. Using DNA methylome and transcriptome analyses of livers from obese individuals, we found that hypomethylation at a CpG site in (encoding platelet-derived growth factor α) and overexpression are both associated with increased T2D risk, hyperinsulinemia, increased insulin resistance, and increased steatohepatitis risk. Genetic risk score studies and human cell modeling pointed to a causative effect of high insulin levels on CpG site hypomethylation, overexpression, and increased PDGF-AA secretion from the liver. We found that PDGF-AA secretion further stimulates its own expression through protein kinase C activity and contributes to insulin resistance through decreased expression of insulin receptor substrate 1 and of insulin receptor. Importantly, hepatocyte insulin sensitivity can be restored by PDGF-AA-blocking antibodies, PDGF receptor inhibitors, and by metformin, opening therapeutic avenues. Therefore, in the liver of obese patients with T2D, the increased PDGF-AA signaling contributes to insulin resistance, opening new therapeutic avenues against T2D and possibly NAFLD.

Phosphodiesterase (PDE) 4 inhibitors are a class of drugs that can provide novel therapies for asthma and chronic obstructive pulmonary disease. Their development is frequently hampered by the induction of vascular toxicity in rat mesenteric tissue during preclinical studies. Whereas these vascular lesions in rats have been well characterized histologically, little is known about their pathogenesis and in turn, sensitive and specific biomarkers for preclinical and clinical monitoring do not exist. In order to investigate the early molecular mechanisms underlying vascular injury, time-course studies were performed by treating rats for 2-24 h with high doses of the PDE4 inhibitor CI-1044. Transcriptomics analyses in mesenteric tissue were performed using oligonucleotide microarray and real-time RT-PCR technologies and compared to histopathological observations. In addition, protein measurements were performed in serum samples to identify soluble biomarkers of vascular injury. Our results indicate that molecular alterations preceded the histological observations of inflammatory and necrotic lesions in mesenteric arteries. Some gene expression changes suggest that the development of the lesions could follow a primary modulation of the vascular tone in response to the pharmacological effect of the compound. Activation of genes coding for pro- and antioxidant enzymes, cytokines, adhesion molecules, and tissue inhibitor of metalloproteinase 1 (TIMP-1) indicates that biomechanical stimuli may contribute to vascular oxidant stress, inflammation, and tissue remodeling. TIMP-1 appeared to be an early and sensitive predictive biomarker of the inflammatory and the tissue remodeling components of PDE4 inhibitor-induced vascular injury.