Aberrant activation of the phosphoinositide-3-kinase (PI3K)/ PTEN/Akt pathway, leading to increased proliferation and decreased apoptosis, has been implicated in several human pathologies including cancer. Our previous data have shown that Akt-mediated signaling is an essential mediator in the mouse skin carcinogenesis system during both the tumor promotion and progression stages. In addition, overexpression of Akt is also able to transform keratinocytes through transcriptional and posttranscriptional processes. Here, we report the consequences of the increased expression of Akt1 (wtAkt) or constitutively active Akt1 (myrAkt) in the basal layer of stratified epithelia using the bovine keratin K5 promoter. These mice display alterations in epidermal proliferation and differentiation. In addition, transgenic mice with the highest levels of Akt expression developed spontaneous epithelial tumors in multiple organs with age.

Changes in the molecular and cellular composition of the CNS after injury or disease result in the formation of an inhibitory environment that inhibits the regeneration of adult mammalian CNS neurons. Although a dramatic change in the CNS environment after traumatic injury or disease is hemorrhage because of vascular rupture or leakage of the blood-brain barrier, the potential role for blood proteins in repair processes remains unknown. Here we show that the blood protein fibrinogen is an inhibitor of neurite outgrowth that is massively deposited in the spinal cord after injury. We show that fibrinogen acts as a ligand for ␤3 integrin and induces the transactivation of EGF receptor (EGFR) in neurons. Fibrinogen-mediated inhibition of neurite outgrowth is reversed by blocking either ␤3 integrin or phoshorylation of EGFR. Inhibition of Src family kinases that mediate the cross-talk between integrin and growth factor receptors rescue the fibrinogen-induced phosphorylation of EGFR. These results identify fibrinogen as the first blood-derived inhibitor of neurite outgrowth and suggest fibrinogen-induced EGFR transactivation on neuronal cells as a molecular link between vascular and neuronal damage in the CNS after injury.blood-brain barrier ͉ regeneration ͉ spinal cord injury ͉ transactivation ͉ scar T he identification of common molecular mechanisms that regulate vascular and neural development has expanded the role of the CNS vasculature from nutrition to regulation of axonal guidance, synaptic activity, metabolic trafficking, and adult neurogenesis (1). Although there is a causal interaction between the nervous system and the vasculature, a physical and metabolic barrier between the brain and the systemic circulation, namely the blood-brain barrier (BBB), prohibits the entry of blood proteins from the vasculature into the nervous tissue (2). Leakage of blood components in the CNS parenchyma is a common denominator of several CNS diseases characterized by edema formation and neuronal damage, such as stroke, HIV encephalitis, Alzheimer's disease (AD), multiple sclerosis (MS), glioblastoma, and bacterial meningitis (2). After traumatic injury, such as spinal cord injury (SCI), the primary mechanical injury results in pronounced hemorrhage into the spinal cord and disruption of the blood vessel walls (3). Evidence in AD that correlates microhemorrhages with amyloid plaque formation (4) and in MS that identifies leakage of blood components in the brain as one of the earliest histopathologic abnormalities (5) has postulated a role for blood components in the onset and progression of neurodegeneration. However, the cellular and molecular mechanisms of action of blood proteins within the CNS microenvironment and their contribution to disease pathogenesis remain poorly characterized. Given that inhibition of regeneration in the CNS results in part from the presence of inhibitory factors in the neuronal environment (6), investigating the role of blood proteins as modulators of neuronal functions could be crucial for the ide...

Overexpression of human IGF-1 with the bovine keratin 5 (BK5) promoter (BK5.IGF-1 transgenic mice) induces persistent epidermal hyperplasia and leads to spontaneous skin tumor formation. In previous work, PI3K and Akt activities were found to be elevated in the epidermis of BK5.IGF-1 transgenic mice compared to nontransgenic littermates. In the present study, we examined the importance of the PI3K/Akt signaling pathway in mediating the skin phenotype and the skin tumor promoting action of IGF-1 in these mice. Western blot analyses with epidermal lysates showed that signaling components downstream of PI3K/Akt were altered in epidermis of BK5.IGF-1 mice. Increased phosphorylation of GSK-3 (Ser(9/21)), TSC2(Thr(1462)), and mTOR(Ser(2448)) was observed. In addition, hypophosphorylation and increased protein levels of beta-catenin were observed in the epidermis of BK5.IGF-1 mice. These data suggested that components downstream of Akt might be affected, including cell cycle machinery in the epidermis of BK5.IGF-1 mice. Protein levels of cyclins (D1, E, A), E2F1, and E2F4 were all elevated in the epidermis of BK5.IGF-1 mice. Also, immunoprecipitation experiments demonstrated an increase in cdk4/cyclin D1 and cdk2/cyclin E complex formation, suggesting increased cdk activity in the epidermis of transgenic mice. In further studies, the PI3K inhibitor, LY294002, significantly blocked IGF-1-mediated epidermal proliferation and skin tumor promotion in DMBA-initiated BK5.IGF-1 mice. In addition, inhibition of PI3K/Akt with LY294002 reversed many of the cell cycle related changes observed in untreated transgenic animals. Collectively, the current results supported the hypothesis that elevated PI3K/Akt activity and subsequent activation of one or more downstream effector pathways contributed significantly to the tumor promoting action of IGF-1 in the epidermis of BK5.IGF-1 mice.

Chest pain is a leading reason patients seek medical evaluation. While assays to detect myocyte death are used to diagnose a heart attack (acute myocardial infarction, AMI), there is no biomarker to indicate an impending cardiac event. Transcriptional patterns present in circulating endothelial cells (CEC) may provide a window into the plaque rupture process and identify a proximal biomarker for AMI. Thus, we aimed to identify a transcriptomic signature of AMI present in whole blood, but derived from CECs. Candidate genes indicative of AMI were nominated from microarray of enriched CEC samples, and then verified for detectability and predictive potential via qPCR in whole blood. This signature was validated in an independent cohort. Our findings suggest that a whole blood CEC-derived molecular signature identifies patients with AMI and sets the framework to potentially identify the earlier stages of an impending cardiac event when used in concert with clinical history and other diagnostics where conventional biomarkers indicative of myonecrosis remain undetected.

Akt is a serine/threonine kinase involved in a variety of cellular responses, including cell proliferation and cell survival. Recent studies from our laboratory suggest that Akt signaling may play an important role in skin tumor promotion. To explore this premise, we examined epidermal Akt activation and signaling in response to chemically diverse skin tumor promoters. Mice received single or multiple applications of 12-O-tetradecanoylphorbol-