U nlimited proliferation is typical of cancer cells, a phenotype supported by several distinct biological events, including enhanced cell proliferation, increased cell survival, and decreased cell death. Studies examining the molecular bases of these events have identified a variety of signaling pathways that are involved in their regulation. The mechanisms by which these different signaling pathways are coordinated to regulate proliferation and survival of cancer cells has remained poorly understood.ROS are normally generated by mitochondria during respiration, but can also be generated by inducible enzyme systems in mammalian cells.(1) Cellular ROS levels increase following exposure to a variety of stress agents, such as anticancer drugs.(2) Upregulation of these highly reactive molecules promotes apoptosis by stimulating the activation of pro-apoptotic signaling molecules, such as JNK and p38 (Fig. 1). (3,4) ROS also function in p53-induced apoptosis. In contrast, low levels of ROS stimulate normal cell proliferation under non-stress conditions; ROS production was reported to be increased in cancer cells (6,7) (Fig. 1). Elevated ROS appear to maintain the constitutive activation of transcription factors (NF-κB and AP-1) during tumor progression.(8) Overexpression of Mox1, the catalytic subunit of NADPH oxidase, induces superoxide generation, leading to the transformation of NIH 3T3 cells.(9) Thus, ROS might play a critical role in the pathogenesis of cancer. The diverse, and even opposing, effects of ROS on cell behavior reflect the complex nature of the biological functions of these highly reactive molecules.Integrins, a large family of adhesion receptors including more than 20 members, mediate highly dynamic cell-cell and cellextracellular matrix interactions. Integrin-mediated cell adhesion regulates a wide variety of biological processes, including cell migration, survival, and proliferation. The association and dissociation of integrin and their ligands are achieved by changes in the conformations of integrin molecules. Adoption of the active conformation triggered by intracellular signaling and cytoskeletal assembly, resulting in ligand binding, integrin clustering, and recruitment of cytoplasmic plaque proteins to integrin attachment sites, called focal adhesions.(10,11) ILK plays a central role in integrin activation and signaling.(12) ILK is composed of three structurally distinct domains, three ankyrin repeats near the N-terminus, a short linker sequence, and a Cterminal kinase domain.Functional studies of ILK1 revealed that GSK3β is a target of ILK1.(13) GSK3β, an important mediator of developmental signaling through the Wnt/wingless pathway, alters the transcriptional activity of Tcf/Lef factors through phosphorylation of the transcriptional cofactor β-catenin.(14,15) GSK3β-mediated phosphorylation targets β-catenin for degradation. Overexpression of ILK1 in epithelial cells induces the phosphorylation of GSK3β at Ser9, an inhibitory modification that results in the stabilization and nuclear trans...

Oral fat sensitivity (OFS, the ability to detect fat) may be related to overeating-induced obesity. However, it is largely unknown whether OFS affects taste preference and eating habits. Therefore, we aimed to evaluate (1) the association between body mass index (BMI) and OFS and (2) the relationship of OFS with four types of taste preference (sweet, sour, salty, and bitter) and eating habits using serial concentrations of oleic acid (OA) homogenized in non-fat milk and a self-reported questionnaire. Participants were 25 healthy Japanese individuals (mean age: 27.0 ± 5.6 years), among whom the OA detection threshold was significantly associated with BMI. Participants were divided into two subgroups based on oral sensitivity to 2.8 mM OA: hypersensitive (able to detect 2.8 mM OA, n = 16) and hyposensitive (unable to detect 2.8 mM OA, n = 9). The degree of sweet taste preference of the hypersensitive group was significantly higher than that of the hyposensitive group. Furthermore, there was significantly higher degree of preference for high-fat sweet foods than low-fat sweet foods in the hypersensitive group. There was also a significant inverse correlation between the OA detection threshold and the degree of both spare eating and postprandial satiety. Thus, OFS is associated not only with BMI, but also with the preference for high-fat sweet foods and eating habits. The present study provides novel insights that measuring OFS may be useful for assessing the risk of obesity associated with overeating in countries, including Japan, where BMI is increasing in the population.

To promote the functional restoration of the nervous system following injury, it is necessary to provide optimal extracellular signals that can induce neuronal regenerative activities, particularly neurite formation. This study aimed to examine the regulation of neuritogenesis by temperature-controlled repeated thermal stimulation (TRTS) in rat PC12 pheochromocytoma cells, which can be induced by neurotrophic factors to differentiate into neuron-like cells with elongated neurites. A heating plate was used to apply thermal stimulation, and the correlation of culture medium temperature with varying surface temperature of the heating plate was monitored. Plated PC12 cells were exposed to TRTS at two different temperatures via heating plate (preset surface temperature of the heating plate, 39.5°C or 42°C) in growth or differentiating medium for up to 18 h per day. We then measured the extent of growth, neuritogenesis, or acetylcholine esterase (AChE) activity (a neuronal marker). To analyze the mechanisms underlying the effects of TRTS on these cells, we examined changes in intracellular signaling using the following: tropomyosin-related kinase A inhibitor GW441756; p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580; and MAPK/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor U0126 with its inactive analog, U0124, as a control. While a TRTS of 39.5°C did not decrease the growth rate of cells in the cell growth assay, it did increase the number of neurite-bearing PC12 cells and AChE activity without the addition of other neuritogenesis inducers. Furthermore, U0126, and SB203580, but not U0124 and GW441756, considerably inhibited TRTS-induced neuritogenesis. These results suggest that TRTS can induce neuritogenesis and that participation of both the ERK1/2 and p38 MAPK signaling pathways is required for TRTS-dependent neuritogenesis in PC12 cells. Thus, TRTS may be an effective technique for regenerative neuromedicine.

Initial cell responses following implantation are important for inducing osteoconductivity. We investigated cell adhesion, spreading, and proliferation in response to native and bovine serum albumin (BSA)-adsorbed disc of hydroxyapatite (HA) or alpha-type alumina (α-Al2O3) using mouse MC3T3-E1 osteoblastic cells and mouse RAW264.7 macrophages. The adsorbed BSA inhibited adhesion and spreading of MC3T3-E1 cells, but did not affect MC3T3-E1 cell proliferation on HA and α-Al2O3 substrates. Thus, MC3T3-E1 cells quickly adhere to original HA before cell binding is impeded by adsorption of BSA in quantities sufficient to inhibit the adhesion of MC3T3-E1 cells. The adsorbed BSA inhibits adhesion of RAW264.7 cells to α-Al2O3, but not to HA. BSA adsorption does not affect RAW264.7 cell spreading and proliferation on both HA and α-Al2O3 substrates. Thus, BSA adsorbed on HA stimulates a different cell response than α-Al2O3. Moreover, quick adherence of osteoblast cells and monocyte-macrophage lineage cells plays a role in HA osteoconductivity.

In this study, we investigated the effect of dorsomorphin, a selective inhibitor of bone morphogenetic protein (BMP) signaling, on rat PC12 pheochromocytoma cell differentiation. PC12 cells can be induced to differentiate into neuron-like cells possessing elongated neurites by nerve growth factor, BMP2, and other inducers. Cells were incubated with BMP2 and ⁄ or dorsomorphin, and the extent of neurite outgrowth was evaluated. Unexpectedly, BMP2-mediated neuritogenesis was not inhibited by co-treatment with dorsomorphin. We also found that treatment with dorsomorphin alone, but not another BMP signaling inhibitor, LDN-193189, induced neurite outgrowth in PC12 cells. To further understand the mechanism of action of dorsomorphin, the effects of this drug on intracellular signaling were investigated using the following signaling inhibitors: the ERK kinase (MEK) inhibitor U0126; the tropomyosinrelated kinase A inhibitor GW441756; and the protein kinase A (PKA) inhibitor H89. Dorsomorphin induced rapid and sustained ERK1 ⁄ 2 activation; however, dorsomorphin-mediated ERK1 ⁄ 2 activation and neuritogenesis were robustly inhibited in the presence of U0126 or H89, but not GW441756. These findings suggest that dorsomorphin has the potential to induce neuritogenesis in PC12 cells, a response that requires the activation of PKA-dependent MEK-ERK1 ⁄ 2 signaling.