Leptin, secreted by adipocytes, regulates satiety and energy expenditure. Several forms of leptin receptors produced by alternative mRNA splicing are found in many tissues, including the hypothalamus, liver, lung, kidney, hematopoietic cells, and gonads, suggesting that leptin exerts effects in these tissues. In accordance with the distribution of leptin receptors, there is accumulating evidence that leptin plays various roles in reproduction, hematopoiesis, and the immune systems in addition to the regulation of food intake and energy expenditure. In the present study, we examined the in vitro effects of leptin on proliferation of a mouse embryonic cell line, C3H10T1/2, and its mechanism of action. Leptin caused a dose-and time-dependent increase in mitogen-activated protein kinase (MAPK) activity that was accompanied by an increase in C3H10T1/2 cell number. The MAPK kinase-1-specific inhibitor PD98059 completely blocked the increases in both MAPK activity and cell proliferation caused by leptin. These findings indicate that leptin stimulates the proliferation of C3H10T1/2 cells via the MAPK cascade.The ob gene has been cloned as a genetic factor responsible for obesity in genetically obese rodents, ob/ob mice (1). The ob gene product (leptin), mutated in ob/ob mice, serves as a satiety factor secreted from adipose tissue and plays an important role in regulating body weight through its receptor in the hypothalamus (1-4). In addition to regulating body weight, leptin also influences reproductive, hematopoietic, and immune systems in which its receptors are expressed (5-10), suggesting that leptin also has extrahypothalamic actions. Furthermore, leptin receptors are expressed in various tissues including lung, kidney, testis, and adipose tissue (11,12). These findings suggest that leptin plays diverse roles in many systems. However, the mechanism of its signal transduction in these organs remains unclear.Recently, STATs 1 have been suggested to be involved in the signal transduction mechanism of leptin. It was reported that leptin activated STAT-1, -3, and -5 (13) and in artificial reconstruction systems using Cos cells transfected with leptin receptors and STATs. Furthermore, activation of STAT-3 by leptin was observed in the hypothalamus in vivo (15). We recently found that leptin induced tyrosine phosphorylation of several cellular proteins including STAT-1 in ACHN cells (cloned human renal carcinoma cells) and suggested that ACHN cells were useful for analyzing the signal transduction mechanism of leptin (16).On the other hand, pathways other than STATs may be involved in leptin signal transduction system. Because leptin is considered to be a member of the cytokine family from the results of structural analysis (17), its signal transduction system may be similar to those of other cytokines. Many cytokines stimulate a molecular cascade coupled with Ras activation (18 -20). p21 ras plays a key role in the phosphorylation and activation of mitogen-activated protein kinases (MAPKs) (21, 22), which in turn phosp...

This retrospective study was conducted in Japan to determine the incidence, risk factors and outcomes of sinusoidal obstruction syndrome (SOS) after allogeneic hematopoietic stem cell transplantation (HSCT). Among 4290 patients undergoing allogeneic HSCT between 1999 and 2010, 462 were diagnosed with SOS according to the Seattle criteria (cumulative incidence, 10.8%). The cumulative incidence of SOS diagnosed by the modified Seattle criteria was 9.3%. Of 462 patients, 107 met the Baltimore criteria and 168 had severe SOS with renal and/or respiratory failure. The median onset for SOS was 12 days after HSCT (range, À 2-30). Overall survival at day 100 was 32% for SOS and 15% for severe SOS. Multivariate analyses showed that significant independent risk factors for SOS were the number of HSCTs, age, performance status, hepatitis C virus-seropositivity, advanced disease status and myeloablative regimen. SOS was highly associated with overall mortality (hazard ratio, 2.09; P o 0.001). Our retrospective survey showed that the cumulative incidence of SOS in Japan was 10.8%, similar to that previously reported in Western countries, and that the overall survival of patients who developed SOS was low. Furthermore, several risk factors were identified. Preventive and therapeutic strategies for high-risk SOS patients must be established to improve overall survival.

We cloned the 5-flanking region of the human growth hormone-releasing hormone receptor (GHRH-R) gene and determined the nucleotide sequence of 2.7 kilobases upstream from the translation start site. RNase protection analysis showed the major transcription start site is 122 base pairs upstream from the translation start site. The 5-end of the longest product of 5-rapid amplification of cDNA ends was close to the site. There were no typical TATA homologies but several putative regulatory elements including Pit-1-binding site-like element. Transient transfection studies using a luciferase reporter gene demonstrated that 5-flanking region had promoter activity in GH3 cells (derived from rat pituitary tumor) but not in nonpituitary cells, BeWo and HeLa cells. However, co-transfection of Pit-1 expression vector increased luciferase activity in BeWo cells. Deletion study showed that the regions from ؊310 to ؊130 and from ؊130 to ؊120 were important for the GHRH-R gene expression in GH3 cells, although the latter contributed less to the gene expression. In BeWo cells cotransfected with Pit-1 expression vector, the region from ؊310 to ؊130 was essential for the Pit-1-dependent expression of GHRH-R gene. The region from ؊310 to ؊120 has two putative Pit-1-binding sites, P1 and P2, located from ؊129 to ؊123 and from ؊171 to ؊160, respectively. Both mobility shift assay and DNase-I footprint analysis showed that P2 had much higher Pit-1 binding affinity than P1. Mutation of P2 decreased GHRH-R gene expression in GH3 cells. These findings were consistent with the results that the region from ؊310 to ؊130 is an important element for Pit-1-dependent expression of GHRH-R gene. Growth hormone-releasing hormone (GHRH)1 plays a major role in stimulating both synthesis and release of growth hormone (GH) in the anterior pituitary through its specific receptor. So far, the GHRH receptor (GHRH-R) has been cloned in human (1, 2), mouse (3), rat (1), and pig (4). The GHRH-R is a member of G protein-coupled receptor family and transduces GHRH-dependent increase in intracellular cAMP via G s activation for stimulating somatotroph proliferation and GH gene expression (1-4). Lin et al. (5) demonstrated that one amino acid substitution of the GHRH-R in the little mouse, showing genetically transmitted dwarfism, caused GH deficiency and somatotroph hypoplasia. In addition, an amber-type mutation (Glu72Stop) of the GHRH-R in humans was demonstrated to cause profound GH deficiency (6). These genetic disorders suggest the physiological significance of GHRH-R in hypothalamopituitary GH axis.The relationship between the dynamics of GHRH-R expression and GH secretion remains to be clarified. Not only the functional defects of GHRH-R but also the amount of GHRH-R should affect GH synthesis and secretion in the pituitary. Hypothalamic hormone, neurotransmitters, various hormonal states, and nutrition all could modulate the activity of the GHRH-GH axis. For instance, glucocorticoids potentiate GHRH action and enhance GH secretion in rats (7-9), where...

The clinical impact of KIT mutations in core binding factor acute myeloid leukemia (CBF-AML) is still unclear. In the present study, we analyzed the prognostic significance of each KIT mutation (D816, N822K, and other mutations) in Japanese patients with CBF-AML. We retrospectively analyzed 136 cases of CBF-AML that had gone into complete remission (CR). KIT mutations were found in 61 (45%) of the patients with CBF-AML. D816, N822K, D816 and N822K, and other mutations of the KIT gene were detected in 29 cases (21%), 20 cases (15%), 7 cases (5%), and 5 cases (4%), respectively. The rate of relapse-free survival (RFS) and overall survival (OS) in patients with D816 and with both D816 and N822K mutations was significantly lower than in patients with other or with no KIT mutations (RFS: p < 0.001, OS: p < 0.001). Moreover, stratified analysis of the chromosomal abnormalities t(8;21)(q22;q22) and inv(16)(p13.1q22), t(16;16)(p13.1;q22) showed that D816 mutation was associated with a significantly worse prognosis. In a further multivariate analysis of RFS and OS, D816 mutation was found to be an independent risk factor for significantly poorer prognosis. In the present study, we were able to establish that, of all KIT mutations, D816 mutation alone is an unfavorable prognostic factor.

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