Tryptophan 650 of human granulocyte colony-stimulating factor (G-CSF) receptor, implicated in the activation of JAK2, is also required for G- CSF-mediated activation of signaling complexes of the p21ras route

Granulocyte colony-stimulating factor (G-CSF) induces rapid phosphorylation of JAK kinases as well as activation of the p21ras route through interaction with its specific receptor (G-CSF-R). The cytoplasmic membrane-proximal region of G-CSF-R (amino acids 631 to 684) is necessary for proliferation induction and activation of JAK2. In contrast, activation of Shc and Syp, signaling molecules implicated in the p21ras signaling route, depends on the phosphorylation of tyrosine residues located in the membrane-distal region (amino acids 685 to 813) of G-CSF-R. We investigated whether G-CSF-induced activation of signaling complexes of the p21ras route depends on the function of the membrane-proximal cytoplasmic region of G-CSF-R. A G- CSF-R mutant was constructed in which tryptophan 650 was replaced by arginine and expressed in BAF3 cells (BAF/W650R). In contrast to BAF3 cell transfectants expressing wild-type G-CSF-R, BAF/W650-R cells did not proliferate and did not show activation of JAK2, STAT1, or STAT3 in response to G-CSF. Immunoprecipitations with anti-Shc and anti-Grb2 antisera showed that mutant W650R also failed to activate Syp and Shc. These data indicate that the membrane-proximal cytoplasmic domain of G- CSF-R is not only crucial for proliferative signaling and activation of JAK2 and STATs, but is also required for activation of the p21ras route, which occurs via the membrane-distal region of G-CSF-R.     

Whole‐exome sequencing defines the mutational landscape of pheochromocytoma and identifies KMT2D as a recurrently mutated gene

As subsets of pheochromocytomas (PCCs) lack a defined molecular etiology, we sought to characterize the mutational landscape of PCCs to identify novel gene candidates involved in disease development. A discovery cohort of 15 PCCs wild type for mutations in PCC susceptibility genes underwent whole‐exome sequencing, and an additional 83 PCCs served as a verification cohort for targeted sequencing of candidate mutations. A low rate of nonsilent single nucleotide variants (SNVs) was detected (6.1/sample). Somatic HRAS and EPAS1 mutations were observed in one case each, whereas the remaining 13 cases did not exhibit variants in established PCC genes. SNVs aggregated in apoptosis‐related pathways, and mutations in COSMIC genes not previously reported in PCCs included ZAN, MITF, WDTC1, and CAMTA1. Two somatic mutations and one constitutional variant in the well‐established cancer gene lysine (K)‐specific methyltransferase 2D (KMT2D, MLL2) were discovered in one sample each, prompting KMT2D screening using focused exome‐sequencing in the verification cohort. An additional 11 PCCs displayed KMT2D variants, of which two were recurrent. In total, missense KMT2D variants were found in 14 (11 somatic, two constitutional, one undetermined) of 99 PCCs (14%). Five cases displayed somatic mutations in the functional FYR/SET domains of KMT2D, constituting 36% of all KMT2D‐mutated PCCs. KMT2D expression was upregulated in PCCs compared to normal adrenals, and KMT2D overexpression positively affected cell migration in a PCC cell line. We conclude that KMT2D represents a recurrently mutated gene with potential implication for PCC development. © 2015 The Authors. Genes, Chromosomes & Cancer Published by Wiley Periodicals, Inc.     

p38 MAPK对嗜酸性粒细胞和支气管上皮细胞共培养时细胞因子释放的调控作用

目的 了解嗜酸性粒细胞和支气管上皮细胞相互作用诱导细胞因子释放的p38 MAPK信号转导通路.方法 用CD16磁珠抗体分离外周血中嗜酸性粒细胞,以嗜酸性粒细胞和支气管上皮细胞(BEAS-2B)接触共培养为实验模型,观察SB 203580对细胞培养上清液中细胞因子浓度的影响.细胞因子浓度采用ELISA和流式细胞微珠方法测定.结果 SB 203580能够有效抑制BEAS-2B细胞释放IL-6、IL-8(P＜0.05)和嗜酸性粒细胞释放IL-8(P＜0.01).SB 203580对嗜酸性粒细胞与BEAS-2B细胞接触共培养诱导的IL-6、IL-8和IP-10释放具有显著抑制作用(P＜0.001).结论 嗜酸性粒细胞、BEAS-2B细胞单独或相互作用时均通过p38 MAPK信号转导通路释放细胞因子.     

Basic fibroblast growth factor confers a less malignant phenotype in MDA-MB-231 human breast cancer cells

Basic fibroblast growth factor (FGF-2) expression is associated with a more differentiated phenotype, earlier stage of disease, and a better prognosis in breast cancer patients. To determine whether expression of FGF-2 can cause a less malignant phenotype, we engineered MDA-MB-231 cells, a highly dedifferentiated, invasive breast cancer cell line, to express different isoforms of FGF-2. Cells expressed either cytoplasmic, nuclear, or a combination of both FGF-2 isoforms. Western blots of 2 M NaCl washes and of conditioned medium demonstrated that these cells did not export FGF-2. Cells expressing FGF-2 had levels of fibroblast growth factor receptors equivalent with those of control cells. Transformation was assayed by anchorage-independent colony formation and tumor formation in athymic mice. All of the constructs expressing various FGF-2 isoforms had a 60-70% reduction in colony formation in soft agar, but only cells expressing the Mr 18,000 FGF-2 isoform formed fewer and smaller tumors in mice. To determine potential mechanisms responsible for a less malignant phenotype, experiments measuring invasion in Matrigel, the secretion of matrix metalloprotease activity and migration in a modified Boyden chamber and in a patch wound motility assay were carried out. Cells expressing the Mr 18,000 cytoplasmic FGF-2 moiety had a 45% decrease in invasion in Matrigel compared to vector-transfected controls. Cells expressing Mr 18,000 FGF-2 had an increase in Mr 97,000 and Mr 48,000 collagenase, demonstrating that the decreased invasive potential was not due to a down-regulation of gelatinolytic or caseinolytic matrix metalloproteinases. However, motility was decreased in both assays, primarily in cells expressing Mr 18,000 FGF-2, whereas exogenous recombinant human FGF-2 had no effect. These studies demonstrate for the first time that FGF-2 expression can cause a less malignant phenotype in breast cancer cells, possibly as a result of decreased motility and invasion.