The JNK,ERK and p53 pathways play distinct roles in apoptosis mediated by the antitumor agents vinblastine,doxorubicin, and etoposide

Assessment of specific apoptosis and survival pathways implicated in anticancer drug action is important for understanding drug mechanisms and modes of resistance in order to improve the benefits of chemotherapy. In order to better examine the role of mitogen-activated protein kinases, including JNK and ERK, as well as the tumor suppressor p53, in the response of tumor cells to chemotherapy, we compared the effects on these pathways of three structurally and functionally distinct antitumor agents. Drug concentrations equal to 50 times the concentration required to reduce cell proliferation by 50% were used. Vinblastine, doxorubicin, or etoposide (VP-16) induced apoptotic cell death in KB-3 carcinoma cells, with similar kinetic profiles of PARP cleavage, caspase 3 activation, and mitochondrial cytochrome c release. All three drugs strongly activated JNK, but only vinblastine induced c-Jun phosphorylation and AP-1 activation. Inhibition of JNK by SP600125 protected cells from drug-induced cytotoxicity. Vinblastine caused inactivation of ERK whereas ERK was unaffected in cells exposed to doxorubicin or VP-16. Inhibition of ERK signaling by the MEK inhibitor, U0126, potentiated the cytotoxic effects of vinblastine and doxorubicin, but not that of VP-16. Vinblastine induced p53 downregulation, and chemical inhibition of p53 potentiated vinblastine-induced cell death, suggesting a protective effect of p53. In contrast, doxorubicin and VP-16 induced p53, and inhibition of p53 decreased drug-induced cell death, suggesting a pro-apoptotic role for p53. These results highlight the differential roles played by several key signal transduction pathways in the mechanisms of action of key antitumor agents, and suggest ways to specifically potentiate their effects in a context-dependent manner. In addition, the novel finding that JNK activation can occur without c-Jun phosphorylation or AP-1 activation has important implications for our understanding of JNK function.     

Eating ourselves to death (and despair): The contribution of adiposity and inflammation to depression

Obesity and related metabolic conditions are of epidemic proportions in most of the world, affecting both adults and children. The accumulation of lipids in the body in the form of white adipose tissue in the abdomen is now known to activate innate immune mechanisms. Lipid accumulation causes adipocytes to directly secrete the cytokines interleukin (IL) 6 and tumor necrosis factor α (TNFα), but also monocyte chemoattractant protein 1 (MCP-1), which results in the accumulation of leukocytes in fat tissue. This sets up a chronic inflammatory state which is known to mediate the association between obesity and conditions such as cardiovascular disease, type 2 diabetes, and cancer. There is also a substantial literature linking inflammation with risk for depression. This includes the observations that: (1) people with inflammatory diseases such as multiple sclerosis, cardiovascular disease, and psoriasis have elevated rates of depression; (2) many people administered inflammatory cytokines such as interferon α develop depression that is indistinguishable from depression in non-medically ill populations; (3) a significant proportion of depressed persons show upregulation of inflammatory factors such as IL-6, C-reactive protein, and TNFα; (4) inflammatory cytokines can interact with virtually every pathophysiologic domain relevant to depression, including neurotransmitter metabolism, neuroendocrine function, and synaptic plasticity. While many factors may contribute to the association between inflammatory mediators and depression, we hypothesize that increased adiposity may be one causal pathway. Mediational analysis suggests a bi-directional association between adiposity and depression, with inflammation possibly playing an intermediary role.     

氯胺酮致小鼠精神分裂样症状及其机制探讨

目的观察氯胺酮致小鼠精神分裂样症状,血清肌酸激酶（CK）、一氧化氮（NO）的改变,及对额叶MEK1 mRNA、ERK2 mRNA表达的影响。方法将40只昆明小鼠随机分为生理盐水组和氯胺酮小、中、大剂量4组。腹腔注射7d后观测行为学改变,用紫外分光光度法测定血清CK和NO水平,用RT-PCR方法检测额叶MEK1、ERK2的表达。结果与生理盐水组相比,给药组小鼠在行为学指标上有明显改变,以大、中剂量组显著,差异有高度统计学意义（P〈0.01）;各给药组小鼠血清CK活性均有不同程度增高,但仅大剂量组的差异有高度统计学意义（P〈0.01）,血清NO含量均显著增高,差异均有高度统计学意义（P〈0.01）;额叶MEK1的表达,中剂量组和大剂量组均明显下调,ERK2的表达在大剂量组明显下调,差异均有统计学意义（P〈0.05或〈0.01）。结论氯胺酮增加了小鼠血清CK活性和NO含量,抑制MEK1-ERK2信号转导通路的激活,使其产生精神分裂样症状,这可能也是精神分裂症的发病机制之一。     

Lead-induced cell signaling cascades in GT1-7 cells

The effects of lead on the signal transduction pathways that may be involved in the release of gonadotropin-releasing hormone (GnRH) from neurons in the hypothalamus have not been well defined. Using the GT1-7 cell line, an in vitro model for GnRH-secreting neurons, we examined signal transduction pathways directly affected by lead. We found that lead-induced phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1 and ERK2), as well as p90RSK and cAMP response element-binding protein (CREB), but did not induce IkappaB degradation. MEK1/2 inhibitor (PD98059) suppressed lead-induced ERK and p90RSK activation. Neither PKC inhibitors (Go6983, Go6976) nor CaMKII inhibitor (KN-62) had a pronounced effect on lead-induced ERK1 and ERK2 phosphorylation. However, MEK1/2 inhibitor, CaMKII inhibitor, and PKC inhibitor significantly suppressed lead-induced CREB phosphorylation. These results indicate that lead-activated PKC, CaMKII and MEK/ERK/p90RSK pathways simultaneously, all of which contributed to CREB phosphorylation. Our results also indicate that lead-induced p90RSK and CREB activation does not alter expression of early response genes like c-fos. We conclude that lead activates PKC, CaMKII or MEK-ERK-p90RSK pathways in GT1-7 cells, leading to CREB phosphorylation and modulation of gene expression.     

PACMEL: A phase 1 dose escalation trial of trametinib (GSK1120212) in combination with paclitaxel

BackgroundWe sought to determine the maximal tolerated dose of the MEK inhibitor trametinib with weekly paclitaxel, with a view to exploring the combination’s activity in melanoma lacking a BRAF V600 mutation.MethodsIn this phase 1 study we used a fixed dose of paclitaxel (80 mg/m² intravenous (IV) on days 1, 8 and 15 of each 4 week cycle) and escalated the dose of trametinib (to a maximum 2 mg orally (PO) daily), following a 3 + 3 design. Eligible patients had advanced melanoma and could have received up to two previous lines of treatment for metastatic disease.Findings15 patients were enrolled, all but one of whose melanoma was wild type for BRAF at codon 600. The maximal monotherapy dose of trametinib proved tolerable with weekly paclitaxel. The most frequent adverse events observed were rash and fatigue. Six (40%) partial responses were reported, including four of eight patients with NRAS mutations. Median progression free survival was 5.5 months (95% confidence interval (CI) 1.8–7.8 months) and overall survival, 14.1 months (95% CI 4.6–not reached).InterpretationTrametinib can safely be given with weekly paclitaxel at the full monotherapy dose. In this small group promising progression free and overall survival were observed in patients with melanoma lacking a V600 BRAF mutation.     

Novel investigational drugs active as single agents in multiple myeloma

Introduction: Multiple myeloma (MM) is a hematologic malignancy characterized by proliferation of malignant plasma cells. patient outcome has improved markedly over the last decades due to the introduction of novel therapeutic agents such as bortezomib, thalidomide and lenalidomide. However, MM still remains largely incurable and patients eventually become refractory to available treatments. To address this unmet medical need, a variety of new molecules are currently being developed in preclinical models and/or are being investigated in clinical studies.

Areas covered: We summarized available data on new investigational drugs showing anti-myeloma single-agent activity and that might have a role in the future therapeutic armamentarium against MM. Besides their single-agent activity, the synergic potential of these new agents with the currently approved drugs will be pivotal in their integration into consolidated MM backbone therapies. The drugs discussed include alkylators, new proteasome inhibitors, novel anti-CD38 monoclonal antibodies, Bcl-2 inhibitors, Cyclin-Dependent-Kinase inhibitor, Kinesin-spindle protein inhibitors, MEK1/2 inhibitors, AKT inhibitors and PIM-Kinase inhibitors.

Expert opinion: Isatuximab, oprozomib, melflufen, venetoclax and filanesib seem to be the most promising agents with single agent activity. Nevertheless, lack of clinical activity as single agent does not imply clinical inefficacy in combination treatments.     

Developmental dosing with a MEK inhibitor (PD0325901) rescues myopathic features of the muscle-specific but not limb-specific Nf1 knockout mouse

Neurofibromatosis Type 1 (NF1) is a common autosomal dominant genetic disorder While NF1 is primarily associated with predisposition for tumor formation, muscle weakness has emerged as having a significant impact on quality of life. NF1 inactivation is linked with a canonical upregulation Ras-MEK-ERK signaling. This in this study we tested the capacity of the small molecule MEK inhibitor PD0325901 to influence the intramyocellular lipid accumulation associated with NF1 deficiency. Established murine models of tissue specific Nf1 deletion in skeletal muscle (Nf1_MyoD^?/?) and limb mesenchyme (Nf1_Prx1^?/?) were tested.Developmental PD0325901 dosing of dams pregnant with Nf1_MyoD^?/? progeny rescued the phenotype of day 3 pups including body weight and lipid accumulation by Oil Red O staining. In contrast, PD0325901 treatment of 4?week old Nf1_Prx1^?/? mice for 8?weeks had no impact on body weight, muscle wet weight, activity, or intramyocellular lipid. Examination of day 3 Nf1_Prx1^?/? pups showed differences between the two tissue-specific knockout strains, with lipid staining greatest in Nf1_MyoD^?/? mice, and fibrosis higher in Nf1_Prx1^?/? mice.These data show that a MEK/ERK dependent mechanism underlies NF1 muscle metabolism during development. However, crosstalk from Nf1-deficient non-muscle mesenchymal cells may impact upon muscle metabolism and fibrosis in neonatal and mature myofibers.     

联合抑制Notch2和MEK/ERK通路对胃癌细胞增殖的影响

目的探讨Notch2和MEK/ERK信号通路在胃癌细胞SGC-7901中是否存在交叉作用。方法采用体外化学合成的特异性针对Notch2的siRNA(Notch2siRNA)和丝裂原激活蛋白激酶(MEK)/细胞外信号调节激酶(ERK)信号通路的抑制剂PD98059,分别单独和联合处理体外培养的胃癌SGC-7901细胞,以转染阴性对照siRNA(control siRNA)细胞作为siRNA对照组,并设不给予任何转染的空白对照组。免疫印迹(Western Blotting)法检测磷酸化ERK1/2(p-ERK)1/2和Notch2蛋白的表达水平。比色法(MTT)检测癌细胞增殖抑制率。结果Notch2siRNA能降低蛋白Notch2的表达水平,并抑制癌细胞增殖[(38.26±1.82)%],而p-ERK的表达水平则较对照组增加。PD98059能降低p-ERK的表达水平,并抑制癌细胞的增殖[(30.05±3.16)%],Notch2水平则无明显变化,联合应用Notch2siRNA和PD98059能明显降低p-ERK和Notch2蛋白的表达水平,与Notch2siRNA或PD98059单独应用比较,显著抑制癌细胞增殖率,差异有统计学意义[(72.55±5.30)%,P0.01]。结论特异性抑制Notch2信号通路,且抑制MEK/ERK通路可进一步增强抑制Notch2通路的抗肿瘤增殖效果,提示MEK/ERK和Notch2 2条信号通路在胃癌SGC-7901细胞中存在交叉作用。