BACKGROUND: To clarify the roles of rat sarcoma (Ras)/mitogen-activated protein kinase (MAPK) signaling pathway in oncogenesis and cytodifferentiation of odontogenic tumors, K-Ras gene status and expression of Ras, Raf1, MAPK/extracellular signal-regulated kinase (ERK) kinase (MEK)1, and ERK1/2 proteins were analyzed in ameloblastomas as well as in tooth germs. METHODS: Paraffin sections of 10 tooth germs and 46 benign and 6 malignant ameloblastomas were examined immunohistochemically for the expression of K-Ras, Raf1, MEK1, and ERK1/2. Frozen tissue samples of 22 benign ameloblastomas and 1 malignant (metastasizing) ameloblastoma were analyzed by direct DNA sequencing to detect K-Ras gene alteration. RESULTS: Immunohistochemical reactivity for K-Ras, Raf1, MEK1, and ERK1/2 was detected in both normal and neoplastic odontogenic epithelium, and these molecules were reactive chiefly with odontogenic epithelial cells neighboring the basement membrane. Plexiform ameloblastomas showed slightly stronger expression of these Ras/MAPK signaling molecules than follicular ameloblastomas. Keratinizing cells and granular cells showed decreased reactivity for the signaling molecules. Basal cell ameloblastomas showed slightly stronger reactivity for the signaling molecules than did the other subtypes. K-Ras immunoreactivity in malignant ameloblastomas was lower than that in dental lamina of tooth germs. Direct DNA sequencing showed a GGT to GCT point mutation at codon 12 of K-Ras gene in one ameloblastoma. Conclusion: Expression of K-Ras, Raf1, MEK1, and ERK1/2 in tooth germs and ameloblastomas suggests that Ras/MAPK signaling pathway functions to regulate cell proliferation and differentiation in both normal and neoplastic odontogenic epithelium. K-Ras gene status implied that K-Ras mutations might play a minor role in oncogenesis of odontogenic epithelium. 相似文献
IL-8 mRNA in human gingival epithelial cells (HGECs) is up-regulated by Fusobacterium nucleatum, and up-/down-regulated by Porphyromonas gingivalis in a complex interaction in the early stages (< or = 4 h) after infection. The mechanisms involved in this regulation in response to F. nucleatum and/or P. gingivalis infection, and identification of co-regulated cytokine genes, are the focus of this investigation. Heat, formalin or protease treatment of F. nucleatum cells attenuated the IL-8 mRNA up-regulation. NF-kappaB, mitogen-activated protein kinase (MAPK) p38 and MAPK kinase/extracellular signal-regulated kinase (MEK/ERK) pathways were involved in IL-8 mRNA induction by F. nucleatum. Pretreatment of P. gingivalis with heat, formalin or protease enhanced IL-8 mRNA induction. NF-kappaB, MARK p38, and MEK/ERK pathways were also involved in this induction. In contrast, down-regulation of IL-8 mRNA by P. gingivalis involved MEK/ERK, but not NF-kappaB or MAPK p38 pathways. cDNA arrays analysis revealed that mRNA down-regulation by P. gingivalis is a specific reaction that only a number of genes, e.g. IL-1beta, IL-8, macrophage inflammatory protein-2alpha, and migration inhibitory factor-related protein-14, are affected based on examination of 278 cytokine/receptor genes. These data indicate that F. nucleatum and P. gingivalis trigger specific and differential gene regulation pathways in HGECs. 相似文献
The neurotoxicity ofn-hexane is thought to be caused ultimately by 2,5-hexanedione (2,5-HD), one of then-hexane metabolites. The potentiation ofn-hexane neurotoxicity by co-exposure with MEK, therefore, is suspected to be related to kinetics of 2,5-HD in blood. To clarify the kinetics ofn-hexane metabolites in the mixed exposure ofn-hexane and MEK, rats were exposed to 2000 ppmn-hexane or a mixture of 2000 ppmn-hexane and 2000 ppm MEK, and the time courses of serumn-hexane metabolites were determined. 2,5-HD in serum increased until 2 h after the end of exposure, when serum 2,5-HD concentration reached a peak of 16.35 g/ml in then-hexane-alone group. In contrast, 2,5-HD in the mixed exposure group increased much more slowly during and after exposure than in then-hexane-alone group. It reached a peak of 2.12 g/ml at 8 h after the end of exposure. Serum MBK, a precursor of 2,5-HD in the co-exposure group, was about half in then-hexane-alone group during exposure. However, MBK decreased more slowly in the co-exposure group than in then-hexane-alone group after the end of the exposure. The results suggest that co-exposed MEK might inhibit oxidation ofn-hexane and decrease clearance ofn-hexane metabolites. Co-exposed MEK did not increase serum 2,5-HD, which was considered a main neurotoxic metabolite. Therefore the enhancement of neurotoxicity could not be attributed to increased serum 2,5-HD in the co-exposed group. The mechanism of enhancement of neurotoxicity ofn-hexane by MEK should be studied further. 相似文献
Variable clinical responses, tumor heterogeneity, and drug resistance reduce long-term survival outcomes for metastatic melanoma patients. To guide and accelerate drug development, we characterized tumor responses for five melanoma patient derived xenograft models treated with Vemurafenib. Three BRAFV600E models showed acquired drug resistance, one BRAFV600E model had a complete and durable response, and a BRAFV600V model was expectedly unresponsive. In progressing tumors, a variety of resistance mechanisms to BRAF inhibition were uncovered, including mutant BRAF alternative splicing, NRAS mutation, COT (MAP3K8) overexpression, and increased mutant BRAF gene amplification and copy number. The resistance mechanisms among the patient derived xenograft models were similar to the resistance pathways identified in clinical specimens from patients progressing on BRAF inhibitor therapy. In addition, there was both inter- and intra-patient heterogeneity in resistance mechanisms, accompanied by heterogeneous pERK expression immunostaining profiles. MEK monotherapy of Vemurafenib-resistant tumors caused toxicity and acquired drug resistance. However, tumors were eradicated when Vemurafenib was combined the MEK inhibitor. The diversity of drug responses among the xenograft models; the distinct mechanisms of resistance; and the ability to overcome resistance by the addition of a MEK inhibitor provide a scheduling rationale for clinical trials of next-generation drug combinations. 相似文献
We investigated whether the hyperbaric oxygen (O2) could promote the proliferation of growth-arrested osteoblasts in vitro and the mechanisms involved in this process. Osteoblasts were exposed to different combinations of saturation and pressure of O2 and evaluated at 3 and 7 days. Control cells were cultured under ambient O2 and normal pressure [1 atmosphere (ATA)]; high-pressure group cells were treated with high pressure (2.5 ATA) twice daily; high-O2 group cells were treated with a high concentration O2 (50% O2) twice daily; and high pressure plus high-O2 group cells were treated with high pressure (2.5 ATA) and a high concentration O2 (50% O2) twice daily. Hyperbaric O2 significantly promoted osteoblast proliferation and cell cycle progression after 3 days of treatment. Hyperbaric O2 treatment stimulated significantly increased mRNA expression of fibroblast growth factor (FGF)-2 as well as protein expression levels of Akt, p70S6K, phosphorylated ERK, nuclear factor (NF)-κB, protein kinase C (PKC)α, and phosphorylated c-Jun N-terminal kinase (JNK). Our findings indicate that high pressure and high O2 saturation stimulates growth-arrested osteoblasts to proliferate. These findings suggest that the proliferative effects of hyperbaric O2 on osteoblasts may contribute to the recruitment of osteoblasts at the fracture site. The FGF-2/MEK/ERK 1/2/Akt/p70S6K/NF-κB and PKC/JNK pathways may be involved in mediating this process. 相似文献
Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive, metastatic disease with limited treatment options. Factors contributing to the metastatic predisposition and therapy resistance in pancreatic cancer are not well understood. Here, we used a mouse model of KRAS-driven pancreatic carcinogenesis to define distinct subtypes of PDAC metastasis: epithelial, mesenchymal and quasi-mesenchymal. We examined pro-survival signals in these cells and the therapeutic response differences between them. Our data indicate that the initiation and maintenance of the transformed state are separable, and that KRAS dependency is not a fundamental constant of KRAS-initiated tumors. Moreover, some cancer cells can shuttle between the KRAS dependent (drug-sensitive) and independent (drug-tolerant) states and thus escape extinction. We further demonstrate that inhibition of KRAS signaling alone via co-targeting the MAPK and PI3K pathways fails to induce extensive tumor cell death and, therefore, has limited efficacy against PDAC. However, the addition of histone deacetylase (HDAC) inhibitors greatly improves outcomes, reduces the self-renewal of cancer cells, and blocks cancer metastasis in vivo. Our results suggest that targeting HDACs in combination with KRAS or its effector pathways provides an effective strategy for the treatment of PDAC. 相似文献
Introduction: Combination treatment with a BRAF inhibitor and MEK inhibitor is the standard of care for patients with advanced BRAFV600 mutation-positive melanoma. With the currently available combinations of dabrafenib plus trametinib and vemurafenib plus cobimetinib, median progression-free survival (PFS) of over 12 months has been achieved. However, treatment resistance and disease recurrence remain a clinical challenge.
Areas covered: Encorafenib in combination with bimetinib offers a new approach that may offer benefits over existing BRAF/MEK inhibitor combinations.
Expert opinion: While other BRAF/MEK inhibitor combinations have achieved a median overall survival (OS) of 22 months, patients with advanced BRAF mutation-positive melanoma treated with encorafenib plus binimetinib achieved a median OS of 33.6 months in the phase III COLUMBUS trial. PFS also appears to be improved with encorafenib plus binimetinib. This improved efficacy may be related to the distinct pharmacokinetics of encorafenib, with prolonged binding to the target molecule providing greater BRAF inhibition and increased potency compared with other drugs in the same class. Increased specificity of encorafenib may also result in better tolerability with less off-target effects, including reduced occurrence of pyrexia and photosensitivity. Encorafenib plus binimetinib seems likely to emerge as a valuable therapeutic alternative to established BRAF/MEK inhibitor combinations. 相似文献