Project description:Here we showed that SOX7 was significantly downregulated in different cancer types, especially in lung and breast cancers. Low expression of SOX7 was associated with advanced stage of cancer with shorter overall survival. Cancer cells with loss of SOX7 promoted cell survival and colony formation, suppressed cellular apoptosis and produced a drug resistant phenotype against a variety of chemo/targeting therapeutic agents. Mechanistically, SOX7 induced cellular apoptosis through upregulation of genes associated with both P38 and apoptotic signaling pathway, as well as preventing the proteasome mediated degradation of pro-apoptotic protein BIM. Treatment of either a proteasome inhibitor MG132 or bortezomib, or with a p-ERK/MEK inhibitor U0126 attenuate the SOX7 promoted BIM degradation.
Project description:C-MYC (henceforth MYC) is one of the most frequently overexpressed oncogenes in human cancer and even modestly deregulated MYC expression can initiate ectopic proliferation in many post-mitotic, terminally differentiated cell types in vivo. Metazoan organisms have consequently evolved a number of mechanisms to counteract MYC's oncogenic potential, of which apoptosis is arguably the best understood. However, the mechanisms through which MYC induces apoptosis remains controversial, with some studies implicating p19ARF-mediated stabilization of p53, followed by induction of pro-apoptotic BH3 family member NOXA and PUMA, while others argue for more direct regulation of BH3 proteins, especially BIM. The debate likely stems from the use of different experimental systems, modes of perturbation, and quite possibly different levels of MYC expression. Here, we use a single experimental system to systematically evaluate the roles of p19ARF and BIM during MYC-induced apoptosis, in vitro, in vivo, and in combination with a widely used tumoricidal chemotherapeutic, Doxorubicin. We find a common specific requirement for BIM during MYC-induced apoptosis in multiple settings, which does not extend to the p53-responsive BH3 family member PUMA, and find no evidence of a role for p19ARF during MYC-induced apoptosis in the tissues examined. MYC-ER ChIP-Seq with HC20 anti-ER antibody in MCF10A cells performed on an Illumina IIx Genome Analyzer.
Project description:C-MYC (henceforth MYC) is one of the most frequently overexpressed oncogenes in human cancer and even modestly deregulated MYC expression can initiate ectopic proliferation in many post-mitotic, terminally differentiated cell types in vivo. Metazoan organisms have consequently evolved a number of mechanisms to counteract MYC's oncogenic potential, of which apoptosis is arguably the best understood. However, the mechanisms through which MYC induces apoptosis remains controversial, with some studies implicating p19ARF-mediated stabilization of p53, followed by induction of pro-apoptotic BH3 family member NOXA and PUMA, while others argue for more direct regulation of BH3 proteins, especially BIM. The debate likely stems from the use of different experimental systems, modes of perturbation, and quite possibly different levels of MYC expression. Here, we use a single experimental system to systematically evaluate the roles of p19ARF and BIM during MYC-induced apoptosis, in vitro, in vivo, and in combination with a widely used tumoricidal chemotherapeutic, Doxorubicin. We find a common specific requirement for BIM during MYC-induced apoptosis in multiple settings, which does not extend to the p53-responsive BH3 family member PUMA, and find no evidence of a role for p19ARF during MYC-induced apoptosis in the tissues examined.
Project description:We have established functions of the stimulus dependent MAPKs, ERK1/2 and ERK5 in DRG, motor neuron, and Schwann cell development. Surprisingly, many aspects of early DRG and motor neuron development were found to be ERK1/2 independent and Erk5 deletion had no obvious effect on embryonic PNS. In contrast, Erk1/2 deletion in developing neural crest resulted in peripheral nerves that were devoid of Schwann cell progenitors, and deletion of Erk1/2 in Schwann cell precursors caused disrupted differentiation and marked hypomyelination of axons. The Schwann cell phenotypes are similar to those reported in neuregulin-1 and ErbB mutant mice and neuregulin effects could not be elicited in glial precursors lacking Erk1/2. ERK/MAPK regulation of myelination was specific to Schwann cells, as deletion in oligodendrocyte precursors did not impair myelin formation, but reduced precursor proliferation. Our data suggest a tight linkage between developmental functions of ERK/MAPK signaling and biological actions of specific RTK-activating factors. Microarray analysis on RNA extracts derived from E12.5 Erk1/2CKO(Wnt1) and wildtype DRGs
Project description:The eIF4F translation initiation complex plays a critical role in melanoma resistance to clinical BRAF and MEK inhibitors. In this study, we uncover a novel function of eIF4F in the negative regulation of the RAS/RAF/MEK/ERK mitogen-activated protein kinase (MAPK) signaling pathway. We demonstrate that eIF4F is essential for maintaining optimal ERK signaling intensity in treatment-naïve melanoma cells harboring BRAF or NRAS mutations. Specifically, the dual-specificity phosphatase DUSP6/MKP3, which acts as a negative feedback regulator of ERK activity, requires continuous production in an eIF4F-dependent manner to limit excessive ERK signaling driven by oncogenic RAF/RAS mutations. Treatment with small molecule eIF4F inhibitors disrupts the negative feedback control of MAPK signaling, leading to ERK hyperactivation and EGR1 overexpression in melanoma cells in vitro and in vivo. Furthermore, our quantitative analyses reveal a high spare signaling capacity in the ERK pathway, suggesting that eIF4F-dependent feedback keeps the majority of ERK molecules inactive under normal conditions. Overall, our findings highlight the crucial role of eIF4F in regulating ERK signaling flux and suggest that pharmacological eIF4F inhibitors can disrupt the negative feedback control of MAPK activity in melanomas with BRAF and NRAS activating mutations.
Project description:The mammalian genome contains two ERK/MAP kinase kinase genes, Mek1 and Mek2, which encode dual-specificity kinases responsible for ERK/MAP kinase activation. To define the function of ERK/MAPK signaling pathway in lung development, we performed tissue-specific deletions of Mek1 function in a Mek2 null background. Inactivation of both Mek genes in mesenchyme resulted in several phenotypes including giant omphalocele, skeletal defects, pulmonary hypoplasia, abnormal trachea patterning, and death at birth. Microarray analysis with RNA extracted from lungs of E15.5 Dermo1+/Cre, Mek1+/flox;Mek2-/-;Dermo1+/Cre and Mek1flox/flox;Mek2-/-;Dermo1+/Cre embryos was performed to evaluate the molecular impact of the loss of all Mek alleles in mesenchyme on lung development. . Total RNA was isolated from lungs of E15.5 Dermo1+/Cre embryos (control), from E15.5 Mek1+/flox;Mek2- /-;Dermo1+/Cre embryos (experimental) and from E15.5 Mek1flox/flox;Mek2-/-;Dermo1+/Cre embryos (experimental). Four specimens were analyzed per genotype.
Project description:The RAS family of small GTPases is among the most frequently mutated gene families in human cancer. In pancreatic ductal adenocarcinoma (PDAC), ~95% of cases harbor an activating KRAS mutation, primarily at codon 12, 13, or 61, with G12D the most common overall (40%). In contrast, the KRASQ61L mutation, though constitutively active, is virtually absent in PDAC patient tumors. This suggests that KRASQ61L may engage in distinct, allele-specific signaling that limits its ability to drive tumorigenesis. Determining the mechanisms that limit the occurrence of this mutation will aid in our understanding of the critical KRAS effectors and pathways that drive tumorigenesis. To investigate these mechanisms, we utilized a tightly controlled doxycycline-inducible KRAS expression system in an isogenic, immortalized pancreatic cell line, enabling direct comparison of KRASQ61L to the common PDAC mutant KRASG12D. Using TurboID proximity labeling alongside RNA sequencing, we mapped early effector interactions and transcriptional responses, revealing that KRASQ61L induces greater hyperactivation of the ERK/MAPK pathway, resulting in increased nuclear translocation of ERK1/2. Finally, pancreatic cells are highly tolerant to overexpression of KRASG12D, but KRASQ61L overexpression leads to impaired proliferation and increased apoptosis. These findings provide experimental support for the long-standing "Goldilocks" model of oncogenic signaling, where too much ERK/MAPK pathway activation is detrimental to tumorigenesis. Our work offers a mechanistic explanation for the relative absence of KRASQ61L in PDAC and contributes to our understanding of KRAS allele-specific vulnerabilities, which can inform future therapeutic strategies targeting KRAS-driven pancreatic cancer.