- [Show abstract] [Hide abstract] ABSTRACT: We have recently demonstrated that protein kinase Cι (PKCι) promotes a stem-like, tumor-initiating cell phenotype in KRAS-driven lung adenocarcinoma by activating a novel ELF3-NOTCH3 signaling axis.11. Ali SA, Justilien V, Jamieson L, Murray NR, Fields AP. Protein Kinase Ciota Drives a NOTCH3-dependent Stem-like Phenotype in Mutant KRAS Lung Adenocarcinoma. Cancer Cell 2016; 29: 367-378.View all references Combined PKCι and NOTCH inhibition was identified as a novel strategy for the treatment of KRAS-driven lung adenocarcinoma.
- [Show abstract] [Hide abstract] ABSTRACT: Lung cancer is the leading cause of cancer death in the US with ∼124,000 new cases annually, and a five year survival rate of ∼16%. Mutant KRAS-driven lung adenocarcinoma (KRAS LADC) is a particularly prevalent and deadly form of lung cancer. Protein kinase Cι (PKCι) is an oncogenic effector of KRAS that activates multiple signaling pathways that stimulate transformed growth and invasion, and maintain a KRAS LADC tumor-initiating cell (TIC) phenotype. PKCι inhibitors used alone and in strategic combination show promise as new therapeutic approaches to treatment of KRAS LADC. These novel drug combinations may improve clinical management of KRAS LADC.
- [Show abstract] [Hide abstract] ABSTRACT: We report that the protein kinase Cι (PKCι) oncogene controls expression of NOTCH3, a key driver of stemness, in KRAS-mediated lung adenocarcinoma (LADC). PKCι activates NOTCH3 expression by phosphorylating the ELF3 transcription factor and driving ELF3 occupancy on the NOTCH3 promoter. PKCι-ELF3-NOTCH3 signaling controls the tumor-initiating cell phenotype by regulating asymmetric cell division, a process necessary for tumor initiation and maintenance. Primary LADC tumors exhibit PKCι-ELF3-NOTCH3 signaling, and combined pharmacologic blockade of PKCι and NOTCH synergistically inhibits tumorigenic behavior in vitro and LADC growth in vivo demonstrating the therapeutic potential of PKCι-ELF3-NOTCH3 signal inhibition to more effectively treat KRAS LADC.
- [Show abstract] [Hide abstract] ABSTRACT: Specific transcription factors and co-regulatory proteins cooperate to regulate the expression of phenotypic genes involved in driving the specific cell lineage. Epigenetic mechanisms such as histone and DNA CpG-methylation that are controlled by regulatory complexes, also contribute in regulating cell fate decisions by regulating cellular transcription. During cancer a transformed cell faces cascade of external and internal signaling events that cause disruption of regulatory complexes and lead to failure of transcriptional machinery to run microenvironment. In general, together perturbation of transcriptional and epigenetic events in a cancer cell results in abnormal regulation of cell proliferation, growth and differentiation. These major biological mechanisms regulate tumor growth and progression during cancer. Recent findings have explored the existence of cancer "stem-like" cells in the tumor that are resistant to chemo-therapy and radio-therapy. These "stem-like" cells can be identified in the tumor due to the expression of marker genes and epigenetic modifications. Many specific post-translational epigenetic modifications such as, acetylation, methylation and phosphorylation of the histones are linked to transcriptional regulation of cancer "stem-like" phenotype. The current review briefly summarizes the importance of transcriptional regulatory complexes, epigenetic markings and molecular events involved in "stem-like" cell fate determination during cancer.
Dataset: ccell25 2 c1 (5)-CMYK
Dataset: ccell25 2 c1 (5)-CMYK
- [Show abstract] [Hide abstract] ABSTRACT: We report that two oncogenes coamplified on chromosome 3q26, PRKCI and SOX2, cooperate to drive a stem-like phenotype in lung squamous cell carcinoma (LSCC). Protein kinase Cι (PKCι) phosphorylates SOX2, a master transcriptional regulator of stemness, and recruits it to the promoter of Hedgehog (Hh) acyltransferase (HHAT) that catalyzes the rate-limiting step in Hh ligand production. PKCι-mediated SOX2 phosphorylation is required for HHAT promoter occupancy, HHAT expression, and maintenance of a stem-like phenotype. Primary LSCC tumors coordinately overexpress PKCι, SOX2, and HHAT and require PKCι-SOX2-HHAT signaling to maintain a stem-like phenotype. Thus, PKCι and SOX2 are genetically, biochemically, and functionally linked in LSCC, and together they drive tumorigenesis by establishing a cell-autonomous Hh signaling axis.
- [Show abstract] [Hide abstract] ABSTRACT: The Runt-related transcription factor Runx2 is essential for bone development but is also implicated in progression of several cancers of breast, prostate and bone, where it activates cancer-related genes and promotes invasive properties. The transforming growth factor β (TGF-β) family member bone morphogenetic protein-3B (BMP-3B/GDF10) is regarded as a tumor growth inhibitor and a gene silenced in lung cancers; however the regulatory mechanisms leading to its silencing have not been identified. Here we show that Runx2 is highly expressed in lung cancer cells and downregulates BMP-3B. This inverse relationship between Runx2 and BMP-3B expression is further supported by increased expression of BMP-3B in mesenchymal cells from Runx2 deficient mice. The ectopic expression of Runx2, but not DNA binding mutant Runx2, in normal lung fibroblast cells and lung cancer cells resulted in suppression of BMP-3B levels. The chromatin immunoprecipitation studies identified that the mechanism of Runx2-mediated suppression of BMP-3B is due to the recruitment of Runx2 and histone H3K9-specific methyltransferase Suv39h1 to BMP-3B proximal promoter and a concomitant increase in histone methylation (H3K9) status. The knockdown of Runx2 in H1299 cells resulted in decreased histone H3K9 methylation on BMP-3B promoter and increased BMP-3B expression levels. Furthermore, co-immunoprecipitation studies showed a direct interaction of Runx2 and Suv39h1 proteins. Phenotypically, Runx2 overexpression in H1299 cells increased wound healing response to TGFβ treatment. Our studies identified BMP-3B as a new Runx2 target gene and revealed a novel function of Runx2 in silencing of BMP-3B in lung cancers. Our results suggest that Runx2 is a potential therapeutic target to block tumor suppressor gene silencing in lung cancer cells.
- [Show abstract] [Hide abstract] ABSTRACT: The osteogenic and oncogenic transcription factor RUNX2 downregulates the RNA polymerase I (RNA Pol I)-mediated transcription of rRNAs and changes histone modifications associated with the rDNA repeat. However, the mechanisms by which RUNX2 suppresses rRNA transcription are not well understood. RUNX2 cofactors such as histone deacetylases (HDACs) play a key role in chromatin remodeling and regulation of gene transcription. Here, we show that RUNX2 recruits HDAC1 to the rDNA repeats in osseous cells. This recruitment alters the histone modifications associated with active rRNA-encoding genes and causes deacetylation of the protein upstream binding factor (UBF, also known as UBTF). Downregulation of RUNX2 expression reduces the localization of HDAC1 to the nucleolar periphery and also decreases the association between HDAC1 and UBF. Functionally, depletion of HDAC1 relieves the RUNX2-mediated repression of rRNA-encoding genes and concomitantly increases cell proliferation and global protein synthesis in osseous cells. Our findings collectively identify a RUNX2-HDAC1-dependent mechanism for the regulation of rRNA-encoding genes and suggest that there is plasticity to RUNX2-mediated epigenetic control, which is mediated through selective mitotic exclusion of co-regulatory factors.
- [Show abstract] [Hide abstract] ABSTRACT: Nuclear microenvironments are architecturally organized subnuclear sites where the regulatory machinery for gene expression, replication, and repair resides. This compartmentalization is necessary to attain required stoichiometry for organization and assembly of regulatory complexes for combinatorial control. Combined and methodical application of molecular, cellular, biochemical, and in vivo genetic approaches is required to fully understand complexities of biological control. Here we provide methodologies to characterize nuclear organization of regulatory machinery by in situ immunofluorescence microscopy.
- [Show abstract] [Hide abstract] ABSTRACT: Epigenetic control of ribosomal RNA (rRNA) gene transcription by cell type-specific regulators, such as the osteogenic transcription factor Runx2, conveys cellular memory of growth and differentiation to progeny cells during mitosis. Here, we examined whether coregulatory proteins contribute to epigenetic functions that are mitotically transmitted by Runx2 in osteoblastic cells. We show that the transcriptional corepressor Transducin Like Enhancer-1 (TLE1) associates with rRNA genes during mitosis and interphase through interaction with Runx2. Mechanistically, depletion of TLE1 relieves Runx2-mediated repression of rRNA genes transcription and selectively increases histone modifications linked to active transcription. Biologically, loss of TLE-dependent rRNA gene repression coincides with increased global protein synthesis and enhanced cell proliferation. Our findings reinforce the epigenetic marking target genes by phenotypic transcription factors in mitosis and demonstrate a requirement for retention of coregulatory factors to sustain physiological control of gene expression during proliferation of lineage committed cells.
- [Show abstract] [Hide abstract] ABSTRACT: There is growing awareness that the fidelity of gene expression necessitates coordination of transcription factor metabolism and organization of genes and regulatory proteins within the three-dimensional context of nuclear architecture. The regulatory machinery that governs genetic and epigenetic control of gene expression is compartmentalized in nuclear microenvironments. Temporal and spatial parameters of regulatory complex organization and assembly are functionally linked to biological control and are compromised with the onset and progression of tumorigenesis. High throughput imaging of cells, tissues, and tumors, including live cell analysis, is expanding research's capabilities toward translating components of nuclear organization into novel strategies for cancer diagnosis and therapy.
- [Show abstract] [Hide abstract] ABSTRACT: Runx proteins are tissue-specific transcriptional scaffolds that organize and assemble regulatory complexes at strategic sites of target gene promoters and at intranuclear foci to govern activation or repression. During interphase, fidelity of intranuclear targeting supports the biological activity of Runx1 and Runx2 proteins. Both factors regulate genes involved in cell cycle control and cell growth (e.g., rRNA genes), as well as lineage commitment. Here, we have examined the subcellular regulatory properties of the third Runx member, the tumor suppressor protein Runx3, during interphase and mitosis. Using in situ cellular and biochemical approaches we delineated a subnuclear targeting signal that directs Runx3 to discrete transcriptional foci that are nuclear matrix associated. Chromatin immunoprecipitation results show that Runx3 occupies rRNA promoters during interphase. We also find that Runx3 remains associated with chromosomes during mitosis and localizes with nucleolar organizing regions (NORs), reflecting an interaction with epigenetic potential. Taken together, our study establishes that common mechanisms control the subnuclear distribution and activities of Runx1, Runx2, and Runx3 proteins to support RNA polymerase I and II mediated gene expression during interphase and mitosis.
Article: Transcription-factor-mediated epigenetic control of cell fate and lineage commitmentThis paper is one of a selection of papers published in this Special Issue, entitled CSBMCB’s 51st Annual Meeting – Epigenetics and Chromatin Dynamics, and has undergone the Journal’s usual peer review process.[Show abstract] [Hide abstract] ABSTRACT: Epigenetic control is required to maintain competency for the activation and suppression of genes during cell division. The association between regulatory proteins and target gene loci during mitosis is a parameter of the epigenetic control that sustains the transcriptional regulatory machinery that perpetuates gene-expression signatures in progeny cells. The mitotic retention of phenotypic regulatory factors with cell cycle, cell fate, and tissue-specific genes supports the coordinated control that governs the proliferation and differentiation of cell fate and lineage commitment.
- [Show abstract] [Hide abstract] ABSTRACT: The regulatory machinery that governs genetic and epigenetic control of gene expression is compartmentalized in nuclear microenvironments. Temporal and spatial parameters of regulatory complex organization and assembly are functionally linked to biological control and are compromised with the onset and progression of tumorigenesis providing a novel platform for cancer diagnosis and treatment.
- [Show abstract] [Hide abstract] ABSTRACT: Ribosomal RNA (rRNA) genes are down-regulated during osteogenesis, myogenesis, and adipogenesis, necessitating a mechanistic understanding of interrelationships between growth control and phenotype commitment. Here, we show that cell fate-determining factors [MyoD, myogenin (Mgn), Runx2, C/EBPbeta] occupy rDNA loci and suppress rRNA expression during lineage progression, concomitant with decreased rRNA expression and reciprocal loss of occupancy by c-Myc, a proliferation-specific activator of rRNA transcription. We find interaction of phenotypic factors with the polymerase I activator upstream binding factor UBF-1 at interphase nucleoli, and this interaction is epigenetically retained on mitotic chromosomes at nucleolar organizing regions. Ectopic expression and RNA interference establish that MyoD, Mgn, Runx2, and C/EBPbeta each functionally suppress rRNA genes and global protein synthesis. We conclude that epigenetic control of ribosomal biogenesis by lineage-specific differentiation factors is a general developmental mechanism for coordinate control of cell growth and phenotype.
- [Show abstract] [Hide abstract] ABSTRACT: Regulatory machinery for gene expression, replication, and repair are architecturally organized in nuclear microenvironments. This compartmentalization provides threshold concentrations of macromolecules for the organization and assembly of regulatory complexes for combinatorial control. A mechanistic under standing of biological control requires the combined application of molecular, cellular, biochemical, and in vivo genetic approaches. This chapter provides methodologies to characterize nuclear organization of regulatory machinery by in situ immunofluorescence microscopy.