IU Indianapolis ScholarWorks :: Browsing by Subject "Proto-oncogene proteins"

Browsing by Subject "Proto-oncogene proteins"

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Akt Phosphorylates the Transcriptional Repressor Bmi1 to Block Its Effects on the Tumor-Suppressing Ink4a-Arf Locus
(American Association for the Advancement of Science, 2012-10-23) Liu, Yan; Liu, Fan; Yu, Hao; Zhao, Xinyang; Sashida, Goro; Deblasio, Anthony; Harr, Michael; She, Qing-Bai; Chen, Zhenbang; Lin, Hui-Kuan; Di Giandomenico, Silvana; Elf, Shannon E.; Yang, Youyang; Miyata, Yasuhiko; Huang, Gang; Menendez, Silvia; Mellinghoff, Ingo K.; Rosen, Neal; Pandolfi, Pier Paolo; Hedvat, Cyrus V.; Nimer, Stephen D.; Pediatrics, School of Medicine
The Polycomb group protein Bmi1 is a transcriptional silencer of the Ink4a-Arf locus, which encodes the cell cycle regulator p16(Ink4a) and the tumor suppressor p19(Arf). Bmi1 plays a key role in oncogenesis and stem cell self-renewal. We report that phosphorylation of human Bmi1 at Ser³¹⁶ by Akt impaired its function by triggering its dissociation from the Ink4a-Arf locus, which resulted in decreased ubiquitylation of histone H2A and the inability of Bmi1 to promote cellular proliferation and tumor growth. Moreover, Akt-mediated phosphorylation of Bmi1 also inhibited its ability to promote self-renewal of hematopoietic stem and progenitor cells. Our study provides a mechanism for the increased abundance of p16(Ink4a) and p19(Arf) seen in cancer cells with an activated phosphoinositide 3-kinase to Akt signaling pathway and identifies crosstalk between phosphorylation events and chromatin structure.
Chloroquine Promotes Apoptosis in Melanoma Cells by Inhibiting BH3 domain Mediated PUMA Degradation
(Elsevier, 2013) Lakhter, Alexander J.; Sahu, Ravi P.; Sun, Yang; Kaufmann, William K.; Androphy, Elliot J.; Travers, Jeffrey B.; Naidu, Samisubbu R.; Dermatology, School of Medicine
The Bcl homology-3 (BH3)-only protein p53 upregulated modulator of apoptosis (PUMA) counters Bcl-2 family anti-apoptotic proteins and promotes apoptosis. Although PUMA is a key regulator of apoptosis, the post-transcriptional mechanisms that control PUMA protein stability are not understood. We show that a lysosome-independent activity of chloroquine (CQ) prevents degradation of PUMA protein, promotes apoptosis, and reduces the growth of melanoma xenografts in mice. Compared with wild-type PUMA, a BH3 domain-deleted PUMA protein showed impaired decay in melanoma cells. Fusion of the BH3 domain to a heterologous protein led to its rapid turnover that was inhibited by CQ. Although both CQ and inhibitors of lysosomal proteases stalled autophagy, only CQ stabilized PUMA protein and promoted apoptosis. Our results reveal a lysosomal protease-independent activity of CQ that selectively promotes apoptosis in melanoma cells.
Complement component C1q regulates macrophage expression of Mer tyrosine kinase to promote clearance of apoptotic cells
(Oxford University Press, 2012) Galvan, Manuel D.; Foreman, Deborah B.; Zeng, Erliang; Tan, John C.; Bohlson, Suzanne S.; Microbiology and Immunology, School of Medicine
Failure to efficiently clear apoptotic cells is linked to defects in development and the onset of autoimmunity. Complement component C1q is required for efficient engulfment of apoptotic cells in mice and humans; however, the molecular mechanisms leading to C1q-dependent engulfment are not fully understood. In this study, we used primary mouse macrophages to identify and characterize a novel molecular mechanism for macrophage-mediated C1q-dependent engulfment of apoptotic cells. We found that macrophage activation with C1q resulted in cycloheximide-sensitive enhanced engulfment, indicating a requirement for de novo protein synthesis. To investigate the cycloheximide-sensitive pathway, C1q-elicited macrophage transcripts were identified by microarray. C1q triggered the expression of Mer tyrosine kinase (Mer) and the Mer ligand growth arrest-specific 6: a receptor-ligand pair that mediates clearance of apoptotic cells. Full-length native C1q, and not the collagen-like tail or heat-denatured protein, stimulated Mer expression. This novel pathway is specific to C1q because mannose-binding lectin, a related collectin, failed to upregulate Mer expression and function. Soluble Mer-Fc fusion protein inhibited C1q-dependent engulfment of apoptotic cells, indicating a requirement for Mer. Moreover, Mer-deficient macrophages failed to respond to C1q with enhanced engulfment. Our results suggest that C1q elicits a macrophage phenotype specifically tailored for apoptotic cell clearance, and these data are consistent with the established requirement for C1q in prevention of autoimmunity.
Development and evaluation of ActSeq: A targeted next-generation sequencing panel for clinical oncology use
(PLOS, 2022-04-21) Shi, Zonggao; Lopez, Jacqueline; Kalliney, William; Sutton, Bobbie; Simpson, Joyce; Maggert, Kevin; Liu, Sheng; Wan, Jun; Stack, M. Sharon; Medical and Molecular Genetics, School of Medicine
Purpose: The demand for high-throughput genetic profiling of somatic mutations in cancer tissues is growing. We sought to establish a targeted next generation sequencing (NGS) panel test for clinical oncology practice. Methods: Customized probes were designed to capture exonic regions of 141 genes selected for the panel, which was aimed for the detection of clinically actionable genetic variations in cancer, including KRAS, NRAS, BRAF, ALK, ROS1, KIT and EGFR. The size of entire targeted regions is 0.8 Mb. Library preparation used NEBNext Ultra II FS kit coupled with target enrichment. Paired-end sequencing was run on Illumina NextSeq 500 at a read length of 150 nt. A bioinformatics workflow focusing on single nucleotide variant and short insertions and deletions (SNV/indel) discovery was established using open source, in-house and commercial software tools. Standard reference DNA samples were used in testing the sensitivity and precision and limit of detection in variant calling. Results: The general performance of the panel was observed in pilot runs. Average total reads per sample ranged from 30 million to 48 million, 73% ~82% unique reads. All runs had more than 99% average mapping rate. Mean target coverage ranged from 727x to 879x. Depth of coverage at 50x or more reached 87% of targeted region and 60% of targeted region received 500x or more coverage depth. Using OncoSpan HD827 DNA, which bears 144 variants (SNV/indel) from 80 genes that are within the targeted region on the panel, our somatic variant calling pipeline reached 97% sensitivity and 100% precision respectively, with near 48 million reads. High concordance with orthogonal approaches in variant detection was further verified with 7 cancer cell lines and 45 clinical specimens. Conclusion: We developed a NGS panel with a focus on clinically actionable gene mutations and validated the performance in library construction, sequencing and variant calling. High concordance with reference materials and orthogonal mutation detection was observed.
Gcn5 is required for PU.1-dependent Interleukin-9 (IL-9) induction in Th9 cells
(Oxford University Press, 2012) Goswami, Ritobrata; Kaplan, Mark H.; Pediatrics, School of Medicine
Naive CD4+ T cells differentiate into various effector Th subsets depending on the Ags and cytokine microenvironment they encounter. IL-9-secreting Th9 cells are the most recent Th subset to be described. PU.1, one of the transcription factors required for the development of Th9 cells, binds to the Il9 gene. In this study, we show that PU.1 increases histone acetylation at the Il9 locus through direct interactions with histone acetyltransferases. In the absence of PU.1, there is decreased association of Gcn5 and p300/CBP associated factor and increased association of histone deacetylases at the Il9 locus in Th9 cells. Inhibition of histone deacetylase activity augments PU.1-dependent IL-9 production. PU.1 forms a complex with Gcn5, and inhibition of the expression of Gcn5 results in reduced IL-9 production. Moreover, the effects of Gcn5 on IL-9 production are specific as the production of IL-10 and IL-21, two additional cytokines produced by Th9 cells, is not altered after decreased Gcn5 expression. Together, these data define a PU.1-dependent mechanism for altered histone acetylation and expression of the Il9 locus in Th9 cells.
Macrophage dectin-1 expression is controlled by leukotriene B4 via a GM-CSF/PU.1 axis
(Oxford University Press, 2012) Serezani, C. Henrique; Kane, Steve; Collins, Latima; Morato-Marques, Mariana; Osterholzer, John J.; Peters-Golden, Marc; Microbiology and Immunology, School of Medicine
Pattern recognition receptors for fungi include dectin-1 and mannose receptor, and these mediate phagocytosis, as well as production of cytokines, reactive oxygen species, and the lipid mediator leukotriene B(4) (LTB(4)). The influence of G protein-coupled receptor ligands such as LTB(4) on fungal pattern recognition receptor expression is unknown. In this study, we investigated the role of LTB(4) signaling in dectin-1 expression and responsiveness in macrophages. Genetic and pharmacologic approaches showed that LTB(4) production and signaling through its high-affinity G protein-coupled receptor leukotriene B(4) receptor 1 (BLT1) direct dectin-1-dependent binding, ingestion, and cytokine production both in vitro and in vivo. Impaired responses to fungal glucans correlated with lower dectin-1 expression in macrophages from leukotriene (LT)- and BLT1-deficent mice than their wild-type counterparts. LTB(4) increased the expression of the transcription factor responsible for dectin-1 expression, PU.1, and PU.1 small interfering RNA abolished LTB(4)-enhanced dectin-1 expression. GM-CSF controls PU.1 expression, and this cytokine was decreased in LT-deficient macrophages. Addition of GM-CSF to LT-deficient cells restored expression of dectin-1 and PU.1, as well as dectin-1 responsiveness. In addition, LTB(4) effects on dectin-1, PU.1, and cytokine production were blunted in GM-CSF(-/-) macrophages. Our results identify LTB(4)-BLT1 signaling as an unrecognized controller of dectin-1 transcription via GM-CSF and PU.1 that is required for fungi-protective host responses.
MYC and HSF1 Cooperate to Drive Sensitivity to Polo-like Kinase 1 Inhibitor Volasertib in High-grade Serous Ovarian Cancer
(American Association for Cancer Research, 2025) Williams, Imade; O’Malley, Matthew; DeHart, Haddie; Walker, Bobby; Ulhaskumar, Vrushabh; Jothirajah, Pranav; Ray, Haimanti; Landrum, Lisa M.; Delaney, Joe R.; Nephew, Kenneth P.; Carpenter, Richard L.; Obstetrics and Gynecology, School of Medicine
We show that HSF1 and MYC genes are co-amplified in more than 30% of HGSOC and demonstrate that HSF1 and MYC functionally cooperate to drive the growth of HGSOC cells. This work provides the foundation for HSF1 and MYC co-amplification as a biomarker for treatment efficacy of the polo-like kinase 1 inhibitor volasertib in HGSOC.
PLK1 Inhibition Induces Synthetic Lethality in Fanconi Anemia Pathway-Deficient Acute Myeloid Leukemia
(American Association for Cancer Research, 2025) Sheth, Aditya S.; Chan, Ka-Kui; Liu, Sheng; Wan, Jun; Angus, Steve P.; Rhodes, Steven D.; Mitchell, Dana K.; Davis, Christopher; Ridinger, Maya; Croucher, Peter J.; Zeidan, Amer M.; Wijeratne, Aruna; Qian, Shaomin; Tran, Ngoc Tung; Sierra Potchanant, Elizabeth A.; Pediatrics, School of Medicine
This work demonstrates that FA pathway mutations, which are frequently observed in sporadic AML, induce hypersensitivity to PLK1 inhibition, providing rationale for a novel synthetic lethal therapeutic strategy for this patient population.
Quantitative phosphoproteomic analysis identifies novel functional pathways of tumor suppressor DLC1 in estrogen receptor positive breast cancer.
(PLOS, 2018-10-02) Gökmen-Polar, Yesim; True, Jason D.; Vieth, Edyta; Gu, Yuan; Gu, Xiaoping; Qi, Guihong D.; Mosley, Amber L.; Badve, Sunil S.; Pathology and Laboratory Medicine, School of Medicine
Deleted in Liver Cancer-1 (DLC1), a member of the RhoGAP family of proteins, functions as a tumor suppressor in several cancers including breast cancer. However, its clinical relevance is unclear in breast cancer. In this study, expression of DLC1 was correlated with prognosis using publicly available breast cancer gene expression datasets and quantitative Reverse Transcription PCR in cohorts of Estrogen Receptor-positive (ER+) breast cancer. Low expression of DLC1 correlates with poor prognosis in patients with ER+ breast cancer with further decrease in metastatic lesions. The Cancer Genome Atlas (TCGA) data showed that down regulation of DLC1 is not due to methylation or mutations. To seek further insights in understanding the role of DLC1 in ER+ breast cancer, we stably overexpressed DLC1-full-length (DLC1-FL) in T-47D breast cancer cells; this inhibited cell colony formation significantly in vitro compared to its control counterpart. Label-free global proteomic and TiO2 phosphopeptide enrichment assays (ProteomeXchange identifier PXD008220) showed that 205 and 122 phosphopeptides were unique to DLC1-FL cells and T-47D-control cells, respectively, whereas 6,726 were quantified by phosphoproteomics analysis in both conditions. The top three significant clusters of differentially phosphopeptides identified by DAVID pathway analysis represent cell-cell adhesion, mRNA processing and splicing, and transcription regulation. Phosphoproteomics analysis documented an inverse relation between DLC1 expression and several phosphopeptides including epithelial cell transforming sequence 2 (ECT2). Decreased phosphorylation of ECT2 at the residue T359, critical for its active conformational change, was validated by western blot. In addition, the ECT2 T359-containing phosphopeptide was detected in both basal and luminal patient-derived breast cancers breast cancer phosphoproteomics data on the Clinical Proteomic Tumor Analysis Consortium (CPTAC) Assay portal. Together, for the first time, this implicates ECT2 phosphorylation in breast cancer, which has been proposed as a therapeutic target in lung cancer. In conclusion, this data suggests that low expression of DLC1 is associated with poor prognosis. Targeting ECT2 phosphopeptides could provide a promising mechanism for controlling poor prognosis seen in DLC1low ER+ breast cancer.
STAT6-dependent regulation of Th9 development
(Oxford University Press, 2012) Goswami, Ritobrata; Jabeen, Rukhsana; Yagi, Ryoji; Pham, Duy; Zhu, Jinfang; Goenka, Shreevrat; Kaplan, Mark H.; Pediatrics, School of Medicine
Th cell effector subsets develop in response to specific cytokine environments. The development of a particular cytokine-secreting pattern requires an integration of signals that may promote the development of opposing pathways. A recent example of this paradigm is the IL-9-secreting Th9 cell that develops in response to TGF-β and IL-4, cytokines that, in isolation, promote the development of inducible regulatory T cells and Th2 cells, respectively. To determine how the balance of these factors results in priming for IL-9 secretion, we examined the effects of each pathway on transcription factors that regulate Th cell differentiation. We demonstrated that TGF-β induces the PU.1-encoding Sfpi1 locus and that this is independent of IL-4-induced STAT6 activation. IL-4-activated STAT6 is required for repressing the expression of T-bet and Foxp3 in Th9 cells, transcription factors that inhibit IL-9 production, and STAT6 is required for the induction of IRF4, which promotes Th9 development. These data established a transcription factor network that regulates IL-9 and demonstrated how combinations of cytokine signals generate cytokine-secreting potential by altering the expression of a panel of transcription factors.

Browsing by Subject "Proto-oncogene proteins"

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