Browsing by Author "Ladaika, Christopher A."

Now showing 1 - 5 of 5
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    Activation of AKT induces EZH2-mediated β-catenin trimethylation in colorectal cancer
    (Elsevier, 2023-08-16) Ghobashi, Ahmed H.; Vuong, Truc T.; Kimani, Jane W.; Ladaika, Christopher A.; Hollenhorst, Peter C.; O’Hagan, Heather M.; Biochemistry and Molecular Biology, School of Medicine
    Colorectal cancer (CRC) develops in part through the deregulation of different signaling pathways, including activation of the WNT/β-catenin and PI3K/AKT pathways. Additionally, the lysine methyltransferase enhancer of zeste homologue 2 (EZH2) is commonly overexpressed in CRC. EZH2 canonically represses gene transcription by trimethylating lysine 27 of histone H3, but also has non-histone substrates. Here, we demonstrated that in CRC, active AKT phosphorylated EZH2 on serine 21. Phosphorylation of EZH2 by AKT induced EZH2 to interact with and methylate β-catenin at lysine 49, which increased β-catenin’s binding to the chromatin. Additionally, EZH2-mediated β-catenin trimethylation induced β-catenin to interact with TCF1 and RNA polymerase II and resulted in dramatic gains in genomic regions with β-catenin occupancy. EZH2 catalytic inhibition decreased stemness but increased migratory phenotypes of CRC cells with active AKT. Overall, we demonstrated that EZH2 modulates AKT-induced changes in gene expression through the AKT/EZH2/β-catenin axis in CRC.
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    LSD1 and aberrant DNA methylation mediate persistence of enteroendocrine progenitors that support BRAF mutant colorectal cancer
    (American Association for Cancer Research, 2021) Miller, Samuel A.; Policastro, Robert A.; Sriramkumar, Shruthi; Lai, Tim; Huntington, Thomas D.; Ladaika, Christopher A.; Kim, Daeho; Hao, Chunhai; Zentner, Gabriel E.; O’Hagan, Heather M.; Health Sciences, School of Health and Human Sciences
    Despite the connection of secretory cells, including goblet and enteroendocrine (EEC) cells, to distinct mucus-containing colorectal cancer histologic subtypes, their role in colorectal cancer progression has been underexplored. Here, our analysis of The Cancer Genome Atlas (TCGA) and single-cell RNA-sequencing data demonstrates that EEC progenitor cells are enriched in BRAF-mutant colorectal cancer patient tumors, cell lines, and patient-derived organoids. In BRAF-mutant colorectal cancer, EEC progenitors were blocked from differentiating further by DNA methylation and silencing of NEUROD1, a key gene required for differentiation of intermediate EECs. Mechanistically, secretory cells and the factors they secrete, such as trefoil factor 3, promoted colony formation and activation of cell survival pathways in the entire cell population. Lysine-specific demethylase 1 (LSD1) was identified as a critical regulator of secretory cell specification in vitro and in a colon orthotopic xenograft model, where LSD1 loss blocks formation of EEC progenitors and reduces tumor growth and metastasis. These findings reveal an important role for EEC progenitors in supporting colorectal cancer. SIGNIFICANCE: This study establishes enteroendocrine progenitors as a targetable population that promotes BRAF-mutant colorectal cancer and can be blocked by LSD1 inhibition to suppress tumor growth.
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    LSD1 inhibition attenuates targeted therapy-induced lineage plasticity in BRAF mutant colorectal cancer
    (Springer Nature, 2025-04-23) Ladaika, Christopher A.; Chakraborty, Averi; Masood, Ashiq; Hostetter, Galen; Yi, Joo Mi; O’Hagan, Heather M.; Medicine, School of Medicine
    Background: BRAF activating mutations occur in approximately 10% of metastatic colorectal cancer (CRCs) and are associated with worse prognosis in part due to an inferior response to standard chemotherapy. Standard of care for patients with refractory metastatic BRAFV600E CRC is treatment with BRAF and EGFR inhibitors and recent FDA approval was given to use these inhibitors in combination with chemotherapy for patients with treatment naïve metastatic BRAFV600E CRC. Lineage plasticity to neuroendocrine cancer is an emerging mechanism of targeted therapy resistance in several cancer types. Enteroendocrine cells (EECs), the neuroendocrine cell of the intestine, are uniquely present in BRAF mutant CRC as compared to BRAF wildtype CRC. Methods: BRAF plus EGFR inhibitor treatment induced changes in cell composition were determined by gene expression, imaging and single cell approaches in multiple models of BRAF mutant CRC. Furthermore, multiple clinically relevant inhibitors of the lysine demethylase LSD1 were tested to determine which inhibitor blocked the changes in cell composition. Results: Combined BRAF and EGFR inhibition enriched for EECs in all BRAF mutant CRC models tested. Additionally, EECs and other secretory cell types were enriched in a subset of BRAFV600E CRC patient samples following targeted therapy. Importantly, inhibition of LSD1 with a clinically relevant inhibitor attenuated targeted therapy-induced EEC enrichment through blocking the interaction of LSD1, CoREST2 and STAT3. Conclusions: Our findings that BRAF plus EGFR inhibition induces lineage plasticity in BRAFV600E CRC represents a new paradigm for how resistance to BRAF plus EGFR inhibition occurs. Additionally, our finding that LSD1 inhibition blocks lineage plasticity has the potential to improve responses to BRAF plus EGFR inhibitor therapy in patients.
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    PTEN depletion reduces H3K27me3 levels to promote epithelial-to-mesenchymal transition in epithelial colorectal cancer cells
    (Public Library of Science, 2024-11-19) Ghobashi, Ahmed H.; Kimani, Jane W.; Ladaika, Christopher A.; O’Hagan, Heather M.; Medical and Molecular Genetics, School of Medicine
    Epithelial-to-mesenchymal (EMT) transition is one of the best-known examples of tumor cell plasticity. EMT enhances cancer cell metastasis, which is the main cause of colorectal cancer (CRC)-related mortality. Therefore, understanding underlying molecular mechanisms contributing to the EMT process is crucial to finding druggable targets and more effective therapeutic approaches in CRC. In this study, we demonstrated that phosphatase and tensin homolog (PTEN) knockdown (KD) induces EMT in epithelial CRC, likely through the activation of AKT. PTEN KD modulated chromatin accessibility and reprogrammed gene transcription to mediate EMT in epithelial CRC cells. Active AKT can phosphorylate enhancer of zeste homolog 2 (EZH2) on serine 21, which switches EZH2 from a transcriptional repressor to an activator. Interestingly, PTEN KD reduced the global levels of trimethylation of histone 3 at lysine 27(H3K27me3) in an EZH2-phosphorylation-dependent manner. Additionally, EZH2 phosphorylation at serine 21 reduced the interaction of EZH2 with another polycomb repressive complex 2 (PRC2) component, suppressor of zeste 12 (SUZ12), suggesting that the reduced H3K27me3 levels in PTEN KD cells were due to a disruption of the PRC2 complex. Overall, we demonstrated that PTEN KD modulates changes in gene expression to induce the EMT process in epithelial CRC cells by phosphorylating EZH2 and activates transcription factors such as activator protein 1 (AP1).
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    Single-Cell Profiling Reveals the Impact of Genetic Alterations on the Differentiation of Inflammation-Induced Murine Colon Tumors
    (MDPI, 2024-05-28) Ghobashi, Ahmed H.; Lanzloth, Rosie; Ladaika, Christopher A.; Masood, Ashiq; O’Hagan, Heather M.; Medicine, School of Medicine
    Genetic mutations and chronic inflammation of the colon contribute to the development of colorectal cancer (CRC). Using a murine model of inflammation-induced colon tumorigenesis, we determined how genetic mutations alter colon tumor cell differentiation. Inflammation induced by enterotoxigenic Bacteroides fragilis (ETBF) colonization of multiple intestinal neoplasia (MinApcΔ716/+) mice triggers loss of heterozygosity of Apc causing colon tumor formation. Here, we report that the addition of BRAFV600E mutation (BRAFF-V600ELgr5tm1(Cre/ERT2)CleMinApcΔ716/+, BLM) or knocking out Msh2 (Msh2LoxP/LoxPVil1-creMinApcΔ716/+, MSH2KO) in the Min model altered colon tumor differentiation. Using single-cell RNA sequencing, we uncovered the differences between BLM, Min, and MSH2KO tumors at a single-cell resolution. BLM tumors showed an increase in differentiated tumor epithelial cell lineages and a reduction in the tumor stem cell population. Interestingly, the tumor stem cell population of BLM tumors had revival colon stem cell characteristics with low WNT signaling and an increase in RevCSC marker gene expression. In contrast, MSH2KO tumors were characterized by an increased tumor stem cell population that had higher WNT signaling activity compared to Min tumors. Furthermore, overall BLM tumors had higher expression of transcription factors that drive differentiation, such as Cdx2, than Min tumors. Using RNA velocity, we identified additional potential regulators of BLM tumor differentiation such as NDRG1. The role of CDX2 and NDRG1 as putative regulators for BLM tumor cell differentiation was verified using organoids derived from BLM tumors. Our results demonstrate the critical connections between genetic mutations and cell differentiation in inflammation-induced colon tumorigenesis. Understanding such roles will deepen our understanding of inflammation-associated colon cancer.