Browsing by Author "Barajas, Sergio"

Now showing 1 - 7 of 7
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    Author Correction: Mutant p53 drives clonal hematopoiesis through modulating epigenetic pathway
    (Nature Publishing Group, 2020-07-28) Chen, Sisi; Wang, Qiang; Yu, Hao; Capitano, Maegan L.; Vemula, Sasidhar; Nabinger, Sarah C.; Gao, Rui; Yao, Chonghua; Kobayashi, Michihiro; Geng, Zhuangzhuang; Fahey, Aidan; Henley, Danielle; Liu, Stephen Z.; Barajas, Sergio; Cai, Wenjie; Wolf, Eric R.; Ramdas, Baskar; Cai, Zhigang; Gao, Hongyu; Luo, Na; Sun, Yang; Wong, Terrence N.; Link, Daniel C.; Liu, Yunlong; Boswell, H. Scott; Mayo, Lindsey D.; Huang, Gang; Kapur, Reuben; Yoder, Mervin C.; Broxmeyer, Hal E.; Gao, Zhonghua; Liu, Yan; Biochemistry and Molecular Biology, School of Medicine
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    Mutant p53 drives clonal hematopoiesis through modulating epigenetic pathway
    (Nature Research, 2019-12-11) Chen, Sisi; Wang, Qiang; Yu, Hao; Capitano, Maegan L.; Vemula, Sasidhar; Nabinger, Sarah C.; Gao, Rui; Yao, Chonghua; Kobayashi, Michihiro; Geng, Zhuangzhuang; Fahey, Aidan; Henley, Danielle; Liu, Stephen Z.; Barajas, Sergio; Sergio, Wenjie; Wolf, Eric R.; Ramdas, Baskar; Cai, Zhigang; Gao, Hongyu; Luo, Na; Sun, Yang; Wong, Terrence N.; Link, Daniel C.; Liu, Yunlong; Boswell, H. Scott; Mayo, Lindsey D.; Huang, Gang; Kapur, Reuben; Yoder, Mervin C.; Broxmeyer, Hal E.; Gao, Zhonghua; Liu, Yan; Biochemistry and Molecular Biology, School of Medicine
    Clonal hematopoiesis of indeterminate potential (CHIP) increases with age and is associated with increased risks of hematological malignancies. While TP53 mutations have been identified in CHIP, the molecular mechanisms by which mutant p53 promotes hematopoietic stem and progenitor cell (HSPC) expansion are largely unknown. Here we discover that mutant p53 confers a competitive advantage to HSPCs following transplantation and promotes HSPC expansion after radiation-induced stress. Mechanistically, mutant p53 interacts with EZH2 and enhances its association with the chromatin, thereby increasing the levels of H3K27me3 in genes regulating HSPC self-renewal and differentiation. Furthermore, genetic and pharmacological inhibition of EZH2 decreases the repopulating potential of p53 mutant HSPCs. Thus, we uncover an epigenetic mechanism by which mutant p53 drives clonal hematopoiesis. Our work will likely establish epigenetic regulator EZH2 as a novel therapeutic target for preventing CHIP progression and treating hematological malignancies with TP53 mutations.
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    Polycomb group protein Mel18 inhibits hematopoietic stem cell self-renewal through repressing the transcription of self-renewal and proliferation genes
    (Springer Nature, 2025) Cai, Wenjie; Liu, Xicheng; Barajas, Sergio; Xiao, Shiyu; Vemula, Sasidhar; Chen, Hongxia; Yang, Yuxia; Bochers, Christopher; Henley, Danielle; Liu, Sheng; Jia, Yuzhi; Hong, Michelle; Mays, Tiffany M.; Capitano, Maegan L.; Liu, Huiping; Ji, Peng; Gao, Zhonghua; Pasini, Diego; Wan, Jun; Yue, Feng; Platanias, Leonidas C.; Xi, Rongwen; Chen, Sisi; Liu, Yan; Biochemistry and Molecular Biology, School of Medicine
    Polycomb group (PcG) proteins play important roles in hematopoietic stem cell (HSC) self-renewal. Mel18 and Bmi1 are homologs of the PCGF subunit within the Polycomb repressive complex 1 (PRC1). Bmi1 (PCGF4) enhances HSC self-renewal and promotes terminal differentiation. However, the role of Mel18 (PCGF2) in hematopoiesis is not fully understood and how Mel18 regulates gene transcription in HSCs remains elusive. We found that acute deletion of Mel18 in the hematopoietic compartment significantly increased the frequency of functional HSCs in the bone marrow. Furthermore, we demonstrate that Mel18 inhibits HSC self-renewal and proliferation. RNA-seq studies revealed that HSC self-renewal and proliferation gene signatures are enriched in Mel18-/- hematopoietic stem and progenitors (HSPCs) compared to Mel18+/+ HSPCs. Notably, ATAC-seq revealed increased chromatin accessibility at genes important for HSC self-renewal, whereas CUT&RUN showed decreased enrichment of H2AK119ub1 at genes important for proliferation, leading to increased expression of both Hoxb4 and Cdk4 in Mel18-/- HSPCs. Thus, we demonstrate that Mel18 inhibits hematopoietic stem cell self-renewal through repressing the transcription of genes important for HSC self-renewal and proliferation.
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    PRL2 phosphatase enhances oncogenic FLT3 signaling via dephosphorylation of the E3 ubiquitin ligase CBL at tyrosine 371
    (American Society of Hematology, 2023) Chen, Hongxia; Bai, Yunpeng; Kobayashi, Michihiro; Xiao, Shiyu; Cai, Wenjie; Barajas, Sergio; Chen, Sisi; Miao, Jinmin; Nguele Meke, Frederick; Vemula, Sasidhar; Ropa, James P.; Croop, James M.; Boswell, H. Scott; Wan, Jun; Jia, Yuzhi; Liu, Huiping; Li, Loretta S.; Altman, Jessica K.; Eklund, Elizabeth A.; Ji, Peng; Tong, Wei; Band, Hamid; Huang, Danny T.; Platanias, Leonidas C.; Zhang, Zhong-Yin; Liu, Yan; Pediatrics, School of Medicine
    Acute myeloid leukemia (AML) is an aggressive blood cancer with poor prognosis. FMS-like tyrosine kinase receptor-3 (FLT3) is one of the major oncogenic receptor tyrosine kinases aberrantly activated in AML. Although protein tyrosine phosphatase PRL2 is highly expressed in some subtypes of AML compared with normal human hematopoietic stem and progenitor cells, the mechanisms by which PRL2 promotes leukemogenesis are largely unknown. We discovered that genetic and pharmacological inhibition of PRL2 significantly reduce the burden of FLT3-internal tandem duplications-driven leukemia and extend the survival of leukemic mice. Furthermore, we found that PRL2 enhances oncogenic FLT3 signaling in leukemia cells, promoting their proliferation and survival. Mechanistically, PRL2 dephosphorylates the E3 ubiquitin ligase CBL at tyrosine 371 and attenuates CBL-mediated ubiquitination and degradation of FLT3, leading to enhanced FLT3 signaling in leukemia cells. Thus, our study reveals that PRL2 enhances oncogenic FLT3 signaling in leukemia cells through dephosphorylation of CBL and will likely establish PRL2 as a novel druggable target for AML.
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    PRL2 Phosphatase Promotes Oncogenic KIT Signaling in Leukemia Cells through Modulating CBL Phosphorylation
    (American Association for Cancer Research, 2024) Chen, Hongxia; Bai, Yunpeng; Kobayashi, Michihiro; Xiao, Shiyu; Barajas, Sergio; Cai, Wenjie; Chen, Sisi; Miao, Jinmin; Meke, Frederick Nguele; Yao, Chonghua; Yang, Yuxia; Strube, Katherine; Satchivi, Odelia; Sun, Jianmin; Rönnstrand, Lars; Croop, James M.; Boswell, H. Scott; Jia, Yuzhi; Liu, Huiping; Li, Loretta S.; Altman, Jessica K.; Eklund, Elizabeth A.; Sukhanova, Madina; Ji, Peng; Tong, Wei; Band, Hamid; Huang, Danny T.; Platanias, Leonidas C.; Zhang, Zhong-Yin; Liu, Yan; Pediatrics, School of Medicine
    Receptor tyrosine kinase KIT is frequently activated in acute myeloid leukemia (AML). While high PRL2 (PTP4A2) expression is correlated with activation of SCF/KIT signaling in AML, the underlying mechanisms are not fully understood. We discovered that inhibition of PRL2 significantly reduces the burden of oncogenic KIT-driven leukemia and extends leukemic mice survival. PRL2 enhances oncogenic KIT signaling in leukemia cells, promoting their proliferation and survival. We found that PRL2 dephosphorylates CBL at tyrosine 371 and inhibits its activity toward KIT, leading to decreased KIT ubiquitination and enhanced AKT and ERK signaling in leukemia cells. Implications: Our studies uncover a novel mechanism that fine-tunes oncogenic KIT signaling in leukemia cells and will likely identify PRL2 as a novel therapeutic target in AML with KIT mutations.
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    Role of p53 in regulation of hematopoiesis in health and disease
    (Wolters Kluwer, 2022) Barajas, Sergio; Cai, Wenjie; Liu, Yan; Biochemistry and Molecular Biology, School of Medicine
    Purpose of review: Human aging is associated with an exponential increase in the occurrence of clonal hematopoiesis of indeterminate potential (CHIP). CHIP is associated with increased risks of de novo and therapy-related hematologic neoplasms and serves as a reservoir for leukemic relapse. Somatic mutations in the TP53 gene, which encodes the tumor suppressor protein p53, rank in the top five among genes that were mutated in CHIP. TP53 mutations in CHIP are associated with an increased incidence of myeloid neoplasms such as myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). This review focuses on mechanisms by which mutant p53 promotes CHIP progression and drives the pathogenesis of MDS and AML. We will also discuss potential therapeutic approaches that can target mutant p53 and improve treatment outcomes of MDS and AML. Recent findings: TP53 was frequently mutated in individuals with CHIP as well as in patients with MDS and AML. While clinical studies suggest that p53 mutant hematopoietic stem and progenitor cell expansion may predispose the elderly to hematologic neoplasms, the underlying mechanisms are not fully understood. Recent findings suggest that mutant p53 may utilize both cell autonomous and noncell autonomous mechanisms to promote CHIP development. Furthermore, we and others have demonstrated that several gain-of-function mutant p53 proteins have enhanced oncogenic potential beyond dominant-negative and loss-of-function effects. Notably, TP53 allelic state has important implications for genome stability, clinical presentation, and outcomes in MDS. Some small molecules reactivating wild-type p53 tumor suppressor activity show promising effects on some human MDS and AML cells with TP53 mutations in preclinical and early phases of clinical studies. Summary: TP53 mutations in MDS and AML are correlated with advanced disease, poor prognosis, reduced overall survival, and dismal outcomes. Deep understanding of the functions of mutant p53 proteins is essential to devise effective therapies for patients with myeloid neoplasms and other human cancers with TP53 mutations. Targeting mutant p53 directly or pathways regulated by mutant p53 holds great potential in preventing CHIP progression and treating MDS and AML patients with TP53 mutations.
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    The Role of Mutant P53 in the Pathogenesis of Myelodysplastic Syndromes
    (2025-05) Barajas, Sergio; Mayo, Lindsey; Liu, Yan; Dong, Charlie; Liu, Yunlong; Nakshatri, Harikrishna
    Human aging is associated with the development of clonal hematopoiesis of indeterminate potential (CHIP), which increases the risk of hematologic neoplasms such as myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). Somatic mutations in the tumor suppressor gene TP53 are found in 10-15% of MDS patients and are associated with poor prognosis and reduced survival. TP53 mutations promote clonal expansion and drive MDS pathogenesis during aging. However, extrinsic factors contributing to the progression of p53 mutant clonal hematopoiesis to MDS remain unknown. We discovered that chronic inflammation provides a competitive growth advantage to p53 mutant hematopoietic stem and progenitor cells (HSPCs) through activating the NLRP1 inflammasome, leading to increased secretion of pro-inflammatory cytokines such as IL-1β and IL-6 from p53 mutant HSPCs, thereby generating a pro-inflammatory microenvironment that negatively affects the fitness of wild-type HSPCs in a paracrine manner. Furthermore, we found that approximately 60% of p53R248W/+ mice develop MDS with age and exhibit elevated levels of IL-1β and IL-6 in their bone marrow (BM). Similarly, increased levels of IL-1β and IL-6 were observed in the BM of MDS or AML patients with TP53 mutations. Mechanistically, mutant p53 dysregulates pre-mRNA splicing in key regulators of the inflammatory response in HSPCs, such as IKBKE and USP15, leading to enhanced NF-κB activation and increased secretion of pro-inflammatory cytokines in the BM of middle-aged p53 mutant mice. Moreover, we discovered that TP53 and SRSF2 mutations cooperate in accelerating the development of hematologic malignancies, possibly through convergent effects on the NF-κB pathway. Thus, we demonstrate that chronic inflammation and aberrant pre-mRNA splicing contribute to the progression of p53 mutant clonal hematopoiesis to MDS. Notably, blocking IL-1β or inhibiting gasdermin D (GSDMD) maturation reduces the fitness of mutant p53 HSPCs, suggesting that IL-1β and GSDMD are potential therapeutic targets for TP53 mutated CHIP and myeloid neoplasms.