Blood Cancer Discovery最新文献

{"title":"Abstract A45: UBTF-TD molecular alterations drive leukemogenesis in pediatric AML by directly interacting and regulating the HOXB gene locus","authors":"Juan M. Barajas, Masayuki Umeda, Ryan Hiltenbrand, Reethu Krishnan, Tamara Westover, Michael P. Walsh, Jing Ma, Sherif Abdelhamed, J. Klco","doi":"10.1158/2643-3249.aml23-a45","DOIUrl":"https://doi.org/10.1158/2643-3249.aml23-a45","url":null,"abstract":"\u0000 Pediatric acute myeloid leukemia (AML) is often refractory to chemotherapy and remains a devastating disease with poor outcomes. Consequently, there is an urgent need to characterize molecular drivers of pediatric AML with the goal of developing more effective molecular therapies. Our group recently identified somatic tandem duplications (TD) in exon 13 of upstream binding transcription factor (UBTF) as a subtype-defining genomic alteration in pediatric AML that is associated with poor outcomes, high relapse rate, and measurable residual disease (MRD) positivity. However, how these alterations drive leukemogenesis is yet to be investigated. Wild-type UBTF regulates rRNA transcription, ribosome biogenesis, and nucleolar formation. Our recent work suggests that UBTF-TD retains these functions. However, we found that expression of UBTF-TD in cord blood CD34+ cells, but not wild-type UBTF, leads to their increased proliferation, self-renewal, and CD117/CD33 surface marker expression, suggesting a potential gain of function as well. Furthermore, we also observed increased expression of HOXB locus genes, PRDM16, MEIS1, and NKX2-3 in the CD34+ UBTF-TD overexpression model relative to our WT control. These expression patterns are similar to what we see in patients, collectively implicating UBTF-TD driving leukemic phenotypes. Based on our localization studies of UBTF-TD to DNA, we hypothesized that UBTF-TD protein may gain the ability to interact with genomic loci that characterize UBTF-TD AML, like the HOXB locus. We therefore wanted to test if UBTF-TD localized to the HOXB cluster and if this lead direct transcriptional upregulation. To test this, we expressed HA-tagged UBTF-TD in cord-blood CD34+ cells and mapped UBTF-TD genomic occupancy using CUT&RUN. We found that UBTF-TD localized to the promoters and gene bodies of key genes, including PRDM16, MEIS1, NKX2-3, and the HOXB cluster. These sites were accompanied by H3K4me3 and H3K27ac active marks without the H3K27me3 repressive mark. To validate these as bone-fide UBTF-TD-occupied regions, we utilized a expressed FKBP12F36V-HA-UBTF-TD fusion in CD34+ cells. This degradation tag (dTAG) system allows for rapid degradation of UBTF-TD protein upon dTAG-13 treatment. We treated our FKBP12F36V-HA-UBTF-TD expressing cord blood CD34+ cells with 1uM of dTAG-13 or DMSO. We found that a 3-day treatment with dTAG-13 led to downregulation of HOXB gene locus expression, but loss of CD117 expression or cell growth required prolonged treatment. Furthermore, our CUT&RUN data showed that dTAG-13 treatment resulted in loss of UBTF-TD protein at the HOXB gene cluster. Collectively, these data show that UBTF-TD interacts with genomic loci at the HOXB gene cluster to directly upregulate their expression. This loss of HOX gene expression leads then leads to loss of a leukemic phenotype. Our data highlights a potential mechanism for UBTF-TD leukemogenesis and sets a foundation where inhibiting the UBTF-TD molecular signa","PeriodicalId":29944,"journal":{"name":"Blood Cancer Discovery","volume":" ","pages":""},"PeriodicalIF":11.2,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45460560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A20: Inflammation remodels the immune microenvironment in acute myeloid leukemia","authors":"Audrey Lasry, B. Nadorp, M. Fornerod, D. Nicolet, Huiyun Wu, C. Walker, Zhengxi Sun, Matthew T. Witkowski, Anastasia N. Tikhonova, Maria Guillamot, Geraldine Cayanan, Anna H. Yeaton, T. Gruber, Ann-Kathrin Eisfeld, I. Aifantis","doi":"10.1158/2643-3249.aml23-a20","DOIUrl":"https://doi.org/10.1158/2643-3249.aml23-a20","url":null,"abstract":"\u0000 Acute myeloid leukemia (AML) is a hematopoietic malignancy with poor prognosis and limited treatment options. Here we provide a comprehensive single cell RNA-Sequencing census of the bone marrow immune microenvironment in adult and pediatric AML patients. We characterize unique inflammation signatures in a subset of AML patients, associated with inferior outcomes. We identify atypical B cells, a dysfunctional B cell subtype enriched in high-inflammation AML patients, as well as an increase in CD8+ GZMK+ and regulatory T cells, accompanied by a reduction in T cell clonal expansion. We derive an inflammation-associated gene score (iScore) that associates with poor survival outcomes in AML patients. Addition of the iScore refines current risk stratifications for AML patients and may enable identification of patients in need of more aggressive treatment. This work provides a first framework for classifying AML patients based on their immune microenvironment and a rationale for consideration of the inflammatory state in clinical settings.\u0000 Citation Format: Audrey Lasry, Bettina Nadorp, Maarten Fornerod, Deedra Nicolet, Huiyun Wu, Christopher J Walker, Zhengxi Sun, Matthew T Witkowski, Anastasia N Tikhonova, Maria Guillamot, Geraldine Cayanan, Anna Yeaton, Tanja A Gruber, Ann-Kathrin Eisfeld, Iannis Aifantis. Inflammation remodels the immune microenvironment in acute myeloid leukemia [abstract]. In: Proceedings of the AACR Special Conference: Acute Myeloid Leukemia and Myelodysplastic Syndrome; 2023 Jan 23-25; Austin, TX. Philadelphia (PA): AACR; Blood Cancer Discov 2023;4(3_Suppl):Abstract nr A20.","PeriodicalId":29944,"journal":{"name":"Blood Cancer Discovery","volume":" ","pages":""},"PeriodicalIF":11.2,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46672268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A30: Activation of GCN2 by HC-7366 results in significant anti-tumor efficacy as monotherapy and in combination with Venetoclax in AML models","authors":"Feven Tameire, P. Wojnarowicz, S. Fujisawa, Sharon Huang, O. Reilly, C. Dudgeon, Nick Collette, J. Drees, Kathryn T. Bieging-Rolett, Takashi O. Kangas, Weiyu Zhang, M. Fumagalli, Iman Dewji, Yunfang Li, Anissa S. H. Chan, Xiaohong X. Qiu, B. Harrison, Ashley LaCayo, K. Staschke, A. C. Rigby, S. Ramurthy, E. Lightcap, D. Surguladze, N. Bose","doi":"10.1158/2643-3249.aml23-a30","DOIUrl":"https://doi.org/10.1158/2643-3249.aml23-a30","url":null,"abstract":"\u0000 The integrated stress response (ISR) is an adaptive signaling pathway that cells utilize to respond to a wide range of extrinsic and intrinsic stresses, many of which are important for tumorigenesis. Activation of ISR plays a dual role in cell fate decisions; while the ISR promotes survival, prolonged activation of ISR induces apoptosis. Activation of General Control Nonderepressible 2 (GCN2), an ISR kinase that senses and responds to nutrient stress conditions results in anti-tumor activity. We are developing HC-7366, a first-in-class, first-in-human GCN2 activator, and are currently evaluating it in a phase 1 clinical trial in solid tumors (NCT05121948). Here we present a series of studies characterizing the antitumor effects of HC-7366 in acute myeloid leukemia (AML). Higher expression of GCN2 and ISR markers such as ATF4 has been observed in primitive or minimally differentiated AML cells, suggesting that AML may be particularly sensitive to HC-7366. Encouragingly, in vivo efficacy studies in MOLM-16 and KG-1 tumor models showed 100% complete response and 100% tumor growth inhibition, respectively. Analysis of tumors from treated mice by IHC demonstrated activation of ISR as evidenced by increased expression of the ATF4 targets, ASNS and PSAT1, confirming that HC-7366 is functioning as a GCN2 activator in vivo. In the MV4-11 model, a differentiated subtype of AML that shows limited response to venetoclax, the combination of HC-7366 and venetoclax produced strong benefit resulting in 26% tumor regression. Enhanced activation of ISR pathway was again observed when HC-7366 was combined with venetoclax. HC-7366 treatment also impacted possible venetoclax resistance mechanisms by increasing the levels of PUMA while reducing levels of S100A8/A9 proteins. To investigate the effects of the compound on primary AML, we performed an ex vivo screen using cells from AML patients and treatment with HC-7366 showed a remarkable decrease in cell proliferation. Furthermore, in a xenotransplantable model of patient-derived AML, we found that HC-7366 significantly reduced mature myeloid (CD33+) AML cells in the bone marrow as compared to standard of care (SOC) agents, including venetoclax. We confirmed that activation of ISR, reduction in cell viability, and inhibition of protein synthesis following treatment with HC-7366 was dependent on GCN2 using CRISPR knockout cells. In addition, HC-7366 reduced mitochondrial respiration in MOLM-16 cells, suggesting effects on cellular bioenergetics. Metabolomics analyses of AML xenograft tumors showed that HC-7366 significantly altered metabolites associated with amino acid metabolism, urea cycle, and oxidative stress. Together, our in vitro and in vivo results demonstrate that HC-7366 is a potent GCN2 activator with strong antitumor activity in AML as a single agent and in combination with venetoclax, supporting its investigation in clinical trials in patients with AML.\u0000 Citation Format: Feven Tameire, Paulina M. Wojnar","PeriodicalId":29944,"journal":{"name":"Blood Cancer Discovery","volume":" ","pages":""},"PeriodicalIF":11.2,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47780604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A08: Targeting HSP90 epichaperome in TP53 mutant AML","authors":"B. Carter, Poo Yee Mak, W. Tao, Lauren B Ostermann, Yuki Nishida, S. Boettcher, M. Andreeff","doi":"10.1158/2643-3249.aml23-a08","DOIUrl":"https://doi.org/10.1158/2643-3249.aml23-a08","url":null,"abstract":"\u0000 The Bcl-2 inhibitor venetoclax (VEN)/hypomethylation agent (HMA) combination achieves high response rates, has improved outcomes for many patients with AML and is now considered standard of care for patients who are older or unfit to receive intensive chemotherapy. However, the median overall survival is only 14.7 months on this regimen and only 2.5 months post relapse. Molecular analysis demonstrates that mutations in TP53 and oncogenic kinases are key determinants of lower response rates and early relapse. Preclinical studies also show that increased kinase signaling in AML stem/progenitor cells in TP53 mutant AML. The heat shock protein 90 (HSP90) chaperone, a key regulator of proteostasis, is responsible for the correct folding of kinases and transcription factors. HSP90-associated-epichaperomes, formed in malignant cells, are complexes consisting of HSP90, co-chaperones, and associated proteins that support the maturation, activity, and stability of many cancer-associated kinases and transcription factors including mutated TP53. Hence, HSP90 epichaperome inhibition has the potential of targeting TP53 mutant AML. In contrast to other HSP90 ATP inhibitors, PU-H71 (zelavespib) is a competitive inhibitor specific for the ATP binding site of HSP90 epichaperomes. We here investigate the therapeutic potentials of targeting HSP90 epitherachorme with PU-H71 in TP53 mutated AML. Western blot analysis found increased HSP90 and several signaling proteins in TP53 knockout and mutant Molm13 cells generated by CRISPR/cas-9 or by exposing to idasanutlin, compared to the isogeneic wild-type controls. Using a fluorochrome-labelled PU-H71 and flow cytometry, we demonstrate the presence of HSP90 epichaperomes in AML cells and AML stem/progenitor cells with TP53 mutations, but not in normal bone marrow and bone marrow stem/progenitor cells. PU-H71 effectively kills AML cells and AML stem/progenitor cells with various TP53 mutations, and prolongs survival in TP53-mutant AML xenograft mice with minimal effects on normal CD34+ bone marrow cells and hematopoiesis. PU-H71 increased Bim expression and enhanced VEN activity in AML cells and AML stem/progenitor cells with TP53 mutations. Importantly, in a mixture of TP53 wild-type/R248W Molm13 cells (1000:1), nutlin3a selectively killed TP53 wild-type but enriched TP53 mutant Molm13 cells; VEN treatment favored the outgrowth of TP53-mutant cells, while PU-H71 effectively killed TP53 wild-type and mutant cells. Furthermore, PU-H71 exhibited anti-leukemia activity against both TP53 WT and mutant AML cells, which was further enhanced by VEN in vivo in a xenograft model of mixed TP53 WT and mutated Molm13 cells (10:1). Our data support that the HSP90 epichaperome is essential for the growth and survival of AML and AML stem/progenitor cells harboring mutant TP53. Inhibition of HSP90 by PU-H71 targets AML cells/stem/progenitor cells enhances VEN activity and prevents outgrowth of VEN-resistant TP53 mutant AML cells. This co","PeriodicalId":29944,"journal":{"name":"Blood Cancer Discovery","volume":" ","pages":""},"PeriodicalIF":11.2,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43076389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A05: Multiplexed CyTOF analysis of FLT3-ITD AML landscape identifies proteomic profiles associated with resistance to targeted therapies","authors":"M. Muftuoglu, M. Yilmaz, Mahesh Basyal, Li Li, N. Daver, M. Andreeff","doi":"10.1158/2643-3249.aml23-a05","DOIUrl":"https://doi.org/10.1158/2643-3249.aml23-a05","url":null,"abstract":"\u0000 Targeted therapies(TT) combining FLT3 inhibitors with hypomethylating agents (HMA) and Venetoclax (Ven) are highly effective against FLT3-ITD acute myeloid leukemia (AML) with high response rates. Signaling mutations along with emergence of rarer mutations are the key contributors to primary and secondary resistance to TT. We hypothesize that resistant leukemia clones have unique proteomic profiles that facilitate survival under therapy pressure(TP) and deciphering proteomic profiles at the single-cell level will delineate resistance mechanisms and adaptive responses driven by TP. We performed multiplexed single-cell proteomic analysis of serial PB and BM samples (n:162) from patients treated with FLT3i+HMA+/-VEN using CyTOF. Unsupervised analysis identified leukemia cells and non-malignant cellular elements of the leukemia compartment in an unbiased manner. Next, we interrogated the leukemia proteomic landscape to identify leukemia associated proteomic features. Since Ven targets BCL2 and FLT3i modulates the expression of anti-apoptotic molecules we assessed the expression of apoptosis regulators and found that leukemia cells with immature phenotype, including those with leukemia stem cell(LSC) phenotype, almost always expressed moderate-high levels of BCL2. Monocytic cells(MC) lacked BCL2 expression and had the highest levels of MCL1. Despite expressing moderate levels of MCL1 and BCL-XL, TT was effective in substantially eliminating CD34+ immature leukemia cells. We observed a relative enrichment of MCs, either benign or malignant, after TT. Since cells with MC phenotype were inherently resistant to TT we hypothesized that leukemia cell subsets having similar proteomic profiles to MCs will persist after TT. Phenotypic interrogation of leukemia cells (UMAP) revealed that LSCs generally clustered on the opposite pole distant from MCs and leukemia cells on poles facing MCs were more differentiated. Remarkably, FLT3-ITD mutation partners differentially altered the proteomic landscape. NPM1 mutant FLT3-ITD AML cells displayed a less diverse leukemia architectural organization with differentiation block. Contrarily, signaling mutations diversified the leukemia landscape into a diverse continuum of differentiation states. We also observed that RAS/MAPK mutations could overcome differentiation block and gave rise to a differentiation continuum encompassing less-differentiated, transitional and differentiated leukemia cells. The transitional CD34+ leukemia cells, mapped in close vicinity to MCs, and differentiated MCs that preferentially persisted at D28, had active signaling pathways and expressed CD36. The presence of CD34+ leukemia cells with persistent signaling at D28 was indicative of poor clinical outcomes. Conclusion: Multiplexed single-cell proteomic analysis identified a unique mode of resistance and proteomic features of surviving cells in with FLT3-ITD AML patients treated with TT, and elucidated how different mutation partners in FLT3-IT","PeriodicalId":29944,"journal":{"name":"Blood Cancer Discovery","volume":" ","pages":""},"PeriodicalIF":11.2,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43106890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A50: Distinguishing Mosaic Li Fraumeni Syndrome, Clonal Hematopoiesis and Incidental Myeloid Neoplasms in Patients with Solid Tumors with Pathogenic TP53 Mutations Identified by Germline Testing or Cell-Free Circulating DNA Sequencing","authors":"S. Loghavi, Yoheved Gerstein, M. Routbort, K. Patel, Koichi Takahashi, M. Daniels, Julie B Moskowitz, D. Hammond, K. Chien, L. Medeiros, F. Ravandi, H. Kantarjian, G. Garcia-Manero, B. Arun, Joseph D. Khoury, C. Dinardo","doi":"10.1158/2643-3249.aml23-a50","DOIUrl":"https://doi.org/10.1158/2643-3249.aml23-a50","url":null,"abstract":"\u0000 The incorporation of panel-based germline genetic testing for assessment of pathogenic or likely pathogenic variants associated with increased risk of breast, ovarian, prostatic and pancreatic cancer in NCCN guidelines and wide adoption of cell-free circulating DNA sequencing (liquid biopsy) for patients with advanced solid tumors has increased the identification of pathogenic TP53 variants in blood of patients with solid tumors. The variant allelic frequency (VAF) of the pathogenic variant is often used to help infer the compartment of origin (germline vs somatic) with near heterozygous (~50%) VAF favoring germline; however, when VAF is low (sub heterozygous) potential considerations include mosaic Li Fraumeni syndrome, clonal hematopoiesis, or incidental myeloid neoplasms, and determining the origin of the TP53 mutation can be a challenge with important surveillance and treatment implications. We describe a cohort of patients with solid tumors or hematologic malignancies in whom pathogenic or likely pathogenic TP53 variants of uncertain origin were identified by clinical genetic testing of peripheral blood, next generation sequencing (NGS) using an 81 gene hematologic malignancy-based panel, or cell-free DNA sequencing/liquid biopsy. In a subset of patients for whom solid tumor, adjacent normal tissue and/or bone marrow (BM) was available, immunohistochemistry for p53 protein was performed. Patients (n= 17) included 11 (61%) women and 7 (39%) men with a median age of 54 years (range 8-7) at initial cancer diagnosis, with 17 unique TP53 variants with a median VAF of 16% (range, 2-50%). The most common indication for referral for additional investigation of the TP53 origin was sub-heterozygous VAF on germline testing of blood (8/47%) or saliva (1/6%); TP53 variant identified in plasma when the concurrent solid tumor was TP53 wild-type (3/18%) followed by presence of a pathogenic TP53 variant in remission BM of patients with history of hematologic malignancies (4/24%). Additional germline testing of skin fibroblasts and/or BM examination was performed in in 9 (53%) and 8 (47%) patients, respectively. p53 IHC was performed on 3 BM biopsies and 2 solid tumor tissues. A multimodality/multidisciplinary interpretation of these results allowed appropriate classification of the TP53 variants in 12/18 patients (67%). These included Li Fraumeni syndrome (5/12; 42%); clonal hematopoiesis (5/12; 42%); donor-derived clonal hematopoiesis (1/12;8%) and therapy-related myelodysplastic syndrome (1/12; 8%) patients. Appropriate awareness and distinction of clonal hematopoiesis and potential myeloid neoplasms from mosaic germline TP53 in the setting of subheterozygous VAF identified on peripheral blood or bone marrow analyses can be challenging. Multimodality testing and a multidisciplinary approach for accurate interpretation is required. Immunohistochemical staining for p53 can be useful in making this distinction in a subset of patients.\u0000 Citation Format: Sana","PeriodicalId":29944,"journal":{"name":"Blood Cancer Discovery","volume":" ","pages":""},"PeriodicalIF":11.2,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43469199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A46: Heterozygous mutations in DDX41 cause erythroid progenitor cell defects and cooperate with p53 mutations to cause hematologic malignancy","authors":"Timothy M. Chlon, Emily Stepanchick, Analise Sulentic, Andrew F. Wilson, D. Starczynowski","doi":"10.1158/2643-3249.aml23-a46","DOIUrl":"https://doi.org/10.1158/2643-3249.aml23-a46","url":null,"abstract":"\u0000 Germline mutations in the RNA Helicase gene DDX41 are the most common cause of inherited susceptibility to adult MDS and AML. These mutations are always heterozygous and are typically frameshifts, causing loss of functional protein. We recently reported that at least one functional copy of DDX41 is essential for hematopoiesis, and that DDX41 is required for ribosome biogenesis (Chlon et al., Cell Stem Cell 2021). While biallelic DDX41 mutations cause dramatic defects in hematopoiesis, the role of heterozygous mutations in MDS pathogenesis is not yet understood. DDX41 mutation carriers frequently experience idiopathic cytopenias of unknown significance (ICUS) prior to MDS onset, suggesting that underlying hematopoietic defects contribute to MDS/AML (Choi et al., Haemotologica 2021). The majority of DDX41-mutant MDS patients have refractory anemia, indicating that the erythroid lineage is particularly affected in these patients (Sebert et al., Blood 2019). Since ribosome defects are a common cause of inherited anemias and also contribute to MDS pathogenesis, we characterized the effect of heterozygous DDX41 mutations on erythropoiesis in murine and human models. Mice that were transplanted with Ddx41+/− bone marrow develop anemia at 12-15 months post-transplant. At younger ages, these mice have normal hematopoietic indices, but when stress erythropoiesis is induced by Pheylhydrazine-treatment, the Ddx41+/− mice have prolonged anemia. These observations indicate that heterozygous loss of DDX41 causes defects in erythropoiesis during stress and aging. We further characterized the effect of Ddx41-hetrozyogisty on erythroid progenitor function in vitro. In colony assays, we found that Ddx41+/− HSPC form fewer BFU-E but comparable numbers of myeloid colonies. In liquid culture erythroid differentiation cultures, we found that Ddx41+/− HSPC produce fewer CD71+ Ter119+ progenitors than controls. Mechanistically, we found that in vitro-derived erythroid progenitors from both mice and cell line models had decreased protein translation, suggesting that ribosome defects underlie the observed inefficiency in erythropoiesis. In congenital ribosomopathy diseases, ribosome defects lead to p53 activation which contributes to defects in erythropoiesis. Interestingly, TP53 mutations are common in DDX41-mutant MDS/AML (Sebert et al., Blood 2019), suggesting that the ribosome deficiency selects for these mutations. To assess the role of p53 mutations in the development of DDX41-mutant MDS, we generated Ddx41+/−;p53+/− mice and transplanted the bone marrow into lethally-irradiated recipients and followed the mice for 1 year. These mice developed a lethal MDS-like phenotype at 7-12 months post-transplant while control mice lived until the end of the study period. The sick mice had anemia and other cytopenias accompanied by enlarged spleens and dysplastic myeloid cells. Collectively, these results indicate that p53 mutations cooperate with Ddx41-heterozygosity to promo","PeriodicalId":29944,"journal":{"name":"Blood Cancer Discovery","volume":" ","pages":""},"PeriodicalIF":11.2,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42113875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A48: Aging-related, Senescence-associated Secretory Phenotype and Allogeneic Hematopoietic Cell Transplantation Outcomes in Older Adults","authors":"R. Lin, P. Wong, J. Flynn, Erika R Ritter, Caleb Ho, J. Ruiz, A. Jakubowski, E. Papadopoulos, B. Shaffer, H. Castro-Malaspina, C. Cho, Doris Ponce, J. Barker, R. Tamari, C. Sauter, B. Gyurkocza, M. V. D. van den Brink, J. Young, M. Perales, S. Devlin, S. Giralt","doi":"10.1158/2643-3249.aml23-a48","DOIUrl":"https://doi.org/10.1158/2643-3249.aml23-a48","url":null,"abstract":"\u0000 Introduction: Older adults with hematologic malignancies such as AML and MDS increasingly undergo allogeneic hematopoietic cell transplantation (alloHCT). The impact of the aging host environment, especially cellular senescence, remains unexplored, however.\u0000 Objectives: We hypothesize that pre-transplant senescence-associated secretary phenotype (SASP) is associated with alloHCT outcomes among older patients and tested it in this biomarker correlative study.\u0000 Methods: We measured ten SASP-related cytokines (IFNγ, IL1β, IL2, IL4, IL6, IL8, IL10, IL12, IL13, and TNFα, and C-reactive protein (CRP) from pre-transplant plasma samples of 155 patients (>50 years) who had undergone alloHCT at MSKCC from 2011 to 2019 for acute leukemias and other myeloid malignancies. Expression of aging biomarker p16 was measured on a subset of patients by immunohistochemistry.\u0000 Results and Discussion: The median age was 64.1 years (IQR 58.3 – 67.8). Diseases included 57% acute leukemias (AML and ALL) and 43% MDS/MPN. KPS was <90 in 43% and HCT-CI was >3 in 53% of patients. With median follow-up of 61 months for survivors, the 5-year OS and PFS is 50% and 46%, respectively. The 2-year cumulative incidence of non-relapse mortality (NRM) and relapse is 18% and 31%, respectively. At the baseline, these SASP-related cytokines have variable degree of association with KPS, chronologic age, and disease risk. IL2 trended toward significant positive association with OS (HR 1.19, 95% CI 1-1.43, p=0.052) and was significantly associated with PFS (HR 1.21, 95% CI 1.02-1.44, p=0025) in univariate analysis, but not in multivariate analysis after adjusting for clinical characteristics. No cytokine was associated with NRM. IL2 and IL4 were associated with relapse in univariate but not multivariate analysis. Several cytokines including IL12 p70, IL13, IL4, and TNFα were associated with 100d grade II-IV acute GVHD in patients who received CNI-based GVHD prophylaxis. In summary, we found potential association of SASP-related cytokines with patient characteristics and transplant outcomes. We aim to validate these findings and examine their therapeutic potential to improve alloHCT outcomes.\u0000 Citation Format: Richard J Lin, Phillip Wong, Jessica R Flynn, Erika R Ritter, Caleb Ho, Josel D Ruiz, Ann A Jakubowski, Esperanza B Papadopoulos, Brian C Shaffer, Hugo R Castro-Malaspina, Christina J Cho, Doris R Ponce, Juliet N Barker, Roni Tamari, Craig S Sauter, Boglarka Gyurkocza, Marcel van den Brink, James W Young, Miguel-Angel Perales, Sean M Devlin, Sergio A Giralt. Aging-related, Senescence-associated Secretory Phenotype and Allogeneic Hematopoietic Cell Transplantation Outcomes in Older Adults [abstract]. In: Proceedings of the AACR Special Conference: Acute Myeloid Leukemia and Myelodysplastic Syndrome; 2023 Jan 23-25; Austin, TX. Philadelphia (PA): AACR; Blood Cancer Discov 2023;4(3_Suppl):Abstract nr A48.","PeriodicalId":29944,"journal":{"name":"Blood Cancer Discovery","volume":" ","pages":""},"PeriodicalIF":11.2,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42262431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A19: Targeting epigenetic regulators to override cellular identity programs and induce therapeutic differentiation in MLL-rearranged acute myeloid leukemia","authors":"A. Blanco","doi":"10.1158/2643-3249.aml23-a19","DOIUrl":"https://doi.org/10.1158/2643-3249.aml23-a19","url":null,"abstract":"\u0000 Acute myeloid leukemia (AML) is a poor-prognosis disease that is universally characterized by a prominent differentiation block. Chemotherapeutic regimens and disease outcomes have not changed in decades, and there is great need for novel therapeutic treatments and approaches. Differentiation therapy is a fundamentally different therapy that aims to reactivate latent maturation programs to induce proliferation arrest and apoptosis. This approach is curative in the promyelocytic AML subtype but not others. It is therefore critical to identify the enforcers of differentiation arrest in non-APL AML. Here, we performed a cell-fate selection CRISPR screen for chromatin factors whose inhibition promotes AML cell differentiation. We found that both genetic and chemical inhibition of the histone acetyltransferase KAT6A induces myeloid maturation, most prominently in MLL-rearranged AML. KAT6A loss markedly reduces self-renewal and extinguishes the proliferative capacity of AML cells. Through ChIP-seq, RNA-seq, and clinical dataset analyses, we found that KAT6A is the likely initiator of a newly-described \"writer-reader\" module that drives oncogene expression in AML. KAT6A catalyzes promoter H3K9 acetylation, which is bound by the H3K9ac reader ENL, leading to Super-elongation complex recruitment and release of paused RNA PolII at oncogenic loci such as MYC. KAT6A is elevated in human AMLs compared to matched normal tissue, and its downregulation correlates with monocytic differentiation in clinical AML datasets. These findings suggest the potential of targeting KAT6A and/or ENL to disrupt this writer-reader module and ablate downstream MYC transcriptional programs in MLL-rearranged AML. This strategy may be viable in the near future, as a recently developed KAT6A/B inhibitor has already entered clinical trials for breast cancer. In follow-up work, we performed differentiation-specific \"synergy screens,\" in which we delivered sgRNA libraries to U937 cells and ER-Hoxb8 cells treated with or without an LSD1 inhibitor (LSD1i). We identified multiple genes whose knockout synergized with LSD1i treatment to induce complete, terminal differentiation with low toxicity. Genetic results were confirmed with small molecule inhibitors of selected hits, and the most synergistic drug combination was pursued further. We found that AML cells dependent on hyperactivity of both Hoxa9 and Meis1 are most sensitive to this drug combination. Preliminary data suggest that LSD1i treatment alone fails to downregulate Meis1 expression, and that the ability of the second drug to fully ablate Meis1 is the likely mechanism underlying the observed synergy. Importantly, the second drug is also in clinical trials and will be discussed in the abstract presentation. Altogether, this work advances our understanding of the AML differentiation block and nominates a specific drug combination for AML differentiation therapy.\u0000 Citation Format: Andres Blanco. Targeting epigenetic regulators to o","PeriodicalId":29944,"journal":{"name":"Blood Cancer Discovery","volume":" ","pages":""},"PeriodicalIF":11.2,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48926955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abstract A39: Role of LARP1 in the leukemogenesis of Acute Myeloid Leukemia","authors":"D. A. Nahotko, Aneta Baran, Mariafausta Fischietti, E. Beauchamp, L. Platanias","doi":"10.1158/2643-3249.aml23-a39","DOIUrl":"https://doi.org/10.1158/2643-3249.aml23-a39","url":null,"abstract":"Mammalian target of rapamycin (mTOR) is a strong driver of tumorigenesis in multiple types of tumors, however targeting mTOR for cancer therapy has yielded only limited success. This may be explained in part by signaling redundancy with other pathways, such as CDK9 mTOR-Like (CTORC) complexes, recently described by our group. One of the binders common to mTORC1 and CTORC2 is La related protein 1 (LARP1). LARP1 influences ribosome biogenesis by regulating translation of 5'terminal oligopyrimidine tract (5’ TOP) containing mRNAs, which often encode ribosomal proteins and translation factors. Here, we validate LARP1 as common target of mTORC1 and CTORC2 as well as investigate its influence on leukemogenesis. To explore LARP1’s role in leukemogenesis we utilized CRISPR/CAS9 technology to create OCI-AML5 and U937 LARP1 knockout (KO) cells. Loss of LARP1 expression significantly diminished proliferation potential of AML cell lines both in vitro as well as in vivo when implanted into the flank of athymic nude mice as xenografts. Additionally, primary CD34+ leukemia cells were transfected with LARP1 targeting or scrambled siRNA and leukemic progenitor growth was assessed in methocellulose colony formation assays. We observed suppression of leukemic progenitors colony forming ability in LARP1 siRNA transfected cells, compared to the Ctrl siRNA transfected cells. We also determined enhanced sensitivity of Larp1 KO cell lines to standard chemotherapy agents such Azacitidine, Cytarabine and Venetoclax. We employed polysome profiling to compare global translation levels between Larp1 KO and control U937 cells. Our polysomal profiling results show that KO of LARP1 in U937 cells reduces global translation and ribosome biogenesis as expected as we observed a suppression of both monosomal and polysomal peaks. In summary, Larp1 is important for leukemogenesis and influences their response to treatment with currently used chemotherapy agents. These observations together suggest that LARP1 is a promising target for development of novel antileukemia approaches. Citation Format: Dominik A Nahotko, Aneta H Baran, Mariafausta Fischietti, Elspeth M Beauchamp, Leonidas C Platanias. Role of LARP1 in the leukemogenesis of Acute Myeloid Leukemia [abstract]. In: Proceedings of the AACR Special Conference: Acute Myeloid Leukemia and Myelodysplastic Syndrome; 2023 Jan 23-25; Austin, TX. Philadelphia (PA): AACR; Blood Cancer Discov 2023;4(3_Suppl):Abstract nr A39.","PeriodicalId":29944,"journal":{"name":"Blood Cancer Discovery","volume":" ","pages":""},"PeriodicalIF":11.2,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46939477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}