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994 MYC-Alarmin Axis As a Novel Oncogenic Driver in a Subgroup of Triple Negative Myeloproliferative NeoplasmsClinically Relevant Abstract

Program: Oral and Poster Abstracts
Type: Oral
Session: 631 Myeloproliferative Syndromes and Chronic Myeloid Leukemia: Basic and Translational: Oncogenic Drivers and Genetic Models
Monday, December 11, 2023: 5:15 PM

Nicole D. Vincelette, PhD1, Xiaoqing Yu, PhD2*, Andrew T. Kuykendall, MD3, Jungwon Moon1*, Siyuan Su4*, Chia-Ho Cheng, PhD5*, Rinzine Sammut, MD1*, Hai Vu Nguyen, PhD6*, Erika Adriana Eksioglu, PhD, MS7, Onyee Chan, MD8, Najla H Al Ali, MS8*, Parth C. Patel, DO, MS1, Dae Hyun Lee9*, Shima Nakanishi, PhD10*, Renan Ferreira11*, Qianxing Mo, PhD3*, Suzanne Cory12*, Harshani Lawrence, PhD11*, Ling Zhang, MD13, Daniel Murphy, PhD14*, Rami S. Komrokji, MD8, Daesung Lee, PhD4*, Scott H. Kaufmann, MD, PhD15, John L. Cleveland, PhD16 and Seongseok Yun, MD, PhD8

1Malignant Hematology, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL
2Department of Biostatistics and Bioinformatics, Moffitt Cancer Center, Tampa, FL
3Moffitt Cancer Center, Tampa, FL
4Chemistry, University of Illinois Chicago, Chicago, IL
5Biostatistics and Bioinformatics, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL
6Walter and Eliza Hall Institute, Parkville, Australia
7Immunology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL
8Department of Malignant Hematology, Moffitt Cancer Center, Tampa, FL
9University of South Florida, Tampa, FL
10Tumor Biology, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL
11H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL
12Walter and Eliza Hall Institute, Pariville, Australia
13Department of Pathology, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL
14University of Glasgow, Glasgow, United Kingdom
15Mayo Clinic, Rochester, MN
16Department of Tumor Biology, Moffitt Cancer Center, Tampa, FL

Primary Myelofibrosis (PMF) is an aggressive myeloproliferative neoplasm (MPN) characterized by constitutional symptoms, cytopenias, splenomegaly, extramedullary hematopoiesis, bone marrow (BM) fibrosis, and a propensity to transform to acute myeloid leukemia (AML). Despite advances in understanding the underlying genetic abnormalities in MPN and the development of JAK2 inhibitors to treat MF, there is an urgent need to devise new treatment strategies, particularly for triple negative myelofibrosis (TN-MF) cases that lack mutations in the JAK2 kinase pathway and who have inferior outcomes.

To identify potential oncogenic drivers in TN-MF, we performed cytogenetic analyses and targeted exome sequencing of 98 genes commonly mutated in myeloid malignancies in 584 MF patients identified from the Total Cancer Care database at Moffitt Cancer Center. Notably, there were no significant differences in the somatic mutation profiles (other than JAK2 activating mutations) between TN vs. JAK2/CALR/MPL mutant MF patients. However, trisomy of chromosome 8 occurs more frequently in TN-MF vs. other subtypes (26.7% vs. 6.2%, p=0.0001). To identify oncogenic drivers in trisomy 8+ TN-MF, we performed scRNA-seq analysis from 18,651 cells (n=15,850 from 3 normal donors and n=2,801 from a trisomy 8+ TN-MF patient) and identified a total of 1,260 genes that are differentially regulated in hematopoietic stem cells (HSCs) of trisomy 8+ TN-MF compared to normal donors. Among these, 131 genes were located on chromosome 8 and MYC was one of the top 5 genes that are significantly upregulated in trisomy 8+ HSCs. Additional immunohistochemistry staining demonstrated that MYC protein levels in BM cells were significantly higher in trisomy 8+ TN-MF patients vs. trisomy 8- patients.

To assess whether MYC might be a driver of MPN, we established an Mx1-Cre+/-;Rosa26LSL-MYC/LSL-MYC transgenic mouse model that inducibly overexpresses MYC in HSCs following treatment of polyinosinic-polycytidylic acid (pIpC). Forced MYC expression induced profound anemia, monocytosis, megakaryocytic atypia, splenomegaly, increased BM collagen deposition/fibrosis, extramedullary hematopoiesis in spleen and liver, and significantly reduced OS vs. Mx1-Cre+/- wild type controls (median OS 258 days vs. not reached (NR), p<0.0001). MYC also promoted expansion of HSCs, myeloid progenitors, and Gr-1+/CD11b+ mature myeloid cells in BM and spleen; thus, MYC was sufficient to provoke MF-like disease independent of JAK2 pathway mutations. Subsequent scRNA-seq analysis of 25,232 cells (n=13,552 from control and n=11,680 from a MYC transgenic mouse) revealed that S100a9 mRNA levels were increased by MYC in most major hematopoietic cell types. Supporting oncogenic roles of S100A9 in MYC-driven MF, deletion of S100a9 in Mx1-Cre+/-;Rosa26LSL-MYC/LSL-MYC;S100a9-/- mice abolished MYC-induced MF phenotypes and significantly improved OS (median OS NR vs. 225 days, p=0.0345).

To test whether inhibition of MYC can suppress MF disease progression in vivo, lethally irradiated CD45.1+/CD45.2+ WT mice were transplanted with BM cells harvested from CD45.2+ Mx1-Cre+/-;Rosa26LSL-MYC/LSL-MYC mice that were treated with pIpC 20 weeks prior to transplant. MYCi975, a small molecule that inhibits MYC, reduced MYC and S100a9 protein levels in BM and spleen cells. Further, MYCi975 effectively suppressed MYC-driven MF phenotypes and disease progression, and significantly improved OS (median OS NR vs. 252 days, p=0.0109).

In summary, our studies are the first to describe an oncogenic role of MYC in MF pathogenesis, where MYC provokes an alarmin-driven inflammatory circuit, and where the MYC-S100A9 axis represents a therapeutic vulnerability for TN-MF patients. Accordingly, our results provide a strong rationale for testing agents targeting MYC or S100A9 in early phase clinical trials in MPNs having increased MYC levels or activity.

Disclosures: Kuykendall: Protagonist Therapeutics, Inc.: Consultancy, Research Funding; Prelude: Research Funding; BMS: Consultancy, Research Funding; AbbVie: Consultancy; Sierra Oncology: Research Funding; Morphosys: Consultancy, Research Funding; Incyte: Consultancy; Imago: Consultancy; CTI: Consultancy; Blueprint: Consultancy, Research Funding, Speakers Bureau; GSK: Consultancy; Novartis: Consultancy. Chan: BMS: Honoraria; AbbVie: Honoraria. Komrokji: BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Geron: Consultancy; AbbVie, CTI biopharma, Jazz, Pharma Essentia, Servio: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Rigel, Taiho, DSI: Honoraria, Membership on an entity's Board of Directors or advisory committees.

*signifies non-member of ASH