How skin and liver can lead to diagnosis

A 73-year-old woman was referred by her hematologist for cholestasis of unknown origin. She was recently diagnosed with chronic myelomonocytic leukemia grade 0 in a context of fatigue, night sweats, weight loss and monocytosis. A PET-CT showed hepatosplenomegaly and multiple centimetric adenopathy. The diagnosis was confirmed by a bone marrow aspiration and biopsy. Interestingly, the evolution of the patient is marked by the appearance of cholestasis and an erythematous firm skin nodule of the right forearm. The skin lesion was biopsied to rule out a cutaneous localization of the patient’s known hemopathy.

Overactivation of the NLRP3 Inflammasome in Chronic Myelomonocytic Leukemia KRAS Mutated Patients Can be Detected By the Apoptosis-Associated Speck-like Protein (ASC) and Reverted By IL1β Inhibitors

It has been recently shown that RAS mutations, which occur in 11-38% of Chronic Myelomonocytic Leukemia (CMML), do not only act via RAS/MEK/ERK signaling, but contribute to the disease through NLRP3 inflammasome activation (Hamarsheh, Nat Comm 2020). Despite a therapeutic approach based on NLRP3/IL1β axis blockade, as bring to a stem cell transplantation (SCT) has been proposed, data on the efficacy of IL1β inhibitors in hematopoietic neoplasms is limited. A 55 year old man with previous autoinflammatory episodes (constrictive pericarditis) was diagnosed on September 2020 of CMML-1 KRAS G12D (Inter-2). Due to worsening (orchiepidedymitis, pneumonitis, cellulitis), and the impossibility of performing an SCT at that time, on December 02 2020 he started anakinra (a IL1β receptor antagonist) with good response. Due to new episodes of autoinflammation, anakinra was discontinued (12 April 2021) with severe clinical worsening (heart failure) and no response to diuretic/corticosteroid. After anakinra was restarted (04 May 2021), a progressive improvement was seen, allowing a successful pericardiectomy before an SCT. We obtained blood samples from this patient (at different times) and plasma and whole blood samples from 11 and 5 other CMML KRAS mut patients, respectively. We also included CMML patients without KRAS mutations (KRAS wt) (n=8), with sepsis (n=5) and healthy individuals (n=9). Plasma levels of 15 inflammatory cytokines associated with NLRP3 inflammasome and NFkB pathways were measured using a customized MILLIPLEX ® kit. The inflammasome marker activation assays were conducted as previously published (Martínez García JJ, Nature Comm 2019). Compared to healthy controls, KRAS wt CMML patients did not show differences in any cytokine tested, except IL6, while KRAS mut patients showed significantly higher levels of IL1α, IL1ra, IL18, IL12p40 (associated with NLRP3 inflammasome), IL6, IL8 (associated with NFkB pathway) and M-CSF (Fig. 1A B). Compared to KRAS wt CMML patients, those with KRAS mut showed higher levels of cytokines associated with both the NLRP3 and NFkB pathways, reaching statistical significance for those related with NLRP3 inflammasome. We also observed changes in inflammasome related cytokines before and after anakinra (Table 1). This cytokine profile in the plasma made us analyze the oligomerization of ASC as a marker of inflammasome activation in monocytes of KRAS mut CMML. We found that in all cases of KRAS mut CMML patients around 30 to 80% of monocytes presented oligomers of ASC measured by the time of flight assay, while in healthy donors and KRAS wt CMML patients, ASC oligomerization occurred upon NLRP3 inflammasome activation with lipopolysaccharide (LPS) + ATP or Pyrin inflammasome activation with LPS and Clostridium difficile B toxin (TcdB) (Fig. 2A). Ex vivo activation of PBMCs from KRAS mut CMML patients showed that despite the high percentage of cells with ASC oligomers, very low levels of IL1b released from these cells, even when NLRP3 was activated with LPS+ATP (Fig. 2B), suggesting that this inflammasome is activated in vivo and could not be further activated ex vivo. As control, Pyrin inflammasome activation in PBMCs from KRAS mut CMML was able to induce IL1b release similarly to healthy controls (Fig. 2B). We then found that anakinra treatment of the KRAS mut CMML patient followed in this study, resulted in a decrease of the percentage of monocytes with basal active inflammasomes (Fig. 2C). A little ex vivo activation of the NLRP3 inflammasome was obtained when cells were treated with LPS+ATP, while Pyrin inflammasome was activated at normal levels after LPS+TcdB treatment (Fig. 2D). The inflammasome basal activation increased in the monocytes of the KRAS mut CMML patient after anakinra withdraw and during clinical deterioration and restarting anakinra (second arrow) decreased the basal percentage of monocytes with ASC oligomers (Fig. 2C). Since ASC oligomers are associated to pyroptosis via caspase 1 activation and gasdermin D processing, we then analyzed pyroptotic markers in the plasma of the patient during the time. ASC was increased when monocytes presented elevated percentage of ASC oligomers (Fig. 2E), suggesting that ASC detection could be a promising biomarker. Overall, we show that, in vivo, the NLRP3 inflammasome activation of KRAS mut CMML patients may revert with IL1β blockers. ASC could identify those candidates to receive this therapy. PI18/00316 Figure 1 Figure 1. Disclosures Jerez: Novartis: Consultancy; BMS: Consultancy; GILEAD: Research Funding. Bellosillo: Thermofisher Scientific: Consultancy, Speakers Bureau; Roche: Research Funding, Speakers Bureau; Qiagen: Consultancy, Speakers Bureau. Hernández-Rivas: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene/BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees. Ferrer Marin: Cty: Research Funding; Incyte: Consultancy, Research Funding; Novartis: Speakers Bureau.

Single-Cell RNA Sequencing Analysis Reveals Mechanisms of Initiation and Progression in Chronic Myelomonocytic Leukemia

Despite advances in the genetic characterization of chronic myelomonocytic leukemia (CMML), the molecular mechanisms that drive the disease during its distinct phases remain unclear. To uncover vulnerabilities in CMML that could be therapeutically targeted to halt its evolution, we sought to dissect at the single-cell level the cellular and transcriptomic changes that occur in the hematopoietic system at the time of CMML's initiation and its progression after hypomethylating agent (HMA) therapy. To evaluate the molecular mechanisms underlying CMML maintenance, we performed single-cell RNA sequencing (scRNA-seq) analysis of lineage-negative (Lin -)CD34 + hematopoietic stem and progenitor cells (HSPCs) and bone marrow (BM) mononuclear cells (MNCs) isolated from untreated CMML patients (n=5 and 6, respectively) and age-matched healthy donors (HDs; n=2 and 3, respectively). Our integrated analysis revealed that CMML Lin -CD34 + HSPCs had a predominant granulomonocytic differentiation route with an increased frequency of early and committed myeloid-monocytic progenitors at the expense of HSCs and megakaryocyte/erythroid progenitors (Fig. 1a). Differential expression analysis among the clusters revealed that most transcriptomic differences occurred in CMML HSCs, which were characterized by the upregulation of genes involved in oxidative phosphorylation, type I interferon (IFN) and IFNγ response, myeloid development, and inflammatory signaling and had downregulated expression of genes involved in TNFα-mediated NF-κB activation (Fig. 1b). These data suggest that CMML HSCs undergo metabolic reprogramming and demand a higher level of mitochondrial activity to maintain activated monocytic differentiation in response to inflammatory signaling. Consistent with these results, scRNA-seq analysis of MNCs isolated from the same HD and CMML BM samples showed that monocytes were significantly increased at the expense of erythroid precursors and B cells in CMML (Fig. 1c). CMML monocytes had upregulated genes involved in IFNγ response, oxidative phosphorylation, MYC targets, NF-κB activation, and inflammation (e.g., S100A9, CCL3, IL1B). Interestingly, among the anti-apoptotic BCL2 family members, only the NF-κB transcriptional target BCL2A1 was significantly overexpressed. To investigate the mechanisms of resistance to HMA therapy, we performed integrated scRNA-seq analysis of sequential Lin -CD34 + cells and BM MNCs isolated from CMML patients at the time of disease initiation and progression after HMA therapy failure. CMML progression was driven by a significant expansion of lympho-myeloid progenitors (LMPPs) at the expense of earlier HSCs , which exacerbated myelomonocytic differentiation in the HSPC compartment (Fig. 1d). Expanded LMPPs were characterized by higher levels of IFNγ response, NF-κB survival signaling, and cell cycle regulators. Accordingly, scRNA-seq analysis of MNCs cells from the same patients showed significantly increased frequencies of monocytes and a reduction of naïve CD4 +/CD8 + T cells and effector memory CD8 + T cells. Differential expression analysis of the 2 sample groups in the monocyte population identified five different cellular clusters, one of which emerged only at progression (Fig. 1e). This population was characterized by high expression levels of inflammatory cytokines and the anti-apoptotic modulators MCL1 and BCL2A1. Together, these data suggest that CMML progression arises from immature myeloid progenitors at the stem cell level and that downstream monocytes undergo transcriptomic rewiring and acquire survival mechanisms that induce therapy resistance and further accelerate disease progression. In conclusion, our results elucidate the differentiation hierarchies and transcriptional programs associated with CMML's initiation and its progression after HMA therapy. Our data suggest that therapies targeting downstream effectors of NF-kB-mediated survival signaling could overcome treatment failure. Figure 1 Figure 1. Disclosures Wei: Daiichi Sanko: Research Funding. Kantarjian: AbbVie: Honoraria, Research Funding; Immunogen: Research Funding; KAHR Medical Ltd: Honoraria; Jazz: Research Funding; Ipsen Pharmaceuticals: Honoraria; Astellas Health: Honoraria; NOVA Research: Honoraria; Pfizer: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Astra Zeneca: Honoraria; Ascentage: Research Funding; Aptitude Health: Honoraria; Daiichi-Sankyo: Research Funding; Amgen: Honoraria, Research Funding; BMS: Research Funding; Precision Biosciences: Honoraria; Taiho Pharmaceutical Canada: Honoraria.

Incidence of Autoimmune Diseases, Molecular Characteristics and Clinical Outcomes of Chronic Myelomonocytic Leukemia in an Asian Population: A Single-Center Experience

Background: Chronic myelomonocytic leukemia (CMML) is the most common subtype of the rare myelodysplastic/myeloproliferative neoplasms. Some studies have described the possible association with autoimmune disease. With the potential transformation into acute myeloid leukemia, it is known to have an unfavorable prognosis. Previous studies reported TET2, SRSF2, ASXL1, and KRAS/NRAS as the most occurring somatic mutations in CMML. However, the clinical and molecular characteristics of CMML patients in Asia remained fairly unknown. Materials and Methods: Patients with CMML who were diagnosed in Siriraj Hospital, which is the largest comprehensive cancer center in Thailand, from 2010 to 2020 were identified from the hospital database. Clinical and laboratory data, along with pathological results, were collected from the same database. The results of the 25-gene targeted DNA sequencing panel designed for myeloid neoplasms were also extracted if the results were available. Continuous variables were represented as medians and their associated ranges. Overall survival (OS) was determined using Kaplan-Meier estimator and log-rank test. Results: A total of 67 patients with CMML were included in our study. The median age of the cohort was 67 years old with a similar number of male and female patients in the cohort. Thirteen (19.4%) patients were diagnosed with autoimmune diseases, mainly autoimmune hemolytic anemia and immune thrombocytopenic purpura. According to cytogenetic risk for CMML, 35 (64.8%), 6 (11.1%), and 13 (24.1%) patients were classified as low, intermediate, and high risk, respectively. The clinical characteristics and laboratory results of patients were shown in Table 1. For the 15 patients with available molecular results, 13 had at least 1 somatic abnormality with TET2 (46.7%), ASXL1, NRAS, SRSF2 (each 26.7%), and KRAS (20.0%) being the common genetic mutations. The median mutation number was 4 (range, 0-6). The molecular landscape was demonstrated in Figure 1. Overall survival (OS) rates at 1 and 2 years were 74% and 57%, respectively. Patients with MDS-CMML tended to have longer median OS compared to MPN-CMML [37.9 (13.6-62.2) months vs. 19.7 (10.1-29.4) months] but did not reach statistical significance (p=0.124) (Figure 2). Conclusions: Asian patients with CMML had a considerable amount of associated autoimmune diseases. The genetic mutations contributing to CMML in our cohort also differed from previous reports. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.