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4344 Indoleamine 2,3-Dioxygenase-1 Expressing Dendritic Cell Populations Are Associated with Tumor-Induced Immune Tolerance & Aggressive Disease Biology in Chronic Myelomonocytic Leukemia

Program: Oral and Poster Abstracts
Session: 636. Myelodysplastic Syndromes—Basic and Translational Studies: Poster III
Hematology Disease Topics & Pathways:
Diseases, CMML, Biological Processes, Myeloid Malignancies, immune mechanism
Monday, December 3, 2018, 6:00 PM-8:00 PM
Hall GH (San Diego Convention Center)

Abhishek A. Mangaonkar, MD1, Kaaren K. Reichard, MD2*, April Chiu, MD3*, Matthew T Howard, MD4*, Rebecca L King, MD5, Ryan M. Carr, M.D., Ph.D.1*, Bonnie M Alver6*, Keith D. Robertson7*, Margot Cousin, PhD8*, Jose C Villasboas9*, Martin E. Fernandez-Zapico, MD10*, Terra L. Lasho, PhD1, Naseema Gangat, MBBS1, Aref Al-Kali, MD11, Michelle A. Elliott, MD1, William J. Hogan, MBBCh12, Mark R. Litzow, MD1, Animesh Pardanani, MBBS, PhD 1, Eric Solary, MD, PhD13, Ayalew Tefferi, MD1 and Mrinal M. Patnaik, MD, MBBS1

1Division of Hematology, Mayo Clinic, Rochester, MN
2Division of Hematopathology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN
3Mayo Clinic, Rochester, MN
4Division of Hematopathology, Mayo Clinic, Rochester, MN
5Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN
6Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester
7Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN
8Department of Health Sciences Research, Center for Individualized Medicine, Mayo Clinic, Rochester, MN
9Division of Hematology, Human Immune Monitoring Core, Mayo Clinic, Rochester, MN
10Department of Oncology, Mayo Clinic, Rochester, MN
11Division of Hematology and Medical Oncology, Department of Medicine, Mayo Clinic, Rochester, MN
12Division of Hematology, Mayo Clinic, Department of Internal Medicine, Division of Hematology, Rochester, MN
13Department of Hematology, Gustave Roussy Cancer Center, Villejuif, France

Introduction:

Chronic myelomonocytic leukemia (CMML) is a chronic myeloid malignancy associated with monocytosis, autoimmunity (~30%) & an inherent risk for leukemic transformation. Bone marrow (BM) dendritic cell (DC) populations occur in ~30% of patients, with a poorly defined biological & prognostic role. The malignant immune microenvironment is regulated by indoleamine 2,3-dioxygenase-1 (IDO-1) expressing DCs, which modulate regulatory T (Treg) cells & block their conversion into proinflammatory T helper (Th17)-like cells. IDO-1 is a known immune checkpoint & functions by catabolizing tryptophan, an amino acid essential for T cell function. We hypothesized that distinct IDO-1 expressing DC populations in CMML modulate Tregs & contribute towards immune tolerance & aggressive disease biology.

Methods:

Primary diagnostic CMML peripheral blood mononuclear cells (PBMC) & BM biopsy specimens were obtained after Mayo Clinic IRB approval. A DC population was defined on H&E stained biopsy sections as focal collections (>10) of cells with characteristic elongated nuclei & cytoplasmic extensions. Transcriptomic & protein expression studies assessing IDO-1 expression were done by previously described methods. In addition, IHC expression of PD-1, PD-L1 & CTLA-4 was also done. IDO-1 promoter methylation studies with DIP-seq were performed. The impact on immune tolerance was assessed using mass cytometry (CyTOF).

Results:

Cohort: Twenty eight patients with CMML were included in the study, median age 70 (range: 51-80) years; 71% males. Eleven (39%) patients had coexisting autoimmune conditions. Of these, 8 (73%) had detectable DC populations either at diagnosis, or during the course of their disease. At a median follow-up of 46 (95% CI 27, 84) months, there were 14 (50%) deaths & 9 (32%) leukemic transformations.

  1. IHC results: Nine (32%) patients were identified to have a DC population at CMML diagnosis. CD123 & TCL1 staining was performed in 5 (56%) patients, with 3 being positive for both, & 2 positive for CD123 only (additional IHC studies ongoing). IDO1 expression by IHC was documented in all 9 (100%) cases (Fig 1A & 1B), while rare populations of PD-1, PD-L1 & CTLA-4 lymphocytes were also seen in all cases. Due to the low DC burdens (median cellularity ≤ 5%) & uniform staining intensity, IHC-based grading was not done. Samples at serial time-points, post-HMA therapy & at the time of blast transformation, were available in 5 & 3 patients respectively. Among the patients who did not have DC populations at diagnosis, 5 (42%) developed them post-HMA therapy, while 3 (50%) developed them at the time of LT. The development of DC populations was associated with loss of response to HMA (50%) & disease progression (50%).
  2. Transcriptomic analysis: RNA expression data was available on 7 (25%) patients, of whom only 1 (14%) had DC populations at diagnosis. The IDO-1 RPKM value in the former was higher than the mean pooled value in the latter group (330 versus 74, p=0.05).
  3. Methylation studies: DIP-seq was performed on 12 (43%) cases from the primary IHC cohort. Qualitative analysis of IDO-1 promoter hypomethylation was conducted & confirmed in all 9 (100%) cases with 5-mC & 5-hmC marks compared to input as displayed in figure 1C.
  4. Immune profiling: CyTOF was performed on 4 CMML samples (3 with IDO-1 expressing DC populations at diagnosis) from the primary IHC cohort & compared to a normal PBMC control. Results confirmed an increase in DC populations (fig 1D& 1E), & reduced % of Th17-like T cells in CMML samples compared to control (1.1 versus 5.07, p=0.05, fig 1F).
  5. Clinical correlates & survival analysis: With the exception that CMML patients with DC populations had a higher frequency of NRAS (P=0.007) mutations, the two groups were comparable for cytogenetic & molecular abnormalities. The median OS for the cohort was 45 (95% CI 29, 84) months. CMML patients with IDO-1 expressing DC populations at diagnosis had a shorter median OS, in comparison to those without (median OS 30 vs 45, p=0.03, Kaplan-Meier analysis in fig 1G).

Conclusions:

In conclusion, we demonstrate that DC populations are seen in ~30% of patients with CMML with a uniform expression of IDO-1 & limited expression of PD-1, PD-L1 & CTLA-4. CMML patients with BM DC populations have a higher frequency of NRAS mutations & DC IDO-1 expression is associated with tumor induced immune tolerance. Additional IHC, genomic & preclinical studies with IDO-1 inhibitors are ongoing.

Disclosures: Al-Kali: Novartis: Research Funding.

*signifies non-member of ASH