Abstract 4118: Mass cytometry analysis identifies rare primitive subpopulations with High STAT5 and p38 MAPK activity in a elderly male treated for chronic myelogenous leukemia.
Authors: De Jitakshi 
Published: August 2014

Abstract
Introduction: Despite promising advances in enzyme-targeted therapeutics for treatment of chronic myelogenous leukemia (CML), there is a high rate of relapse. Constitutive signaling by STAT5 transcription factor is essential for ABL-kinase driven leukemogenesis. We performed mass cytometry (MC) analysis of cell type-specific activity of this critical survival mechanism in a patient with relapsed CML.
Design: Peripheral blood from a previously treated 74y CML patient who had held therapy for approx. 2 months and had a rising WBC (7.9 K/μl) was obtained from UCSF, fixed 4 hours post-collection, and stained with a panel of 30 metal isotope-tagged antibodies including those towards lineage-associated antigens; CD127/IL-7R; p-STAT5A; p-p38 MAP kinase; and IkappaB kinase. MC performed on the CyTOF instrument at HIMC of Stanford University was analyzed on FlowJo and spanning-tree progression analysis of density-normalized events algorithms.
Results: Markedly high basal STAT5 and p38 activity was detected in minute subpopulations of CD19br/IgD-/CD45dim cells (0.36%) and CD4+/CD45br T-cells (0.24%) expressing IL-7R, and not in the IL-7R (-) lymphocytes. A less frequent p-STAT5hi/CD34+/CD117+ blast population (0.06%) had lower IL-7R, p-p38, IkappaB, and higher IL-3R compared to the other two p-STAT5hi cell-types; while neutrophils and precursors had significantly lower (∼80-100X) p-STAT5 (Table).
Conclusion: Activated STAT5 and p38 MAPK in rare post-therapy CML cells with upregulated IL-7R supports the notion that these are resistance mechanisms and possible drug targets for residual CML. Whether these are ABL kinase-driven pathways, and prognostic relevance of rare circulating CD19+/IL-7R+ cells in the context of previously treated CML remains to be elucidated. Furthermore, such activated networks in a rare subset of CD4+ T-cells suggest these are also oncogene-addicted immune evasion mechanisms.
Raw median values of selected antigens PMNs Monocytes B-cells CD4+ T-cells CD8+ T-cells p-STAT5hi CD4+ CD127+ T-cells p-STAT5hi CD19br CD45dim CD127+ cells p-STAT5hi CD34+ CD117+ blasts L-shifted PMNs Intracellular markers p-STAT5 38.3 7.0 3.0 0 0 3450 3756 3423 98.9 p-STAT3 10.6 1.4 0.8 0 0 25.1 26.1 42.9 9.1 p-p38 MAP kinase 52.9 13.4 8.6 1.7 1.2 5251 5882 2260 46.3 p-ERK 36.4 25.3 21.6 7.0 5.9 8.6 10.9 72.6 28.9 p-pS6 kinase 5.3 0 0.5 0 0 2.3 0.6 38 4.6 IKB kinase 82.8 20.9 13.4 3.4 2.5 8988 9130 3334 73.0 Surface markers CD34 4.4 2.9 1.7 0 0 14.1 19.9 2798 28.1 CD45 367 2345 2340 2905 3392 3750 720 128 26.2 CD117 3.9 0 0 0 0 0 0 1393 29.5 CD127 13.4 2.1 0.6 0 0 569 982 96.6 4.2 CD123 0 0.3 1.5 6.5 7.9 15.0 6.3 42.1 0 HLA-DR 0.5 144 234 0 0 0 0 45.9 5.6 CD19 6.4 0.4 19.5 0 0 37.1 326 26.7 0 IgD 19.9 27.8 44.9 9.3 6.2 1.9 1.5 87.3 75.5 CD3 12.8 9.9 13.7 1316 1615 1163 17.4 0 0 CD4 1.2 48.3 5.1 493 0 238 34.9 208 6.6 CD7 3.4 0.8 2.0 87.1 114 61.5 3.9 0 0 CD66 1218 3.0 2.8 0.2 4.6 3.2 2.0 24.0 183 CD33 3.5 61.2 4.5 0 0 0 0 1.5 8.0 CD38 11.4 42.0 12.6 0 0 0 0 3.2 6.3 % cells 56.6 6.4 2.2 15.7 14.5 0.2 0.4 0.1 1.8
Citation Format: Jitakshi De. Mass cytometry analysis identifies rare primitive subpopulations with High STAT5 and p38 MAPK activity in a elderly male treated for chronic myelogenous leukemia. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4118. doi:10.1158/1538-7445.AM2013-4118