[1356] WT1 RNA Expression in Different Cell Lineages in Normal and Leukemic Bone Marrow

Daphne C Ang, Fei Yang, Chenxue Qu, Ginny Lanier, Guang Fan, Richard Press. Oregon Health and Science University, Portland, OR

Background: The WT1 gene is over-expressed in the bone marrow and peripheral blood of patients with acute myeloid leukemia (AML) and high expression levels are prognostic of poor outcomes. WT1 has been previously shown to be expressed in normal CD34+ bone marrow cells, but at a level about 100 to 1000 times lower than in leukemic cells. However, WT1 expression in other cell lineages including PMN's, lymphocytes, and monocytes (in normal and leukemic samples) is unknown.
Design: Bone marrows (BM) from 8 normal, 13 AML (including 1 acute promyelocytic leukemia (APL)), 4 acute lymphoblastic leukemia (ALL) patients; and peripheral blood (PB) samples from 9 AML (including 3 AMML and 3 M5) patients were fluorescence-activated cell sorting (FACS)-sorted into 4 lineages: CD34+ blasts, CD14+/CD64+ monocytes (MONO), CD45+ lymphocytes (LYMPH), and neutrophils (PMN) sorted by characteristic side and forward scatter. FACS-sorted samples were examined for WT1 expression levels by quantitative reverse trascriptase-polymerase chain reaction (normalized to the ABL reference gene).
Results: The WT1 expression level of normal and ALL patients was significantly lower (2-3 logs lower) across all cell lineages as compared to AML patients (p=.02). Among AML samples, WT1 was highly expressed, not only in the blast population but also in the PMNs and to a lesser degree in the monocytes.

Table 1. Mean WT1 expression (CU) of different cell lineages in normal and leukemic BM and PB
 NORMALAML (BM)AML (PB)ALL
PMN214800180018
BLAST4911000470018
LYMPH84503601
MONO301300766


The WT-1 RNA levels in bone marrow among AML cases were not statistically different from peripheral blood (p=0.16). In two patients with follow up available, post-treatment bone marrow showed residual/relapsed AML and sorted blasts and PMNs likewise showed persistent elevation of WT-1 levels.
Conclusions: These results suggest that WT-1 is aberrantly overexpressed in myeloid leukemic cells. WT-1 overexpression is not solely confined to the blast cells, but is also seen in the maturing myeloid and monocytic lineages. The WT1-expressing leukemic blasts may then ultimately mature to neutrophils and monocytes.
Category: Hematopathology

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 220, Tuesday Morning

 

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