[1266] Expression Profiling of Transcription Factors in Precursor Lymphoblastic Leukemia (ALL/LBL) and Burkitt Lymphoma (BL): Utility of PAX-5 Immunostaining as Pan-Pre-B-Cell Marker

MR Nasr, N Rosenthal, S Syrbu. University of Iowa Hospitals and Clinics, Iowa City, IA

Background: The optimal use of transcription factors available to determine B-lineage specificity in B-ALL/LBL has not been determined. We undertook an extensive immunohistochemistry study of a panel of B-cell transcription factors in B-ALL/LBL, T-ALL/LBL and BL seeking to find those with the best specificity and sensitivity.
Design: Tissue microarrays were constructed with duplicate paraffin-embedded tissue cores from 34 B-ALL/ABLs, 19 T-ALL/LBLs and 30 BLs samples. Immunostaining was performed on all specimens using antibodies against PU.1, OCT.2, BOB.1, MUM-1, PAX-5, CD20, CD79a and CD22. Each core was evaluated for the percentage of tumor cells staining and recorded in 4 grades (G) [G (0): 0%, G (1): 1-25%, G (2): 26-50% and G (3): >50%].
Results: The number of positive cases and the grade of staining for each of the transcription factors are shown in the table.

B-ALL/LBL (n=34)BL (N=30)T-ALL/LBL (n=19)
PAX-5 (Grade)34 (3)25 (3); 5 (2)0
BOB.1 (G)31 (3); 1 (2)25 (3); 2 (2)11 (3); 1 (2)
PU.1 (G)33 (3)11 (3); 6 (2); 6 (1)13 (3); 2 (2)
CD79a (G)25 (3); 4 (2)25 (3); 4 (2)0
CD22 (G)15 (3); 12 (2)13 (3); 1 (2)0
CD20 (G)2 (2)26 (3); 4 (2)0
OCT.2 (G)2 (3)12 (3); 5 (2); 6 (1)0
MUM-1 (G)01 (3); 4 (2)0


All B-ALL/LBLs expressed PAX-5 (34/34 [100%]), 32 (94%) of 34 expressed BOB.1, 33 (97%) of 34 expressed PU.1, 29 (85%) of 34 expressed CD79a, 27 (79%) of 34 expressed CD22, 2 (6%) of 34 expressed CD20 and OCT.2, and none (0%) expressed MUM-1. The percentages of cases expressing PAX-5, BOB.1, PU.1, CD79a, CD22, CD20, OCT.2, and MUM-1 in BLs were 100% (30/30), 90% (27/30), 77% (23/30), 97% (29/30), 47% (14/30), 100% (30/30), 77% (23/30), and 17% (5/30), respectively. All 19 cases of T-ALL/LBL were negative for CD20, CD22, CD79a, PAX-5, MUM-1, and OCT.2. However, of the 19 T-ALL/LBLs, 15 (79%) and 12 (63%) demonstrated PU.1 and BOB.1 expression, respectively.
Conclusions: We have found that PAX-5 is an excellent pan-B and pan-pre-B-cell marker and should be used as the first-line B lineage-specific marker for paraffin immunophenotyping B-ALL/LBL and BL. Pax-5 demonstrated better specificity than BOB.1 and PU.1 and better sensitivity than CD79a, CD22 and CD20. Our results suggest that the expression of Pax-5 antigen precedes the expression of CD22, CD79a and CD20. Although it is reported that OCT2 is an early B-cell differentiation antigen, only 6% of our B-ALL/B-LBL cases were positive.
Category: Hematopathology

Wednesday, March 11, 2009 1:00 PM

Poster Session VI # 174, Wednesday Afternoon

 

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