OUP user menu

Expression of B Cell–Specific Activator Protein/PAX5 in Acute Myeloid Leukemia With t(8;21)(q22;q22)

Jose R. Valbuena MD, L. Jeffrey Medeiros MD, George Z. Rassidakis MD, PhD, Suyang Hao MD, C. Daniel Wu MD, Lei Chen MD, Pei Lin MD
DOI: http://dx.doi.org/10.1309/LG0Q0VXYBETJ4VHE 235-240 First published online: 1 August 2006


The blasts of acute myeloid leukemia (AML) with t(8;21)(q22;q22) frequently express the B-cell antigen CD19, which is regulated by B cell–specific activator protein (BSAP) encoded by the PAX5 gene, a protein important for B-cell lineage commitment and development. We assessed for BSAP expression in 28 AML cases with t(8;21) and 46 AML cases of other types. CD19 was expressed by 26 (93%) cases of AML with t(8;21) and 1 AML case (2%) without t(8;21). We also tested a subset of cases for the B-cell transcription factors Oct2 and OCA-B (BOB.1) and the B-cell antigens CD20, CD22, and CD79a. Immunostaining performed on bone marrow biopsy specimens demonstrated BSAP expression in all 28 AML cases with t(8;21): weak, 21; strong, 7. By contrast, BSAP was expressed weakly in only 1 AML case without t(8;21). Oct2 was expressed strongly in 12 of 16 AML cases with t(8;21) and 19 of 46 without t(8;21). OCA-B, CD20, CD22, or CD79a were negative in all cases assessed. These results indicate that silencing of PAX5 is not required for commitment to myeloid differentiation and that BSAP expression in AML is found mainly in cases with t(8;21).

Key Words:
  • Acute myeloid leukemia with t(8;21)
  • B cell–specific activator protein
  • PAX5
  • Flow cytometry
  • Immunohistochemistry