title: Expression of PAX5 in CD20-positive multiple myeloma assessed by immunohistochemistry and oligonucleotide microarray.
abstract: Silencing of PAX5 gene by upregulation of B-lymphocyte-induced maturation protein-1 (PRDM1) is essential for terminal differentiation of B cells to plasma cells. To investigate PAX5 gene expression and its protein product, B-cell-specific activator protein (BSAP), in a subgroup of multiple myeloma characterized by CD20 expression, we studied PAX5/BSAP by immunohistochemistry in 25 cases of myeloma, all expressing moderate to strong CD20 by flow cytometric analysis, and correlated the results with PAX5 and PRDM1 mRNA levels analyzed by the Affymetrix HuGeneFL GeneChip microarray in 17 cases. Using paraffin-embedded bone marrow biopsy sections, we found PAX5/BSAP was expressed in 72% (18/25) of cases overall with an intensity ranging from weak (10, 56%) to strong (8, 44%). PAX5/BSAP was negative in 10 randomly selected CD20-negative myelomas included as negative controls. PAX5 mRNA levels correlated inversely with that of PRDM1 in both CD20-positive and CD20-negative myelomas and failed to predict the expression levels of PAX5/BSAP, suggesting that detected PAX5/BSAP likely represents remnant of earlier stage of development. We conclude that CD20-positive myelomas expressing PAX5/BSAP can present as a diagnostic pitfall mimicking B-cell neoplasms with plasmacytoid differentiation.
authors.affiliation: Department of Pathology, University of Arkansas for Medical Science, USA. peilin@mdanderson.org
authors.forename: Pei
authors.initials: P
authors.lastname: Lin
authors.forename: Mustafa
authors.initials: M
authors.lastname: Mahdavy
authors.forename: Fenghuang
authors.initials: F
authors.lastname: Zhan
authors.forename: Hua-Zhong
authors.initials: HZ
authors.lastname: Zhang
authors.forename: Ruth L
authors.initials: RL
authors.lastname: Katz
authors.forename: John D
authors.initials: JD
authors.lastname: Shaughnessy
mesh_terms: D000328:Adult; D000368:Aged; D018951:Antigens, CD20 / Q000096:biosynthesis*; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D015345:Oligonucleotide Probes / Q000235:genetics; D051757:PAX5 Transcription Factor; D000074462:Positive Regulatory Domain I-Binding Factor 1; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D018951:Antigens, CD20; D004268:DNA-Binding Proteins; D015345:Oligonucleotide Probes; D051757:PAX5 Transcription Factor; C497281:PAX5 protein, human; D012333:RNA, Messenger; D012097:Repressor Proteins; D014157:Transcription Factors; C087042:PRDM1 protein, human; D000074462:Positive Regulatory Domain I-Binding Factor 1