N-terminal PAX8 polyclonal antibody shows cross-reactivity with N-terminal region of PAX5 and is responsible for reports of PAX8 positivity in malignant lymphomas.
Recently, reports using immunohistochemistry and a polyclonal antibody directed against the N-terminal region of PAX8 describe PAX8 expression in malignant lymphomas. As the N-terminal regions of PAX family members, including the B-cell transcription factor PAX5, have high sequence homology, we investigated PAX8 positivity in malignant lymphomas. Comparative sequence analysis between the N- and C-terminal regions of PAX8 and PAX5 proteins confirmed homologies of 70% and 39%, respectively. We then compared the results using N-terminal (high homology) and C-terminal (lower homology) anti-PAX8 antibodies to assess PAX8 expression in reactive tissues, diffuse large B-cell lymphoma and classical Hodgkin lymphoma, using routine immunohistochemical methods. Expression of PAX8 was also assessed in diffuse large B-cell lymphoma and classical Hodgkin lymphoma cell lines using real-time qRT-PCR methods. Our results show that reactive and neoplastic B-cells are positive for PAX8 using the N-terminal antibody, but negative for PAX8 when the C-terminal antibody was used. PAX8 mRNA levels were not detected in any of the B-cell lymphoma cell lines studied. These results indicate that benign and malignant B-cells do not express PAX8. We conclude that positivity for PAX8 reported by others in B-cell lymphomas is likely due to cross-reactivity between the N-terminal regions of PAX8 and PAX5, due to the high sequence homology of these two regions.
Department of Hematopathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
Lucas
L
Moretti
L Jeffrey
LJ
Medeiros
Kranthi
K
Kunkalla
Michelle D
MD
Williams
Rajesh R
RR
Singh
Francisco
F
Vega
D000595:Amino Acid Sequence; D000918:Antibody Specificity; D014408:Biomarkers, Tumor / Q000032:analysis*; D003429:Cross Reactions; D006801:Humans; D007150:Immunohistochemistry; D016393:Lymphoma, B-Cell / Q000378:metabolism*; D008969:Molecular Sequence Data; D051757:PAX5 Transcription Factor / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
D014408:Biomarkers, Tumor; D051757:PAX5 Transcription Factor; C497281:PAX5 protein, human; D000072636:PAX8 Transcription Factor; C083325:PAX8 protein, human; D051761:Paired Box Transcription Factors