TY - JOUR
T1 - Flow cytometric false myeloperoxidase-positive childhood B-lineage acute lymphoblastic leukemia
AU - Savaşan, Süreyya
AU - Buck, Steven
AU - Gadgeel, Manisha
AU - Gabali, Ali
N1 - Funding Information:
This work is partly supported by funds from Children’s Hospital of Michigan Foundation, Kids without Cancer Foundation (formerly known as Leukemia Research Life) and Karmanos-Ginopolis Fund.
Publisher Copyright:
© 2017 International Clinical Cytometry Society
PY - 2018/5
Y1 - 2018/5
N2 - Background: Flow cytometric intracellular myeloperoxidase (MPO) staining of leukemic blasts is a useful tool in diagnosis of leukemia subtype. Interpretation of high MPO-positivity can be a diagnostic challenge in B-lineage acute lymphoblastic leukemia (B-ALL). While very few such cases have been reported, high MPO positive B-ALL cases without additional myeloid antigen positivity are suspect and require further investigation. Methods: Three pediatric cases of B-ALL with strong MPO staining (clone 8E6; Invitrogen) at diagnosis and three others with negative MPO staining were studied by flow cytometry and immunohistochemistry. In-vitro drug cytotoxicity, oxidative stress generation, and immunophenotyping using other MPO clones were performed to further investigate MPO presence. Results: Expectedly, normal myeloid cells in all six samples were positive and mature lymphocytes negative for MPO staining. However, MPO monoclonal antibody (mAb) obtained from clones other than Invitrogen and other myeloid-specific mAbs gave negative results suggesting false positivity of the initial MPO staining. Immunohistochemistry for MPO was also negative on all six cases tested. Furthermore, in-vitro vincristine cytotoxicity was greater in leukemic cells from MPO false-positive cases compared with MPO-negative B-ALL samples, demonstrating indirect lack of MPO activity. Moreover, drug treatment did not lead to generation of reactive oxidative species, also reflective of lack of significant MPO presence. Conclusions: The cause of false-positive MPO staining remains unknown in these three cases; a cross reactivity could be the culprit. Caution should be given to similar phenomena and detailed investigation may contribute to the understanding of altered protein expression in such outlier cases.
AB - Background: Flow cytometric intracellular myeloperoxidase (MPO) staining of leukemic blasts is a useful tool in diagnosis of leukemia subtype. Interpretation of high MPO-positivity can be a diagnostic challenge in B-lineage acute lymphoblastic leukemia (B-ALL). While very few such cases have been reported, high MPO positive B-ALL cases without additional myeloid antigen positivity are suspect and require further investigation. Methods: Three pediatric cases of B-ALL with strong MPO staining (clone 8E6; Invitrogen) at diagnosis and three others with negative MPO staining were studied by flow cytometry and immunohistochemistry. In-vitro drug cytotoxicity, oxidative stress generation, and immunophenotyping using other MPO clones were performed to further investigate MPO presence. Results: Expectedly, normal myeloid cells in all six samples were positive and mature lymphocytes negative for MPO staining. However, MPO monoclonal antibody (mAb) obtained from clones other than Invitrogen and other myeloid-specific mAbs gave negative results suggesting false positivity of the initial MPO staining. Immunohistochemistry for MPO was also negative on all six cases tested. Furthermore, in-vitro vincristine cytotoxicity was greater in leukemic cells from MPO false-positive cases compared with MPO-negative B-ALL samples, demonstrating indirect lack of MPO activity. Moreover, drug treatment did not lead to generation of reactive oxidative species, also reflective of lack of significant MPO presence. Conclusions: The cause of false-positive MPO staining remains unknown in these three cases; a cross reactivity could be the culprit. Caution should be given to similar phenomena and detailed investigation may contribute to the understanding of altered protein expression in such outlier cases.
KW - B lineage acute lymphoblastic leukemia
KW - cytotoxicity
KW - false positive
KW - flow cytometry
KW - intracellular myeloperoxidase
KW - oxidative stress
UR - http://www.scopus.com/inward/record.url?scp=85047868070&partnerID=8YFLogxK
U2 - 10.1002/cyto.b.21613
DO - 10.1002/cyto.b.21613
M3 - Article
C2 - 29244249
AN - SCOPUS:85047868070
VL - 94
SP - 477
EP - 483
JO - Cytometry Part B - Clinical Cytometry
JF - Cytometry Part B - Clinical Cytometry
SN - 1552-4949
IS - 3
ER -