De novo diffuse large B-cell lymphoma with a CD20 immunohistochemistry-positive and flow cytometry-negative phenotype: molecular mechanisms and correlation with rituximab sensitivity.
Bottom Line: Rituximab-mediated cytotoxicity in the CDC assay using IHC(+)/FCM(-) primary cells was significantly lower than in IHC(+)/FCM(+) cells (P < 0.05); however, partial effectiveness was confirmed.No significant difference was observed between IHC(+)/FCM(-) and IHC(+)/FCM(+) patients in overall survival (P = 0.664).FCM using rituximab may be more informative than B1 for predicting rituximab effectiveness in IHC(+)/FCM(-) cases.
Affiliation: Department of Hematology and Oncology, Nagoya University Graduate School of Medicine, Nagoya, Japan; Department of Hematology/Oncology Research, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan.Show MeSH
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Mentions: Primary or cryopreserved lymphoma tissues showing the CD20 IHC(+)/FCM(−) phenotype obtained in Nagoya University Hospital (n = 8) and the affiliated hospitals (n = 4) were used for further analyses (Table2). Representatives of this phenotype are shown in Figure1(a) (IHC) and 1(b) (FCM). For IHC analysis, B cells were confirmed with anti-CD79a antibody, which recognizes a B-cell receptor component. CD20 protein expression was also confirmed in CD79a-positive B cells (Fig.1a). For FCM analysis, lymphoma cells were gated by side scatter and forward scatter or the CD45 expression level, and CD19-positive B-cell lymphoma populations were confirmed (Fig.1b). However, CD20 expression was not confirmed in these cell populations. B-cell light chain restriction was also confirmed with FCM, and 4 out of 12 cases (33.3%) expressed neither kappa-light chains nor lambda-light chains (Fig.1b and Table2). Interestingly, seven out of eight patients who expressed either the kappa or lambda chain expressed the kappa chain (87.5% of light chain-expressing patients). This percentage in CD20 IHC(+)/FCM(−) patients was higher tendency than that in CD20 IHC(+)/FCM(+) patients (nine out of 20 patients in Table1 [45.0%]).
Affiliation: Department of Hematology and Oncology, Nagoya University Graduate School of Medicine, Nagoya, Japan; Department of Hematology/Oncology Research, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan.