Figure 1.
Overexpression of the AID transgene emulates a progressive CLL-like disease. (A) Immunohistochemical analyses of spleen sections from the 3 strains euthanatized after developing leukemia. As depicted, AID levels in both AID-DT strains appeared similar to, or even higher than in, GC B cells from immunized wild-type (wt) C57BL/6 mice examined in parallel. Cre-immunized wt animals were used as controls. Micrographs for each genotype depicting AID and B220 for 3 different magnifications are depicted. Insets/squares indicate the areas where augmentation was used. Scale bars: 500, 100, and 20 µm for original magnifications of ×2.5, ×10, and ×40, respectively. Mice between 8 and 10 months were used for these experiments. Within the sensitivity range achieved by immunocytochemistry, the relative AID protein levels of the DT-AID models correlated with mRNA measurements (supplemental Figure 1B). Overall, these data indicate that both DT-AID models develop leukemia with similar histopathology and, despite relatively higher AID expression, do not exhibit dysfunctional development and are suitable to study the influence of AID in CLL evolution. After antigen detection, each section was counterstained using Mayer’s hematoxylin. (B) Submandibular vein bleeding was performed for TCL1 and DT-AID mice at 6 and 10 months. Percentages of malignant IgM+CD5+ cells are shown for ≥15 animals of the 3 genotypes. At month 10, the TCL1/Igκ-AID mean was 46% ± 8%; the TCL1/act-AID mean was 47% ± 7%; and the TCL1 mean was 26% ± 5%. (C) Comparison of spleen weights of control wt mice and animals from the 3 genotypes (n ≥ 8). Representative images of spleens are shown under the chart. (D) To determine tumor burden in leukemic animals, 10 mice from each genotype were euthanized at 6 and 10 months of age. Spleens from the 3 strains at 10 months of age were disaggregated to evaluate leukemic infiltration (IgM+CD5+ cell percentage). The TCL1/Igκ-AID mean percentage was 87% ± 5%; the TCL1/act-AID mean percentage was 64% ± 7%; and the TCL1 mean percentage was 42% ± 7%. (E) Kaplan-Meier survival curves are shown for TCL1 (n = 51), TCL1/Igκ-AID (n = 63), and TCL1/act-AID (n = 27). Survival data were obtained by observing cohorts of 10 to 51 mice for each genotype. Differences in median overall survival for both DT-AID strains (medians: TCL1/Igκ-AID = 270 days and TCL1/act-AID mice = 245 days) compared with TCL1 mice (median, 356 days) were significant (log-rank test). Overall survival of the monotransgenic AID strains was comparable to TCL1 mice (supplemental Figure 1E). Only those mice (stipulated by end-point leukemia or dying with leukemia signs) were euthanized and included in the analysis of overall survival. *P < .05, **P < .001, ***P < .001, ****P < .0001. ns, not significant.

Overexpression of the AID transgene emulates a progressive CLL-like disease. (A) Immunohistochemical analyses of spleen sections from the 3 strains euthanatized after developing leukemia. As depicted, AID levels in both AID-DT strains appeared similar to, or even higher than in, GC B cells from immunized wild-type (wt) C57BL/6 mice examined in parallel. Cre-immunized wt animals were used as controls. Micrographs for each genotype depicting AID and B220 for 3 different magnifications are depicted. Insets/squares indicate the areas where augmentation was used. Scale bars: 500, 100, and 20 µm for original magnifications of ×2.5, ×10, and ×40, respectively. Mice between 8 and 10 months were used for these experiments. Within the sensitivity range achieved by immunocytochemistry, the relative AID protein levels of the DT-AID models correlated with mRNA measurements (supplemental Figure 1B). Overall, these data indicate that both DT-AID models develop leukemia with similar histopathology and, despite relatively higher AID expression, do not exhibit dysfunctional development and are suitable to study the influence of AID in CLL evolution. After antigen detection, each section was counterstained using Mayer’s hematoxylin. (B) Submandibular vein bleeding was performed for TCL1 and DT-AID mice at 6 and 10 months. Percentages of malignant IgM+CD5+ cells are shown for ≥15 animals of the 3 genotypes. At month 10, the TCL1/Igκ-AID mean was 46% ± 8%; the TCL1/act-AID mean was 47% ± 7%; and the TCL1 mean was 26% ± 5%. (C) Comparison of spleen weights of control wt mice and animals from the 3 genotypes (n ≥ 8). Representative images of spleens are shown under the chart. (D) To determine tumor burden in leukemic animals, 10 mice from each genotype were euthanized at 6 and 10 months of age. Spleens from the 3 strains at 10 months of age were disaggregated to evaluate leukemic infiltration (IgM+CD5+ cell percentage). The TCL1/Igκ-AID mean percentage was 87% ± 5%; the TCL1/act-AID mean percentage was 64% ± 7%; and the TCL1 mean percentage was 42% ± 7%. (E) Kaplan-Meier survival curves are shown for TCL1 (n = 51), TCL1/Igκ-AID (n = 63), and TCL1/act-AID (n = 27). Survival data were obtained by observing cohorts of 10 to 51 mice for each genotype. Differences in median overall survival for both DT-AID strains (medians: TCL1/Igκ-AID = 270 days and TCL1/act-AID mice = 245 days) compared with TCL1 mice (median, 356 days) were significant (log-rank test). Overall survival of the monotransgenic AID strains was comparable to TCL1 mice (supplemental Figure 1E). Only those mice (stipulated by end-point leukemia or dying with leukemia signs) were euthanized and included in the analysis of overall survival. *P < .05, **P < .001, ***P < .001, ****P < .0001. ns, not significant.

Close Modal
This Feature Is Available To Subscribers Only

or Create an Account

Close Modal
Close Modal