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KSHV Latency Locus Cooperates with Myc to Drive Lymphoma in Mice.

Sin SH, Kim Y, Eason A, Dittmer DP - PLoS Pathog. (2015)

Bottom Line: Kaposi sarcoma-associated herpesvirus (KSHV) has been linked to Kaposi sarcoma and B-cell malignancies.Mechanisms of KSHV-induced oncogenesis remain elusive, however, in part due to lack of reliable in vivo models.These data indicate that the KSHV latency locus cooperates with the deregulated Myc pathways to further lymphoma progression.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Program in Global Oncology, Lineberger Comprehensive Cancer Center, and Center for AIDS Research, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.

ABSTRACT
Kaposi sarcoma-associated herpesvirus (KSHV) has been linked to Kaposi sarcoma and B-cell malignancies. Mechanisms of KSHV-induced oncogenesis remain elusive, however, in part due to lack of reliable in vivo models. Recently, we showed that transgenic mice expressing the KSHV latent genes, including all viral microRNAs, developed splenic B cell hyperplasia with 100% penetrance, but only a fraction converted to B cell lymphomas, suggesting that cooperative oncogenic events were missing. Myc was chosen as a possible candidate, because Myc is deregulated in many B cell lymphomas. We crossed KSHV latency locus transgenic (latency) mice to Cα Myc transgenic (Myc) mice. By itself these Myc transgenic mice develop lymphomas only rarely. In the double transgenic mice (Myc/latency) we observed plasmacytosis, severe extramedullary hematopoiesis in spleen and liver, and increased proliferation of splenocytes. Myc/latency mice developed frank lymphoma at a higher rate than single transgenic latency or Myc mice. These data indicate that the KSHV latency locus cooperates with the deregulated Myc pathways to further lymphoma progression.

No MeSH data available.


Related in: MedlinePlus

Increased frequency of PCs in Myc/latency mice.Cells were isolated from spleen or BM from 7–11 week-old Myc (n = 5) or the Myc/latency (n = 5) mice and analyzed using flow cytometry. Lymphocytes in spleen or BM were pregated based on CD19 expression. CD19- cells were further gated using CD138 and B220. Representative FACS plots of PBs and PCs were shown. (A-B) Splenic PBs (CD19-B220+CD138+) and PCs (CD19-B220-CD138+). (C-D) PBs and PCs in BM. (E) The percentages of PBs or PCs are shown. Splenic plasmacytosis induced by increased PCs was further confirmed by immunostaining with γ heavy-chain. (F) Comparison of splenic PBs and PCs frequencies from the latency (n = 5), Myc (n = 5), and Myc/latency (n = 5) mice. Splenic cells were isolated from 7–11 week-old mice and analyzed by flow cytometry. Igγ chain staining was performed for spleen sections from the latency mouse (n = 5; G-H), single transgenic Myc mouse (n = 5; I-J), and double transgenic Myc/latency mouse (n = 5; K-L). Representative images were shown. (M) The number of Igγ chain positive cells from 400X images (n = 5 for all genotypes) was counted and plotted. (N) Isotype-specific Ig regulation by KSHV latency locus in overexpressed Myc background. Levels of Igs were measured by ELISA and plotted from the Myc mice (n = 6), and Myc/latency (n = 5). *, **, and *** represent significant difference with p ≤ 0.05, p ≤ 0.005, p ≤ 0.0005 by ANOVA, respectively.
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ppat.1005135.g001: Increased frequency of PCs in Myc/latency mice.Cells were isolated from spleen or BM from 7–11 week-old Myc (n = 5) or the Myc/latency (n = 5) mice and analyzed using flow cytometry. Lymphocytes in spleen or BM were pregated based on CD19 expression. CD19- cells were further gated using CD138 and B220. Representative FACS plots of PBs and PCs were shown. (A-B) Splenic PBs (CD19-B220+CD138+) and PCs (CD19-B220-CD138+). (C-D) PBs and PCs in BM. (E) The percentages of PBs or PCs are shown. Splenic plasmacytosis induced by increased PCs was further confirmed by immunostaining with γ heavy-chain. (F) Comparison of splenic PBs and PCs frequencies from the latency (n = 5), Myc (n = 5), and Myc/latency (n = 5) mice. Splenic cells were isolated from 7–11 week-old mice and analyzed by flow cytometry. Igγ chain staining was performed for spleen sections from the latency mouse (n = 5; G-H), single transgenic Myc mouse (n = 5; I-J), and double transgenic Myc/latency mouse (n = 5; K-L). Representative images were shown. (M) The number of Igγ chain positive cells from 400X images (n = 5 for all genotypes) was counted and plotted. (N) Isotype-specific Ig regulation by KSHV latency locus in overexpressed Myc background. Levels of Igs were measured by ELISA and plotted from the Myc mice (n = 6), and Myc/latency (n = 5). *, **, and *** represent significant difference with p ≤ 0.05, p ≤ 0.005, p ≤ 0.0005 by ANOVA, respectively.

Mentions: The KSHV latency locus alone induced plasmacytosis [29], and this phenotype was maintained in the compound Myc/latency mice, though other phenotypes of original latency mice, such as increased frequency of mature and MZ B cells, were not recapitulated in the Myc/latency mice (S1 Table). Plasmablasts (PBs; CD19-B220+CD138+) and plasma cells (PCs; CD19-B220-CD138+) were increased in the spleens of Myc/latency mice compared to Myc mice (Fig 1A and 1B). This increase was statistically significant to p ≤ 0.03 by ANOVA (Fig 1E). The increased numbers of PCs were confirmed in situ using Igγ chain immunohistochemistry. The intensity and prevalence of the staining was more robust in spleen sections of Myc/latency mice compared to those of Myc single transgenic mice (Fig 1G–1M). This phenotype was consistently seen in all mice (S3 Fig). Next, the frequencies of PBs and PCs in Myc/latency mice were compared to those of the latency mice. PBs were increased significantly in the Myc/latency mice compared to the latency mice (p ≤ 0. 001 by ANOVA), while PCs were not augmented obviously (p ≤ 0.08 by ANOVA, Fig 1F). The direct comparison of splenic PBs and PCs from the latency, Myc, and Myc/latency mice strongly suggests that the additive effect of KSHV latency locus and Myc overexpression induces higher PC and PB frequencies (Fig 1F). These data demonstrate that increased frequency of PCs in the Myc/latency mice is not a single effect of the KSHV latency locus, but the result of cooperation between the KSHV transgene and the Myc transgene. Thus, activated Myc may cooperate with KSHV latent genes to drive plasma cell proliferation/activation.


KSHV Latency Locus Cooperates with Myc to Drive Lymphoma in Mice.

Sin SH, Kim Y, Eason A, Dittmer DP - PLoS Pathog. (2015)

Increased frequency of PCs in Myc/latency mice.Cells were isolated from spleen or BM from 7–11 week-old Myc (n = 5) or the Myc/latency (n = 5) mice and analyzed using flow cytometry. Lymphocytes in spleen or BM were pregated based on CD19 expression. CD19- cells were further gated using CD138 and B220. Representative FACS plots of PBs and PCs were shown. (A-B) Splenic PBs (CD19-B220+CD138+) and PCs (CD19-B220-CD138+). (C-D) PBs and PCs in BM. (E) The percentages of PBs or PCs are shown. Splenic plasmacytosis induced by increased PCs was further confirmed by immunostaining with γ heavy-chain. (F) Comparison of splenic PBs and PCs frequencies from the latency (n = 5), Myc (n = 5), and Myc/latency (n = 5) mice. Splenic cells were isolated from 7–11 week-old mice and analyzed by flow cytometry. Igγ chain staining was performed for spleen sections from the latency mouse (n = 5; G-H), single transgenic Myc mouse (n = 5; I-J), and double transgenic Myc/latency mouse (n = 5; K-L). Representative images were shown. (M) The number of Igγ chain positive cells from 400X images (n = 5 for all genotypes) was counted and plotted. (N) Isotype-specific Ig regulation by KSHV latency locus in overexpressed Myc background. Levels of Igs were measured by ELISA and plotted from the Myc mice (n = 6), and Myc/latency (n = 5). *, **, and *** represent significant difference with p ≤ 0.05, p ≤ 0.005, p ≤ 0.0005 by ANOVA, respectively.
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ppat.1005135.g001: Increased frequency of PCs in Myc/latency mice.Cells were isolated from spleen or BM from 7–11 week-old Myc (n = 5) or the Myc/latency (n = 5) mice and analyzed using flow cytometry. Lymphocytes in spleen or BM were pregated based on CD19 expression. CD19- cells were further gated using CD138 and B220. Representative FACS plots of PBs and PCs were shown. (A-B) Splenic PBs (CD19-B220+CD138+) and PCs (CD19-B220-CD138+). (C-D) PBs and PCs in BM. (E) The percentages of PBs or PCs are shown. Splenic plasmacytosis induced by increased PCs was further confirmed by immunostaining with γ heavy-chain. (F) Comparison of splenic PBs and PCs frequencies from the latency (n = 5), Myc (n = 5), and Myc/latency (n = 5) mice. Splenic cells were isolated from 7–11 week-old mice and analyzed by flow cytometry. Igγ chain staining was performed for spleen sections from the latency mouse (n = 5; G-H), single transgenic Myc mouse (n = 5; I-J), and double transgenic Myc/latency mouse (n = 5; K-L). Representative images were shown. (M) The number of Igγ chain positive cells from 400X images (n = 5 for all genotypes) was counted and plotted. (N) Isotype-specific Ig regulation by KSHV latency locus in overexpressed Myc background. Levels of Igs were measured by ELISA and plotted from the Myc mice (n = 6), and Myc/latency (n = 5). *, **, and *** represent significant difference with p ≤ 0.05, p ≤ 0.005, p ≤ 0.0005 by ANOVA, respectively.
Mentions: The KSHV latency locus alone induced plasmacytosis [29], and this phenotype was maintained in the compound Myc/latency mice, though other phenotypes of original latency mice, such as increased frequency of mature and MZ B cells, were not recapitulated in the Myc/latency mice (S1 Table). Plasmablasts (PBs; CD19-B220+CD138+) and plasma cells (PCs; CD19-B220-CD138+) were increased in the spleens of Myc/latency mice compared to Myc mice (Fig 1A and 1B). This increase was statistically significant to p ≤ 0.03 by ANOVA (Fig 1E). The increased numbers of PCs were confirmed in situ using Igγ chain immunohistochemistry. The intensity and prevalence of the staining was more robust in spleen sections of Myc/latency mice compared to those of Myc single transgenic mice (Fig 1G–1M). This phenotype was consistently seen in all mice (S3 Fig). Next, the frequencies of PBs and PCs in Myc/latency mice were compared to those of the latency mice. PBs were increased significantly in the Myc/latency mice compared to the latency mice (p ≤ 0. 001 by ANOVA), while PCs were not augmented obviously (p ≤ 0.08 by ANOVA, Fig 1F). The direct comparison of splenic PBs and PCs from the latency, Myc, and Myc/latency mice strongly suggests that the additive effect of KSHV latency locus and Myc overexpression induces higher PC and PB frequencies (Fig 1F). These data demonstrate that increased frequency of PCs in the Myc/latency mice is not a single effect of the KSHV latency locus, but the result of cooperation between the KSHV transgene and the Myc transgene. Thus, activated Myc may cooperate with KSHV latent genes to drive plasma cell proliferation/activation.

Bottom Line: Kaposi sarcoma-associated herpesvirus (KSHV) has been linked to Kaposi sarcoma and B-cell malignancies.Mechanisms of KSHV-induced oncogenesis remain elusive, however, in part due to lack of reliable in vivo models.These data indicate that the KSHV latency locus cooperates with the deregulated Myc pathways to further lymphoma progression.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Program in Global Oncology, Lineberger Comprehensive Cancer Center, and Center for AIDS Research, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.

ABSTRACT
Kaposi sarcoma-associated herpesvirus (KSHV) has been linked to Kaposi sarcoma and B-cell malignancies. Mechanisms of KSHV-induced oncogenesis remain elusive, however, in part due to lack of reliable in vivo models. Recently, we showed that transgenic mice expressing the KSHV latent genes, including all viral microRNAs, developed splenic B cell hyperplasia with 100% penetrance, but only a fraction converted to B cell lymphomas, suggesting that cooperative oncogenic events were missing. Myc was chosen as a possible candidate, because Myc is deregulated in many B cell lymphomas. We crossed KSHV latency locus transgenic (latency) mice to Cα Myc transgenic (Myc) mice. By itself these Myc transgenic mice develop lymphomas only rarely. In the double transgenic mice (Myc/latency) we observed plasmacytosis, severe extramedullary hematopoiesis in spleen and liver, and increased proliferation of splenocytes. Myc/latency mice developed frank lymphoma at a higher rate than single transgenic latency or Myc mice. These data indicate that the KSHV latency locus cooperates with the deregulated Myc pathways to further lymphoma progression.

No MeSH data available.


Related in: MedlinePlus