Molecular Insights into Major Peripheral T-cell Lymphoma Entities with Advances in a Representative Model System

Peripheral T-cell lymphoma (PTCL) is a group of complex clinicopathological entities associated with an aggressive clinical course. Angioimmunoblastic T-cell lymphoma (AITL) and PTCL-not otherwise specified (PTCL-NOS) are the two most frequent categories accounting for more than 50% of PTCLs. Gene expression profiling (GEP) defined molecular signatures for AITL and delineated biological and prognostic subgroups within PTCL-NOS (PTCL-GATA3 and PTCL-TBX21). Genomic copy number analysis and targeted sequencing revealed unique genomic abnormalities and oncogenic pathways, indicating distinct oncogenic evolution. PTCL-GATA3 exhibited higher genomic complexity characterized by frequent loss or mutation of tumor suppressor genes targeting the CDKN2A/B-TP53 axis and PTEN-PI3K pathways. PTCL-TBX21 had fewer abnormalities, primarily targeting cytotoxic effector genes, and was enriched in mutations of genes regulating DNA methylation. AITL showed lower genomic complexity compared to other PTCL entities, suggesting it is epigenetically driven, yet frequent co-occurring gains of chromosome 5 and 21 were observed. Thus, to further explore the underlying pathobiology of AITL, we established an AITL-like murine model. We have found TET2 to be the most recurrent mutation in AITL with evidence that it may be a founder mutation. The generated murine model had a loss of Tet2 in CD4+ T-cells, resulting in the long-term development of an aggressive T-cell lymphoma with a TFH phenotype, similar to AITL. These mice developed lymphomas characterized by massive splenomegaly, marked generalized lymphadenopathy, hepatomegaly and occasional involvement of other parenchymal organs. Serial RNA-sequencing analysis of the pre-neoplastic and neoplastic CD4+ T-cells revealed increased PI3K-AKT signaling and decreased Foxo1 signaling likely mediated through ICOS in the neoplastic cells, promoting TFH cell expansion. Overall, we demonstrated that novel GEP-defined PTCL subgroups likely evolve by distinct genetic pathways and that AITL is driven more by epigenetic alterations, such as loss of Tet2 as it resulted in an aggressive T-cell lymphoma with a TFH phenotype. These findings emphasize the critical need for genetically faithful model systems for studying these common PTCL entities in order to improve therapeutic options

Caveolin-1 is dispensable for early lymphoid development, but plays a role in the maintenance of the mature splenic microenvironment

Objective Caveolin-1 (CAV1) is known for its role as both a tumor suppressor and an oncogene, harboring a highly context-dependent role within a myriad of malignancies and cell types. In an immunological context, dysregulation of CAV1 expression has been shown to alter immunological signaling functions and suggests a pivotal role for CAV1 in the facilitation of proper immune responses. Nonetheless, it is still unknown how Cav1-deficiency and heterozygosity would impact the development and composition of lymphoid organs in mice. Herein, we investigated the impacts of Cav1-dysregulation on the lymphoid organs in young (12 weeks) and aged (36 weeks) Cav1+/+, Cav1+/−, and Cav1−/− mice. Results We observed that only Cav1-deficiency is associated with persistent splenomegaly at all timepoints. Furthermore, no differences in overall body weight were detected (and without sexual dimorphisms). Both aged Cav1+/− and Cav1−/− mice present with decreased CD19+CD22+ B cells and secondary-follicle atrophy, specifically in the spleen, compared with wild-type controls and irrespective of splenomegaly status. Consequently, the demonstrated effects on B cell homeostasis and secondary follicle characteristics prompted our investigation into follicle-derived human B-cell lymphomas. Our investigation points toward CAV1 as a dysregulated protein in follicle-derived B-cell malignancies without harboring a differential expression between more aggressive and indolent hematological malignancies

Subtype-Specific and Co-Occurring Genetic Alterations in B-cell Non-Hodgkin Lymphoma

B-cell non-Hodgkin lymphoma (B-NHL) encompasses multiple clinically and phenotypically distinct subtypes of malignancy with unique molecular etiologies. Common subtypes of B-NHL, such as diffuse large B-cell lymphoma, have been comprehensively interrogated at the genomic level, but rarer subtypes, such as mantle cell lymphoma, remain less extensively characterized. Furthermore, multiple B-NHL subtypes have thus far not been comprehensively compared using the same methodology to identify conserved or subtype-specific patterns of genomic alterations. Here, we employed a large targeted hybrid-capture sequencing approach encompassing 380 genes to interrogate the genomic landscapes of 685 B-NHL tumors at high depth, including diffuse large B-cell lymphoma, mantle cell lymphoma, follicular lymphoma, and Burkitt lymphoma. We identified conserved hallmarks of B-NHL that were deregulated in the majority of tumors from each subtype, including frequent genetic deregulation of the ubiquitin proteasome system. In addition, we identified subtype-specific patterns of genetic alterations, including clusters of co-occurring mutations and DNA copy number alterations. The cumulative burden of mutations within a single cluster were more discriminatory of B-NHL subtypes than individual mutations, implicating likely patterns of genetic cooperation that contribute to disease etiology. We therefore provide the first cross-sectional analysis of mutations and DNA copy number alterations across major B-NHL subtypes and a framework of co-occurring genetic alterations that deregulate genetic hallmarks and likely cooperate in lymphomagenesis

The Genetic Basis of Hepatosplenic T-cell Lymphoma

Hepatosplenic T cell lymphoma (HSTL) is a rare and lethal lymphoma; the genetic drivers of this disease are unknown. Through whole exome sequencing of 68 HSTLs, we define recurrently mutated driver genes and copy number alterations in the disease. Chromatin modifying genes including SETD2, INO80 and ARID1B were commonly mutated in HSTL, affecting 62% of cases. HSTLs manifest frequent mutations in STAT5B (31%), STAT3 (9%), and PIK3CD (9%) for which there currently exist potential targeted therapies. In addition, we noted less frequent events in EZH2, KRAS and TP53. SETD2 was the most frequently silenced gene in HSTL. We experimentally demonstrated that SETD2 acts as a tumor suppressor gene. In addition, we found that mutations in STAT5B and PIK3CD activate critical signaling pathways important to cell survival in HSTL. Our work thus defines the genetic landscape of HSTL and implicates novel gene mutations linked to HSTL pathogenesis and potential treatment targets

Caveolin-1 is dispensable for early lymphoid development, but plays a role in the maintenance of the mature splenic microenvironment

Abstract Objective Caveolin-1 (CAV1) is known for its role as both a tumor suppressor and an oncogene, harboring a highly context-dependent role within a myriad of malignancies and cell types. In an immunological context, dysregulation of CAV1 expression has been shown to alter immunological signaling functions and suggests a pivotal role for CAV1 in the facilitation of proper immune responses. Nonetheless, it is still unknown how Cav1-deficiency and heterozygosity would impact the development and composition of lymphoid organs in mice. Herein, we investigated the impacts of Cav1-dysregulation on the lymphoid organs in young (12 weeks) and aged (36 weeks) Cav1 +/+, Cav1 +/−, and Cav1 −/− mice. Results We observed that only Cav1-deficiency is associated with persistent splenomegaly at all timepoints. Furthermore, no differences in overall body weight were detected (and without sexual dimorphisms). Both aged Cav1 +/− and Cav1 −/− mice present with decreased CD19+CD22+ B cells and secondary-follicle atrophy, specifically in the spleen, compared with wild-type controls and irrespective of splenomegaly status. Consequently, the demonstrated effects on B cell homeostasis and secondary follicle characteristics prompted our investigation into follicle-derived human B-cell lymphomas. Our investigation points toward CAV1 as a dysregulated protein in follicle-derived B-cell malignancies without harboring a differential expression between more aggressive and indolent hematological malignancies

MOESM2 of Caveolin-1 is dispensable for early lymphoid development, but plays a role in the maintenance of the mature splenic microenvironment

Additional file 2: Figure S2. (a) Dots plots of B-cell populations in the BM for Cav1+/+, Cav1+/−, and Cav1−/− mice at 12 and 36 weeks (n = 8–13 per group). Pre/Pro B cells designated as CD19+CD22−, immature B cells designated as CD19+CD22+. (b) Representative pseudo-color flow cytometry plots of CD4+ and CD8+ populations in the Thy at 12 and 36 weeks for listed genotypes. (c) (Dot plots show mean ± SD with each dot corresponding to a biological replicate, flow cytometry gate values show mean ± SD)

MOESM4 of Caveolin-1 is dispensable for early lymphoid development, but plays a role in the maintenance of the mature splenic microenvironment

Additional file 4: Figure S4. (a) Dot plots of CD11b+ cells in the SP and BM at the listed genotypes for 12 and 36 weeks. (b) Dot plots of CD14+ cells in the SP and BM at the listed genotypes for 12 and 36 weeks. (d) Dot plot of splenic lymphocyte percentage in 36-week mice for listed genotypes. (Dot plots show mean ± SD with each dot corresponding to a biological replicate, NS not significant, * = p < 0.05 ANOVA and Tukey post hoc test)

MOESM5 of Caveolin-1 is dispensable for early lymphoid development, but plays a role in the maintenance of the mature splenic microenvironment

Additional file 5: Table S1. Histological scoring table. Table S2. Patient characteristics from the LY6161 high-density lymphoma tissue array. Table S3. Publicly available GEO DataSets utilized for gene expression analysis. Table S4. Antibodies utilized within the study

MOESM1 of Caveolin-1 is dispensable for early lymphoid development, but plays a role in the maintenance of the mature splenic microenvironment

Additional file 1: Figure S1. (a) Bar graph of mean body (g) of listed genotypes separated by males (no fill pattern) and females (fill pattern) (n = 3–9 per group). (b) Bar graph of mean SP weight (mg) of listed genotypes separated by males (no fill pattern) and females (fill pattern) (n = 2–11 per group). (Bar graphs show mean ± SD with each dot corresponding to a biological replicate, NS not significant, * = p < 0.05 ANOVA and Tukey post hoc test)