Periodic Reporting for period 1 - FolLyway2HIT (Deciphering the role of immunoglobulin classes in shaping Follicular Lymphoma molecular heterogeneity and evolution)
Période du rapport: 2023-09-01 au 2025-08-31
The FolLyway2HIT project aimed to decipher how distinct immunoglobulin heavy-chain (IgH) isotypes influence the molecular evolution of B-cell lymphomas, from the earliest precursor lesions—such as in situ follicular neoplasia (ISFN)—to aggressive high-grade forms including double-hit/triple-hit (DH/TH) lymphomas. The project built on the host laboratory’s expertise in germinal center (GC) biology and lymphoma genetics, focusing on how B-cell receptor (BCR) class determines gene expression, clonal behavior, and microenvironmental interactions during lymphomagenesis. The overarching goal was to define the mechanisms linking IgH class to transcriptional reprogramming, immune evasion, and transformation potential, thereby advancing precision medicine approaches for GC-derived lymphomas.
A large cohort of 66 primary lymphoma samples, including follicular lymphoma (FL), diffuse large B-cell lymphoma (DLBCL), DH/TH lymphomas, and ISFN, was profiled by immunohistochemistry, RNA-scope, and flow cytometry to determine the IgH isotype expressed by malignant cells.
Nineteen representative cases were selected for single-cell RNA sequencing and B-cell receptor (BCR) clonotype analyses, enabling a high-resolution integration of transcriptional identity, clonal architecture, and immune composition.
Complementary bulk transcriptomics on 22 DH/TH lymphomas revealed that tumors with detectable IgH expression (IgH⁺) and those lacking it (IgH^UND) represent distinct biological entities. IgH⁺ lymphomas displayed immune activation signatures and T-cell–rich microenvironments, while IgH^UND cases showed proliferative, metabolically active, and immune-depleted profiles.
These findings, published in Blood Cancer Discovery (2025), demonstrated that IgH^UND lymphomas predominantly derive from isotype-switched B cells, establishing a molecular link between BCR class, tumor biology, and clinical aggressiveness.
In parallel, ISFN and early FL cases were subjected to single-cell and spatial transcriptomic profiling, revealing transcriptional and microenvironmental differences between reactive and pathological germinal centers colonized by BCL2-rearranged B cells. Pathological centers exhibited enrichment in cell survival and immune evasion programs, while reactive centers showed proliferative signatures and balanced immune cell infiltration.
These results provide the first spatially resolved molecular characterization of pre-neoplastic GC lesions, highlighting the earliest changes associated with FL initiation.
Nineteen representative cases were selected for single-cell RNA sequencing and B-cell receptor (BCR) clonotype analyses, enabling a high-resolution integration of transcriptional identity, clonal architecture, and immune composition.
Complementary bulk transcriptomics on 22 DH/TH lymphomas revealed that tumors with detectable IgH expression (IgH⁺) and those lacking it (IgH^UND) represent distinct biological entities. IgH⁺ lymphomas displayed immune activation signatures and T-cell–rich microenvironments, while IgH^UND cases showed proliferative, metabolically active, and immune-depleted profiles.
These findings, published in Blood Cancer Discovery (2025), demonstrated that IgH^UND lymphomas predominantly derive from isotype-switched B cells, establishing a molecular link between BCR class, tumor biology, and clinical aggressiveness.
In parallel, ISFN and early FL cases were subjected to single-cell and spatial transcriptomic profiling, revealing transcriptional and microenvironmental differences between reactive and pathological germinal centers colonized by BCL2-rearranged B cells. Pathological centers exhibited enrichment in cell survival and immune evasion programs, while reactive centers showed proliferative signatures and balanced immune cell infiltration.
These results provide the first spatially resolved molecular characterization of pre-neoplastic GC lesions, highlighting the earliest changes associated with FL initiation.
The project produced several advances beyond current knowledge:
New molecular stratification of GC-derived lymphomas: IgH⁺ and IgH^UND tumors were shown to follow divergent transcriptional trajectories, reflecting different GC zones of origin (light-zone vs. dark-zone B cells). This discovery redefines lymphoma classification by integrating IgH class as a determinant of biological behavior and immune contexture.
Mechanistic link between IgH class and tumor–immune crosstalk: The correlation between IgH expression and microenvironmental composition revealed that BCR identity modulates immune infiltration and cytokine signaling, explaining variable immunogenicity among lymphoma subtypes.
Establishment of an in vitro transformation model: A novel high-grade B-cell lymphoma (HGBCL) model was generated by sequential retroviral transduction of primary human GC B cells with recurrent oncogenes (BCL2, MYC, TP53, FOXO1, CCND3, KLHL6). This system faithfully recapitulates stepwise transformation, including dark-zone–like phenotypes and loss of BCR signaling, providing a scalable platform to test therapeutic hypotheses.
Integration of cutting-edge single-cell and spatial technologies: The adoption of CosMx Spatial Transcriptomics enabled subcellular-resolution mapping of lymphoma architecture, setting the foundation for future precision pathology applications.
Together, these achievements significantly extend the understanding of how BCR isotype selection drives lymphoma heterogeneity and transformation—an advance directly relevant to translational oncology.
New molecular stratification of GC-derived lymphomas: IgH⁺ and IgH^UND tumors were shown to follow divergent transcriptional trajectories, reflecting different GC zones of origin (light-zone vs. dark-zone B cells). This discovery redefines lymphoma classification by integrating IgH class as a determinant of biological behavior and immune contexture.
Mechanistic link between IgH class and tumor–immune crosstalk: The correlation between IgH expression and microenvironmental composition revealed that BCR identity modulates immune infiltration and cytokine signaling, explaining variable immunogenicity among lymphoma subtypes.
Establishment of an in vitro transformation model: A novel high-grade B-cell lymphoma (HGBCL) model was generated by sequential retroviral transduction of primary human GC B cells with recurrent oncogenes (BCL2, MYC, TP53, FOXO1, CCND3, KLHL6). This system faithfully recapitulates stepwise transformation, including dark-zone–like phenotypes and loss of BCR signaling, providing a scalable platform to test therapeutic hypotheses.
Integration of cutting-edge single-cell and spatial technologies: The adoption of CosMx Spatial Transcriptomics enabled subcellular-resolution mapping of lymphoma architecture, setting the foundation for future precision pathology applications.
Together, these achievements significantly extend the understanding of how BCR isotype selection drives lymphoma heterogeneity and transformation—an advance directly relevant to translational oncology.