Germ layer specification and organotropism in lymphoma invasion.

Relevance exists between tumorigenesis and embryonic development. Distinct clinical and molecular features, as well as the relationship between the pattern of lymphoma invasion and germ layer development remain largely unknown. We identified a germ layer-dependent specification of extranodal invasion (ENI) in diffuse large B-cell lymphoma. Upon R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) treatment, mesoderm-originating ENI (ENI-mesoderm) was significantly associated with inferior progression-free survival and overall survival, as compared to ectoderm-originating ENI (ENI-ectoderm) and endoderm-originating ENI (ENI-endoderm). Representative oncogenic mutations were MYD88, PIM1, and TBL1XR1 in ENI-ectoderm, TP53 and TET2 in ENI-endoderm, and MYD88, PIM1, TBL1XR1, and CD79B in ENI-mesoderm. Notably, organotrophic migration exhibited temporal disparities corresponding to germ layer development, occurring from ectoderm- to endoderm- and mesoderm-originating organs, with a similar trajectory to the germ layer process. Single-cell RNA sequencing revealed that malignant B cells follow a developmental trajectory mirroring the germ layer process, differentiating from a progenitor state enriched with NF-κB and T-cell activation signaling into two distinct branches by either upregulated B-cell receptor signaling (Path I) or sustained T-cell activation (Path II). Regarding immune checkpoints, ENI-ectoderm, ENI-endoderm, and ENI-mesoderm exhibited significant upregulation of LGALS9, PD-L1, and B7-H3, respectively. Our findings thus contributed to a better understanding of crosstalk between lymphoma progression and embryonic development, providing new insights into targeted approaches against germ layer-dependent invasion in cancer treatment.