Follicular Lymphoma Organoids for Investigating the Tumor Microenvironment

Background: Current in vitro lymphoma models, including three-dimensional organoids, generally contain exclusively neoplastic lymphocytes and require artificial reconstitution to recapitulate the tumor microenvironment (TME). The co-culture of syngeneic tumor-infiltrating lymphocytes (TILs) alongside endogenous primary malignant lymphocytes could be useful for modeling complex interactions in the TME, and for immunological maneuvers and therapies relying on TILs. However, such conditions for maintaining lymphomas in their syngeneic TME as a cohesive unit have remained elusive.

Methods: We adapted an air-liquid interface (ALI) method that we previously described (Neal JT et al 2019 Cell) for propagating patient-derived organoids (PDOs) from primary human follicular lymphomas. Surgically excised lymphoma samples were tested for the ability to maintain lymphoma cell viability in vitro using a lymph node organoid technique. Lymph nodes containing lymphoma cells (and in one case, a PBMC sample including circulating lymphoma cells) were processed into a single cell suspension and frozen until use. Samples were thawed and prepared into immune organoids (see figure). We assessed cell composition by flow cytometry on day 7, and in a subset of samples, up to 21 days post-thaw.

Results: A total of 6 patients were profiled for PDO formation, PDO composition and stability, and PDO longevity. 4 of 6 samples showed good cell viability at day 7 post-culture and in a subset of samples, up to 21 days post-culture. Cell composition was well-maintained over time, with presence of lymphoma cells (CD19+ CD10+ CD5-) easily detectable and maintenance of supporting cells of the lymph node such as T follicular helper cells (CD3+ CD4+ CXCR5+ PD-1+) and non-B, non-T cells. Supporting lymph node cells were not detected in the PBMC sample, suggesting the cell composition is related to the initial composition and not due to differentiation in vitro. Genotyping, gene expression phenotyping, and T-cell/B-cell receptor profiling data will be presented at the meeting, including accuracy of PDOs for preserving the original spectrum of these indices.

Conclusions: Propagation of PDOs of primary lymphomas with endogenous immune stroma is feasible and maintains cohesive elements of the TME. This system should allow immunoncology investigations within the TME and to facilitate personalized immunotherapy testing.

Fig 1: Human lymphoma organoid cultures as a model to study tumor microenvironments and immune responses in vitro. (A) Experimental schema for preparing lymphoma organoids from tumor explants. In an adapted workflow optimized for ex vivo culture of human tonsillar germinal centers (Wagar L et al, submitted), we subject cryopreserved FL samples to organoid culture. (B) An example of follicular lymphoma organoid reorganization in vitro after four days in culture. (C) Total cell viability in FL organoids for up to 21 days in culture. Six samples were tested. (D) Frequency of major cell types in FL samples after organoid culture. Although there is variation among donors' samples, an individual's cell composition is well maintained for at least 14 days in most organoids.

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