Single cell analysis of follicular lymphoma patient-derived xenograft in avian embryos

Despite achieving high rates of complete remission with RCHOP immuno-chemotherapy, almost all patients with follicular lymphoma (FL) will experience multiple relapses after treatment. The understanding of the heterogeneity of treatment responses is limited by the absence of in vitro or in vivo experimental models. Here, we develop a primary FL cell xenograft model in chicken embryos to capture treatment response heterogeneity and analyze the mechanisms of response to immune-chemotherapy. Using light sheet microscopy, we observed that tumor volume reduction achieved with RCHOP treatment in ovo predicted progression free survival in multivariate analysis. To further explore the model, we used single-cell RNA sequencing to discover a signature of 21 genes upregulated after RCHOP exposure, with significant intratumoral heterogeneity. As a proof of concept, we functionally validated the involvement of BAX as a critical effector of RCHOP which can be targeted with venetoclax in vitro and in ovo. Overall design: Human lymph nodes from follicular lymphoma samples before and after avian transplantation with RCHOP or vehicle treatment