SUMMARY
Non-Hodgkinlymphomas (NHL) represent about 90% of all lymphomas diagnosed each year and is classified
based on cell type - B cell, T cell and natural killer (NK) cell types, location - nodal or extra nodal, and the tumor
grade - aggressive (high grade) and indolent (low grade). Follicular lymphoma (FL) is the most common indolent
B-cell lymphoma but remains a largely incurable malignancy. The most clinically challenging aspect of FL is the
transformation into diffuse large B-cell lymphomas (DLBCL), characterized by the emergence of more aggressive
subclones, loss of the follicular growth spatial architecture, and resistance to treatment, leading to a much-
shortened survival period, typically less than 2 years. Among T-cell lymphomas, angioimmunoblastic T-cell
lymphoma (AITL) is one of the most common subtypes characterized by a tumor with follicular helper phenotype
surrounded by an inflammatory microenvironment, arborizing vasculature, and progression with dramatic
changes in spatial architecture. Although the discovery of FL transformation and AITL tumor evolution was
initially documented over 50 years ago, the biological mechanisms and clinical implications remain poorly
understood. No biomarkers exist to predict or therapies to prevent its metastases or progression to highly
aggressive lymphomas. Both of these tumors hijack normal follicle biology to escape immune surveillance and
potentially develop resistance clones. Yale HTAN Center aims to leverage the latest development in single-cell
and spatial omics technologies to construct a spatiotemporal atlas of human FL transformation to DLBCL and
AITL evolution. Specifically, we will apply high-plex immunofluorescence protein imaging to map all major cell
types and spatial whole transcriptome sequencing to link cell type to mutational landscape, clonal evolution, and
spatial interaction within the tumor microenvironment. We will further integrate spatial omics data with single
nucleus RNA sequencing to identify cell subtypes and niches across tissue samples over various disease stages
to construct a complete cell atlas associated with tumor transformation for different genders and racial/ethnic
groups and then computationally model the spatiotemporal evolutionary dynamics. Finally, we will apply and
integrate spatial-epigenome-transcriptome co-profiling to unveil epigenetic mechanism underlying such
transformation and potentially discover earliest events to predict the progression. The proposed spatiotemporal
lymphoma atlas represents a valuable resource to test a range of hypotheses such as how different tumor clones
emerge, interact, compete or cooperate in the spatial tissue context to drive lymphomagenesis, how T cells
recognize and interact with different mutant clones, how the microenvironment co-evolves with tumor cells, and
how to predict the likelihood of transformation and therapeutic stratification of patients. Single-cell spatial omics
techniques and computational models can be applied to other types of human tumors within the HTAN
consortium.