Tumour assembloids recapitulate tumour–CAF–T cell crosstalk in renal cancer

Abstract Dynamic interactions between tumours and their microenvironment are crucial for cancer progression and therapeutic outcomes 1,2 . However, our understanding of these relationships remains limited by the constrained capacity of current human model systems to manipulate diverse cellular components and to interrogate complex tumour–stroma crosstalk. Here we generated combinatorial, mix-and-match tumour assembloids by conditionally reconstituting multiple components of human renal cell carcinoma, including cancer cells, cancer-associated fibroblasts (CAFs) and tumour-infiltrating immune cells. Using genetically engineered renal cell carcinoma assembloids with humanized mouse models, we uncovered mechanisms by which CAFs coordinate interactions between tumour cells and CD8 + T cells to maintain non-cell-autonomous CD8 + T cell stemness and drive responsiveness to anti-PD-1 therapy. These interactions operate through a tumour–CAF–T cell signalling axis in which tumour-derived WNT induces CAF expression of activin A, which enhances CD8 + T cell stemness and sensitivity to PD-1 blockade. In non-responders, we also identified a subset of WNT-unresponsive CAFs that do not produce activin A, which leads to impaired CD8 + T cell stemness and resistance to therapy. Together, these findings establish a tumour–CAF–T cell axis as a key determinant of heterogeneous responses to immune checkpoint inhibitors. Moreover, tumour assembloids provide a versatile platform for mechanistic dissection of the tumour microenvironment and evaluation of personalized immunotherapy strategies.