Human implantable tertiary lymphoid organs (TLO) for solid tumor therapy: from organ chips to the clinic?

We previously created an in vitro human TLO model from patient-derived, circulating immune cells using organ-on-a-chip devices and 3D culture in extracellular matrix (ECM). B cells in these TLOs express activation induced cytidine deaminase, which is only expressed in lymphoid tissues and is required for class switching and somatic hypermutation (SHM). When challenged by vaccines, these TLO undergo SHM and produce antigen-specific antibodies and CD8 T cells. To model cancer associated TLOs, we integrated human  pancreatic and lung cancer cell lines into these TLO Chips to understand how the immune context of hot and cold tumors differentially impacts TLO formation. The high PDL1/L2 expressing lung cancer cell line that displayed a “hot” phenotype in published murine studies induced high levels of cytokines and stimulated increased TLO formation in the lymphoid Organ Chip. In contrast, the cold, low PDL1/L2 expressing lung and pancreatic cell lines did not induce this cytokine signature or TLO formation. Importantly, TLO assembly correlated with increased B cell activation, anti-tumor CD8 activity, and tumor cell death. When the same mix of immune cells and ECM was injected in humanized mice bearing subcutaneous tumors from the hot lung cancer cell line, new lymphoid tissue containing dense aggregates of T and B cells was induced, showing for the first time that direct injection of synthetic TLOs at the tumor site may offer an alternative form of therapy for solid tumors.