Understanding how breast cancer (BC) grows in axillary lymph nodes (ALNs), and refining how therapies might halt that process, is clinically important. However, modelling the complex ALN microenvironment is difficult, and no human models exist at present. We harvested ALNs from ten BC patients, and perfused them at 37 °C ex vivo for up to 24 h. Controlled autologous testing showed that ALNs remain viable after 24 h of ex vivo perfusion: haematoxylin and eosin-stained histological appearance and proliferation (by Ki67 immunohistochemistry) did not change significantly over time for any perfused ALN compared with a control from time-point zero. Furthermore, targeted gene expression analysis (NanoString Pancancer IO360 panel) showed that only 21/750 genes were differentially expressed between control and perfused ALNs (|log2 FC| > 1 and q < 0.1): none were involved in apoptosis and metabolism, but rather all 21 genes were involved in immune function and angiogenesis. During perfusion, tissue acid-base balance remained stable. Interestingly, the flow rate increased (p < 0.001) in cancer-replaced (i.e metastasis occupied >90% of the surface area on multiple levels) compared to cancer-free nodes (i.e. nodes with no metastasis on multiple sections). CXCL11 transcripts were significantly more abundant in cancer-replaced nodes, while CXCL12 transcripts were significantly more abundant in cancer-free nodes. These cytokines were also detected in the circulating perfusate. Monoclonal antibodies (nivolumab and trastuzumab) were administered into a further three ALNs to confirm perfusion efficacy. These drugs saturated the nodes; nivolumab even induced cancer cell death. Normothermic ALN perfusion is not only feasible but sustains the tumour microenvironment ex vivo for scientific investigation. This model could facilitate the identification of actionable immuno-oncology targets. This article is protected by copyright. All rights reserved.
Lymph node metastasis, breast cancer, immuno-oncology, normothermic perfusion