A microfluidic tumor-on-chip platform deciphers hypoxia-driven FOXO3a/PD-L1 signaling in gastric cancer immunotherapy resistance

Hypoxia represents a common feature within the microenvironment of various cancerous tumors, which suppresses tumor immunogenicity. Immunotherapy, particularly based on immune checkpoint inhibitors, significantly alters the prognosis of certain tumors and reveals the presence of intrinsic or acquired resistance. Presently available platforms, however, cannot efficiently recapitulate the in vivo tumor microenvironment and elucidate the mechanisms of hypoxia-induced immunotherapy resistance in tumors. In this study, a microfluidic tumor-on-chip model is employed to investigate immunotherapy resistance in gastric cancer (GC) cells within a hypoxic microenvironment. Unlike traditional methods, this chip accurately and efficiently replicates the in vivo tumor hypoxic microenvironment. This microfluidic platform demonstrates the upregulation of the forkhead box O3 (FOXO3a) under hypoxic conditions, subsequently activating downstream programmed cell death ligand-1 (PD-L1) expression, ultimately leading to immunotherapy resistance. In a syngeneic mouse model, FOXO3a deficiency restores sensitivity to immunotherapy by enhancing immune cell enrichment. In clinical samples, FOXO3a levels and the prognosis of patients with gastric cancer receiving immunotherapy are correlated. In summary, by constructing a novel microfluidic chip, the in vivo tumor microenvironment can be efficiently simulated, uncovering the pivotal role of FOXO3a in immunotherapy resistance in gastric cancer.