Chemotherapy regimens induce inhibitory immune checkpoint protein expression on stem-like and senescent-like oesophageal adenocarcinoma cells

Use of immune checkpoint inhibitors (ICIs) with chemotherapy to enhance responses in oesophageal adenocarci-noma (OAC) is an attractive approach. We identified subpopulations of OAC cells expressing inhibitory immune checkpoint (IC) ligands (PD-L1, PD-L2 and CD160) and receptors (PD-1, TIGIT, TIM-3, LAG-3 and A2aR) in vitro and in ex vivo biopsies. Combination chemotherapy regimens FLOT and CROSS promote a more immune-resistant phenotype through upregulation of IC ligands and receptors on OAC cells in vitro . Importantly, this study investigated if OAC cells, enriched for ICs exhibited a more stem-like and senescent-like phentoype. FLOT preferentially upregulates PD-L1 on a stem-like OAC cell phenotype, defined by ALDH activity. Expression of senescence-associated ??????-galactosidase is induced in a subpopulation of OAC cells following FLOT and CROSS chemotherapy treatment, along with enhanced expression of TIM-3 and A2aR ICs. Blockade of PD-1 signalling in OAC cells induced apoptosis and enhanced FLOT and CROSS chemotherapy toxicity in vitro . Upregulation of ICs on OAC cells following chemotherapy may represent potential mechanisms of chemo-immune resistance. Combination ICIs may be required to enhance the efficacy of chemotherapy and immunotherapy in OAC patients.