Overcoming immunotherapy resistance in hepatocellular carcinoma by targeting myeloid IL-8/CXCR2 signaling

Durable responses to immune checkpoint blockade (ICB) in hepatocellular carcinoma (HCC) are limited to a minority of patients, yet reliable biomarkers are still lacking. Inflammatory cytokines such as interleukin-8 (IL-8) are associated with HCC progression, and IL-8 is known as the chemoattractant for immunosuppressive myeloid cells. Therefore, we aim to elucidate the ICB resistance mechanisms mediated by the activation of the IL-8/CXCR2 pathway. Single-cell RNA sequencing (scRNA-seq) was performed in advanced HCC patients with baseline and on-treatment biopsy after pembrolizumab in a phase 2 clinical trial cohort. Our data revealed that IL-8 and its receptor, CXCR2, mainly derived from immunosuppressive myeloid-derived suppressor cells (MDSCs). In particular, the high circulating IL-8 level was strongly associated with poor ICB response. This myeloid IL-8/CXCR2 pathway was further elucidated in our ICB-resistant orthotopic mouse model using AZD5069, a clinically available CXCR2 antagonist. Suppression of the IL-8/CXCR2 pathway significantly abrogated MDSC trafficking and immunosuppressive activity, which sensitized the anti-PD-L1 blockade to reduce tumor growth and prolong survival. The association between myeloid IL-8 and ICB therapeutic outcomes also extended to multiple cancer types. Collectively, our study not only suggests a potential non-invasive biomarker for patient stratification and monitoring of ICB response but it also provides a proof of concept for combinational immunotherapy to benefit patients who are non-responsive to ICB monotherapy.