Evaluation of hepatocellular carcinoma circulating tumor cells expressing programmed death-ligand 1

Abstract

Background: Hepatocellular carcinoma (HCC) often presents in advanced stages with limited treatment options. Immunotherapies employing checkpoint inhibition between programmed cell death protein-1 (PD-1) and programmed death-ligand 1 (PD-L1) have shown promise in treating advanced HCC. While enumeration of HCC circulating tumor cells (CTCs) expressing cytokeratin (CK) has been associated with prognosis, data on HCC CTCs expressing PD-L1 have not been reported. We sought to detect PD-L1 expressing HCC CTCs, and investigate its role as a prognostic biomarker. Methods: We utilized a microfluidic, antibody-based platform to enumerate and phenotype CTCs from 4mL of peripheral blood in a prospective cohort of 92 patients (8 healthy control, 11 non-malignant liver disease, 73 HCC). Immunocytochemical staining identified total HCC CTCs (DAPI+/CK+/CD45−) and a subpopulation expressing PD-L1 (DAPI+/CK+/PD-L1+/CD45−). CTC number and phenotype were correlated with clinicopathologic data. Results: CK+ CTCs were detected in 96% of HCC patients (mean = 7, range = 0−27), and discriminated HCC and non-HCC patients (≥2 CK+ CTCs, AUROC = 0.92, sensitivity = 90.4%, specificity = 84.1%, p < 0.0001). PD-L1+ CTCs discriminated HCC patients with early stage (3/39 had PD-L1+ CTCs) and advanced/metastatic disease (23/34 had PD-L1+ CTCs; AUROC = 0.79, sensitivity = 67.7%, specificity = 92.3%, p < 0.0001; Figure). Of 6 patients receiving anti-PD1 therapy, the 3 demonstrating response all had PD-L1+ CTCs, compared to only 1 of 3 non-responders. Conclusion: To our knowledge, this is the first report evaluating PD-L1+ CTCs in HCC, which accurately discriminate early and advanced stage HCC, and are associated with response to immunotherapy. Further studies with more patients are necessary to determine if PD-L1 CTC phenotype may help guide selection of patients likely to benefit from immune checkpoint inhibitors.