Hepatocellular carcinoma (HCC) is among the leading causes of worldwide cancer‐related morbidity and mortality. Poor prognosis of HCC is attributed primarily to tumor presentation at an advanced stage when there is no effective treatment to achieve the long term survival of patients. Currently available tests such as alpha‐fetoprotein have limited accuracy as a diagnostic or prognostic biomarker for HCC. Liver biopsy provides tissue that can reveal tumor biology but it is not used routinely due to its invasiveness and risk of tumor seeding, especially in early‐stage patients. Liver biopsy is also limited in revealing comprehensive tumor biology due to intratumoral heterogeneity. There is a clear need for new biomarkers to improve HCC detection, prognostication, prediction of treatment response, and disease monitoring with treatment. Liquid biopsy could be an effective method of early detection and management of HCC. Circulating tumor cells (CTCs) are cancer cells in circulation derived from the original tumor or metastatic foci, and their measurement by liquid biopsy represents a great potential in facilitating the implementation of precision medicine in patients with HCC. CTCs can be detected by a simple peripheral blood draw and potentially show global features of tumor characteristics. Various CTC detection platforms using immunoaffinity and biophysical properties have been developed to identify and capture CTCs with high efficiency. Quantitative abundance of CTCs, as well as biological characteristics and genomic heterogeneity among the CTCs, can predict disease prognosis and response to therapy in patients with HCC. This review article will discuss the currently available technologies for CTC detection and isolation, their utility in the clinical management of HCC patients, their limitations, and future directions of research.

We report a covalent chemistry-based hepatocellular carcinoma (HCC)-specific extracellular vesicle (EV) purification system for early detection of HCC by performing digital scoring on the purified EVs. Earlier detection of HCC creates more opportunities for curative therapeutic interventions. EVs are present in circulation at relatively early stages of disease, providing potential opportunities for HCC early detection. We develop an HCC EV purification system (i.e., EV Click Chips) by synergistically integrating covalent chemistry-mediated EV capture/release, multimarker antibody cocktails, nanostructured substrates, and microfluidic chaotic mixers. We then explore the translational potential of EV Click Chips using 158 plasma samples of HCC patients and control cohorts. The purified HCC EVs are subjected to reverse-transcription droplet digital PCR for quantification of 10 HCC-specific mRNA markers and computation of digital scoring. The HCC EV-derived molecular signatures exhibit great potential for noninvasive early detection of HCC from at-risk cirrhotic patients with an area under receiver operator characteristic curve of 0.93 (95% CI, 0.86 to 1.00; sensitivity = 94.4%, specificity = 88.5%).

Hepatocellular carcinoma (HCC) is a leading cause of mortality. Checkpoint inhibitors of programmed cell death protein-1 (PD-1) and programmed death-ligand 1 (PD-L1) have shown great efficacy, but lack biomarkers that predict response. Circulating tumor cells (CTCs) have promise as a liquid-biopsy biomarker; however, data on HCC CTCs expressing PD-L1 have not been reported. We sought to detect PD-L1-expressing HCC-CTCs and investigated their role as a prognostic and predictive biomarker. Using an antibody-based platform, CTCs were enumerated/phenotyped from a prospective cohort of 87 patients with HCC (49 early-stage, 22 locally advanced, and 16 metastatic), 7 patients with cirrhosis, and 8 healthy controls. Immunocytochemistry identified total HCC CTCs (4′,6-diamidino-2-phenylindolepositive [DAPI+]/cytokeratin-positive [CK+]/clusters of differentiation 45-negative [CD45−]) and a subpopulation expressing PD-L1 (DAPI+/CK+/PD-L1+/CD45−). PD-L1+ CTCs were identified in 4 of 49 (8.2%) early-stage patients, but 12 of 22 (54.5%) locally advanced and 15 of 16 (93.8%) metastatic patients, accurately discriminating early from locally advanced/metastatic HCC (sensitivity = 71.1%, specificity = 91.8%, area under the receiver operating characteristic curve = 0.807; P < 0.001). Compared to patients without PD-L1+ CTCs, patients with PD-L1+ CTCs had significantly inferior overall survival (OS) (median OS = 14.0 months vs. not reached, hazard ratio [HR] = 4.0, P = 0.001). PD-L1+ CTCs remained an independent predictor of OS (HR = 3.22, P = 0.010) even after controlling for Model for End-Stage Liver Disease score (HR = 1.14, P < 0.001), alpha-fetoprotein (HR = 1.55, P < 0.001), and overall stage/tumor burden (beyond University of California, San Francisco, HR = 7.19, P < 0.001). In the subset of 10 patients with HCC receiving PD-1 blockade, all 5 responders demonstrated PD-L1+ CTCs at baseline, compared with only 1 of 5 nonresponders, all of whom progressed within 4 months of starting treatment. Conclusion: We report a CTC assay for the phenotypic profiling of HCC CTCs expressing PD-L1. PD-L1+ CTCs are predominantly found in advanced-stage HCC, and independently prognosticate OS after controlling for Model for End-Stage Liver Disease, alpha-fetoprotein, and tumor stage. In patients with HCC receiving anti-PD-1 therapy, there was a strong association with the presence of PD-L1+ CTCs and favorable treatment response. Prospective validation in a larger cohort will better define the utility of PD-L1+ CTCs as a prognostic and predictive biomarker in HCC. (Hepatology Communications 2020;4:1527-1540). H epatocellular carcinoma (HCC) is the fourth leading cause of cancer mortality worldwide and remains an important global health burden, with an estimated one million deaths attributable to HCC by 2030. (1) In the United States, the age-adjusted incidence of HCC has increased