An assay under development can measure and evaluate circulating biomarkers called extracellular vesicles (EVs) -- early indicators of the presence of tumors -- and may give clinicians an early heads-up on the presence of hepatocellular carcinoma (HCC), the most common form of primary liver cancer, according to research published recently in Hepatology.
While EVs are released by normal cells, they are released to a greater extent by tumor cells and cells within a tumor microenvironment. Investigators at the University of California at Los Angeles (UCLA) and collaborators elsewhere have developed a streamlined surface protein assay (HCC EV SPA) capable of analyzing and quantifying eight subpopulations of HCC EVs.
Using HCC EVs may make it possible to detect early-stage HCC rapidly and affordably with high sensitivity in at-risk patients who have liver cirrhosis, wrote the researchers, including Hsian-Rong Tseng, PhD, an expert in molecular and medical pharmacology.
There were more than 30,000 deaths from primary liver cancer in the U.S. in 2021. HCC accounts for 80% to 85% of primary liver cancers, most often occurring in patients with liver cirrhosis or chronic hepatitis B virus infection.
The scientists believe the sensitivity of current surveillance methods for detecting early-stage HCC is suboptimal. Guidelines from the American Association for the Study of Liver Diseases recommend that at-risk patients undergo biannual liver ultrasound to detect HCC at a curative stage.
However, the accuracy of ultrasound imaging remains low, with sensitivity between 60% and 70% and with a specificity of 90%, meaning noninvasive tests for early detection are needed.
The scientists' streamlined HCC EV SPA can quantify eight subpopulations of HCC EVs in 400-µL plasma samples based on four HCC-associated surface protein markers and two EV markers.
A biostatistical analysis of the resulting HCC EV surface protein signatures establishes an HCC EV ECG score, making it possible to distinguish early-stage HCC from at-risk cirrhosis.
The assay uses two platform technologies: proprietary click beads, also known as methyltetrazine [mTz]-modified microbeads, that purify HCC EVs from a small volume of plasma samples; and multiplex, real-time immuno-PCR, which quantifies subpopulations of HCC EVs.
The researchers developed a statistical model based on patient gender, age, and three serum biomarkers (AFP-L3, AFP, and des-gamma-carboxy prothrombin), which was extremely sensitive in detecting HCC in phase II biomarker studies, distinguishing early-stage cancer from cirrhosis.
After the researchers optimized HCC EV SPA using artificial samples and confirmed reproducibility, 45 patients with early-stage HCC and 61 at-risk patients with liver cirrhosis took part in the phase II study. The age, gender, and ethnicity were similar among patients with HCC and the cirrhotic controls. Approximately three-quarters of those with HCC had well-compensated liver disease, compared to nearly half of the cirrhotic controls.
Among the HCC patients, 82% had liver cirrhosis. The researchers compared HCC EV ECG scores from patients with early-stage HCC to patients with other cancers. The scores from HCC patients were significantly higher than scores from patients with other cancers, confirming the specificity of HCC EV ECG scores to HCC rather than to cancers in general.
The score was validated for accurately detecting early-stage HCC from cirrhosis. The sensitivity and specificity of the assay significantly outperformed serum alpha-fetoprotein and remained consistently excellent through the subgroup analyses, according to the researchers.
Additional validation in a larger phase II multicenter biomarker study and a phase III study is needed to confirm the assay's clinical utility, they added.