EV-based Liquid Biopsy for the Diagnosis of Early-Stage Liver Cancer

Detecting cancer at early stages significantly increases patient survival rates. Because lethal solid tumors often produce few symptoms before progressing to advanced, metastatic disease, diagnosis frequently occurs when surgical resection is no longer helpful. One promising approach to detect early-stage, curable cancers uses biomarkers present in circulating extracellular vesicles.

Extracellular vesicles (EVs) are 40 to 200 micron cell-derived vesicles which play a critical role in cell-to-cell communication, and disease progression. These vesicles, which are present in all biological fluids, contain a wide variety of molecular species such as RNA, DNA, proteins, and lipids from their origin cells, offering a good source of biomarkers.

The clinical relevance of EVs has remained largely undetermined, partially owing to challenges in EV analysis. Nonetheless, EVs, which contain molecules that are reflective of the cell type of origin, are increasingly being recognized as important vehicles of communication between cells and as promising diagnostic and prognostic biomarkers in cancer. Despite this huge clinical potential, the wide variety of methods for separating EVs from biofluids, which provide material of highly variable purity, and the lack of knowledge regarding methodological reproducibility have slowed the entry of EVs into the clinical arena.

Hepatocellular carcinoma (HCC) is the most common form of liver cancer and is usually undetectable until it reaches an advanced stage, when it is usually fatal. Currently, the best available screening method for at-risk patients is ultrasound imaging of the liver. However, ultrasound testing can be expensive and time-consuming, putting it out of reach of many patients, and the tests often miss smaller, early-stage tumors that could be curable.

In this regard, a major improvement in liver cancer diagnostic technique, based on liquid biopsy of cancer-related extracellular vesicles, was described recently by investigators at the Ceders-Sinai Medical Center (Los Angeles, CA, USA).

The investigators used tissue microarray to evaluate four potential HCC-associated protein markers. In addition, an HCC EV Surface Protein Assay, comprised of covalent chemistry-mediated HCC EV purification and real-time immuno-PCR readouts, was developed and optimized for quantifying subpopulations of EVs.

An HCC EV ECG score, calculated from the readouts of three HCC EV subpopulations was established for detecting early-stage HCC. Subsequently a phase II biomarker study was conducted to evaluate the performance of ECG score in a training cohort of 106 patients and an independent validation cohort of 72 patients.

Results revealed that 99.7% of tissue microarrays stained positive for at least one of the four HCC-associated protein markers, which were subsequently validated in HCC EVs. In the training cohort, the HCC EV ECG score demonstrated an area under the receiver operating curve of 0.95 for distinguishing early-stage HCC from cirrhosis with a sensitivity of 91% and a specificity of 90%.

“Most at-risk patients are not screened,” said contributing author Dr. Ju Dong Yang, medical director of the Liver Cancer Program at Cedars-Sinai Medical Center. “They struggle to get insurance authorizations and contact the imaging center, and then show up to have the test done—and the test’s accuracy can be limited, particularly in patients with obesity or more advanced liver disease. This is where a screening blood test becomes increasingly valuable. This important work could fill an unmet need for a more user-friendly, more accurate screening test that detects liver cancer early and saves lives. We are the first team looking at extracellular vesicles as a detection biomarker for early-stage liver cancer, and our study showed it had outstanding performance. We are planning on doing larger-scale studies to further validate this test and bring it into routine clinical practice here—and globally.”

The EV-based liquid biopsy for early detection of liver cancer was described in the July 31, 2022, online edition of the journal Hepatology.

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Ceders-Sinai Medical Center