Digital assay of circulating tumor cells may improve diagnosis, monitoring of liver cancer

January 19, 2017, Massachusetts General Hospital

Use of an advanced form of the commonly used polymerase chain reaction (PCR) method to analyze circulating tumor cells (CTCs) may greatly increase the ability to diagnose early-stage cancer, increasing the likelihood of successful treatment. In their report published in PNAS, a team from the Massachusetts General Hospital (MGH) Cancer Center describe how combining use of the MGH-developed CTC-iChip with RNA-based digital PCR greatly improved detection of cancer cells in the blood of patients with hepatocellular carcinoma (HCC), the most common type of liver cancer.

"We have developed an assay capable of detecting a single cell within a background of the tens of billions of cells that comprise whole blood," says Mark Kalinich of the MGH Cancer Center, co-lead author of the PNAS report. "Our test provides highly specific detection of cancer in patients with HCC, compared with healthy individuals and with those at high risk for developing the disease. These results hold promise for both the early detection of HCC and for the monitoring of treatment over time."

Liver cancer, including HCC, is the second highest cause of cancer death in the world. HCC is particularly prevalent in developing countries, where its incidence is driven by infection with the hepatitis B virus, which now affects more than 248 million individuals. In developed countries, conditions like hepatitis C infection and alcohol abuse are also increasing the prevalence of HCC. Early diagnosis of the tumor can lead to five-year survival rates of from 50 to 80 percent, but once HCC has spread, survival drops to around 15 percent.

Current blood-based strategies for detecting HCC, such as serum levels of alpha-fetoprotein (AFP), have had poor results. New technologies enabling the isolation and analysis of CTCs have been valuable research tools and can help track treatment response, but the use of microscopy to identify and analyze CTCs required the time-consuming development of specific protocols for particular forms of cancer. While standard PCR is a technique for generating many copies of a specific nucleic acid segment of DNA, digital PCR allows much more precise measurement of the quantity of a given nucleic acid segment in a sample of CTCs.

The research team developed their digital PCR assay by first identifying 10 specific RNA transcripts that were expressed in HCC cells but not in blood components. Using the CTC-iChip developed at the MGH Center for Engineering in Medicine, they assayed from six groups of individuals:

* newly diagnosed HCC patients;

* HCC patients receiving treatment who still had evidence of disease;

* HCC patients who appeared to be cured after surgical treatment, including liver transplantation;

* patients at risk for developing HCC because of other chronic liver diseases;

* patients with other types of cancer, including some with liver metastases;

* healthy volunteers.

Digital PCR analysis revealed significantly higher levels of the HCC-associated RNA transcripts in blood samples from patients with HCC than from those with other cancers, with chronic liver disease or healthy controls. Use of a CTC score based on the 9 RNA transcripts most significantly associated with HCC generated positive results for more than half of those with untreated HCC but only around 8 percent of healthy controls and 3 percent of those with other liver diseases. Around 28 percent of patients currently being treated had positive scores, and the percentage of positive scores among patients with no evidence of disease after treatment was similar to that of healthy controls.

Follow up with a small group of patients produced evidence suggesting the potential of the CTC score to monitor treatment response. Scores remained high in two patients who had not been treated between blood draws, while the scores of two other patients dropped after surgical tumor removal. Another patient's score dropped precipitously after treatment with a checkpoint inhibitor and then showed significant further reduction after a radioembolization procedure that greatly reduced the size of the tumor.

To determine whether CTC scoring could improve the inadequate results of AFP screening, the researchers used both methods to analyze blood samples from 15 newly diagnosed patients. In four of them, the presence of HCC was indicated by CTC score alone; AFP alone detected cancer that the CTC score did not in one patient, and the results of both tests were able to detect HCC in another five. Overall, either CTC score, AFP or both produced positive results in 67 percent of patients, missing the diagnosis in only one third.

While previous studies combining AFP with more specific assays like ultrasound have improved diagnosis of at-risk patients, leading to a 37 percent drop in mortality, the authors note that ultrasound results can be compromised in with obesity or cirrhosis and that high-quality ultrasound may not be available in the developing countries where the risk of HCC is highest.

"Although there are major hurdles to global implementation of CTC-based digital PCR to screen for HCC, we believe they are surmountable," says Kalinich, who is an MD/ PhD candidate at Harvard Medical School. "With the blood stabilization techniques currently being developed in Mehmet Toner's lab at the Center for Engineering in Medicine, blood draws from anywhere in the world could be analyzed at central processing facilities, enabling the high throughput required for global screening efforts." He notes that further study is required to confirm the ability of this assay to detect HCC in a large-scale trial, expand the number of HCC-related RNA transcripts to further improve diagnostic accuracy, and determine whether this approach can help detect and monitor treatment for other forms of cancer.

Explore further: New model could benefit liver cancer transplant patients

More information: Mark Kalinich et al, An RNA-based signature enables high specificity detection of circulating tumor cells in hepatocellular carcinoma, Proceedings of the National Academy of Sciences (2017). DOI: 10.1073/pnas.1617032114

Related Stories

New model could benefit liver cancer transplant patients

December 21, 2016
A simple blood test may better predict which patients diagnosed with liver cancer will experience disease recurrence, according to new research from Weill Cornell Medicine scientists. The findings may help physicians determine ...

Outreach to cirrhosis patients doubles early screening rates for deadly liver cancer

November 18, 2016
Proactive outreach to cirrhosis patients in a safety net health system successfully doubled their screening rates for liver cancer, UT Southwestern Medical Center researchers found.

Blood-born molecules could predict those who will develop liver cancer

June 6, 2016
Hepatocellular carcinoma, the most common type of liver cancer, is increasing in incidence in the United States, and infection with the Hepatitis B virus (HBV) causes about 50 percent of cases. However, it can be difficult ...

Successful treatment for hepatitis C reduces risk of liver cancer later in veterans

April 25, 2016
A new study by researchers at Baylor College of Medicine found that treatment and cure of chronic hepatitis C reduce the risk of hepatocellular carcinoma (HCC), especially if given early, before cirrhosis develops, and while ...

Tumor cells in the blood may indicate poor prognosis in early breast cancer

May 15, 2014
Tumor cells in bone marrow of early breast cancer patients predict a higher risk of relapse as well as poorer survival, but bone marrow biopsy is an invasive and painful procedure. Now, it may be possible to identify tumor ...

Breast cancer cells found to switch molecular characteristics

August 24, 2016
A study led by Massachusetts General Hospital (MGH) investigators reveals how spontaneous changes in the molecular characteristics of tumors can lead to tumors with a mixed population of cells requiring treatment with several ...

Recommended for you

Daily low-dose aspirin may be weapon against ovarian cancer

July 20, 2018
(HealthDay)— One low-dose aspirin a day could help women avoid ovarian cancer or boost their survival should it develop, two new studies suggest.

Discovery of kidney cancer driver could lead to new treatment strategy

July 19, 2018
University of North Carolina Lineberger Comprehensive Cancer Center scientists have uncovered a potential therapeutic target for kidney cancers that have a common genetic change. Scientists have known this genetic change ...

High fruit and vegetable consumption may reduce risk of breast cancer, especially aggressive tumors

July 19, 2018
Women who eat a high amount of fruits and vegetables each day may have a lower risk of breast cancer, especially of aggressive tumors, than those who eat fewer fruits and vegetables, according to a new study led by researchers ...

Sunscreen reduces melanoma risk by 40 per cent in young people

July 19, 2018
A world-first study led by University of Sydney has found that Australians aged 18-40 years who were regular users of sunscreen in childhood reduced their risk of developing melanoma by 40 percent, compared to those who rarely ...

Analysis of prostate tumors reveals clues to cancer's aggressiveness

July 19, 2018
Using genetic sequencing, scientists have revealed the complete DNA makeup of more than 100 aggressive prostate tumors, pinpointing important genetic errors these deadly tumors have in common. The study lays the foundation ...

Complementary medicine for cancer can decrease survival

July 19, 2018
People who received complementary therapy for curable cancers were more likely to refuse at least one component of their conventional cancer treatment, and were more likely to die as a result, according to researchers from ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.