Most cancers keep a low profile and become fatal, causing no symptoms until they are too advanced to treat. Ovarian and gastroesophageal cancers are among the most notorious progressions for this disease, often leading to late-stage diagnosis.
Now an international team of researchers from Rockefeller University’s Laboratory of Cellular and Structural Biology has developed a highly sensitive blood test that can detect a key protein produced by cancer cells that shows promise for early detection. The results were published recently Cancer discovery.
Unlike many cancer tests that are limited in scope, expensive, or rely on invasive tissue sampling, this new method is a low-cost, multi-cancer detector that can pick up the presence of a telltale protein known as LINE-1-ORF1p. , a small amount of blood in less than two hours.
The test has breakthrough potential as an early diagnostic test for life-threatening cancers. These types of ultrasensitive detection devices are poised to improve patient outcomes in transformative ways.”
Michael P. Rout, head of Rockefeller Lab
Genetic copy and paste
Cancer biomarker identification is a young and growing field. There are a number of such biomarkers, but they may come with drawbacks. Some require a surgical biopsy. Others are employed only after the onset of symptoms, which may be too late for effective intervention. Most are normal human proteins that have variability from person to person, making it difficult to interpret a single value. And many are targeted to a specific cancer, narrowing their range.
But recently, an important new biomarker for earlier detection may have emerged. The protein, known as Line-1 ORF1p, came on the radar of researchers about a decade ago. Line-1 is a retrotransposon, a virus-like element present in every human cell that replicates through a copy-and-paste process, resulting in a new copy at a new location in the genome. ORF1p is a protein that is overexpressed in cancer.
“Transposons are normally expressed in sperm and eggs and during embryogenesis, so there are situations where you have non-pathobiological expression of the transposon,” said Rockefeller Research Associate Professor John LaCava, co-author of the paper, who specializes in LINE-1 research. . “But otherwise, these ‘jumping genes’ remain silent in the genome, as their activity causes stress and insults to the cell.”
Most of the time, the body keeps Line-1 under control. “There are layers of mechanisms that prevent Line-1 from being expressed and producing ORF1p, so we can use the presence of the protein as a proxy for an unhealthy cell that no longer has control over the transcriptome,” notes LaCava. “You shouldn’t find ORF1p in a healthy person’s bloodstream.”
Over the past five years, he added, “it has become abundantly clear that these proteins are highly elevated in most cancers,” including many of the most common and most deadly cancers of the esophagus, colon, lung, breast, prostate, ovary, uterus, pancreas, head. and the neck.
Because carcinoma cells produce ORF1p early in the course of the disease, researchers have long sought a sensitive, accurate test to detect ORF1p as early as possible. The ability to detect cancer in patients before it spreads could potentially save lives.
Very sensitive test
The Rockefeller researchers worked with principal investigators at Harvard University’s Brigham, Mass. General Institute for Biologically Inspired Engineering, and the Dana-Farber Cancer Institute, among other partner institutions, to engineer a rapid, low-cost test capable of detecting ORF1p. Plasma, which accounts for more than half of the components of human blood.
The new study used a single-molecule-based detection technology known as SIMOA that was developed by co-author David Walt of Harvard. The Rockefeller team used custom nanobodies derived from llamas and engineered as capture reagents that trap the ORF1p protein and act as sensitive probes to detect it.
“We developed these reagents as part of our mission to capture and describe the molecular interactions of ORF1p with other proteins in colorectal cancer,” LaCava said. “We knew that most colorectal cancers have large amounts of LINE-1 proteins, so we reasoned that the interactions they create deregulate normal cell functions in a way that benefits the cancer. Interactions. Later, it became clear that our collaborators at Harvard were developing their biomarker assay. can use the same reagents for , so we shared them.”
The researchers found that the test was highly accurate in detecting ORF1p in blood samples from patients with various types of cancer, including ovarian, gastroesophageal and colorectal cancer. It costs less than $3 to produce and gives fast results.
“We were shocked by how well this test worked across cancer types,” said lead author Martin Taylor of Massachusetts General Hospital’s Department of Pathology.
The researchers also analyzed plasma from 400 healthy people aged 20-90 who donated blood to the Mass General Brigham Biobank; ORF1p is undetectable in 97–99% of them. Of the five men who had detectable ORF1p, the man with the highest levels was found to have progressed to prostate cancer six months later.
Beware of the spikes
Another potential use of the assay is to monitor how a patient is responding to cancer therapy. If a treatment is effective, the ORF1p level in the patient’s blood should decrease, LaCava says. In one part of the study, researchers studied 19 patients treated for gastroesophageal cancer; In 13 people who responded to treatment, ORF1p levels dropped below the detection limit of the assay.
Protein tracking could potentially be incorporated into routine health care, LaCava says. “At a healthy point in your life, you can measure your ORF1p levels to establish a baseline. Then your doctor will just watch for any spikes in ORF1p levels, which may indicate changes in your health status. Although there may be some small ORF1p fluctuations here and there , a spike would cause a deeper investigation.”
Lama to doctor
The study results also illustrate the enormous potential of nanobody reagents generated through the study of interatomics, Rout said. Interactomics seeks to understand the dynamic interactions of a cell’s millions of individual components, particularly its proteins and nucleic acids. These interactions form macromolecular complexes that transmit information and regulate cellular behavior. Pathogenic changes in these interactions underlie all diseases.
“There is an urgent need for better tools to reveal and isolate interactomes that is only just beginning to be met,” says Rout. “To that end, we often collaborate with other institutions in the development of reagents like our llama-derived nanobodies. The resulting products are not merely research tools; they have great potential in the hands of doctors.”