Identification of 144 elevated phosphoproteins indicative of cancer shows one possible path forward in the use of liquid biopsies for early detection of cancer and monitoring patients in remission
While precision medicine and a growing menu of medical laboratory assays and diagnostics are increasing the number of treatment methods available to cancer patients, early detection is still key to improving outcomes and increasing the odds of survival.
In February 2017, a Dark Daily ebriefing titled, “British Medical Laboratory Test for Early Screening of Lung Cancer Shows Promising Interim Results in Large Trial; Could Lead to Other Simple Blood Tests for Cancer Detection,” showcased the EarlyCDT-Lung test. In a University of Dundee press release, researchers noted the non-invasive test promised detection of lung cancer “potentially up to five years” earlier than traditional scans.
Now, researchers from Purdue University are testing a non-invasive blood test for detection of all types of cancer using phosphoproteins as biomarkers that could detect cancer even before the onset of any symptoms. This could lead to non-invasive therapies, and ways to monitor them, that could be applied while the patient’s body is still strong and able to respond well to treatment.
Speaking with New Atlas, researcher W. Andy Tao, PhD, Chief Scientific Officer of Tymora Analytical Operations, stated, “This is definitely a breakthrough, showing the feasibility of using phosphoproteins in blood for detecting and monitoring diseases.”
Extracellular Vesicles as the Key to Isolating Phosphoproteins
Protein phosphorylation—particularly mutations in phosphatases and kinases—are already known to play roles in cancer development as noted in the OncLive article “Phosphorylation: The Master Switch of the Cell.”
However, as the liver uses phosphatase to dephosphorylate proteins, identification of phosphoproteins in the blood has remained difficult for researchers.
Isolating phosphoproteins from tissue samples is equally difficult. “Assays of phosphoproteins from tissues face tremendous challenges because of the invasive nature of tissue biopsy and the highly dynamic nature of protein phosphorylation during the typically long and complex procedure of tissue biopsy,” noted I-Hsuan Chen, PhD Candidate, and W. Andy Tao, PhD, in their study published in Proceedings of the National Academy of Sciences of the United States of America (PNAS).
As shown in the illustration above, extracellular vesicles are basically blobs of cellular cytosol that contain microRNA (miRNA) Messenger RNA (mRNA) and proteins, which some researchers believe potentially could compete with stem cell-based therapeutics. (Image copyright: BioProcess Intl.)
In their attempts, researchers instead focused on the biomarker discovery potential of extracellular vesicles (EV)—in particular microvesicles and exosomes—citing strong evidence in the ability to use EV-based disease biomarkers well before symptoms appear.
“The ability to detect the genome output (active proteins, and in particular phosphoproteins) can provide more direct real-time information about the organism’s physiological function and disease progressions, particularly in cancers,” the PNAS study authors noted.
Researchers isolated nearly 2,400 phosphoproteins across 30 samples from breast cancer patients. They then compared these to six control samples and identified 144 specific proteins commonly elevated when cancer was present.
In a Purdue University press release, Timothy Ratliff, PhD, Director of Purdue University Center for Cancer Research expanded on the findings of the study, stating, “The vesicles and exosomes are present and released by all cancers, so it could be that there are general patterns for cancer tissues, but it’s more likely that [W. Andy Tao, PhD] will develop patterns associated with different cancers.”
Monitoring Cancer with a Blood-Based Cartridge Diagnostic
The Purdue University press release highlights the potential of the process, noting, “A simple blood test for cancer would be far less invasive than scopes or biopsies that remove tissue. A doctor could also regularly test a cancer patient’s blood to understand the effectiveness of treatment and monitor patients after treatment to see if the cancer is returning.”
The ability to capture EV phosphoproteins appears to be stable over time. The samples used in the Perdue University study were taken nearly five years ago by the Indiana Biobank.
While the stability of samples is a boon to researchers, they note that there are still many improvements to be made to the methods used before some medical laboratories could attempt to replicate their results.
Current methods require using differential high-speed and ultra-high-speed centrifugation. Study authors note this makes it less than ideal for clinical laboratory use due to lack of access and lower specificity.
However, the Purdue press release also notes plans for future improvements. Tymora Analytical Operations is developing technologies to use the biomarkers in a cartridge-based system. This could mean that pathology groups and medical laboratories might one day add an automated test to their menus for the second leading cause of death in the United States.
Until then, medical laboratories can help further efforts by collecting samples and working with biobanks, such as the one used in the Purdue study. Clinical laboratories already power much of the diagnostic tools driving innovation and discovery in oncological precision medicine. With the addition of a way to detect cancers, both while in remission or before symptoms appear, laboratories could further increase their role in fighting this worldwide killer.
—Jon Stone
Related Information:
Protein Discovery Points to Potential Blood Test for All Cancers
Phosphoproteins in Extracellular Vesicles as Candidate Markers for Breast Cancer
Breakthrough Discovery May Make Blood Test Feasible for Detecting Cancer
Phosphorylation: The Master Switch of the Cell
Overview of Protein Phosphorylation
