Danish researchers have created a new blood test capable of accurately detecting multiple types of cancer at all stages of progression.
The method is based on the remarkable 2015 discovery – made by the same team – that a protein naturally produced by the malaria parasite will bind to a distinct version of a surface protein that is present on 95 percent of cancer cells (ofCS). To translate this into a laboratory test, they took a synthetical version of the malaria protein – rVAR2 – and fused it with a tiny magnetic bead. When added to a blood sample, the resulting complex sticks to free-floating malignant cells known as circulating tumor cells (CTCs), allowing clinicians to easily isolate CTCs from healthy cells and other blood components and gather them for diagnostic analyses using a magnet.
Though large replication studies will need to be performed, results from the team’s latest study, published in Nature Communications, suggest that the test has the potential to not only catch cancer before it spreads (stage I), but may also identify when a patient is in the incredibly hard-to-detect later phase, wherein cells from the primary tumor have just switched into invasive migratory mode but have not yet settled in new locations to form secondary tumors. Metastatic cancer is responsible for roughly 90 percent of all cancer-related deaths, translating to a yearly toll of approximately 7.4 million people worldwide.
"We have developed a method where we take a blood sample and with great sensitivity and specificity, we're able to retrieve the individual cancer cells from the blood,” lead author Ali Salanti said in a statement. “We catch the cancer cells in greater numbers than existing methods, which offers the opportunity to detect cancer earlier and thus improve outcome.”
Salanti and his colleagues performed a series of experiments to assess how well the rVAR2 platform could capture cells from breast, prostate, colorectal, lung carcinoma, osteosarcoma, and melanoma cell lines. The results confirmed that rVAR2 does indeed bind to all these cancer types while essentially ignoring the myriad of normal circulating cells present in a blood sample. However, it was most efficient at capturing CTCs from liver, lung, and pancreatic carcinoma patients.
Demonstrating the platform’s impressive efficiency, the team added 10 isolated pancreatic cancer cells to several 5-mL samples of healthy blood (a volume that contains roughly 25 billion red blood cells and 35 million white blood cells). The rVAR2 captured eight or nine of the cells each time.
Salanti’s team has already further tested the platform’s diagnostic value in a large study of pancreatic cancer patients, and they hope that future work will validate it as a tool for staging the disease.
"Today, it's difficult to determine which stage cancer is at," said Salanti. "Our method has enabled us to detect cancer at stages one, two, three and four. Based on the number of circulating tumour cells we find in someone's blood, we'll be able to determine whether it's a relatively aggressive cancer or not so then to adjust the treatment accordingly.”
The currently available CTCs detection tests use antibodies that bind to other types of cancer-associated cell surface proteins, yet not all forms of cancer have these markers, and some of the platforms bind to a high-number of non-cancerous cells.