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A simple blood test can tell us a lot about what is happening in our bodies, maybe even whether a tumour is starting to grow. Researchers are developing a blood test for cancer, called a liquid biopsy, that looks for parts of cancer cells in blood samples. The ultimate goal is to be able to use a blood test to detect cancer early before a tumour can grow big enough to be detected through conventional diagnosis methods.
Liquid biopsy research has made some promising advances, but it is currently limited by the need for the technology to be highly sensitive in order to detect the smallest amounts of cancer present in the blood.
Some liquid biopsy technology looks for genetic mutations unique to cancer, but these mutations are so rare that existing techniques have a hard time picking them up reliably. But cancer cells have other identifiers that could be useful. In a recent study published in the journal Nature, a team of CCS-funded researchers looked at whether detecting epigenetic changes might result in a more sensitive liquid biopsy for cancer than current methods.
Patterns of epigenetic changes act like cancer signals
Epigenetic changes alter how the genetic code is organized and “read,” but are not genetic mutations themselves. Often, a chemical group attaches to a cell’s genetic material and influences whether a particular gene is turned on or off. A specific pattern of epigenetic changes may be unique to a certain type of tumour and can be useful for identification, and maybe even diagnosis.
These epigenetic changes are found more often than genetic mutations, so they have potential to improve the sensitivity of liquid biopsies in detecting cancer.
But can researchers develop technology that picks up these patterns from bits of cells circulating in the blood, and are they an accurate readout of cancer?
Epigenetic changes could differentiate between cancer and healthy cells
The researchers in this study developed a technology to look for patterns of epigenetic changes in blood samples that signal the presence of cancer and tested whether it might be effective for early diagnosis.
They found that their liquid biopsy technology could differentiate between pancreatic cancer cells and healthy blood cells based on the patterns of epigenetic changes.
They then looked at 7 other types of cancer, including colorectal, lung and breast, to identify cancer-specific epigenetic patterns that might be useful for liquid biopsy. They found distinct patterns in the cell fragments for each cancer type, suggesting that, in the future, their approach might be able to detect and distinguish between different types of cancer, even when the cancer is at a very early stage.
Epigenetic changes could have use in liquid biopsy
The goal of diagnosing cancer through a blood sample is currently limited by the available technology. Current systems look for unique genetic mutations, but these can be uncommon in cancer cell fragments in the blood, resulting in tests that are not sensitive enough to detect early-stage cancer.
In contrast, patterns of epigenetic changes in cancer cells are still distinct from healthy cells and even between different cancer types, and they are much more common than genetic mutations. While the researchers acknowledge that their system needs to be confirmed in other sets of cells, their findings strongly suggest that it may be possible, and perhaps even advantageous, to look for these epigenetic cancer signals when doing a liquid biopsy.
Eileen Hoftyzer, BSc