Tenfold boost in ability to pinpoint proteins in cancer cells
Better diagnosis and treatment of cancer could hinge on the ability to better understand a single cell at its molecular level. New research offers a more comprehensive way of analysing one cell’s unique behaviour, using an array of colours to show patterns that could indicate why a cell will or won’t become cancerous.
A University of Washington team has developed a new method for colour-coding cells that allows them to illuminate 100 biomarkers, a ten-time increase from the current research standard, to help analyse individual cells from cultures or tissue biopsies.
‘Discovering this process is an unprecedented breakthrough for the field,’ said corresponding author Xiaohu Gao, a UW associate professor of bioengineering. ‘This technology opens up exciting opportunities for single-cell analysis and clinical diagnosis.’
The research builds on current methods that use a smaller array of colours to point out a cell’s biomarkers – characteristics that indicate a special, and potentially abnormal or diseased, cell. Ideally, scientists would be able to test for a large number of biomarkers, then rely on the patterns that emerge from those tests to understand a cell’s properties.
The UW research team has created a cycle process that allows scientists to test for up to 100 biomarkers in a single cell. Before, researchers could only test for 10 at a time.
The analysis uses quantum dots, which are fluorescent balls of semiconductor material. Quantum dots are the smaller version of the material found in many electronics, including smartphones and radios. These quantum dots are between 2 and 6 nanometers in diameter, and they vary on the colour they emit depending on their size.
Cyclical testing hasn’t been done before, though many quantum dot papers have tried to expand the number of biomarkers tested for in a single cell. This method essentially reuses the same tissue sample, testing for biomarkers in groups of 10 in each round.
‘Proteins are the building blocks for cell function and cell behaviour, but their makeup in a cell is highly complex,’ Gao said. ‘You need to look at a number of indicators (biomarkers) to know what’s going on.’
The new process works like this: Gao and his team purchase antibodies that are known to bind with the specific biomarkers they want to test for in a cell. They pair quantum dots with the antibodies in a fluid solution, injecting it onto a tissue sample. Then, they use a microscope to look for the presence of fluorescent colours in the cell. If they see particular quantum dot colours in the tissue sample, they know the corresponding biomarker is present in the cell.
After completing one cycle, Gao and co-author Pavel Zrazhevskiy, a UW postdoctoral associate in bioengineering, inject a low-pH fluid into the cell tissue that neutralises the colour fluorescence, essentially wiping the sample clean for the next round. Remarkably, the tissue sample doesn’t degrade at all even after 10 such cycles, Gao said.
For cancer research and treatment, in particular, it’s important to be able to look at a single cell at high resolution to examine its details. For example, if 99 percent of cancer cells in a person’s body respond to a treatment drug, but 1 percent doesn’t, it’s important to analyse and understand the molecular makeup of that 1 percent that responds differently.
‘When you treat with promising drugs, there are still a few cells that usually don’t respond to treatment,’ said Gao. ‘They look the same, but you don’t have a tool to look at their protein building blocks. This will really help us develop new drugs and treatment approaches.’ University of Washington
