We catch single cancer cells in the blood
A lab on a chip detects metastasis at the very beginning of cancer development
Roman Ivanov, ComputerEven in the early stages of cancer, individual cancer cells enter the bloodstream and spread throughout the body.
In certain unfortunate cases, they cause metastases. The most unpleasant thing is that, as, for example, in the case of breast cancer, these freely circulating cells may differ from the original cells forming the tumor (this type of cancer is able to produce stem cancer cells resistant to radio and chemotherapy), which allows them to survive treatment and later cause remission of the disease.
That is why it is so important to be able to detect these cells in the blood, isolate and study them at any stage of the development of the disease. In an article published in the journal Angewandte Chemie (Schiro et al., Sensitive and High-Throughput Isolation of Rare Cells from Peripheral Blood with Ensemble-Decision Aliquot Ranking), experts from the University of Washington (USA) report on a method they developed based on a "laboratory on a chip" and allows detecting and isolating even very small concentrations of cancer cells in the blood.
Detecting freely circulating cancer cells is a complex task that requires finding minuscule amounts of them (say, ten cells per milliliter of blood). Daniel T. Chiu and colleagues have developed a microfluidic system that needs just one milliliter of blood sample and 20 minutes of operation. At the same time, an already small sample is divided into many very small aliquots (portions), each of which is analyzed for the presence of cells of a certain type.
The blood sample is initially labeled with fluorescent markers that specifically bind to certain cancer cells. Then it is passed through a system of microchannels, where it passes through the zone irradiated by the laser. The size of the latter determines the volume of elementary aliquots (approximately 2 nl). If there is a cancer cell marked with a fluorescent marker in the aliquot, the laser beam will lead to the observed light emission. Thus, the very fact of the presence of one or more types of specific cancer cells is determined. Further, if the aliquot is fluorescent (positive), it is sent to a channel other than the one into which the non-fluorescent portions merge. That is, all positive aliquots fall into the filtration chamber. Red blood cells and the vast majority of other blood cells pass through the filter, while larger tumor cells are delayed. Now the isolated cancer cells can be counted directly on the filter, examined under a microscope and collected with micropipettes for further more thorough examination. Using the second marker, it is possible to identify certain groups of cancer cells, such as cancer stem cells.
Test experiments with blood containing a known number of breast cancer cells demonstrated the accuracy of the technique in determining the number of cancer cells at the level of 93% with zero false positive result.
The researchers believe that the technology they have developed will show itself perfectly when monitoring therapy, examining the patient's condition after discharge, as well as early detection of the disease.
Prepared based on the materials of ChemistryViews: Finding Cancer Cells in Blood.
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05.03.2012