DNA dabbles

What is Liquid biopsy?? It is a technique for analyzing blood and other bodily fluids, for diagnosing and monitoring diseases.  Because we don't need an invasive procedure, such as surgery, to obtain biofluids, liquid biopsies are non-invasive and painless.  This feature of liquid biopsy makes it useful, when tissue biopsy cannot be used.  An important example of such applications is cancer, where liquid biopsy can be used as a diagnostic and monitoring tool. How is Liquid Biopsy performed? Liquid biopsy analyses can be done on blood as well as other bodily fluids such as urine, saliva or sputum. But, blood samples are the most commonly used samples for testing. A small amount of blood is drawn using a needle and syringe. Cells are separated from the blood and circulating DNA or RNA is extracted from the cell-free blood, or blood components such as plasma or serum. Levels of nucleic acids are commonly measured using techniques such as PCR. Changes in the sequence of nucle...

 Earlier we saw how cell-free DNA  is  released into the body fluids . That raises a lot of questions... Does the amount of DNA vary from person-to-person? Can the DNA levels be different in people with diseases than in normal people? Yes, they can be...  For example, in cancer, researchers have measured cfDNA levels using many techniques. Some of them are radioimmunoassay, DNA dipstick, and real-time PCR. Different studies have reported different levels of cfDNA. But in general, cancer patients had higher cfDNA concentration than healthy people. Some studies compared cell-free levels in different cancer types. Of these, lung cancer patients had the highest levels of cell-free DNA. And prostate cancer patients had the lowest levels. So how can this information help in treating disease? To answer this, researchers compared DNA levels with patients' clinical information. They found that patients with bigger tumors had higher cell-free DNA levels. Patients with higher d...

 Welcome back reader! Today, we will look at how DNA reaches the bloodstream. There are two ways by which cells release DNA. One is when living cells release DNA under certain conditions such as stress or as defense. This is called as active release of DNA. Second, when cells die, they release their contents into the surroundings. This is called passive release of DNA.  Now, how can a cell actively release DNA into blood? There are many processes by which living cells can release DNA.  First is phagocytosis. Phagocytosis is a process by which white blood cells eat dead or infected cells and bacteria to protect the body from infection. Some of the types of white blood cells that usually do phagocytosis are monocytes, macrophages and neutrophils. Second is NETosis vital. Now imagine a man is fishing. What would he do if he wants to catch a large amount of fish at once? Throw a net, right? In the same way, neutrophils throw NETs to catch any bacteria or similar microbes that...

Last time we saw that DNA is released into blood by cells. But in what form is it released?  We know that DNA remains stable inside the cell. But what happens to it when it comes out of the cell? Does it remain stable? Well, cell-free DNA is known to exist in many forms.  Free DNA fragments One is that of a free or unbound DNA fragment, that is, the DNA fragment by itself without being bound to any surface. But without being bound to anything, can DNA be stable in blood? A good question, as our blood is known to contain proteins that can destroy DNA, called as DNases . But some studies reported that the activity of DNases was low in some diseases. For example, Svetlana Tamkovich and their group,  in 2006, compared DNase activity with cell-free DNA concentration in cancer patients. They found that DNase activity was low in cancer patients, but high in normal people. This means that more amount of cell-free DNA can survive in the blood of cancer patients than in the bl...