Cancer is now one of the malignant diseases that threaten human health, and it is also showing a trend of getting younger and younger. With the development of medical technology, people can already see some changes in tumor markers that suggest that there may be tumors in the human body through the simplest blood test methods, such as carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP) and CA199.
So have you ever heard that cell free DNA (cfDNA) can also be detected in the blood? What is cfDNA? What does it have to do with tumors?
What is DNA?
DNA, or DNA, is a molecule within biological cells that is the carrier of all genetic information and is generally present inside the cell.
The DNA sequence of different cells is not the same, and by measuring the sequence we can tell which kind of cell this DNA molecule originates from. Just like the police catch a prisoner, the corresponding prisoner can be found through DNA comparison. Compared with normal cells, tumor cells produce a large number of mutations in the sequence of their genomic DNA, which causes them to grow abnormally.
What is cellular free DNA (cfDNA)?
cfDNA refers to fragments of DNA that are degraded by dead cells released into the blood plasma. cfDNA is present in a variety of body fluids of the human body, including blood, urine, cerebrospinal fluid, ascites, etc., usually in size of 160 bases, and the half-life is 16 minutes to 2.5 hours. Normally, the body's cells don't have so many dead cells, so the amount in the blood is very low.
The free DNA associated with tumors in the blood is called circulating tumor DNA (ctDNA), which mainly comes from the apoptosis, necrosis and self-secretion of tumor cells, which will be shorter, generally 134 to 144 bases in size. ctDNA has a short half-life of just 0.5-1 hour.
Due to the rapid metabolism and proliferation of tumor cells, a large number of cells apoptosis and necrosis after the lack of oxygen, so a large amount of ctDNA will be released into the blood.
In addition, since tumor cells contain many genetic mutations, we can also determine whether there is a ctDNA by measuring whether there is a mutation in the cfDNA circulating in the blood.
Measure changes in the content of ctDNA and mutations in its sequence
What's the point?
Assists in the early diagnosis of tumors
Determining the presence of ctDNA can help detect early tumors by measuring changes in cfDNA levels in body fluids and whether there are mutations in tumor-associated genes, buying time for subsequent treatment.
Judge the effect of treatment
By measuring the content change of ctDNA, the effect of the patient's current treatment is judged, and the effect of tumor clearance is observed to avoid over-treatment.
Assist in the selection of treatment options
Sequencing the ctDNA of tumor patients can help with targeted drug selection and help doctors do better personalized treatments.
Monitor the disease
During treatment, due to the short half-life of ctDNA, it can reflect the state of the tumor in real time, and it is also convenient to obtain cfDNA through the blood, which is a minimally invasive method. Therefore, ctDNA testing is very suitable for monitoring changes in tumor treatment in order to adjust the protocol in time.
Compared with other blood cancer-related protein detection indicators, ctDNA has the advantage of having a shorter half-life, which can better reflect the current condition of the tumor. Studies have shown that ctDNA is more sensitive than protein markers when detecting breast and bowel cancers, and can also track the disappearance, spread and recurrence of tumors.
Write at the end
Although ctDNA has great potential in tumor treatment, if it is widely used in clinical practice, it still faces many problems, such as the selection of sequencing methods, the problem of sequencing time and cost, the relatively small amount of ctDNA released in early tumors will bring detection difficulties, etc., and there is still room for scientists to further optimize and use ctDNA to help cure more tumors as soon as possible!