A study, published in the journal PLoS Genetics, reveals that cancer cells might streamline their genomes for an easy proliferation. The researchers from the Stowers Institute for Medical Research conducted the study. They provide evidence suggesting that cancer cells rationalize their genomes in order to propagate more easily.
The study was conducted in both humans and mouse cells. It shows that genomes of the cancer cells lose copies of ribosomal DNA. These are repetitive sequences, which upon downsizing, enables the cancer cells to replicate faster. Moreover, they render them less able to withstand DNA damage. The study suggests that ribosomal DNA copy number can help to predict which cancers are sensitive to the DNA-damaging chemotherapeutics.
The findings of the study appeared in the respective journal on June 22, 2017. According to the researchers, the chemotherapeutics drugs are often DNA-damaging. However, it’s not clear yet that why would these drugs selectively kill cancer cells. The results of the study suggest that off-loading copies of ribosomal DNA render the cancer genome unstable. They make the cancer cells, particularly, susceptible to chemotherapy employing DNA-damaging drugs.
What does ribosomal DNA do?
Ribosomal DNA plays a critical yet identical role in both the healthy cells and cancer cells. It encodes the structural components of ribosomes. Ribosomes are responsible for producing the proteins, carrying out many cellular functions. Few studies, including the ribosomal analysis, show that the copies of ribosomal DNA expand and contract all the time.
It is a hypothesis that highly proliferating cancer cells need more than the usual amount of ribosomes for the expansion of copy number. However, the researchers have found exactly the opposite.
What did the researchers find?
The team utilized data from eight different human cancer genome projects. Using computational methods, the researchers counted the number of copies of ribosomal DNA in normal and cancer cells of 162 patients from the eight projects. No change in the copy number appeared in five of the projects. But in the remaining three projects, the cancer cells lost their ribosomal DNA copies, relative to the normal cells.
Droplet digital PCR was used to count the ribosomal DNA copies in normal and cancer cells from the mice. The cells were highly proliferative, made more ribosomal RNA, and synthesized more protein. However, all the cells had fewer copies of ribosomal DNA.
The scientists thought that the pressure to proliferate would lead to an increase in the copy number, so there would be more DNA transcribed into RNA. However, less DNA to copy was speculated to promote proliferation. Moreover, the cancer cells were more sensitive to DNA damage than normal cells.
The scientists believe that if the same idea persists in humans. It can be clinically very helpful. The study was funded by the Stowers Institute of Medical Research. Plus, the researchers encourage further studies regarding this subject. This might help in diagnostic and therapeutic measures regarding cancer treatments.