Turns Out Mitochondria Have an Unknown Function
Now, a new study discovered a new feature of mitochondria: it can act as a molecular alarm when cells are exposed to stress or chemicals which can harm DNA. Chemotherapy can be an example of this.
Mitochondria contain their genome, the mitochondrial DNA (mtDNA), in the mitochondrial matrix. In this study, scientists aim to determine the molecular pathways which are activated by the release of damaged mtDNA into the cell's interior.
The main interest of scientists is a subset of genes, also known as interferon-stimulated genes, or ISGs. These are normally activated by the presence of viruses; however, the genes were a particular subset of ISGs turned on by viruses, this subset of ISGs can be found to be activated in cancer cells that have developed resistance to chemotherapy by with DNA-damaging agents like doxorubicin.
Doxorubicin targets nuclear DNA to destroy cancer cells. However, this new study points out that doxorubicin also damages mtDNA and causes a release of it; and it activates ISGs. According to the group of scientists, this subset of ISGs protects nuclear DNA from damage which causes increased resistance to the chemotherapy drug.
Gerald Shadel, a professor in Salk's Molecular and Cell Biology Laboratory and the Audrey Geisel Chair in Biomedical Science says "Perhaps the fact that mitochondrial DNA is present in so many copies in each cell, and has fewer of its own DNA repair pathways, makes it a very effective sensor of DNA stress."
He also points out, "It says to me that if you can prevent damage to mitochondrial DNA or its release during cancer treatment, you might prevent this form of chemotherapy resistance."