Many cancer treatments damage cell DNA. After too much irreparable damage, cells can initiate their own death. High school biology teaches us that the protein p53 takes charge of this process. p53 ensures repair of damaged DNA, but initiates cell suicide when the damage becomes too severe. This prevents uncontrolled cell division and cancer formation.
That sounds like a foolproof system, but reality is more complex. "In more than half of tumors, p53 no longer functions," says Thijn Brummelkamp. "The key player p53 plays no role there. So why do cancer cells without p53 still die when you damage their DNA with chemotherapy or radiation? To my surprise, that turned out to be an unanswered question."
His research group then discovered, together with the group of colleague Reuven Agami (both research groups are part of Oncode Institute), a previously unknown way in which cells die after DNA damage. In the lab, they administered chemotherapy to cells in which they carefully modified the DNA. Thijn: "We were looking for a genetic change that would allow cells to survive chemotherapy. Our group has a lot of experience in selectively disabling genes, which we could perfectly apply here." (see text box)
By switching off genes, the research group found a new pathway to cell death headed by the gene Schlafen11 (SLFN11). Principle investigator Nicolaas Boon: "In the event of DNA damage, SLFN11 shuts down the protein factories of cells: the ribosomes. This causes immense stress in these cells, which leads to their death. The new route we discovered completely bypasses p53."
The SLFN11 gene is not unfamiliar in cancer research. It is often inactive in tumors of patients who do not respond to chemotherapy, says Thijn. "We can now explain this link. When cells lack SLFN11 they will not die in this manner in response to DNA damage. The cells will survive and the cancer persist."
