Credit: A.T. Tikhonenko
A novel sequencing technique has allowed researchers to identify direct targets of p53, providing new insight into this gene’s anticancer activity.
The research, published in eLife, revealed nearly 200 genes that were directly regulated by p53, and many of these had never been identified before.
The study’s authors said this work lays the foundation for investigations into which of these genes are necessary for p53’s cancer-killing effects and how cancer cells evade these genes.
The researchers noted that all cancers must deal with p53’s antitumor effects. Generally, there are 2 ways they do this: by mutating p53 directly or by producing the protein MDM2, which inhibits p53 function. With the current study, the team explored the second strategy.
“MDM2 inhibitors, which are through phase 1 human trials, effectively activate p53 but manage to kill only about 1 in 20 tumors,” said study author Joaquín Espinosa, PhD, of the University of Colorado in Boulder.
“The question is why. What else is happening in these cancer cells that allow them to evade p53?”
According to the researchers, the answer is in the downstream effects of p53. The gene sets in motion a cascade of events that lead to cancer cell destruction. But it has been unclear exactly which other genes are directly activated by p53.
To identify genetic targets of p53, Dr Espinosa and his colleagues used a technique called Global Run-On Sequencing (GRO-Seq). Unlike other methods, GRO-Seq measures new RNA being created, not overall RNA levels.
“Many teams around the world have been getting cancer cells, treating them with MDM2 inhibitors, and waiting hours and hours to see what genes turn on, and then, only imprecisely,” Dr Espinosa said. “GRO-Seq lets us do it in minutes, and the discoveries are massive.”
The technique generates a large quantity of data because it requires counting tens of thousands of RNA molecules before and after p53 activation. So this research required designing algorithms to sort through the data, as well as a computational biologist driving a supercomputer.
But the researchers were able to pinpoint new genes directly regulated by p53. And they believe this could aid the future development of cancer-fighting strategies.
