The second leg of the journey among leading labs takes us to the European Institute of Oncology in Milan. CRISPR’s potential is particularly exciting for oncology, as tumors are caused by multiple mutations and the new technique of genome editing is multiplexable, meaning it may target several genes at the same time. IEO scientific co-director Pier Giuseppe Pelicci has shared his enthusiasm with us.
“In our lab we are using CRISPR in 3 broad research areas. In the first area we follow the classic way, by disrupting the genes we want to study in order to understand their functions. CRISPR can do it much better than the previous techniques. It’s fast, very cheap and easy to handle. Before CRISPR we could carry out an experiment every 6 months, after CRISPR we can do one every week. It’s like altering the flow of time.”
What kind of genes do you target, can you give us any example?
“Our latest experiment concerns the phenomenon of cellular reprogramming, i.e. when a mature cell is reprogrammed back into an undifferentiated state. This can be done in the lab by activating 4 genes and getting induced pluripotent stem cells as a result. We had several questions in mind. Does reprogramming happen spontaneously in the human body? During a woman’s lifetime, for example, may an adult mammary cell revert to stem cell? Does it occur in tumors? May cancer cells become stem cells? The answer is yes, and some 20 genes are involved. We cripple them one by one and then we watch the effects of this targeted disruption. Without CRISPR it would be an ordeal, now it’s a pleasure. We can simultaneously target 4 or 5 genes in the same cell, a result that would have required 5 to 6 years before and now is achieved in 15 days.”
What about the second research area, do you use CRISPR in a different way?
“Instead than cutting the DNA as usual, we use a Cas9 variant that finds the desired gene and turns it on. In place of the molecular scissors of the classic kit we have a kind of molecular switch, that we are using to investigate antibodies directed against cancer cells. We have a platform to generate such antibodies, but we must understand which antigen is targeted by each antibody. Again, it would have required a couple of years with the old systems, but by teaming up with the Sanger Institute and harnessing the power of CRISPR we created a library, meaning a collection of human cells, where each cell is mutated in one of its 22,000 genes. We cover the whole human genome in this way. By checking which cells are recognized by a certain antibody we identify its antigen. This is a drug discovery strategy, useful to find therapeutic targets.”
Eager to know about the third area. What are you doing?
“It’s another Cas9 library, made in collaboration with the biotech company Cellecta. We knockout the genes and inject the mutated cells into the mouse model to figure out which of them are involved in tumor promotion.”
CRISPR is said to be so simple that anybody can use it. Is it true?
“Well, in my experience if you put the kit in the hands of a 35 years old postdoc he struggles a little bit, because he is accustomed to different procedures and has to destructure himself. It’s easier for a graduate who has never tried the older techniques.
Is it a real revolution or are we getting overexcited?
“We rightly became enthusiastic about the human genome sequencing in the past, and it was a great endeavor indeed. But CRISPR is even more compelling. Reading the DNA text is not so useful, as long as the genes function is unknown. CRISPR opens wide the door to functional genomics. It was called the biggest game changer to hit biology since PCR, but in my opinion is even more revolutionary than the polymerase chain reaction. I don’t usually buy the hype, but this is something really amazing.”
(The picture is from the magazine Panorama)