CRISPR model unlocks potential for early leukemia interventions

February 10, 2021
CRISPR is not quite ready for one of its biggest hoped-for purposes. (AP Photo/CDC)

CRISPR is not quite ready for one of its biggest hoped-for purposes. (AP Photo/CDC)

A Mount Sinai research team built the first cellular model to depict progression of acute myeloid leukemia, or AML, from early to late stages through CRISPR gene editing, paving the way to improve targeted therapies and early interventions.

A study published Wednesday in Cell Stem Cell describes how the team led by Icahn School of Medicine used gene-editing technologies to alter genes that make malignant cells to identify potential therapeutic targets for early AML stages. With an estimate of nearly 20,000 newly diagnosed cases in the U.S. last year, AML is one of the most common leukemias.

Researchers leveraged CRISPR/Cas9 technology to alter DNA sequences in induced pluripotent stem cells, or iPSC, by introducing specific leukemia-causing gene mutations. This led to the creation of a model with an increasing number of mutated genes with progressive malignant features.

Lead study author Eirini Papapetrou notes that CRISPR/Cas9 and iPSC technologies gave researchers the “unique opportunity to characterize changes underlying the transitions between stages of AML, and to harness patterns of these changes to pinpoint target genes for early intervention.” They modeled “the order by which mutations arise in normal cells, and drove [those mutations] through consecutive stages of increased malignant features through to leukemia,” explained Papapetrou, who is also an associate professor of oncological sciences at Icahn Mount Sinai.

CRISPR gene editing, among other methods, has been used increasingly often since 2012 to mimic mutations of blood cancers, introduce them into cells and then observe what they do. 

Gene-editing technologies were “very cumbersome and difficult to implement” prior to CRISPR becoming available, Papapetrou said in an interview with The Academic Times

The researchers at Sinai had done similar projects where cells were captured at different stages of the spectrum of transformation, from normal to leukemia. But this process develops in humans throughout “many, many years, even decades, so it’s hard to, from one single sample, one time, one snapshot, to get every possible stage, and therefore we couldn't have the full spectrum,” Papapetrou said.

The team built on existing research from sequencing leukemia projects about the order, the combination and different mutations as well as how they need to occur in becoming leukemia.

“With CRISPR we have the power to recreate and make it so that we have everything exactly in the order by which it happens and have it in front of us,” Papapetrou added. It allowed the team to model isolated mutations in a precise and more controlled way in the lab for the first time.

Yet how exactly the modeled strategy can be applied in clinical settings remains unclear. 

“There is still a lot more to learn and understand about this before we can apply it to the clinic,” said Papapetrou. “But what I think is quite remarkable is that there's now a lot of converging evidence that inflammation is a factor here on oncogenesis, in our case in particular leukemogenesis, that might be an opportunity for something to intervene and modulate earlier.” 

An open question is what would be better to target, from early or later clones to mutations acquired earlier or those acquired later. Most of the targeted therapies that have been developed more recently focus on later mutations like IDH2. 

Such therapies “haven’t given transformative response, and that could be for many reasons, but one of them could be that they target too late and you still have the cells earlier on that can still drive the disease, so you're not doing anything that's very transformative to the disease,” Papapetrou said. “There is a good reason to think that targeting early events will have more lasting responses.” 

The study suggests that it is possible to find such early events, and that it is possible to target those.

The study identifies inflammatory and innate immunity pathways as early targets for intervention that can be applied to AML, as well as blood cancer myelodysplastic syndrome and the pre-leukemic condition clonal hematopoiesis.

“Often when you give a therapy to a patient who has leukemia, it can be argued that it's already too late and no matter what you do, you're going to always have some cases of resistance or relapse,” noted Papapetrou. “Now, there are opportunities to detect these pre-leukemia conditions and identify individuals that are at higher risk of developing leukemia and either target earlier or completely prevent that from happening.” 

It would be “highly desirable to have a therapy that is going to eliminate not only the cells that are driving the later stages of the disease, but also the earlier ones and completely eradicate it,” Papapetrou added.

Future research at Sinai aims to better understand the role of inflammatory signaling as the biggest indicator and how viable it would be to move the strategy of using the model to follow leukemia evolution to the clinic. Papapetrou says the team is particularly interested in understanding "how different mutations might actually contribute to this different inflammatory state or regulation that leukemia and pre-leukemia cells have.”

The study, “Sequential CRISPR gene editing in human iPSCs charts the clonal evolution of myeloid leukemia and identifies early disease targets,” was published in Cell Stem Cell on Feb. 10. The authors of the study are Tiansu Wang, Allison R. Pine, Andriana G. Kotini, Han Yuan, Lee Zamparo, Daniel T. Starczynowski, Christina Leslie and Eirini P. Papapetrou, Icahn School of Medicine at Mount Sinai. 

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