Stories about: Kimberly Stegmaier

Overriding resistance to epigenetic inhibitors in neuroblastoma: Targeting PI3K

(IMAGE COURTESY NATIONAL CANCER INSTITUTE)

Children’s cancers pose unique challenges. They’re not caused by the same kinds of genetic mutations that cause adult cancers, and only a minority of their mutations can be targeted with drugs. In a recent study, Kimberly Stegmaier, MD, at Dana-Farber/Boston Children’s Cancer and Blood Disorders Center and her colleagues systematically deleted every gene in the genome in a number of childhood cancers. This led them to previously unknown — and targetable — genes that help drive tumor growth.

But Stegmaier is also interested in epigenetic regulators — proteins that help control the regulation of genes and contribute to many pediatric cancers. They’re a hot subject of research: Child cancers tend to arise in developing tissues, and epigenetic regulators are active during early development. Clinical trials are starting to test drugs that inhibit epigenetic cancer-promoting factors.

There’s a problem, though: Cancers often become resistant to targeted inhibitors, including epigenetic inhibitors. So, again using genome-wide approaches, Stegmaier set out to find ways to overcome this resistance.

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CRISPR-Cas9 screen opens new targets for Ewing sarcoma, other childhood cancers

Ewing sarcoma research by Kimberly Stegmaier, MD
The TP53 pathway normally helps pull the plug on cancerous cells. While the pathway is intact in most pediatric cancers, research finds that drugs targeting the pathway can curb tumor cell proliferation in Ewing sarcoma. Photo: Kimberly Stegmaier, MD (SAM OGDEN / DANA-FARBER CANCER INSTITUTE)

While the genetic mutations driving adult cancers can sometimes be targeted with drugs, most pediatric cancers lack good targets. That’s because their driving genetic alterations often create fusion proteins that aren’t easy for drugs to attack.

“This is one reason why it is notoriously hard to make targeted drugs against childhood cancers — their cancer-promoting proteins often lack good pockets for drugs to bind to,” says Kimberly Stegmaier, MD.

However, that’s beginning to change.

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Cancer researchers hit a bullseye with a new drug target for Ewing sarcoma

Cell staining shows the lethal efficacy of CDK+PARP inhibitors against Ewing sarcoma
Fluorescent staining shows how PARP and CDK12 inhibitors combine to deal a lethal blow to Ewing sarcoma. In the top row, green represents locations of DNA damage incurred by Ewing sarcoma cells. In the bottom row, red represents DNA repair activity. Together, PARP and CDK12 inhibitors lead to Ewing sarcoma cell death.

Screening a class of recently-developed drug compounds — so-called “CDK inhibitors” capable of blocking CDK7/12/13 proteins — against hundreds of different human cancer cell lines, researchers at Dana-Farber/Boston Children’s Cancer and Blood Disorders Center have found that CDK12 inhibitors pack a particularly lethal punch to Ewing sarcoma, a rare cancer typically affecting children and young adults.

“No one has previously considered CDK12 inhibition as a way to combat Ewing sarcoma,” says Kimberly Stegmaier, MD, senior author of the new Cancer Cell paper that describes the findings.

In 2014, Nathaneal Gray, PhD, co-author on the new paper, and his team were the first to develop CDK inhibitors.

Some individuals were entirely cured of the disease

“Now, in mice, we’ve shown that Ewing sarcoma cells die if CDK12 is knocked out genetically or chemically inhibited,” Stegmaier says. What’s more, her team has discovered that CDK12 inhibition can be combined with another drug, called a PARP inhibitor, to double down on Ewing sarcoma cells.

The revelation that CDK12 inhibition can kill Ewing sarcoma cells brings a surge of hope to the field of pediatric oncology, which has long been challenged to find new drugs against childhood cancers.

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Taking a sideswipe at high-risk neuroblastoma

Microscopy image of human neuroblastoma cells.
Human neuroblastoma cells.

Cancer and other diseases are now understood to spring from a complex interplay of biological factors rather than any one isolated origin. New research reveals that an equally-nuanced approach to treating high-risk neuroblastoma may be the most effective way to curb tumor growth.

One challenge in treating pediatric cancers like neuroblastoma is that they are not initiated from the same kinds of genetic mutations as adult cancers, which usually arise from mutations related to an accumulation of DNA replication errors or environmental factors. In contrast, childhood cancers more often stem from genetic duplications, deletions or translocations, the latter of which occurs when a gene sequence switches its location from one chromosome to another.

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Progress in the treatment of childhood leukemia

Although treatments for childhood cancer patients are improving, cancer remains the leading cause of death by disease in children. Doctors and researchers are also focused on decreasing the toxicity of these treatments, which can have side effects years after a child finishes treatment.

“The war against childhood cancer is hardly over,” says Kimberly Stegmaier, MD, a pediatric oncologist at Dana-Farber/Boston Children’s Cancer and Blood Disorders Center. “We need to do better.”

Stegmaier, who focuses her research on identifying new drug targets and new drugs for childhood leukemiaEwing sarcoma, and neuroblastoma, recently discussed advances in childhood cancer treatment in a Science, Innovation, and Discovery Talk (SID Talk) at Dana-Farber. During the TED Talk-style presentation, Stegmaier explained some of her research in the treatment of sub-microscopic acute lymphoblastic leukemia (ALL) as well as genetic targets in childhood cancers.

“What you can do in an environment where you have chemists, biologists, and clinicians adjacent and working collaboratively is very powerful,” says Stegmaier. “That’s why I’m here today—we need to cure 100 percent of kids, and we can’t do this alone.”

This story originally ran on Dana-Farber Cancer Institute’s Insight blog.

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