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Newswise – For patients diagnosed with IDH-mutant glioma, an incurable brain tumor that often affects adults in their 30s and 40s, treatment typically works at first. However, the cancer almost always returns, and when it does, it frequently stops responding to treatment.
Now, Yale researchers and their collaborators at Massachusetts General Hospital, the Weizmann Institute of Science, and the University of Miami have mapped how these tumors shift from initial diagnosis to recurrence. In a new study published June 3 in Nature, the team identified two broad patterns: Some tumors remain relatively stable, while others acquire new genetic alterations and shift into more aggressive cellular states associated with reduced treatment sensitivity.
“The tumor becomes increasingly treatment resistant, and patients ultimately pass away from this disease” says Roel Verhaak, PhD, Harvey and Kate Cushing Professor of Neurosurgery at Yale School of Medicine. “What we didn’t previously understand was how these tumors were changing between the patient’s initial treatment and recurrence, and whether those patterns were consistent across patients.”
To investigate this question, the researchers analyzed molecular data from tumors collected from 35 patients with IDH-mutant glioma. Rather than relying only on bulk tumor sequencing, which provides an average view of many cells, the team integrated multiple layers of molecular information, including DNA sequencing, single-cell RNA sequencing, and single-cell chromatin accessibility profiling.
DNA sequencing allowed the team to track genetic alterations in the tumors over time, including mutations acquired after treatment. Single-cell RNA sequencing allowed them to measure gene activity in individual tumor cells, while chromatin accessibility profiling revealed which regions of the genome were active. Together, these tools helped the team link specific genetic events to the cell states and regulatory programs that emerge as tumors recur.
“What really distinguishes this study compared to prior work is that we integrated multiple layers of high-resolution molecular information to understand how these tumors respond to therapy,” says first author Kevin Johnson, PhD, a research scientist in Verhaak’s lab.
Two paths after treatment
The analysis revealed a clear divide in how IDH-mutant gliomas progress after treatment. In some patients, recurrent tumors remained relatively stable, with limited genetic and cellular changes. In others, the tumors acquired new genetic alterations and transitioned toward more aggressive cellular programs.
“The group with substantial genetic changes showed reduced sensitivity to treatment,” says Verhaak, a member of Yale Cancer Center. “These changes may help explain why some tumors become more difficult to treat after recurrence.”
One hallmark of this pattern was the emergence of a more stem cell-like and proliferative tumor cell state. Another involved the emergence of a tumor cell state associated with changes in the tumor microenvironment, including immune cells linked to immune suppression. This latter pattern was strikingly similar to what has been observed in glioblastoma, the most lethal brain cancer, the team says.
While the findings reveal how therapy can shape the changes that occur in recurrent tumors, the researchers emphasize that current treatments remain beneficial for patients. The goal, Verhaak says, “is to identify when and why tumors stop responding to therapy so that we can better inform their subsequent treatment.”
Ultimately, the researchers hope their findings will help guide new approaches that keep tumors on a treatment-sensitive path.
Fueling this scientific push are the meaningful personal connections they maintain with the patient community. “The patients really motivate us to keep going,” Johnson says. “Seeing the impact of the disease drives us to keep pushing our understanding forward so we can provide patients with better treatment options.”
