"Chromosomal Chaos:" Complex Array of Mutations Found in Rare, Aggressive Leukemia

"Chromosomal Chaos:" Complex Array of Mutations Found in Rare, Aggressive Leukemia

Sezary syndrome is a rare condition: Its incidence is estimated to be about 0.3-2 cases per 100,000 in the United States each year, and those patients have a five-year survival rate of less than 30 percent.

The team integrated three, complementary gene sequencing approaches to look for mutations in tumor cells from SS patients: whole-genome sequencing in six subjects, sequencing of all protein-coding regions (exomes) in 66 subjects, and comparing variation in the number of copies of all genes across the genome in 80 subjects.

We did not expect the degree of genetic complexity that we found in our study,” author said. They identified previously unknown recurrent loss-of-function mutations that target genes regulating epigenetic pathways – ones that act on how tightly or loosely chromosomes are wound and thus accessible for genes to be expressed. One of these targets is called ARID1A, and they found that loss-of-function mutations and/or deletions in ARID1A occurred in over 40 percent of the SS genome studied.

They also identified “gain-of-function” mutations in PLCG1, and JAK1, JAK3, STAT3 and STAT5B.  In preliminary drug-mutation matching studies, they found that JAK1-mutated SS cells were sensitive to JAK inhibitors, drugs that are currently approved for treatment of other hematologic cancers such as polycythemia vera and myelofibrosis.

“With knowledge like this, we can design clinical trials using JAK inhibitors for SS patients based on their JAK mutations,” said the author. “But this is just the start. These results highlight the genetic vulnerabilities that we can use in designing precision medicine therapies.”