Story Summary: Instead of the normal pairs of 23 chromosomes, individuals with Down syndrome inherit an extra copy of one chromosome, in this case chromosome 21. Chromosomes are made of DNA and carry the genes that serve as the assembly and operations manual for life. Down syndrome is associated with a variety of medical and developmental problems, including a 10- to-20-fold increased risk of ALL. The new gene alteration was identified by St. Jude scientists following up on an earlier observation. They had previously found a recurring deletion in a region of DNA duplicated on the X and Y chromosomes. The PAR1 deletion was found only in patients with a subtype of ALL known as B-progenitor ALL. It was most common in children with both B-progenitor ALL and Down syndrome. In this study, investigators screened almost 400 children with ALL, including 75 patients with Down syndrome. The deletion was present in 7 percent of patients with B-progenitor ALL, but in more than half of the patients with both B progenitor and Down syndrome. Patients with Down syndrome are particularly vulnerable to complications from standard chemotherapy, and could therefore benefit from novel therapies, said Karen Rabin, M. D. , of Texas Childrens Cancer Center and a study co-author. She is a Baylor College of Medicine assistant professor of pediatric hematology/oncology. Both the cytokine, thymic stromal lymphopoietin (TSLP), and CRLF2 are known to play important roles in the development of immune cells known as T lymphocytes as well as in inflammation and allergic disease. CRFL2 is the second gene implicated in development of B-progenitor ALL in patients with Down syndrome. JAK2 belongs to a family of genes that produce enzymes called kinases. Almost all JAK mutations were observed in patients with CRLF2 alterations. It has been a mystery as to why the JAK mutations in Down syndrome ALL are different from those seen in other cancers, Mullighan said. Neither genetic alteration on its own produced the same effect. Researchers also reported their impact could be weakened by the addition of drugs that target JAK mutations. A next step is to determine if these mutations also interact in mouse models of ALL. com) — University of New Mexico Cancer Center researchers have identified a genetic mutation underlying one of the most common childhood cancers, acute lymphoblastic leukemia (ALL). Stanford University School of Medicine researchers have identified one pathway in this important process in mice . . ….Read the Full Story

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