It is well recognized that genetic aberrations, such as chromosomal translocations, are complemented by secondary aberrations (possible epigenetic) that give rise to leukemic clones. However, complementary epigenetic event(s) and their roles in development of common subtypes of childhood leukemias are not well characterized. Our goals are to understand the scope of genome-wide epigenetic alterations in childhood leukemia, and then develop epigenetic screening markers to test archived neonatal blood spots (Guthrie cards) for early detection of leukemia. We have successfully performed preliminary experiments using GoldenGate Methylation Cancer Panel I microarrays (Illumina, Inc), using leukemic bone marrows, and corresponding archived Guthrie cards of childhood leukemias patients, to test the contribution of a large panel of cancer- related genes in the development of leukemia. We have also performed experiments with leukemia cell lines to test the gene expression response to a demethylating agent. This technique involved pharmacologic inhibition of epigenetic modifications, coupled with gene expression microarrays (Affymetrix Exon 1.0), and has yielded a number of candidate genes for which gene promoter methylation may play a functional role in leukemia. Our current focus is to focus on a panel of preliminary candidate genes using validation assays in primary leukemia samples, and then focusing further in Guthrie cards for our chosen targets. In the current application we will use methylation-specific PCR and bisulfite sequencing to reduce the size, and to focus our current large panel of 90 gene targets. We will choose the 30 which are methylated in the highest fraction of TEL-AML1 leukemia and which are not methylated in normal CD34 cells and normal Guthrie card DNA. We will then test this panel of epigenetic markers in Guthrie cards from children who grew up to get TEL-AML1 leuekmia and compare to a group of 500 children who did not, to assess predictive value. We focus exclusively on the most common cytogenetic subltype, those with TEL-AML1 translocations who are 22% of all ALL.
This research aims ultimately at the characterization of early epigenetic mutations and imprinting abnormalities in the development of leukemia, and the use these markers for the early detection of pediatric leukemia.
PROJECT NARRATIVE: With this project we are exploring the existence of early markers of leukemia at birth. This will impact public health by increasing our knowledge in the mechanisms of the etiology of childhood leukemia and providing markers for the early detection of, or predisposition to, leukemia at birth.
| Diakos, Christofer; Zhong, Sheng; Xiao, Yuanyuan et al. (2010) TEL-AML1 regulation of survivin and apoptosis via miRNA-494 and miRNA-320a. Blood 116:4885-93 |
