Molecular analysis of chromosome 22 breakpoints in adult Philadelphia-positive acute lymphoblastic leukaemia

TLDR

The Philadelphia translocation t(9;22)(q34;q11) is common in chronic myelogenous leukaemia and occurs in about 20% of adult acute lymphoblastic leukaemia, with the chromosome 22 breakpoint localized to a 5.8‑kb breakpoint cluster region. The study aimed to investigate the chromosome 22 breakpoint configuration in adult Philadelphia‑positive acute lymphoblastic leukaemia. Five adult Ph‑positive ALL patients were examined for breakpoint cluster region rearrangements. Breakpoint cluster region rearrangements were found in two patients, while one patient had a break upstream of the first exon and two patients had no bcr involvement, indicating that the t(9;22) translocation can produce distinct genomic configurations in ALL compared to CML.

Abstract

The Philadelphia (Ph) translocation, t(9:22)(q 34:q11), is found in the majority of patients with chronic myelogenous leukaemia (CML) as well as in approximately 20% of adult acute lymphoblastic leukaemia (ALL) patients. The chromosome 22 breakpoint in CML has been localized within a restricted 5.8 kb segment of DNA known as the breakpoint cluster region (bcr). To investigate the chromosome 22 breakpoint in ALL, we analysed five adult Ph-positive ALL patients for bcr rearrangement. Rearrangement was detected within bcr in two patients. However, in one patient the break occurred 5' to the first exon of bcr and in two patients the bcr region was not involved. We conclude that the identical cytogenetic marker, t(9:22), may yield a different genomic configuration in ALL and CML.