Molecular Cytogenetic Studies of Leukaemogenesis

Project Description

Funding Children’s Medical & Research Foundation.
Principal Investigator Dr Raymond Stallings.
Researchers Dr. Linda McArdle, Ms. Paula Carty.
Duration April 2002 - March 2004.
Collaborators Drs. Anne O’Meara, Fin Breatnach, Aengus O’Marcaigh.

Introduction

Cytogenetic and molecular cytogenetic analysis of leukaemia cells forms an integral part of any modern approach to the treatment and management of patients with haematological malignancy.

Haematological malignancies are characterized by recurrent, nonrandom chromosome abnormalities and more than 200 primary or secondary chromosome abnormalities have been associated with various types of leukaemias.

Identification of chromosomal abnormalities with known diagnostic or prognostic significance is essential to determine the most optimum treatment modality.

Monitoring patients by cytogenetic analysis following treatment for signs of residual disease, or disease progression allows early intervention and will improve treatment and disease management.

Work in progress

The following work is currently in progress:

High resolution mapping of deletion 16q22 breakpoints found in acute myelogenous leukaemia and myelodysplastic syndrome

Rearrangements of chromosome 16q22 are a common event in myeloid malignancies.

The most common abnormality is the inv(16)(p13q22) that is characteristic of M4EO AML and leads to fusion of segments of the myosin heavy chain gene (MYH11) and the transcription factor CBFB.

The breakpoints were originally identified using cosmid clones from our chromosome 16 ordered clone map.

Another common AML abnormality is deletion of band 16q22. Deletion of 16q22 is not specific to an AML FAB subtype and is quite often preceeded by a myelodysplastic phase before the leukaemia development.

The gene(s) targeted by the deletion may not be the CBFB gene since the phenotypic effect of the deletion is somewhat different from the inversion.

The goal of our studies is to refine the mapping of the region on chromosome 16q that is commonly deleted in MDS/AML and to identify the gene(s) involved with AML leukemogenesis.

We are using sets of BAC clones generated at the Los Alamos National Laboratory to refine the mapping of the deleted region.

A final aspect of our studies is to determine if low abundance, chromosome 16-specific repetitive sequences, originally identified in our physical mapping studies (38,43), are in proximity to the breakpoints and provide a mechanism for generation of the deletions by recombination.

Analysis of leukaemia with complex chromosome abnormalities using MFISH

Another goal of our leukaemia studies is to characterize leukaemias with complex chromosome abnormalities using MFISH.

We have a large number of archived cases where chromosome abnormalities were too complex to be fully characterized by banding analysis.

These cases are being analyzed using molecular cytogenetic methods such as MFISH and CGH in order to determine what abnormalities have occurred, and whether novel, recurrent abnormalities can be identified.