Evidence for clustered tumour suppressor gene loci on mouse chromosomes 2 and 4 in radiation-induced Acute Myeloid Leukaemia

Abstract

Purpose: To investigate the influence of genetic and epigenetic factors on allelic loss on chromosomes 2 and 4 in mouse radiation-induced acute myeloid leukaemia (r-AML).

Methods: r-AML that arose in (CBA/H×C57BL/6)F1×CBA/H and F1×C57BL/6 mice were screened for transcription factor PU1 (also known as SPI-1) gene mutations and methylation of the paired box gene 5 (Pax5) gene promoter. We have increased the statistical significance of a genetic linkage analysis of affected F1×CBA/H mice to test for linkage to loci implicated directly or indirectly with r-AML-susceptibility.

Results: There was a statistically significant difference ( p < 10⁻⁴) in the frequency of PU1 gene mutations in F1×CBA/H and F1×C57BL/6 r-AML, implicating a second linked but genotype-dependent myeloid leukaemia suppressor gene on chromosome 2. A suggestive CBA/H r-AML-resistance locus maps within 10 cM of the minimally deleted region on chromosome 4. The Pax5 gene promoter is subject to ongoing subclonal promoter methylation in the r-AML, evidence that Pax5 gene silencing confers a selective advantage during clonal expansion in vivo.

Conclusions: Allelic loss in mouse r-AML and subsequent tumour suppressor gene mutation (PU1) or silencing (Pax5) is strongly influenced by genetic background and/or epigenetic factors, and driven by in vivo clonal selection.

Keywords:

• PU1
• Pax5
• radiation-induced AML