Frequent loss of heterozygosity on chromosomes 4, 12 and 19 in radiation-induced lymphomas in mice

We found frequent loss of heterozygosity (LOH) on chromosomes 4, 12 and 19 in radiation-induced lymphomas from (BALB/cHeA × STS/A) F1 hybrid mice by allelotype analysis at polymorphic microsatellite loci. The incidences of LOH were 27% (20 of 74 lymphomas), 57% (42 of 74 lymphomas) and 50% (37 of 74 lymphomas) on chromosomes 4 (at D4Mit31), 12 (at D12Mit17) and 19 (at D19Mit11), respectively. These frequent LOH regions are homologous to human chromosomes 9p and 1p, chromosome 12q32.1 and chromosome 10q, respectively. Strain-specific preferential allele loss was observed only on chromosome 4. However, no bias in the frequency of loss between alleles of maternal and paternal origin was observed, indicating that genomic imprinting may not be predominantly involved in these lymphomas. The results suggest that these three regions might harbor tumor suppressor genes responsible for this lymphomagenesis.