Allelic losses on chromosome 4 suggest the existence of a candidate tumor suppressor gene region of about 0.6 cM in gamma-radiation-induced mouse primary thymic lymphomas.

Mouse chromosome 4 was investigated to assess the involvement of tumor suppressor genes in primary thymic lymphomas induced by gamma-irradiation. PCR analysis using microsatellite DNA polymorphic markers was performed in F1 animals generated from a cross between the strains C57BL/6J and RF/J. Microsatellite markers were selected with focus on chromosome 4 around the region containing the interferon alpha gene cluster (D4Mit17, D4Wsm1, D4Mit9, and D4Mit205 and a more distal region (D4Mit12, D4Mit54, and D4Mit13). Allelic losses were detected in 21/47 (44.7%) gamma-radiation-induced thymic lymphomas. Analysis of markers located on six other chromosomes as well as on the proximal region of chromosome 4 illustrates the specificity of the occurrences of LOH appearing on the former markers. This analysis clearly suggests the existence of a candidate tumor suppressor gene region on mouse chromosome 4 of about 0.6 cM between the markers D4Wsm1 and D4Mit9 (TLSR1, Thymic Lymphoma Suppressor Region 1). In addition, another more distal region centered at the marker D4Mit54 could be also exist (TLSR2). In most tumors, allelic losses on these chromosome regions involved the paternal RF/J allele (19 of 20).