Loss of heterozygosity on chromosome 5 in vicinity of the telomere in gamma-radiation-induced thymic lymphomas in mice.

Analysis of the loss of heterozygosity at the D5Mit143 locus was done for thymic lymphlomas induced by gamma-irradiation of mice from two reciprocal backcrosses (BALB/c x CcS-13)F1 x BALB/c and (BALB/c x CcS-13)F1 x CcS-13. BALB/c mice are susceptible to gamma-ray induction of lymphomas. The CcS-13 strain is one of 20 CcS/Dcm (CcS) series of recombinant congenic strains, and the CcS-13 mice are resistant to gamma-radiation-induced lymphomas [1, 8]. Our preliminary tests show 50% (6/12) frequency of allelic loss at the D5Mit143 locus in thymic lymphomas induced by gamma-irradiation of the mice from (BALB/c x CcS-13)F1 x BALB/c backcross. Yet, in gamma-radiation-induced lymphomas from the backcross made in opposite direction, namely, (BALB/c x CcS-13)F1 x CcS-13, the analysis with the DSMit143 marker revealed low incidence of the loss of heterozygosity, 6.7% (15). The D5Mit143 locus resides in the distal part of chromosome 5, close to the telomere. Allelic loss of heterozygosity at the D5Mit143 locus showed strain specificity. In each case, the lost allele derived from the CcS-13 resistant strain. Our current results and previously done) linkage analysis [8] let us to suspect existence of a putative tumor suppressor gene for gamma-radiation-induced lymphoma at the region of murine chromosome 5.