Abstract
Lymphomas induced by radiation in the cross between BALB/c and STS, a susceptible and a resistant strain for lymphomagenesis, show a wide-range of allelic loss on chromosome 4, where preferential loss of the STS allele occurs. This suggests the existence of tumor susceptibility gene(s) on chromosome 4. In the present study, by the use of C.S congenic strains with STS-derived portions of chromosome 4 on the BALB/c background possible correlation of the regions bearing lymphoma susceptibility genes with LOH was examined. Lymphomas were induced in animals with fractionated X-irradiation according to Kaplan's protocol and examined for LOH of chromosome 4. The order and map positions in centimorgan (cM) for microsatellite markers are as follows: D4Mit39(11)-D4Mit17(31)-D4Mit7(36)-D4Mit86(38)-D4Mit302(43)-D4Mit9(45) -D4Mit31(51), spanning the proximal-middle chromosome 4. Allelic loss was seen in 11 (32%) of 34 (C.S17-31 x BALB/c)F1 as well as in 10 (29%) of 34 (C.S302-9 x BALB/c)F1, with preferential loss of the STS allele (10/11 and 9/10). On the other hand, both (C.S39-86 x BALB/c)F2 and (C.S7-86 x BALB/c)F2.scarcely showed LOH (<5%). The results suggested that the wide-ranging LOH. was a concomitant event of allelic loss in a small segment bearing a potential tumor susceptibility gene in the middle chromosome 4.
