Non-random chromosome rearrangements in herpes simplex virus type 1 transformed diploid CHEF cells

The effects of Herpes simplex virus type 1 (HSV-1) on diploid, non-tumourigenic Chinese hamster embryo fibroblasts (CHEF/18-1D-3) were studied. Six independent lines transformed by HSV-1 alone or by HSV-1 in combination with acyclovir or aqueous tobacco extract were isolated. In contrast to uninfected CHEF/18-1D-3 cells, all transformants grew in soft agar and were tumourigenic in nude mice. Neither infectious virus nor viral antigens could be detected in any of the lines. Cytogenetic analysis revealed clonal chromosome abnormalities in all lines including trisomy for the long arm of chromosome 3 in five lines. In three of these the extra 3q was translocated onto 6p. All lines showed loss of the corresponding 3p arm. The remaining line had a hypodiploid stemline with loss of one chromosome 7. This line also showed a pronounced chromosomal instability with a multitude of mainly sporadic rearrangements. These results show that HSV-1 induced transformation and tumourigenesis in CHEF cells is associated with the induction of chromosome rearrangements, in particular trisomy for 3q.