Multistage Friend erythroleukemia: independent origin of tumor clones with normal or rearranged p53 cellular oncogenes

Abstract

The erythroleukemia induced by Friend virus complex in adult mice is a multistage malignancy characterized by the emergence, late in the disease, of tumorigenic cell clones. We have previously shown that a significant proportion of these clones have unique rearrangements in their cellular p53 oncogene. The clonal relationships among Friend tumor cells isolated in the late stages of Friend erythroleukemia were analyzed by examining the unique integration site of Friend murine leukemia virus and the unique rearrangement in their cellular p53 oncogene. The majority of clones isolated from individual mice infected with Friend virus were clonally related as judged by the site of Friend muriiie leukemia virus integration. However, Southern gel analysis of DNA from individual Friend cell clones indicated that all of the clones with a normal p53 gene from the same mice were clonally related, but were unrelated to the Friend cell lines with a rearranged p53 gene. These results suggest that Friend tumor cells with rearrangements in their p53 gene arise as the result of a unique transformation event, rather than by progression from already existing tumor cells with a normal p53 gene. They also suggest that such rearrangements in the p53 gene confer a strong selective advantage to these cells in vivo.

A tagged helper-free Friend virus causes clonal erythroblast immortality by specific proviral integration in the cellular genome

“…This inherent difficulty has been exacerbated because SFFV has been almost exclusively analyzed in the presence of helper MuLV, which creates opportunities for multiple infections of tumor cells (21)(22)(23) and for continual infection of previously uninfected erythroblasts in vivo. Despite these difficulties, evidence has accumulated that Friend disease can be separated into an initial polyclonal erythroblastosis in which the proliferating cells have limited lifespans and continue to differentiate (9,17,37,40) and a later stage that may be clonal in which the cells have a greater self-renewal capability (5,21,22). The numbers of steps involved in this progression and their temporal relationships have not been previously known.…”

“…at 42°C for 4 h in a solution consisting of 50% formamide, 5 x pol env LTR SSPE (lx SSPE is 0.15 M NaCl, 0.01 M NaH2PO4, and pL2-6K 0.001 M EDTA), 5x Denhardt solution, 0.1% sodium dodecyl sulfate, and 200 ,ug of salmon sperm DNA per ml. S ch h 3sperm DNA per ml).…”

“…Moreover, SFFV pathogenesis is restricted to mice (6,29,36). Despite these difficulties, previous studies have suggested that the progression of Friend erythroleukemia involves selective outgrowth of cell clones that have a proliferative advantage (5,21,22). Moreau-Gachelin and co-workers have analyzed the DNA from Friend leukemia cells by using a small SFFV-derived hybridization probe that reacts in stringent conditions with only a few endogenous sequences of the murine genome (21).…”

The p53 gene and its role in human brain tumors

“…This led to the initial conclusion that thep53 gene is a dominantly acting oncogene. The first indications of its role in the process of naturally occurring in vivo tumorigenesis came from the detection of gene rearrangements in murine (Ben David et al, 1988;Chow et al, 1987) and human leukemias (Prokocimer et al, 1986) as well as in human osteogenic sarcomas (Masuda et al, 1987). However, since these genetic events typically caused either deletions or gross rearrangement of the p53 gene, it appeared unlikely that in these cases the gene was being activated as would be expected for an oncogene.…”

Integration of Friend murine leukemia virus into both alleles of the p53 oncogene in an erythroleukemic cell line

“…Several leukemia and tumor cell lines with rearrangement of the p53 oncogene have been described (2,16,18,19,27,32,33). These rearrangements result in loss of p53 protein or production of truncated forms of the p53 protein.…”