Alterations of p53 and c-myc in the clonal evolution of malignant lymphoma.
We derived the lymphoma cell lines OCI-Ly 13.1 and OCI-Ly 13.2 from a patient with non-Hodgkin's lymphoma at the time of presentation and during chemotherapy-resistant relapse. These lines were of T-cell phenotype and contained the identical T-cell receptor beta-chain rearrangement, indicating that both lines were members of the same malignant clone. The lines differed in their growth characteristics; OCI-Ly 13.1 grew slowly and required growth factors for colony formation, whereas OCI-Ly 13.2 grew rapidly and formed colonies without addition of growth factors. To test whether or not these biologic differences were associated with specific genetic changes, we evaluated the status of the c-myc and p53 genes of both cell lines. The p53 and c-myc genes of OCI-Ly 13.1 were in germline configuration and produced normal-sized transcripts. The p53 protein expressed in OCI-Ly 13.1 was recognized by the anti-p53 monoclonal antibody, PAb240, indicating a conformation typical of p53 proteins expressed by p53 alleles containing a missense mutation. However, sequencing studies of the entire p53 coding region did not reveal any point mutations. In contrast, the cell line OCI-Ly 13.2 contained structural abnormalities of both the c-myc and p53 genes. In addition, one of the p53 alleles was lost as determined by a cDNA probe for the p53 gene (17p 13.1) and the YNZ22.1 probe (17p 13.3). These changes resulted in the absence of p53 protein and mRNA in OCI-Ly 13.2 as detected by immunoprecipitation and Northern blot analysis, respectively. They may be a reflection of disease progression and may be associated with the altered behavior of the malignant cell population within the patient and in vitro.
Chang
H
H
Ontario Cancer Institute, University of Toronto, Ontario, Canada.
Benchimol
S
S
Minden
M D
MD
Messner
H A
HA
D001483:Base Sequence; D015139:Blotting, Southern; D015333:Gene Rearrangement, beta-Chain T-Cell Antigen Receptor; D016259:Genes, myc; D016158:Genes, p53; D006801:Humans; D008223:Lymphoma / Q000235:genetics*; D008969:Molecular Sequence Data; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000032:analysis
D016159:Tumor Suppressor Protein p53