title: Nonhereditary p53 mutations in T-cell acute lymphoblastic leukemia are associated with the relapse phase.
abstract: We have previously reported that greater than 60% of human leukemic T-cell lines possess mutations in the p53 tumor suppressor gene. To determine whether T-cell acute lymphoblastic leukemia (T-ALL) patient samples possess p53 mutations, we screened peripheral blood-and bone marrow-derived leukemia samples, taken at diagnosis and at relapse, for p53 mutations. Exons 4 through 9 and selected intron regions of the p53 gene were analyzed using polymerase chain reaction-single-strand conformation polymorphism and direct sequencing. p53 mutations were found in 0 of 15 T-ALL diagnosis samples, as compared with 10 of 36 (28%) T-ALL relapse samples. To determine whether p53 mutations play a role in the recurrence (relapse) of T-ALL, two special groups of T-ALL patients were studied: (1) a group of 8 relapse patients whose disease was refractory to chemotherapeutic treatment, and (2) a group of 6 "paired" T-ALL cell samples from patients for whom we possess both diagnosis and relapse samples. Three of 8 relapsed patients (37.5%) whose disease was refractory to the reinduction of remission by chemotherapy possessed missense mutations of the p53 gene. All 3 cases had mutations in exon 5. Among the paired samples, 3 of 6 patients harbored p53 mutations at disease recurrence, but possessed only wild-type p53 alleles at diagnosis. One case had mutation on exon 4, 1 case in exon 5, and 1 case in exon 8 with loss of heterozygosity. These data clearly indicate that recurrence of T-ALL is associated with missense mutations in p53. Our results indicate that (1) mutations of p53 do occur in T-ALL in vivo, and such mutations are associated with the relapse phase of the disease; and (2) p53 mutation is involved in the progression of T-ALL. This conclusion is supported by our observation that the introduction of T-ALL-derived mutant p53 expression constructs into T-ALL cell lines further increases their growth rate in culture, enhances cell cloning in methylcellulose, and increases tumor formation in nude mice.
authors.affiliation: Department of Biology/Cancer Center, University of California, San Diego, La Jolla 92093-0063.
authors.forename: M H
authors.initials: MH
authors.lastname: Hsiao
authors.forename: A L
authors.initials: AL
authors.lastname: Yu
authors.forename: J
authors.initials: J
authors.lastname: Yeargin
authors.forename: D
authors.initials: D
authors.lastname: Ku
authors.forename: M
authors.initials: M
authors.lastname: Haas
mesh_terms: D001483:Base Sequence; D002872:Chromosome Deletion; D016158:Genes, p53; D006801:Humans; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D012008:Recurrence