RESUMO
Nonsynonymous TP53 exon 4 single-nucleotide polymorphism (SNP), R72P, is linked to cancer and mutagen susceptibility. R72P associations with specific cancer risk, particularly hematological malignancies, have been conflicting. Myelodysplastic syndrome (MDS) with chromosome 5q deletion is characterized by erythroid hypoplasia arising from lineage-specific p53 accumulation resulting from ribosomal insufficiency. We hypothesized that apoptotically diminished R72P C-allele may influence predisposition to del(5q) MDS. Bone marrow and blood DNA was sequenced from 705 MDS cases (333 del(5q), 372 non-del(5q)) and 157 controls. Genotype distribution did not significantly differ between del(5q) cases (12.6% CC, 38.1% CG, 49.2% GG), non-del(5q) cases (9.7% CC, 44.6% CG, 45.7% GG) and controls (7.6% CC, 37.6% CG, 54.8% GG) (P=0.13). Allele frequency did not differ between non-del(5q) and del(5q) cases (P=0.91) but trended towards increased C-allele frequency comparing non-del(5q) (P=0.08) and del(5q) (P=0.10) cases with controls. Median lenalidomide response duration increased proportionate to C-allele dosage in del(5q) patients (2.2 (CC), 1.3 (CG) and 0.89 years (GG)). Furthermore, C-allele homozygosity in del(5q) was associated with prolonged overall and progression-free survival and non-terminal interstitial deletions that excluded 5q34, whereas G-allele homozygozity was associated with inferior outcome and terminal deletions involving 5q34 (P=0.05). These findings comprise the largest MDS R72P SNP analysis.
Assuntos
Deleção Cromossômica , Síndromes Mielodisplásicas/genética , Proteína Supressora de Tumor p53/genética , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Frequência do Gene , Humanos , Estimativa de Kaplan-Meier , Masculino , Pessoa de Meia-Idade , Mutação , Síndromes Mielodisplásicas/tratamento farmacológico , Síndromes Mielodisplásicas/patologia , Polimorfismo de Nucleotídeo Único , Resultado do TratamentoAssuntos
Mutação , Síndromes Mielodisplásicas/genética , Doenças Mieloproliferativas-Mielodisplásicas/genética , Transtornos Mieloproliferativos/genética , Proteínas ras/genética , Sequência de Aminoácidos , Sequência de Bases , Mapeamento Cromossômico , Regulação Leucêmica da Expressão Gênica , Humanos , Dados de Sequência Molecular , Síndromes Mielodisplásicas/mortalidade , Doenças Mieloproliferativas-Mielodisplásicas/mortalidade , Transtornos Mieloproliferativos/mortalidade , Proteínas ras/químicaRESUMO
The DNA hypomethylating drug decitabine maintains normal hematopoietic stem cell (HSC) self-renewal but induces terminal differentiation in acute myeloid leukemia (AML) cells. The basis for these contrasting cell fates, and for selective CpG hypomethylation by decitabine, is poorly understood. Promoter CpGs, with methylation measured by microarray, were classified by the direction of methylation change with normal myeloid maturation. In AML cells, the methylation pattern at maturation-responsive CpGs suggested at least partial maturation. Consistent with partial maturation, in gene expression analyses, AML cells expressed high levels of the key lineage-specifying factor CEBPA, but relatively low levels of the key late-differentiation driver CEBPE. In methylation analysis by mass spectrometry, CEBPE promoter CpGs that are usually hypomethylated during granulocyte maturation were significantly hypermethylated in AML cells. Decitabine-induced hypomethylation was greatest at these and other promoter CpGs that are usually hypomethylated with myeloid maturation, accompanied by cellular differentiation of AML cells. In contrast, decitabine-treated normal HSCs retained immature morphology, and methylation significantly decreased at CpGs that are less methylated in immature cells. High expression of lineage-specifying factor and aberrant epigenetic repression of some key late-differentiation driver genes distinguishes AML cells from normal HSCs, and could explain the contrasting differentiation and methylation responses to decitabine.
