Ku70/80 nonhomologous end-joining activity is essential for resolving random DNA double-strand breaks, and the Ku70/80 protein complex has been proposed as ‘‘caretaker’’ of genomic stability.We studied the Ku70/80 heterodimer activity in a patient a¡ected by multiple basal cell carcinomas with a personal history of moderate exposure to ionizing radiation. The Ku70/80 DNAbinding activity was analyzed, by electrophoretic mobility shift assay, in ¢ve tumor biopsies from di¡erent sites and at distinct clinical stages, and in three matched normal skin samples from the same patient. As control normal tissues from healthy individuals were also tested. The ¢ve basal cell carcinomas were classi¢ed as ‘‘non aggressive’’ and ‘‘aggressive’’ on the basis of morphologic parameters and expression of the molecular markers bcl-2, Ki67/MIB1, and p53. A 62% increase in the Ku70/80 DNA-binding activity was found in normal skin from the patient, compared to unexposed individuals (po0.0001). The nuclear activity of the heterodimer was further increased in nonaggressive basal cell carcinomas compared to both matched normal skin from the patient (31%, p¼0.0001) and tissues from healthy controls (73%, p¼0.0001). Strikingly, the two aggressive basal cell carcinomas tested showed very low Ku70/80 DNA-binding activity with a reduction of 87% compared to normal skin from the patient (po0.0001) and 64% compared to controls (p¼0.001). Although these results are limited to only one patient, together with other recent studies they support the hypothesis that downregulation of the nonhomologous end-joining pathway may be associated with tumor progression.

Differential modulation of Ku70/80 DNA-binding activity in a patient with multiple basal cell carcinomas

POETA, Maria Luana;
2003-01-01

Abstract

Ku70/80 nonhomologous end-joining activity is essential for resolving random DNA double-strand breaks, and the Ku70/80 protein complex has been proposed as ‘‘caretaker’’ of genomic stability.We studied the Ku70/80 heterodimer activity in a patient a¡ected by multiple basal cell carcinomas with a personal history of moderate exposure to ionizing radiation. The Ku70/80 DNAbinding activity was analyzed, by electrophoretic mobility shift assay, in ¢ve tumor biopsies from di¡erent sites and at distinct clinical stages, and in three matched normal skin samples from the same patient. As control normal tissues from healthy individuals were also tested. The ¢ve basal cell carcinomas were classi¢ed as ‘‘non aggressive’’ and ‘‘aggressive’’ on the basis of morphologic parameters and expression of the molecular markers bcl-2, Ki67/MIB1, and p53. A 62% increase in the Ku70/80 DNA-binding activity was found in normal skin from the patient, compared to unexposed individuals (po0.0001). The nuclear activity of the heterodimer was further increased in nonaggressive basal cell carcinomas compared to both matched normal skin from the patient (31%, p¼0.0001) and tissues from healthy controls (73%, p¼0.0001). Strikingly, the two aggressive basal cell carcinomas tested showed very low Ku70/80 DNA-binding activity with a reduction of 87% compared to normal skin from the patient (po0.0001) and 64% compared to controls (p¼0.001). Although these results are limited to only one patient, together with other recent studies they support the hypothesis that downregulation of the nonhomologous end-joining pathway may be associated with tumor progression.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11586/77819
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