RESUMO
Nucleotide excision repair (NER) is an ordered process in nonmalignant cells, in both human and nonhuman systems. We previously reported that in human brain there is discordant mRNA expression of excision repair cross-complementing (ERCC) 1 and ERCC2 in malignant tissues, concurrent with excellent concordance of these genes in nonmalignant tissues from the same patients. Here we have extended these studies to compare low-grade tumors to high-grade tumors and to include ERCC3 (which links DNA repair with DNA transcription) and ERCC6 (which is essential for gene-specific repair). Glial tumor and adjacent normal brain specimens from 19 individuals were studied. Paired malignant and nonmalignant tissues were obtained from 12 of these patients. For ERCC3, there was excellent concordance of mRNA expression between malignant and nonmalignant tissues from the same individuals (P = 0.003). For ERCC6, no concordance was observed (P = 0.314). Tumor tissue from patients with high-grade gliomas exhibited marked discordance of mRNA expression patterns in situations in which good concordance was observed in tumor tissue from low-grade gliomas. We previously established that malignant brain tumors show increased disorder of genes in the NER process, as compared with nonmalignant tissues. These data suggest that increasing disorder in the NER process may occur as cells move from low-grade to high-grade malignancy.
Assuntos
Neoplasias Encefálicas/genética , Encéfalo/fisiologia , DNA Helicases/genética , Reparo do DNA , Proteínas de Ligação a DNA/genética , Proteínas de Drosophila , Regulação Neoplásica da Expressão Gênica , Glioma/genética , Astrocitoma/genética , Astrocitoma/terapia , Neoplasias Encefálicas/terapia , Enzimas Reparadoras do DNA , Glioblastoma/genética , Glioblastoma/terapia , Glioma/terapia , Humanos , Oligodendroglioma/genética , Oligodendroglioma/terapia , Proteínas de Ligação a Poli-ADP-Ribose , RNA Mensageiro/genética , RNA Neoplásico/genética , Análise de RegressãoRESUMO
Perturbation of the DNA repair process appears to be responsible for the occurrence of a number of human diseases, which are usually associated with a propensity to develop internal malignancies and/or disorders of the central nervous system. We have been interested in the possibility that a subtle abnormality in DNA repair competency might be associated with the transformation of nonmalignant cells to the malignant state. To study this question, we assayed malignant and nonmalignant brain tissues from 19 individuals for mRNA expression levels of the human DNA repair genes ERCC1, ERCC2, and XPAC and for differential splicing of the ERCC1 transcript. We separately compared expression levels of these genes in the following situations: concordance of expression within malignant tissues; concordance of expression within nonmalignant tissues; concordance between malignant and nonmalignant tissues within individuals of the cohort; and concordance of gene expression between two nonmalignant tissue sites within a single individual. Linear regression analyses of mRNA values obtained suggested orderly concordance of these three DNA repair genes in nonmalignant tissues within the patient cohort and an excellent concordance of these genes between two separate biopsy sites from the same individual. In contrast, malignant tissues showed disruption of concordance between the full-length ERCC1 transcript and ERCC2, which have excision and helicase functions, respectively. Furthermore, within the same individuals, malignant tissues were discordant with nonmalignant tissues for ERCC1 and ERCC2, although concordance for XPAC was preserved. These data suggest that one molecular characteristic of human malignancy may be the disruption of the normal relationship between the excision and the helicase functions of the nucleotide excision repair pathway.
Assuntos
Neoplasias Encefálicas/metabolismo , Encéfalo/metabolismo , DNA Helicases , Reparo do DNA , Endonucleases , Proteínas/genética , RNA Mensageiro/análise , Fatores de Transcrição , Dano ao DNA , Proteínas de Ligação a DNA/genética , Humanos , Reação em Cadeia da Polimerase , Proteína de Xeroderma Pigmentoso Grupo A , Proteína Grupo D do Xeroderma PigmentosoRESUMO
Taxol and cisplatin are the two most effective agents discovered to date for treating advanced-stage cancer of the ovary. Learning how best to combine these agents is the focus of preclinical and clinical studies conducted at a number of institutions. Taxol's effect on cellular sensitivity to cisplatin was studied in paired cisplatin-sensitive A2780 and cisplatin-resistant A2780/CP70 human ovarian cancer cell lines. Cisplatin growth curves were generated under conditions of specific sequencing with Taxol, and IC50s (concentrations at which growth is inhibited to 50% of control) for cisplatin were obtained and compared. Taxol was used at an IC10 dose in all experiments. Taxol treatments were for 24 hours and cisplatin treatments were for 1 hour in all experiments. Dimethyl sulfoxide (DMSO) was the diluent for all Taxol stock solutions. Separately, the effects of Taxol and DMSO on cisplatin cellular accumulation were measured. End points reported include measures of cytotoxicity and Taxol effects on cisplatin cellular accumulation. Using a microculture tetrazolium assay, cisplatin growth curves were obtained under the influence of Taxol, at a Taxol dose of 3 nM for both cell lines. DMSO alone had no effect on tumor cell growth. In A2780 cells, the influence of Taxol on cisplatin cytotoxicity was modest, whereas cisplatin-induced cell kill was augmented 1.5-fold when cisplatin was given immediately after Taxol. In A2780/CP70 cells, Taxol augmented cisplatin-induced cell kill by 30-fold when cisplatin was given immediately after Taxol; 75-fold when cisplatin was given 24 hours after completion of Taxol; and 19-fold when cisplatin was given 48 hours after completion of Taxol.(ABSTRACT TRUNCATED AT 250 WORDS)
