Trisomy for chromosome 1q in a pontine astrocytoma

Poly(ADP-ribose) polymerase: a guardian angel protecting the genome and suppressing tumorigenesis

Poly(ADP-ribosyl)ation is an immediate cellular response to DNA damage generated either exogenously or endogenously. This post-translational modification is catalyzed by poly(ADP-ribose) polymerase (PARP, PARP-1, EC 2.4.2.30). It is proposed that this protein plays a multifunctional role in many cellular processes, including DNA repair, recombination, cell proliferation and death, as well as genomic stability. Chemical inhibitors of the enzyme, dominant negative or null mutations of PARP-1 cause a high degree of genomic instability in cells. Inhibition of PARP activity by chemical inhibitors renders mice or rats susceptible to carcinogenic agents in various tumor models, indicating a role for PARP-1 in suppressing tumorigenesis. Despite the above observations, PARP-1 knockout mice are generally not prone to the development of tumors. An enhanced tumor development was observed, however, when the PARP-1 null mutation was introduced into severely compromised immune-deficient mice (a mutation in DNA-dependent protein kinase) or mice lacking other DNA repair or chromosomal guardian molecules, such as p53 or Ku80. These studies indicate that PARP-1 functions as a cofactor to suppress tumorigenesis via its role in stabilization of the genome, and/or by interacting with other DNA strand break-sensing molecules. Studies using PARP-1 mutants and chemical inhibitors have started to shed light on the role of this protein and of the specific protein post-translational modification in the control of genomic stability and hence its involvement in cancer.

Cytogenetics of pediatric central nervous system tumors

A cytogenetic analysis was performed on short-term cultures of 43 previously untreated childhood central nervous system neoplasms of various histology. The cells were obtained from pediatric patients, none of whom had received therapy before karyotypic evaluation. Successful chromosome studies were performed on 24 tumors. The most commonly detected structural abnormalities involved chromosomes 1 and 17. Other structural chromosome abnormalities involved chromosomes 3, 6, 8, 9, 11, 12, and 20.

Cytogenetic analysis of 109 pediatric central nervous system tumors

Reports of cytogenetic abnormalities in pediatric central nervous system (CNS) tumors are important for collection and comparison of large numbers of karyotypes of primary CNS neoplasms to produce statistically significant correlations. We report cytogenetic results of 119 samples of pediatric CNS tumors from 109 patients. Tumors included 33 low-grade astrocytomas, 18 high-grade astrocytomas, 14 gangliogliomas, 13 ependymomas, 17 primitive neuroectodermal tumors (PNET), three choroid plexus papillomas and carcinomas, and a miscellaneous group of 20 rare primary CNS tumors and metastases. In each group, cytogenetic results were correlated with histologic subtype and survival. The study indicated specific chromosome abnormalities in different groups of tumors. Low-grade astrocytomas showed mostly numeric abnormalities with gains of chromosome 7, high-grade astrocytomas showed differences from karyotypic changes observed in adults in lacking double minutes (dmin) and monosomy 10. The ependymoma group showed the largest proportion of abnormal karyotypes with frequent involvement of chromosome 6 and 16. Chromosome 6 was the single most common abnormal chromosome in this study, closely followed by chromosomes 1 and 11. Pediatric CNS neoplasms differ from adult tumors cytogenetically as well as histologically and biologically.

Age-related nonrandom chromosomal abnormalities in human low-grade astrocytomas

We report a cytogenetic investigation of 55 low-grade astrocytomas in 52 patients, 15 children and 37 adults. In addition to numerical aberrations such as trisomy 7 and gonosomal losses, we found structural and/or numerical aberrations of chromosome 1 in eight astrocytomas. There was a striking difference between the rearranged chromosomes in pediatric and adult patients. Whereas the pediatric tumors revealed monosomies 1p with accompanying trisomy 1q, the astrocytomas in adults showed partial or complete monosomies 1q.

Molecular cytogenetic analysis of a medulloblastoma with isochromosome 17 and double minutes

Cytogenetic analysis of a medulloblastoma revealed two abnormal cell lines of 48,XY, +8, +8, -14, +der(14)t(1;14)(q11;p11),i(17q) and 51,XY, +5, +6, +8, +8, -14 + 20, +der (14)t(1;14)(q11;p11),i(17q), + dmin. The finding of double minute chromosomes in some medulloblastomas has been associated with amplification of the c-myc or N-myc oncogenes. We were unable to detect gene amplification with these probes by Southern blot analysis.

Evolution of tumor chromosome abnormalities after therapy in a pediatric astrocytoma

Chromosome studies originally performed on a patient with an untreated pontine astrocytoma showed a trisomy for 1q as the sole chromosome aberration. After the patient received radiation and chemotherapy, subsequent study indicated the presence of the original trisomy for 1q, as well as trisomy for chromosomes 2, 3q, and 17, in a tumor that now, histologically, is glioblastoma multiforme. In addition to the numerical aberrations, chromosome rearrangements were observed, involving translocation breakpoints that have been reported as "hot spots" associated with the clastogenetic effect of ionizing radiation.