Biomedical subjects

F Z Bischoff

Publications and source records attributed to F Z Bischoff.

29 records · Page 2Linked to original sources

PubMed1995

Genomic instability due to germline p53 mutations drives preneoplastic progression toward cancer in human cells.

Cells heterozygous for mutations in p53 demonstrate extreme genomic instability and develop mutations detectable at the chromosome level as well as the molecular level. This genomic instability causes initially nontumorigenic ras-expressing immortal LFS cells to progress to a tumorigenic state presumably due to additional mutational events. It is not surprising that LFS families with these p53 mutations develop the additional mutations necessary for cancer to occur at such high frequencies. This observation is consistent with increased cancer rates in these families being due to abrogation of a rate limiting step rather than a rate expected for one less step in a multistep carcinogenic process. Although p53 has been shown to be able to function as a transcription factor, mutations in p53 appear to affect genomic stability in LFS fibroblasts with double minutes and telomeric associations being prominent early events. One possibility is that p53 controls the expression of genes required for fidelity of replication or telomerase activity. Alternatively p53 may itself be a replication factor like the transcription factor CTF. In the future, we plan to investigate whether p53 plays a direct role in replication.

Animals↗

PubMed1995

Single cell analysis demonstrating somatic mosaicism involving 11p in a patient with paternal isodisomy and Beckwith-Wiedemann syndrome.

Partial isodisomy of 11p has been observed in some patients with Beckwith-Wiedemann syndrome. In this study, we demonstrate somatic mosaicism directly through PCR and single cell analysis on blood lymphocytes from a patient with Beckwith-Wiedemann syndrome. Whole genome amplification was performed on single cells and the resultant product was subjected to locus specific microsatellite marker analysis using PCR. Two populations of cells were detected, a population of cells with normal biparental inheritance for chromosome 11 and a population of cells with partial paternal isodisomy of 11p between markers D11S922 (11p15.5) and D11S904 (11p14-p13). These results are consistent with somatic recombination resulting in mosaicism for paternal isodisomy. The use of single cell PCR is ideal for studying the distribution of mosaicism within and between tissues and has been used in this study to identify a cell line with uniparental disomy in a patient with Beckwith-Wiedemann syndrome.

Adult↗

PubMed1994

Estimates of aneuploidy using multicolor fluorescence in situ hybridization on human sperm.

Single color fluorescence in situ hybridization (FISH) has been utilized on sperm to estimate nondisjunction rates for chromosomes 1, 12, 15, 16, X and Y. Using single-color FISH, one cannot distinguish nonhybridization from nullisomy nor disomy from diploidy. In order to provide an internal control, a multicolor FISH strategy was employed. Satellite probes specific for 13 human chromosomes were used on multiple semen samples from two normal donors. Two or three probes were hybridized simultaneously and scored by two independent observers. Over all experiments, 40,641 sperm were analyzed. The majority of autosomes had no significant difference in aneuploidy between chromosomes or between donors. However, a significant difference was observed for chromosome 18 between donors (chi 2(2) = 7.078, 0.025 < P < 0.05). Additionally, no significant difference was found between donors for sex chromosome aneuploidy. The frequency of sex chromosome aneuploidy was similar to that seen in paternally derived 47,XXY and 47,XYY conceptuses. Furthermore, 0.15% of sperm were found to be diploid. Based on the results of this study, as much as 19% of all sperm may be chromosomally abnormal. This method proved to be useful for determining aneuploidy of human chromosomes in sperm and valuable in exploring whether individual differences of nondisjunction exist.

Adult↗

PubMed1993

A method to isolate DNA from small archival tissue samples for p53 gene analysis.

The tumor suppressor gene p53 is involved in predisposition to a variety of human cancers, including those from Li-Fraumeni cancer family syndrome patients. Studies of inheritance of p53 germline mutations require confirmation of the mutation in the tumors from family members. These studies, as well as other retrospective studies of tumor specific mutations, are often hampered by a lack of available fresh or frozen tumor tissue samples for DNA extraction to confirm the suspected p53 mutation. Here we describe a simple technique for DNA isolation that permits mutational analysis of p53 from minimal amounts of paraffin-embedded archival tissue samples.

Base Sequence↗

PubMed1992

Wild-type p53 restores cell cycle control and inhibits gene amplification in cells with mutant p53 alleles.

Loss of cell cycle control and acquisition of chromosomal rearrangements such as gene amplification often occur during tumor progression, suggesting that they may be correlated. We show here that the wild-type p53 allele is lost when fibroblasts from patients with the Li-Fraumeni syndrome (LFS) are passaged in vitro. Normal and LFS cells containing wild-type p53 arrested in G1 when challenged with the uridine biosynthesis inhibitor PALA and did not undergo PALA-selected gene amplification. The converse occurred in cells lacking wild-type p53 expression. Expression of wild-type p53 in transformants of immortal and tumor cells containing mutant p53 alleles restored G1 control and reduced the frequency of gene amplification to undetectable levels. These studies reveal that p53 contributes to a metabolically regulated G1 check-point, and they provide a model for understanding how abnormal cell cycle progression leads to the genetic rearrangements involved in tumor progression.

Aspartic Acid↗

PubMed1991

Tumorigenic transformation of spontaneously immortalized fibroblasts from patients with a familial cancer syndrome.

Immortal cell lines arose spontaneously during in vitro culture of initially normal fibroblasts, MDAH041 and MDAH087, from patients with Li-Fraumeni familial cancer syndrome. Fibroblasts from a control donor, MDAH170, maintained a normal morphology and senesced at 31 population doublings. The immortal fibroblasts have several properties of transformed cells. In addition to having acquired an altered morphology and chromosomal anomalies, MDAH041 and MDAH087 have escaped from senescence, growing beyond 300 and 100 population doublings (pd), respectively. As early as 50 pd, these cells can be transformed by an activated H-ras oncogene to form tumors in nude mice. However, MDAH041 immortal cells were resistant to tumorigenic transformation by transfection with the v-abl oncogene.

Animals↗

PubMed1990

Spontaneous abnormalities in normal fibroblasts from patients with Li-Fraumeni cancer syndrome: aneuploidy and immortalization.

Families of patients with the Li-Fraumeni cancer syndrome have an inherited pattern of sarcomas and various other types of cancers that follow a dominant mode of transmission, an early age of onset, and exhibit multiple primary tumors. As soft tissue sarcomas (including fibrosarcomas) are frequently observed with this syndrome, the in vitro growth characteristics of fibroblasts derived from skin biopsies of Li-Fraumeni syndrome patients were studied. Control fibroblasts maintained a normal morphology and eventually senesced in culture. Fibroblasts from seven of eight affected individuals developed changes in morphology, anchorage-independent growth, and chromosomal abnormalities. In a fashion similar to that of fibroblasts from normal donors they underwent a growth crisis during which their growth was slow, but they continued to grow past the point at which control samples had stopped dividing (35 population doublings). Fibroblasts from Li-Fraumeni cancer patients escape senescence, growing well beyond 35 population doublings with growth rates similar to early-passage cells. Patient fibroblasts maintain the morphology of a transformed cell but remain nontumorigenic in nude mice. These observations of the behavior of fibroblasts from patients with the Li-Fraumeni syndrome may have predictive value for the determination of gene carriers within these families who are at high risk of cancer.

Aneuploidy↗

PubMed1990

Germ line p53 mutations in a familial syndrome of breast cancer, sarcomas, and other neoplasms.

Familial cancer syndromes have helped to define the role of tumor suppressor genes in the development of cancer. The dominantly inherited Li-Fraumeni syndrome (LFS) is of particular interest because of the diversity of childhood and adult tumors that occur in affected individuals. The rarity and high mortality of LFS precluded formal linkage analysis. The alternative approach was to select the most plausible candidate gene. The tumor suppressor gene, p53, was studied because of previous indications that this gene is inactivated in the sporadic (nonfamilial) forms of most cancers that are associated with LFS. Germ line p53 mutations have been detected in all five LFS families analyzed. These mutations do not produce amounts of mutant p53 protein expected to exert a trans-dominant loss of function effect on wild-type p53 protein. The frequency of germ line p53 mutations can now be examined in additional families with LFS, and in other cancer patients and families with clinical features that might be attributed to the mutation.

Amino Acid Sequence↗

PubMed1990

The current state of oncogenes and cancer: experimental approaches for analyzing oncogenetic events in human cancer.

The development of cancer is a multistage process. The activation of proto-oncogenes and the inactivation of tumor suppressor genes play a critical role in the induction of tumors. Using human cell model systems of carcinogenesis, we have studied how oncogenes, tumor suppressor genes, and recessive cancer susceptibility genes participate in this multistep process. Normal human cells are resistant to the transforming potential of oncogenes, such as ras oncogenes, which are activated by specific point mutations. Since as many as 40% of some tumor types contain activated ras oncogenes, a preneoplastic transition in multistage carcinogenesis must involve changing from an oncogene-resistant stage to an oncogene-susceptible stage. The analysis of such critical steps in carcinogenesis using rodent systems has usually not represented the human disease with fidelity. In order to study this carcinogenic process, we have developed human cell, in vitro systems that represent some of the genetic changes that occur in cellular genes during human carcinogenesis. Using these systems, we have learned some of the functions of dominant activated-transforming oncogenes, tumor suppressor genes, and cellular immortalization genes and how they influence the carcinogenic process in human cells. Using our understanding of these processes, we are attempting to clone critical genes involved in the etiology of familial cancers. These investigations may help us to develop procedures that allow us to predict, in these cancer families, which individuals are at high risk for developing cancer.

Animals↗

PubMedDate not supplied

Noninvasive determination of fetal RhD status using fetal DNA in maternal serum and PCR.

OBJECTIVE: Because prenatal testing of fetal RhD status by amniocentesis carries small yet finite risks to the fetus and mother, this study sought to determine whether fetal DNA in maternal serum could be used to detect fetal RhD status by polymerase chain reaction (PCR). METHODS: A retrospective analysis was made of frozen serum specimens from 20 sensitized RhD-negative pregnant women (ranging from 15.0 to 36.0 weeks' gestation) who were confirmed by serology at birth to have been carrying RhD-positive fetuses. Eleven serum specimens from RhD-negative individuals served as controls. DNA was isolated from serum and used in two PCR-based methods to detect a 99 base pair (bp) DNA fragment specific for the RhD gene and a 113 bp fragment specific for the RhCE gene as control. RESULTS: Overall, in 14 (70%) of 20 RhD-positive fetuses the 99 base pair RhD-specific PCR product was detected. There was no false positive detection among the 11 control serum specimens. CONCLUSION: The results illustrate the ability to detect fetal RhD sequences in maternal serum of sensitized women. Moreover, the findings demonstrate that fetal single-gene disorders can be detected prenatally by using DNA isolated only from maternal serum.

Blood Grouping and Crossmatching↗

PubMedDate not supplied

Heritability and molecular genetic studies of endometriosis.

Endometriosis is a common disease defined as the growth of endometrial tissue outside the uterine cavity that often results in a vast array of gynaecological problems including dyspareunia, dysmenorrhoea, pelvic pain and infertility. Despite the increasing evidence that supports a genetic component to this common gynaecological condition, the basic aetiology and pathogenesis of endometriosis remain unknown. It is likely that endometriosis is a common polygenic/multifactorial disease caused by an interaction between multiple genes as well as the environment. Such conditions do not have a clear Mendelian pattern of inheritance. Recent molecular cytogenetic studies on endometriotic tissue and an established endometriosis-derived cell line provide novel evidence that acquired chromosome-specific alterations may be involved in endometriosis, possibly reflecting clonal expansion of chromosomally abnormal cells. Molecular DNA studies examining the role of loss of heterozygosity in endometriotic lesions has identified candidate tumour suppressor gene loci, including 5q, 6q, 9p, 11q and 22q, that may play a role in the malignant transformation of endometriotic implants to endometrioid ovarian cancers. Evidence of mutations in the tumour suppressor PTEN gene in the endometrioid subtype of epithelial ovarian cancer further suggests that somatic genetic alterations represent early events in the transformation of benign endometriotic cells. Genetic factors are also likely to influence individual susceptibility to endometriosis. There is now evidence that heritable allelic differences in drug-metabolizing enzymes play an important role in the development of endometriosis. Further studies are warranted to identify major susceptibility gene(s) and the mechanism involved in endometriosis to assist in the development of better methods for early detection, diagnosis and prevention.

Endometrial Neoplasms↗