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At least 541 records · Page 30Linked to original sources
PubMed2005

Mdm2 in growth signaling and cancer.

Genetic and biochemical evidence have demonstrated a direct link between Mdm2 and cancer development. Elevated expression of Mdm2 is observed in a significant proportion of different types of cancer. The major contribution of Mdm2 to the development of cancer is through a tight inhibition of the activities and stability of the tumor suppressor p53. However, extensive studies over the past few years have identified p53-independent functions of Mdm2, in the regulation of several important cellular processes and multiple signaling pathways. The promotion of cell cycle progression by Mdm2 is mediated via p53 inhibition, and by regulating the pRb/E2F complex. Mdm2 is an important mediator of growth and survival signaling in the PI3K/Akt pathway, an activator of certain steroid hormone receptors, and an inhibitor of the TGF-beta growth restrictive pathway. Thus, the impact on these pathways by deregulated Mdm2, as often observed in cancer, can be oncogenic in a permissible environment. This renders Mdm2 as an important target for the development of anti-cancer drugs.

Animals↗
PubMed1993

Evidence for a major gene effect in early-onset lung cancer.

Genetic segregation analyses that allowed for variable age of onset of lung cancer and smoking history were performed on 337 families, each ascertained through a lung cancer patient. Results indicated compatibility of the data with Mendelian codominant inheritance of a rare major autosomal gene that acts in concert with smoking to predispose carriers to lung cancer, by producing earlier onset of the cancer when controlling for equivalent smoking levels. Segregation at this locus could account for 69% and 47% of the cumulative incidence of lung cancer in individuals up to ages 50 and 60 respectively, but only 22% of all lung cancers in persons up to age 70. This decrease in the importance of the gene's contribution to overall lung cancer rates at later ages is most likely a reflection of an increasing proportion of noncarriers succumbing to the effects of long-term exposure to tobacco. A significant cohort effect was found, most likely due to differing smoking patterns before and after World War I, but in both cohorts the effect of a major locus could not be rejected.

Data Collection↗
PubMed2002

Pancreatic cancer: epidemiology, genetics, and approaches to screening.

Pancreatic cancer is a leading cause of cancer-related mortality. Treatment has limited efficacy, and 5-year survival rates remain less than 5%. Insights from epidemiology and discoveries in molecular genetics have laid the groundwork for a rational screening strategy for high-risk individuals. High-risk populations include those in their 6th to 8th decades of life, those with a family history of pancreatic cancer, and those with a personal history of tobacco smoking. Roughly 10% of cases are due to an inherited genetic susceptibility. Several familial syndromes with known genetic defects have been implicated, but the majority of familial cases result from as yet undefined genes. Acquired mutations have been identified in the oncogenes K-ras and HER2/neu, and in the tumor suppressor genes p16, p53, SMAD4, and BRCA2. No standard for screening or prevention exists, but strategies employing endoscopic, radiologic, and molecular methods to screen high-risk individuals are under investigation.

Adult↗
PubMed2005

Comparative functional genomics for identifying models of human cancer.

Genetically modified mice with overexpressed and/or deleted genes have been used extensively to model human cancer. However, it is uncertain as to what extent the mouse models reproduce the corresponding cancers in humans. We have compared the global gene expression patterns in human and mouse hepatocellular carcinomas (HCCs) in an attempt to identify the mouse models that most extensively reproduce the molecular pathways in the human tumors. The comparative analysis of the gene expression patterns in murine and human HCC indicates that certain genetic mouse models closely reproduce the gene expression patterns of HCC in humans, while others do not. Identification of mouse models that reproduce the molecular features of specific human cancers (or subclasses of specific human cancers) promises to accelerate both the understanding of the molecular pathogenesis of cancer and the discovery of therapeutic targets. We propose that this method, comparative functional genomics, could be effectively applied to the analysis of mouse models for other human cancers.

Animals↗
PubMed1997

K-ras and p53 mutations in hereditary non-polyposis colorectal cancers.

Genetic instability related to defective DNA mismatch repair genes may be involved in the pathogenesis of carcinoma in Hereditary Non-Polyposis Colorectal Cancer (HNPCC). To test that the targets of genetic instability could include critical transforming genes involved in colon tumor progression, we examined 23 colorectal carcinomas in patients with HNPCC in order to detect somatic mutations in K-ras and p53 genes. Using single strand conformation polymorphism followed by direct DNA sequencing, we detected 4 mutations in K-ras gene (17%) and 3 in p53 gene (13%) which change the amino acid sequence of the protein p53. This is significantly lower than in sporadic cancer. Our data suggest that colon cancer in HNPCC might partly involve a distinct pathogenetic mechanism that involves other genes than those altered in sporadic tumors.

Adult↗
PubMed2004

[Relationship between susceptibility and prognosis of laryngeal cancer and genetic polymorphisms in CYP1A1 and GSTM1].

OBJECTIVE: To investigate the relationship between susceptibility and prognosis of laryngeal cancer and genetic polymorphisms in CYP1A1 GSTM1. METHODS: The genetic polymorphisms of CYP1A1 exon-7 and GSTM1 were analyzed by polymorphism-polymerase chain reaction (PCR) technique in peripheral blood leukocytes of 89 laryngeal cancer cases and 164 non-cancer controls. RESULTS: Either in the frequency of CYP1A1 (W, MW, M) and GSTM1 negative individual of laryngeal cancer were significantly higher than that in the controls(P < 0.05). Combined genetype of CYP1A1 and GSTM1, that is CYP1A1 W/GSTM1 (-), CYP1A1 MW/GSTM1 (-), CYP1A1 M/GSTM1 (+), CYP1A1 M/GSTM1 (-) had higher risk than those combined genotypes, which ratios were 1.42 (0.62-3.22), 1.67 (0.7-4.03), 2.55 (1.0-6.54) and 4.02 (1.65-9.79), respectively. Statistic analysis suggested an interaction between smoking and CYP1A1 M/GSTM1 (-) genotypes polymorphisms which increase risk of laryngeal cancer. There was no significant difference in the frequency of CYP1A1, GSTM1 individual with the development and prognosis of laryngeal cancer. CONCLUSION: The present datas suggested that genetic polymorphisms of CYP1A1 and GSTM1 were susceptible to laryngeal cancer. Individuals with CYP1A1 M or GSTM1 (-) had increased risk of developing laryngeal cancer, but individuals with combined CYP1A1 M/GSTM1 (-) and smoking were more susceptible. Genetic polymorphisms of CYP1A1 and GSTM1 are not related with clinic process of laryngeal cancer.

Carcinoma, Squamous Cell↗
PubMed2001

Genetic linkage analysis of prostate cancer families to Xq27-28.

OBJECTIVES: A recent linkage analysis of 360 families at high risk for prostate cancer identified the q27-28 region on chromosome X as the potential location of a gene involved in prostate cancer susceptibility. Here we report on linkage analysis at this putative HPCX locus in an independent set of 186 prostate cancer families participating in the Prostate Cancer Genetic Research Study (PROGRESS). METHODS: DNA samples from these families were genotyped at 8 polymorphic markers spanning 14.3 cM of the HPCX region. RESULTS: Two-point parametric analysis of the total data set resulted in positive lod scores at only two markers, DXS984 and DXS1193, with scores of 0.628 at a recombination fraction (theta) of 0.36 and 0.012 at theta = 0.48, respectively. The stratification of pedigrees according to the assumed mode of transmission increased the evidence of linkage at DXS984 in 81 families with no evidence of male-to-male transmission (lod = 1.062 at theta = 0.28). CONCLUSIONS: Although this analysis did not show statistically significant evidence for the linkage of prostate cancer susceptibility to Xq27-28, the results are consistent with a small percentage of families being linked to this region. The analysis further highlights difficulties in replicating linkage results in an etiologically heterogeneous, complexly inherited disease.

Age Factors↗
PubMed1995

Hereditary breast and ovarian cancer: epidemiology, genetics, screening and predictive testing.

Inherited predisposition to cancer has become an increasingly important part of the practice of clinical genetics. Hereditary breast and ovarian cancer form a significant part of this new field. There are approximately 13,000 new cases of breast cancer diagnosed every year in Canada, and 5% of these can be expected to have a hereditary basis. Large studies implicated a dominant gene with a population frequency of 0.33% and high penetrance. Linkage analysis localised one such gene to chromosome 17q21 in 1990, and 1994 BRCA1 was cloned. The BRCA1 gene is large, and mutations are spread over the entire gene. There is evidence of common origins for some of the mutations. Early detection of hereditary breast and ovarian cancer is problematic. There is no evidence that early diagnosis by population-based mammography improves survival in sporadic premenopausal breast cancer. Multimodal screening for ovarian cancer has not been adequately assessed. Moreover, there is little evidence that such procedures are more likely to be effective in high-risk groups. Women who may gain initial benefit from the cloning of BRCA1 are from BRCA1-linked families who have living affected relatives. Over the next few years, it is likely that predictive testing for hereditary breast and ovarian cancer will become a routine clinical service in large centres.

Breast Neoplasms↗
PubMed2004

Minority recruitment in hereditary breast cancer research.

Although recruitment of ethnic and racial minorities in medical research has been evaluated in several studies, much less is known about the methods used to recruit these populations to participate in cancer genetics research. This report reviews the resources that have been used to identify and recruit ethnic and racial minorities to participate in hereditary breast cancer research. Overall, hospital-based resources were used most often to identify potential subjects, and active recruitment methods were used most frequently to enroll eligible subjects. This review suggests that there appears to be a finite number of resources and strategies to identify and recruit potential subjects to participate in cancer genetics research; however, options for improving awareness about cancer genetics research among ethnic and racial minorities have not been extensively evaluated. To study ethnic and racial minority participation in cancer genetics research, stronger evaluation components will need to be integrated into research methods. Both observational and experimental studies are needed to determine resources that are most effective for identifying potential subjects who are ethnic and racial minorities and to evaluate the effects of different recruitment strategies on enrollment decisions among these populations.

Breast Neoplasms↗
PubMed1996

Allele loss on chromosome arm 6q and fine mapping of the region at 6q27 in epithelial ovarian cancer.

Genetic changes have been shown to be important in determining the multistep progression of cancer. Allele loss studies and karyotypic analysis of epithelial ovarian tumours have indicated the presence of putative tumour suppressor genes on chromosomes 6, 11, 13, 17, 18, 22, and X. We have focused on chromosome arm 6q to identify the minimal region that may contain a putative tumour suppressor gene. Nineteen polymorphic microsatellite markers from 6q and one centromeric marker (D6S294) have been used to detect allele loss in 68 ovarian tumours (six benign, six borderline, and 56 with malignant histology). Allele loss was evaluated by separation of fluorescence labelled polymerase chain reaction-amplified products. Forty-six of fifty-six (82%) malignant tumours showed allele loss on 6q, whereas only four of 56 had lost all the markers tested. Forty-one of fifty-six (73%) malignant tumours showed allele loss at 6q26-27. The minimal region of allele loss was between markers D6S264 and D6S297 (3 cM), with maximal allele loss of 62% at D6S193 and 52% at D6S297. Three tumours showed loss of D6S193 only, while retaining flanking informative markers. Allele loss around 6q26-27 was observed in all histological types of epithelial ovarian cancer and did not correlate with any clinical factors. In addition, there was allele loss at ESR (56%) and D6S286 (47%), though a minimal region was not defined. Allele loss at 6q12-25 correlated significantly with endometrioid and mucinous ovarian malignant tumours (P = 0.01). The physical mapping of the region between D6S297 and D6S264 will allow the eventual identification of the putative tumour suppressor gene.

Adult↗
PubMed2006

Long contiguous stretches of homozygosity in the human genome.

Single nucleotide polymorphisms (SNPs) are the most common sequence variation in the human genome; they have been successfully used in mapping disease genes and more recently in studying population genetics and cancer genetics. In a population-based association study using high-density oligonucleotide arrays for whole-genome SNP genotyping, we discovered that in the genomes of unrelated Han Chinese, 34 out of 515 (6.6%) individuals contained long contiguous stretches of homozygosity (LCSHs), ranging in the size from 2.94 to 26.27 Mbp (10.22+/-5.95 Mbp). Four out of four (100%) Taiwan aborigines also demonstrated this genetic characteristic. The number of LCSH regions increased markedly in the offspring of consanguineous marriages. LCSH was also detected in Caucasian samples (11/42; 26.2%) and African American samples (2/42; 4.76%). A total of 26 LCSH regions were recurrently detected among Han Chinese, Taiwan aborigines, and Caucasians. DNA copy number determination by hybridization intensity analysis and real-time quantitative PCR (qPCR) excluded deletion as the cause of LCSH. Our results suggest that LCSHs are common in the human genome of the outbred population and this genetic characteristic could have a significant impact on population genetics and disease gene studies.

Black or African American↗
PubMed1993

p53 mutation in gastric cancer: a genetic model for carcinogenesis is common to gastric and colorectal cancer.

Mutation of the p53 tumour-suppressor gene in exons 5 through 8 was examined in 118 cases of gastric cancer (59 early gastric cancers and 59 advanced gastric cancers) using PCR-SSCP (polymerase-chain-reaction-single-strand-conformation polymorphism) analysis and direct sequencing. In early gastric cancer, mutations were found in 15 of 41 (37%) cases of the cohesive type, i.e., papillary adenocarcinoma, well to moderately differentiated tubular adenocarcinoma, and poorly differentiated adenocarcinoma with solid nests or focal tubular structures, but were not detected in 18 cases of the non-cohesive type, i.e., signet-ring-cell carcinoma and poorly differentiated adenocarcinoma growing in a scattered manner. In advanced gastric cancer, 25 of 59 (42%) cases of the cohesive type had p53 mutation. No significant association was found between p53 mutation and other histopathological parameters such as macroscopic classification, lymph-node involvement and depth of tumour invasion. Fifteen of 25 (60%) mutations in the advanced gastric-cancer group were accompanied by allele loss at the p53 gene locus. Eighty-three percent of mutations in early gastric cancer and 52% of mutations in advanced gastric cancer showed G:C-to-A:T transition, almost exclusively at CpG dinucleotide mutational hot spots, indicating that the spectrum of p53 mutation was similar to that of colorectal cancer. These data suggest that the p53 mutation occurs selectively in gastric cancer of the cohesive type from the intramucosal cancer stage.

Adenocarcinoma↗
PubMed1999

Clinical implications of p53 mutations.

The ultimate goal of basic cancer research is to provide a theoretical foundation for rational approaches to improve cancer therapy. Our extensive insight into the biology of the p53 tumour suppressor and the clinical behaviour of tumours harbouring p53 mutations indicates that information concerning p53 will be useful in diagnosis and prognosis, and may ultimately produce new therapeutic strategies. At the same time, efforts to understand the clinical implications of p53 mutations have revealed conceptual and technical limitations in translating basic biology to the clinic. The lessons learned from p53 may lay the groundwork for future efforts to synthesize cancer gene function, cancer genetics and cancer therapy.

Antineoplastic Agents↗
PubMed1995

What does it mean to be a cancer gene carrier? Problems in establishing causality from the molecular genetics of cancer.

This article addresses the following question: What does it mean to be a cancer gene carrier? The existence of families prone to cancer has prompted an intense search for predisposing heritable gene mutations. Genes that impart susceptibility to colorectal, breast, and ovarian cancers have been recently identified. It is doubtful, however, that the action of a single mutant gene totally accounts for the development of malignant disease. The mutant gene likely causes cancer in these family members only in conjunction with other genes, environmental factors, or both. Furthermore, although an individual carrier of a mutant gene within a cancer-prone family has an increased risk of malignancy, nutritional, pharmacologic, or other interventions may still confer protection. Extrapolations from cancer-prone families to the general population are even more problematic. The excess risk of malignancy among carriers of mutant genes who are not members of cancer-prone families is unknown. Large-scale epidemiologic studies are needed to determine the magnitude (or even the existence) of such excess risk.

Environmental Exposure↗
PubMed1994

Mutation of the p53 gene in gallbladder cancer.

Genetic alteration of the p53 gene was examined in tissue specimens of primary gallbladder cancer (GBC) using PCR-single strand conformation polymorphism (SSCP) and direct sequencing analyses. The p53 gene mutation was detected in five of the 16 GBC cases examined (31%). All five cases showed single point mutations; four were mutations resulting in amino acid substitution and the other was one base-pair deletion. Of the five mutations detected, four occurred at evolutionarily conserved regions and the remaining one at a well conserved region among species. Our result is similar to those of previous reports for various human cancers in mutation scattering over four of the five conserved domains.

Adult↗
PubMed2002

Impact of genetic counseling and testing on colorectal cancer screening behavior.

One goal of cancer genetic counseling is to improve early detection and prevention of cancers by identifying individuals at risk and providing screening recommendations. This study determined the impact of genetic counseling and testing on patient's post-genetic risk assessment colorectal cancer screening behaviors. Follow-up data from patients seen August, 1996, through May, 1998, at the Johns Hopkins Cancer Risk Assessment Clinic were analyzed. Eligible patients included those without cancer who were due for a colon examination by the time of follow-up, based on recommendations given during genetic risk assessment (GRA). We analyzed the role of gender, age, time since GRA, prior screening, genetic testing decision, mutation status, and post-GRA screening. Of 65 patients evaluated, 50 (76.9%) had undergone at least one endoscopic colon exam prior to visiting the Cancer Risk Assessment Clinic. At the time of GRA, 37 of 65 (56.9%) were overdue for a colon exam and at the time of follow-up, 15/65 (23.1%) were past due (p < 0.001). Patients with mutation-positive genetic tests were more likely to adhere to screening guidelines than those with negative gene tests (100% vs. 40.5%, p = 0.05). Genetic counseling and testing increases overall patient adherence with recommended colon screening, especially for those with positive genetic test results. However, patients with negative results may receive false reassurance about cancer risks and fail to follow recommended screening. Emphasis should be placed on the importance of screening even when genetic test results are negative.

Colorectal Neoplasms↗
PubMed1995

Detection of eight BRCA1 mutations in 10 breast/ovarian cancer families, including 1 family with male breast cancer.

Genetic epidemiological evidence suggests that mutations in BRCA1 may be responsible for approximately one half of early onset familial breast cancer and the majority of familial breast/ovarian cancer. The recent cloning of BRCA1 allows for the direct detection of mutations, but the feasibility of presymptomatic screening for cancer susceptibility is unknown. We analyzed genomic DNA from one affected individual from each of 24 families with at least three cases of ovarian or breast cancer, using SSCP assays. Variant SSCP bands were subcloned and sequenced. Allele-specific oligonucleotide hybridization was used to verify sequence changes and to screen DNA from control individuals. Six frameshift and two missense mutations were detected in 10 different families. A frameshift mutation was detected in a male proband affected with both breast and prostate cancer. A 40-bp deletion was detected in a patient who developed intra-abdominal carcinomatosis 1 year after prophylactic oophorectomy. Mutations were detected throughout the gene, and only one was detected in more than a single family. These results provide further evidence that inherited breast and ovarian cancer can occur as a consequence of a wide array of BRCA1 mutations. These results suggests that development of a screening test for BRCA1 mutations will be technically challenging. The finding of a mutation in a family with male breast cancer, not previously thought to be related to BRCA1, also illustrates the potential difficulties of genetic counseling for individuals known to carry mutations.

BRCA1 Protein↗
PubMed1996

Potential role of DNA polymerase beta in gene therapy against cancer: a case for colorectal cancer.

Genetic instability characterized by the accumulation of mutations of tumor suppressor genes and oncogenes appears to be associated with carcinogenesis in colorectal and other cancers. Mutations of DNA polymerase beta (pol beta) and related chromosomal alterations appear to be consistent with the causal role of a "mutator phenotype' in carcinogenesis. However, homozygous knockout pol beta mutations appear to interfere with embryogenesis. Increased pol beta activity (i.e. relative to pol alpha activity) has been associated with cell cycle arrest. The related aphidicolin-resistant DNA replication has been observed primarily in differentiating cells, including the mammalian blastocyst, adrenal cortex, thyroid, anterior pituitary, and the mechanism of endoreduplication (amitotic over-replication of DNA) can be traced to lower eukaryotes. This increased activity in relation to terminal commitment is inconsistent with a simple "DNA repair' view of pol beta. It is therefore proposed that pol beta may play a more fundamental role in cellular differentiation through involvement in a putative subgenomic DNA replication-based model of terminal gene expression. Thus genetic instability, loss of differentiation, and carcinogenesis may result from aberration(s) or "derailment' of such replication-based mechanism of terminal gene expression. It is suggested to examine the relationship of DNA pol beta to genomic instability and carcinogenesis using genetic analyses and antisense technology with possible applications for gene therapy against colorectal cancer.

Animals↗