Stalking the start of colon cancer

Association between the CYP1A1 gene polymorphism and susceptibility to emphysema and lung cancer

Aim-To investigate cytochrome P4501A1 (CYP1A1) polymorphism and susceptibility to emphysema and lung cancer.Methods-A novel polymerase chain reaction (PCR) for genotyping the CYP1A1 polymorphism, corresponding to putative low or high enzyme activity, was developed to genotype lung cancer resection samples which had been assessed macroscopically for the presence of centriacinar and panacinar emphysema. Samples were collected and genotyped from a group of patients with chronic obstructive airways disease. A control group of anonymous blood donations was genotyped to determine the basal levels of the polymorphism in the Scottish population.Results-The high activity allele of the CYP1A1 gene is associated with susceptibility to centriacinar emphysema and lung cancer but not panacinar emphysema. CYP1A1 polymorphism is not linked to lung cancer in the absence of emphysema, nor to chronic obstructive airways disease which is the clinical manifestation of emphysema, particularly of the panacinar type.Conclusions-Susceptibility to emphysema and lung cancer is associated with polymorphism of the P4501A1 gene. A trend towards damage of centriacinar pattern has been detected, which supports the theory that centriacinar emphysema results from local, direct damage to the respiratory bronchioles from exposure to cigarette smoke.

Effects of high ELF magnetic fields on enzyme-catalyzed DNA and RNA synthesis in vitro and on a cell-free DNA mismatch repair

Environmental electromagnetic fields have been implicated in human cancers. We examined whether high extremely low frequency (ELF) AC magnetic fields could affect DNA synthesis, transcription or repair, using in vitro model systems with defined sequences. The rate and fidelity of DNA polymerase catalyzed DNA synthesis, as well as of RNA polymerase catalyzed RNA synthesis, were not statistically significantly affected by 60 Hz 0.25-0.5 Tesla magnetic fields. The efficiency of mutS dependent mismatch repair with human cell extracts was also not affected by the magnetic field exposure. The results suggest that the core processes related to the transmission of genetic information are stable under high ELF magnetic fields.

Do MSH6 mutations contribute to double primary cancers of the colorectum and endometrium?

Mismatch repair (MMR) gene mutations cause hereditary nonpolyposis colorectal cancer (HNPCC), a common form of familial colorectal cancer. Among MMR genes, germline MSH6 mutations are often observed in HNPCC-like families with an increased frequency of endometrial cancer. We have previously shown that a proportion of women affected with double primary cancers of the colorectum and endometrium carry germline MSH2 or MLH1 mutations and, thus, belong to HNPCC families. In this study, we have investigated the specific contribution of MSH6 defects to such double primary patients. By sequence analysis of the entire coding region of MSH6, three putative missense mutations were identified in patients with atypical family histories that do not meet HNPCC criteria. Moreover, one of these mutations, a novel substitution Arg901 His, was found in a patient previously shown to carry a truncating germline MLH1 mutation. Thus, MSH6 mutations are likely to contribute to the etiology of double primary cancers of the colorectum and endometrium.

Molecular-pathological diagnosis of gastrointestinal tissues and its contribution to cancer histopathology

Multiple genetic and epigenetic alterations of cancer-related genes and molecules are involved in the course of the development and progression of gastrointestinal cancers. These include telomerase activation, genetic instability, and abnormalities of oncogenes, tumor suppressor genes, cell cycle regulators, cell adhesion molecules and DNA repair genes. By analyzing these alterations in pathology specimens, we can improve differential diagnosis of cancer, obtain information of grade of malignancy, and identify patients at high risk for developing multiple primary cancers. Since 1993, a system of molecular-pathological diagnosis was established, and has been performed as a routine service in collaboration with Hiroshima City Medical Association Clinical Laboratory. More than 10 000 cases of gastrointestinal biopsy and surgery have been analyzed, and additional information of differential diagnosis, biological malignancy and tumor multiplicity could be obtained. Molecular-pathological diagnosis may provide a new approach to cancer diagnosis and novel therapeutics for the 21st century. Furthermore, the analysis of the genetic and epigenetic abnormalities in clinical materials may clarify the molecular mechanism of carcinogenesis and comparative morphological changes. From the analyses of p27KIP1 and telomerase in gastrointestinal adenomas, we have learned that morphological abnormality of the nucleus is an indicator for cells with immortality and malignant potential that must participate in super-early diagnosis (detection of true precancerous lesions) of gastrointestinal cancer. Molecular-pathological diagnosis thus contributes to detailed understanding of cancer histopathology and improves the histopathological diagnosis.

Li-Fraumeni syndrome and the role of the p53 tumor suppressor gene in cancer susceptibility

Mutation of the tumor suppressor gene p53 is a molecular genetic event frequently observed in human cancer, and inactivating missense mutations usually are accompanied by the resultant overexpression of mutant p53 protein. In gynecologic cancers, p53 is also often altered; the frequency varies depending on types of cancers and where they develop. Further, human papillomavirus oncoproteins that inactivate p53 and Rb proteins play important roles in the development of several gynecologic cancers. Individuals who are heterozygous for germline mutations of the p53 gene are strongly predisposed to a variety of cancers. The identification of these individuals may have profound value in the future when therapies or chemopreventive agents specific for the p53 alteration are available. The role of p53 tumor suppressor gene in gynecologic cancers and heritable cancer susceptibility syndromes including Li-Fraumeni and Lynch II syndromes is an active and important area of study.

Isolation and characterization of the human mismatch repair gene hMSH2 promoter region

Hereditary nonpolyposis colorectal cancer (HN-PCC) is one of man's commonest hereditary diseases. Several studies have identified four responsible genes that are involved in a process known as DNA mismatch repair; hMSH2 is the most important of these four genes. In addition to mutational analysis of these genes, investigations of transcriptional regulatory mechanisms are important. Therefore, our purpose has been to isolate the hMSH2 promoter region. Using direct sequencing of P1 recombinant DNA we have characterized 1100 bp of the hMSH2 promoter.

Microsatellite instability in human colonic cancer is not a useful clinical indicator of familial colorectal cancer

BACKGROUND & AIMS

Microsatellite instability is a property of most tumors occurring in the context of hereditary nonpolyposis colon cancer. Instability also occurs in 10%-15% of apparently sporadic colorectal cancers, and it has been hypothesized that this instability may indicate a genetic predisposition to colonic cancer. This study evaluated whether there is a clinically useful association between colon cancer instability and a family history of cancer.

METHODS

Colon cancer cases (n = 188) from a population-based study were evaluated for microsatellite instability with 10 polymerase chain reaction primer sets. Instability results were compared with family history and other clinical and biological characteristics.

RESULTS

Microsatellite instability was found in 16.5% of tumors. It was predominantly a feature of right-sided tumors (P = 0.003) and was associated with the youngest and oldest ages at diagnosis (P = 0.01). Instability was not associated with family history of cancer, sex of the individual, or the glutathione-S-transferase mu 1 null genotype.

CONCLUSIONS

Although some very small, and as yet undefined, proportion of colon cancer may be caused by inherited mutations leading to microsatellite instability, tumoral instability by itself is not a marker for familiality and should not be considered as evidence for an inherited syndrome.

Molecular basis of endometrial cancer

BACKGROUND

Most human cancers are thought to arise from alterations in oncogenes and tumor suppressor genes.

METHODS

Molecular techniques have been used to identify specific genetic alterations in endometrial cancers.

RESULTS

Overexpression of the HER-2/neu oncogene occurs in 10% of endometrial cancers and correlates with poor survival. Alterations in other receptor tyrosine kinases (c-fms and epidermal growth factor receptor) also occur in some cases. The c-myc oncogene, which encodes a nuclear transcription factor, also may be overexpressed in some invasive cancers. Mutations in the K-ras oncogene occur in 10% and in 20-30% of American and Japanese endometrial cancers, respectively. K-ras mutations also have been observed in endometrial hyperplasias, and this may represent an early event in the development of some cancers. Mutation of the p53 tumor suppressor gene, with resultant overexpression of mutant p53 protein, occurs in 20% of endometrial adenocarcinomas. Overexpression of p53 is associated with advanced stage and poor survival. Because p53 mutations do not occur frequently in endometrial hyperplasias, this may be a relatively late event in endometrial carcinogenesis. Recent studies have shown that mutations occur in microsatellite sequences in some endometrial cancers. Because microsatellite instability in hereditary nonpolyposis colon cancer has been found to be caused by mutations in DNA repair genes, similar mutations are being sought in endometrial cancers.

CONCLUSIONS

Although several molecular alterations have been identified, the molecular pathogenesis of endometrial cancer remains poorly understood.

DNA mismatch repair and cancer

The genetic basis of cancer involves certain classes of genes, particularly oncogenes, tumor-suppressor genes, and DNA mismatch repair genes. Originally identified in bacteria and yeast, the human homologues of DNA mismatch repair genes have been implicated in the pathogenesis of the hereditary nonpolyposis colorectal cancer syndromes, as well as a variety of different sporadic cancers. An appreciation of their role in cancer is predicated on an understanding of their function in the processes of DNA repair. This article reviews the recent developments and advances in the biology of the human DNA mismatch repair genes and their involvement in the pathogenesis of cancer.

Lung pathology: the molecular genetics of non-small cell lung cancer

In Australia, lung cancer is the most common malignancy in males and the largest cause of cancer deaths. Conventional management has not had a dramatic impact on the mortality rates from lung cancer, which has a case-fatality rate of over 90%. Recent developments in molecular and cellular biology have however, contributed to our knowledge of lung tumorigenesis, which will hopefully translate into clinical benefit for our patients. Many molecular abnormalities are common to both non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) but there are differences between these histological types and even within the NSCLC subtypes. This review concentrates on NSCLC, which accounts for up to 85% of Australian lung cancers.

Recombination, mutation and the origin of species

A major barrier to recombination between bacterial species lies in the mismatch repair system, a complex of proteins that has evolved to proof-read freshly replicated DNA. It now appears that a second system, involving an inducible DNA recombination, repair and mutagenesis pathway, also regulates interspecies recombination, but in a positive way, being required for recombination between Escherichia coli and Salmonella typhimurium. Thus the rate at which newly emerging species of bacteria diverge can be seen as a balance between a permissive state associated with inducible repair and recombination, and the proof-reading of intermediates in the recombination pathway by the mismatch correction system.

Familial myelodysplastic syndrome with onset late in life

A family is described in which three, and possibly four members, namely, the propositus, two paternal uncles, and possibly his paternal grandfather, developed a myelodysplastic syndrome (MDS) after the age of 60 years. This late onset resembles sporadic cases which are commoner in older age, rather than the previously reported familial cases most of whom have been children or young adults. The three affected members had megaloblastoid bone marrows with an increased proportion of bone marrow blasts and developed progressive bone marrow failure without leukemic transformation. The propositus showed a dramatic but temporary response to GM-CSF therapy but eventually became unresponsive with a marked increase in bone marrow reticulin and reduction in hemopoietic elements. Affected members had no recognisable bone marrow cytogenetic abnormality but the pattern of inheritance and similarity in clinical features suggest an inherited genetic defect which predisposes to the development of MDS.

Patenting genes. J. Craig Venter and the Human Genome Project

He often begins to answer before you have finished asking your question, but his replies are to the point. He speaks with emotion about the people he hopes to help, particularly children with fatal genetic diseases. 'I prefer to do something: the outcome of doing nothing is perfectly clear', he says. He began sequencing human genes while others were discussing how and when to do so. His methods have been called inelegant, redundant, wasteful, and too 'industrial'. Will his method fail to detect some infrequently transcribed genes? That's all right with him. He is not concerned with finding all the human genes, but rather with the fastest possible route to a useful catalog of most human genes.

Genetic alterations in human gastrointestinal cancers. The application to molecular diagnosis

Gastrointestinal cancers involve genetic alterations in multiple oncogenes, multiple tumor suppressor genes, and multiple DNA repair genes. However, common and different genetic changes are observed in esophageal, gastric, and colorectal carcinomas, respectively. Inactivation of the p53 gene and expression of CD44 abnormal transcripts are common events that serve as a powerful tool for cancer diagnosis. Gene amplification of cyclin D is found preferentially in esophageal cancer, whereas gene amplification of cyclin E and c-met is frequently associated with gastric cancer. Mutations of the cyclin-dependent kinase inhibitor genes also occur in esophageal and gastric cancers. However, the scenario of multiple gene changes differs depending on the two histologic types of gastric cancer, because they may have different genetic pathways. Interestingly, the frequency of genetic instability is also quite different between the two types of gastric cancer. A new strategy of molecular diagnosis for gastrointestinal cancers, which started as routine work at Hiroshima City Medical Association Clinical Laboratory last August, may provide a new approach to cancer diagnosis for the next decade.

Interspecies gene exchange in bacteria: the role of SOS and mismatch repair systems in evolution of species

Analysis of interspecies matings between S. typhimurium and E. coli indicates that the genetic barrier that separates these (and perhaps many other) related species is primarily recombinational. The structural component of this barrier is genomic sequence divergence. The mismatch repair enzymes act as potent inhibitors of interspecies recombination, whereas the SOS system acts as an inducible positive regulator. Interspecies mating triggers a RecBC-dependent SOS response in female bacteria that increases recombination mainly through overproduction of the RecA protein. Mismatch repair acts to reduce the mutation rate and recombination between similar sequences, whereas SOS acts to increase both. These opposing activities allow mismatch repair and SOS systems to determine both the rate of accumulation of sequence divergence and the extent of genetic isolation, which are the key components of the speciation process.

Unstable triplet repeat diseases

Seven inherited human disorders are now associated with the intragenic expansion of triplet repeat DNA sequences. These repeats demonstrate extreme instability in both germline and somatic tissue, accounting for the unusual genetic inheritance patterns and symptom variability associated with these diseases.

Biomarkers in the endometrium

A number of oncogenes and tumor suppressor genes that may serves as surrogate biomarkers of transformation are altered during the process of endometrial carcinogenesis. Overexpression of HER-2/neu occurs in 10% of endometrial adenocarcinomas and correlates with intraperitoneal spread of disease and poor survival. The c-myc oncogene is amplified in 10% of cases. Point mutations in codon 12 of the K-ras oncogene have been reported to occur in 10-20% of endometrial cancers. K-ras mutations also have been noted in some endometrial hyperplasias, which may represent an early event in the development of some endometrial cancers. Mutation of the p53 tumor suppressor gene, with resultant overexpression of mutant p53 protein, occurs in 20% of endometrial adenocarcinomas. Overexpression of p53 is associated with advanced stage and poor survival. Because p53 mutations have not been observed in endometrial hyperplasias, this is thought to be a relatively late event in endometrial carcinogenesis. Microsatellite instability has also been noted in approximately 15% of sporadic endometrial cancers, but mutations in DNA repair genes have not yet been reported. Chemoprevention trials in endometrial cancer may be feasible due to the existence of a premalignant lesion and surrogate biomarkers.

Diagnosis and the new genetics

The rapid pace of gene discovery has led to new opportunities for clinical diagnosis using molecular genetic technologies. Recent achievements include the culmination of the 10-year search for the Huntington's disease gene, the identification of predisposing genes for certain familial colon cancers, and the characterization of potential genetic risk indicators for Alzheimer's disease, hypertension, and coronary heart disease. These advances, coupled with the previous discoveries of important disease genes (e.g. those for cystic fibrosis, Duchenne muscular dystrophy, and fragile X syndrome) have quickly expanded the capacity of genetic analysis, allowing the design of enhanced and novel approaches for diagnostic testing. The transfer of molecular technology to the area of clinical genetic analysis, although associated with many potential benefits, has raised some concern regarding the possible misuse of genetic tests and information, particularly with regard to presymptomatic diagnosis of disease and population screening.

Pathogenesis of ovarian cancers

OBJECTIVE

To review our current understanding of the molecular genetic events involved in the development of epithelial ovarian cancers.

METHODS

Molecular biologic techniques have been used to examine the role of growth-stimulatory genes (oncogenes) and -inhibitory genes (tumor suppressors) in ovarian cancer.

RESULTS

A number of different peptide growth factors and their receptors are expressed by normal and malignant ovarian epithelial cells. However, the role, if any, of growth factors in ovarian carcinogenesis or maintenance of the transformed phenotype remains unknown. Amplification and overexpression of the HER-2/neu and c-myc oncogenes occur in a significant fraction of epithelial ovarian cancers (20-30%). Overexpression of HER-2/neu has correlated with poor survival in some studies, whereas c-myc amplification is more common in serous cancers. Mutation of the K-ras oncogene frequently occurs in borderline ovarian tumors, but is less common in invasive epithelial ovarian cancers. Mutation of the p53 tumor suppressor gene occurs in approximately half of advanced (stage III/IV) ovarian cancers and in 15% of early (stage IA/IB) cases. Most recently, preliminary studies have focused on the role of other tumor suppressor genes, cyclins, WAF1, and DNA mismatch repair genes.

CONCLUSIONS

An understanding of the molecular events involved in the pathogenesis of epithelial ovarian cancer is beginning to evolve. Improvements in early diagnosis, treatment, and prevention of this deadly disease are dependent on further progress in this area.