Incidence of cancer in 161 families affected by ataxia-telangiectasia

Article Abstract:

Ataxia-telangiectasia is a genetic disorder, inherited as a recessive trait. Patients who are homozygous, that is, who carry two copies of the gene, develop ataxia starting in childhood. This defect in coordinated movement progresses to complete disability by 10 years. Patients with this disorder also develop telangiectasia, or swelling of tiny blood vessels. These telangiectatic lesions generally develop at about three or four years of age. Retrospective studies have indicated that homozygotes are about 100 times more likely to develop cancer than the general population. Retrospective family studies have also suggested that heterozygotes, who carry one copy of the gene, and therefore do not develop the syndrome, also suffer increased risk of cancer. Among heterozygotes, however, the risk of cancer is much less, perhaps two to six times greater than the general population. Retrospective studies may be tainted, however. Bias may result from the increased likelihood that families with several cancer patients may be more likely to come to the attention of medical researchers. A prospective study was therefore conducted on 161 families with ataxia-telangiectasia. A total of 1,599 blood relatives of patients with ataxia-telangiectasia were followed for periods averaging 6.4 years; 821 spouses served as control subjects. Ninety-one cancers developed among the blood relatives; 19 were identified among the spouses. This confirms the increased risk among possible heterozygotes. A total of 294 relatives carry the gene with certainty, due to their relationship with an ataxia-telangiectasia patient. When only these people were considered, the observed increased cancer risk was greater. The cancer risk for male heterozygotes is increased by 3.8 times, that for women 3.5 times. The risk of breast cancer among female heterozygotes is increased 5.1 times. A case-control evaluation demonstrated that the women with breast cancer were more likely to have been exposed to selected sources of radiation, such as X-rays. Heterozygotes carrying the ataxia-telangiectasia gene appear to be especially susceptible to the cancer-causing effects of radiation. Low levels of radiation, such as those received during mammography, are safe for most people but may be dangerous for women carrying the ataxia-telangiectasia gene. The authors suggest that women from affected families might consider alternatives to mammography and other routine X-rays. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Research, Risk factors, Breast cancer, Genetic disorders, Ataxia telangiectasia

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K-ras oncogene activation as a prognostic marker in adenocarcinoma of the lung

Article Abstract:

Oncogenes are genes in human cells which, when activated, may be related to the development of cancer. Understanding of the malignant transformation of cells has been greatly advanced in recent years by the recognition that the cancer-causing genes found in some viruses have counterparts in normal cells. A number of such oncogenes have been described, and it is believed that at least in some cases the transformation of a normal cell into a malignant cell results from a mutation in one of these oncogenes. One such family of oncogenes is the ras gene. There are three main subgroups, H-ras, K-ras, and N-ras, all of which encode a protein with a molecular weight of 21 kilodaltons. Tissues removed from 69 patients with adenocarcinoma of the lung were tested for the activation of one site in the ras oncogene by a specific mutation at one location (codon 12). A mutation at this site has been previously found in approximately one third of lung adenocarcinomas. By amplifying the quantity of DNA available, specific DNA segments that included the K-ras oncogene site could be measured from 69 adenocarcinoma patients. Nineteen of these patients were found to have tumors that had a single mutation in the K-ras oncogene. The presence of this mutation was a highly unfavorable sign. Twelve of the 19 died during the follow-up period, compared with 16 out of 50 patients who did not have a mutation of the K-ras oncogene. Patients without the mutation also had a longer period when they were free of disease following their original surgery. The results show that the presence of a mutation to the K-ras oncogene, despite radical surgery and only small original tumors, is associated with a very poor prognosis. (Consumer Summary produced by Reliance Medical Information, Inc.)

Abnormalities, Causes of, Physiological aspects, Prognosis, DNA damage, Oncogenes, Ras genes, Adenocarcinoma

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Gene transfer into humans: a first step

Article Abstract:

An article in the August 30, 1990 issue of The New England Journal of Medicine reports the first transfer of human cells which have had a region of foreign genetic material spliced into the chromosomes. In this case, modified human cells were re-injected into the patient from whom they were taken. Tumor-infiltrating lymphocytes (TIL), white blood cells, were altered (by retroviral infection, transduction) to include a gene that rendered the altered cells more resistant to an antibiotic. This property tagged the cells and allowed researchers to document that the TIL cells remained in the patient for an extended period of time (up to two months in two patients). There were no ill effects from the introduction of genetically manipulated cells back into the patients. These studies appear to indicate that the preparatory method that uses retrovirus to add genetic material into the human chromosome is both safe and efficient. This step may eventually lead to the immunotherapy of a great number of human inherited disorders. The opportunity to correct defects in the production of a particular biochemical molecule because of a missing or damaged gene may be near. It is especially hoped that the data obtained from this and similar future experiments could lead to improved therapies for cancer. It remains important for national and institutional regulatory authorities to ensure that this new line of research continues in a safe manner. (Consumer Summary produced by Reliance Medical Information, Inc.)

Innovations, Genetic engineering, Immunotherapy, editorial

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