Recessive mutations in the causation of human cancer

Article Abstract:

The General Motors Cancer Research Foundation awarded the 1990 Charles S. Mott Prize to Webster K. Cavenee for his research on the role of mutations in the causation of cancer. Genetic damage has now been implicated as a contributing factor in a wide range of different cancers. Dr. Cavenee focused his research on a childhood cancer of the retina, retinoblastoma. Retinoblastoma occurs both as a familial disease and also sporadically; about 1 in 10,000 children are affected. Investigation of the chromosomes of patients with retinoblastoma has revealed that many patients have a large piece of DNA missing from chromosome 13; examining enough such patients has revealed that a particular region, located at 13q14 on the long arm of chromosome 13, is gone in all the patients so affected. In general, however, such a deletion should not cause cancer. Since virtually all genes are present in two copies, the other, normal gene, should be able to take up the slack of the retinoblastoma gene with the deletion or other mutation. This led to the hypothesis that the development of retinoblastoma actually involves two mutations. The first, the deletion, is inherited from one parent. The second mutation, in the corresponding gene on the other chromosome, occurs randomly in a retinal cell during embryonic development. Lacking a properly functioning retinoblastoma protein, the cell becomes malignant. This model also provides an explanation for the sporadic form of the disease. In some unlucky individuals, two normal genes are inherited from the parents, but first one and then the other suffer mutations in embryonic development. Research into other forms of cancer is beginning to reveal that the road to cancer is not a single wrong mutation resulting in malignancy, but rather an accumulation of many genetic wrong turns which ultimately result in cancerous growth. (Consumer Summary produced by Reliance Medical Information, Inc.)

Research, Mutation (Biology), Mutation, Biochemical genetics, Genetic disorders, Retinoblastoma, Medical genetics

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Endometrial carcinoma in the cancer family syndrome

Article Abstract:

Hereditary nonpolyposis colorectal carcinoma (HNPCC) is a form of colorectal cancer which occurs in family clusters; it is sometimes called the 'cancer family syndrome'. However, medical practitioners often fail to appreciate that endometrial cancer, cancer of the lining of the uterus, often occurs in these same family clusters. The focus of attention on the colorectal cancers has obscured the fact that cancer of the uterine endometrium is the second most common form of cancer in these 'cancer families'. A study was conducted to tabulate the important features of 26 cases of endometrial cancer occurring in 19 cancer families. The average age of onset for these patients was 48, which is 14 years younger than the average age for endometrial cancer. In the majority of cases, excessive or irregular bleeding was the first indication that a cancer might be present. Fourteen of the 26 patients had other cancers in addition to the endometrial cancer, and six of these 14 patients had more than one other cancer. Colorectal cancers accounted for half of all the additional cancers, but cancers of the ovary, stomach, bladder, lung, pancreas, and breast also occurred. The five-year survival rate for the patients in the present study was 73 percent. For purposes of comparison, the five-year survival of a set of 442 women with endometrial cancer without familial cancer histories was 68 percent. In the present series of 19 cancer families, the recognition familial cancer was delayed in 14 families. The reason for this delay was the failure to consider endometrial cancer as one of the possible indications of cancer family syndrome. (Consumer Summary produced by Reliance Medical Information, Inc.)

Endometrial cancer

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Results of a screening program for C-cell disease (medullary thyroid cancer and C-cell hyperplasia)

Article Abstract:

Multiple endocrine neoplasia types IIa and IIb involve a familial predisposition to several endocrine tumors, including pheochromocytoma and parathyroid hyperplasia. Medullary thyroid cancer (MTC), however, is the most common neoplasm resulting from this disorder. Clinicians have come to recognize that when patients with MTC are identified, family members and relatives should be screened for MTC or C-cell hyperplasia, which may be a premalignant form of MTC. Even among patients with apparently sporadic, as opposed to familial, MTC, 10 to 20 percent will have relatives with MTC or C-cell disease. When the levels of calcitonin hormone were measured after stimulation with calcium in members of the families of 12 patients with apparently sporadic MTC, 25 percent of the patients had affected relatives. Since C-cell hyperplasia may progress to MTC, early surgical treatment is believed to have great value. However, it should be noted that in some patients the elevated levels of calcitonin may resolve spontaneously, suggesting that C-cell disease may in some cases be a reversible condition. (Consumer Summary produced by Reliance Medical Information, Inc.)

Thyroid cancer

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