The BRCA1 and BRCA2 breast cancer genes

This review discusses the need for sleep, effects of sleep deprivation on behaviour and performance in the military, and sleep management recommendations to optimise combat effectiveness. Most people, regardless of sex or race, prefer 7 to 8 hours of sleep each night. Sleeping during the day is less recuperative. Continuous sleep is more effective than multiple short naps-even when the total hours for naps is more. Ten to 20 minute naps are useful when continuous sleep is not possible. Sleep inertia is the 5 to 30 minute period of sluggishness after awakening and important military tasks should be avoided. Previously, continuous work episodes (CWEs) duration was restricted by limited night vision, unreliable equipment and reduced endurance of military personnel. With improved technology, CWEs are now restricted primarily by endurance which is affected by sleep deprivation. This was one of the experiences noted in recent conflicts (e.g. Desert Storm) by personnel in the air force, army and navy. Since there will be changes in operational requirements, several work-rest-sleep plans must be prepared. Sleeping the preferred 7 to 8 hours per 24 hours the week before an operation may help prepare for optimal performance. Personnel should be familiarised with conditions under which they may sleep. During combat, sleep management should ideally avoid situations where all personnel are exhausted at the same time. As sleep debt accumulates, a person's mood, motivation, attention, alertness, short-term memory, ability to complete routines, task performance (errors of omission more than errors of commission) and physical performance will become more negatively affected. Counter measures must then be taken (e.g. time for sleep or naps, changing routines or rotating jobs). Drugs like caffeine and amphetamine can help personnel stay awake. However, they may also keep them awake when they need to sleep- and on awakening, they could suffer from "hang-overs" and are less efficient. Sleep lost need not be replaced hour-for-hour. Therefore, after operations, personnel need continuous sleep for only 10 to 12 hours as longer sleep increases sleep inertia and delays getting back to normal schedules.     

Mutations in BRCA1 and BRCA2 in breast cancer families: are there more breast cancer-susceptibility genes?

To estimate the proportion of breast cancer families due to BRCA1 or BRCA2, we performed mutation screening of the entire coding regions of both genes supplemented with linkage analysis of 31 families, 8 containing male breast cancers and 23 site-specific female breast cancer. A combination of protein-truncation test and SSCP or heteroduplex analyses was used for mutation screening complemented, where possible, by the analysis of expression level of BRCA1 and BRCA2 alleles. Six of the eight families with male breast cancer revealed frameshift mutations, two in BRCA1 and four in BRCA2. Although most families with female site-specific breast cancers were thought to be due to mutations in either BRCA1 or BRCA2, we identified only eight mutations in our series of 23 site-specific female breast cancer families (34%), four in BRCA1 and four in BRCA2. According to the posterior probabilities calculated for mutation-negative families, based on linkage data and mutation screening results, we would expect 8-10 site-specific female breast cancer families of our series to be due to neither BRCA1 nor BRCA2. Thus, our results suggest the existence of at least one more major breast cancer-susceptibility gene.     

Germline mutations of the BRCA1 and BRCA2 genes in a breast and ovarian cancer patient

Nitric oxide (NO) has been implicated as a modulator of the vascular effects of angiotensin II (ANG II) in the kidney. We used a NO-sensitive microelectrode to study the effect of ANG II on NO release, and to determine the effect of selective inhibition of the ANG II subtype I receptor (AT1) with losartan (LOS) and candesartan (CAN). NO release from isolated and perfused renal resistance arteries was measured with a porphyrin-electroplated, carbon fiber. The vessels were microdissected from isolated perfused rat kidneys and perfused at constant flow and pressure in vitro. The NO-electrode was placed inside the glass collection cannula to measure vessel effluent NO concentration. ANG II stimulated NO release in a dose-dependent fashion: 0.1 nM, 10 nM and 1000 nM ANG II increased NO-oxidation current by 85+/-18 pA (n = 11), 148+/-22 pA (n = 11), and 193+/-29 pA (n = 11), respectively. These currents correspond to changes in effluent NO concentration of 3.4+/-0.5 nM, 6.1+/-1.1 nM, and 8.2+/-1.3 nM, respectively. Neither LOS (1 muM) nor CAN (1 nM) significantly affected basal NO production, but both AT1-receptor blockers markedly blunted NO release in response to ANG II (10 nM): 77+/-6% inhibition with LOS (n = 8) and 63+/-9% with CAN (n = 8). These results are the first to demonstrate that ANG II stimulates NO release in isolated renal resistance arteries, and that ANG II-induced NO release is blunted by simultaneous AT1-receptor blockade. Our findings suggest that endothelium-dependent modulation of ANG II-induced vasoconstriction in renal resistance arteries is mediated, at least in part, by AT1-receptor-dependent NO release.     

Double heterozygosity for mutations in the BRCA1 and BRCA2 genes in a breast cancer patient

BACKGROUND: Germline mutations in the tumor suppressor genes BRCA1 and BRCA2 confer substantial increased lifetime risk for breast cancer, and in the case of BRCA1, for ovarian carcinoma as well. These two genes alone account for the vast majority of hereditary breast cancer families. Numerous mutations have been described in each gene, the majority of which are small insertions or deletions resulting in expression of a truncated protein. MATERIALS AND METHODS: Several common mutations can be detected using a polymerase chain reaction-mediated, site-directed mutagenesis assay, which transforms the amplicon derived from either the wild-type or mutant allele by adding or removing a restriction endonuclease site. We screened 49 putative sporadic breast tumors using this methodology, targeting four BRCA1 mutations (185delAG, 5382insC, R1443X, and E1250X) and a single BRCA2 mutation (6174delT). RESULTS: Using the polymerase chain reaction-mediated, site-directed mutagenesis assay, we identified two mutations, namely, a 185delAG mutation (BRCA1) and a 6174delT mutation (BRCA2). Interestingly, these two mutations were found in the same sample. None of the remaining 48 breast tumors showed evidence of these mutations. Allele-specific oligonucleotide probes were then employed in conjunction with the Universal GeneComb Test Kit, which confirmed the presence of mutations. CONCLUSIONS: Our data suggest that the common germline BRCA1 and BRCA2 mutations are infrequently encountered in sporadic breast cancers. The one case with dual BRCA1 and BRCA2 mutations suggests that this tumor may be hereditary in origin, despite the lack of a positive family history. Double heterozygosity for mutations in BRCA1 and BRCA2 may have increasingly significant implications with regard to predisposition to breast cancer.     

Effect of BRCA1 and BRCA2 on the association between breast cancer risk and family history

BACKGROUND: The discovery of BRCA1 and BRCA2 has led to a reassessment of the association between family history of breast/ovarian cancer and breast cancer risk after controlling for carrier status for mutations in the BRCA1 and BRCA2 genes. We examined whether family history of breast cancer remains a predictive risk factor for this disease after carrier status for BRCA1 and/or BRCA2 mutations is taken into consideration. METHODS: The data are from 4730 case subjects with breast cancer and 4688 control subjects enrolled in the Cancer and Steroid Hormone Study. The probability of being a BRCA1 and/or BRCA2 gene carrier was calculated for each woman. Among predicted noncarriers, logistic regression was used to assess the relationship (odds ratios and 95% confidence intervals [CIs]) between case or control status and family history of breast or ovarian cancer. Estimates of age-specific breast cancer risk are presented by predicted carrier status. RESULTS: Among predicted noncarriers, case subjects were 2.06 times (95% CI = 1.69-2.50) and 1.24 times (95% CI = 1.17-1.32) more likely to report a first-degree or second-degree family history of breast cancer, respectively, than were control subjects. Case subjects were 1.99 times (95% CI = 1.63-2.44), 1.66 times (95% CI = 1.18-2.38), and 2.23 times (95% CI = 0.21-24.65) more likely to report an affected mother, sister, or both, respectively, than were control subjects. A family history of ovarian cancer was not statistically significantly associated with breast cancer risk. Noncarriers were predicted to have a lifetime risk of 9% of developing breast cancer compared with a 63% risk for carriers. CONCLUSIONS: Among women with a moderate family history of breast cancer, i.e., predicted noncarriers of BRCA1 and/or BRCA2 mutations, family history remains a factor in predicting breast cancer risk. In families with breast and ovarian cancers, the aggregation of these two cancers appears to be explained by BRCA1/BRCA2 mutation-carrier probability.     

Differential contributions of BRCA1 and BRCA2 to early-onset breast cancer

BACKGROUND: Germ-line mutations in the BRCA1 and BRCA2 genes predispose women to breast cancer. BRCA1 mutations are found in approximately 12 percent of women with breast cancer of early onset, and the specific mutation causing a deletion of adenine and guanine (185delAG), which is present in 1 percent of the Ashkenazi Jewish population, contributes to 21 percent of breast cancers among young Jewish women. The contribution of BRCA2 mutations to breast cancer of early onset is unknown. METHODS: Lymphocyte specimens from 73 women with breast cancer diagnosed by the age of 32 were studied for heterozygous mutations of BRCA2 by a complementary-DNA-based protein-truncation assay, followed by automated nucleotide sequencing. In addition, specimens from 39 Jewish women with breast cancer diagnosed by the age of 40 were tested for specific mutations by an allele-specific polymerase chain reaction. RESULTS: Definite BRCA2 mutations were found in 2 of the 73 women with early-onset breast cancer (2.7 percent; 95 percent confidence interval, 0.4 to 9.6 percent), suggesting that BRCA2 is associated with fewer cases than BRCA1 (P=0.03). The specific BRCA2 mutation causing a deletion of thymine (6174delT), which is found in 1.3 percent of the Ashkenazi Jewish population, was observed in 1 of the 39 young Jewish women with breast cancer (2.6 percent; 95 percent confidence interval, 0.09 to 13.5 percent), indicating that it has a small role as a risk factor for early-onset breast cancer. Among young women with breast cancer, there are BRCA2 mutations that cause truncation of the extreme C terminus of the protein and that may be functionally silent, along with definite truncating mutations. CONCLUSIONS: Germ-line mutations in BRCA2 contribute to fewer cases of breast cancer among young women than do mutations in BRCA1. Carriers of BRCA2 mutations may have a smaller increase in the risk of early-onset breast cancer.     

Moderate frequency of BRCA1 and BRCA2 germ-line mutations in Scandinavian familial breast cancer

Previous studies of high-risk breast cancer families have proposed that two major breast cancer-susceptibility genes, BRCA1 and BRCA2, may account for at least two-thirds of all hereditary breast cancer. We have screened index cases from 106 Scandinavian (mainly southern Swedish) breast cancer and breast-ovarian cancer families for germ-line mutations in all coding exons of the BRCA1 and BRCA2 genes, using the protein-truncation test, SSCP analysis, or direct sequencing. A total of 24 families exhibited 11 different BRCA1 mutations, whereas 11 different BRCA2 mutations were detected in 12 families, of which 3 contained cases of male breast cancer. One BRCA2 mutation, 4486delG, was found in two families of the present study and, in a separate study, also in breast tumors from three unrelated males with unknown family history, suggesting that at least one BRCA2 founder mutation exists in the Scandinavian population. We report 1 novel BRCA1 mutation, eight additional cases of 4 BRCA1 mutations described elsewhere, and 11 novel BRCA2 mutations (9 frameshift deletions and 2 nonsense mutations), of which all are predicted to cause premature truncation of the translated products. The relatively low frequency of BRCA1 and BRCA2 mutations in the present study could be explained by insufficient screening sensitivity to the location of mutations in uncharacterized regulatory regions, the analysis of phenocopies, or, most likely, within predisposed families, additional uncharacterized BRCA genes.     

Genetic heterogeneity and penetrance analysis of the BRCA1 and BRCA2 genes in breast cancer families. The Breast Cancer Linkage Consortium

The contribution of BRCA1 and BRCA2 to inherited breast cancer was assessed by linkage and mutation analysis in 237 families, each with at least four cases of breast cancer, collected by the Breast Cancer Linkage Consortium. Families were included without regard to the occurrence of ovarian or other cancers. Overall, disease was linked to BRCA1 in an estimated 52% of families, to BRCA2 in 32% of families, and to neither gene in 16% (95% confidence interval [CI] 6%-28%), suggesting other predisposition genes. The majority (81%) of the breast-ovarian cancer families were due to BRCA1, with most others (14%) due to BRCA2. Conversely, the majority of families with male and female breast cancer were due to BRCA2 (76%). The largest proportion (67%) of families due to other genes was found in families with four or five cases of female breast cancer only. These estimates were not substantially affected either by changing the assumed penetrance model for BRCA1 or by including or excluding BRCA1 mutation data. Among those families with disease due to BRCA1 that were tested by one of the standard screening methods, mutations were detected in the coding sequence or splice sites in an estimated 63% (95% CI 51%-77%). The estimated sensitivity was identical for direct sequencing and other techniques. The penetrance of BRCA2 was estimated by maximizing the LOD score in BRCA2-mutation families, over all possible penetrance functions. The estimated cumulative risk of breast cancer reached 28% (95% CI 9%-44%) by age 50 years and 84% (95% CI 43%-95%) by age 70 years. The corresponding ovarian cancer risks were 0.4% (95% CI 0%-1%) by age 50 years and 27% (95% CI 0%-47%) by age 70 years. The lifetime risk of breast cancer appears similar to the risk in BRCA1 carriers, but there was some suggestion of a lower risk in BRCA2 carriers <50 years of age.     

Regulation of BRCA1 and BRCA2 expression in human breast cancer cells by DNA-damaging agents

Germline mutations in the breast cancer susceptibility genes BRCA1 and BRCA2 have been linked to the development of breast cancer, ovarian cancer, and other malignancies. Recent studies suggest that the BRCA1 and BRCA2 gene products may function in the sensing and/or repair of DNA damage. To investigate this possibility, we determined the effects of various DNA-damaging agents and other cytotoxic agents on the mRNA levels of BRCA1 and BRCA2 in the MCF-7 and other human breast cancer cell lines. We found that several agents, including adriamycin (a DNA intercalator and inhibitor of topoisomerase II), camptothecin (a topoisomerase I inhibitor), and ultraviolet radiation induced significant decreases in BRCA1 and BRCA2 mRNA levels. Decreased levels of BRCA1 and BRCA2 mRNAs were observed within 6-12 h after treatment with adriamycin and persisted for at least 72 h. Adriamycin also induced decreases in BRCA1 protein levels; but these decreases required several days. U.V. radiation induced dose-dependent down-regulation of BRCA1 and BRCA2 mRNAs, with significant decreases in both mRNAs at doses as low as 2.5 J/m2, a dose that yielded very little cytotoxicity. Adriamycin-induced down-regulation of BRCA1 and BRCA2 mRNAs was first observed at doses that yielded relatively little cytotoxicity and little or no apoptotic DNA fragmentation. Adriamycin and U.V. radiation induced distinct dose- and time-dependent alterations in the cell cycle distribution; but these alterations did not correlate well with corresponding changes in BRCA1 and BRCA2 mRNA levels. However, the adriamycin-induced reduction in BRCA1 and BRCA2 mRNA levels was correlated with p53 functional status. MCF-7 cells transfected with a dominant negative mutant p53 (143 val-->ala) required at least tenfold higher doses of adriamycin to down-regulate BRCA1 and BRCA2 mRNAs than did parental MCF-7 cells or control-transfected MCF-7 clones. These results suggest that BRCA1 and BRCA2 may play roles in the cellular response to DNA-damaging agents and that there may be a p53-sensitive component to the regulation of BRCA1 and BRCA2 mRNA expression.     

BRCA1 and BRCA2 in breast cancer families from Wales: moderate mutation frequency and two recurrent mutations in BRCA1

Mutations in the BRCA1/BRCA2 genes account for varying proportions of breast cancer families studied, and demonstrate considerable variation in mutational spectra coincident with ethnic and geographical diversity. We have screened for mutations in 17 families from Wales with two or more cases of breast cancer under age 50 and/or ovarian cancer. Eight out of 17 (47%) families had demonstrable mutations. Six out of 17 (35%) carried BRCA1 mutations and 2 out of 17 (12%) carried BRCA2 mutations. Two recurrent mutations in BRCA1 were identified, which appear to represent founder mutations in this population. These data support the existence of additional breast and ovarian cancer susceptibility genes.     

BRCA2 germline mutations in Swedish breast cancer families

Life-threatening situations in sarcoidosis are extremely rare. They may be due to failure of vital organs--lungs, heart, kidney, liver and brain--and usually due to irreversible fibrosis. Respiratory failure follows irreversible pulmonary fibrosis and the development of cor pulmonale. Cardiac sarcoidosis is more sinister for it may be silent, ill-recognised with sudden death or high morbidity. It needs sophisticated techniques to uncover this latent iceberg. Renal failure may be due to granulomatous interstitial nephritis and/or nephrocalcinosis. Hepatic failure is due to intrahepatic cholestasis, portal hypertension and bleeding oesophageal varices. Neurosarcoidosis carries a mortality of 10 per cent, over twice that of sarcoidosis overall. The treatment of each situation is discussed including organ transplantation.     

BRCA1 and BRCA2 mRNA levels are coordinately elevated in human breast cancer cells in response to estrogen

The steady state levels of BRCA1 and BRCA2 mRNAs were shown to be coordinately elevated by the steroid hormone estrogen but not progesterone in the human breast cancer cell lines BT-483 and MCF-7. Two different antiestrogens, trans 4'-hydroxytamoxifen and ICI 182,780, blocked the elevation of BRCA1 and BRCA2 mRNA levels, confirming that the effect was mediated through the estrogen receptor. In BT-483 cells, BRCA1 and BRCA2 mRNA levels were both elevated 18 to 24 h after estrogen stimulation, suggesting that the effect of estrogen was indirect. Cycloheximide blocked the estrogen effect implying that estrogen induces synthesis of an unidentified estrogen-responsive protein(s) that then result in the elevation of BRCA1 and BRCA2 mRNAs.