p300 binding by E1A cosegregates with p53 induction but is dispensable for apoptosis

E1A expression during adenovirus infection induces apoptosis. E1A expression causes accumulation of the p53 tumor suppressor protein, and E1A-induced apoptosis is p53 mediated in primary rodent cells, implying that p53 induction may be linked to apoptosis induction by E1A. Adenoviruses containing mutations in the E1A gene were tested for the ability to trigger both p53 accumulation and the appearance of enhanced cytopathy (cyt phenotype) and degradation of DNA (deg phenotype), indicative of apoptosis in infected HeLa cells. The adenoviruses had mutations which disrupted the pRb- and/or p300-binding activities of E1A so that the relationship between p53 induction and apoptosis and binding to these cellular proteins by E1A could be determined. An E1A mutation that specifically disrupted the p300-binding activity failed to induce p53 accumulation, whereas mutations in E1A which affected pRb binding induced p53 accumulation. Thus, p300 binding was required and pRb binding was dispensable for E1A-mediated accumulation of p53 in HeLa cells. All the E1A mutant viruses, regardless of the ability to induce p53 accumulation, induced the cyt and deg phenotypes, suggesting that p53 induction in infected HeLa cells was not essential for apoptosis, nor was binding of E1A to the pRb and/or p300 protein. The possibility that E1A induced a p53-independent apoptosis pathway was tested by analyzing the appearance of the cyt and deg phenotypes in Saos-2 cells, which were null for both alleles of p53, upon adenovirus infection. An adenovirus expressing wild-type 12S E1A induced both the cyt and deg phenotypes in Saos-2 cells, as did all the E1A mutant viruses. Thus, E1A expression during infection of human cells may trigger redundant p53-independent and -dependent apoptotic pathways.

Change in the use of breast-conserving surgery in western Washington after the 1990 NIH Consensus Development Conference

OBJECTIVE

To evaluate the use of breast-conserving surgery in western Washington before and after the National Institutes of Health Consensus Development Conference (June 18-21, 1990) during which breast-conserving surgery was recommended for most women with early invasive breast cancer.

DESIGN

Survey.

SETTING

Population-based cancer registry in the Seattle-Puget Sound (Washington) region.

PARTICIPANTS

The survey included 13541 women in whom American Joint Committee on Cancer stage I or II breast cancer was diagnosed between January 1, 1983, and December 31, 1993.

MAIN OUTCOME MEASURE

Proportion of participants who underwent breast-conserving surgery.

RESULTS

From April 1985, after results of a US randomized controlled trial showing equivalent survival in women undergoing mastectomy or breast-conserving surgery were published, to the time of the Conference, breast-conserving surgery was performed on 44.8% of women with stage I and 25.8% with stage II breast cancer. These percentages increased to 54.9% and 35.2%, respectively, during the post-Conference period. While women with stage II breast cancer were less likely than women with stage I breast cancer to undergo breast-conserving surgery before and after the Conference, trends for age and education were attenuated after the Conference. Differences in the use of breast-conserving surgery observed before the Conference between countries of residence and among hospital types were also reduced after the Conference.

CONCLUSIONS

These findings suggest that the Conference recommendations had an effect on the adoption of breast-conserving surgery, particularly among groups who were previously least likely to undergo such surgery. Despite progress toward the Conference recommendation that the majority of women with early invasive breast cancer undergo breast-conserving surgery, the majority of women with stage II breast cancer undergo mastectomy.

Using a brief household food inventory as an environmental indicator of individual dietary practices

OBJECTIVES

This study examined whether foods in household pantries are an indicator of house-hold members' diet.

METHODS

In a random-digit-dial survey, the presence in the house of 15 high-fat foods was assessed with whoever answered the phone. A randomly selected household member was surveyed about diet-related behaviors (n = 1002).

RESULTS

Individuals in the precontemplation stage of dietary change had more high-fat foods in their pantry than those in maintenance (means of 7.4 and 5.8, respectively). Individuals with low-fat pantries had an intake of 32% energy from fat vs 37% for those with high-fat pantries.

CONCLUSIONS

Household food inventories are a practical and valid approach to monitoring dietary behaviors in community-based studies.

Bcl-2 and the ICE family of apoptotic regulators: making a connection

Apoptosis, a genetically programmed mechanism of eliminating cells in response to a variety of stimuli, provides protection against cancer and viral infections as well as maintenance of homeostasis in living organisms. Two classes of molecules, the Bcl-2 family of regulators and the ICE family of proteases, have emerged from different vertebrate, invertebrate and viral systems that have been used to elucidate the pathways leading to apoptosis. However, no connection between these two disparate families of apoptotic regulators has been convincingly established. In reviewing the recent advances pertaining to the Bcl-2 and ICE-related protein families, one can address the question of a functional relationship between the two classes of proteins.

Leisure-time physical activity in relation to breast cancer among young women (Washington, United States)

It has been hypothesized that women who participate in vigorous physical activity may have lower risk of breast cancer due to lower lifetime exposure to ovarian hormones. A population-based case-control study was conducted to investigate the association between leisure-time physical activity and risk of breast cancer among women aged 21 to 45 years. Cases were 747 women diagnosed with invasive breast cancer between 1983 and 1990 in three counties of western Washington state (United States), and were identified through the Seattle-Puget Sound Surveillance, Epidemiology, and End Results (SEER) registry. Controls were 961 women selected from the same area by random-digit telephone dialing. Physical activity was assessed through personal interview, with questions on frequency and duration of each type of recreational activity during the two-year period immediately prior to reference data (date of diagnosis for cases and a comparable assigned date for controls) and between ages 12 and 21. For the two-year time period before diagnosis, there was no association with frequency of activity (age-adjusted odds ratio [OR] = 0.93, 95 percent confidence interval [CI] = 0.71-1.22 for four or more episodes per week cf none), total hours spent in physical activity (age-adjusted OR = 0.92, CI = 0.71-1.22 for four or more hours per week cf none) or MET (metabolic equivalent energy expenditure unit) (age-adjusted OR = 0.95, CI = 0.73-1.23 for 18 or more METs per week of none), nor any trend is risk with increasing activity levels. Similarly, there was no association between leisure activity during adolescence and breast cancer risk. These results were not confounded further by body mass index (wt/ht2), age at menarche, age at first full-term pregnancy, parity, family history of breast cancer, or other measured health behaviors. Our findings do not support a protective effect of leisure-time physical activity either in the adolescent years or in adulthood on breast cancer in young women.

Lamin proteolysis facilitates nuclear events during apoptosis

Expression of the adenovirus E1A oncogene stimulates both cell proliferation and p53-dependent apoptosis in rodent cells. p53 implements apoptosis in all or in part through transcriptional activation of bax, the product of which promotes cell death. The adenovirus E1B 19K product is homologous in sequence and in function to Bcl-2, both of which bind to and inhibit the activity of Bax and thereby suppress apoptosis. The E1B 19K protein also interacts with the nuclear lamins, but the role of this interaction in the regulation of apoptosis is not known. Lamins are, however, substrates for members of the interleukin-1 beta-converting enzyme (ICE) family of cysteine proteases that are activated during apoptosis and function downstream of Bcl-2 in the cell death pathway. lamins are degraded during E1A-induced p53-dependent apoptosis. Lamin A and C are cleaved into 47- and 37-kD fragments, respectively, and the site of proteolysis is mapped to a conserved aspartic acid residue at position 230. The cleavage of lamins during apoptosis is consistent with the activation of an ICE-related cysteine protease down-stream of p53. No lamin protease activity was detected in cells expressing the E1B 19K protein, indicating that 19K functions upstream of protease activation in inhibiting apoptosis. Substitution of the aspartic acid at the cleavage site produced a mutant lamin protein that was resistant to proteolysis both in vitro and in vivo. Expression of uncleavable mutant lamin A or B attenuated apoptosis, delaying cell death and the associated DNA fragmentation by 12 h. Mutant lamin expressing cells failed to show the signs of chromatin condensation and nuclear shrinkage typical of cell death by apoptosis. Instead, the nuclear envelope collapsed and the nuclear lamina remained intact. However, the late stage of apoptosis was morphologically unaltered and formation of apoptotic bodies was evident. Thus, lamin breakdown by proteolytic degradation facilitates the nuclear events of apoptosis perhaps by facilitating nuclear breakdown.

Length-dependent mechanisms in single cardiac cells

This brief review looks at recent work investigating length-dependent mechanisms in single cardiac cells. Studies using the mechanically simple single cardiac cell have confirmed much of the data previously reported in multicellular preparations, although some differences between single cell and multicellular studies have been found. Electrical studies have been able to investigate the effects of stretch on ion channels and have concentrated upon the exciting discovery of many types of stretch-activated channels in the heart. These channels may explain the occurrence of length-dependent changes in pacemaker activity and stretch-activated arrhythmias in the whole heart. Prolonged stretch can lead to hypertrophy, and single cell studies have been able to characterize the sequence of events leading from membrane stretch to altered protein expression. It appears from these studies that the role of angiotensin II is important.

Do beliefs, knowledge, and perceived norms about diet and cancer predict dietary change?

OBJECTIVES

We hypothesized that belief in an association between diet and cancer, knowledge of dietary recommendations and food composition, and perceived norms would predict healthful dietary changes.

METHODS

Data are from a population-based sample of Washington State residents (n = 607). Psychosocial constructs measured at baseline (1989/90) were used to predict changes in dietary practices, fat intake, fiber intake, and weight over 3 years.

RESULTS

Adults who strongly believed in a diet-cancer connection decreased the percentage of energy consumed from fat by 1.20 percentage points and increased fiber intake by 0.69 g, compared with decreases of 0.21 percentage points and 0.57 g among those with no belief (P < .05). Adults with knowledge of the National Cancer Institute fat and fiber goals decreased their percentage of energy from fat by 1.70 points compared with an increase of 0.27 points among those with little knowledge (P < .05). Food composition knowledge and perceived pressure to eat a healthful diet were not significant predictors of changes in fat intake, fiber intake, or weight.

CONCLUSIONS

Interventions that increase the public's beliefs in diet and health associations and communicate diet recommendations can encourage healthful dietary change.

Induction of apoptosis by human Nbk/Bik, a BH3-containing protein that interacts with E1B 19K

The E1B 19-kilodalton protein (19K protein) is a potent apoptosis inhibitor and the adenovirus homolog of Bcl-2 (E. White, Genes Dev. 10:1-15, 1996). To obtain a better understanding of the biochemical mechanism by which the E1B 19K protein regulates apoptosis, proteins that interact with 19K have been identified; one of these is Bax (J. Han, P. Sabbatini, D. Perez, L. Rao, D. Mohda, and E. White, Genes Dev. 10:461-477, 1996), and another is Bak (S. N. Farrow, J. H. M. White, I. Martinou, T. Raven, K.-T. Pun, C. J. Grinham, J.-C. Martinou, and R. Brown, Nature (London) 374:731-733, 1995). Bax and Bak are Bcl-2 family members which contain Bcl-2 homology regions 1, 2, and 3 (BH1, BH2, and BH3), which interact with E1B 19K and Bcl-2 and promote apoptosis. Like Bax and Bak, Nbk was cloned from a yeast two-hybrid screen for proteins that interact with E1B 19K. Nbk contained BH3 but not BH1 or BH2. It also interacted with Bcl-2 but not with Bax. Both Bcl-2 and E1B 19K interacted with Nbk in vitro, and this interaction was highly specific. In vivo, the Nbk and E1B 19K proteins may colocalize with cytoplasmic and nuclear membranes. Nbk expression functionally antagonized 19K-mediated inhibition of apoptotic cell death and completely prevented transformation by E1A and E1B 19K. Nbk was sufficient for induction of apoptosis in the presence of mutant p53 and thus low levels of Bax, suggesting that Nbk functions independently of Bax to induce apoptosis. Nbk may therefore represent a novel death regulator which contains only a BH3 that interacts with and antagonizes apoptosis inhibitors such as the E1B 19K protein.

Family history and survival of young women with invasive breast carcinoma

BACKGROUND

This study investigates whether a positive family history of breast carcinoma is associated with improved survival after invasive breast carcinoma among women ages 21 through 45.

METHODS

Subjects were 733 nonadopted women born after 1944 who were diagnosed with primary invasive breast carcinoma between January 1983 and April 1990 while residing in the metropolitan Seattle area and who provided information on family history of breast carcinoma. Information on clinical characteristics and survival was obtained from a population-based cancer registry. Subjects were followed for survival through 1994. Cox proportional hazards models were used to estimate the relative risk (RR) of dying in relation to family history of breast carcinoma, adjusting for selected clinical characteristics, age and year of diagnosis, and prior mammograms.

RESULTS

The risk of dying among women with a first-degree family history of breast carcinoma was half that of women with no family history of breast carcinoma (RR = 0.5%; 95% confidence interval [CI], 0.3-0.9). There was no evidence of a reduction in the risk of dying among women with only a second-degree family history of breast carcinoma (RR = 1; 95% CI, 0.6-1.4). These associations were adjusted for age and year of diagnosis, stage of disease, tumor size, bilaterality, and mammogram history. These findings were not further influenced by adjustment for initial treatment or the numbers and ages of relatives at risk for breast carcinoma.

CONCLUSIONS

Compared with women with neither a first- nor second-degree family history of breast carcinoma, the authors found that women who had a first-degree family history experienced increased survival. This finding did not appear to be attributable to differences in screening or treatment. To the extent that this difference is attributable to underlying biologic mechanisms, new insights into the natural history and treatment of breast carcinoma could result. Future studies should investigate whether specific susceptibility genes are associated with differential survival from breast carcinoma.

Estimating relative risk functions in case-control studies using a nonparametric logistic regression

The authors describe an approach to the analysis of case-control studies in which the exposure variables are continuous, i.e., quantitative variables, and one wishes neither to categorize levels of the exposure variable nor to assume a log-linear relation between level of exposure and disease risk. A dose-response association of an exposure variable with a disease outcome can be depicted by estimated relative risks at various exposure levels, and the functional relation between exposure dose and disease risk is here termed a relative risk function (RRF). A RRF takes values that are greater than zero: Values less than one imply lower risk; the value one implies no risk, and values greater than one imply increased risk, when compared with a reference value. The authors describe how a nonparametric logistic regression can be used to estimate and display these RRFs. Using data from a previously published case-control study of diet and colon cancer, RRFs for total energy, dietary fiber, and alcohol intakes are compared with the original results obtained from using categorized levels of exposure variables. For total energy and alcohol intakes, there were meaningful differences in study results based on the two analytic approaches. For energy, the nonparametric logistic regression detected a significant protective effect of low intakes, which was not found in the original analysis. For alcohol, the nonparametric logistic regression suggested that there were two underlying populations, non- or very light drinkers and moderate to heavy drinkers, with different relation of dose to disease risk. In contrast, the original analysis found a nonlinear increase in risk across intake categories and did not detect the complex, bimodal nature of the exposure distribution. These results demonstrate that nonparametric logistic regression can be a useful approach to displaying and interpreting results of case-control studies.

Breast cancer and hormonal contraceptives: further results. Collaborative Group on Hormonal Factors in Breast Cancer

The Collaborative Group on Hormonal Factors in Breast Cancer has brought together and reanalysed the worldwide epidemiological evidence on breast cancer risk and use of hormonal contraceptives. Original data from 54 studies, representing about 90% of the information available on the topic, were collected, checked and analysed centrally. The 54 studies were performed in 26 countries and include a total of 53,297 women with breast cancer and 100,239 women without breast cancer. The studies were varied in their design, setting and timing. Most information came from case-control studies with controls chosen from the general population; most women resided in Europe or North America and most cancers were diagnosed during the 1980s. Overall 41% of the women with breast cancer and 40% of the women without breast cancer had used oral contraceptives at some time; the median age at first use was 26 years, the median duration of use was 3 years, the median year of first use was 1968, the median time since first use was 16 years, and the median time since last use was 9 years. The main findings, summarised elsewhere, are that there is a small increase in the risk of having breast cancer diagnosed in current users of combined oral contraceptives and in women who had stopped use in the past 10 years but that there is no evidence of an increase in the risk more than 10 years after stopping use. In addition, the cancers diagnosed in women who had used oral contraceptives tended to be less advanced clinically than the cancers diagnosed in women who had not used them. Despite the large number of possibilities investigated, few factors appeared to modify the main findings either in recent or in past users. For recent users who began use before age 20 the relative risks are higher than for recent users who began at older ages. For women whose use of oral contraceptives ceased more than 10 years before there was some suggestion of a reduction in breast cancer risk in certain subgroups, with a deficit of tumors that had spread beyond the breast, especially among women who had used preparations containing the highest doses of oestrogen and progestogen. These findings are unexpected and need to be confirmed. Although these data represent most of the epidemiological evidence on the topic to date, there is still insufficient information to comment reliably about the effects of specific types of oestrogen or of progestogen. What evidence there is suggests, however, no major differences in the effects for specific types of oestrogen or of progestogen and that the pattern of risk associated with use of hormonal contraceptives containing progestogens alone may be similar to that observed for preparations containing both oestrogens and progestogens. On the basis of these results, there is little difference between women who have and have not used combined oral contraceptives in terms of the estimated cumulative number of breast cancers diagnosed during the period from starting use up to 20 years after stopping. The cancers diagnosed in women who have used oral contraceptives are, however, less advanced clinically than the cancers diagnosed in never users. Further research is needed to establish whether the associations described here are due to earlier diagnosis of breast cancer in women who have used oral contraceptives, to the biological effects of the hormonal contraceptives or to a combination of both. Little information is as yet available about the effects on breast cancer risk of oral contraceptive use that ceased more than 20 years before and as such data accumulate it will be necessary to re-examine the worldwide evidence.

Nutrient intake in relation to bladder cancer among middle-aged men and women

This population-based case-control study examined the association between selected nutrients, foods, and diet behaviors and bladder cancer. Bladder cancer cases (n = 262) were identified from the Surveillance, Epidemiology, and End Results Program cancer registry for western Washington, and controls (n = 405) were identified through random digit dialing. Cases were diagnosed between January 1987 and June 1990, and eligible subjects were Caucasian, aged 45-65 years, and residents of King, Pierce, or Snohomish counties. Subjects completed a self-administered, 71-item food frequency questionnaire and a structured telephone interview. Analyses were conducted by logistic regression analysis and included adjustment for age, sex, smoking (current, former, never), and county. Odds ratios and their 95% confidence intervals for highest versus lowest level of intake were examined. An inverse association was found between the risk of bladder cancer and dietary retinol (odds ratio (OR) across quartiles: 1.00, 1.09, 0.97, and 0.52; 95% CI 0.29-0.97; trend p value = 0.03) and dietary vitamin C (OR across quartiles: 1.00, 0.96, 0.67, and 0.50; 95% CI 0.28-0.88; trend p value = 0.009), adjusted for calories. The use of multivitamin supplements daily over the 10-year period ending 2 years before diagnosis versus no use was associated with a decreased risk of bladder cancer (OR = 0.39; 95% CI 0.24-0.63) as was use of supplemental vitamin C (OR for > 502 mg/day over the 10 years vs. none = 0.40; 95% CI 0.21-0.76). Increased intake of fruit was associated with a decreased risk of bladder cancer (OR across quartiles: 1.00, 1.24, 0.72, and 0.53; 95% CI 0.30-0.93; trend p value = 0.01, adjusted for calories), while increased use of fried foods was associated with an increased risk of bladder cancer (OR across quartiles: 1.00, 1.51, 1.81, and 2.24; 95% CI 1.25-4.03; trend p value = 0.006). This study provides modest evidence that certain nutrients, foods, and supplementation may affect the incidence of bladder cancer.

Community organization to promote breast cancer screening ordering by primary care physicians

Community organization has been viewed as a promising approach to changing preventive behaviors. We evaluated the impact of community organization strategies to promote breast cancer screening ordering by primary care physicians in Washington State. Physicians practicing in two intervention and two control communities were surveyed by mail pre-intervention (1989) and post-intervention (1993). Intervention activities targeting the health care sector included the formation of local physician planning groups, a series of informational mailings, medical office staff training sessions, and reminder system support. There were no significant post-intervention differences in the self-reported mammography ordering of physicians practicing in the intervention and control areas. Over the four-year study period, the proportions of physicians who ordered regular mammography increased by 36%. By 1993, over 80% of the respondents routinely used mammographic screening. Concerns about the high price of mammograms and inadequate insurance coverage were significantly reduced over time in both community pairs. Also, use of patient reminder systems increased significantly between 1989 and 1993. Secular trends resulting from diffusion of strategies to promote mammography were responsible for increases in physician ordering of the procedure. Year 2000 goals for breast cancer screening use by physicians may already have been met in some communities.

Nevi and migration within the United States and Canada: a population-based cross-sectional study

A survey to ascertain factors associated with benign melanocytic nevi or moles was conducted among randomly-selected White adults (aged 18 to 50 years) in Washington State (United States). Participants of the telephone interview in 1990-91 were questioned about lifetime places of residence and constitutional factors. Subjects counted raised nevi on their arms at the end of the survey. Logistic regression was used to examine the risk for two or more nevi compared with no nevi. Individuals who resided in warmer areas and lower latitudes than Washington State were at higher risk of having multiple nevi. This association held for residence at birth, during childhood, adolescence, and over lifetime: an odds ratio (OR) of 2.3 (95 percent confidence interval = 1.2-4.3) for lifetime average daily maximum temperature of > or = 64 degrees F compared with 58.9 degrees F, and similar ORs of 2.1 for adolescence and 1.8 for childhood. These associations remained significant after adjusting for potential confounding effects of constitutional factors and for childhood sunburns as a potential mechanism. Risk of multiple nevi was reduced for both early age at migration and longer duration of stay in Washington. These data are consistent with the importance of childhood and adolescent sun exposure in the etiology of nevi, but also suggest an effect of lifetime sun exposure.

Relationship of food groups and water intake to colon cancer risk

The association between food groupings and adenocarcinoma of the colon was investigated in a population-based case-control study of men and women ages 30-62 years. Colon cancer cases (238 men and 186 women) diagnosed from 1985 to 1989 were identified from the Seattle-Puget Sound Surveillance, Epidemiology, and End Results Registry. Controls (224 men and 190 women) were selected using a random digit telephone dialing method. Dietary information was gathered using an 80-item food frequency questionnaire. Foods were grouped and analyzed by quartile of intake, with adjustment for age and total energy intake. Among women, a reduced risk of colon cancer was associated with a high intake of fruits and vegetables [adjusted odds ratio (OR) for highest versus lowest quartile, 0.48; 95% confidence interval (CI), 0.26-0.86; P for trend, P = 0.02]. Inverse associations were also observed for the consumption of total (hot and cold) cereals (OR, 0.47; 95% CI, 0.25-0.91; P = 0.05), dairy products (OR, 0.40; 95% CI, 0.21-0.79; P = 0.05), and water (OR for > 5 glasses/day versus < or = 2 glass/day, 0.55; 95% CI, 0.31-0.99; P = 0.004). Among men, colon cancer risk was inversely associated with the intake of breads and cereals (OR, 0.43; 95% CI, 0.22-0.82; P = 0.02) and hot cereal (OR for weekly versus never eating, 0.53; 95% CI, 0.32-0.87; P = 0.01). Water consumption was marginally associated with a decreased colon cancer risk among men as well (OR for > 4 glasses/day versus < or = 1 glass/day, 0.68; 95% CI, 0.38-1.22; P = 0.16). Total meat consumption was associated with an increased risk of distal colon cancer among men (OR, 2.20; 95% CI, 1.08-4.48; P = 0.01). These results were not confounded by body mass index or other measured health behaviors. Results of this research support previous findings which associate intake of fruits, vegetables, grains, and dairy products with reduced colon cancer risk, and meat intake with an increased colon cancer risk. This study also reports a new finding of a possible inverse association of water consumption (glasses of plain water per day) with colon cancer risk.

Physical activity in relation to colon cancer in middle-aged men and women

A population-based case-control study was conducted to assess the relation between physical activity and colon cancer among men and women aged 30-62 years. Cases were 251 men and 193 women diagnosed with colon cancer in 1985-1989 in three countries in the Seattle metropolitan area who were identified from the Seattle-Puget Sound Surveillance, Epidemiology, and End Results registry. Controls were 233 men 194 women identified by random digit telephone dialing who were selected by stratified random sampling to approximate the age, sex, and county distribution of cases. Physical activity was assessed by questions on frequency and duration of types of recreational and occupational activities during the 10-year period ending 2 years before diagnosis. Each activity was classified as low intensity (< 4.5 METs ) or moderate to high intensity (> or = 4.5 METs). For men and women combined, moderate or high intensity recreational activity was associated with a decreased risk of colon cancer (relative risk (RR) for two or more times per week vs. none = 0.70, 95% confidence interval (CI) 0.49-1.00). This relation was stronger for men than women. Occupational activity was not associated with colon cancer, except among men younger than 55 (RR for > or = 14.5 hours per week of moderate activity vs. none = 0.29, 95% CI 0.12-0.69). Among men and women combined, total moderate or high intensity activity (occupational plus recreational) was marginally related to colon cancer (RR for > or = 5 hours per week vs. none = 0.78, 95% CI 0.55-1.10). These results were adjusted for age (and sex in the combined sex analyses) and were not confounded by body mass index, dietary factors, or other measured health behaviors. The results of this study provide modest support to the growing number of studies showing that recreational and/or occupational physical activity is associated with a reduced risk of colon cancer.

A possible mechanism for large stretch-induced increase in [Ca2+]i in isolated guinea-pig ventricular myocytes

OBJECTIVES

The aim of the study was to investigate the mechanisms responsible for provoking and maintaining a large, stretch-induced, increase in the level of resting calcium in single guinea-pig ventricular myocytes. In particular, we wished to test the relative importance of intracellular and extracellular sources of calcium in this phenomenon.

METHODS

Carbon fibres were used to stretch cells loaded with the fluorescent calcium indicator Indo-1. Sarcomere length and internal calcium activity ([Ca2+]i) were measured. Experimental results from our present and previous studies were compared with those predicted by the OXSOFT HEART (version 4) model of the guinea-pig ventricular myocyte incorporating a stretch-activated channel.

RESULTS

The stretch-induced increase in [Ca2+]i was found to be sensitive to removal of [Ca2+]o and application of the Ca(2+)-channel blocker verapamil (1 microM). The phenomenon was not sensitive to disruption of sarcoplasmic reticulum function by ryanodine (1 microM) nor to the Na+ channel blocker TTX (30 microM). Our experimental findings were reproduced in the modelling study.

CONCLUSIONS

The stretch-induced increase in [Ca2+]i is modulated by extracellular sources of Ca2+ rather than intracellular Ca2+ stores and is not indiscriminately sensitive to blockers of depolarizing current. We propose that the stretch-induced increase in [Ca2+]i may be triggered by activation of stretch-activated channels but that a combination of stretch-activated current and Ca(2+)-window current maintain the increased levels of resting [Ca2+]i.

Effect of estrogen replacement therapy on the specificity and sensitivity of screening mammography

BACKGROUND

Previous studies have demonstrated that mammographic breast density increases following the initiation of estrogen replacement therapy (ERT). The effect, if any, that this increase in density has on the specificity (related to false-positive readings) and the sensitivity (related to false-negative readings) of screening mammography is unknown.

PURPOSE

Using a retrospective cohort study design, we assessed the effects of ERT on the specificity and the sensitivity of screening mammography.

METHODS

Participants (n = 8779) were postmenopausal women, aged 50 years or older, who were enrolled in a health maintenance organization located in western Washington state and who entered a breast cancer screening program between January 1988 and June 1993. Two-view mammography was performed as part of a comprehensive breast cancer screening visit. Menopausal status, as well as demographic and risk-factor information, was recorded via self-administered questionnaires. Hormonal replacement therapy type and use were determined from questionnaire data and from an automated review of pharmacy records. Individuals diagnosed with breast cancer within 12 months of their first screening-program mammograms were identified through use of a regional cancer registry. Risk ratios (RRs) plus 95% confidence intervals (CIs) of false-positive as well as false-negative examinations among current and former ERT users (with never users as the reference group) were calculated. Reported P values are two-sided.

RESULTS

The specificity of mammographic screening was lower for current users of ERT than for never users or former users. Defining a positive mammographic reading as any non-normal reading (either suspicious for cancer or indeterminate), the adjusted RR (95% CI) of a false-positive reading for current users versus never users was 1.33 (1.15-1.54) (P < .001); for former users versus never users, the RR (95% CI) was 1.00 (0.87-1.15). The adjusted mammographic specificities (95% CIs) for never users, former users, and current users of ERT were 86% (84%-88%), 86% (84%-87%), and 82% (80%-84%), respectively. Defining a positive reading more rigorously (i.e., as suspicious for cancer only), the adjusted RRs (95% CIs) of false-positive readings for current users and former users (versus never users) were 1.71 (1.37-2.14) (P < .001) and 1.16 (0.93-1.45), respectively. Sensitivity was also lower in women currently receiving ERT. The unadjusted RR (95% CI) of a false-negative reading for current users versus never users was 5.23 (1.09-25.02) (P = .04); for former users versus never users, the RR (95% CI) was 1.06 (0.10-10.87). The unadjusted mammographic sensitivities (95% CI) for never users, former users, and current users of ERT were 94% (80%-99%), 94% (69%-99%), and 69% (38%-91%), respectively.

CONCLUSIONS AND IMPLICATIONS

Current use of ERT is associated with lower specificity and lower sensitivity of screening mammography. Lower specificity could increase the cost of breast cancer screening, and lower sensitivity may decrease its effectiveness.

A population-based study of contralateral breast cancer following a first primary breast cancer (Washington, United States)

To evaluate predictors of contralateral breast cancer risk, we examined data from a nested case-control study of second primary cancers among a cohort of women in western Washington (United States) diagnosed with breast cancer during 1978 through 1990 and identified through a population-based cancer registry. Cases included all women in the cohort who subsequently developed contralateral breast cancer at least six months after the initial diagnosis, but prior to 1992 (n = 234). Controls were sampled randomly from the cohort, matched to cases on age, stage, and year of initial breast cancer diagnosis. Information on potential risk factors for second primary cancer was obtained through medical record abstractions and physician questionnaires. Women who were postmenopausal due to a bilateral oophorectomy (i.e., a surgical menopause) at initial breast cancer diagnosis had a reduction in contralateral breast cancer risk compared with premenopausal women (matched odds ratio [mOR] = 0.25, 95 percent confidence interval [CI] = 0.09-0.68), whereas no reduction in risk was noted among postmenopausal women who had had a natural menopause (mOR = 0.90, CI = 0.39-2.09). Among postmenopausal women, there was a suggestion of a lower risk associated with relatively high parity (2+). A family history of breast cancer was associated with an increased risk (mOR = 1.96, CI = 1.22-5.15) and varied little by menopausal status. Having an initial tumor with a lobular component (c.f. a ductal histology) was not related strongly to risk (mOR = 1.47, CI = 0.79-2.74). The results of the present and earlier studies argue that we have limited ability to predict the occurrence of a contralateral breast tumor. Better predictors will be required before diagnostic and preventive interventions can be targeted to subgroups of patients with unilateral breast cancer.