Levonorgestrel-releasing intrauterine system and the risk of breast cancer: A nationwide cohort study

BACKGROUND

Prolonged steroid hormone therapy increases the risk of breast cancer, especially the risk of lobular cancer, but the effect of the levonorgestrel-releasing intrauterine system (LNG-IUS) use is controversial. In this study we aimed to test the hypothesis that risk for lobular breast cancer is elevated among LNG-IUS users.

MATERIAL AND METHODS

We identified from the national Medical Reimbursement Registry of Finland the women aged 30-49 who had used LNG-IUS for the treatment or prevention of menorrhagia in 1994-2007, and from the Finnish Cancer Registry breast cancers diagnosed before the age of 55 and by the end of 2012.

RESULTS

A total of 2015 women had breast cancer diagnosed in a cohort of 93 843 LNG-IUS users during follow-up consisting of 1 032 767 women-years. The LNG-IUS users had an increased risk for both ductal breast cancer [standardized incidence ratio (SIR) 1.20, 95% confidence interval (CI) 1.14-1.25] and for lobular breast cancer (SIR 1.33, 95% CI 1.20-1.46), as compared with the general female population. The highest risk was found in LNG-IUS users who purchased the device at least twice, whose SIR for lobular cancer was 1.73 (95% CI 1.37-2.15).

CONCLUSIONS

The results imply that intrauterine administration of levonorgestrel is not only related to an excess risk of lobular breast cancer but also, in contrary to previous assumptions, to an excess risk of ductal breast cancer.

Use of menopausal hormone therapy and risk of ductal and lobular breast cancer among women 55-74 years of age

The Women's Health Initiative (WHI) randomized trials found that use of combined estrogen and progestin menopausal hormone therapy (CHT) increases breast cancer risk, but use of unopposed estrogen hormone therapy (EHT) does not. However, several questions regarding the impact of hormone use on risk of different types of breast cancer and what thresholds of use confer elevations in risk remain. We conducted a population-based case-control study among women 55-74 years of age to assess the association between menopausal hormone use and risk of invasive ductal and invasive lobular breast carcinomas. Associations were evaluated using polytomous logistic regression and analyses included 880 ductal cases, 1,027 lobular cases, and 856 controls. Current EHT and CHT use were associated with 1.6-fold [95 % confidence interval (CI): 1.1-2.2] and 2.3-fold (95 % CI: 1.7-3.2) increased risks of lobular breast cancer, respectively, but neither was associated with risk of ductal cancer. Lobular cancer risk was increased after 9 years of EHT use, but after only 3 years of CHT use. Evidence across more than a dozen studies indicates that lobular carcinoma is the type of breast cancer most strongly influenced by menopausal hormones. Here, we characterize what thresholds of duration of use of both EHT and CHT that confer elevations in risk. Despite the rapid decline in hormone therapy use the WHI results were published, study of the hazards associated with these medications remains relevant given the estimated 38 million hormone therapy prescriptions that are still filled in the United States annually.

Immunohistochemical characterization of N-methyl-N-nitrosourea-induced mammary tumours of Sprague-Dawley rats

BACKGROUND

Single dose of N-methyl-N-nitrosourea (MNU) was shown to induce malignant tumours in susceptible rat strains. However, such tumours are not well-characterized.

MATERIAL AND METHODS

We characterized MNU-induced tumours in Sprague-Dawley rats using ultrasonographic, radiographic and immunohistochemical (IHC) methods.

RESULTS

In 27 rats, 41 tumours developed, appearing ultrasonographically as hypodense, non-homogenic areas with signal enhancement at their periphery. Out of these, 39 were of malignant epithelial origin, with an IHC phenotype closely-resembling that of human invasive ductal breast carcinoma. One case was diagnosed as carcinosarcoma. IHC analysis revealed that Ki-67 antigen expression correlated positively with tumour volume (r=0.40, p=0.0079). Moreover, tumours with α-smooth muscle actin in the tumour stroma were characterized by a higher proliferative rate as compared to those without its expression (p<0.05).

CONCLUSION

This rat model of chemical carcinogenesis may be suitable for examining breast cancer development and progression.

Estrogen plus progestin and breast cancer incidence and mortality in the Women's Health Initiative Observational Study

BACKGROUND

In the Women's Health Initiative (WHI) randomized trial, estrogen plus progestin increased both breast cancer incidence and mortality. In contrast, most observational studies associate estrogen plus progestin with favorable prognosis breast cancers. To address differences, a cohort of WHI observational study participants with characteristics similar to the WHI clinical trial was studied.

METHODS

We identified 41 449 postmenopausal women with no prior hysterectomy and mammogram negative within 2 years who were either not hormone users (n = 25 328) or estrogen and progestin users (n = 16 121). Multivariable-adjusted Cox proportional hazard regression was used to calculate hazard ratios (HRs) with 95% confidence intervals (CI). All statistical tests were two-sided.

RESULTS

After a mean of 11.3 (SD = 3.1) years, with 2236 breast cancers, incidence was higher in estrogen plus progestin users than in nonusers (0.60% vs 0.42%, annualized rate, respectively; HR = 1.55, 95% CI = 1.41 to 1.70, P < .001). Women initiating hormone therapy closer to menopause had higher breast cancer risk with linear diminishing influence as time from menopause increased (P < .001). Survival after breast cancer, measured from diagnosis, was similar in combined hormone therapy users and nonusers (HR = 1.03, 95% CI = 0.79 to 1.35). On a population basis, there were somewhat more deaths from breast cancer, measured from cohort entry (HR = 1.32, 95% CI = 0.90 to 1.93, P = .15), and more all-cause deaths after breast cancer (HR = 1.65, 95% CI = 1.29 to 2.12, P < .001) in estrogen plus progestin users than in nonusers.

CONCLUSIONS

Consistent with WHI randomized trial findings, estrogen plus progestin use is associated with increased breast cancer incidence. Because prognosis after diagnosis on combined hormone therapy is similar to that of nonusers, increased breast cancer mortality can be expected.

A genome-wide association study to identify genetic susceptibility loci that modify ductal and lobular postmenopausal breast cancer risk associated with menopausal hormone therapy use: a two-stage design with replication

Menopausal hormone therapy (MHT) is associated with an elevated risk of breast cancer in postmenopausal women. To identify genetic loci that modify breast cancer risk related to MHT use in postmenopausal women, we conducted a two-stage genome-wide association study (GWAS) with replication. In stage I, we performed a case-only GWAS in 731 invasive breast cancer cases from the German case-control study Mammary Carcinoma Risk Factor Investigation (MARIE). The 1,200 single nucleotide polymorphisms (SNPs) showing the lowest P values for interaction with current MHT use (within 6 months prior to breast cancer diagnosis), were carried forward to stage II, involving pooled case-control analyses including additional MARIE subjects (1,375 cases, 1,974 controls) as well as 795 cases and 764 controls of a Swedish case-control study. A joint P value was calculated for a combined analysis of stages I and II. Replication of the most significant interaction of the combined stage I and II was performed using 5,795 cases and 5,390 controls from nine studies of the Breast Cancer Association Consortium (BCAC). The combined stage I and II yielded five SNPs on chromosomes 2, 7, and 18 with joint P values <6 × 10(-6) for effect modification of current MHT use. The most significant interaction was observed for rs6707272 (P = 3 × 10(-7)) on chromosome 2 but was not replicated in the BCAC studies (P = 0.21). The potentially modifying SNPs are in strong linkage disequilibrium with SNPs in TRIP12 and DNER on chromosome 2 and SETBP1 on chromosome 18, previously linked to carcinogenesis. However, none of the interaction effects reached genome-wide significance. The inability to replicate the top SNP × MHT interaction may be due to limited power of the replication phase. Our study, however, suggests that there are unlikely to be SNPs that interact strongly enough with MHT use to be clinically significant in European women.

Alcohol and risk of breast cancer by histologic type and hormone receptor status in postmenopausal women: the NIH-AARP Diet and Health Study

Little is known about the association between alcohol and breast cancer by different tumor characteristics. The study consisted of 184,418 postmenopausal women aged 50-71 years in the National Institutes of Health-AARP Diet and Health Study (1995-2003). Alcohol use, diet, and potential risk factors for cancer were assessed with a mailed questionnaire at baseline. The relative risks and 95% confidence intervals were estimated by using Cox proportional hazards regression. Breast cancer cases and estrogen receptor and progesterone receptor status were identified through linkage to state cancer registries. During an average of 7 years of follow-up, 5,461 breast cancer cases were identified. Alcohol was significantly positively associated with total breast cancer: Even a moderate amount of alcohol (>10 g/day) significantly increased breast cancer risk. In a comparison of >35 g versus 0 g/day, the multivariate relative risks were 1.35 (95% confidence interval (CI): 1.17, 1.56) for total breast cancer, 1.46 (95% CI: 1.22, 1.75) for ductal tumors, and 1.52 (95% CI: 0.95, 2.44) for lobular tumors. The multivariate relative risks for estrogen receptor-positive/progesterone receptor-positive, estrogen receptor-positive/progesterone receptor-negative, and estrogen receptor-negative/progesterone receptor-negative tumors were 1.46 (95% CI: 1.12, 1.91) for >35 g versus 0 g/day, 1.13 (95% CI: 0.73, 1.77) for >20 g versus 0 g/day, and 1.21 (95% CI: 0.79, 1.84) for >20 g versus 0 g/day, respectively. Moderate consumption of alcohol was associated with breast cancer, specifically hormone receptor-positive tumors.

Hormone therapy and breast cancer risk

Hormone therapy (HT) is the most efficacious intervention for the relief of climacteric symptoms. Controversies surrounding HT have left many women puzzled and afraid. Gynecologists are faced with long-standing beneficial assumptions challenged by an abundance of robust detrimental new data, with little guidance on how to interpret these findings. Prescriptions for HT (and incidence of breast cancers in some areas) have fallen over the last 3 years due to anxiety provoked about breast cancer risk and recurrence. The current 'clinical climate' is against HT. Due to a lack of effective alternatives, women suffering from estrogen-deficiency symptoms are still requesting objective information about HT, particularly those at higher risk of breast cancer or those with a past history of breast cancer. In this situation, discussion of the current clinical uncertainty surrounding the use of HT must be undertaken to ensure that women are adequately informed. The objective of this presentation is to provide a framework for understanding breast cancer risk associated with HT. What are the precise molecular mechanisms of estrogen and progestin in the initiation of breast cancer? Does the risk of estrogen-only therapy on breast cancer vary by dose, constituent, route and duration of administration and cessation of use? Does HT, in addition to increasing risk for breast cancer, affect the type of breast cancer (lobular and ductal) diagnosed? Is HT associated with breast cancers that have better prognostic factors? How relevant are the changes in mammographic breast density associated with HT for the evaluation of breast cancer risk? What is the additional global health risk/benefit ratio associated with the selective use of progesterone or progestin that may confer a significant cardiovascular benefit, such as drospirenone? It is currently assumed and tested that new hormones with particular pharmacological profiles may ultimately achieve their therapeutic goal of relieving climacteric symptoms without an associated moderate increased risk of breast cancer.

[Secondary breast cancer after treatment for Hodgkin's disease. About seven cases]

OBJECTIVE

Therapeutic results of Hodgkin disease (HD) have improved by the use of combined radio-chemotherapy. However, this association can increase the risk of on-term effects including secondary cancers. In a retrospective study, we collected secondary breast cancer (BC) in patients previously treated with chemoradiotherapy for Hodgkin disease at Salah-Azaïz institute of Tunis.

PATIENTS AND METHODS

Between 1975 and 2003, seven patients (six women and one man) treated for HD subsequently developed BC. Mean age at diagnosis of HD was 21 years (12-29). The first treatment was combined chemotherapy (MOPP-ABVD) and radiotherapy for all patients. Radiotherapy was delivered with cobalt 60 with large fields. The median dose was 41.3 Gy (2 Gy/fraction in 6 patients and 3.3 Gy in one).

RESULTS

The breast tumours occurred after a median delay of 204 months (132-276). According to the TNM classification, we showed two stage T2, one stage T3, two stage T4b and two stage T4d. The mean clinical size was 47 mm (25-80 mm). All patients had infiltrating carcinoma. Axillary node histological involvement was found in 6 cases. All patients were treated by mastectomy and chemotherapy. Only one patient had a locoregional irradiation. Median survival was 26.5 months (12-48). Four patients died and three are still alive at respectively 24, 31 and 144 months.

DISCUSSION AND CONCLUSION

According to the previous data, breast cancer represents 6.3 to 9% of all second cancers occurring after HD treatment. We conclude that especially young women and girls treated for HD should be carefully monitored. We suggest that secondary BC be sometimes treated by conservative radiosurgical approach.

Aromatase inhibitors and male breast cancer

The majority of breast cancers in male patients are hormone receptor positive. Tamoxifen has proven to be successful in both adjuvant and metastatic settings and remains the standard of care. Given the improved outcomes in female patients with aromatase inhibitors (AI), these drugs have become a potential therapeutic tool for male patients. Preliminary data show effective suppression of oestradiol levels in males treated with AI and some reports have demonstrated objective responses. Here we report a case of a male patient with metastatic breast cancer treated with letrozole who achieved clinical response associated with a decrease in blood oestradiol levels.

Unopposed estrogen therapy and the risk of invasive breast cancer

BACKGROUND

Although short-term unopposed estrogen use does not seem to increase breast cancer risk, the effect of longer-term estrogen use remains unclear. We sought to assess the relationship between longer-term use of unopposed estrogen and the risk of invasive breast cancer over an extended follow-up period.

METHODS

Within the Nurses' Health Study, a prospective cohort study, we observed 11 508 postmenopausal women who had a hysterectomy and reported information on estrogen use at baseline (1980). The study population was expanded every 2 years to include women who subsequently became postmenopausal and had a hysterectomy, so that 28 835 women were included in the final follow-up period (2000-2002). Estrogen use was assessed from self-reported data on biennial questionnaires. The main outcome was invasive breast cancer.

RESULTS

A total of 934 invasive breast cancers were included in the analysis. Breast cancer risk increased with duration of unopposed estrogen use among longer-term users with the highest risk seen in cancers positive for estrogen receptor (ER+) and progesterone receptor (PR+). The multivariate relative risks (RRs) and 95% confidence intervals (CIs) for breast cancer with current use of unopposed estrogen for less than 5 years, 5 to 9.9 years, 10 to 14.9 years, 15 to 19.9 years, and 20 years or longer were, respectively, 0.96 (95% CI, 0.75-1.22), 0.90 (95% CI, 0.73-1.12), 1.06 (95% CI, 0.87-1.30), 1.18 (95% CI, 0.95-1.48), and 1.42 (95% CI, 1.13-1.77) (P for trend <.001). The risk of ER+/PR+ breast cancers was noted to be statistically significant after 15 years of current use (RR, 1.48; 95% CI, 1.05-2.07).

CONCLUSION

Users of unopposed estrogen were at increased risk of breast cancer but only after longer-term use.

Impact of teenage oral contraceptive use in a population-based series of early-onset breast cancer cases who have undergone BRCA mutation testing

Oral contraceptive (OC) use in young women has been associated with an increased risk of breast cancer. This matched case-control study aims to elucidate the combined effects of OC use and genetic factors in a population-based series of BRCA1/2 mutation-tested early-onset breast cancers. A first invasive breast cancer was diagnosed in 259 women aged 40 years between 1990 and 1995 in the South Swedish Health Care Region. A total of 245 women were included in this study. Information on family history of cancer, reproductive factors, smoking and OC use was obtained from questionnaires or patient charts. Three age-matched controls per case were chosen from a prospective South Swedish cohort. Ever OC use and current OC use were not associated with breast cancer. Cases were more likely to have used OCs before age 20 years (adjusted odds ratio (OR) 2.10 (95% CI 1.32-3.33)) and before their first child (adjusted OR 1.63 (95% CI 1.02-2.62)). When stratified by age, the effect of early OC use was limited to women diagnosed prior to age 36 years (OR 1.53 (1.17-1.99) per year of OC use prior to age 20 years). The risks were similar for low-dose and high-dose OCs. The probability of being a BRCA1/2 mutation carrier was three times higher among cases who started OC use prior to age 20 years compared with cases who started at age 20 years or older or who had never used OCs. However, the duration of OC use was similar among cases with and without BRCA1/2 mutations. No association was seen with a first-degree family history of breast cancer. Each year of OC use prior to age 20 years conferred a significantly increased risk for early-onset breast cancer, while there was no risk associated with use after age 20 years.

The effects of steroidal estrogens in ACI rat mammary carcinogenesis: 17beta-estradiol, 2-hydroxyestradiol, 4-hydroxyestradiol, 16alpha-hydroxyestradiol, and 4-hydroxyestrone

Several investigators have suggested that certain hydroxylated metabolites of 17beta-estradiol (E2) are the proximate carcinogens that induce mammary carcinomas in estrogen-sensitive rodent models. The studies reported here were designed to examine the carcinogenic potential of different levels of E2 and the effects of genotoxic metabolites of E2 in an in vivo model sensitive to E2-induced mammary cancer. The potential induction of mammary tumors was determined in female ACI rats subcutaneously implanted with cholesterol pellets containing E2 (1, 2, or 3 mg), or 2-hydroxyestradiol (2-OH E2), 4-hydroxyestradiol (4-OH E2), 16alpha-hydroxyestradiol (16alpha-OH E2), or 4-hydoxyestrone (4-OH E1) (equimolar to 2 mg E2). Treatment with 1, 2, or 3 mg E2 resulted in the first appearance of a mammary tumor between 12 and 17 weeks, and a 50% incidence of mammary tumors was observed at 36, 19, and 18 weeks respectively. The final cumulative mammary tumor incidence in rats treated with 1, 2, or 3 mg E2 for 36 weeks was 50%, 73%, and 100% respectively. Treatment of rats with pellets containing 2-OH E2, 4-OH E2, 16alpha-OH E2, or 4-OH E1 did not induce any detectable mammary tumors. The serum levels of E2 in rats treated with a 1 or 3 mg E2 pellet for 12 weeks was increased 2- to 6-fold above control values (approximately 30 pg/ml). Treatment of rats with E2 enhanced the hepatic microsomal metabolism of E2 to E1, but did not influence the 2- or 4-hydroxylation of E2). In summary, we observed a dose-dependent induction of mammary tumors in female ACI rats treated continuously with E2; however, under these conditions 2-OH E2, 4-OH E2, 16alpha-OH E2, and 4-OH E1 were inactive in inducing mammary tumors.

Acquired hemophilia as first manifestation of breast carcinoma in a man under long-term spironolactone therapy

A 69-year-old man under long-term spironolactone therapy (16 years) was hospitalized with spontaneous hematoma on the trunk and extremities. Coagulation studies disclosed an acquired hemophilia that was successfully treated with human factor VIII for a few days and immunosuppressive agents for several months. Physical examination revealed bilateral gynecomastia and an upper left quadrant breast nodule. Complete staging was unremarkable. Complete left mastectomy was performed. Histopathology showed invasive ductal carcinoma, expressing positivity for estrogen and progesterone receptors. The acquired hemophilia was considered to be a paraneoplasic syndrome. The question of a linkage between long-term spironolactone therapy and breast carcinoma is discussed.

Relation between use of antihypertensive medications and risk of breast carcinoma among women ages 65-79 years

BACKGROUND

Limited data are available regarding the incidence of breast carcinoma among users of relatively recently introduced forms of antihypertensive therapy. Although it has been suggested that women who have taken calcium channel blockers (CCBs) have an increased risk and that women who have taken angiotensin-I-converting enzyme (ACE) inhibitors have a decreased risk, currently, no conclusions can be drawn.

METHODS

A population-based case-control study of women ages 65-79 years was conducted in western Washington State. The responses of 975 women who were diagnosed with invasive breast carcinoma during 1997-1999 were compared with the responses of 1007 women in a control group. Associations between use of different types of antihypertensive medications and breast carcinoma incidence were evaluated using logistic regression.

RESULTS

Overall, women who had ever used CCBs, beta-blockers, or ACE inhibitors did not have an altered risk of breast carcinoma relative to women who had never used antihypertensive medications. Although the use of immediate-release CCBs, thiazide diuretics, and potassium-sparing diuretics was associated with modestly increased risks of breast carcinoma (odds ratio [OR], 1.5; 95% confidence interval [95% CI], 1.0-2.1; OR, 1.4; 95% CI, 1.1-1.8; and OR, 1.6; 95% CI, 1.2-2.1, respectively), the absence of any trend in the size of excess risk with increasing duration or with current versus former use of these agents argues for a cautious interpretation.

CONCLUSIONS

The use of particular types of antihypertensive medications, including immediate-release CCBs and certain diuretics, may increase the risk of breast carcinoma among older women. Additional studies are warranted to clarify these potential associations. Cancer 2003;98:1504-13.

Oral Contraceptives and the Risk of Ductal Breast Carcinoma in situ

Recent evidence suggests that oral contraceptive use is associated with little to no increased risk of invasive breast carcinoma. No study has examined the relationship between oral contraceptive use and the risk of non-invasive breast carcinoma, that is, breast carcinoma in situ.

OBJECTIVE

To define the role of oral contraceptive use in the development of breast carcinoma in situ.

METHODS

The data are 875 ductal carcinoma in situ (DCIS) cases diagnosed among residents of the state of Connecticut from September 15, 1994 to March 14, 1998 and between the age of 20 and 79 years as well as 999 control subjects. Controls are female Connecticut residents collected via random-digit-dial and frequency matched to the cases by 5-year age intervals. Telephone interviews were used to collect information on risk factors and cancer screening history. Logistic regression was used to provide maximum likelihood estimates of the odds ratios (OR) with 95% confidence intervals (95% CI).

RESULTS

The risk of being diagnosed with DCIS for women who had ever used oral contraceptives was not increased relative to women who had never used them (OR: 1.0, 95% CI: 0.8, 1.2). The risk did not significantly increase with duration of oral contraceptive use, nor with duration of high estrogen use, time since last use, progestin or estrogen type, or age at first use. Furthermore, the association between oral contraceptive use and DCIS risk did not vary by the presence of a family history of breast cancer or by menopausal status.

CONCLUSIONS

In these data, no evidence was found for an increased risk of ductal carcinoma in situ associated with the use of oral contraceptives.

Antidepressant medications and their association with invasive breast cancer and carcinoma in situ of the breast

BACKGROUND

Experimental studies in animals have suggested that antidepressants may promote the growth of mammary tumors, but epidemiologic data have not shown consistent associations between antidepressant use and breast cancer.

METHODS

We analyzed data from a population-based, case-control study conducted in North Carolina from 1996 to 2000 to examine the association between antidepressant use and breast cancer. Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) separately for invasive breast cancer and carcinoma in situ.

RESULTS

Over 20% of both cases and controls reported having ever used antidepressants. Overall, women with invasive breast cancer did not report antidepressant use more frequently than controls (OR = 1.0; CI = 0.7-1.2). There was a suggestion that use of selective serotonin reuptake inhibitor antidepressants for 36 months or more was more common among the breast cancer cases (OR = 2.7; CI = 0.9-7.9). Carcinoma in situ cases reported antidepressant use less frequently than controls (OR = 0.6; CI = 0.4-0.8). No consistent relation was observed between duration of use and carcinoma in situ.

CONCLUSIONS

Antidepressant use in general was not related to an increased risk of breast cancer. There may be increased risk associated with long-term use of SSRIs. Continued monitoring of this relation is warranted, given the high prevalence of use of these drugs in the general population.

Estrogenic and antiestrogenic properties of resveratrol in mammary tumor models

Trans-3,4',5-trihydroxystilbene (resveratrol), a phytoalexin present in grapes and grape products such as wine, has been identified as a chemopreventive agent. Recent studies performed with MCF-7 human breast cancer cells have demonstrated superestrogenic effects with resveratrol. In contrast, studies performed using estrogen receptor-transfected cell lines have shown that resveratrol acts as a mixed agonist/antagonist. The major objective of this study was to characterize the estrogen-modulatory effects of resveratrol in a variety of in vitro and in vivo mammary models. Thus, the effect of resveratrol alone and in combination with 17beta-estradiol (E2) was assessed with MCF-7, T47D, LY2, and S30 mammary cancer cell lines. With cells transfected with reporter gene systems, the activation of estrogen response element-luciferase was studied, and using Western blot analysis, the expression of E2-responsive progesterone receptor (PR) and presnelin 2 protein was monitored. Furthermore, the effect of resveratrol on formation of preneoplastic lesions (induced by 7,12-dimethylbenz(a)anthracene) and PR expression (with or without E2) was evaluated with mammary glands of BALB/c mice placed in organ culture. Finally, the effect of p.o. administered resveratrol on N-methyl-N-nitrosourea-induced mammary tumors was studied in female Sprague Dawley rats. As a result, in transient transfection studies with MCF-7 cells, resveratrol showed a weak estrogenic response, but when resveratrol was combined with E2 (1 nM), a clear dose-dependent antagonism was observed. Similar mixed estrogenic/antiestrogenic effects were noted with S30 cells, whereas resveratrol functioned as a pure estrogen antagonist with T47D and LY2 cells. Furthermore, in MCF-7 cells, resveratrol induced PR protein expression, but when resveratrol was combined with E2, expression of PR was suppressed. With T47D cells, resveratrol significantly down-regulated steady-state and E2-induced protein levels of PR. With LY2 and S30 cells, resveratrol down-regulated presnelin 2 protein expression. Using the mouse mammary organ culture model, resveratrol induced PR when administered alone, but expression was suppressed in the presence of E2 (1 nM). Furthermore, resveratrol inhibited the formation of estrogen-dependent preneoplastic ductal lesions induced by 7,12-dimethylbenz(a)anthracene in these mammary glands (IC50 = 3.2 microM) and reduced N-methyl-N-nitrosourea-induced mammary tumorigenesis when administered to female Sprague Dawley rats by gavage. Therefore, in the absence of E2, resveratrol exerts mixed estrogen agonist/antagonist activities in some mammary cancer cell lines, but in the presence of E2, resveratrol functions as an antiestrogen. In rodent models, carcinogen-induced preneoplastic lesions and mammary tumors are inhibited. These data suggest that resveratrol may have beneficial effects if used as a chemopreventive agent for breast cancer.

Methylselenocysteine modulates proliferation and apoptosis biomarkers in premalignant lesions of the rat mammary gland

In the rat mammary carcinogenesis model, premalignant lesions known as intraductal proliferations (IDPs) are detectable within a few weeks after carcinogen treatment. These early transformed colonies are the precursors for the eventual formation of carcinomas. Our past research indicated that methylselenocysteine added to the diet of rats reduced the development of IDPs of all sizes (the size of each IDP was estimated operationally by the number of 5-micron serial sections showing the same pathology). The appearance of an IDP lesion represents a balance between cell proliferation and cell death. The modulation of these two cellular events by methylselenocysteine was investigated. The abdominal-inguinal mammary gland was excised 6 weeks after MNU administration. Proliferation and apoptosis were evaluated by BrdU labeling and the TUNEL assay, respectively. The expression levels of several cell cycle and apoptosis regulatory proteins, including cyclin D1, cyclin A, p27, p16, bcl-2, box and bak, were also assessed. All of the above endpoints were quantified by immunohistochemistry in paraffin-embedded sections. The results showed that the magnitude of the response to methylselenocysteine intervention seemed to depend on the size of the IDP lesion. For the purpose of this study, the small and large lesions were classified as those containing < or = 30 or > 30 serial sections, respectively. With the small lesions, methylselenocysteine significantly inhibited BrdU labeling and the expression of cyclin D1 and cyclin A, but increased the expression of p27. Interesting, only p27 was upregulated in the larger IDP lesions, while BrdU labeling and the cyclins were not affected. It is possible that the transformed phenotype becomes less sensitive to selenium-mediated arrest of proliferation once it progresses to a more advanced pathological stage. In contrast, methylselenocysteine stimulated apoptosis (TUNEL assay) by 3 to 4 fold, and this increase was evident in both the small and large IDP lesions. Consistent with the induction of apoptosis, a reduced expression of bcl-2 was also observed in the methylselenocysteine group. In summary, our data suggest that exposure to methylselenocysteine blocks clonal expansion of premalignant lesions at an early stage. This is achieved by simultaneously modulating certain molecular pathways that are responsible for inhibiting cell proliferation and enhancing apoptosis.

Hormone replacement therapy in relation to risk of lobular and ductal breast carcinoma in middle-aged women

BACKGROUND

In the majority of studies, long term, recent use of hormone replacement therapy has been associated with an increased risk of breast carcinoma. However, little attention has been paid to the possibility that the magnitude of this association may vary according to the histologic type of breast carcinoma.

METHODS

In this population-based case-control study, interviews were conducted with 537 female residents of King County, Washington who were ages 50-64 years and who had been diagnosed with primary breast carcinoma between January 1, 1988 and June 30, 1990. Interviews with 492 randomly selected King County women without a history of breast carcinoma served as a basis for comparison. Analyses were performed separately for women with lobular and for those with ductal tumors.

RESULTS

Compared with nonusers of menopausal hormones, those who currently were using combined estrogen and progestin hormone replacement therapy (CHRT) and had done so for at least 6 months had an elevated risk of lobular breast carcinoma (odds ratio [OR] = 2.6; 95% confidence interval [95% CI], 1.1-5.8), but no change in their risk of ductal breast carcinoma was noted (OR = 0.7; 95% CI, 0.5-1. 1). The OR associated with current use of unopposed estrogen for at least 6 months was 1.5 (95% CI, 0.5-3.9) for lobular tumors and 0.7 (95% CI, 0.4-1.1) for ductal tumors. Similar results were found when cases of invasive tumor were analyzed separately.

CONCLUSIONS

The results of this study suggest that CHRT use increases the risk of lobular, but not ductal, breast carcinoma in middle-aged women.

Histopathology of mammary tumours in female rats treated with 1-methyl-1-nitrosourea

OBJECTIVE

To induce, evaluate and classify advanced stages of mammary gland tumours induced by MNU.

METHODS

Female Sprague-Dawley rats were injected intraperitoneally with 1-methyl-1-nitrosourea (MNU; 50 mg.kg-1) on the day 33, 40, 47, 54 and 61 of age in the first experiment and on 50th and 113th day in the second experiment. On the 117th day (first experiment) and on the 153rd day of age (second experiment) the rats were sacrificed by decapitation and their mammary glands were evaluated both macroscopically and microscopically for the presence of grossly detectable mammary tumours. Mammary tumours were classified according to Russo et al. (1990).

RESULTS AND CONCLUSIONS

The final incidence of palpable carcinomas was ranging from 60 % to 76 %. All microscopically evaluated tumours were malignant. Among the total number of lesions classified the percentage of invasive tumours ranged from 35 % to 44 %. No metastases were observed in other organs in MNU treated animals.

In vitro proliferation and in vivo malignancy of cell lines simultaneously derived from a chemically-induced heterogeneous rat mammary tumor

Identification of clones in primary tumors responsible for proliferation, invasion, and metastasis was carried out. Four different aneuploid established cell lines derived from a ductal infiltrating mammary rat tumor induced by 7,12-dimethylbenz[a]anthracene were studied for proliferative and growth features in vitro and for tumorigenic and metastatic potential in vivo in nude mice. Clones, named RM1, RM2, RM3, and RM4, were characterized by different proliferative activity. Clone RM1 showed the highest proliferative activity by both tritiated thymidine incorporation and S-phase flow cytometry, followed by clone RM4. Conversely, clones RM2 and RM3 showed a lower proliferation rate. Growth-promoting activity, tested on 3T3 Swiss cells, was high in all clones, although RM1 showed significantly lower growth factors-releasing activity. Nude mice tumorigenesis demonstrated a strong tumor induction of line RM1 (100% of the mice after 47 +/- 7 d) and a slightly lower tumor induction of line RM4 (70% of the mice after 69 +/- 9 d). Line RM3 showed tumor induction in 40% of the mice after 186 +/- 16 d. Lines RM2 showed no tumor induction. Metastasis occurred in mice treated with line RM1 only. Therefore, tumorigenesis and metastasis correlate with proliferation but not with the release of growth factors. In conclusion, flow cytometry monitoring of clones from heterogeneous primary tumors proved to be a suitable model for the study of in vivo malignancy and in vitro proliferation.

Neoplastic transformation of mammary epithelial cells in rats is associated with decreased apoptotic cell death

Previous studies have shown that terminal end buds (TEBs) in the murine mammary gland have high proliferative activity and demonstrate apoptotic cell death (ACD). Since TEBs are considered the place of origin of most chemically induced mammary carcinomas, we hypothesized that the development of hyperplastic and premalignant (carcinoma in situ, CIS) lesions in TEBs is associated with either a further increase in cell proliferation and/or with a decrease in ACD. To test this hypothesis we used the N-methyl-N-nitorosourea (MNU) carcinogenesis model in rats, where the occurrence of mammary tumors is preceded by hyperplastic and premalignant lesions arising mostly in TEBs, as well as in ducts and alveoli. The percentage of proliferating cells, as evaluated by 5-bromodeoxyuridine labeling (BrdU-LI), was similar in TEBs to those in terminal endbud hyperplasia (TEBH), CIS, and carcinomas (CA), whereas the percentage of apoptotic cells (apoptotic index, AI) was relatively high in TEBs and decreased in TEBH, CIS, and CA. This indicates that neoplastic transformation of mammary epithelial cells in TEBs is not associated with an increase in cell proliferation, but with a decrease in ACD. In addition to TEBH, hyperplastic lesions developed in ductal branching areas (ductal hyperplasia, DH) and alveolar structures (alveolar hyperplasia, AH). However, BrdU-LI in both DH and AH was lower than in TEBH, whereas the AI values were similar, suggesting that TEBH has a higher potential for progression and malignant transformation than DH and AH. In mammary tumors apoptotic cells were rare in the peripheral, proliferative areas, but frequent close to the necrotic areas, suggesting that intratumoral factors may significantly affect ACD. Thus, it appears that dissociation between cell proliferation and apoptosis occurs in the hyperplastic stages of mammary carcinogenesis and that neoplastic transformation of mammary epithelial cells is associated with decreased ACD but not with increased cell proliferation.

Hormone replacement and breast cancer: implications of the Iowa Women's Health Study

Amid conflicting reports about the link between hormone replacement therapy and breast cancer, the Iowa Women's Health Study gives grounds for cautious optimism. According to the study, women on hormone replacement therapy had a higher incidence of breast cancer, but the excess cancers were of a "favorable" histologic type. This paper discusses clinical decision-making in light of the study results.

Benign and malignant mammary tumors induced by DMBA in female Wistar rats

This study pretends to characterize 7, 12-dimetylbenz[a]anthracene-induced benign and malignant tumors. One hundred and twenty female Wistar rats were randomly allocated to two groups: Control Group and Induction Group; IG animals were given a single dose of DMBA and killed 24 weeks after. Other tumors besides breast tumors were diagnosed, mainly tumors of the salivary glands and ovarian benign epithelial tumors. Incidence of breast disorders was about 60%. Macroscopic mammary tumors varied in dimension from 2 mm to 55 mm. Malignant breast tumors (n = 56) were essentially invasive ductal carcinomas (91.1%), G1 (92.2%), presenting histologic characteristics of good prognosis. Predominant benign breast disorders consisted of glandular (68.6%) and atypical (20%) hyperplasias reproducing histologic types of human breast diseases. Different individual susceptibility to DMBA apparently occurs; while some rats never developed neoplasias, others exhibited several tumors.

Estrogen replacement therapy after localized breast cancer: clinical outcome of 319 women followed prospectively

PURPOSE

To determine whether estrogen replacement therapy (ERT) alters the development of new or recurrent breast cancer in women previously treated for localized breast cancer.

PATIENTS AND METHODS

Potential participants (n = 319) in a trial of ERT after breast cancer were observed prospectively for at least 2 years whether they enrolled onto the randomized trial or not. Of 319 women, 39 were given estrogen and 280 were not given hormones. Tumor size, number of lymph nodes, estrogen receptors, menopausal status at diagnosis, and disease-free interval at the initiation of the observation period were comparable for the trial participants (n = 62) versus nonparticipants (n = 257) and for women on ERT (n = 39) versus controls (n = 280). Cancer events were ascertained for both groups.

RESULTS

Patient and disease characteristics were comparable for the trial participants versus nonparticipants, as well as for the women on ERT versus the controls. One patient in the ERT group developed a new lobular estrogen receptor-positive breast cancer 72 months after the diagnosis of a ductal estrogen receptor-negative breast cancer and 27 months after initiation of ERT. In the control group, there were 20 cancer events: 14 patients developed new or recurrent breast cancer at a median time of 139.5 months after diagnosis and six patients developed other cancers at a median time of 122 months.

CONCLUSION

ERT does not seem to increase breast cancer events in this subset of patients previously treated for localized breast cancer. Results of randomized trials are needed before any changes in current standards of care can be proposed.

Effect of energy restriction on the expression of cyclin D1 and p27 during premalignant and malignant stages of chemically induced mammary carcinogenesis

The restriction of energy intake has a profound inhibitory effect on carcinogenesis, yet the mechanism or mechanisms that account for this effect are unknown. In this experiment, the hypothesis tested was that energy restriction upregulates the expression of p27/kip1, a gene product associated with cell-cycle growth arrest, while downregulating cyclin D1, a protein that combines with cyclin-dependent kinases to promote phosphorylation of retinoblastoma protein and the progression of cells through the cell cycle. We studied levels of these proteins in uninvolved mammary epithelial cells and in mammary intraductal proliferations, ductal carcinomas in situ, and adenocarcinomas induced in response to administration of 1-methyl-1-nitrosourea in animals fed either ad libitum or 90%, 80%, or 60% of ad libitum intake. Protein levels were evaluated immunohistochemically by using computer-assisted image analysis to quantify differences in protein expression among treatment groups. The expression of p27 increased and the expression of cyclin D1 decreased dose-dependently in response to energy restriction. The effect was greater on p27 than on cyclin D1. The hypothesis proposed is that energy restriction inhibits carcinogenesis by arresting cell-cycle progression by regulating p27/kip1.

Induction of mammary carcinomas by N-methyl-N-nitrosourea in ovariectomized rats treated with epidermal growth factor

The importance of epidermal growth factor (EGF) in both normal and malignant mammary gland development are presented in these studies. Initial findings demonstrated that in the absence of ovarian hormones, EGF had a significant proliferative effect on mammary epithelial cells. To determine whether mammary epithelial cells grown with EGF, in the absence of ovarian hormones, could be transformed by N-methyl-N-nitrosourea (MNU), female ovariectomized Lewis rats were implanted with pellets containing EGF for 1 week and then treated with MNU for initiation. Two days after MNU treatment, ovaries were implanted and EGF pellets were removed from all ovariectomized groups in order to promote carcinogenesis. The mammary carcinoma incidence of the EGF-stimulated group (90%) was not significantly different from the intact group (100%). The mammary cancer morphology of EGF-treated carcinomas was either ductal carcinoma or cribriform adenocarcinoma, whereas intact animals developed mainly papillary and occasional cribriform carcinomas. Fifty-eight percent of the carcinomas from the EGF group were ovarian hormone-independent compared with 10% of carcinomas from the intact group. These results demonstrate that EGF-induced proliferation during initiation with MNU was sufficient to induce the transformation of mammary carcinomas in the absence of ovarian hormones. The hormonal dependency of these EGF-induced carcinomas were different compared with MNU-initiated mammary carcinomas in intact rats.

Temporal sequence of mammary intraductal proliferations, ductal carcinomas in situ and adenocarcinomas induced by 1-methyl-1-nitrosourea in rats

An experimental model for mammary carcinogenesis has been described in which intraductal proliferations, ductal carcinomas in situ and adenocarcinomas can be readily detected and the frequency of their occurrence quantified. The objective of the experiment reported in this study was to determine the latency period between carcinogen administration and the occurrence of each of these types of lesion. A total of 150 female Sprague-Dawley rats were injected i.p. with 50 mg 1-methyl-1-nitrosourea (MNU)/kg body wt at 21 days of age. Groups of 30 rats each were killed at 7, 14, 21, 28 and 35 days post-carcinogen. Mammary intraductal proliferations were the first detected lesions and were observed in 20% of the animals at 14 days following carcinogen administration. At 21 days post-carcinogen ductal carcinomas in situ and adenocarcinomas were observed. The number of each type of lesion increased with time post-carcinogen, but the temporal pattern of occurrence was different among lesion types. The pattern of lesion occurrence was consistent with intraductal proliferations being a precursor lesion for ductal carcinomas in situ and adenocarcinomas. Furthermore, the data imply that ductal carcinomas in situ represent one pathway of morphological progression by which intraductal proliferations evolve into invasive carcinomas, but that this lesion type, as currently defined histologically, may not be an obligatory intermediate in morphologic progression. These findings are consistent with emerging evidence of multiple but distinct pathogenetic pathways leading to mammary carcinomas that display different morphological patterns and biological activities.

Relationship between immune state and tumor growth rate in rats bearing progressive and non-progressive mammary tumors

Impaired immune responses occur frequently in cancer patients or in tumor-bearing animals, but the mechanisms of the tumor-induced immune defects remain poorly understood. The aim of the present study was to determine the relevance of the immune system in the control of tumor growth. We have developed a model of progressive and non-progressive mammary tumor, chemically induced in female Wistar rats. In this model we evaluated the development of an immune response after immunization of rats bearing progressive and non-progressive tumors with a non-related antigen, such as sheep red blood cells. We also studied the activation state of peritoneal macrophages from animals bearing tumors by evaluating the production of free radicals. Our findings indicated that the cell-mediated immunity in rats bearing progressive tumors fails to respond to heterologous antigen in vivo, as demonstrated by a negative delayed-type hypersensitivity reaction, and is accompanied by minor nitric oxide production by peritoneal exudate cells as well as a lower capacity for macrophage activation. The study of non-progressive tumor-bearing rats indicated that the cell-mediated immune response was intact and an activated state of macrophages was found in vivo. The results described in this paper should be taken into account when therapies based on cancer vaccines are chosen for the treatment of cancer.

Effect of oyster mushroom (Pleurotus ostreatus) on pathological changes in dimethylhydrazine-induced rat colon cancer

The effect of 5% of dried oyster mushroom (Pleurotus ostreatus) in the diet on the dimethylhydrazine (DMH)-induced colon carcinogenesis was studied in male Wistar rats. DMH in a dose of 20 mg/kg of body weight was applied to animals once a week during a period of 12 weeks. Mushroom diet was applied either after treatment with DMH for another 21 weeks or during the whole experiment. Mushroom diet reduced significantly the incidence of lymphoid hyperplasia foci when mushroom was supplemented during the whole experiment. Tumour lesions could be characterized either as carcinoma in situ, or as infiltrating adenocarcinoma. Mushroom diet did not affect significantly the incidence of tumours. Nevertheless, a reduction in total number of tumours was observed in both groups of animals fed mushroom diet. A significant reduction of the number of tumour foci of the type carcinoma in situ was observed in animals fed the oyster mushroom during the whole experiment. Also these animals had the significantly lower number of aberrant crypt foci. Mushroom diet reduced the ornithine decarboxylase activity in the colon and in the liver when oyster mushroom diet was administered during the whole experiment.

A rat model of pancreatic ductal adenocarcinoma: targeting chemical carcinogens

BACKGROUND

Current experimental models of pancreatic cancer either fail to reproduce the ductal phenotype or cause simultaneous cancers in other organs also. To develop an animal of pancreatic cancer that accurately mimics the human condition, we restricted carcinogenic exposure to the pancreas and specifically targeted ductal epithelial cells. Three different carcinogens were either implanted directly into the pancreas or infused into the pancreatic duct, with or without near-total pancreatectomy (as a means of inducing pancreatic ductal cell proliferation).

METHODS

Groups of male Sprague-Dawley rats were exposed to varying doses of dimethylbenzanthracine (DMBA), methynitronitrosoguanidine, or ethylnitronitrosoguanidine either through direct implantation into the pancreas or infusion into the pancreatic duct. Near-total pancreatectomy was added in all groups except two DMBA implantation groups. Surviving rats were killed at 3, 6, 9, or 12 months, and the pancreata were evaluated histologically.

RESULTS

All three carcinogens caused pancreatic inflammation, ductal hyperplasia, atypia, and dysplasia beginning by 3 months and becoming more prominent at later time points. Only DMBA caused frequent invasive pancreatic ductal adenocarcinoma, which was first evident by 6 months. The prevalence of pancreatic cancer among DMBA-treated rats evaluated after 10 months was 39% (19 of 49). The addition of pancreatic resection did not enhance pancreatic cancer development.

CONCLUSIONS

Of the strategies tested, only direct implantation of DMBA into the rat pancreas frequently produces pancreatic cancer histologically similar to human ductal adenocarcinoma. The development of hyperplastic, atypical, and dysplastic changes preceding and accompanying carcinomas suggests that these lesions are preneoplastic. This model recapitulates the progression from normal to neoplastic epithelium and is likely to be useful for the study of morphologic and molecular mechanisms underlying the early stages of pancreatic carcinogenesis and for the investigation of novel diagnostic and therapeutic techniques.

K-ras and p53 mutations in hamster pancreatic ductal adenocarcinomas and cell lines

K-ras and p53 gene alterations are frequently found in human pancreatic carcinomas and cell lines. The aim of this study was to analyze for the presence of K-ras and p53 gene mutations in hamster pancreatic tumors and cell lines. Mutations at the first coding exon of the K-ras gene and in exons V to VIII of the hamster p53 gene were analyzed in six cell lines (H2T, PC1, PC1.2, PC1.0, WD, and PD) and in N-nitroso-bis(2-oxopropyl)amine-induced pancreatic (n = 9) and extra-pancreatic (n = 4) tumors. K-ras mutations were present in seven of the nine pancreatic tumors and in all extra-pancreatic tumors. No p53 mutations were detected in the tumors. All cell lines analyzed contained K-ras mutations. Moreover, four of the six cell lines contained single amino acid substitutions in the p53 gene. Cell lines derived from nitrosamine-induced pancreatic tumors in the hamster contained K-ras and p53 alterations similar to those found in cell lines derived from human pancreatic carcinomas.

Receptors characterization of intraperitoneally N-nitroso-N-methylurea-induced mammary tumors in rats

Mammary adenocarcinomas induces in female Sprague-Dawley rats by three intraperitoneal injections of N-nitroso-N-methylurea were studied in order to characterize their estrogen (ER), progesterone (PgR), prolactin (PRLR) and epidermal growth factor (EGFR) receptors. All samples evaluated showed the presence of ER and PgR in the cytosol fraction and PRLR amd EGFR in the membrane fraction. Q (fmol/mg) and K(d) (nM) values were as follows: ER, 56 +/- 11 and 0.5 +/- 0.1; PgR, 109 +/- 25 and 2.2 +/- 0.5 and PRLR, 335 +/- 75 and 0.5 +/- 0.2, respectively. In all tumors studied, two specific sites were found for EGFR, one with Q(1) = 22 +/- 9 and K(d1) = 0.6 +/- 0.3, and the other with Q(2) = 125 +/- 33 and K(d2) = 2.1 +/- 0.5. Receptor content was found to be independent of tumor histopathological variety. Displacement index (DI) with estradiol and tamoxifen of [I(3)H]E2-ER binding showed great heterogeneity, with values ranging from 0.01 to1.54. No correlation between ER content and DI values was found. Antiestrogenic binding sites were not found in the microsomal fraction of ten mammary tumors examined. Proliferation of this experimental mammary tumor may be regulated by a complex interaction of steroid and polypeptide hormones, as well as growth factors.

High yields of K-ras mutations in intraductal papillary mucinous tumors and invasive adenocarcinomas induced by N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine in the pancreas of female Syrian hamsters

Ductal adenocarcinoma, the most common form of pancreatic cancer in humans, is associated with activation of the K-ras oncogene in approximately 90% of cases. In contrast, K-ras mutations are found in < 50% of the relatively rare intraductal papillary mucinous tumor (IPMT), which arises in the main pancreatic ducts. Since both adenocarcinomas and IPMTs are believed to arise from ductal cells and progress through similar sequences of morphological changes (i.e. flat hyperplasia, papillary hyperplasia, atypia and carcinoma in situ), it is clear that such progression may not always necessitate activation of the ras oncogene. Experimentally ductal adenocarcinomas of the pancreas can be induced in the hamster model by a brief treatment with N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine (HPOP), while IPMTs can be induced by a combined treatment with HPOP and orotic acid (OA) in an initiation/promotion schedule. Since animals are exposed to the carcinogen only once, initiated normal epithelium is expected to give rise to a wide spectrum of neoplastic and preneoplastic lesions, progression of which will depend on the extent of mutagenesis induced at initiation in the targeted cells. In order to investigate the role of K-ras in progression of IPMTs as compared with adenocarcinomas we have examined the presence of K-ras mutations in the above two types of experimentally induced pancreatic cancers, as well as in associated and preneoplastic lesions. K-ras mutations at codons 12, 13 and 61 were determined by a designed restriction fragment length polymorphism method using mismatched nested primers in 77 neoplastic and preneoplastic foci microdissected from 20 pancreases. Mutations were found in all foci of atypical hyperplasia, in carcinomas in situ and invasive cancer, whether such lesions originated in lobular tissue or in the main pancreatic duct. Mutations were also found in papillary hyperplasia and flat hyperplasia in small ducts and also in the main duct at high frequency. With one exception, all ras mutations were G-->A transitions at the second base of codon 12. Mutations were occasionally accompanied by excessive presence of the mutant ras allele or loss of the wild-type ras allele, events that were more frequent in atypical hyperplasia (5/17), carcinomas in situ (5/14), IPMTs (2/5) and invasive adenocarcinomas (2/5) than in flat hyperplasia (0/6) or papillary hyperplasia (2/18). Our results demonstrate that: (i) K-ras mutations, predominantly G-->A transitions, are present in all experimentally induced hamster tumors; (ii) the incidence of K-ras mutations in IPMTs is lower in humans than in the hamster model; (iii) advanced lesions in both adenocarcinomas and IPMTs were frequently associated with an excess of the mutant over the wild-type K-ras allele. It is likely that both adenocarcinomas and IPMTs induced chemically in the hamster model arise by mechanisms which involve early activation of K-ras. Such a mechanism seems to be applicable only in a fraction of human IPMTs.

Rapid induction of mammary intraductal proliferations, ductal carcinoma in situ and carcinomas by the injection of sexually immature female rats with 1-methyl-1-nitrosourea

While most data in the literature indicate that chemically-induced mammary carcinogenesis in the rat proceeds through morphologically identifiable stages, little quantitative data exist on the frequency of their occurrence. A carcinogen induction protocol is reported that defines conditions under which approximately 38% of detectable lesions in the abdominal-inguinal mammary glands were histologically classified as either intraductal proliferations or ductal carcinoma in situ. The remainder of the lesions were classified as carcinomas. This response was observed in a group of 30 female Sprague-Dawley rats injected i.p. with 50 mg 1-methyl-1-nitrosourea (MNU)/kg body wt at 21 days of age. The experiment was terminated 35 days following carcinogen administration. The methods used to prepare whole mounts and to identify, excise and process lesions in the whole mounts to permit histological classification are described in detail. This carcinogenesis protocol also induced a significant palpable tumor response. The first palpable tumor, histologically classified as an adenocarcinoma, was observed 30 days post carcinogen administration. When the experiment was terminated (35 days post MNU), the cumulative incidence of palpable carcinomas was 60%. The rapidity of the carcinogenic response was remarkable. Unlike the i.v. administration of 7,12-dimethylbenz[a]anthracene (DMBA) to rats of this age, MNU injection resulted in > 99% incidence of palpable mammary gland tumors that were malignant. The data reported in this paper confirm and support the pathogenetic pathway described for the induction of mammary tumors in the rat by DMBA. The induction of mammary carcinogenesis in immature animals described in this paper may be of value in the investigation of early morphologically identifiable stages of this disease process as well as providing an extremely rapid method for tumor induction.

Chemopreventive activity of Oltipraz against N-nitrosobis(2-oxopropyl)amine (BOP)-induced ductal pancreatic carcinoma development and effects on survival of Syrian golden hamsters

The synthetic dithiolethione Oltipraz has marked cancer chemopreventive and phase II enzyme inducing activity in various animal carcinogenesis models, but has not been examined in any animal models of ductal pancreatic cancer relevant to the human disease. The chemopreventive potential of Oltipraz on pancreatic tumor incidence and multiplicity was examined in the N-nitrosobis(2-oxopropyl)-amine (BOP)-induced ductal pancreatic adenocarcinoma model in Syrian hamsters. Animals were maintained on control semipurified diets or semipurified diets containing 300 and 600 mg/kg Oltipraz beginning 2 weeks prior to BOP initiation and throughout the 26 week study. Oltipraz at 300 mg/kg had no effect on the incidence or multiplicity of preneoplastic, neoplastic or metastatic lesions, while at 600 mg/kg dietary Oltipraz the incidence of pancreatic adenocarcinomas was reduced significantly (P < or = 0.05) compared to BOP-treated controls. Dietary Oltipraz at both doses had a significant influence on reducing mortality and morbidity in tumor-bearing animals with metastatic disease. At 26 weeks, total hepatic glutathione-S transferase (GST) activity and GST mu activity were elevated significantly in Oltipraz-treated animals, while total pancreatic GST activity was reduced, albeit not significantly. Serum lipase activity, a marker for pancreatic damage, exhibited a progressive decline in BOP-treated animals administered Oltipraz compared to BOP-treated controls at 12 weeks of the study; by week 26, lipase activity was comparable in all groups and reduced compared to activity at week 12. Positive nuclear immunostaining for the p53 tumor suppressor protein, a hallmark of human pancreatic cancer and a transient response to DNA damage, was observed in only a small percentage of BOP-induced pancreatic lesions and was not influenced Oltipraz administration. Further chemoprevention and pharmacologic studies of Oltipraz in relevant animal models of ductal pancreatic cancer could provide a foundation for future studies in human populations at potential risk for pancreatic cancer.

Multiple genetic alterations in hamster pancreatic ductal adenocarcinomas

Pancreatic ductal adenocarcinomas induced in the Syrian golden hamster (SGH) by N-nitrosobis(2-oxopropyl)amine share many similarities with the human disease, including mutations of the K-ras oncogene. In vitro carcinogenesis studies with immortal SGH pancreatic duct cells indicate that neoplastic transformation in this system can occur without mutational inactivation of p53 suppressor gene. In this study we extend the genetic analysis of the in vivo SGH model to increase the number of cases analyzed for the status of K-ras and to determine further the spectrum of alterations involved; we have studied the status of the p53, DCC, and Rb-1 suppressor genes and the status of the mdm2 oncogene, which can involve p53 indirectly. The partial SGH-coding sequence of mdm2 and DCC was determined. K-ras mutation in the second position of codon 12 was present in 17 of 19 (90%) of tumors. Immunohistochemistry and single strand conformation polymorphism analysis showed no evidence of p53 mutation in 21 tumors. RNase protection assays showed overexpression of mdm2 in 5 of 19 (26%) tumors. Semiquantitative reverse transcription-PCR analysis showed a complete or partial loss of DCC expression in 10 of 19 (53%) neoplasms and of Rb-1 (42%) expression in 8 of 19 tumors when compared to matched controls. Deregulation of these genes appears to be significant in SGH pancreatic carcinogenesis as indicated by their frequencies. However, the fact that 6 tumors showed either only a K-ras mutation or the absence of alterations of the 5 genes analyzed indicates that additional as yet unstudied or unknown genes are also involved in SGH pancreatic duct carcinogenesis.

Induction at high incidence of ductal prostate adenocarcinomas in NBL/Cr and Sprague-Dawley Hsd:SD rats treated with a combination of testosterone and estradiol-17 beta or diethylstilbestrol

This study determined the incidence of prostate adenocarcinoma following long-term treatment of NBL and Sprague-Dawley rats with estradiol-17 beta or diethylstilbestrol (DES) plus testosterone and it defined the origin of these tumors. NBL and Sprague-Dawley rats were treated with two Silastic tubing implants (i.d. 1.6 mm, o.d. 3.2 mm) containing a 2 cm long filling of testosterone and one implant containing a 1 cm long filling of estradiol-17 beta or DES. Control animals received empty implants. Treated animals were killed when moribund and controls were killed at 91 (NBL) or 75 (Sprague-Dawley) weeks after initiation of treatment and accessory sex glands were sampled for histopathological examination of multiple step sections. Prostatic adenocarcinoma occurred in 100% of NBL rats after treatment with estradiol-17 beta or DES plus testosterone for 44 and 59 weeks (group means) respectively. Adenocarcinoma incidences were lower in Sprague-Dawley rats. The adenocarcinomas were small, microscopic, invasive tumors and they were spatially closely associated with the periurethral ducts of the dorsal, lateral and/or anterior (= coagulating gland) prostate, but never with the ducts of the ventral lobe and seminal vesicles. One adenocarcinoma was of uncertain origin. Duct-acinar dysplastic lesions occurred in the periphery of the dorsal and lateral prostate of all hormone-treated NBL and many Sprague-Dawley rats, but did not appear to give rise to carcinoma. Although some adenocarcinomas were contiguous with dysplastic ducts of the peripheral dorsolateral prostate, the main mass of these neoplasms was located in the periurethral area. Also, most adenocarcinomas were only connected with the periurethral ducts, in which atypical hyperplasia occurred following hormone treatment for 36 weeks or longer. Thus atypical hyperplasia of the periurethral prostate ducts, but not peripheral duct-acinar dysplasia, appeared to be the likely precursor of the induced carcinomas. Testosterone plus DES, but not estradiol-17 beta, induced marked dysplasia-like lesions in the acini of the ventral prostate of all NBL and many Sprague-Dawley rats. These lesions had progressed to carcinoma in situ (or adenoma) in 46% of NBL rats.

Induction of ductal carcinomas by intraductal administration of 7,12-dimethylbenz(a)anthracene in Wistar rats

Postpartum Wistar inbred rats (weaned on the 9th puerperal day) were injected intraductally in one mammary gland with 7,12-dimethylbenze (a) anthracene (DMBA) to selectively induce ductal carcinoma. The incidence of ductal hyperplasia increased with time until it peaked at 7 weeks (12/13 animals) and then decreased. Ductal carcinoma first developed at 9 weeks in 3/12 (2 non-invasive and 1 invasive lesion) and the incidence increased with time until invasive ductal tumors were observed in 9/11 at 20 weeks. Tumors developed only in the DMBA-treated mammary glands and no systemic effects of the carcinogen were observed. Degeneration and detachment of epithelioglandular cells were seen here and there in the ducts and terminal ducts, and epithelioglandular cells proliferated in terminal duct until 2 weeks. Residual trace DMBA powder was detected in terminal ducts and the epithelioglandular layer until 7 weeks. This trace DMBA was considered to be the cause of the development of atypical epithelial cells, inducing ductal carcinomas.

[Multiple neoplasms after a well succeeded treatment of Hodgkin's disease]

The authors refer to a 21-year-old Caucasian (white) woman, who in 1977 presented fever and cervical and axillary adenopathy, whose biopsy showed nodular sclerosis Hodgkin's Disease, stage IIIB. The patient received six chemotherapy cycles associated with immunotherapy and supplemented with radiation therapy with good response. RESULTS--In 1985, after routine gynaecological examination and a hysterectomy, cervical intraepithelial neoplasia grade 3 (CIN 3) and atypic leiomyoma of the uterine body were diagnosed. Five years later, biopsies diagnosed invasive duct carcinoma in the right breast and homolateral axillary and cervical nodes. The patient was submitted to chemo and radiation therapy and died nine months later. CONCLUSION--The possibility of later occurrence of a second or multiple new malignancies in patients successfully treated for Hodgkin's Disease points out the need for a more complete long-term follow-up, including periodic mammography.

Characterization of three cloned cell lines from a N-nitrosobis(2-hydroxypropyl)amine-induced transplantable hamster pancreatic ductal adenocarcinoma

To investigate characteristics of pancreatic carcinoma growth behavior, the cloned cell lines, HPD1NR, HPD2NR, and HPD3NR, were established from a transplantable hamster ductal adenocarcinoma induced by N-nitrosobis(2-hydroxypropyl)amine (BHP). All three clones showed similar epithelial cell morphology and grew as sheets in culture with no differences in doubling times, ranging from 23-28 h. Mutation in the c-Ki-ras exon 1 was detected in common. The modal chromosome numbers were also found to be similar at 60, 62, and 60-62 in the less than tetraploid cells in the three clones. In contrast, a clear difference in frequencies of tetraploid or polyploid cells at 24.7, 22.5, and 75.5% in HPD1NR, HPD2NR, and HPD3NR, respectively, was evident. Tumorigenic potency evaluated by transplanting individual clones revealed HPD3NR to display pronouncedly less growth in syngeneic hamsters. The results suggest that increase in frequency of tetraploid or polyploid cells might be associated with a decreased in vivo growth potential of hamster pancreatic ductal adenocarcinomas, and suggest that these clones might become a valuable tool for understanding in vivo growth mechanisms of cancer cells.

Genomic p53 mutation in a chemically induced hamster pancreatic ductal adenocarcinoma

This study investigates possible alterations in exons 5 through 8 of the p53 gene and altered p53 protein expression in the Syrian golden hamster model of pancreatic ductal adenocarcinoma. In the Syrian hamster p53 sequence, 1469 base pairs are presented for the genomic regions surrounding exons 5 through 8, along with the primer sequences specific for the enzymatic amplification of the individual exons. Single-stranded conformation polymorphism was analyzed on the products obtained by enzymatic amplification of hamster genomic DNA extracted from 2 transplantable pancreatic ductal adenocarcinomas, 6 groups of N-methylnitrosourea (MNU)-treated pancreatic duct cells, and 17 MNU-induced pancreatic ductal adenocarcinomas. The two transplantable adenocarcinomas were a well-differentiated ductal adenocarcinoma established from a N-nitrosobis(2-oxopropyl)amine-induced tumor and a poorly differentiated ductal adenocarcinoma established from a spontaneous tumor. An altered mobility indicated a conformational change in the first part of exon 5 in the solid form of the well-differentiated ductal adenocarcinoma. Direct sequencing of the amplified product revealed an A-->C transversion in codon 135, which corresponds to codon 132 in the human p53 gene. A conformational change in exon 7 was observed in 1 of 6 MNU-treated cell samples, and none of the 17 resultant tumors. Direct sequencing confirmed a deletion of one C of the three in codon 263, which generates a frameshift mutation. No conformational change was observed in any other products. Positive staining with PAb240 or DO7 antibodies against human p53 or with an antibody generated in our laboratory against the hamster p53 fusion protein was observed only in the solid form of well-differentiated ductal adenocarcinoma and in rare cells scattered in 4 of 28 MNU-induced tumors analyzed. This study provides a system to analyze p53 gene alterations in the hamster and is the initial report of a specific p53 mutation in a hamster pancreatic ductal adenocarcinoma.

Progesterone induction of mammary carcinomas in BALB/c female mice. Correlation between progestin dependence and morphology

We have demonstrated that medroxyprogesterone acetate (MPA), when administered in high doses, induces mammary carcinomas in virgin female BALB/c mice. Since one of the possible explanations for this effect was its progestagenic effects, we decided to investigate whether progesterone (Pg) alone could also induce mammary adenocarcinomas in our model and if MPA at doses lower than those used to establish the model was also carcinogenic. A total of 136 mice were subdivided into 3 groups: Group 1, 44 mice were implanted s.c. with 40 mg Pg silastic pellets at the beginning of the experiment, and 6 months later with a 20 mg Pg pellet; Group 2, 45 mice were similarly treated with MPA pellets; Group 3, 47 mice were inoculated s.c. with 40 mg MPA every three months. At the end of 20 months, 9 animals had developed mammary tumors in Group 1, 18 in Group 2 and 34 in Group 3 (actuarial incidence = 28%, 58%, and 98%, respectively); tumor latency was similar in all groups: 46.2 +/- 13.1, 51.3 +/- 9.9, and 50.1 +/- 2.1 weeks, respectively. Seven (Group 1), 14 (Group 2), and 25 (Group 3) tumors were transplanted into syngeneic mice to determine progestin dependence. All tumors, except one from Group 1, were histologically characterized. In Group 1 (Pg 60 mg), 4 tumors (67%) were infiltrating lobular carcinomas and 2 were ductal carcinomas (33%). In Group 2 (MPA 60 mg), 2 tumors (14%) were lobular and 12 were ductal adenocarcinomas (86%) (Group 1 vs Group 2: p < 0.05), whereas in Group 3 (MPA 160 mg), 8 were lobular carcinomas (32%) and 17 were ductal carcinomas (68%). In syngeneic passages all lobular tumors behaved as progestin independent (PI) and ductal tumors as progestin dependent (PD). All ductal tumors, except one, expressed estrogen receptors (ER) and progesterone receptors (PR), whereas receptor expression was variable in lobular carcinomas. It can be concluded that Pg induces mostly lobular, PI mammary tumors in BALB/c female mice. The fact that most MPA-induced tumors are ductal and PD suggests that the two hormones use different carcinogenic pathways.

Recent results in animal models of pancreatic carcinoma: histogenesis of tumors

Animal models of carcinoma of the pancreas provide new information regarding the pathways for histogenesis of the tumors. Four models, induced by chemical carcinogens or transgenic methods, are reviewed briefly from this perspective. Recent reports indicate that carcinomas with a ductal phenotype can arise from transformed acinar cells in rodents. A transgenic mouse model provides evidence that anaplastic carcinomas and islet cell tumors may arise from primitive cells that express the elastase gene, yet retain the potential to differentiate as islet cells. In a nitrosamine-induced hamster model, ductal carcinomas appear to arise directly from ductal cells. Carcinomas in this model contained mutations in the c-K-ras oncogene that are similar to those reported in about 75 percent of human pancreatic carcinomas, whereas acinar cell carcinomas of rats lacked this mutation. The histologic type of a carcinoma may reflect the cell of origin, but this statement is not always true. Therefore, classification of tumors on the basis of phenotype rather than on the presumed cell of origin is recommended. Among the animal models, the carcinomas in hamster pancreas rank as most similar to human pancreatic ductal adenocarcinomas in regard to the phenotype of the tumors and the prevalence of the c-K-ras mutation.