Chemoprevention Trial of Contralateral Breast Cancer with Fenretinide. Rationale, Design, Methodology, Organization, Data Management, Statistics and Accrual

Plasma Testosterone and Prognosis of Postmenopausal Breast Cancer Patients

Purpose

High endogenous testosterone is associated with increased breast cancer (BC) risk. We designed this study specifically to assess the long-term prognostic role of testosterone in a cohort of postmenopausal BC patients.

Patients and Methods

We considered 194 postmenopausal women, operated on for early BC (T1-2N0M0), who never received chemotherapy or hormonal therapy, and who participated in a fenretinide BC prevention trial as untreated controls. Blood samples were collected 3 months (median) after surgery; plasma samples, stored at −80°C, were radioimmunoassayed for testosterone. Median follow-up was 14 years. The main end point was any cancer event. Event-free survival was estimated by the Kaplan-Meier method. Hazard ratios (HRs) of events by testosterone level were estimated by the Cox model, adjusting for age, tumor size, and histology.

Results

Patients with high testosterone (≥ 0.40 ng/mL, median of distribution) had significantly lower event-free survival than those with low testosterone (log-rank P = .004). The adjusted HR of patients with high versus low testosterone was 2.05 (95% CI, 1.28 to 3.27). High testosterone was also associated with a significantly higher risk of BC events (relapse and second primary) with an adjusted HR of 1.77 (95% CI, 1.06 to 2.96). Eleven second primaries (non-BC) occurred in the high-testosterone group, four in the low-testosterone group.

Conclusion

High plasma testosterone strongly predicts poorer prognosis in postmenopausal BC patients not administered adjuvant therapy. Testosterone levels should be determined as part of the prognostic work-up.

Anti-proliferative activity of fenretinide in human hepatoma cells in vitro and in vivo

N-(4-hydroxyphenyl)-retinamide (fenretinide) is a synthetic derivative of all-trans-retinoic acid and induces apoptosis in several cancer cell lines. We determined the anti-cancer activity of fenretinide using human hepatoma cell lines, Bel-7402, HepG2 and Smmc-7721. An in-vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that fenretinide exhibited growth inhibition in these cell lines, with IC50 values ranging from 13.1 to 15.5 micromol/l. In Bel-7402 cells, apoptosis with 15 micromol/l fenretinide for 0 and 48 h was 3 and 48%, respectively. In-vivo studies using the Bel-7402 xenografted athymic mouse model showed tumor inhibition rates ranging from 37.2 to 57.2%, with fenretinide administration once per 3 days at the rate of 25-100 mg/kg. Western blot analysis further showed down-regulation of procaspase-3, X-linked inhibitor of apoptosis protein and poly(ADP-ribose) polymerase cleavage in Bel-7402 cells treated with 15 mumol/l fenretinide for 48 h. Overexpression of p53 was observed in a time-dependent manner, along with a decrease in the Bcl-2/Bax ratio. Depolarized mitochondrial membranes were found in fenretinide-induced apoptotic cells, in a time-dependent manner. We conclude that fenretinide effectively inhibits the proliferation of Bel-7402, both in vitro and in vivo. Both procaspase-3 and p53-mediated apoptotic pathways are involved in its potent anti-cancer activity.

Fifteen-year results of a randomized phase III trial of fenretinide to prevent second breast cancer

PURPOSE

The synthetic retinoid fenretinide administered for 5 years for prevention of second breast cancer showed no difference after a median of 8 years, but a possible reduction in premenopausal women. We conducted a long-term analysis in a subgroup of women who were regularly followed up in a single center.

PATIENTS AND METHODS

We analyzed data after a median follow-up of 14.6 years (IQ range, 12.3-16.3 years) from 1739 women aged 30-70 (872 in the fenretinide arm and 867 in the observation arm), representing 60% of the initial cohort of 2867 women. The main efficacy endpoint was second primary breast cancer (contralateral or ipsilateral).

RESULTS

The number of second breast cancers was 168 in the fenretinide arm and 190 in the control arm (hazard ratio = 0.83, 95% CI, 0.67-1.03). There were 83 events in the fenretinide arm and 126 in the observation arm in premenopausal women (HR = 0.62, 95% CI, 0.46-0.83), and 85 and 64 events in postmenopausal women (HR = 1.23, 95% CI, 0.63-2.40). The younger were the women, the greater was the risk reduction associated with fenretinide, which attained 50% in women aged 40 years or younger and disappeared after age 55 (P-age*treatment interaction = 0.023). There was no difference in cancers in other organs, distant metastases or survival.

CONCLUSIONS

Fenretinide induces a significant risk reduction of second breast cancer in premenopausal women, which is remarkable at younger ages, and persists several years after treatment cessation. Since adverse events are limited, a trial in young women at high-risk is warranted.

Induction of apoptosis in primary meningioma cultures by fenretinide

Fenretinide, a synthetic retinoid that induces apoptosis in tumor cells in vitro, is being evaluated in clinical trials as a chemotherapeutic agent against several malignancies. Due to its ease of administration, long-term tolerability, and low incidence of long-term side effects, we explored its potential as a therapeutic agent against meningiomas by examining its efficacy in vitro against such cells in primary culture. Cells, cultured from freshly resected benign, atypical, or malignant meningiomas, were exposed to fenretinide (10 mumol/L). Treatment effects were assessed using flow cytometry, Western blot analysis, semiquantitative reverse transcription-PCR for retinoid receptor expression, and changes in insulin-like growth factor-I (IGF-I)-induced proliferation. Fenretinide induced apoptosis in the three grades of meningioma primary cells tested, as shown by the appearance of a sub-G(1) fraction in flow cytometric analysis and by the detection of poly-adenosyl ribonucleotidyl phosphorylase cleavage indicating caspase activation. Fenretinide treatment also increased levels of the death receptor DR5 and caused mitochondrial membrane depolarization. The levels of the retinoid receptors, retinoic acid receptor alpha and retinoid X receptor gamma, were up-regulated in response to fenretinide, suggestive of ligand-induced receptor up-regulation. IGF-I-induced proliferation in the meningioma cells was abolished by fenretinide. We conclude that fenretinide induces apoptosis in all three histologic subtypes of meningioma and exerts diverse cellular effects, including DR5 up-regulation, modulation of retinoid receptor levels, and inhibition of IGF-I-induced proliferation. These results provide preliminary evidence that fenretinide has activity against meningiomas and suggest that further studies are warranted to explore its potential as a therapeutic agent against meningiomas.

Phase II study of fenretinide (NSC 374551) in adults with recurrent malignant gliomas: A North American Brain Tumor Consortium study

PURPOSE

Fenretinide induces apoptosis in malignant gliomas in vitro. This two-stage phase II trial was conducted to determine the efficacy of fenretinide in adults with recurrent malignant gliomas.

PATIENTS AND METHODS

Twenty-two patients with anaplastic gliomas (AG) and 23 patients with glioblastoma (GBM) whose tumors had recurred after radiotherapy and no more than two chemotherapy regimens were enrolled. Fenretinide was given orally on days 1 to 7 and 22 to 28 in 6-week cycles in doses of 600 or 900 mg/m(2) bid.

RESULTS

Six of 21 (29%) patients in the AG arm and two of 23 (9%) patients in the GBM arm had stable disease at 6 months. One patient with AG treated at 900 mg/m(2) bid dosage had a partial radiologic response. Median progression-free survival (PFS) was 6 weeks for the AG arm and 6 weeks for the GBM arm. PFS at 6 months was 10% for the AG arm and 0% for the GBM arm. Grade 1 or 2 fatigue, dryness of skin, anemia, and hypoalbuminemia were the most frequent toxicities reported. The trial was closed after the first stage because of the inadequate activity at the fenretinide doses used. The first-administration mean plasma C(max) for fenretinide was 832 +/- 360 ng/mL at the 600 mg/m(2) bid dosage and 1,213 +/- 261 ng/mL at the 900 mg/m(2) bid dosage.

CONCLUSION

Fenretinide was inactive against recurrent malignant gliomas at the dosage used in this trial. However, additional studies using higher doses of the agent are warranted based on the tolerability of the agent and the potential for activity of a higher fenretinide dosage, as suggested in this trial.

Ovarian cancer and high-risk women—implications for prevention, screening, and early detection

OBJECTIVE

The aim of this study was to understand the strengths and limitations of current prevention, detection, and screening methods for ovarian cancer and to identify research areas to improve prevention, screening, and detection of the disease for all women as well as for women carrying a mutation in the BRCA1/2 genes.

METHODS

We convened an ovarian cancer symposium at the University of Pittsburgh in May 2002. Nineteen leading scientists representing disciplines such as epidemiology, molecular biology, pathology, genetics, bioinformatics, and psychology presented the latest data on ovarian cancer prevention, screening, and early detection.

RESULTS

Ovarian cancer is the most common cause of death from a gynecologic malignancy in the United States. Because survival depends on stage of diagnosis, early detection is critical in improving clinical outcome. However, existing screening techniques (CA125, transvaginal ultrasound) have not been shown to reduce morbidity or mortality. Moreover, with the exception of oral contraceptives, there are no available chemopreventive agents. Bilateral salpingo-oophorectomy also has been shown to reduce incidence, but this procedure has several drawbacks in terms of a woman's reproductive, cardiovascular, skeletal, and mental health.

CONCLUSIONS

Better methods to prevent, detect, and screen for ovarian cancer in all women, but particularly in high-risk women carrying mutations in BRCA1/2, are urgently needed. This article reviews the current state of knowledge in the etiology, prevention, and early detection of ovarian cancer and suggests several areas for future clinical, epidemiologic, and laboratory-based research.

Retinoic acid signaling through PI 3-kinase induces differentiation of human endometrial adenocarcinoma cells

The specific signals required for actin polymerization in response to extracellular factors remain unknown. However, in many cell types, there is a correlation between actin polymerization, activation of phosphatidylinositol 3-kinase (PI 3-kinase), and the production of the second messenger phosphatidylinositol-3,4,5-triphosphate. Increased levels of PI 3-kinase have been detected during cell growth and transformation. However, PI 3-kinase is also activated during differentiation, suggesting that PI 3-kinase and its lipid products also play a role in the regulation of cellular differentiation. The newly characterized CAC-1 cell line established from a poorly differentiated human endometrial adenocarcinoma (Exp. Mol. Pathol. 69 (2000), 175) was used as a model to investigate the role of PI 3-kinase in differentiation induction. CAC-1 cells differentiated upon treatment with pharmacological doses of retinoids (1 micro M of 13-cis or all-trans), evidenced by actin filament reorganization, and cell enlargement. PI 3-kinase staining is primarily localized to perinuclear regions in untreated cells. However, retinoic acid treatment induced PI 3-kinase to relocalize throughout the cytoplasm. Subcellular fractionation and Western blotting confirmed that PI 3-kinase decreased in the particulate fraction, concurrent with retinoid-induced differentiation. Interestingly, pretreatment with the PI 3-kinase inhibitor wortmannin (100 nM) prior to retinoic acid treatment prevented retinoic acid-induced actin reorganization and cell enlargement. To distinuish whether retinoid regulation of PI 3-kinase is mediated through traditional nuclear retinoic acid receptors, the levels of retinoic acid receptor-beta (RAR-beta) protein were evaluated. Retinoid treatment did not alter RAR-beta protein levels compared to controls. These data suggest that PI 3-kinase activity and cytoplasmic relocalization are required for retinoid-induced differentiation of poorly differentiated human endometrial adenocarcinoma cells.

[Can breast cancer be chemoprevented in 2003?]

Breast cancer is certainly not preventable at the same degree as lung cancer is by avoiding cigarette smoking or bladder cancer by avoiding exposure to some specific professional carcinogens. Despite the increased availability of screening mammography and the use of adjuvant chemotherapy, breast cancer remains a major cause of morbidity and mortality in women. Chemoprevention could be one of the possible weapons to decrease the morbidity and the mortality due to breast cancer. Experimental, epidemiological and clinical data suggest that one can prevent occurrence of breast cancer. The results of five trials including more than 25,000 patients comparing the effectiveness of tamoxifen with a placebo were published. The results of these trials, at first sight, do not agree. Only in the USA, the results of the five trials have led to licence tamoxifen for chemoprevention of breast cancer. But the Food and Drug Administration stresses the fact that the noxious side effects are too numerous for this molecule to be prescribed with all the patients. It must be reserved for the women presenting an increased risk. The means of identifying the women at increased risk are not yet perfect.

Adolescent vitamin A intake alters susceptibility to mammary carcinogenesis in the Sprague-Dawley rat

We tested the hypothesis that adolescent dietary vitamin A intake impacts mammary gland development and subsequent sensitivity to carcinogenesis. Sprague-Dawley rats were fed a purified diet that was vitamin A deficient, adequate (2.2 mg retinyl palmitate/kg diet), or supranutritional (16 mg retinyl palmitate/kg diet) from 21 to 63 days of age, the period of adolescent mammary gland development. At 73 days of age, rats were given 1-methyl-1-nitrosourea (25 mg/kg body wt i.p.) and monitored for mammary tumors. Tumors appeared earlier and more frequently in rats fed vitamin A-deficient or -supplemented diets. Vitamin A deficiency during adolescence was associated with alveolar mammary gland development and precocious milk protein expression, while supplementation was associated with ductal gland development and suppression of milk protein expression. Differences in circulating estradiol and mammary gland estrogen receptor-alpha, and estrogen-responsive progesterone receptor mRNA were not observed, suggesting that the effects of vitamin A on mammary gland development and carcinogenesis are estrogen independent. Mammary expression of another hormone receptor that regulates milk protein expression, the glucocorticoid receptor, was also unaffected. These results demonstrate that vitamin A intake during adolescence alters mammary gland differentiation and indicate that a narrow range of vitamin A intake during adolescence protects against carcinogenesis.

Effect of fenretinide on ovarian carcinoma occurrence

OBJECTIVE

The aim of this study was to update the effect of fenretinide, a synthetic vitamin A analogue proposed for chemoprevention, on the occurrence of ovarian carcinoma.

METHODS

Data were obtained from a randomized clinical trial for the prevention of second breast cancer. For the present investigation, events of interest were new primary carcinomas of the ovary arising in the fenretinide or the no-treatment (control) arm. The probability of carrying a BRCA germ-line mutation was assessed in women with ovarian carcinoma according to G. Parmigiani et al. (1998, Am J Hum Genet 62, 145-58).

RESULTS

Fenretinide reduced ovarian carcinoma occurrence during the 5-year intervention period (0 versus 6 cases in the fenretinide and control arm, P = 0.0327). This effect was no longer evident after the 5-year intervention period (6 versus 4 cases, P = 0.7563). Therefore with median observation time of 121 months, a total of 6 carcinomas of the ovary occurred in the fenretinide group and 10 in the control group. The probability of carrying a BRCA mutation was lower for women with ovarian carcinoma in the treatment arm.

CONCLUSION

Fenretinide treatment was associated with a lower incidence of ovarian carcinoma during the intervention period but such a protective effect seems to disappear after treatment. Furthermore, a possible protective effect of fenretinide in BRCA-mutated women was suggested. Further studies on fenretinide for the prevention of ovarian carcinoma particularly in women with genetic susceptibility appear necessary.

Chemoprevention of breast cancer with fenretinide

Chemoprevention of cancer represents a challenge for oncology during this new millennium. Substantial advances have been accomplished in the last decade, especially for primary and secondary prevention of breast cancer. In addition to tamoxifen, raloxifene and other selective estrogen receptor modulators, retinoids are among the most promising agents, given their ability to inhibit mammary carcinogenesis in preclinical models. Fenretinide, the synthetic amide of retinoic acid, inhibits cell growth mostly through the induction of apoptosis with mechanisms which may partly involve the retinoid receptors. Because it has a favourable toxicological profile, fenretinide has been extensively investigated in clinical trials. A large randomised phase III trial for secondary breast cancer prevention has been recently carried out in Italy. Results showed a reduction of second breast malignancies in premenopausal women. In addition, a significant decrease of circulating insulin-like growth factor (IGF)-1, a known risk factor for premenopausal breast cancer, was observed after 1 year of fenretinide administration in premenopausal women with breast cancer. Ongoing studies on the validation of the circulating IGF-1 as a surrogate endpoint biomarker of fenretinide activity and on the effectiveness of the combination with low dose tamoxifen may provide further insight into the future clinical application of fenretinide.

Safety of the synthetic retinoid fenretinide: long-term results from a controlled clinical trial for the prevention of contralateral breast cancer

PURPOSE

To describe the pattern of occurrence of adverse events commonly arising during treatment with fenretinide, a synthetic retinoid under investigation for cancer prevention.

PATIENTS AND METHODS

The series includes 2,867 women accrued in a trial aimed at assessing the effect of fenretinide on the prevention of second breast malignancy. Women were randomly assigned to receive no treatment (1,435 patients) or 5-year fenretinide treatment (1,432 patients). In terms of disease recurrence in the breast, the trial showed a possible beneficial effect of the compound in premenopausal women, and an opposite trend in postmenopausal women. End points considered for safety assessment were the occurrence of diminished dark adaptation, dermatologic disorders, gastrointestinal symptoms, disorders of the ocular surface, and abnormal laboratory values.

RESULTS

The most common adverse events were diminished dark adaptation (cumulative incidence, 19.0%) and dermatologic disorders (18.6%). Less common events were gastrointestinal symptoms (13.0%) and disorders of the ocular surface (10.9%). In comparison, incidence figures in the control arm were 2.9% for diminished dark adaptation, 2.9% for dermatologic disorders, 5.4% for gastrointestinal symptoms, and 3.2% for disorders of the ocular surface. Symptoms occurring during fenretinide treatment tended to recover with time. No between-group difference was observed for the occurrence of laboratory data abnormalities. Overall, 63 (4.4%) treatment discontinuations were caused by adverse events.

CONCLUSION

Given the number of patients involved in the study and the prolonged intake of the drug, the experience on fenretinide tolerability can be considered sufficiently reassuring to justify further testing of the retinoid.

Suppression of pRB expression in normal human mammary epithelial cells is associated with resistance to all-trans-retinoic acid but not N-(4-hydroxylphenyl)-retinamide

Despite the widespread clinical use of synthetic and naturally occurring retinoids, the down stream targets of retinoids have not been fully characterized. We observe that G(1/0)-phase arrest induced by all-trans-retinoic acid (ATRA) in normal human mammary epithelial cells (HMECs) is temporally associated with a significant decrease in the levels of hyperphosphorylated retinoblastoma protein (pRB). Suppression of pRB protein expression in HMECs by retroviral-mediated expression of the E7 protein of the human papillomavirus strain 16 (HPV-16) was associated with resistance to ATRA-mediated growth arrest but not to the synthetic retinoid N-(4-hydroxyphenyl) retinamide (4-HPR or fenretinide). 4-HPR but not ATRA induced apoptosis in HMECs independent of the level of pRB protein expression. These observations suggest that ATRA- but not 4-HPR-mediated growth arrest may be dependent on the coordinated expression of pRB and emphasize the chemotherapeutic potential of 4-HPR, particularly for suppressing growth of tumors lacking pRB function.

Transforming growth factors-beta are not good biomarkers of chemopreventive efficacy in a preclinical breast cancer model system

Using a carcinogen-initiated rat model of mammary tumorigenesis, we tested the hypothesis that transforming growth factor (TGF)-betas are useful biomarkers of chemopreventive efficacy in the breast. The chemopreventive agents tested were tamoxifen and the retinoids 9-cis-retinoic acid (9cRA) and N-(4-hydroxyphenyl)retinamide (4-HPR), because both antiestrogens and retinoids have previously been shown to upregulate TGF-betas in vitro. Despite demonstrable chemopreventive efficacy in this model, none of these agents, alone or in combination, had any significant impact on the expression of TGF-betas in the mammary ductal epithelium or periductal stroma as determined by immunohistochemistry. These data suggest that TGF-betas are not likely to be useful biomarkers of chemopreventive efficacy in a clinical setting.

Retinoids in chemoprevention and differentiation therapy

Retinoids are essential for the maintenance of epithelial differentiation. As such, they play a fundamental role in chemoprevention of epithelial carcinogenesis and in differentiation therapy. Physiological retinoic acid is obtained through two oxidation steps from dietary retinol, i.e. retinol-->retinal-->retinoic acid. The latter retinal-->retinoic acid step is irreversible and eventually marks disposal of this essential nutrient, through cytochrome P450-dependent oxidative steps. Mutant mice deficient in aryl hydrocarbon receptor (AHR) accumulate retinyl palmitate, retinol and retinoic acid. This suggests a direct connection between the AHR and retinoid homeostasis. Retinoids control gene expression through the nuclear retinoic acid receptors (RARs) alpha, beta and gamma and 9-cis-retinoic acid receptors alpha, beta and gamma, which bind with high affinity the natural ligands all-trans-retinoic acid and 9-cis-retinoic acid, respectively. Retinoids are effective chemopreventive agents against skin, head and neck, breast, liver and other forms of cancer. Differentiation therapy of acute promyelocytic leukemia (APL) is based on the ability of retinoic acid to induce differentiation of leukemic promyelocytes. Patients with relapsed, retinoid-resistant APL are now being treated with arsenic oxide, which results in apoptosis of the leukemic cells. Interestingly, induction of differentiation in promyelocytes and consequent remission of APL following retinoid therapy depends on expression of a chimeric PML-RAR alpha fusion protein resulting from a t(15;17) chromosomal translocation. This protein functions as a dominant negative against the function of both PML and RARs and its overexpression is able to recreate the phenotypes of the disease in transgenic mice. The development of new, more effective and less toxic retinoids, alone or in combination with other drugs, may provide additional avenues for cancer chemoprevention and differentiation therapy.

Chemoprevention of breast cancer: the Italian experience

The activity of our group is focused on the conduction of chemoprevention clinical trials of breast cancer in at-risk subjects, among which we include women on hormone replacement therapy (HRT). The role of the insulin-like growth factor (IGF) system and of mammographic breast density as surrogate biomarkers for breast cancer prevention is also being investigated. The IGF system is involved in human carcinogenesis of several solid tumors. IGF-I is a potent mitogen for breast cancer cells; elevated circulating IGF-I levels have been associated with a higher risk of premenopausal breast cancer, prostate and colorectal cancer in prospective studies. Both tamoxifen and the synthetic retinoid fenretinide (4-HPR) have been shown to decrease plasma IGF-I levels. A trial of their combination is ongoing in premenopausal women with increased risk for breast cancer. Mammographic breast density has also been associated with an increased risk of breast cancer in several prospective studies. In this article, we discuss the rationale for selection of appropriate cohorts, candidate agents, and putative surrogate biomarkers in our breast cancer prevention trials. Moreover, updated results of the secondary prevention trial of 4-H PR and of the primary prevention trial of tamoxifen are presented. Finally, the rationale for a reduction of tamoxifen dose in future prevention trials is provided.

Prevention of breast cancer

With the advent of screening and the increased incidence of breast cancer, concern for the prevention of breast cancer has become forefront in today's society. Determining individual risk is the key to prescribing prevention. Prevention of breast cancer is still under clinical investigation with only one drug, tamoxifen, showing benefit in high risk patients. This paper reviews the possible sites for prevention of neoplastic transformation via biomarkers in a breast cell as well as the investigational drugs and their potential use in the chemoprevention of breast cancer.

Chemoprevention of breast cancer in the older patient

Age is the most important risk factor for the development of breast cancer. The risk of breast cancer continues to increase in American women until the age of 80 years. A family history of breast cancer helps identify those who possibly have the highest risk of developing breast cancer; however, most women who develop breast cancer do not have a first-degree relative with a history of breast cancer. Currently, the Gail model is a commonly used model to identify risk, and this model has now been validated in several populations of women undergoing screening for breast cancer. The first large-scale breast cancer prevention trial investigating the preventive effects of tamoxifen has demonstrated a decrease in the development of breast cancer by almost 50% in the women in the tamoxifen treatment arm as compared with those receiving placebo. The NSABP P-1 trial was the largest of the three tamoxifen breast cancer prevention trials and had the greatest power to detect a difference between the two treatment groups in breast cancer events. This trial also included the largest percentage of postmenopausal women. It is unclear why the Italian and Royal Marsden Hospital trials had negative results regarding the preventive effects of tamoxifen. These two trials were strikingly different from the NSABP P-1 trial, however, and they included a different population of women. The issues surrounding the use of HRT for treatment of hot flashes in the Italian and Royal Marsden Hospital trials adds to the controversy concerning the negative results of these trials. The new SERM, raloxifene, has shown promise in preliminary studies as a preventive agent for breast cancer. The STAR trial will open soon and will evaluate the efficacy of raloxifene in preventing breast cancer in a prospective fashion, comparing its efficacy with tamoxifen treatment. Other endpoints will evaluate side effects such as menopausal symptoms, endometrial cancer, thromboembolic events, and benefits regarding serum lipids and incidence of osteoporotic bone fractures. The development of SERMs results from an understanding of novel mechanisms of ER modulation and allows targeting for favorable effects in specific tissues. The challenge is to develop an ideal SERM that is effective in preventing breast cancer and does not increase the risk of endometrial cancer, while providing beneficial estrogenic effects on serum lipids and bone mineral density changes. Estrogen receptor-mediated intracellular processes are complex. There are at least two different types of estrogen receptors. The alpha receptors predominate in the breast and uterus, and the beta receptors predominate in the bone and blood vessels. Many proteins also interact with these receptors as co-activators or co-repressors. Transcription-activating factors modulate the effects of estrogen on its target genes. Future prevention strategies may use a combined targeted approach to inhibit ER-mediated cancer progression pathways. The retinoids are under investigation in prevention studies for a multitude of cancers, because they have been shown to inhibit cellular proliferation and to induce cellular differentiation. The retinoid 4HPR was selected for use in breast cancer prevention studies because of its low toxicity profile and prevention efficacy in preclinical studies. It is now being used in combination with tamoxifin in a phase II breast cancer prevention trial. Multiple surrogate endpoint biomarkers are being measured before and after treatment, including measurement of serum IGF-I levels. Future directions in breast cancer prevention include the development of more potent hormonal therapies that completely inhibit ER-mediated cancer progression and, ultimately, multitargeted therapies involving agents that work synergistically.

Randomized trial of fenretinide to prevent second breast malignancy in women with early breast cancer

BACKGROUND

Fenretinide, a vitamin A analogue, has been shown to inhibit breast carcinogenesis in preclinical studies. We determined the efficacy of fenretinide in preventing a second breast malignancy in women with breast cancer.

METHODS

We randomly assigned 2972 women, aged 30-70 years, with surgically removed stage I breast cancer or ductal carcinoma in situ to receive for 5 years either fenretinide orally (200 mg/day) or no treatment. The primary end point was the incidence of contralateral breast cancer or ipsilateral breast cancer 7 years after randomization. Other end points considered post hoc were the same outcomes stratified by menopausal status, incidence of distant metastases, overall mortality, and tumors in other organs. The hazards of breast cancer occurrence were determined by Cox proportional hazards regression analysis. Statistical tests were two-sided.

RESULTS

At a median observation time of 97 months, there were no statistically significant differences in the occurrence of contralateral breast cancer (P =.642) or ipsilateral breast cancer (P =.177) between the two arms. However, an interaction was detected between fenretinide treatment and menopausal status in both outcomes (P for interaction in both outcomes =.045), with a possible beneficial effect in premenopausal women (contralateral breast cancer: adjusted hazard ratio [HR] = 0.66, and 95% confidence interval [CI] = 0.41-1.07; ipsilateral breast cancer: adjusted HR = 0.65, and 95% CI = 0.46-0. 92) and an opposite effect in postmenopausal women (contralateral breast cancer: adjusted HR = 1.32, and 95% CI = 0.82-2.15; ipsilateral breast cancer: adjusted HR = 1.19, and 95% CI = 0.75-1. 89). There were no statistically significant differences between the two arms in tumors in other organs, incidence of distant metastasis, and all-cause mortality.

CONCLUSIONS

Fenretinide treatment of women with breast cancer for 5 years appears to have no statistically significant effect on the incidence of second breast malignancies overall, although a possible benefit was detected in premenopausal women. These studies, particularly the post hoc analyses, are considered exploratory and need to be confirmed.

4HPR triggers apoptosis but not differentiation in retinoid sensitive and resistant human embryonal carcinoma cells through an RARgamma independent pathway

Retinoids signal biological effects through retinoic acid receptors (RAR) and retinoid X receptors (RXR) and their co-regulators. We previously reported that all-trans retinoic acid (RA) triggers terminal differentiation in the human embryonal carcinoma cell line NTERA-2 clone D1 (NT2/D1), through an RARgamma dependent pathway. RARgamma repression in NT2/D1-R1 cells accounts for RA resistance in this line. This report finds RARgamma repression is due to selective repression of RARgamma but not RARbeta transcription in NT2/D1-R1 cells. The repression is neither due to mutations in RARgamma nor its promoter containing the RA response element. Prior work was confirmed and extended by demonstrating that an RARgamma selective agonist preferentially signals differentiation of NT2/D1 cells, while RARalpha/beta, RARbeta, RXR agonists and an RAR pan-antagonist do not even when NT2/D1 cells are treated with these retinoids at 10 microM dosages. None of these examined retinoids induced differentiation of the RA resistant NT2/D1-R1 cells. In contrast, N-(4-hydroxyphenyl)retinamide (4HPR), a reported transcriptional activator of RARgamma was shown to potently induce growth inhibition and apoptosis in both NT2/D1 and NT2/D1-R1 cells. 4HPR-induced apoptosis was unaffected by co-treatment of both cell lines with equimolar RAR antagonist. Semi-quantitative reverse transcription-polymerase chain reaction (RT - PCR) assays of total RNA from 4HPR-treated NT2/D1 and NT2/D1-R1 cells did not reveal RARgamma induction. Since 4HPR signals in RA-resistant NT2/D1-R1 cells having an RARgamma transcriptional block, these results indicate that 4HPR triggers apoptosis but not differentiation through an RARgamma independent pathway. Taken together, these findings implicate a therapeutic role for 4HPR mediated apoptosis in germ cell tumors even when a maturation block is present.

Dysregulated expression of cyclin D1 in normal human mammary epithelial cells inhibits all-trans-retinoic acid-mediated G0/G1-phase arrest and differentiation in vitro

Overexpression of cyclin D1 protein is observed in the majority of breast cancers, suggesting that dysregulated expression of cyclin D1 might be a critical event in breast cancer carcinogenesis. We investigated whether retroviral-mediated expression of cyclin D1 might affect all-trans-retinoic acid (ATRA)-mediated growth inhibition and differentiation of normal cultured human mammary epithelial cells (HMECs). HMECs treated with 1.0 microM ATRA undergo irreversible growth inhibition starting at 24 h and complete G0/G1-phase arrest by Day 3. Cyclin D1 protein levels are observed to decrease in association with the initiation of growth arrest starting at 24 h and then increase by approximately 35% on Day 3. Concomitant with this observed increase in cyclin D1, HMECs undergo morphologic changes consistent with progression to a more differentiated phenotype, including an increase in cell size, increased cell spreading, increased tonofilaments, and accumulation of cytoplasmic vesicles containing lipid. Dysregulated expression of cyclin D1 in HMECs results in inhibition of G0/G1-phase arrest mediated by ATRA. In addition, HMECs expressing exogenous cyclin D1 are resistant to differentiation by ATRA. Our results suggest that coordinated expression of cyclin D1 may be critical for normal mammary epithelial cell homeostasis, and dysregulated expression of cyclin D1 might result in retinoid resistance and promote mammary carcinogenesis.