Superficial bladder cancer is a major target for chemoprevention. Retinoids are important modulators of epithelial differentiation and proliferation and are effective in the treatment and prevention ...of several epithelial cancers. One class of compounds, the retinamides, is structurally similar to other retinoids but have the added feature of being potent apoptosis inducers. Among these, fenretinide (N-4-hydroxyphenylretinamide), or 4HPR, has promise for bladder cancer chemoprevention and is currently under Phase III study in this setting. In addition to 4HPR, there are several new structurally related phenylretinamides bearing hydroxyl, carboxyl, or methoxyl residues on carbons 2, 3, and 4 of the terminal phenylamine ring designated N-(2-hydroxyphenyl)retinamide, N-(3-hydroxyphenyl)retin amide, N-(2-carboxyphenyl)retin- amide, N-(3-carboxyphenyl)retin amide, N-(4-carboxy- phenyl)retinamide, and N-(4-methoxyphenyl)retinamide, respectively. The objective of this study was to compare the growth inhibitory and apoptotic effects of these phenylretinamides with 4HPR in human bladder transitional cell cancer-derived cell lines of varying histological grade (RT4, grade 1; UM-UC9 and UM-UC10, grade 3; and UM-UC14, grade 4) by cell counting, cell cycle fluorescence-activated cell sorter analysis and a dual stain apoptosis assay. All of the seven phenylretinamides reduced cell number, altered the cell cycle distribution, and induced apoptosis when administered at a concentration of 10 microM, which is within the pharmacologically achievable range. Although the relative potencies of the phenylretinamides varied depending on the cell line, N-(3-hydroxy phenyl)retin- amide was the most active with significantly greater growth inhibition than 4HPR in all of the four cell lines. These in vitro findings warrant further study of these novel phenylretinamides, which may have potential as preventive or therapeutic agents in transitional cell cancer.
7,12-Dimethylbenz(a)anthracene (DMBA) is a prototype carcinogen that induces a high yield of mammary tumors in rats after a single feeding. We investigated the induction and chemoprevention of DNA ...adducts in female Sprague Dawley rats receiving DMBA by gavage according to a variety of treatment schedules. The patterns of 32P-postlabeled DNA adducts in liver and mammary epithelial cells were similar to those produced by the in vitro reaction of metabolically activated DMBA with calf thymus DNA. There was a high and statistically significant correlation between dose of DMBA administered to rats (0, 0.6, 2.4, and 12 mg/kg body weight) and levels of DNA adducts in both types of cells. The regression lines relating DMBA doses to total DNA adduct levels were significantly divergent and crossed at 1.5 mg/kg body weight, indicating that, at lower doses, the formation of DNA adducts is more intense in target mammary cells, whereas at higher doses, DNA adduct levels are more elevated in liver cells, presumably due to the greater metabolic capacity of this organ. When the rats were sacrificed 7 days rather than 2 days after DMBA administration, DNA adduct levels were approximately halved in both liver and mammary cells. The observed patterns can be interpreted based on toxicokinetic factors, local and distant metabolism, removal of DNA adducts by excision repair, and cell proliferation rate. Of three chemopreventive agents given with the diet to rats treated with 12 mg of DMBA, 5,6-benzoflavone (1650 ppm) was the most effective, inhibiting DNA adduct formation in liver and mammary cells by 96.5 and 83.5%, respectively. Feeding of 1,2-dithiole-3-thione (600 ppm) inhibited this biomarker by 68.5 and 50.2%, whereas butyl hydroxyanisole (BHA; 5000 ppm) showed a significant inhibition in the liver (46.5%) but was ineffective in mammary cells (29.0%, not significant). These data correlate nicely with the results of a parallel study in which 5,6-benzoflavone, 1,2-dithiole-3-thione, and BHA inhibited formation of hemoglobin adducts by 80.0, 44.0, and 0%, respectively; the incidence of mammary tumors by 82.4, 47.1, and 5.9%, respectively; and their multiplicity by 92.6, 80.0, and 7.4%, respectively. Therefore, biomarkers of biologically effective dose are highly predictive of the efficacy of chemopreventive agents in the DMBA rat mammary model. The selective inhibition by BHA of DNA adducts in the liver but not in mammary cells is consistent with the finding that this phenolic antioxidant stimulated phase II activities in the liver but not in the mammary gland (L. L. Song et al., manuscript in preparation). In any case, the broad-spectrum inducer 5,6-BF appears to be more effective than the two monofunctional phase II inducers, presumably because an enhanced activation of DMBA to reactive metabolites is coordinated with their blocking, detoxification, and excretion.
Fenretinide (4-HPR) is a retinoid analogue with antitumor and chemopreventive activities. In addition to 4-HPR, there are several other new phenylretinamides bearing hydroxyl, carboxyl, or methoxyl ...residues on carbons 2, 3, and 4 of the terminal phenylamine ring N-(2-hydroxyphenyl)retinamide (2-HPR), N-(3-hydroxyphenyl)retinamide, N-(2-carboxyphenyl)retinamide, N-(3-carboxyphenyl)retinamide, N-(4-carboxyphenyl)retinamide, and N-(4-methoxyphenyl)retinamide (4-MPR) . It is hypothesized that these agents can act independent of the nuclear retinoid receptor pathway. To test this hypothesis directly, we have analyzed the activity of these phenylretinamides in vitro on a panel of F9 murine embryonal carcinoma cell lines, which includes wild-type (F9-WT) and mutant cells that have disrupted genes for both retinoid X receptor alpha and retinoic acid receptor gamma retinoid receptors (F9-KO). The F9-KO cells lack almost all measurable response to all-trans-retinoic acid, the primary biologically active retinoid. Two distinct effects of retinamides were identified. The first is a rapid, dose-dependent induction of cell growth inhibition (reduced cell viability), and the second is a slower induction of differentiation and accumulation of cells in the G(1) phase of the cell cycle that was observed with a concentration of 1 micro M, for only those phenylretinamides bearing charged (hydroxyl or carboxyl) groups on the terminal phenylamine ring. The induction of differentiation and G(1) accumulation was only observed in the F9-WT cells, indicating that this effect is receptor-dependent. 4-MPR, a major metabolite of 4-HPR, lacks a charged group on the terminal phenylamine ring and did not induce retinoid receptor-dependent effects, but did induce cell growth inhibition. Thus, 4-MPR may play a role in the clinical activity of 4-HPR. This study further reveals the mechanism of action of these novel phenylretinamides and supports continued investigation into their development as chemopreventive drugs.
Women with germline mutations in the breast cancer susceptibility gene BRCA1 are at an increased risk of developing breast cancer. The synthetic retinoid N-(4-hydroxyphenyl)retinamide (4-HPR) has ...been shown to have a clinical chemopreventive activity in patients with premenopausal breast cancer. Since BRCA1 mutations are associated with an early-onset breast cancer, usually before menopause, we hypothesized that 4-HPR may be an effective chemopreventive agent against breast tumors exhibiting BRCA1 mutations. The objective of this study was to determine the effectiveness and mechanisms of action of 4-HPR and its phenylretinamide analogues in BRCA1-mutated breast cancer cells. At clinically relevant doses, 4-HPR induced apoptosis in human (HCC1937) and murine (W0069, W525) BRCA1-mutated breast cancer cells. Among the various phenylretinamides tested, N-(2-carboxyphenyl)retinamide (2-CPR) and 3-CPR significantly inhibited the growth of HCC1937 cells; however, they were not as potent as 4-HPR in this respect. We also determined the mechanisms by which 4-HPR induces apoptosis in BRCA1-mutated breast cancer cells. The extent to which 4-HPR induced apoptosis in BRCA1-mutated cells correlated with the increases in nitric oxide (NO) production and nitric oxide synthase (NOS) II and NOSIII expression. Use of a NOS inhibitor to block NO production suppressed the inhibitory effects of 4-HPR in all cell lines. These in vitro results suggest that 4-HPR may be an effective chemopreventive agent against breast tumors that exhibit BRCA1 mutations because of its ability to induce NO-mediated apoptosis in such tumors.
In this study, feeding Western-style diets (WDs) to mice for a duration of two years without any chemical carcinogen led to the development of gross colonic lesions that were histologically ...classified as dysplastic crypts and focal hyperplasias with or without atypical nuclei. To better understand early biological events contributing to the development of colonic neoplasia, grossly normal colonic mucosa was investigated; mitotic and apoptotic colonic epithelial cells, atypical mitosis, and atypical nuclei were studied. A significant and transient increase of mitotic activity in the basal and intermediate portions of the colonic crypts was seen in young mice after feeding them the WDs. This was accompanied by diffuse activation of apoptosis of the colonic epithelial cells. In the middle of the rodents' life span, after administration of both the WDs and control diet, the rodents developed a marked depletion of apoptotic epithelial cells in the mid-region of the colonic crypts; this was followed by the expansion of an epithelial cell population containing atypical nuclei, and the emergence of the gross lesions noted above. With this sequence of events, prolonged feeding of WDs to mice produced single-crypt dysplastic lesions and focal hyperplasias indicative of tumorigenesis.
The proceedings of a workshop focusing on a project to evaluate the use of fluorodeoxyglucose-positron emission tomography (FDG-PET) as a tool to measure treatment response in non-Hodgkin lymphoma ...(NHL) are described. Sponsored by the Leukemia & Lymphoma Society, the Foundation of the National Institutes of Health, and the National Cancer Institute, and attended by representatives of the Food and Drug Administration, the Centers for Medicare and Medicaid Services, and scientists and clinical researchers from academia and the pharmaceutical and medical imaging industries, the workshop reviewed the etiology and current standards of care for NHL and proposed the development of a clinical trial to validate FDG-PET imaging techniques as a predictive biomarker for cancer therapy response. As organized under the auspices of the Oncology Biomarker Qualification Initiative, the three federal health agencies and their private sector and nonprofit/advocacy group partners believe that FDG-PET not only demonstrates the potential to be used for the diagnosis and staging of many cancers but in particular can provide an early indication of therapeutic response that is well correlated with clinical outcomes for chemotherapy for this common form of lymphoma. The development of standardized criteria for FDG-PET imaging and establishment of procedures for transmission, storage, quality assurance, and analysis of PET images afforded by this demonstration project could streamline clinical trials of new treatments for more intractable forms of lymphoma and other cancers and, hence, accelerate new drug approvals.
The influence of chemical carcinogen, hormonal stimulation, and chronic dietary administration of the synthetic retinoid, N-(4-hydroxyphenyl)-all-trans-retinamide (4-HPR), on the induction of ...prostate cancer in male Wistar-Unilever rats was determined. Three different tumor induction regimens were used: (a) a single i.v. dose of 50 mg of N-methyl-N-nitrosourea (MNU) per kg body weight, followed by chronic androgen stimulation via s.c. implantation of two silastic capsules containing 40 mg testosterone each; (b) a single i.v. dose of 50 mg of MNU per kg body weight (no testosterone treatment); and (c) chronic androgen stimulation with implanted testosterone capsules (no MNU treatment). In a fourth series of animals, the incidence of spontaneous prostate tumors was determined in groups of rats receiving neither carcinogen nor hormone stimulation. Within each series, parallel groups of animals were fed a control (vehicle-supplemented) diet or control diet supplemented with 4-HPR beginning 1 day after carcinogen administration; retinoid administration was continuous until termination of the study at 450 days. The incidence of accessory sex gland cancer in rats treated sequentially with MNU + testosterone was >60%, in comparison with cancer incidences of <20% in rats receiving MNU only and <5% in rats treated with testosterone only. No spontaneous accessory sex gland tumors were observed in rats receiving no carcinogen and no testosterone. Tumor induction in the accessory sex glands by MNU + testosterone was relatively specific for the prostate: the incidence of carcinoma of the dorsolateral/anterior prostate was more than 5-fold greater than the incidence of cancer present only in the seminal vesicle. 4-HPR conferred no protection against cancer induction in the prostate by any regimen of MNU and/or testosterone. These results demonstrate the importance of both carcinogen exposure and hormone stimulation on the induction of neoplasia in the prostate of Wistar-Unilever rats.
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) α, β and γ and 9-cis-retinoic acid receptors α, β and γ, 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–RARα 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.
Quantitative imaging biomarkers could speed the development of new treatments for unmet medical needs and improve routine clinical care. However, it is not clear how the various regulatory and ...nonregulatory (eg, reimbursement) processes (often referred to as pathways) relate, nor is it clear which data need to be collected to support these different pathways most efficiently, given the time- and cost-intensive nature of doing so. The purpose of this article is to describe current thinking regarding these pathways emerging from diverse stakeholders interested and active in the definition, validation, and qualification of quantitative imaging biomarkers and to propose processes to facilitate the development and use of quantitative imaging biomarkers. A flexible framework is described that may be adapted for each imaging application, providing mechanisms that can be used to develop, assess, and evaluate relevant biomarkers. From this framework, processes can be mapped that would be applicable to both imaging product development and to quantitative imaging biomarker development aimed at increasing the effectiveness and availability of quantitative imaging.
http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.10100800/-/DC1.
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