Search

Background and purpose: Frontotemporal lobar degeneration (FTLD) is a common cause of early-onset dementia. Given the role of cystatin C in brain neurodegeneration and neuroregeneration, the aim of this study was to determine whether the cystatin C gene ( CST3) was genetically associated with FTLD. Methods: Hundred and eighty-six FTLD patients and 457 controls underwent CST3 analysis by PCR and KspI enzyme digestion. Results: In FTLD patients negative for the presence of PGRN mutations, we found an over-representation of the CST3 haplotype B [odds ratio (OR = 1.619, P = 0.002)] and of AB/BB genotypes (OR = 1.704, P = 0.008) in FTLD patients. Conclusions: The present study indicated the CST3 B haplotype as a putative risk factor for FTLD in PGRN mutations negative patients. The reduced level of cystatin C, previously associated with the B haplotype, might represent the molecular factor responsible for the increased risk. Long-term depletion of neurotrophic factors, such as cystatin C and progranulin proteins, seem to be a common theme in FTLD: boosting the expression of such proteins might be a promising therapeutic strategy for FTLD. [ABSTRACT FROM AUTHOR]

Growing evidence advanced the idea that the soluble form of the receptor for advanced glycation end-products (sRAGE) might serve as a risk marker for several disorders including Alzheimer disease. We found a reduced level of circulating sRAGE in patients with mild cognitive impairment (MCI). The reduction of sRAGE in MCI, as well as the anticipation of the disease in patients with the lowest sRAGE levels (≤225 pg/ml), suggest a role of the RAGE axis in the pathogenesis of the disease. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: Sex steroid hormones are implicated in the cognitive processes of the adult brain. Among studies reporting a positive effect of estrogen replacement therapy (ERT) on cognition, the most consistent evidence is that it enhances verbal memory and visuospatial functions. In the present study we investigated the effect of ERT on cognition and on brain morphology in healthy postmenopausal women, taking into account the distinction in current and past ERT users. Methods: Participants were postmenopausal nondemented women recruited from the community: ERT users were 40 (23 current users, 17 past users), while never users were 43. Forty of recruited subjects gave consent to undergo 3D high resolution MRI (16 current users, 7 past users and 17 never users). Participants underwent MMSE and a battery of neuropsychological tests measuring memory, language, intelligence, attention and visuo-spatial abilities. Results: The past users group outperformed the never users in four tests: Token test, WCST categories, attentional matrices and Rey''s delayed list; the current users group outperformed the never users in the Rey''s list test. ERT users had greater grey matter volumes mainly in the cerebellum, but an increase was observed also in the parietal and occipital cortex. Conclusions: ERT use appears to improve linguistic, attentive and planning abilities. Interestingly, the beneficial effects on cognition were detected mainly in the past users subgroup. Here we propose that the trophic effect of estrogens on cerebellum might account for the observed improvement in cognition. [Copyright &y& Elsevier]

Summary. Defects in energy metabolism and oxidative stress play an important role in the pathogenesis of Alzheimer’s Disease (AD). In sporadic AD cases, presenilin 2 (PS2) mRNA levels are decreased in brain areas affected by the disease. The aim of the present study was to investigate whether mitochondrial dysfunction might influence PS2 gene expression. We demonstrated that the inhibition of energy metabolism by sodium azide down-regulates PS2 gene expression through modification of promoter activity. No one of the analyzed transcription factors, sensitive to redox status of the cell, could explain this effect. Azide effect on PS2 expression was completely inhibited by the addition of an antioxidant suggesting that the imbalance of the cellular redox homeostasis modulates the expression of this gene. [ABSTRACT FROM AUTHOR]

To test the validity of the new diagnostic criteria for Alzheimer's disease (AD) in a naturalistic series of patients with mild cognitive impairment (MCI). Ninety consecutive MCI patients were enrolled in a longitudinal study on the natural history of cognitive impairment. Medial temporal (MT) atrophy on MRI was defined as hippocampal volume below the fifth percentile of the distribution in healthy elders, abnormal CSF was based on Sjogren's cutoffs for Abeta42 and tau, and temporoparietal hypometabolism on 18F-FDG PET based on Herholz's t sum score. Patients were followed clinically to detect conversion to AD (MCI-AD), non-AD dementia (MCI-nAD), or no conversion (MCI-NC). The 24 MCI-AD and 15 MCI-nAD patients had sociodemographic, clinical, and neuropsychological baseline features similar to the 51 MCI-NC patients. All MCI patients with MT atrophy converted to AD, as did all those with abnormal CSF, but only 48 and 35% of those without MT atrophy or abnormal CSF converted ( p on logrank test = 0.0007 and 0.001). Prediction of AD conversion was enhanced when positivity to either MT atrophy or abnormal CSF was considered, with only 15% of those MCI patients negative on both converting to AD ( p < 0.0005). Markers were not predictive of non-AD dementia conversion. The accuracy of either MT atrophy or abnormal CSF in discriminating MCI-AD from MCI-NC was good (AUC 0.82, 95% CI 0.70-0.95). MT atrophy and abnormal CSF are the single most robust predictors of conversion to AD in MCI patients, and their combination enhances prediction. AD markers are not predictive of conversion to non-AD dementia. [ABSTRACT FROM AUTHOR]

Abstract: High plasma concentration of homocysteine is an independent risk factor for Alzheimer’s disease (AD), due to microvascular impairment and consequent neural loss [ Plasma homocysteine as a risk factor for dementia and Alzheimer’s disease. N Engl J Med 346(7):476–483]. Is high plasma homocysteine level related to slow electroencephalographic (EEG) rhythms in awake resting AD subjects, as a reflection of known relationships between cortical neural loss and these rhythms? To test this hypothesis, we enrolled 34 mild AD patients and 34 subjects with mild cognitive impairment (MCI). Enrolled people were then subdivided into four sub-groups of 17 persons: MCI and AD subjects with low homocysteine level (MCI− and AD−, homocysteine level <11 μmol/l); MCI and AD subjects with high homocysteine level (MCI+ and AD+, homocysteine level ≥11 μmol/l). Resting eyes-closed EEG data were recorded. EEG rhythms of interest were delta (2–4 Hz), theta (4–8 Hz), alpha 1 (8–10.5 Hz), alpha 2 (10.5–13 Hz), beta 1 (13–20 Hz), and beta 2 (20–30 Hz). EEG cortical sources were estimated by low-resolution brain electromagnetic tomography (LORETA). Results showed that delta (frontal and temporal), theta (central, frontal, parietal, occipital, and temporal), alpha 1 (parietal, occipital, and temporal), and alpha 2 (parietal and occipital) sources were stronger in magnitude in AD+ than AD− group. Instead, no difference was found between MCI− and MCI+ groups. In conclusion, high plasma homocysteine level is related to unselective increment of cortical delta, theta, and alpha rhythms in mild AD, thus unveiling possible relationships among that level, microvascular concomitants of advanced neurodegenerative processes, and synchronization mechanisms generating EEG rhythms. [Copyright &y& Elsevier]

Brain deposition of the amyloid-β protein (Aβ) is a frequent complication of Down’s syndrome (DS) patients. Aβ peptide is generated by endoproteolytic processing of Aβ precursor protein by γ and β secretases. Recently a transmembrane aspartyl protease, BACE, has been identified as the β-secretase, and its homologous BACE-2 has also been described. BACE-2 gene resides on chromosome 21 in the obligate DS region. It cleaves Aβ precursor protein at its β site and more efficiently at a different site within Aβ. In the present study we characterized the BACE-2 gene and protein expression in the DS patients and healthy control. We analyzed, by using a nonradioactive ribonuclease protection assay, the levels of BACE-2 mRNA expression in primary skin fibroblasts. The analysis revealed a 2.6-fold increase in BACE-2 mRNA levels in the DS group compared to the levels observed in the control group. Western blot analysis revealed no difference between DS and control in BACE-2 protein levels in the intracellular compartment. In the medium conditioned by fibroblast, we revealed an evident secretion of BACE-2 protein, represented by two different molecular weights, remarkably increased in DS fibroblasts. BACE-2 overexpression was also confirmed in the DS fetal brains and human neural embryonic DS stem cells in which conditioned media BACE-2 was secreted. These data highlight the importance of the extracellular compartment where BACE-2 overexpression could play a role in plaque formation in DS patients. [Copyright &y& Elsevier]

The injury caused by myocardial reperfusion after ischemia can be contained by interventions aimed at reducing the inflammation and the oxidative stress that underlie exacerbation of tissue damage. Sphingolipids are a class of structural and signaling lipid molecules; among them, the inflammation mediator ceramide accumulates in the myocardium upon ischemia/reperfusion. Here, we show that, after transient coronary occlusion in mice, an increased de novo ceramide synthesis takes place at reperfusion in the ischemic area surrounding necrosis (area at risk). This correlates with the enhanced expression of the first and rate-limiting enzyme of the de novo pathway, serine palmitoyltransferase (SPT). The intraventricular administration at reperfusion of myriocin, an inhibitor of SPT, significantly protected the area at risk from damage, reducing the infarcted area by 40.9 % relative to controls not treated with the drug. In the area at risk, myriocin downregulated ceramide, reduced the content in other mediators of inflammation and reactive oxygen species, and activated the Nrf2–HO1 cytoprotective response. We conclude that an enhanced ceramide synthesis takes part in ischemia/reperfusion injury and that myriocin treatment can be proposed as a strategy for myocardial pharmacological postconditioning. [ABSTRACT FROM AUTHOR]

In the prospect of improved disease management and future clinical trials in Frontotemporal Dementia, it is desirable to share common diagnostic procedures. To this aim, the Italian FTD Network, under the aegis of the Italian Neurological Society for Dementia, has been established. Currently, 85 Italian Centers involved in dementia care are part of the network. Each Center completed a questionnaire on the local clinical procedures, focused on (1) clinical assessment, (2) use of neuroimaging and genetics; (3) support for patients and caregivers; (4) an opinion about the prevalence of FTD. The analyses of the results documented a comprehensive clinical and instrumental approach to FTD patients and their caregivers in Italy, with about 1,000 newly diagnosed cases per year and 2,500 patients currently followed by the participating Centers. In analogy to other European FTD consortia, future aims will be devoted to collect data on epidemiology of FTD and its subtypes and to provide harmonization of procedures among Centers. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is characterized by extracellular amyloid-β (Aβ) deposition, which activates microglia, induces neuroinflammation and drives neurodegeneration. Recent evidence indicates that soluble pre-fibrillar Aβ species, rather than insoluble fibrils, are the most toxic forms of Aβ. Preventing soluble Aβ formation represents, therefore, a major goal in AD. We investigated whether microvesicles (MVs) released extracellularly by reactive microglia may contribute to AD degeneration. We found that production of myeloid MVs, likely of microglial origin, is strikingly high in AD patients and in subjects with mild cognitive impairment and that AD MVs are toxic for cultured neurons. The mechanism responsible for MV neurotoxicity was defined in vitro using MVs produced by primary microglia. We demonstrated that neurotoxicity of MVs results from (i) the capability of MV lipids to promote formation of soluble Aβ species from extracellular insoluble aggregates and (ii) from the presence of neurotoxic Aβ forms trafficked to MVs after Aβ internalization into microglia. MV neurotoxicity was neutralized by the Aβ-interacting protein PrP and anti-Aβ antibodies, which prevented binding to neurons of neurotoxic soluble Aβ species. This study identifies microglia-derived MVs as a novel mechanism by which microglia participate in AD degeneration, and suggest new therapeutic strategies for the treatment of the disease. [ABSTRACT FROM AUTHOR]

Abstract An association study of heterogeneous nuclear ribonucleoprotein (hnRNP)-A1 was carried out in a population of 274 patients with frontotemporal lobar degeneration (FTLD) and 287 with Alzheimer disease (AD) as compared with 344 age- and gender-matched controls. In addition, we evaluated expression levels of hnRNP-A1 and its regulatory microRNA (miR)-590-3p in blood cells from patients and controls. A statistically significant increased frequency of the hnRNP-A1 rs7967622 C/C genotype was observed in FTLD, but not in AD, in patients as compared to controls (23.0 versus 15.4%; p = 0.022, odds ratio [OR] 1.64, confidence interval [CI] 1.09-2.46). Stratifying according to gender, a statistically significant increased frequency of the hnRNP-A1 rs7967622 C/C genotype was observed in male patients as compared to male controls (23.1 versus 11.3%; p = 0.015, OR 2.36, CI 1.22-4.58 but not in females. Considering the rs4016671 single-nucleotide polymorphism (SNP), all patients and controls were wild type. Significantly increased hnRNP-A1 relative expression levels in peripheral blood mononuclear cells (PBMCs) was observed in patients with AD, but not with FTLD, as compared to controls (2.724 ± 0.570 versus 1.076 ± 0.187, p = 0.021). Decreased relative expression levels of hsa-miR-590-3p was observed in patients with AD versus controls (0.685 ± 0.080 versus 0.931 ± 0.111, p = 0.079), and correlated negatively with hnRNP-A1 mRNA levels (r = -0.615, p = 0.0237). According to these findings, hnRNP-A1 and its transcription regulatory factor miR-590-3p are disregulated in patients with AD, and the hnRNP-A1 rs7967622 C/C genotype is likely a risk factor for FTLD in male populations. [ABSTRACT FROM AUTHOR]

A number of mutations in microtubule associated protein tau gene (MAPT), causing frontotemporal lobar degeneration (FTLD) with tau pathology, are located in the four-repeated microtubule (MT) binding domains and affect the ability of tau to bind MTs. Here, we describe a novel variant lying in the second MT domain, found in a female patient diagnosed clinically with progressive nonfluent aphasia (PNFA), with a positive family history for dementia. At 65 years, she started developing progressive language deficits, characterized by expression difficulties and word coordination impairment. She came to our attention at 67 years. Her MMSE score was 22/30. A Brain CT scan showed mild diffuse cortical atrophy, ventricles' asymmetry (left > right), and very mild signs of chronic vasculopathy. Cerebrospinal fluid analysis showed normal amyloid-β₄₂, tau, and P-tau levels. She was diagnosed with PNFA according to current diagnostic criteria. A novel exon 10 MAPT variant was identified (g.123798G > A), which leads to an amino acidic change (p.Gly304Ser) in the second MT microtubule binding domain. In silico analysis predicted that this variant is damaging on protein structure and function. Additional 168 FTLD patients and 503 controls screened (1342 chromosomes) did not carry the variant, suggesting that it is a mutation rather than a polymorphism. The amino acid change likely compromises the ability of tau to properly regulate the dynamic behavior of microtubules. [ABSTRACT FROM AUTHOR]

Acetylcholinesterase inhibitors (AChEIs) have been used to improve cognitive status and disability in patients with mild to moderate Alzheimer's disease (AD). However, while the efficacy of AChEIs (i.e. how they act in randomized controlled trials) in this setting is widely accepted, their effectiveness (i.e. how they behave in the real world) remains controversial. To compare the effects of three AChEIs, donepezil (Aricept), galantamine (Reminyl) and rivastigmine (Exelon), in an Italian national, prospective, observational study representative of the 'real world' clinical practice of AChEI treatment for AD. 938 patients with mild to moderate AD collected within the framework of the Italian National Cronos Project (CP), involving several UVAs (AD Evaluation Units) spread over the entire national territory, who were receiving donepezil, galantamine or rivastigmine were followed for 36 weeks by measuring: (i) function, as determined by the Activities of Daily Living (ADL) and Instrumental Activities of Daily Living (IADL) scales; (ii) cognition, as measured by the Mini-Mental State Examination (MMSE) and the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog) [primary outcome measures]; and (iii) behaviour, as measured on the Neuropsychiatric Inventory (NPI) and Clinical Dementia Rating (CDR) scale. Moreover, all patients were genotyped for apolipoprotein E (apoE) genetic variants. No statistically significant improvement in the primary outcome measures (MMSE and ADAS-Cog) was observed with drug therapy at 36 weeks, at which point all groups had lost, on average, 1 point on the MMSE and gained 2-3 points on the ADAS-Cog scale compared with baseline. On the secondary outcome measures at week 36, all treatment groups showed a significant worsening on the ADL and IADL scales compared with baseline, while on the NPI scale there were no significant differences from baseline except for the galantamine-treated group which worsened significantly. Moreover, patients receiving galantamine worsened significantly compared with the donepezil-treated group on the IADL scale. ApoE epsilon4 allele did not influence the effect of drug therapy. Over a 36-week follow-up period, no significant difference in the effects of donepezil, galantamine and rivastigmine on a variety of functional and cognitive parameters was observed in a large number of apoE-genotyped patients with mild to moderate AD recruited within the framework of a national project representative of the scenario usually encountered in actual clinical practice in Italy. The limitations (possibility of administration of lower drug doses than are used in clinical trials, relatively short follow-up period and the lack of randomization) and strengths (large number of patients, concomitant observation of the three drugs and the number of parameters assessed, including apoE genotype) of the present study are acknowledged. Our type of naturalistic study should complement clinical trials because 'real world' practice operates in the face of the numerous variables (e.g. health status and co-morbidities) associated with a complex disease such as AD in elderly people. [ABSTRACT FROM AUTHOR]

Abstract: Previous studies suggest that in Alzheimer''s disease (AD) the Apolipoprotein E (APOE) ε4 allele is associated with greater vulnerability of medial temporal lobe structures. However, less is known about its effect on the whole cortical mantle. Here we aimed to identify APOE-related patterns of cortical atrophy in AD using an advanced computational anatomy technique. We studied 15 AD patients carriers (ε4+, age: 72±10 SD years, MMSE: 20±3 SD) and 14 non-carriers (ε4−, age: 69±9, MMSE: 20±5) of the ε4 allele and compared them to 29 age-and-sex matched controls (age: 70±9, MMSE: 28±1). Each subject underwent a clinical evaluation, a neuropsychological battery, and high-resolution MRI. UCLA''s cortical pattern matching technique was used to identify regions of local cortical atrophy. ε4+ and ε4− patients showed similar performance on neuropsychological tests (p >.05, t-test). Diffuse cortical atrophy was detected for both ε4+ (p =.0001, permutation test) and ε4− patients (p =.0001, permutation test) relative to controls, and overall gray matter loss was about 15% in each patients group. Differences in gray matter loss between carriers and non-carriers mapped to the temporal cortex and right occipital pole (20% greater loss in carriers) and to the posterior cingulate, left orbitofrontal and dorsal fronto-parietal cortex (5–15% greater loss in non-carriers). APOE effect in AD was not significant (p >.74, ANOVA), but a significant APOE by region (temporal vs fronto-parietal cortex) interaction was detected (p =.002, ANOVA), in both early and late-onset patients (p <.05, ANOVA). We conclude that the ε4 allele modulates disease phenotype in AD, being associated with a pattern of differential temporal and fronto-parietal vulnerability. [Copyright &y& Elsevier]

Background and aims: Neuronal nitric oxide synthase (NOS)1 C276T polymorphism was shown to increase the risk for frontotemporal lobar degeneration (FTLD). In the brain, both NOS1 and NOS3 (endothelial isoform) have been detected. The distribution of NOS3 G894T (Glu298Asp) and T-786C single nucleotide polymorphisms (SNPs) was analyzed in a population of 222 patients with FTLD compared with 218 age-matched controls to determine whether they could influence the susceptibility to develop the disease. Results: A statistically significant increased frequency of the NOS3 G894T SNP was observed in patients as compared with controls (40.0 vs. 31.4%, P = 0.011, OR: 1.65, CI: 1.13–2.42). Conversely, the distribution of the T-786C SNP was similar in patients and controls. No differences were observed stratifying according to gender. Discussion: The NOS3 G894T polymorphism likely acts as risk factor for sporadic FTLD, but studies in larger populations are needed to confirm these preliminary findings. [ABSTRACT FROM AUTHOR]

Resveratrol, a polyphenol found in grapes and other fruit and vegetables, is a powerful chemopreventive and chemotherapeutic molecule potentially of interest for the treatment of breast cancer. The human breast cancer cell line MCF-7, which is devoid of caspase-3 activity, is refractory to apoptotic cell death after incubation with resveratrol. Here we show that resveratrol arrests cell proliferation, triggers death and decreases the number of colonies of cells that are sensitive to caspase-3-dependent apoptosis (MCF-7casp-3) and also those that are unresponsive to it (MCF-7vc). We demonstrate that resveratrol (i) acts via multiple pathways to trigger cell death, (ii) induces caspase-dependent and caspase-independent cell death in MCF-7casp-3 cells, (iii) induces only caspase-independent cell death in MCF-7vc cells and (iv) stimulates macroautophagy. Using BECN1 and hVPS34 (human vacuolar protein sorting 34) small interfering RNAs, we demonstrate that resveratrol activates Beclin 1-independent autophagy in both cell lines, whereas cell death via this uncommon form of autophagy occurs only in MCF-7vc cells. We also show that this variant form of autophagic cell death is blocked by the expression of caspase-3, but not by its enzymatic activity. In conclusion, this study reveals that non-canonical autophagy induced by resveratrol can act as a caspase-independent cell death mechanism in breast cancer cells.Cell Death and Differentiation (2008) 15, 1318–1329; doi:10.1038/cdd.2008.51; published online 18 April 2008 [ABSTRACT FROM AUTHOR]

Background. White matter lesions (WMLs) may contribute to cognitive deficits in patients with mild cognitive impairment (MCI), but their pathogenesis is complex. Fluctuations of blood pressure (BP) over 24 hours and genetic predisposition to develop vascular damage have been implicated. Methods. In 63 MCI patients 65 years old or older, BP was measured both clinically and with ambulatory BP monitoring. Patients were classified in two groups: no/very mild (n = 34) and mild to severe (n = 29) WMLs, based on a visual scale on magnetic resonance (mean age 71.8 +/- 4.7 vs 74.6 +/- 5.1, and female gender 53% vs 66%, respectively). The volume of WMLs was measured by a semi-automatic method, separately for periventricular caps and rim, periventricular confluent, subcortical punctate, and subcortical confluent. Polymorphisms of cystatin C (CST3) and cholesterol 24-hydroxylase (CYP46) genes, putative risk factors for cerebrovascular disease, were determined. Results. The prevalence of cerebrovascular risk factors was similar in the two MCI groups of different WML severity, as well as clinic and ambulatory BP. In patients with mild to severe, but not in those with no/very mild WMLs, the volume of periventricular confluent WMLs increased with increasing daytime systolic BP (regression coefficient.47, 95% confidence interval [CI],.13 to.71 vs.02, 95% CI, -.32 to.36, p =.003 for the difference between slopes). The volume of other WML subtypes was not associated with ambulatory BP. Participants carrying both CST3*B and CYP46*T alleles were overrepresented in the MCI group with mild to severe WMLs (43% vs 17%, p.03). Conclusions. BP and gene putative risk factors for cerebrovascular disease are differentially associated with WMLs in two MCI groups of different WML severity. WMLs might develop for the convergence of innate with acquired factors. [ABSTRACT FROM AUTHOR]

Frontotemporal dementia (FTD) is the second commonest form of dementia after Alzheimer's disease, but its clinical and biological features are less well known. To uncover its earliest signs, we studied the main clinical, neuroimaging, and biochemical findings in an asymptomatic carrier from a three generation FTD family, bearing the P301L pathogenic mutation in the tau gene. Except for selective impairment on the Verbal Fluency Test for letters, all cognitive tests were normal. The brain computed tomography scan was normal, but the brain single photon emission computed tomography and statistical parametric mapping (SPECT-SPM) scan revealed bilateral frontal lobe hypoperfusion. Levels of total tau, 181P-tau, and Abeta1-42 in the cerebrospinal fluid were increased compared with control values. We conclude that detection of these distinctive abnormalities should improve early diagnostic accuracy for FTD and help distinguish it from Alzheimer's disease. [ABSTRACT FROM AUTHOR]

Despite promising preclinical animal studies, retinoic acid (RA), the bioactive derivative of vitamin A, has given disappointing results in clinical trials of human breast cancer because of the hurdle of RA resistance. RA resistance seems to have an heterogeneous molecular basis. One form of RA resistance in breast cancer has been traced to epigenetic silencing of RA receptors (RARs). In the breast cancer cell line T47D, RA treatment (1 µmol/L, 72 h) induced impaired cell growth and apoptosis concomitant with a 2.3-fold increase of endogenous ceramide, a sphingolipid with a recognized role as proapoptotic second messenger. In contrast, in the breast cancer cell line MDA-MB-231 the same treatment failed to induce both growth arrest and accumulation of proapoptotic ceramide. The two cell lines differ in their RAR profiles in that T47D cells are RAR-α positive and RAR-β inducible whereas MDA-MB-231 cells are RAR-α and RAR-β negative. Thus we hypothesized that ceramide accumulation may be mediated by RARs. To test this hypothesis we engineered T47D cells to stably express an RAR-α dominant-negative (DN) construct. DN T47D cells present an RA-resistant phenotype and fail to accumulate ceramide in response to RA treatment. In addition, by inhibiting RAR-α in T47D cells with RAR-α antagonists, we observed a failure to accumulate endogenous ceramide. Altogether these data indicate that RA-induced ceramide in T47D cells is mediated by RAR-α signaling. The synthetic retinoid fenretinide, 4-HPR, whose action is largely independent of RARs, was able to induce cell death and a concomitant ceramide increase in the MDA-MB-231 cell line, thus indicating that the biochemical machinery required for endogenous ceramide production is intact. In conclusion, we show that RA resistance associated with a lack of functional RARs in breast cancer cells can be overcome by using synthetic retinoids such as 4-HPR. [ABSTRACT FROM AUTHOR]