Autism, language delay and mental retardation in a patient with 7q11 duplication

Chromosomal rearrangements are found in a subset of patients with autism. Duplications involving loci associated with behavioural disturbances constitute an especially good candidate mechanism. The Williams-Beuren critical region (WBCR), located at 7q11.23, is commonly deleted in Williams-Beuren microdeletion syndrome (WBS). However, only four patients with a duplication of the WBCR have been reported to date. Here, 206 patients with autism spectrum disorders were screened for the WBCR duplication by quantitative microsatellite analysis and multiple ligation-dependent probe amplification. One male patient with a de novo interstitial duplication of the entire WBCR of paternal origin was identified. The patient had autistic disorder, severe language delay and mental retardation, with mild dysmorphism. The present report concerns the first patient with autistic disorder and a WBCR duplication. This observation indicates that the 7q11.23 duplication could be involved in complex clinical phenotypes, ranging from developmental or language delay to mental retardation and autism.

Autism, language delay and mental retardation in a patient with 7q11 duplication

BACKGROUND

Chromosomal rearrangements, arising from unequal recombination between repeated sequences, are found in a subset of patients with autism. Duplications involving loci associated with behavioural disturbances constitute an especially good candidate mechanism. The Williams-Beuren critical region (WBCR), located at 7q11.23, is commonly deleted in Williams-Beuren microdeletion syndrome (WBS). However, only four patients with a duplication of the WBCR have been reported to date: one with severe language delay and the three others with variable developmental, psychomotor and language delay.

OBJECTIVE AND METHODS

In this study, we screened 206 patients with autism spectrum disorders for the WBCR duplication by quantitative microsatellite analysis and multiple ligation-dependent probe amplification.

RESULTS

We identified one male patient with a de novo interstitial duplication of the entire WBCR of paternal origin. The patient had autistic disorder, severe language delay and mental retardation, with very mild dysmorphic features.

CONCLUSION

We report the first patient with autistic disorder and a WBCR duplication. This observation indicates that the 7q11.23 duplication could be involved in complex clinical phenotypes, ranging from developmental or language delay to mental retardation and autism, and extends the phenotype initially reported. These findings also support the existence of one or several genes in 7q11.23 sensitive to gene dosage and involved in the development of language and social interaction.

Protein kinase Cgamma autoimmunity in paraneoplastic cerebellar degeneration and non-small-cell lung cancer

BACKGROUND

The clinical and immunological profiles of patients with paraneoplastic cerebellar degeneration (PCD) and non-small-cell lung cancer (NSCLC) are not well known.

OBJECTIVE

To review the clinical and immunological features of patients with PCD, NSCLC and without well-characterised onconeural antibodies.

METHODS

The clinical features of nine patients with the diagnosis of classical PCD and NSCLC, included in our archives, were retrospectively reviewed. The presence of antibodies to cerebellar components was determined by immunohistochemistry and immunoblot of rat cerebellum. A cDNA library of human cerebellum was screened with the positive sera to identify the antigen.

RESULTS

Nine patients with PCD and NSCLC were identified. Six patients were men, and the median age at diagnosis of PCD was 63 (range 47-73) years. PCD was completely reversed in two patients, and partially in one, after treatment of the tumour. The serum of one of the patients with PCD showed a unique reactivity with Purkinje cells. The screening of a cerebellar-expression library resulted in the isolation of protein kinase Cgamma (PKCgamma). PKCgamma immunoreactivity was not observed in the serum of 170 patients with non-paraneoplastic neurological syndromes, 27 patients with PCD, no onconeural antibodies and small-cell lung cancer, and 52 patients with NSCLC without paraneoplastic neurological syndromes. The NSCLC from 11 patients without PCD did not express PKCgamma at either the RNA or protein level. However, many cells of the NSCLC of the patient with PKCgamma antibodies expressed PKCgamma.

CONCLUSION

PCD occurs in patients with NSCLC without typical onconeural antibodies and is associated with immune reactions against key proteins of the Purkinje cells.

T cell response to Hu-D peptides in patients with anti-Hu syndrome

The anti-Hu syndrome is the most common paraneoplastic neurologic syndrome but the exact mechanism of immune mediated neuronal injury remains unknown. Anti-Hu antibodies do not appear to play a pivotal role in the pathogenesis of the disease. To assess cell-mediated immunity, we selected 51 peptides from the Hu-D sequence and tested their ability to bind to six common HLA class I molecules. Stable complexes with purified HLA molecules were obtained with 19/51 (37%) selected peptides. Subsequently, the ability of the 19 HLA-binding peptides to stimulate T cells from 10 patients and 10 control subjects was evaluated by detecting IFN-gamma secretion. An anti-peptide T-cell response was observed in 7/10 Hu-positive patients but also in 3/10 control subjects. Overall, a significant T-cell activation occurred in response to 74% (14 out of 19) of the selected peptides in the Hu-positive patients vs. 16% (3 out of 19) in the control group (p < 0.001). In addition, T cells of patients tested within 3 months of the onset of anti-Hu syndrome responded to 82% (14 out of 17) of assessed Hu-D peptides vs. 37% (7 out of 19) in patients tested 1 year or more after developing the syndrome (p < 0.01). Thus, the present study suggests a role of cellular immunity during the course of anti-Hu syndrome.

Multidrug resistance-associated protein MRP1 expression in human gliomas: chemosensitization to vincristine and etoposide by indomethacin in human glioma cell lines overexpressing MRP1

The 190 kDa multidrug resistance protein MRP1 is likely to be involved in the multidrug resistance phenotype of human gliomas. MRP1 expression was evaluated in surgical tumor samples from 17 patients with gliomas. In addition, the impact of the MRP's inhibitor, indomethacin, on the chemosensitivity to etoposide (VP16) and vincristine (VCR) of two glioblastoma cell lines expressing MRP1 (GL15 and 8MG) was investigated. When evaluated in tumor samples, MRP1 expression was observed in all of them with more than 90% of stained tumor cells in 14/15 high-grade gliomas. MRP1 was also strongly expressed at the membrane of the vascular endothelial cells in the same 14 tumor samples, suggesting that the permeability to anticancer drugs could be also limited across brain tumor vessels. At concentrations comprised between 5 and 50 microM, indomethacin significantly increased the cytotoxic effect of etoposide in both cell lines but it was more efficient in increasing the cytotoxicity of VCR on GL15 cells, as compared with 8MG cells. These results suggest that the association of indomethacin to VCR or etoposide could be of interest in the clinical management of gliomas.

Paraneoplastic antineuronal antibodies in patients with systemic autoimmune diseases

Sera from 71 patients with primary Sjögren's syndrome (PSS) and from 102 patients with systemic lupus erythematosus (SLE) were tested by immuno-dot blotting against HuD, Ri, Yo and amphiphysin recombinant proteins. For Ri, Yo and amphiphysin antigens, no immunoreactivity was found in the 173 sera tested. One PSS patient with a clinical picture of subacute sensory neuronopathy had high titers of anti-Hu antibodies. An extensive search for an underlying tumor was initially negative but a small cell lung cancer was eventually discovered three years later. Another patient with SLE and a clinical picture of demyelinating polyradiculoneuropathy had anti-Hu antibodies. Repeated search for an underlying tumor remains negative after five years follow-up in this young non-smoking patient. In addition, the neuropathy progressively improved and the anti-Hu antibodies titer slowly decreased from 1:8000 to 1:2000, making the diagnosis of paraneoplastic syndrome unlikely in this patient. This study indicates that the detection of anti-Hu antibodies in patients with known symptomatic systemic autoimmune diseases such as PSS or SLE should induce the same work-up than the detection of these antibodies in the absence of other immune diseases, i.e. repeated search for occult cancer during several years. As illustrated by our first patient, this strategy may be fruitful. Nevertheless, the clinician should know that anti-Hu antibodies may exceptionally (0.6% in this series) occur in systemic autoimmune disorders with neurological complications, in the absence of an underlying neoplastic disease.

Oligoclonal T-cells in blood and target tissues of patients with anti-Hu syndrome

T-cell clones of unknown significance (TCUS), assessed by monoclonal or oligoclonal T-cell patterns in PCR-DGGE, were detected in blood of 7/9 patients with anti-Hu syndrome. Clonal patterns were also detected in 2/2 neoplastic lymph nodes, and in 2/2 inflamed dorsal root ganglia from three patients. Only some T-cell clones found in target tissues were also detected in blood or non-target tissues, and likely corresponded to TCUS. In one patient, an identical T-cell clone was found in both neoplastic lymph node tissue and dorsal root ganglia, but not in blood. Dorsal root-infiltrating lymphocytes were cytotoxic CD8(+) TIA-1(+) T-cells. They were often found in close contact to sensory neurons, most of which expressed MHC-1. Taken together, these data support a direct effector role of cytotoxic CD8(+) T-cells, the same clones being likely operative in sensory neuron damage and immune-mediated tumor growth control.

Anti-Hu-associated paraneoplastic encephalomyelitis: analysis of 200 patients

We reviewed 200 patients with paraneoplastic encephalomyelitis (PEM) and anti-Hu antibodies to show possible clinical differences with respect to previous series, and to identify patient, tumour and treatment-related characteristics associated with neurological disability and survival. The median age of the 200 patients was 63 years (range 28-82 years) and 75% were men. The predominant neurological syndromes were sensory neuropathy (54%), cerebellar ataxia (10%), limbic encephalitis (9%) and multifocal involvement (11%). Sensorimotor neuropathies with predominant motor involvement were observed in only 4% of the patients. Pathological or X-ray evidence of a tumour was obtained in 167 patients (83%) and was a small-cell lung cancer (SCLC) in 74% of those with histological diagnosis. Coexistence of extrathoracic tumours with SCLC was rare (0.5%). Positive Hu immunoreactivity was observed in the extrathoracic tumours of six out of seven patients in whom autopsy or long-term follow-up ruled out a coexisting SCLC. PEM preceded the diagnosis of the tumour in 71% of patients (mean delay +/- SD 6.5 +/- 7.0 months; range 0.1-47 months). In the 24 patients in whom the tumour diagnosis was the initial event, PEM predicted the progression or relapse of the tumour in 87% of them. No tumour was found in 33 patients, including four who had a post-mortem study and four with >5 years of follow-up. In a logistic regression analysis, treatment of the tumour, associated or not with immunotherapy, was an independent predictor of improvement/stabilization of PEM [odds ratio 4.56; 95% confidence interval (CI) 1.62-12.86]. Cox multivariate analysis indicated that the variables independently associated with mortality were: age >60 years [relative risk (RR) 1.49; 95% CI 1.05-2.12], Rankin score at diagnosis >3 (RR 1.60; 95% CI 1.12-2.28), more than one area of the nervous system affected (RR 1.61; 95% CI 1.08-2.40), and absence of treatment (RR 2.56; 95% CI 1.76-3.71). We conclude that, unlike previous series, the majority of our patients were male, and there was a low occurrence of predominantly motor neuropathies and extrathoracic tumours coexisting with SCLC. When the diagnosed extrathoracic tumour expresses Hu antigens, further tests to rule out a coexisting SCLC are probably unnecessary. Finally, the predictors of mortality and PEM evolution found in the study may be important in the design of future therapeutic protocols, and emphasize the importance of early diagnosis and treatment of the underlying tumour.

[Subacute neuropathy, multiple cancers, and Gougerot-Sjögren syndrome: contribution of anti-Hu antibody]

We report the case of a patient presenting a subacute, predominantly sensory neuropathy. The work up revealed a Sjögren's syndrome and a breast carcinoma. The presence of anti-Hu antibodies, identified by Western Blot using purified recombinant HuD protein, and the absence of the Hu antigen in the breast carcinoma ruled out the responsibility of the Sjögren's syndrome or breast carcinoma. In this context, the most likely diagnosis was a subacute neuropathy associated with small cell lung cancer, which was indeed discovered 3 years later.

Association of herpes simplex virus encephalitis and paraneoplastic encephalitis - a clinico-pathological study

A 57 year-old woman developed acute limbic encephalitis and brainstem dysfunction. Anti-HU antibodies were repeatedly detected in serum and CSF. Postmortem examination showed necrotic and hemorrhagic lesions in the temporal lobes characteristic of herpes simplex virus encephalitis, which was confirmed by immunocytochemistry, and Purkinje cell loss with proliferation of Bergman glia and myelin loss in the external aspect of the dentate nuclei characteristic of paraneoplastic encephalitis. PCR-assay performed on temporal tissue extracts was positive for HSV-1. There was no identifiable neoplasm. This unusual association raises the possibility of a link between the two diseases.

Cell-mediated autoimmunity in paraneoplastic neurological syndromes with anti-Hu antibodies

Paraneoplastic encephalomyelitis or subacute sensory neuronopathy associated with small-cell lung cancer (SCLC) and high titers of anti-HuD antibodies, also called the "anti-Hu syndrome," is believed to result from an immune response triggered by tumor antigens and misdirected to the neurons. To further assess the issue of cell-mediated immunity in this disease, the peripheral blood lymphocyte surface phenotype was studied in 15 patients suffering from the anti-Hu syndrome (seropositive group) and in two control groups consisting of 12 seronegative SCLC patients without neurological syndrome and 15 healthy volunteers. In addition, the recombinant human HuD protein was used to stimulate in vitro peripheral blood mononuclear cells of 10 seropositive patients and of 10 patients from each control group. Phenotypic analysis of the peripheral blood lymphocytes revealed a significant increase of the memory helper (CD45RO+CD4+) T cells in the seropositive group in comparison with the two control groups. Antigen-specific proliferation of peripheral blood mononuclear cells, measured by [3H]thymidine uptake after HuD antigen stimulation, was much higher in the seropositive group than in the two control groups, and phenotypic analysis of proliferating cells revealed a significant expansion of the CD45RO subpopulation of T cells in the seropositive group. Furthermore, after HuD stimulation, a significant increase of the interferon-gamma/interleukin-4 ratio was found in culture supernatants of the seropositive group compared with seronegative SCLC patients and normal controls. Taken together, these results indicate that HuD protein is an antigenic target for autoreactive CD4+ T cells, presumably of the Th1 subtype, which could therefore be directly involved in cell-mediated injury of the nervous system as well as in antitumoral immunity.

The pathophysiology of paraneoplastic neurological syndromes

Paraneoplastic neurological diseases are a group of neurological disorders associated with neoplastic tumors but not due to tumoral extension, metabolic, infectious, vascular or toxic complications of these tumors or their treatment. In the majority of paraneoplastic neurological disorders, circulating autoantibodies directed against neurons have been found in the serum and/or the CSF suggesting, and in some cases implicating, autoimmunity in the pathophysiology of these diseases. The finding of autoimmune phenomena during the course of paraneoplastic neurological disorders is of importance: from a practical point of view, since the detection of anti-neuronal autoantibodies is of great diagnostic help and should lead to the thorough search of the associated tumor often at an early stage of its development; from a theoretical point of view, these disorders represent a peculiar type of molecular mimicry. Tumoral neontigens having structural homology or identity with neuronal autoantigens elicit autoreactivity. The immunological effector mechanisms involved in the pathophysiology of paraneoplastic syndromes appear to differ according to the disease: autoantibodies are pathogenic in Lambert-Eaton syndrome whereas, in paraneoplastic cerebellar degeneration and in the Hu syndrome, the cellular immune response might play a greater role.

[Asphyxiating intra-alveolar hemorrhage: a rare form of fat embolism syndrome]

We report a case of a 23-year-old patient admitted for a right femur fracture resulting from a traffic accident. An intra-alveolar haemorrhage occurred 48 hours later, with asphyxia anaemia, haematic bronchial aspirations, and bilateral alveolar opacities at chest X-ray. This symptomatology was associated with fever, sub-conjunctival petechiae, major hypocholesterolemia, deterioration of renal function, and cholestasis. All these features suggested a fat embolism. Other possible aetiologies were discarded because of normal cardiovascular and immunologic systems and absence of infection. The outcome under symptomatic treatment was satisfactory within 15 days. The occurrence of intra-alveolar haemorrhage in post-traumatic fat embolism is a rare event caused by pulmonary capillary obstruction by fat emboli.

[Glomangioma of the popliteal fossa. Apropos of a case]

Glomus tumours are relatively uncommon lesions most frequently found in the extremitis, usually in the digits. They are most often solitary lesions but multiple tumours have been reported. If the triad of pain, tenderness and cold intolerance should raise the clinical suspicion of a digital glomus. The histological exam is necessary in the extra digital glomus. We reported a case of fossa poplitea glomangioma with tibialis nerve compression. The treatment of choice was a surgical exision. But the tumour have been redivided a year later without malign transformation.

[Paraneoplastic intestinal pseudo-obstruction revealing small cell lung carcinoma: "the anti-Hu syndrome"]

A 67-year-old woman was admitted for intestinal pseudoobstruction associated with peripheral sensitive neuropathy. Jejunal biopsies performed during laparotomy, showed axonal degeneration and lympho-plasmocytic infiltration in myenteric plexus. High titer of seric anti-Hu antibodies suggested a paraneoplastic syndrome. Thoracic CT scan showed mediastinal lymph nodes. Their histological examination confirmed the diagnosis of metastatic small-cell lung carcinoma. Her condition gradually deteriorated despite supportive parenteral nutrition, chemotherapy, steroids and intravenous immunoglobulins. She died 12 months after the onset of symptoms.

[Arterial thrombosis in the course of nephrotic syndrome. Report of three cases]

Vascular thrombosis remains severe complication in patients with nephrotic syndrome. Both venous and arterial thrombosis are observed. We report three new cases of arterial thrombosis in patients with nephrotic syndrome. The role of acquired hemostasis disorders, inducing hypercoagulability, is predominant. Extramembranous glomerulonephritis remains the most frequent cause of nephrotic syndrome, complicated by vascular thrombosis. Treatment is based on anticoagulation and corticosteroid therapy. Search for proteinuria should be part of the etiology work-up in all patients with vascular thrombosis of undetermined origin.

[Arterial complications of Behcet's disease. Report of 13 cases]

Vascular involvement, usually venous thrombosis, is common in Behçet's disease. Arterial manifestations, usually aneurysms or more rarely occlusion, are less common. We analyzed 13 cases of Behçet's disease with arterial complications. This fourth series in the literature was collected over 11 years. There were 12 men and 1 woman, mean age 41 +/- 7 years. Mean delay to arterial complications was 5.8 years (maximum 20 years) after the first sign of the disease. In the 13 patients in our series, there were a total of 18 arterial lesions, including one aneurysm and one stenosis of the internal carotid artery. There were 2 cases (10%) with lesions of the aorta (aneurysms). Approximately half of the arterial lesions (7/18) involved the femoral artery. There were 11 localizations on the femoropopliteal axis (11 aneurysms). One aneurysm of the humeral artery was the only localization in the upper limb. Vascular involvement was limited to arterial lesions in 9/13 patients with multiple lesions at different localizations in 2 patients. In two others, a second arterial localization occurred secondarily. All patients except one were operated. Mid-term complications are: 1 death and 4 thrombi including 3 with good results after reoperation. In these patients with Behçet's disease, risk of severe complications is important, requiring long-term surveillance.

[False hydatic aneurysm of the thoraco-abdominal aorta]

Arterial complications of hydatic disease are rarely encountered. We report a false hydatic aneurysm of the thoracoabdominal aorta revealed by ischemic embolism of the lower limbs. Surgical treatment included aorto-aortic prosthesis and albendazol for 6 months. Results at 18 months are excellent with negative hydatic serology. In endemic areas, hydatic disease is a possible cause of false aneurysms. Long-term surveillance is required after curative surgery and medical treatment.

Imaging and biodistribution of 125I tyramine oligonucleotide in nude mice bearing human breast tumor. Preliminary report

Although the range of applications for antisense oligonucleotides is vast, current research concentrates mainly on virology and oncology. We have conducted in vivo and in vitro investigations of radiolabelling and biodistribution of a 22-mer phosphodiester oligonucleotide injected in athymic mice bearing xenograft of human mammary tumor (coculture: MCF7 and fibroblasts strain AF-11). Tumor/healthy tissue ratio of the 22-mer phosphodiester oligonucleotide fixation is high during the 24 hours after injection instead of fast elimination.

[Applications of antisense oligonucleotides in oncology]

The development of biotechnologies offers considerable potential for new therapeutical approaches, targetting nucleic acids as information bearing molecules responsible for various pathologies. Gene therapy has, up to now, mainly aimed at compensating deficiencies of gene expression, through complex molecular and cellular constructions. Recently, an increasing interest has focused on short nucleotidic sequences (thus relatively easy to synthetize), or oligonucleotides, which could be able to specifically block the expression of mutated or overexpressed genes. When the target of these oligonucleotides is the mRNA of such genes, the strategy is called "antisense". This strategy has already led to a number of successful results in experimental models in vitro. Much more rare are actual effects in animal models and clinical trials are just being sketched. A review on the current state of the art will enlighten the physiological potential of these new molecules but also underline the still numerous issues before controlling therapeutical applications.

Transforming growth factor-beta and megakaryocytes in the pathogenesis of idiopathic myelofibrosis

Although the disease is well described, the pathogenesis of bone marrow fibrosis in idiopathic myelofibrosis still remains unclear. We previously reported elevated intraplatelet transforming growth factor-beta (TGF-beta) levels in patients with this myeloproliferative disorder, compared with healthy subjects. Here, in a series of 16 patients, we show that TGF-beta expression is also increased in patients' peripheral blood mononuclear cells (PBMC): (i) at the mRNA level analysed by Northern blot hybridization and/or reverse transcription-polymerase chain reaction (RT-PCR); (ii) and/or at the secreted peptide level as evaluated in conditioned media from patients' mononuclear cells by a growth inhibition assay on CC164 cells. By immunostaining with a polyclonal anti-TGF-beta 1 antibody, TGF-beta was localized in morphologically heterogenous cells; these cells were characterized as megakaryocytes by labelling with a gpIIbIIIa monoclonal antibody. Thus we provide evidence that both TGF-beta and megakaryocytes are linked in the pathogenesis of idiopathic myelofibrosis.

Erythema gyratum repens. A case studied with immunofluorescence, immunoelectron microscopy and immunohistochemistry

We report a patient with erythema gyratum repens (EGR), in whom a bronchial carcinoma was found. Direct immunofluorescence revealed granular deposits of immunoglobulins at the basement membrane zone (BMZ) in the skin, and in the lung tumour. Direct immunoelectron microscopy showed that the immune deposits were localized just beneath the lamina densa. Indirect immunofluorescence revealed circulating anti-BMZ antibodies. Immunohistochemical staining, using anti-transforming growth factor-beta, anti-epidermal growth factor receptor, anti-vimentin and anti-alpha-actin, was found to be more intense in the lesional skin and the lung tumour than in normal tissues. Possible mechanisms in the pathogenesis of EGR are discussed.

Breast cancer proliferation measured on cytological samples: a study by flow cytometry of S-phase fractions and BrdU incorporation

Cell kinetics have been shown to be an important predictor of clinical evolution of operated breast cancer. We established a method for the estimation of the proliferative activity of tumour cells obtained by fine needle sampling without aspiration (FNS), using simultaneously S-phase fractions (SPF) measured on DNA histograms and 5-bromodeoxyuridine (BrdU) labelling index (BLI) measured by flow cytometry. Biparametric BrdU/DNA flow cytometry could be performed in 122 of 189 (65%) consecutive patients. The mean BLI of the cytologically malignant FNS (118) was of 3.0 and the median of 2.2%. One hundred and forty-eight DNA histograms (78%) were suitable for SPF analysis, of which 141 presented malignant cells, showing a mean of 4.5 and a median of 3.5%, comparable to BLIs. These results were obtained from fluorescence peak area histograms with doublet discrimination and background subtraction allowing the measurements of SPFs as low as 0.4%. An excellent correlation was thus observed between BLIs and SPFs, for the 94 cases for which both results were available (r = 0.85). Infrequent discordances (9%) were noted with SPFs considerably higher than BLIs. Seven patients had three consecutive FNS of their tumour at weekly intervals before treatment. Some variability in the proportions of multiple subpopulations of tumour cells was observed on the DNA histograms. In contrast, proliferation indices (SPF or BLI) were reproducible, suggesting homogeneous growth rates. We conclude that an estimation of the proliferative activity of breast tumours at any stage of the disease is possible routinely by SPF and/or BLI analysis of FNS. At least one quantitative proliferation index could be obtained for 91% of patients.

Arterial manifestations in Behçet's disease: four new cases

Four new arterial lesions observed with Behçet's disease are reported: two popliteal aneurysms, one carotid aneurysm and one carotid stenosis. The clinical features, therapeutic modalities and postoperative complications of these uncommon lesions are reviewed briefly.

New approach for visualizing estrogen receptors in target cells using inherently fluorescent ligands and image intensification

Four fluorescent estrogen ligands were investigated as agents for visualization of estrogen receptors in cells: 2-(2,4-dihydroxyphenyl)-6-hydroxy-3-benzofurancarboxylic acid delta-lactone (coumestrol) and 9(11)-dehydro-12-oxoestradiol [12-oxo-1,3,5-(10),9(11)-estratetraene-3, 17 beta-diol] (12-oxoestradiol), which are inherently fluorescent compounds; and tamoxifen [Z)-1-[4-(2-dimethylaminoethoxy)phenyl]-1,2-diphenyl-1-butene) and 4-hydroxytamoxifen [Z)-1-[4-(2-dimethylaminoethoxy) phenyl]-1-(4-hydroxyphenyl)-2-phenyl-1-butene), which become maximally fluorescent only after ultraviolet irradiation. By conventional fluorescence techniques, these agents can be detected down to 10(-8) M in water, but only to 10(-6) to 10(-7) M in protein solutions; however, by photon-counting spectrofluorimetry, coumestrol and 12-oxoestradiol can be detected in protein solutions down to 5 X 10(-10) M. Three of these compounds have good affinity for the estrogen receptor: coumestrol (20%); 12-oxoestradiol (12%); and 4-hydroxytamoxifen (37%), relative to estradiol (100%). Under conditions where autoradiographic controls indicate that most of the estrogen receptor of MCF-7 human breast cancer cells is in the nucleus, we could demonstrate nuclear fluorescence using 10(-9) M concentrations of coumestrol, 12-oxoestradiol, and 4-hydroxytamoxifen. This nuclear fluorescence was abolished by a 200-fold excess of diethystilbestrol and could only be observed through a fluorescence microscope equipped with a microchannel image intensifier and a video camera detector that together provide a sensitivity enhancement of approximately 10(4). These studies indicate that the estrogen receptor in breast cancer cells can be visualized by fluorescence techniques, provided that the visualizing ligands have adequate affinity and specificity for the receptor and appropriate fluorescence characteristics, and provided that the fluorescence instrument has adequate sensitivity to observe fluorescence emission from cells treated with nM concentrations of the fluorescent agents.