Surface acoustic wave (SAW) real-time interaction analysis of influenza A virus hemagglutinins with sialylated neoglycolipids

Real-time interaction analysis of H1 hemagglutinin from influenza A H1N1 (A/New York/18/2009) and H7 hemagglutinin from influenza A H7N7 (A/Netherlands/219/03) with sialylated neoglycolipids (neoGLs) was performed using the surface acoustic wave (SAW) technology. The produced neoGLs carried phosphatidylethanolamine (PE) as lipid anchor and terminally sialylated lactose (Lc2, Galβ1-4Glc) or neolactotetraose (nLc4, Galβ1-4GlcNAcβ1-3Galβ1-4Glc) harbouring an N-acetylneuraminic acid (Neu5Ac). Using α2-6-sialylated neoGLs, H1 and H7 exhibited marginal attachment towards II6Neu5Ac-Lc2-PE, whereas Sambucus nigra lectin (SNL) exhibited strong binding and Maackia amurensis lectin (MAL) was negative in accordance with their known binding preference towards a distal Neu5Acα2-6Gal- and Neu5Acα2-3Gal-residue, respectively. H1 revealed significant binding towards IV6Neu5Ac-nLc4-PE when compared to weak interaction of H7, while SNL showed strong and MAL no attachment corresponding to their interaction specificities. Additional controls of MAL and SNL with α2-3-sialylated II3Neu5Ac-Lc2-PE and IV3Neu5Ac-nLc4-PE underscored the reliability of the SAW technology. Pre-exposure of model membranes spiked with α2-6-sialylated neoGLs to Vibrio cholerae neuraminidase substantially reduced the binding of the hemagglutinins and the SNL reference. Collectively, the SAW technology is capable of accurate measuring binding features of hemagglutinins towards neoGL-spiked lipid bilayers, which can be easily loaded to the functionalized biosensor gold surface thereby simulating biological membranes and suggesting promising clinical application for influenza virus research.

Real-time interaction analysis of Shiga toxins and membrane microdomains of primary human brain microvascular endothelial cells

Infections of the human intestinal tract with enterohemorrhagic Escherichia coli (EHEC) result in massive extraintestinal complications due to translocation of EHEC-released Shiga toxins (Stxs) from the gut into the circulation. Stx-mediated damage of the cerebral microvasculature raises serious brain dysfunction being the most frequent cause of acute mortality in patients suffering from severe EHEC infections. Stx2a and Stx2e are associated with heavy and mild course of infection, respectively. Stx2a preferentially binds to globotriaosylceramide (Gb3Cer, Galα1-4Galβ1-4Glcβ1-1Cer), while Stx2e prefers globotetraosylceramide (Gb4Cer, GalNAcβ1-3Galα1-4Galβ1-4Glcβ1-1Cer). Both glycosphingolipids (GSLs) were detected in detergent-resistant membranes (DRMs) of primary human brain microvascular endothelial cells (pHBMECs) resembling microdomains of the plasma membrane. In this study, we show that Gb3Cer and Gb4Cer of pHBMECs with saturated C16:0, C22:0, and C24:0 fatty acids dominated in DRMs, corresponding to the liquid-ordered membrane phase, whereas lipoforms carrying unsaturated C24:1 and C24:2 fatty acids prevailed in the non-DRM fractions, which correspond to the liquid-disordered membrane phase. Similarly, a shift of the phospholipids from saturated lipoforms in the DRM to unsaturated species in the non-DRM fractions was observed. Real-time biomolecular interaction analysis using affinity-purified Stx2a and Stx2e, recorded with a surface acoustic wave (SAW) biosensor, evidenced high binding strength of both toxins toward DRMs and failure in interaction with non-DRMs. These results support the hypothesis of preferential binding of Stxs toward microdomains harboring GSL receptors carrying saturated fatty acids in their lipid anchors. Collectively, unraveling the precise mechanisms of Stx-microdomain interaction may help to develop antiadhesive compounds to combat Stx-mediated cellular injury.

PapG subtype-specific binding characteristics of Escherichia coli towards globo-series glycosphingolipids of human kidney and bladder uroepithelial cells

Uropathogenic Escherichia coli (UPEC) are the primary cause of urinary tract infections (UTIs) in humans. P-fimbriae are key players for bacterial adherence to the uroepithelium through the Galα1-4Gal-binding PapG adhesin. The three identified classes I, II and III of PapG are supposed to adhere differently to host cell glycosphingolipids (GSLs) of the uroepithelial tract harboring a distal or internal Galα1-4Gal sequence. In this study, GSL binding characteristics were obtained in a nonradioactive adhesion assay using biotinylated E. coli UTI and urine isolates combined with enzyme-linked NeutrAvidin for detection. Initial experiments with reference globotriaosylceramide (Gb3Cer, Galα1-4Galβ1-4Glcβ1-1Cer), globotetraosylceramide (Gb4Cer, GalNAcβ1-3Galα1-4Galβ1-4Glcβ1-1Cer) and Forssman GSL (GalNAcα1-3GalNAcβ1-3Galα1-4Galβ1-4Glcβ1-1Cer) revealed balanced adhesion toward the three GSLs for PapG I-mediated attachment. In contrast, E. coli carrying PapG II or PapG III increasingly adhered to growing oligosaccharide chain lengths of Gb3Cer, Gb4Cer and Forssman GSL. Binding studies with GSLs from human A498 kidney and human T24 bladder epithelial cells, both being negative for the Forssman GSL, revealed the less abundant Gb4Cer vs. Gb3Cer as the prevalent receptor in A498 cells of E. coli expressing PapG II or PapG III. On the other hand, T24 cells exhibited a higher relative content of Gb4Cer vs. Gb3Cer alongside dominant binding of PapG II- or PapG III-harboring E. coli toward Gb4Cer and vastly lowered attachment to minor Gb3Cer. Further studies on PapG-mediated interaction with cell surface-exposed GSLs will improve our knowledge on the molecular mechanisms of P-fimbriae-mediated adhesion and may contribute to the development of antiadhesion therapeutics to combat UTIs.

Structural Insights into Escherichia coli Shiga Toxin (Stx) Glycosphingolipid Receptors of Porcine Renal Epithelial Cells and Inhibition of Stx-Mediated Cellular Injury Using Neoglycolipid-Spiked Glycovesicles

Shiga toxin (Stx) producing Escherichia coli (STEC) cause the edema disease in pigs by releasing the swine-pathogenic Stx2e subtype as the key virulence factor. Stx2e targets endothelial cells of animal organs including the kidney harboring the Stx receptor glycosphingolipids (GSLs) globotriaosylceramide (Gb3Cer, Galα1-4Galβ1-4Glcβ1-1Cer) and globotetraosylceramide (Gb4Cer, GalNAcβ1-3Galα1-4Galβ1-4Glcβ1-1Cer). Since the involvement of renal epithelial cells in the edema disease is unknown, in this study, we analyzed the porcine kidney epithelial cell lines, LLC-PK1 and PK-15, regarding the presence of Stx-binding GSLs, their sensitivity towards Stx2e, and the inhibitory potential of Gb3- and Gb4-neoglycolipids, carrying phosphatidylethanolamine (PE) as the lipid anchor, towards Stx2e. Immunochemical and mass spectrometric analysis revealed various Gb3Cer and Gb4Cer lipoforms as the dominant Stx-binding GSLs in both LLC-PK1 and PK-15 cells. A dihexosylceramide with proposed Galα1-4Gal-sequence (Gal₂Cer) was detected in PK-15 cells, whereas LLC-PK1 cells lacked this compound. Both cell lines were susceptible towards Stx2e with LLC-PK1 representing an extremely Stx2e-sensitive cell line. Gb3-PE and Gb4-PE applied as glycovesicles significantly reduced the cytotoxic activity of Stx2e towards LLC-PK1 cells, whereas only Gb4-PE exhibited some protection against Stx2e for PK-15 cells. This is the first report identifying Stx2e receptors of porcine kidney epithelial cells and providing first data on their Stx2e-mediated damage suggesting possible involvement in the edema disease.

Shiga toxin-glycosphingolipid interaction: Status quo of research with focus on primary human brain and kidney endothelial cells

Shiga toxin (Stx)-mediated injury of the kidneys and the brain represent the major extraintestinal complications in humans upon infection by enterohemorrhagic Escherichia coli (EHEC). Damage of renal and cerebral endothelial cells is the key event in the pathogenesis of the life-threatening hemolytic uremic syndrome (HUS). Stxs are AB₅ toxins and the B-pentamers of the two clinically important Stx subtypes Stx1a and Stx2a preferentially bind to the glycosphingolipid globotriaosylceramide (Gb3Cer, Galα4Galβ4Glcβ1Cer) and to less extent to globotetraosylceramide (Gb4Cer, GalNAcβ3Galα4Galβ4Glcβ1), which are expected to reside in lipid rafts in the plasma membrane of the human endothelium. This review summarizes the current knowledge on the Stx glycosphingolipid receptors and their lipid membrane ensemble in primary human brain microvascular endothelial cells (pHBMECs) and primary human renal glomerular endothelial cells (pHRGECs). Increasing knowledge on the precise initial molecular mechanisms by which Stxs interact with cellular targets will help to develop specific therapeutics and/or preventive measures to combat EHEC-caused diseases.

Combining Mass Spectrometry, Surface Acoustic Wave Interaction Analysis, and Cell Viability Assays for Characterization of Shiga Toxin Subtypes of Pathogenic Escherichia coli Bacteria

Shiga toxin (Stx)-producing Escherichia coli (STEC) and enterohemorrhagic E. coli (EHEC) as a human pathogenic subgroup of STEC are characterized by releasing Stx AB₅-toxin as the major virulence factor. Worldwide disseminated EHEC strains cause sporadic infections and outbreaks in the human population and swine pathogenic STEC strains represent greatly feared pathogens in pig breeding and fattening plants. Among the various Stx subtypes, Stx1a and Stx2a are of eminent clinical importance in human infections being associated with life-threatening hemorrhagic colitis and hemolytic uremic syndrome, whereas Stx2e subtype is associated with porcine edema disease with a generalized fatal outcome for the animals. Binding toward the glycosphingolipid globotriaosylceramide (Gb3Cer) is a common feature of all Stx subtypes analyzed so far. Here, we report on the development of a matched strategy combining (i) miniaturized one-step affinity purification of native Stx subtypes from culture supernatant of bacterial wild-type strains using Gb3-functionalized magnetic beads, (ii) structural analysis and identification of Stx holotoxins by electrospray ionization ion mobility mass spectrometry (ESI MS), (iii) functional Stx-receptor real-time interaction analysis employing the surface acoustic wave (SAW) technology, and (iv) Vero cell culture assays for determining Stx-caused cytotoxic effects. Structural investigations revealed diagnostic tryptic peptide ions for purified Stx1a, Stx2a, and Stx2e, respectively, and functional analysis resulted in characteristic binding kinetics of each Stx subtype. Cytotoxicity studies revealed differing toxin-mediated cell damage ranked with Stx1a > Stx2a > Stx2e. Collectively, this matched procedure represents a promising clinical application for the characterization of life-endangering Stx subtypes at the protein level.

Membrane assembly of Shiga toxin glycosphingolipid receptors and toxin refractiveness of MDCK II epithelial cells

Shiga toxins (Stxs) are the major virulence factors of Stx-producing Escherichia coli (STEC), which cause hemorrhagic colitis and severe extraintestinal complications due to injury of renal endothelial cells, resulting in kidney failure. Since kidney epithelial cells are suggested additional targets for Stxs, we analyzed Madin-Darby canine kidney (MDCK) II epithelial cells for presence of Stx-binding glycosphingolipids (GSLs), determined their distribution to detergent-resistant membranes (DRMs), and ascertained the lipid composition of DRM and non-DRM preparations. Globotriaosylceramide and globotetraosylceramide, known as receptors for Stx1a, Stx2a, and Stx2e, and Forssman GSL as a specific receptor for Stx2e, were found to cooccur with SM and cholesterol in DRMs of MDCK II cells, which was shown using TLC overlay assay detection combined with mass spectrometry. The various lipoforms of GSLs were found to mainly harbor ceramide moieties composed of sphingosine (d18:1) and C24:1/C24:0 or C16:0 FA. The cells were highly refractory toward Stx1a, Stx2a, and Stx2e, most likely due to the absence of Stx-binding GSLs in the apical plasma membrane determined by immunofluorescence confocal laser scanning microscopy. The results suggest that the cellular content of Stx receptor GSLs and their biochemical detection in DRM preparations alone are inadequate to predict cellular sensitivity toward Stxs.

Colocalization of receptors for Shiga toxins with lipid rafts in primary human renal glomerular endothelial cells and influence of D-PDMP on synthesis and distribution of glycosphingolipid receptors

Damage of human renal glomerular endothelial cells (HRGECs) of the kidney represents the linchpin in the pathogenesis of the hemolytic uremic syndrome caused by Shiga toxins of enterohemorrhagic Escherichia coli (EHEC). We performed a comprehensive structural analysis of the Stx-receptor glycosphingolipids (GSLs) globotriaosylceramide (Gb3Cer, Galα4Galβ4Glcβ1Cer) and globotetraosylceramide (Gb4Cer, GalNAcβ3Galα4Galβ4Glcβ1Cer) and their distribution in lipid raft analog detergent-resistant membranes (DRMs) and nonDRMs prepared from primary HRGECs. Predominant receptor lipoforms were Gb3Cer and Gb4Cer with Cer (d18:1, C16:0), Cer (d18:1, C22:0) and Cer (d18:1, C24:1/C24:0). Stx-receptor GSLs co-distribute with sphingomyelin (SM) and cholesterol as well as flotillin-2 in DRMs, representing the liquid-ordered membrane phase and indicating lipid raft association. Lyso-phosphatidylcholine (lyso-PC) was identified as a nonDRM marker phospholipid of the liquid-disordered membrane phase. Exposure of primary HRGECs to the ceramide analogon d-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP) reduced total Gb3Cer and Gb4Cer content, roughly calculated from two biological replicates, down to half and quarter of its primordial content, respectively, but strengthened their prevalence and cholesterol preponderance in DRMs. At the same time, the distribution of PC, SM and lyso-PC to subcellular membrane fractions remained unaffected by D-PDMP treatment. Defining the GSL composition and precise microdomain structures of primary HRGECs may help to develop novel therapeutic options to combat life-threatening EHEC infections.

Shiga toxin glycosphingolipid receptors and their lipid membrane ensemble in primary human blood-brain barrier endothelial cells

Shiga toxin (Stx)-mediated injury to microvascular endothelial cells in the brain significantly contributes to the pathogenesis of the hemolytic-uremic syndrome caused by enterohemorrhagic Escherichia coli (EHEC). Stxs are AB₅ toxins and the B-pentamers of the two major Stx subtypes Stx1a and Stx2a preferentially bind to the glycosphingolipid (GSL) globotriaosylceramide (Gb3Cer) expressed by human endothelial cells. Here we report on comprehensive structural analysis of the different lipoforms of Gb3Cer (Galα4Galβ4Glcβ1Cer) and globotetraosylceramide (Gb4Cer, GalNAcβ3Galα4Galβ4Glcβ1Cer, the less effective Stx receptor) of primary human brain microvascular endothelial cells and their association with lipid rafts. Detergent-resistant membranes (DRMs), obtained by sucrose density gradient ultracentrifugation, were used as lipid raft-analogous microdomains of the liquid-ordered phase and nonDRM fractions were employed as equivalents for the liquid-disordered phase of cell membranes. Structures of the prevalent lipoforms of Gb3Cer and Gb4Cer were those with Cer (d18:1, C16:0), Cer (d18:1, C22:0) and Cer (d18:1, C24:1/C24:0) determined by electrospray ionization mass spectrometry that was combined with thin-layer chromatography immunodetection using anti-Gb3Cer and anti-Gb4Cer antibodies as well as Stx1a and Stx2a subtypes. Association of Stx receptor GSLs was determined by co-localization with lipid raft-specific membrane protein flotillin-2 and canonical lipid raft marker sphingomyelin with Cer (d18:1, C16:0) and Cer (d18:1, C24:1/C24:0) in the liquid-ordered phase, whereas lyso-phosphatidylcholine was detectable exclusively in the liquid-disordered phase. Defining the precise microdomain structures of primary endothelial cells may help to unravel the initial mechanisms by which Stxs interact with their target cells and will help to develop novel preventive and therapeutic measures for EHEC-mediated diseases.

Shiga toxin glycosphingolipid receptors of Vero-B4 kidney epithelial cells and their membrane microdomain lipid environment

Shiga toxins (Stxs) are produced by enterohemorrhagic Escherichia coli (EHEC), which cause human infections with an often fatal outcome. Vero cell lines, derived from African green monkey kidney, represent the gold standard for determining the cytotoxic effects of Stxs. Despite their global use, knowledge about the exact structures of the Stx receptor glycosphingolipids (GSLs) and their assembly in lipid rafts is poor. Here we present a comprehensive structural analysis of Stx receptor GSLs and their distribution to detergent-resistant membranes (DRMs), which were prepared from Vero-B4 cells and used as lipid raft equivalents. We identified globotriaosylceramide (Gb3Cer) and globotetraosylceramide (Gb4Cer) as the GSL receptors for Stx1a, Stx2a, and Stx2e subtypes using TLC overlay detection combined with MS. The uncommon Stx receptor, globopentaosylceramide (Gb5Cer, Galβ3GalNAcβ3Galα4Galβ4Glcβ1Cer), which was specifically recognized (in addition to Gb3Cer and Gb4Cer) by Stx2e, was fully structurally characterized. Lipoforms of Stx receptor GSLs were found to mainly harbor ceramide moieties composed of sphingosine (d18:1) and C24:0/C24:1 or C16:0 fatty acid. Moreover, co-occurrence with lipid raft markers, SM and cholesterol, in DRMs suggested GSL association with membrane microdomains. This study provides the basis for further exploring the functional impact of lipid raft-associated Stx receptors for toxin-mediated injury of Vero-B4 cells.

Comparison of three chromogenic media and enrichment broth media for the detection of methicillin-resistant Staphylococcus aureus from mucocutaneous screening specimens : Comparison of MRSA chromogenic media

This study compares the performance of three chromogenic culture agar plates, chromID MRSA, MRSA-Screen and MRSA-Select, by challenging with a collection of Staphylococcus aureus strains and screening samples obtained from hospitalised patients. All chromogenic media showed excellent sensitivity (>95%) and specificity after 18 h on the methicillin-resistant Staphylococcus aureus (MRSA) collection strains, but the specificity of MRSA-Screen decreased markedly after 42 h. Sixty-eight of 1,002 screening specimens yielded MRSA on at least one medium. The sensitivity of all media to detecting MRSA after 18 h was <50%, but this increased to 75% (chromID MRSA), 81% (MRSA-Screen) and 72% (MRSA-Select) after 42 h and 85% after enrichment and plating on the same media. The specificity at 18 h was excellent, but was significantly lower for MRSA-Screen after 42 h and enrichment. In conclusion, all media showed equivalent sensitivities after 18 h of incubation and performed better when enriched before inoculation. MRSA-Screen was more sensitive but less specific than the two other media after 42 h of incubation.

Changes in the phosphorylation status of the 27 kDa heat shock protein (HSP27) associated with the modulation of growth and/or differentiation in MCF-7 cells

We have used human mammary cells of the MCF-7 strain, which constitutively express high levels of the small heat shock protein HSP27 and we have compared the changes in the phosphorylation status of this protein together with changes in cell growth and/or morphology induced by the action of one of the following agents: (1) TPA (12-O-tetradecanoylphorbol-13-acetate), known as a differentiation inducer in MCF-7 cells; (2) OH-TAM (hydroxytamoxifen), which exerts a cytostatic and cytotoxic action; or (3) TNF alpha (tumour necrosis factor), which induces apoptotic cell death in this cell line. Our data show that TPA and TNF stimulate an immediate and massive phosphorylation of HSP27, whereas OH-TAM affect the phosphorylation status of the protein only after a 3 day delay. In the case of TPA, high levels of HSP27 phosphorylation were maintained for at least 4 days, along with growth inhibition and acquisition by the cells of a secretory phenotype. TPA and OH-TAM exerted similar immediated effects on cell growth, despite the different time course of their action on HSP27 phosphorylation. This excludes the possibility that the latter is a necessary consequence of, or an absolute requisite to, growth inhibition. With OH-TAM and TNF the increase in HSP27 phosphorylation was concomitant with the appearance of apoptosis, not observed with TPA. This indicates that increased phosphorylation of HSP27 is not specifically associated with the triggering or the execution of apoptosis in these cells. Altogether, our data support the concept that phosphorylated HSP27 is involved (and might then be rate limiting in some instances) in the execution of vital cell programmes (including resistance to stress, proliferation and differentiation), as well as in that of cell death. This is consistent with its role in actin polymerization and its position downstream of the p38/RK-type MAPkinase, itself a point of convergence for diverse signal transduction pathways.

Estrogenic and anti-estrogenic regulation of estrogen receptor in MCF-7 breast-cancer cells: comparison of immunocytochemical data with biochemical measurements

Data from immunocytochemical assessment of estrogen receptor (ER) regulation in MCF-7 cells under estrogenic and anti-estrogenic stimulation were compared with those obtained by enzyme immunoassay (Abbott ER-EIA). Similar trends were observed, although ER level variations were less marked when assessed immunocytochemically. We confirmed reports of ER disappearance in the presence of estrogens (Es; E2 and DES) and pure anti-estrogens (AEs; RU 58,668 and ICI 164,384) as well as its increase with partial AEs (4-OH-TAM and RU 39,119). E2-induced ER down-regulation was partly blocked by actinomycin D (AMD), okadaic acid (OK) and cycloheximide (CHX) when assessed by these 2 methods. Down-regulation by pure AEs was not impeded by CHX, indicating that they operate differently from Es (i.e., transformation of ER to a form sensitive to constitutive degradation activity). In situ pre-labeling of the cells with [3H]TAZ indicated that all investigated ligands eliminate pre-existing ER through binding to newly synthetized receptors, since [3H]TAZ co-valently associates with ER; E2 and RU 58,668 were more effective than 4-OH-TAM in this regard. CHX blocked ER disappearance even in the presence of pure AEs, which is in contrast to the data established with cells not pre-exposed to [3H]TAZ. Nuclear location of [3H]TAZ-ER complexes may explain this discrepancy, since pure AE-ER complexes were reported to be incapable of nuclear translocation.

New biocompatible cationic amphiphiles derivative from glycine betaine: a novel family of efficient nonviral gene transfer agents

With the aim of developing new efficient agents for transfecting of eukaryotic cells we have designed and synthesized a novel family of cationic lipid vectors derived from glycine betaine. In this study we present three novel molecules differing by the length of their aliphatic chains (R=12,R=14,R=16). The lyotropic properties of these cationic lipids have been determined, and their transfection efficiency on different cell lines evaluated, using a luminescent assay. Two of these compounds, GB14 and GB12 are efficient in vitro experiments. Cytoxicity evaluation of these new molecules showed promising results with a low cytotoxicity, especially when co-lipids were included in the formulation. These compounds represent a new family of gene transfer vectors which display good transfection efficiency and low toxicity, possibly due to the natural properties of glycine betaine. These compounds have great potential for the future development of in vivo gene transfer protocols.

Length increase of the side chain of idoxifene does not improve its antagonistic potency in breast-cancer cell lines

Linkage of specific residues onto steroidal estrogens through a long aliphatic side chain leads to "pure antiestrogens" devoid of residual estrogenic activity. Therefore, we assessed whether an increase in the length of the side chain of the triphenylethylenic antiestrogen idoxifene might increase its antagonistic potency. Culture of MCF-7 and tamoxifen-resistant variant RTX6 cells in the presence of CB 7675, a (CH2)8 derivative of idoxifene [(CH2)2], ruled out this possibility. This compound partly blocked MCF-7 cell growth only at 10(-6) M to almost the same extent as tamoxifen and failed to inhibit the growth of RTX6 cells, whereas the pure antiestrogen RU 58 668 was effective on both cell lines at much lower concentration. This absence of improvement was reflected in the observation of an efficiency for down-regulating progesterone receptor no better than that of tamoxifen. Pure antiestrogens are known to down-regulate the estrogen receptor, whereas triphenylethylenic antiestrogens up-regulate the receptor; CB 7675 behaves as the latter in agreement with its lack of strong antagonistic activity.

Estrogen receptor-negative/progesterone receptor-positive Evsa-T mammary tumor cells: a model for assessing the biological property of this peculiar phenotype of breast cancers

In 1986 we reported the appearance of a progestin binding protein in the human breast cancer cell line Evsa-T, originally described as lacking both estrogen and progesterone receptors (ER and PR). In this report we show that PR of this cell line displays a binding affinity for [3H]ORG 2058 and a sucrose gradient sedimentation profile similar to those ascribed to PR from MCF-7 or T47D breast cancer cell lines. PR from Evsa-T cells is down-regulated by the progestin R-5020 as well as by the two antiprogestins, ZK 112.993 and ZK 98.299, but does not confer growth sensitivity to these compounds. ER remains undetectable by ligand binding assay, enzyme immunoassay and northern blotting. Our Evsa-T clone could be a valuable model for assessing the mechanisms leading the ER-/PR+ phenotype occurring occasionally in breast cancers and frequently in meningiomas.

Tamoxifen-induced estrogen receptor up-regulation in mammary tumor cells is not related to growth inhibition

Treatment of estrogen receptor (ER)-positive mammary tumors with tamoxifen produces a dramatic accumulation of ER in the cell nucleus. We investigated whether this phenomenon might be related to the antitumor activity of the drug. Five tamoxifen derivatives for which an influence on MCF-7 cell growth had previously been established were tested for that purpose; two of them inhibited growth, one was growth-stimulatory, and the remaining two were without significant effect. At 1 microM all compounds up-regulated ER in the cell nucleus after 3 days of culture, suggesting that the ER accumulation does not predict the response to tamoxifen treatment. An analysis of a tamoxifen-resistant clone (RT x 6 cells) under similar experimental conditions led to the same conclusion: the ER level significantly increased in the presence of tamoxifen and its 4-hydroxy metabolite.

Brominated detergents as tools to study protein-detergent interactions

In order to study protein-detergent short-range interactions, we analyzed the quenching by brominated detergents of reticulum sarcoplasmic (SR) Ca(2+)-ATPase intrinsic fluorescence. For this purpose, 7,8-dibromododecyl beta-maltoside and 2-O-(10,11-dibromoundecanoyl)sucrose, brominated analogs of two non-ionic detergents, the frequently used dodecylmaltoside and the newly synthesized 2-O-lauroylsucrose respectively, were prepared. Rayleigh scattering measurements showed that the brominated detergents efficiently and rapidly solubilized SR vesicles like their non-brominated analogs although at slightly higher concentrations. Similarly, each analog had a slightly higher critical micellar concentration than its parent detergent. The partition coefficient K (expressed as the ratio of the molar fraction of detergent in the SR lipid phase to that in the aqueous phase, at pH 7.5 and 20 degrees C) was similar for brominated and non-brominated dodecyl maltoside (3.5-4 x 10(5)) and slightly lower for dibromoundecanoylsucrose (approximately 10(5)) than for lauroylsucrose (approximately 2 x 10(5)). At detergent concentrations too low to solubilize the membrane, the brominated detergents rapidly inserted (within seconds) into SR vesicles. In this concentration range, Ca(2+)-ATPase fluorescence quenching steadily increased with detergent concentration. When the membrane was saturated with detergent, the residual fluorescence was about half of its initial value, indicating significant protein-detergent, contacts, possibly due to a slightly higher affinity of Ca(2+)-ATPase for these detergents than for phospholipids. For higher detergent concentrations, solubilizing the membrane, the fluorescence continued to decrease with detergent concentration, with no evidence for a dramatic change in the average hydrophobic environment of the protein during the transition from bilayers to a soluble state. For still higher detergent concentrations, above that necessary for membrane solubilization, the fluorescence was further quenched to a residual relative value of about 20%, corresponding to further delipidation of the protein surface, in agreement with previous results [de Foresta, B., le Maire, M., Orlowski, S., Champeil, P., Lund, S., Møller, J.V., Michelangeli, F. & Lee, A.G. (1989) Biochemistry 28, 2558-2567]. Fluorescence quenching for solubilized Ca(2+)-ATPase was quickly reversed upon addition of excess non-brominated detergent. The effects of the four detergents on the Ca(2+)-ATPase hydrolysis of p-nitrophenyl phosphate were similar and correlated with the protein-detergent contacts evidenced above. In conclusion, both these brominated detergents appear to be promising tools to study protein-detergent interactions at the hydrophobic surface of a membrane protein, either in a membrane or in solubilized complexes.

Estrogenic and antiestrogenic regulation of the half-life of covalently labeled estrogen receptor in MCF-7 breast cancer cells

Effect of estrogens and antiestrogens (AEs) on estrogen receptor (ER) half-life was analyzed in MCF-7 cells by assessing its progressive disappearance after covalent labeling in situ with [3H]tamoxifen aziridine ([3H]TAZ). Cells were incubated for 1 h with 20 nM [3H]TAZ either in the absence or presence of a 500-fold excess of unlabeled estradiol (E2) (non-specific binding). The entire ER population was labeled by this method as established by subsequent incubation of the cells with [125I]E2. [3H]TAZ labeled cells were maintained in culture for additional 5 h in the absence (control) or presence of increasing amounts (0.1 nM - 1 microM) of either a given estrogen (E2, estrone, diethylstilbestrol, bisphenol), a pure AE (RU 58 668, ICI 164 384) or an AE with residual estrogenic activity (RU 39 411, 4-hydroxytamoxifen, keoxifene). The progressive disappearance of nuclear and cytosolic [3H]TAZ-ER complex during 5 h incubation were assessed by their immunoprecipitation with anti-ER monoclonal antibody (H 222) followed by scintillation counting or SDS-PAGE and fluorography. Fading of labeled receptors was extremely slow (approximately 10% loss after 6 h) in absence of any hormone/antihormone indicating a long half-life of the [3H]TAZ-ER complex. Addition of estrogens as well as pure AEs led to a dramatic reduction of the half-life while AEs with residual estrogenic activity were extremely less efficient in this regard providing an explanation for the ability of latter compounds to up-regulate the receptor since they do not affect ER mRNA synthesis and stability. Receptor disappearance induced by estrogens was closely related to their binding affinity for ER. Newly synthesized ER emerged during the treatment with hormones or antihormones seems to be implicated in the phenomenon since [3H]TAZ was covalently bound and could, therefore, not be displaced by these compounds. Induction of synthesis of a short half-life peptide(s) with degradative activity was demonstrated by addition of cycloheximide or puromycine (both at 50 microM) which completely blocked ER disappearance. The fact that no cleavage products of ER were detected by SDS-PAGE suggested a lysosomial hydrolysis. Hence, hormonal modulation of only a part of ERs may down-regulate their total population until it reaches the steady-state level.

Antiestrogenic activity of two 11 beta-estradiol derivatives on MCF-7 breast cancer cells

Two 11 beta-derivatives of estradiol (E2) were tested for their potential antiestrogenic activity in the MCF-7 breast cancer model: one contained a phenoxydimethylaminoethyl side-chain (RU 39,411), the other a pentafluoropentylsulfinyl side-chain (RU 58,668). The former compound displayed mixed estrogenic/antiestrogenic properties, while the latter indicated only an antiestrogenic activity. Both the compounds produced a growth inhibition of MCF-7 cells at doses related to their binding affinity for the estrogen receptor (ER); E2 suppressed this inhibition. The compounds also down-regulated the estrogen binding capacity of the cells but failed to reduce ER mRNA levels, indicating that the grafting of their side-chains prevented this antagonistic effect usually observed with steroidal estrogens. Assessment of ER levels by enzyme immunoassay revealed a marked increase with RU 39,411 and a decrease with RU 58,668; different mechanisms of action should, therefore, be considered. Finally, the estrogenic activity of RU 39,411 was demonstrated by its strong ability to induce synthesis of the progesterone receptor; RU 58,668 failed to display this agonistic activity.

Evaluation of estrogen receptor, antiestrogen binding sites and calmodulin for antiestrogen resistance of two clones derived from the MCF-7 breast cancer cell line

Estrogen receptor (ER), antiestrogen binding sites (AEBS) and calmodulin (CaM) are potential targets of antiestrogen (AE) action. To analyse further which of these targets are primarily involved in the antiproliferative activity of these drugs against human breast cancers, two cell clones, namely the RTx6 and LY-2 variants, selected from MCF-7 cells for their resistance to high doses of tamoxifen (TAM) and the Keoxifen (KEO) analog LY 117018, respectively, were studied for their sensitivity to hydroxytamoxifen (OH-TAM) and KEO as well as the strong calmodulin antagonist calmidazolium. The effects of these drugs on both cell growth and progesterone receptor (PgR) concentration were assessed. Binding properties for ER, AEBS and CaM of each compound were also measured. Our results confirmed that basal growth of RTx6 and LY-2 cells was more resistant to OH-TAM and KEO than parent MCF-7 cells, although both displayed a significant inhibition at the highest doses assessed. In regard to calmidazolium inhibition, each variant behaved as did the MCF-7 line indicating that a modification at the CaM level was not responsible for their lower sensitivity to AEs. Nor could the association of CaM to ER which did not differ among all cell lines. Resistance of these variants was not related to AEBS in view of the total lack of such sites in RTx6 cells. However, under estrogenic growth stimulation such sites may play some role, since LY-2 cells in the presence of estradiol displayed a real antiestrogen-resistant pattern while RTx6 cells were more sensitive than MCF-7 cells to OH-TAM. This property was not found in the antagonism against estradiol-induced PgR synthesis which was observed with each variant. Thus the PgR concentration of RTx6 cells was strongly down-regulated by OH-TAM and KEO and reduced in LY-2 cells to the same extent as in MCF-7 cells. All these observations show that AE resistance is not entirely related to ER mediated events and that alterations at the ER and CaM levels are unlikely to account for the lower AE sensitivity of the variants investigated.

Estradiol-induced down-regulation of estrogen receptor. Effect of various modulators of protein synthesis and expression

Incubation of MCF-7 cells with estradiol (E2) down-regulates estrogen receptor (ER) resulting in a progressive reduction of the capacity of cells to concentrate selectively [3H]E2. Scatchard plot analysis failed to detect any transformation of residual receptors into peptides of lower binding affinity. [3H]Estrone gave an identical ER disappearance pattern with an ER half-life comprised between 2 and 3 h. A similar value was established by incubating the cells with [3H]tamoxifenaziridine ([3H]TAZ) for 1 h before the addition of excessive unlabeled E2 which induced ER-down regulation and impeded any further labeling of the residual receptors. Submission of the [3H]TAZ labeled cell extracts to SDS-PAGE revealed no progressive emergence of low molecular weight cleavage products of the receptor (< 67 kDa). Two inhibitors of protein kinases, H-7 at 40 microM and H-89 at 20 microM, failed to block the E2-induced ER down-regulation. On the contrary, the protein phosphatases 1 and 2A inhibitor, okadaic acid, was effective with concentrations higher than 0.1 microM indicating that a dephosphorylation mechanism was involved in this phenomenon. Cycloheximide (CHX) also significantly reduced the receptor decrease at concentrations higher than 1 microM. G-C specific intercalating agents [actinomycin D (AMD) and chromomycin A3 at 1 microM] also prevented ER disappearance; ethidium bromide (EB) and quinacrine were ineffective. AMD and CHX operated immediately after their addition to the medium indicating an inhibitory action on the synthesis of an RNA and/or a peptide with high turnover rate involved in ER decline. Moreover, AMD produced its suppressive effects under conditions impeding any labeling of newly synthetized receptors (i.e. [3H]TAZ with an excess of unlabeled E2) rejecting the possibility of an increasing ER production which may partially hamper its disappearance. Finally, E2-induced ER mRNA down-regulation was similarly abolished by AMD while EB and CHX were devoid of effect.

Growth factor-like activity of phenol red preparations in the MCF-7 breast cancer cell line

Hormonal responsiveness of the estrogen-sensitive MCF-7 human breast cancer cell line is known to vary between laboratories although the causes and implications of these variations remain unclear. Our findings lead us to conclude that the pH indicator phenol red (PHR) has growth factor-like effects in addition to its well known estrogen-like effects. To demonstrate this hypothesis, we have assessed the importance of PHR either in the absence or in the presence of the estrogens contained in the serum added to the culture medium. The basal growth rate of MCF-7 cells was significantly reduced by short-term or long-term withdrawal of PHR. The stimulatory effects of estradiol and the inhibitory effects of the antiestrogen 2-CH3,4-OH-tamoxifen (MHT) were not significantly affected by long-term withdrawal of the dye. Moreover, long-term cell maintenance without PHR alone or in complete estrogen-depleted medium did not change their basal steroid receptor content. The molecular structure of the estrogen receptor which is usually modified under estrogenic stimulation remained identical whether or not the cells were maintained in the presence of the dye. Maintaining cells without the dye in the presence of serum estrogens led to the death of the cell line after 50 transfers. Lastly, addition of PHR had clearcut growth stimulatory effects on the hormono-independent cell line Evsa-T.

Accumulation of a non-binding form of estrogen receptor in MCF-7 cells under hydroxytamoxifen treatment

It is well known that MCF-7 cells, when incubated with hydroxytamoxifen (OH-Tam) loose their capacity to bind [3H]estradiol. By using Western blotting and [3H]tamoxifen aziridine labeling of KCl extracts from these cells we found that this loss in binding capacity was not associated with a disappearance of the estrogen receptor (ER) protein, an event known to occur after incubation with estradiol. Attempts to label under exchange conditions these ER molecules, which, on the basis of enzyme immunoassays appear to accumulate under OH-Tam treatment, were unsuccessful. Cell fractionation suggested that their origin is nuclear. Assessment of a few triphenylethylenic antiestrogens, as far as their inhibitory potency towards the in vitro MCF-7 cell growth is concerned, indicated a correlation between accumulation of these non-binding ER molecules and the antiestrogen antiproliferative action. However, we were unable to demonstrate absence of such an ER accumulation in two tamoxifen-resistant variants. Impaired folding of the ER protein or impaired phosphorylation of its hormone-binding domain are attractive hypotheses to account for these non-binding ER molecules. Whether these ER molecules have any physiological role, such as competition with the "normal" receptor molecules for the estrogen responsive elements on the DNA is unknown and deserves further study.

Hormone sensitivity in vitro and in vivo of v-ras-transfected MCF-7 cell derivatives

Human mammary carcinoma cell lines (MCF-7) were analysed for their hormone sensitivity before and after transfection with a v-Ha-ras oncogene or with a neomycin-resistance gene followed by selection in vitro or in vivo. Our aim was to test how the expression of the ras oncogene would influence the estradiol sensitivity of MCF-7 cells. In culture, MCF-7 cells expressing the viral p21 oncogene product, as compared to parental MCF-7 cells and their control derivatives, showed lower levels of a 67-kDa estrogen receptor. Progesterone receptors, however, remained sensitive to up-regulation by estrogens. The oncogene-expressing cells were less sensitive than all controls to stimulation of proliferation by 10(-8)M estradiol or to inhibition of proliferation by 2-CH3-4-OH tamoxifen, and this was not dependent upon the type of culture medium used. After s.c. or i.p. injection into female athymic nude mice, ovariectomized or left intact, the growth of MCF-7 cells expressing the ras oncogene product and of all control cells was sensitive to stimulation by estrogen supplementation. Conversely, cell lines derived from tumors generated with long latency in untreated athymic nude mice by v-ras-expressing MCF-7 cells showed efficient formation of quickly growing tumors in the absence of estrogen supplementation. No differences were observed in invasion and metastasis of the different MCF-7 cell types injected into athymic nude mice that were supplemented with estrogens or not.

Derivatives of tamoxifen. Dependence of antiestrogenicity on the 4-substituent

A range of tamoxifen derivatives substituted in the 4-position of the 1-phenyl ring are described. The key steps in the synthesis of 4-iodo-, 4-bromo-, and 4-(methylthio)tamoxifen were reactions of 1,2-diarylbutanones with the (4-halogenophenyl)lithium or [4-(methylthio)phenyl]magnesium bromide. Oxidized precursors of 4-(methylthio)tamoxifen were used to prepare the methylsulfinyl and methylsulfonyl derivatives. Further derivatives (formyl, hydroxymethyl, oxirane, mercapto) were prepared from 4-bromotamoxifen via the 4-lithio derivative. Several of the derivatives (Br, I, SMe, SOMe, SO2Me, oxirane, CHO, CH2OH) displayed a higher affinity for estrogen receptors (ER) of calf uterine cytosol than did tamoxifen, but there was no relationship between affinity to ER and the ability to inhibit the growth of the MCF-7 breast cancer cell line in vitro.

Relation between estrogen receptor concentration and clinical and histological factors: their relative prognostic importance after radical mastectomy for primary breast cancer

After modified radical mastectomy, 490 primary breast cancer patients were followed for a median of 75 months. Bloom grade was measured in 340 patients and ER status in 341. Follow-up of these patients has yielded the following results: (a) The value of traditional indices has been reaffirmed. (Cox's multivariate analysis identified, in order of decreasing importance, the number of invaded lymph nodes, the initial tumor size and the histological grade. Other variables were found to be of lesser importance and were correlated with the three main indices.) (b) The value of ER status disappeared after more than 3 years of follow-up. (c) ER positive patients fared better after recurrence. This was interpreted as being a consequence of their responsiveness to hormonal treatment.

Comparison of biochemical and immunoenzymatic macromethods and a new immunocytochemical micromethod for assaying estrogen receptors in human breast carcinomas

Estrogen receptors (ERs) were assayed in 23 breast carcinomas by: (1) the conventional biochemical assay with dextran-coated charcoal (DCC); (2) the immunoenzymatic assay using a monoclonal antibody (MAb), ER-EIA (Abbott); and (3) an original cytochemical method using another MAb, ER-ICA (Abbott). The first two techniques were performed on biopsy samples, whereas the last was carried out on fine needle aspiration (FNA) samples. The ER contents in aspirates were evaluated by: (1) scaled proportions of colored neoplastic cells; (2) scaled coloration intensity; (3) total grading (= proportion plus intensity); (4) product grading (= proportion times intensity); and (5) a new index (NI) described in this paper. The ER-EIA assay correlated best, with a high statistical significance, with the NI (P less than .001); NI was also the only index that significantly correlated (P less than .05) with the DCC results. The results show that the ER-ICA assay offers the great advantages of being applicable to FNA specimens and of producing rapidly available results. This new technique enriches the panel of MAbs for the diagnosis of adenocarcinomas and offers a new tool for the therapeutic follow-up of breast cancer patients. Our preliminary results suggest that the anti-ER MAbs might be helpful for measuring the hormone dependence of small lesions not assayable by DCC, even under endocrine therapy, thus avoiding false-negative assays.

Estrogen receptor status and estradiol sensitivity of MCF-7 cells in exponential growth phase

Proliferative patterns of MCF-7 human breast cancer cells have been reported to influence their estrogen receptor (ER) contents. However, the experimental conditions under which these variations in ER contents were described differed from those commonly used for maintaining exponential growth. We, therefore, investigated whether or not MCF-7 receptor status also fluctuated under normal growth conditions. MCF-7 cells were cultured up to 4 days in 96-multiwell dishes. On each day, cell number was spectrophotometrically assessed after fixation and coloration of the cells with hematoxylin; corresponding ER content was measured by the Abbott enzyme immunoassay in KCl extracts. At the three plating densities tested (5, 10 and 20 x 10(3) cells/ml), an obvious parallel was found between the cell number and the ER content suggesting an unchanged receptor status throughout the culture period. Regression analysis confirmed this impression. Additional fractionation by SDS-PAGE of total MCF-7 proteins extracted at various times of the culture (up to 7 days in 35 mm Petri dishes) gave identical patterns suggesting that ER synthesis is regulated as the majority of proteins. Growth experiments indicated that this situation conferred a constant estrogenic sensitivity to the cells: 24 h exposure to 10(-8) M estradiol on either the 1st, 2nd, 3rd or 4th day after plating resulted in the same increase in cell number. All these data indicated that ER contents of MCF-7 cells were maintained at a constant level under exponential growth which resulted in a constant estrogenic sensitivity.

Estrogen conjugates and serum factors mediating the estrogenic trophic effect on MCF-7 cell growth

Estrogens stimulate growth of MCF-7 breast cancer cells in monolayer culture. Possible interference of serum factors leading to an estrogen-insensitive cell growth was analyzed in various experiments carried out on serum batches producing no estradiol stimulation. Out of five estrogen conjugates, only 3-glucurono-estradiol partly suppressed the inhibition of hydroxytamoxifen; the conjugate also reduced the estrogen receptor content of the cells, probably by a down regulation process ("processing"). Moreover, prolonged subcultures in dextran-coated charcoal-treated serum attempting to remove possible intracellular estrogens produced no growth stimulation. Interference by hormone carriers of the serum was ruled out by the fact that two strong synthetic estrogens, moxestrol and diethylstilbestrol with weak binding affinity for these carriers, were unstimulatory. Reduction of the carrier concentration also failed to confer any estrogen sensitivity. This lack of effect of most estrogen conjugates and serum carriers seems to contradict the hypothesis of their interference leading to an estrogen-insensitive growth. Presence in the serum of potential inhibitors towards estrogen action was also examined. Dilution of sera inducing an estrogenic stimulated growth failed to show any growth increase, either in the absence or presence of estradiol, thus excluding the possibility of a major influence of an antagonism on growth control. Moreover, clonogenic assays in soft agar eliminated the hypothesis that a difference between "active" (stimulatory with estradiol) and "inactive" serum batches may result from distinct adherence properties rather than from real growth stimulation. All of these data are consistent with the concept that serum factors which are not of estrogenic nature mediate the trophic effect of estradiol; their absence in some serum batches may lead to an estrogen-insensitive cell growth.

In vitro studies of canine mammary tumors: influence of 17-beta-estradiol and progesterone on cell kinetics parameters

Using an in vitro tritiated thymidine nuclear labeling followed by autoradiography, the effects of 17-beta-estradiol (E2) or progesterone (Pg) were studied in 30 canine mammary tumors that were incubated and hormonally stimulated in vitro. In 10 of these tumors, the synthetic (S) phase duration was also measured in absence or in presence of E2, by using a double labeling with tritiated thymidine. Our results demonstrate that E2, and, to a lesser degree, Pg can induce cell replication in both estrogen receptor-positive (ER+ PgR+) and estrogen receptor-negative (ER- PgR-) canine mammary tumors. The mitogenic effect of E2 may involve a shortening of the DNA S cell cycle phase. We have also found a significantly positive relationship between the estrogen and the progesterone receptor concentrations and the basal proliferation rate in these tumors, whereas no correlation was found between steroid receptor contents and the maximal level of stimulation achieved after E2 or Pg exposure.

Induction of progesterone receptor in an estrogen, progesterone receptor-negative breast cancer cell line

In MCF-7 cell culture, some sera endow estradiol-17 beta with strong growth promoting properties ("active" sera) while other fail to display this property ("inactive" sera). Passage from "inactive" to "active" sera are shown here to induce the appearance of a progestin binding capacity in the receptor negative line Evsa-T. Competition with various unlabeled steroids established the specificity of this binding reaction. The induction of progesterone receptor required neither estrogens, nor ER and failed to confer major growth sensitivity to hormonal steroids: only medroxyprogesterone acetate was slightly inhibitory at high concentration. These observations disclose the influence of seric factors independent of estrogens and of ER-related mechanisms on PgR induction.

Clinical significance of the quantitative assessment of estrogen receptors in advanced breast cancer

The predictive value of the estrogen receptor (ER) assay with regard to the response to hormonal treatment was analyzed in women with advanced breast carcinoma. The significance of ten clinical variables of putative prognostic value was also investigated. A total of 49 courses of endocrine therapy were available for study. The respective merits of using the receptor information as a qualitative or a quantitative variable were compared. Linear logistic regression analysis showed that the quantitative information was significantly related to the therapeutic response (P < 0.0001) and proved to be superior to the qualitative information. Compared with the clinical variables tested with the logistic model, receptor concentration was by far the most important single predictor of response. Nevertheless, introduction of two of these clinical variables (i.e., age and menopausal status) into the model in addition to receptor concentration improved its predictive value. Presented in graphic form, the improved model provides a simple means to estimate the probability that a given patient will respond to endocrine therapy. Successive ER assays were available in a series of patients who had received no systemic treatment. In ER+ cases, there was a significant correlation between receptor concentrations in the consecutive assays. There was no influence of the time interval between tissue samplings. Data were also consistent in ER- patients. These results give support to the practice of routine receptor determination in the primary tumor at the time of mastectomy. It is concluded that the distinction between hormone-responsive and hormone-resistant tumors appears artificial. The therapeutic implications of a continuous gradient of hormone-dependency among breast cancers are discussed.

Effects on insulin, prolactin, progesterone, and estradiol on DNA synthesis in organ culture of 7,12-dimethylbenz(a)anthracene-induced rat mammary tumors

The effect of various hormones or hormone combinations on DNA synthesis was investigated in organ cultures of 20 dimethylbenz(a)anthracene-induced rat mammary tumors. Three tumors were insulin independent and were totally insensitive to all other hormones tested. Seventeen tumors were insulin dependent for DNA synthesis and, in the presence of insulin, displayed variable responses to the other hormones. Nine of 12 such tumors were significantly stimulated by the combination of prolactin and progesterone. Given alone, these hormones were effective in only 25% of the tumors tested. Estradiol used at 2 dose levels, 0.001 or 1.0 mug/ml, acted in a reverse manner to progesterone and proved inhibitory in combination with prolactin in 40% of cases. It was ineffective alone except in 1 of 10 cases in which a stimulatory effect was recorded. A comparison in 4 tumors between estimation of DNA synthesis ([3H]thymidine incorporation into DNA) and colchicine-blocked mitoses demonstrated a good concordance. These results are discussed in terms of variations in the degree of hormone responsiveness of individual tumors and of the known hormone-dependent properties of the 7,12-dimethylbenz(a)-anthracene tumors in vivo.

Estradiol-dependent collagenolytic enzyme activity in long-term organ culture of human breast cancer

An organ culture method suitable for the maintenance of viable human breast cancer for at least 14 days has been described. This method was applied to a total of 94 breast cancer specimens. It allowed good survival of "soft" tumors of various histological types, with loose connective stroma even in hormone-free medium. In contrast, "scirrhous" cancers showed poor survival in hormone-free medium; viable cells were maintained only at the very periphery of the explants. Supplementation of the medium with insulin (10 mug/ml), ovine prolactin (5 mug/ml), and hydrocortisone (1 mug/ml) in various combinations seemed to induce enlargement of viable cancer cells and moderate loosening of the stroma in some cases. However, it did not improve the survival of central tumor cords in scirrhous explants. Further supplementation of the medium with 17 beta-estradiol (minimum effective dose, 0.1 to 10 ng/ml), although it did not affect soft tumors, markedly improved survival of the cancer cells of scirrhous tumors throughout the whole explants, with evidence of collagen digestion around the neoplastic cells. This was observed in 18 of 20 scirrhous cancers subjected to this treatment. Estradiol need not be present during the whole culture period; the results at 14 days were identical in explants treated with estradiol for the first 7 days only or for the entire period. Addition of purified collagenase during the first 24 or 48 hr of culture resulted in complete dissolution of the collage. After such treatment, culture under the usual conditions resulted in excellent survival of the explants without improvement from hormone supplementation; thus, while estradiol was necessary when collagen was present, it was not longer required after collagen digestion. It can be concluded that breast cancer cells in organ culture are only slightly, or not at all, hormone dependent for survival, provided that they are not restrained by a dense collagen barrier. The estrogen-induced changes allowing survival inside the scirrhous explants strongly suggest the presence of an estrogen-dependent collagenolytic enzyme system in the collagen-rich breast cancers. This system could represent an important component of the hormone dependency of human breast cancer growth.

Inhibition of DMBA-induced mammary carcinogenesis in the rat by 2-br- -ergocryptine (CB 154), an inhibitor of prolactin secretion, and by nafoxidine (U-11, 100 A), an estrogen antagonist

The DMBA-induced mammary carcinogenesis in the Sprague-Dawley rat is known to be both estrogen and prolactin dependent. The experiments presented here show that 2-Br-&#913;-ergocryptine (CB 154), an inhibitor of prolactin secretion, and nafoxidine (, 100 A), an estrogen antagonist, inhibit the U 11 successive stages of carcinogenesis, namely formation of preneo plastic nodules, transformation of the latter into tumors, and finally growth of the established tumors. Endocrine studies, involving histological examination of organs and serum prolactin determination by radioimmunoassay, show that CB 154 inhibits prolactin secretion and produces peripheral changes consistent with this effect, and that nafoxidine behaves as an antiestrogen in intact animals and in oophorectomized animals given estrogens, that it is devoid of intrinsic estrogenic properties but rather displays progestational-like effects, and that it inhibits prolactin stimulation by estrogens in oophorectomized rats. The antitumor effect of CB 154 can be ascribed to interference with prolactin secretion. That of nafoxidine may result from its antiestrogenic properties at the tumor tissue level, although part of it could be tentatively ascribed to inhibition of prolactin secretion.