Detection and analysis of cancer cells in blood and bone marrow using a rare event imaging system.

An automated rare event detection system (Rare Event Imaging System) is described for the recognition of cancer cells that appear at low frequencies (1 in 1 million) in peripheral blood (PB) or bone marrow (BM). The instrumentation includes an automated fluorescence microscope (Nikon Microphot-FXA) with a cooled charge coupled device camera and a 60-MHz Pentium personal computer. Main features of the system are rapid analysis of large microscopic fields, including a total cell count, detection of fluorescently labeled cells, and a display of digitally stored images of the detected cells. Furthermore, the X,Y coordinates of each identified object are stored and can be recalled for morphological analysis of the cell using higher magnification or different fluorescent filter sets. The preparation of the blood or BM samples for automated analysis consists of lysis of the RBCs, attachment of sample cells onto adhesion slides, fixation, and fluorescent labeling with anticytokeratin antibodies. Cytokeratin-positive cells, however, were detected in 17% of the samples from healthy blood donors using this procedure (mean number, approximately 7/10(6) mononuclear cells in positive samples). To improve the specificity of the rare event detection, a double-labeling protocol combining intracellular cytokeratin with epithelial cell adhesion molecule (Ep-CAM) (breast, ovarian, colon, and lung carcinoma antigen) or disialo-ganglioside (GD2) antigen (small cell lung carcinoma, neuroblastoma, melanoma antigen) was developed. Examples of doubly labeled cultured cells and cancer cells from breast and small cell lung cancer patients are shown. Using the double-labeling protocol, no "positive" cells were seen in samples of healthy blood donors. Automated rare event detection (cytokeratin single-staining) was applied to 355 PB, BM, and stem cell (SC) samples from breast cancer patients before autologous BM transplantation. Cytokeratin-positive cells were found in 52% of BM, 35% of PB, and 27% of SC samples at frequencies of 1-1020 positive cells/10(6) mononuclear cells, thereby establishing the efficacy of the technique in the detection of rare cancer cells in hematopoietic tissue samples of cancer patients.

HRad17 colocalizes with NHP2L1 in the nucleolus and redistributes after UV irradiation.

The rad17 gene of Schizosaccharomyces pombe plays an important role as a checkpoint protein following DNA damage and during DNA replication. The human homologue of S. pombe rad17, Hrad17, was recently identified, but its function has not yet been established. Using the yeast two-hybrid system, we determined that HRad17 can interact with a nucleolar protein, NHP2L1. This interaction was also demonstrated biochemically, in human cells. Immunofluorescence studies revealed that HRad17 and NHP2L1 colocalize to the nucleolus, and immunogold labeling further resolved the location of NHP2L1 to the dense fibrillar component of the nucleolus. Interestingly, the localization of HRad17 in the nucleolus was altered in response to UV irradiation. These results provide some insight into the DNA damage and replication checkpoint mechanisms of HRad17.

Molecular cloning and characterization of human trabeculin-alpha, a giant protein defining a new family of actin-binding proteins.

We describe the molecular cloning and characterization of a novel giant human cytoplasmic protein, trabeculin-alpha (M(r) = 614,000). Analysis of the deduced amino acid sequence reveals homologies with several putative functional domains, including a pair of alpha-actinin-like actin binding domains; regions of homology to plakins at either end of the giant polypeptide; 29 copies of a spectrin-like motif in the central region of the protein; two potential Ca(2+)-binding EF-hand motifs; and a Ser-rich region containing a repeated GSRX motif. With similarities to both plakins and spectrins, trabeculin-alpha appears to have evolved as a hybrid of these two families of proteins. The functionality of the actin binding domains located near the N terminus was confirmed with an F-actin binding assay using glutathione S-transferase fusion proteins comprising amino acids 9-486 of the deduced peptide. Northern and Western blotting and immunofluorescence studies suggest that trabeculin is ubiquitously expressed and is distributed throughout the cytoplasm, though the protein was found to be greatly up-regulated upon differentiation of myoblasts into myotubes. Finally, the presence of cDNAs similar to, yet distinct from, trabeculin-alpha in both human and mouse suggests that trabeculins may form a new subfamily of giant actin-binding/cytoskeletal cross-linking proteins.

Posttranslational modifications of cardiac and skeletal muscle proteins by reactive oxygen species after burn injury in the rat.

OBJECTIVE: To determine the involvement of oxidative damage in muscle wasting after burn injury. SUMMARY BACKGROUND DATA: Burn injury damages tissue at the site of the burn and also affects peripheral tissue. There is evidence to suggest that reactive oxygen species may be generated in increased amounts after burn, and these may contribute to wound healing and to posttranslational modifications of tissue constituents distant from the wound site. METHODS: The oxidation of muscle proteins was assessed, using the dinitrophenylhydrazine assay for carbonyl content, in muscles of rats after a full-thickness skin scald burn covering 20% of the total body surface area, over a 6-week period. In this model, rats failed to incur normal body weight or muscle weight gain. RESULTS: Soleus, extensor digitorum longus, diaphragm, and heart ventricle proteins were oxidatively damaged after injury. The extent of tissue protein oxidation, however, differed depending on the time points studied. In general, higher levels of protein carbonyl group formation, an indicator of oxidative damage, were found to occur within 1 to 5 days after injury, and the oxidized protein content of the various tissues decreased during the later stages. Both sarcoplasmic and myofibrillar carbonyl-containing proteins accumulated in diaphragm 3 days after burn injury and were rapidly removed from the tissue during a 2-hour in vitro incubation. This coincided with increased proteolytic activity in diaphragm. CONCLUSIONS: These observations suggest that the loss of proteins modified by reactive oxygen species may contribute to the burn-induced protein wasting in respiratory and other muscles by a proteolytically driven mechanism.

Structural and functional analysis of mouse Msx1 gene promoter: sequence conservation with human MSX1 promoter points at potential regulatory elements.

Vertebrate Msx genes are related to one of the most divergent homeobox genes of Drosophila, the muscle segment homeobox (msh) gene, and are expressed in a well-defined pattern at sites of tissue interactions. This pattern of expression is conserved in vertebrates as diverse as quail, zebrafish, and mouse in a range of sites including neural crest, appendages, and craniofacial structures. In the present work, we performed structural and functional analyses in order to identify potential cis-acting elements that may be regulating Msx1 gene expression. To this end, a 4.9-kb segment of the 5'-flanking region was sequenced and analyzed for transcription-factor binding sites. Four regions showing a high concentration of these sites were identified. Transfection assays with fragments of regulatory sequences driving the expression of the bacterial lacZ reporter gene showed that a region of 4 kb upstream of the transcription start site contains positive and negative elements responsible for controlling gene expression. Interestingly, a fragment of 130 bp seems to contain the minimal elements necessary for gene expression, as its removal completely abolishes gene expression in cultured cells. These results are reinforced by comparison of this region with the human Msx1 gene promoter, which shows extensive conservation, including many consensus binding sites, suggesting a regulatory role for them.

Activation of the ubiquitin pathway in rat skeletal muscle by catabolic doses of glucocorticoids.

To evaluate whether catabolic levels of glucocorticoids activate the ubiquitin pathway in conjunction with their known proteolytic effect in skeletal muscle, rats were injected daily with corticosterone (CTC; 10 mg/100 g body wt) for 7 days. Two peaks of urinary excretion of 3-methylhistidine (3-MH), a specific marker of myofibrillar proteolysis, were observed at days 1 and 3 (165 and 295% of controls, respectively). Levels of ubiquitin pathway mRNAs in skeletal muscle were assessed around the 3-MH peaks. In the extensor digitorum longus, a first rise of two polyubiquitin (pUb) mRNAs was seen at day 1 (183 and 162% of control for the UbB and UbC transcripts, respectively, P < 0.01). An accumulation of both E2-14k mRNAs (140%, P < 0.02, and 157% of controls, P < 0.01) and proteasome C8 subunit mRNA (222% of control, P < 0.05) was seen at day 2. A second more important peak of induction of pUb mRNA was seen at day 3 (251 and 217% of controls for the UbB and UbC transcripts, respectively, P < 0.001). All transcripts returned to near control levels by day 4. In the soleus, induction of E2-14k mRNA started at day 3 and reached 216 and 208% of controls at day 4 (P < 0.001), whereas an increase of pUb mRNA was observed at days 3 (213 and 241%, P < 0.05) and 4 (211 and 221%, P < 0.001). A rise of proteasome C8 subunit mRNA accumulation was also seen in the soleus at days 3 (217%, P < 0.05) and 4 (157%, P < 0.05). Reduced ubiquitin conjugate levels, possibly due to their rapid degradation through increased proteasome activity, were observed in both muscle types at day 3. The parallel between the catabolic effects of CTC and activation of the ubiquitin pathway in muscles of CTC-treated rats strongly suggests the involvement of this system in glucocorticoid-induced muscular atrophy.

Tissue-specific enhancer of the human glycoprotein hormone alpha-subunit gene: dependence on cyclic AMP-inducible elements.

We identified and characterized elements which confer tissue specificity and cyclic AMP (cAMP) responsiveness to the human glycoprotein alpha-subunit gene. An enhancer containing an 18-base-pair repeat conferred cAMP responsiveness in a non-tissue-specific fashion. DNase I protection assays revealed DNA-binding factors that bound to this element in both placental and nonplacental cells. It also enhanced the alpha-subunit promoter in a tissue-specific manner but had a negligible effect on a heterologous promoter. A unique element found upstream of this enhancer had no independent activity but, in combination with the cAMP-responsive enhancer, distinctly increased the tissue-specific activity of both the alpha-subunit promoter and a heterologous promoter. A factor that bound to this upstream element was found in placental but not nonplacental cells. We conclude that this novel element acts, perhaps through a specific trans-acting factor, in concert with a cAMP-responsive enhancer to confer tissue specificity to the alpha-subunit gene.

Maintenance of prolactin (PRL) binding sites in rat liver cells in suspension culture: effect of PRL and of inhibitors of various cellular functions.

An in vitro method to study the regulation of PRL receptors has been established using adult rat liver cells cultured in a continuous suspension in L-15 medium. PRL binding averaged 28.2 +/- 1.8% of the added labeled hormone per 10(6) cells in freshly isolated liver cells prepared from female rats treated with 17 beta-estradiol. When these cells were incubated at 37 C, binding rapidly declined by 50% at 10 h and 90% at 48 h. This rapid decline could be counteracted by the inclusion of ovine PRL (50 nM), which maintained initial PRL receptor levels up to 48 h of culture. Higher concentrations of PRL (2.5 microM) induced a rapid down-regulation, apparent at 2 and 10 h of culture. Cycloheximide (50 micrograms/ml) induced a slight diminution of control PRL receptor levels and partially reversed the effect of 50 nM PRL. Approximately 60% of the PRL receptors were resistant to the effect of cycloheximide. On the other hand, actinomycin D (10 micrograms/ml) had no effect on PRL receptor levels in control and only a very slight effect in PRL-treated cells. Dinitrophenol, which blocks metabolic oxidation, also partially reversed the effect of 50 nM PRL although it was without any significant effect on control levels. Chloroquine (100 microM) and colchicine (1 microM) failed to alter PRL binding either in the absence or presence of 50 nM PRL. Our results suggest that the existence of regulatory factors occurring in vivo, which are absent in the culture medium, could be responsible for the decline in PRL receptor levels in the control hepatocytes. PRL itself could be one of these factors. On the other hand, and in agreement with the putative actions of the drugs utilized, the mechanism of the PRL-induced maintenance of receptor levels appears to lie in part with an effect on receptor synthesis at the translational (ribsomal) level but to be independent of the internalization or of lysosomal degradation.

Interaction of prolactin (PRL) binding sites with PRL receptor antibodies in rat liver cells in suspension culture: effect of inhibitors of cellular functions.

We have recently demonstrated that prolactin is able to maintain the level of in receptors in cultured rat hepatocytes. This effect could be modulated by various inhibitors of cellular functions. We report here that an antibody developed against a partially purified prolactin receptor preparation can mimic this effect of the hormone (although to a lesser extent) and that drugs can modulate it in a similar manner. In particular, cycloheximide (50 micrograms/mL), which reduced basal receptor levels by approximately 40%, totally reversed the maintenance induced by the antireceptor serum. Actinomycin D (10 micrograms/mL), another protein synthesis inhibitor (at the transcriptional level), had no effect of basal receptor concentration, but counteracted by about one-half the antiserum-induced maintenance. This effect of actinomycin D is much clearer here than the effect previously observed on prolactin-induced receptor levels in rat liver cells in culture. The effect of dinitrophenol (1 mM) on basal levels was of limited amplitude but maintenance was again partly reversed by this drug. In accordance with previous results obtained with prolactin, chloroquine (100 microM) and colchicine (1 microM) failed to alter prolactin binding either in the absence or presence of 5% antireceptor serum. The effect of the antiserum indicates that prolactin itself is not required beyond the membrane for its effect on receptor regulation to be attained. These results also confirm our previous results with prolactin maintenance of prolactin receptor levels in rat liver cells in culture, that the mechanism of receptor maintenance appears to be due in part to a stimulation of receptor synthesis but to be independent of the internalization or of lysosomal degradation.

The effect of chloroquine on lysosomal prolactin receptors in rat liver.

PRL receptors have been previously identified in purified rat liver plasma membrane and Golgi vesicle preparations. In this study, we report on PRL receptors located in highly purified lysosome preparations. These lysosomal PRL receptors were characterized using Scatchard analysis and compared to other intracellular and cell surface receptors. We have identified two classes of lysosomes. Lighter lysosome-like vesicles, which are greatly enriched in acid phosphatase activity (the marker enzyme of lysosomes), contain a great deal of binding activity. This PRL binding was only slightly increased by pretreatment of animals with the lysosomotropic agent chloroquine. In contrast, mature lysosomes showed very little binding activity in control animals, but chloroquine treatment increased binding 7- to 8-fold in these mature lysosomes. We suggest that the lysosome-like structures are immature lysosomes (namely prelysosomes) toward which the hormone-receptor complex is internalized: they appear to bear little proteolytic activity. These structures could play a role in PRL receptor recycling. Lysosomal PRL receptors showed curvilinear Scatchard plots, in contrast to plasma membrane and Golgi counterparts, which were linear over the same range of hormone concentrations. The high affinity site in lysosomes had a Kd comparable to the cell surface and Golgi receptors. The number of binding sites per mg protein in prelysosomes and lysosomes was 3 times greater than that in the homogenate, but Golgi preparations were 3 times as rich as lysosomes. The great number of PRL receptors in prelysosomes could be attributed, in large part, to the low affinity sites. The internalization of PRL into rat liver was examined after in vivo injection of [125I]iodoovine PRL. The labeled hormone was found initially in the plasma membrane fraction, after which it localized preferentially in the Golgi fraction, with maximum incorporation 15 min postinjection. Substantial radioactivity was observed in both classes of lysosomes (L-1 and L-2). In contrast to the Golgi fraction, maximum incorporation of [125I]iodoovine PRL in lysosomes occurred at 30 min. This suggests either that during internalization, PRL first reaches Golgi elements and is then transferred to the lysosomal compartment, or that there are two independent pathways of internalization, one rapid toward the Golgi complex (may be a path of receptor recycling) and the other toward lysosomes (probably leading to receptor degradation).

Intracellular transformation of prolactin following internalization into rat liver.

We investigated prolactin (PRL) degradation in rat liver lysosomes both in vivo and in vitro. In previous studies we showed that, in addition to the Golgi apparatus, PRL is internalized towards lysosomes and light, lysosome-like vesicles which we identified as 'prelysosomes'. Injected [125I]oPRL that localized in lysosomes and prelysosomes at times varying from 0 to 45 min showed significant differences from fresh and plasma membrane- (PM) or Golgi-bound hormone. First, it was more easily dissociable by 3 M MgCl2 than Golgi- but less than PM-bound [125I]oPRL. Second, it was only in lysosomal fractions that, as time following injection increased, a significant part of dissociable radioactivity became non-TAC-precipitable. When MgCl2-extracted [125I]oPRL was subjected to gel filtration on a Sephadex G-75 fine column, some of the radioactivity, and especially that extracted from prelysosomal or lysosomal fractions, eluted as a high molecular weight (HMW) entity, most co-migrated with fresh [125I]oPRL, and a little was found in small fragments. Only the central peak had any rebinding activity, which was comparable to that of fresh hormone. In an in vitro study we incubated [125I]hGH with lysosomal fractions for 16 h at 25 degrees C. After centrifugation, an aliquot of supernatant hormone was assayed for its binding capacity to standard receptor preparations and the rest subjected to gel filtration. Peak fractions were also tested in binding assay. [125I]hGH that had been in contact with prelysosomes lost almost all of its ability to bind to standard receptors and totally migrated in the HMW peak, at the void volume of the column.(ABSTRACT TRUNCATED AT 250 WORDS)