Lamin A/C-Related Cardiac Disease: Late Onset With a Variable and Mild Phenotype in a Large Cohort of Patients With the Lamin A/C p.(Arg331Gln) Founder Mutation

BACKGROUND

Interpretation of missense variants can be especially difficult when the variant is also found in control populations. This is what we encountered for the LMNA c.992G>A (p.(Arg331Gln)) variant. Therefore, to evaluate the effect of this variant, we combined an evaluation of clinical data with functional experiments and morphological studies.

METHODS AND RESULTS

Clinical data of 23 probands and 35 family members carrying this variant were retrospectively collected. A time-to-event analysis was performed to compare the course of the disease with carriers of other LMNA mutations. Myocardial biopsies were studied with electron microscopy and by measuring force development of the sarcomeres. Morphology of the nuclear envelope was assessed with immunofluorescence on cultured fibroblasts. The phenotype in probands and family members was characterized by atrioventricular conduction disturbances (61% and 44%, respectively), supraventricular arrhythmias (69% and 52%, respectively), and dilated cardiomyopathy (74% and 14%, respectively). LMNA p.(Arg331Gln) carriers had a significantly better outcome regarding the composite end point (malignant ventricular arrhythmias, end-stage heart failure, or death) compared with carriers of other pathogenic LMNA mutations. A shared haplotype of 1 Mb around LMNA suggested a common founder. The combined logarithm of the odds score was 3.46. Force development in membrane-permeabilized cardiomyocytes was reduced because of decreased myofibril density. Structural nuclear LMNA-associated envelope abnormalities, that is, blebs, were confirmed by electron microscopy and immunofluorescence microscopy.

CONCLUSIONS

Clinical, morphological, functional, haplotype, and segregation data all indicate that LMNA p.(Arg331Gln) is a pathogenic founder mutation with a phenotype reminiscent of other LMNA mutations but with a more benign course.

Electrical signals affect the cardiomyocyte transcriptome independently of contraction

Cardiomyocytes in vivo are continuously subjected to electrical signals that evoke contractions and instigate drastic changes in the cells' morphology and function. Studies on how electrical stimulation affects the cardiac transcriptome have remained limited to a small number of heart-specific genes. Furthermore, these studies have ignored the interplay between the electrical excitation and the subsequent contractions. We carried out a genomewide assessment of the effects of electrical signaling on gene expression, while distinguishing between the effects deriving from the electrical pulses themselves and the effects instigated by the evoked contractions. Changes in gene expression in primary cultures of neonatal ventricular cardiomyocytes from Lewis Rattus norvegicus were investigated with microarrays and RT-quantitative PCR (QPCR). A series of experiments was included in which the culture medium was supplemented with the contraction inhibitor blebbistatin to allow for electrical stimulation in the absence of contraction. Electrical stimulation was shown to directly enhance calcium handling and induce cardiomyocyte differentiation by arresting cell division and activating key cardiac transcription factors as well as additional differentiation mechanisms such as wnt signaling. Several genes involved in metabolism were also directly activated by electrical stimulation. Furthermore, our data suggest that contraction exerts negative feedback on the transcription of various genes. Together, these observations indicate that intercellular electric currents between adjacent cardiomyocytes have an important role in cardiomyocyte development. They act at least partially through a pulse-specific gene expression program that is activated independently from the evoked contractions.

Both emerin and lamin C depend on lamin A for localization at the nuclear envelope

Physical interactions between lamins and emerin were investigated by co-immunoprecipitation of in vitro translated proteins. Emerin interacted with in vitro translated lamins A, B1 and C in co-immunprecipitation reactions. Competition reactions revealed a clear preference for interactions between emerin and lamin C. Structural associations between lamins and emerin were investigated in four human cell lines displaying abnormal expression and/or localisation of lamins A and C. In each cell line absence of lamins A and C from the nuclear envelope (NE) was correlated with mis-localisation of endogenous and exogenous emerin to the ER. In two cell lines that did not express lamin A but did express lamin C, lamin C as well as emerin was mis-localised. When GFP-lamin A was expressed in SW13 cells (which normally express only very low levels of endogenous lamin A and mis-localise endogenous emerin and lamin C), all three proteins became associated with the NE. When GFP-lamin C was expressed in SW13 cells neither the endogenous nor the exogenous lamin C was localised to the NE and emerin remained in the ER. Finally, lamins A and C were selectively eliminated from the NE of HeLa cells using a dominant negative mutant of lamin B1. Elimination of these lamins from the lamina led to the accumulation of emerin as aggregates within the ER. Our data suggest that lamin A is essential for anchorage of emerin to the inner nuclear membrane and of lamin C to the lamina.

Neuroendocrine-specific protein C, a marker of neuronal differentiation, is reduced in brain of patients with Down syndrome and Alzheimer's disease

Neuroendocrine-specific protein C (NSP-C) is found in neural and neuroendocrine cells and associated with the endoplasmic reticulum. Its expression was found to correlate with the degree of neuronal differentiation. As the neuropathological findings in Down syndrome (DS) includes deficits of differentiation, and we detected a downregulated sequence with 100% homology with NSP-C homolog mRNA in temporal cortex of patients with DS as well as Alzheimer's disease (AD) using differential display-polymerase chain reaction (DD-PCR), we decided to examine the protein levels of NSP-C in temporal, frontal cortex and cerebellum of DS and AD. To normalize NSP-C versus neuronal density, we also determined neuron-specific enolase (NSE) levels and calculated the ratios. NSP-C was significantly reduced in DS (temporal and frontal cortex) and AD (frontal cortex) compared to controls. The significant decrease of NSP-C in DS was even more pronounced when related to NSE levels. Impaired differentiation in DS brain may well be due to absolutely and relatively decreased NSP-C levels in temporal and frontal cortex. As NSP-C was also reduced in AD frontal cortex, NSP-C deficits in these disorders may be reflecting neurodegenerative changes rather than a primary and specific finding of DS or AD pathogenesis.

Dynamics of the nuclear lamina as monitored by GFP-tagged A-type lamins

The behavior of chimeric proteins consisting of A-type lamins and green fluorescent protein (GFP) was studied to investigate the localization and dynamics of nuclear lamins in living cells. Cell line CHO-K1 was transfected with cDNA constructs encoding fusion proteins of lamin A-GFP, lamin Adelta10-GFP, or lamin C-GFP. In the interphase nucleus lamin-GFP fluorescence showed a perinuclear localization and incorporation into the lamina for all three constructs. Our findings show for the first time that the newly discovered lamin A 10 protein is localized to the nuclear membrane. The GFP-tagged lamins were processed and behaved similarly to the endogenous lamin molecules, at least in cells that expressed physiological levels of the GFP-lamins. In addition to the typical perinuclear localization, in the majority of transfected cells each individual A-type lamin-GFP revealed an extensive collection of branching intra- and trans-nuclear tubular structures, which showed a clear preference for a vertical orientation. Time-lapse studies of 3-D reconstructed interphase cells showed a remarkable stability in both number and location of these structures over time, while the lamina showed considerable dynamic movements, consisting of folding and indentation of large parts of the lamina. Fluorescence recovery after bleaching studies revealed a low protein turnover of both tubular and lamina-associated lamins. Repetitive bleaching of intranuclear areas revealed the presence of an insoluble intranuclear fraction of A-type lamins. Time-lapse studies of mitotic cells showed that reformation of the lamina and the tubular structures consisting of A-type lamins did not occur until after cytokinesis was completed.

Peroxide-induced membrane blebbing in endothelial cells associated with glutathione oxidation but not apoptosis

Cells under oxidative stress induced by peroxides undergo functional and morphological changes, which often resemble those observed during apoptosis. Peroxides, however, also cause the oxidation of intracellular reduced glutathione (GSH). We investigated the relation between these peroxide-induced effects by using human umbilical vein endothelial cells (HUVEC) and two HUVEC-derived cell lines, ECRF24 and ECV304. With HUVEC, tert-butyl hydroperoxide (tBH) or hydrogen peroxide application in the presence of serum induced, in a dose-dependent way, reorganization of the actin cytoskeleton, membrane blebbing, and nuclear condensation. These processes were accompanied by transient oxidation of GSH. With ECRF24 cells, this treatment resulted in less blebbing and a shorter period of GSH oxidation. However, repeated tBH addition increased the number of blebbing cells and prolonged the period of GSH oxidation. ECV304 cells were even more resistant to peroxide-induced bleb formation and GSH oxidation. Inhibition of glutathione reductase activity potentiated the peroxide-induced blebbing response in HUVEC and ECRF24 cells, but not in ECV304 cells. Neither membrane blebbing nor nuclear condensation in any of these cell types was due to apoptosis, as evidenced by the absence of surface expression of phosphatidylserine or fragmentation of DNA, even after prolonged incubations with tBH, although high tBH concentrations lead to nonapoptotic death. We conclude that, in endothelial cells, peroxide-induced cytoskeletal reorganization and bleb formation correlate with the degree of GSH oxidation but do not represent an early stage of the apoptotic process.

Neuronal differentiation is accompanied by NSP-C expression

Neuroendocrine-specific protein (NSP) reticulons are expressed in neural and neuroendocrine tissues and cell cultures derived therefrom, while most other cell types lack NSP-reticulons. Three major subtypes have been identified so far, designated NSP-A, NSP-B, and NSP-C. We have investigated the correlation between the degree of neuronal differentiation, determined by morphological and biochemical criteria, and NSP-reticulon subtype expression. For this purpose, several human neuroblastoma cell lines, exhibiting different degrees of neuronal differentiation, were examined immuno(cyto)chemically. It became obvious that the expression of NSP-C, as detected by immunofluorescence microscopy and Western blotting, is most prominent in cell lines with a high degree of neuronal differentiation, such as LA-N-5. Such highly differentiated cells also express other neural and neuroendocrine markers, such as neural cell adhesion molecule (NCAM), neurofilament proteins, synaptophysin, and chromogranin. NSP-A was observed in all cell lines to a different extent. However, no clear correlation was observed with the degree of neuronal differentiation as defined by other neuronal and neuroendocrine markers or morphology. NSP-B could not be detected. The induction of neuronal differentiation with nerve growth factor, dbcAMP, and retinoic acid in the rat pheochromocytoma cell line PC12 and the human teratocarcinoma cell line hNT2, respectively, induced the expression of NSP-A and NSP-C in these cell lines parallel to the induction of neurofilament protein expression. It is concluded that NSP-C expression, in particular, is strongly correlated with neuronal differentiation.

Comparison of A and B-type lamin expression in reactive lymph nodes and nodular sclerosing Hodgkin's disease

AIMS

In order to clarify the differentiation and proliferation status of the Reed-Sternberg and Hodgkin cells we studied A and B-type lamin expression with specific monoclonal antibodies in nodular sclerosing Hodgkin's disease. Its normal counterpart, the reactive lymph node, was also examined for lamin subtype expression.

METHODS AND RESULTS

The CD20 positive centrocytes and centroblasts of the follicle centre in the reactive lymph nodes expressed lamin B1, but were not or only very weakly positive for lamin B2 or A-type lamin antibodies. Mantle zone lymphocytes displayed lamins B1 and B2, but were negative for A-type lamins. Furthermore, CD3- and CD20-positive lymphocytes in the medulla and paracortex lacked A-type lamins, but were positive for both B-type lamins. Finally, the proliferation marker Ki67 was mainly detected in the centroblasts, but also in a fraction of the A-type lamin negative cells in the paracortex and medulla. In Hodgkin's disease, all cells expressed lamins B1 and B2, whereas A-type lamins were primarily observed in CD30-positive Reed-Sternberg and Hodgkin cells. About 20% of the Reed-Sternberg and Hodgkin cells expressed Ki67, with co-expression of lamin A in most of these cells.

CONCLUSIONS

Ki67 and A-type lamin staining were in general mutually exclusive in lymph nodes, indicating that A-type lamin positive cells are not proliferative. This suggests also that the A-type lamin expression in Reed-Sternberg and Hodgkin cells is correlated with a relatively mature phenotype of these malignant cells. However, some of these differentiated malignant cells still have a capacity to proliferate as indicated by Ki67 positivity. Our observation that lamin B2 expression in the follicle centre cells of the reactive lymph node is low or absent indicates that this lamin subtype is not always expressed in nucleated cells, which is in clear contrast to the results obtained in previous studies in other diseases and in normal tissues. Absence of lamin B2 expression may be associated with the follicle centre stage of B-cells.

Detailed analysis of cell cycle kinetics upon proteasome inhibition

We have studied specific effects of proteasome inhibition on cell cycle progression. To this end, the protease inhibitors MG115, calpain inhibitor I, and calpain inhibitor II, which display differential inhibitory effects on proteasomes, were used. Cell kinetic studies using bromodeoxyuridine pulse labeling revealed a complete block of G1/S and metaphase transitions and a delayed progression through S phase in cell cultures treated with 54 microM of MG115. Calpain inhibitor I in similar concentrations displayed a fivefold lower effect on cell cycle kinetics. Calpain inhibitor II and MG2M, which is a structural analogue of MG115, had no effect on the cell cycle. The inhibitory effect of MG115 treatment was reversible, because the cell cycle was immediately resumed when the MG115-containing culture medium was replaced by fresh culture medium. Because ubiquitinated proteins accumulated after MG115 treatment, it was confirmed that ubiquitin-dependent protein degradation, and thus proteasomal activity were blocked. By comparison of biochemical and in vitro proteasome inhibition experiments, it was hypothesized that chymotrypsin-like activity of proteasomes may play an important role in cell cycle kinetics.

A- and B-type lamins are differentially expressed in normal human tissues

A selection of normal human tissues was investigated for the presence of lamins B1, B2, and A-type lamins, using a panel of antibodies specific for the individual lamin subtypes. By use of immunoprecipitation and two-dimensional immunoblotting techniques we demonstrated that these antibodies do not cross-react with other lamin subtypes and that a range of different phosphorylation isoforms is recognized by each antibody. The lamin B2 antibodies appeared to decorate the nuclear lamina in all tissues examined, except hepatocytes, in which very little lamin B2 expression was observed. In contrast to previous studies, which suggested the ubiquitous expression of lamin B1 in mammalian tissues, we show that lamin B1 is not as universally distributed throughout normal human tissues as was to be expected from previous studies. Muscle and connective tissues are negative, while in epithelial cells lamin B1 seemed to be preferentially detected in proliferating cells. These results correspond well with those obtained for lamin B1 in chicken tissues. The expression of A-type lamins is most prominent in well-differentiated epithelial cells. Relatively undifferentiated and proliferating cells in epithelia showed a clearly reduced expression of A-type lamins. Furthermore, most cells of neuroendocrine origin as well as most hematopoietic cells were negative for A-type lamin antibodies.

A comparison of NSP-reticulons with conventional neuroendocrine markers in immunophenotyping of lung cancers

Neuroendocrine-specific protein (NSP)-reticulons are endoplasmic reticulum-associated protein complexes, which have been identified as markers for neuroendocrine differentiation. In this study, the expression of two members of the family of NSP-reticulons, NSP-A and NSP-C, have been investigated in different types of lung cancer and compared with the expression patterns of five conventional neuroendocrine markers, the neural cell adhesion molecule (NCAM), synaptophysin, chromogranin A, Leu-7, and neurofilament proteins. NSP-A and NSP-C antibodies were reactive with most carcinoid tumour and small cell lung carcinoma (SCLC) cases, while atypical carcinoid tumours showed a variable expression. In the total group of neuroendocrine tumours, a high concordance of expression was found between NSP-A and NSP-C, while their expression correlated well with NCAM and synaptophysin positivity. Chromogranin A, Leu-7, and neurofilament proteins were shown to be expressed to a limited extent in these neuroendocrine tumours. In a selected group of non-SCLCs known to exhibit neuroendocrine features, NSP-A expression was detected at much higher frequency than NSP-C. In virtually all NSP-A positive cases, this expression was associated with one or more of the other neuroendocrine markers. NSP-A expression showed a stronger correlation with conventional neuroendocrine markers than NCAM. In detecting neuroendocrine differentiation in non-SCLC, NSP-A is more sensitive than synaptophysin, chromogranin A, Leu-7, and neurofilament proteins. It is concluded that NSP-reticulons are valuable markers in the diagnosis of neuroendocrine differentiation in non-SCLC and should be used in conjunction with NCAM.

Subcellular localization of proteasomes in apoptotic lung tumor cells and persistence as compared to intermediate filaments

We have studied the subcellular localization and expression levels of proteasomes during apoptosis in a lung cancer cell line. Apoptosis was induced by exposing the cells to 200 microM olomoucine, a specific cyclin-dependent kinase inhibitor. The morphological changes characteristic for apoptotic cells were visible: the cells reduced in size, the chromatin condensed and the membranes became convoluted. As the process continued, the nuclei became fragmented, and the cells broke up into cytoplasmic vesicles and apoptotic bodies. Immunocytochemically, apoptotic cells were detected by the ability to bind annexin V at their surface. During the initial stages of apoptosis, proteasomes were present in the nucleus as well as in the cytoplasm. Upon increased chromatin condensation, nuclear proteasomes were found predominantly surrounding the chromatin, while the chromatin itself remained devoid of staining. That the proteasomes persisted relatively long in the apoptotic cells was shown by immunoblotting of non-denaturing gels, which indicated that both 20S and 26S proteasomes were present in apoptotic cells. In immunofluoresence microscopy the proteasome fluorescence intensity of apoptotic cells seemed higher than that of non-apoptotic cells. These differences in intensity were even more pronounced after Triton X-100 extraction. Flow cytometry revealed that the absolute levels of proteasome staining in cells were decreased after Triton X-100 extraction. However, no differences in staining levels were detected between apoptotic and non-apoptotic cells. A relative increase of proteasome concentration through cell shrinkage or a concentration in certain cell compartments may be the origin of the apparently increased signal that was seen in immunofluorescence microscopy. Furthermore, proteasomes were clearly detectable in the apoptotic bodies and cytoplasmic vesicles at the time immunocytochemical reactivity for cytokeratins and lamins had diminished to a large extent. Immunoblotting of denaturing polyacrylamide gels confirmed the results obtained by flow cytometry. The proteasome content was retained only partially in the cells after Triton X-100 extraction, while the intermediate filaments were not detectable anymore in the apoptotic cells.

Nuclear lamin expression in chronic hibernating myocardium in man

Cardiomyocytes of chronic hibernating myocardium are known to undergo structural changes, indicative of dedifferentiation. Amongst these are changes in nuclear shape and chromatin distribution. Nuclear A-type lamins are known to be expressed in a differentiation-related fashion and to contribute to nuclear integrity and chromatin organization. Lamin expression was investigated with immunocytochemical staining procedures in biopsies from patients with chronic hibernating myocardium. The expression of A-type (lamin A and C) were shown to be downregulated during hibernation, while lamin B2 remained present in hibernating cardiomyocytes in a way similar to embryonic muscle cells. All heart muscle cells were shown to be negative for lamin B1. The absence of A-type lamins in chronic hibernating cardiomyocytes could be taken as an additional argument for the dedifferentiation state of these cells. The absence of A-type lamins was accompanied by dispersion of the nuclear heterochromatin, in a way similar to nuclei of embryonic cardiomyocytes.

An alternative splicing product of the lamin A/C gene lacks exon 10

Expression of the A-type lamins was studied in the lung adenocarcinoma cell line GLC-A1. A-type lamins, consisting of lamin A and C, are two products arising from the same gene by alternative splicing. Northern blotting showed in GLC-A1 a relatively low expression level of lamin C and an even lower expression level of lamin A as compared to other adenocarcinoma cell lines. Immunofluorescence studies revealed highly irregular nuclear inclusions of lamin A, suggesting protein or gene expression abnormalities. Reverse transcriptase-polymerase chain reaction-based cDNA analysis followed by sequencing indicated the presence of an as yet unidentified alternative splicing product of the lamin A/C gene. This product differs from lamin A by the absence of the 5' part of exon 10 (90 nucleotides). Therefore we propose to designate this product lamin Adelta10. Deletion of the 30 amino acids encoded by exon 10 was predicted to result in a shift in pI of the protein from 7.4 to approximately 8.6, which was confirmed by two-dimensional immunoblotting. mRNA analysis in a variety of cell lines, normal colon tissue as well as carcinomas demonstrated the presence of lamin Adelta 10 in all samples examined, suggesting its presence in a variety of cell types.

Neuroendocrine-specific protein C (NSP-C): subcellular localization and differential expression in relation to NSP-A

A mouse monoclonal antibody RNL-4, as well as rabbit polyclonal antiserum POL-8 were raised against a synthetic peptide, encompassing the first twenty unique amino-terminal amino acid residues of NSP-C. The specificity of both immunoreagents was established in an ELISA assay using the synthetic peptide and by their immunoreactivity to NSP-C fusion proteins. Immunofluorescence analysis of COS-1 cells, transfected with NSP-C cDNA, showed staining of the endoplasmic reticulum with RNL-4 and POL-8. No cross-reactivity of these reagents with NSP-A or NSP-B was seen. Immunohistochemical studies in normal human tissues showed expression of NSP-C in tissues of neural and neuroendocrine origin, i.e. neurons of the central and peripheral nervous system, the neurohypophysis, adrenal medulla, adenohypophysis, pars intermedia, and in sporadic neuroedocrine cells of the lung. Expression of NSP-C was found in several small cell lung cancer (SCLC) cell lines, in non-SCLC cell lines with neuroendocrine features, but not in typical non-SCLC cell lines. Also, in a neuroblastoma cell line NSP-C expression was observed. Immunoblotting and immunoprecipitation studies with RNL-4 and POL-8 identified the 23 kDa NSP-C polypeptide in these cell lines. Immunofluorescence microscopy showed that also in these cell lines NSP-C is located at the endoplasmic reticulum, as shown before for NSP-A and NSP-B. In some of the cell lines coexpression of NSP-A and NSP-C was observed, while in others only one of the two could be detected. The differential expression of NSP-A and NSP-C in these cell lines is confirmed by immunoblotting and was also evident at the mRNA level. When NSP-A and NSP-C were coexpressed, the number of NSP-C-positive cells was always less than the number of NSP-A-positive cells. A partial colocalization of NSPs was observed in the endoplasmic reticulum. Cell fractionation studies revealed that both proteins are retained in the membranous fraction of the cell, from which they can be solubilized by Triton X-100. Immunoprecipitation analyses under native conditions indicate that NSP-C does not need to associate with NSP-A to form high molecular weight NSP-reticulons.

Abnormal A-type lamin organization in a human lung carcinoma cell line

We have studied the expression of lamins A and C (A-type lamins) in a lung carcinoma cell line using type-specific monoclonal antibodies. Using immunofluorescence and immunoblotting studies it was noted that several irregularities in lamin expression exist in the cell line GLC-A1, derived from an adenocarcinoma. First, the expression of the A-type lamins was lower than in other adenocarcinoma cell lines of the lung. Also the ratio between lamins A and C proteins was 1:8 instead of the 1:1 ratio seen in the other cell lines. Northern blotting confirmed the altered level of A-type lamin expression. Secondly, an abnormal localization of lamin A was observed. Intensely fluorescing lamin A aggregates were observed in the nucleus, rather than the typical perinuclear staining pattern. Confocal scanning laser microscopy revealed that the lamin A aggregates were indeed present throughout the internal nucleus. When these cells were extracted with Triton X-100 the nucleoplasmic aggregates disappeared, which indicates that the A-type lamins are not properly incorporated into the lamina. The A-type lamins in other cell lines derived from adenocarcinomas remained present in the nuclear periphery after extraction with the non-ionic detergent. Immunoblotting studies of the Triton X-100 soluble and insoluble fractions showed that lamin A and an apparently truncated product, which was detected with the lamin A antibody, were present in the insoluble fraction of GLC-A1. This truncated product is partly Triton X-100 soluble since it was also detected in the detergent soluble fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in immunocytochemical detectability of proteasome epitopes depending on cell growth and fixation conditions of lung cancer cell lines

The localization of proteasome epitopes in the lung cancer cell lines NCI-H82, derived from a small cell lung cancer, and MR65, derived from a squamous cell lung carcinoma, was studied in relation to cell growth conditions. For this purpose the proteasome monoclonal antibodies MCP34 and MCP20 were applied to the cells growing under different nutritional conditions, resulting in different proliferative states. Using indirect immunofluorescence microscopy with brief fixation in methanol (5 sec, -20 degrees C) followed by three dips in acetone (5 sec at room temperature), it became obvious that the intracellular detectability of the proteasomes changes depending on the nutritional and proliferative status of the tumor cells. Two types of experiments were carried out: (1) cells were grown for two days at different cell densities, with an excess of culture medium, and (2) cells were seeded in a low cell density and monitored for 6 days without change of medium. In cells grown at low density, the proteasomes can be detected mainly in the nuclei, while the nucleoli are almost devoid of staining, and the cytoplasm is only slightly stained. In cells grown at high density, the staining pattern changes with a much less pronounced nuclear staining than in the cells at low density, while the cytoplasm remains slightly stained. In the nutrient depletion experiment similar changes were seen. In cells growing under favorable conditions (1 or 2 days in fresh medium) proteasomes are detected mainly in the nuclei, whereas when the medium becomes depleted of nutrients (4 or 5-day-old medium) the staining pattern changes to one with a much less pronounced nuclear staining. However, in immunofluorescence studies on cells grown under similar conditions but fixed in ethanol (-20 degrees C) for 15 min, the changes in proteasome localization pattern were not detected during medium depletion. Using this fixation protocol the proteasomes are detected mainly in the nuclei at all stages of the medium exhaustion experiment. These apparently contrasting results suggest that upon nutrient depletion the proteasome epitopes become less accessible to the antibodies used. Apparently, the epitopes can regain accessibility if an extended ethanol fixation is used. This hypothesis was confirmed by flow cytometry and immunoblotting experiments. In flow cytometry of ethanol-fixed cells the fluorescence intensity of only a minor part of the cell population decreases to some extent with medium depletion, but in the majority of the cells fluorescence remains at its initial level. The immunoblotting experiments show no quantitative changes in proteasome content of the tumor cells at the different growth conditions.

Subcellular localization and supramolecular organization of neuroendocrine-specific protein B (NSP-B) in small cell lung cancer

We have recently isolated and characterized a novel gene that is expressed in a neuroendocrine-specific fashion and was therefore designated neuroendocrine-specific protein (NSP)-gene. The NSP-gene encodes three transcripts of different size, with unique 5'-sequences and completely overlapping 3'-sequences. The resulting proteins have an apparent molecular mass of 135 kDa as determined for NSP-A and 23 kDa as found for NSP-C. In the present study we focused on the biochemical characterization and subcellular localization of NSP-B, so far only found to be expressed in the neuroendocrine lung cancer cell line NCI-H82, and its relation to NSP-A. Transfection studies with the NSP-B transcript in COS-1 cells, followed by immunoprecipitation, resulted in a set of proteins ranging in molecular mass from 35 to 45 kDa, identical to NSP-Bs detected by immunoblotting in NCI-H82. In this cell line a major NSP-B triplet in the 43 to 45 kDa range and a 35 kDa NSP-B were consistently detected. Only the 45 kDa NSP-B was found to be phosphorylated. The observed pI values of the 43 to 45 kDa triplet ranged from 4.8 to 5.0, while the 35 kDa NSP-B has a more basic pI value of 5.7. Gel filtration studies show that NSP-A and NSP-B form supramolecular aggregates with a molecular mass of over 500 kDa, present to a minor extent in the phosphate buffered saline soluble cell fraction, but mainly occurring in the membranous pellet fraction from which they can be solubilized by Triton X-100.(ABSTRACT TRUNCATED AT 250 WORDS)

NSP-encoded reticulons are neuroendocrine markers of a novel category in human lung cancer diagnosis

The NSP gene was recently shown to constitute the prototype of a novel gene family, to be selectively transcribed in neural and endocrine cells, and to encode three overlapping proteins, NSP-A, NSP-B, and NSP-C. These proteins were collectively designated reticulons, because they were found to be anchored to membranes of the endoplasmic reticulum through their common carboxy-terminal regions. The goal of the present study was to determine whether the reticulons might be used as markers for neuroendocrine differentiation in human lung tumors. Therefore, the tissue distribution of the NSP-A protein was studied and expression in human lung tumors was evaluated. Immunohistochemical analysis of normal tissues with monoclonal antibodies specifically recognizing the NSP-A protein indicated that NSP-A exhibits a distinct neuroendocrine distribution pattern since it was found to be expressed in a variety of cells with an established neuroendocrine phenotype but not in cells lacking such features. Results with specimens of a wide variety of primary human tumors provided further support for this claim. Immunohistochemical analysis of primary lung carcinomas revealed that NSP-A was readily detectable in small cell lung carcinoma (SCLCs) (8 of 12) and carcinoid tumors of the lung (3 of 3) but not in nonneuroendocrine non-SCLCs (0 of 10). In 13 of 27 non-SCLCs expressing the neural cell adhesion molecule and/or neurofilament proteins, however, NSP-A was found to be expressed. Northern blot analysis of human lung carcinoma cell lines revealed expression of NSP-A- and/or NSP-C-encoding mRNAs in all 18 SCLC cell lines that were studied, except one; however, no expression of these mRNAs could be detected in any of the 11 non-SCLC cell lines tested. The NSP transcript encoding NSP-B was found only in SCLC cell line NCI-H82. In conclusion, the results of our studies suggest that, in lung tumor cells, expression of NSP-A and most likely also NSP-C is restricted to cells with a neuroendocrine phenotype.

Cluster-10 lung-cancer antibodies recognize NSPs, novel neuro-endocrine proteins associated with membranes of the endoplasmic reticulum

We have identified a novel gene (the NSP gene) encoding 3 transcripts and coding for 3 neuroendocrine-specific proteins (NSPs), by screening a cDNA expression library of the small-cell lung-cancer (SCLC) cell line NCI-H82 with the cluster-10 lung-cancer antibodies RNL2 and RNL3. The 3 transcripts code for NSPs with apparent molecular weights of 135 kDa (NSP-A), 43 to 45 and 35 kDa (NSP-B) and 23 kDa (NSP-C). NSP-A and NSP-B are recognized by antibodies RNL2 and RNL3, while second-generation antibodies, specifically recognizing NSP-A and NSP-C, have been produced after immunization with a hybrid protein obtained after bacterial expression of the largest NSP-transcript or with a synthetic peptide specific for NSP-C. The NSPs exhibit a highly restricted distribution pattern and are found mainly in neural and neuro-endocrine cell types, and in neuro-endocrine tumours. Of the different types of lung tumours, mainly SCLC and carcinoids were positive in immunocytochemical assays using the anti-NSP antibodies, while non-SCLC were in general negative. The subcellular distribution of the NSPs was studied in human SCLC cell lines. They do not co-localize with components typical of neuro-endocrine granules, such as synaptophysin and chromogranin. The use of NSP antibodies in the immunofluorescence technique applied to cultured SCLC cells, made it obvious that these proteins localize in the endoplasmic reticulum. Cell fractionation procedures, monitored by immunoblotting assays, indicated an association of the NSPs with the microsomal fraction, from which they could be solubilized with Triton X-100. Gel filtration studies with this solubilized fraction revealed that NSPs form supramolecular aggregates with a molecular weight of more then 500 kDa.

Differentiation markers for lung-cancer sub-types. A comparative study of their expression in vivo and in vitro

Cell lines representing the major sub-types of lung cancer have proved to be useful tools to study the molecular and cellular biology of these malignancies, provided that they are well established and well characterized. Antibodies directed against constituents of different cellular compartments can detect the type and degree of differentiation in lung cancer and derived cell lines. Antibodies can detect cell-surface adhesion molecules, such as NCAM, cadherins and integrins. NCAM antibodies are able to differentiate between small-cell lung cancer (SCLC) and non-SCLC, both in cell lines and in tumours. In addition, a spectrum of other membrane proteins, expressed in solid tumours, such as epidermal-growth-factor receptor and carcino-embryonic antigen, are retained in cell lines. Cytoplasmic intermediate filament proteins appear to be generally retained in lung-cancer cell lines, their combinations being the same as in solid SCLC, adenocarcinomas and squamous-cell carcinomas. Nuclear expression of lamins is comparable in tumours and in their corresponding cell lines and can be used to differentiate between SCLC and non-SCLC: A-type lamins, which are present in non-SCLC, are absent in most SCLC.

Expression of c-myc in progenitor cells of the bronchopulmonary epithelium and in a large number of non-small cell lung cancers

We performed in situ hybridization for c-myc, N-myc, and L-myc mRNA expression using 35S-labeled cRNA probes on frozen sections of 19 pairs of non-small cell lung cancers (NSCLC) and the surrounding non-neoplastic lung tissue. In non-neoplastic lung, c-myc expression was strongest in bronchial epithelium basal cells and hyperplastic alveolar type II pneumocytes, which are potential progenitor cells for bronchopulmonary epithelium and their tumors. In contrast, N-myc and L-myc mRNAs were not detected in non-neoplastic lung. In studies of freshly resected primary tumors, expression of c-myc was detected in 11 of 19 NSCLC (with the highest levels in squamous cell carcinomas), two of which also expressed L-myc, while N-myc expression was never detected. Levels of c-myc expression in tumors were significantly higher than in non-neoplastic lung samples. We conclude that: (1) c-myc expression in non-neoplastic lung tissues is highest in bronchial basal cells and hyperplastic type II cells, and (2) in NSCLC, overexpression of the myc-proto-oncogene is common.

Nuclear A-type lamins are differentially expressed in human lung cancer subtypes

Nuclear A-type and B-type lamin expression was investigated in the major human lung cancer subtypes: small cell lung cancer (SCLC), squamous cell carcinomas, and adenocarcinomas (both non-SCLC). Twenty-two human lung cancer cell lines and 46 fresh frozen human lung cancer specimens were examined. Expression of B-type lamins was found in all the different cell lines. A-type lamins were expressed in all non-SCLC cell lines but were absent or only weakly expressed in 14 out of 16 SCLC cell lines. The immunocytochemical results were confirmed by immunoblotting and Northern blot analyses. In sections of SCLCs and non-SCLCs, B-type lamins were found to be expressed in all tumors. However, in some non-SCLCs, particularly in adenocarcinomas, a considerable proportion of the tumor cells were negative for B-type lamins. A-type lamin expression in SCLCs was weakly positive or negative in 14 out of 15 cases. In contrast, all non-SCLCs displayed A-type lamins, but in several of these samples, both cytoplasmic and nuclear staining was observed.

Cloning and expression of alternative transcripts of a novel neuroendocrine-specific gene and identification of its 135-kDa translational product

Monoclonal antibodies RNL-2 and RNL-3 were previously shown to react with four 35-45-kDa proteins, expressed only in small cell lung carcinoma NCI-H82 cells, but to stain a subset of neuroendocrine tissues and neoplasms (Broers, J. L. V., Mijnheere, E. P., Klein Rot, M., Schaart, G., Sijlmans, A., Boerman, O. C., and Ramaekers, F. C. S. (1991) Cancer 67, 619-633). We used RNL-2 and RNL-3 to isolate cDNA sequences that code for proteins containing the two corresponding epitopes and utilized such cDNAs to develop second generation antibodies. Using these antibodies, we identified a novel 135-kDa protein. The corresponding cDNAs were found to belong to a previously unknown gene with a neuroendocrine-specific expression pattern, tentatively designated NSP gene. NSP transcription appeared to result in mRNAs of 3.4 and 1.8 kilobases (kb). In the NCI-H82 cells only, an apparently aberrant transcript of 2.3 kb was found. cDNAs containing coding sequences of the 3.4-, 2.3-, and 1.8-kb transcripts were isolated, and nucleotide sequence analysis revealed extensive sequence overlap and open reading frames for proteins of 776, 356, and 208 amino acids, respectively. The three deduced proteins all have a common carboxyl-terminal part with two large hydrophobic regions. Transfection of the complete coding sequences of the 3.4-kb transcript resulted in the production of a protein with an apparent molecular mass of 135 kDa. This protein is predicted to be highly negatively charged (calculated pI of 4.35), to be rich in proline and serine, and to contain multiple potential phosphorylation sites.

Cytokeratins expressed in experimental rat bronchial carcinomas

Cytokeratin expression in rat lung tumors was studied using polypeptide-specific monoclonal antibodies (MAbs) to human cytokeratins 4, 5, 7, 8, 10, 13, 14, 18 and 19. Experiments were performed on tumor fragments derived from 5 experimental rat squamous-cell lung tumors and one adenocarcinoma, as well as on cell lines obtained from the same tumors. The aims of this study were to investigate the differentiation profile of the rat tumor tissue and established tumor cell lines based on light and electron microscopical features and on cytokeratin phenotype, to characterize the tumor type and degree of differentiation of the lung tumors maintained during passaging in experimental animals, and to compare the cytokeratin expression pattern in transplanted tumors with that of the cultures derived from these tumors. Our results indicate that, in general, the antibodies used cross-react with rat cytokeratins and that these MAbs can be used to phenotype rat lung carcinomas. Both the tumor fragments and the cultured cells revealed a similar pattern of cytokeratin expression. In addition, the degree of differentiation was maintained upon prolonged culturing in vitro. MAbs to cytokeratin sub-types can therefore be used to distinguish the main sub-types of rat lung tumors and can give an indication about the degree of differentiation.

Expression of surfactant associated protein-A and Clara cell 10 kilodalton mRNA in neoplastic and non-neoplastic human lung tissue as detected by in situ hybridization

Two markers for the progenitor cells of peripheral airways and their tumors are the 10 kilodalton (kd) Clara cell protein and the major surfactant associated protein-A (SP-A). We used the RNA-RNA in situ hybridization technique to study expression of the genes encoding these proteins at the cellular level in 19 pairs of non-neoplastic and neoplastic tissues from resected human lungs. Our results show that in non-neoplastic lung tissue, the Clara 10 kd protein gene was expressed in nonciliated cells of both bronchial and bronchiolar epithelium, indicating that, in contrast to previous assumptions, cells with Clara cell-like differentiation in humans may not be restricted to bronchiolar cells. The incidence of Clara 10 kd protein gene expression, as detected in lung carcinomas (1 out of 19 cases positive) was less than expected based on previous ultrastructural reports. The SP-A gene was strongly expressed in normal alveolar type II cells in non-neoplastic lung and, at higher levels, in hyperplastic cells. In addition, SP-A mRNA expression was observed in scattered bronchial and bronchiolar epithelial cells in 40% of the airways examined. Five out of 17 lung tumors, all of which were adenocarcinomas, were positive for SP-A expression, albeit generally less intense than type II cells. This expression was seen in carcinomas with papillolepidic as well as solid and glandular growth patterns. Our findings provide new insights into the peripheral airway cell differentiation.

Biodistribution of a monoclonal antibody (RNL-1) against the neural cell adhesion molecule (NCAM) in athymic mice bearing human small-cell lung-cancer xenografts

The purpose of this investigation was to determine the targeting potential of the murine monoclonal antibody (MAb) RNL-1 for human small-cell lung cancer (SCLC) in a nude mouse model. RNL-1 is preferentially reactive with SCLC and lung carcinoids, and was classified as a cluster-1 MAb as defined by the International Workshop on Small-Cell Lung-Cancer Antigens. From the intercellular location of the target antigen and its reactivity with 3T3 cells transfected with nucleic acid sequences encoding for the neural cell adhesion molecule (NCAM), it was concluded that RNL-1 is directed against NCAM. RNL-1 was radiolabelled with either 125iodine or 111indium and injected into nude mice bearing NC1-H82 SCLC xenografts. The biodistribution of the radiolabels was determined up to 120 hr post injection. Maximum tumour accretion for 111In-RNL-1 was 11.8%ID/g and 6.5%ID/g for 125I-RNL-1. The accumulation of 111In-RNL-1 could be visualized clearly by gamma scintigraphy without background subtraction techniques. Autoradiographs of whole-body sections from animals injected with 125I-RNL-1 showed that activity in the SCLC xenografts was mainly peripheral, suggesting that tumour uptake is dependent on the vascularization of the tumour tissue.

Novel antigens characteristic of neuroendocrine malignancies

The authors describe the immunochemical detection, biochemical characterization, and tissue distribution of neuroendocrine antigens recognized by three newly developed monoclonal antibodies (MoAb) obtained after immunization of mice with the variant small cell lung cancer (SCLC) cell line NCI-H82. RNL-1 was reactive with neuroendocrine tissues similar to the SCLC cluster-1 MoAb, known to recognize N-CAM. Antibodies RNL-2 and RNL-3 are directed against different epitopes on the same proteinaceous complex. Both MoAb recognize an intracellularly located, water-soluble antigen which has a subunit composition with a protein triplet ranging in molecular weight between 44 and 45 kilodaltons (kD) next to a component of approximately 30 kD. The antibodies RNL-2 and RNL-3 reacted with a subset of neuroendocrine tissues and neuroendocrine neoplasms. In lung cancer both antibodies reacted only with some SCLC and carcinoids and not with nonneuroendocrine lung carcinomas. The potential diagnostic applicability of antibodies RNL-1, RNL-2, and RNL-3 is discussed.

Immunotargeting of human small cell lung cancer xenografts in athymic mice using a monoclonal antibody (RNL-1) against a neuroendocrine-related antigen

A mouse monoclonal antibody (RNL-1) was raised against the variant small cell lung cancer (SCLC) cell line NCI-H82. Immunohistochemical studies on frozen sections showed that the antibody was reactive with most SCLC (15 out of 16) and lung carcinoids (six out of seven), while in general adenocarcinomas and squamous cell carcinomas of the lung were negative. Immunocytochemical studies on 29 different cell lines derived from human lung tumours confirmed the neuroendocrine-related expression of the RNL-1 defined antigenic determinant. Immunoelectron microscopy showed that RNL-1 recognises an extracellular membrane domain, concentrated at adhesion sites between adjacent cells. The tissue distribution of the RNL-1 defined antigen was mainly restricted to neural and neuroendocrine tissues. These immunohistochemical data suggest that RNL-1 is directed against a neuroendocrine-related cell adhesion molecule. Being reactive with an epitope expressed on the surface of most neuroendocrine malignant cells, RNL-1 (IgG1 isotype) is a potential vehicle for targeting SCLC in vivo. We evaluated the ability of radiolabelled RNL-1 to localise human SCLC xenografts in nude mice as a first step in determining the in vivo value for radioimmunodetection. RNL-1 was radioiodinated using the Bolton-Hunter labelling technique. Nude mice bearing NCI-H82 xenografts were injected intravenously with the radiolabelled RNL-1 preparations, and animals were dissected 4, 24, 48, 72 and 120 h post injection (p.i.) to determine the biodistribution of the radiolabel. The iodine-125 label accumulated in the tumour up to 48 h p.i. (6.5% injected dose per gram of tissue [ID g-1]), while the label content of the normal tissues decreased with time.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of intermediate filament proteins in fetal and adult human lung tissues

The expression patterns of intermediate filament proteins in fetal and normal or nonpathological adult human lung tissues are described using (chain-specific) monoclonal antibodies. In early stages of development (9-10 weeks and 25 weeks of gestation) only so-called simple cytokeratins such as cytokeratins 7 (minor amounts). 8, 18 and 19 are detected in bronchial epithelial cells. At later stages of development, the cytokeratin expression patterns become more complex. The number of bronchial cells positive for cytokeratin 7 increases, but basal cells in the bronchial epithelium remain negative. These latter cells show, however, expression of cytokeratin 14 in the third trimester of gestation. Developing alveolar epithelial cells express cytokeratins 7, 8, 18 and 19. In adult human bronchial epithelium cytokeratins 4 (varying amounts), 7, 8, 13 (minor amounts), 14, 18 and 19 can be detected, with the main expression of cytokeratins 7, 8, and 18 in columnar cells and the main expression of cytokeratin 14 in basal cells. Vimentin is detected in all mesenchymal tissues. In addition, fetal lung expresses vimentin in bronchial epithelium, however, to a lesser extent with increasing age, resulting in the expression of vimentin in only few scattered bronchial cells at birth. Also in adult bronchial epithelium the expression of vimentin is noticed in part of the basal and columnar epithelial cells. Desmin filaments, present in smooth muscle cells of the lung, appear to alter their protein structure with age. In early stages of development smooth muscle cells surrounding blood vessels are partly reactive with some cytokeratin antibodies and with a polyclonal desmin antibody. At week 9-10 and week 25 of gestation a monoclonal antibody to desmin, however, is not reactive with blood vessel smooth muscle cells but is only reactive with smooth muscle cells surrounding bronchi. With increasing age the reactivity of cytokeratin antibodies with smooth muscle cells in blood vessels decreases, while the reactivity with the monoclonal desmin antibody increases. Our results show that during differentiation profound changes in the intermediate filament expression patterns occur in the different cell types of the developing lung.

Multicellular aggregates from human tumor cell lines for radiation studies

Aggregates of human tumor cells are widely used in experimental studies on tumor responses to treatment. Only a limited number of human tumor cell lines are capable of forming spheroids. In this study cellular characteristics of 7 lung cancer and 4 bladder cancer cell lines are described with respect to their spheroid forming capacity. Comparisons were made with four reference lines known for their propensity to form growing aggregates. In the absence of vimentin expression no spherical aggregates were formed. Spherical aggregates were formed by one bladder and one lung cancer cell line, of which only the latter exhibited growth. Cellular factors influencing the ability of spheroids to increase in volume after spherical aggregation are not yet defined. Viability and clonogenicity of cells in aggregates are not the determinant of growth capacity. The growth rate of cell lines that exhibited growth is determined by tissue culture conditions and additives. Type of medium, percentage of foetal bovine serum and glucose concentration influenced the growth rate of spheroids. Since the response to radiation may be influenced by the growth rate of the tumors, manipulation of tissue culture medium composition offers the possibility of testing the influence of growth rate on the radiation response of one type of spheroids.

Spontaneous changes in intermediate filament protein expression patterns in lung cancer cell lines

The usefulness of cell lines in the study and prediction of the clinical behaviour of lung cancer is still a matter of debate. However, lung tumour cell cultures have been of value in investigations concerning molecular and cell biological aspects of these neoplasms. Especially in the examination of characteristics specific for the main types of differentiation (squamous cell carcinoma, adenocarcinoma, small cell carcinoma), in vitro studies have been most important. Twenty eight lung cancer cell lines were cultured for up to four years, and were examined at regular intervals for their intermediate filament protein (IFP) expression patterns using a panel of cytokeratin (CK) and neurofilament (NF) antibodies. These studies showed that the classic type of small cell lung cancer (SCLC) cell lines contain CKs 8, 18, and occasionally CK 19, while the variant-type SCLC cell lines generally express no CKs but can contain NFs. Non-SCLC cell lines, such as squamous cell carcinoma and adenocarcinoma cell lines, contain CKs 7 (in most cases), 8, 18 and 19. In one variant SCLC cell line and in one adenocarcinoma cell line CKs 4, 10 and 13, characteristic of squamous cell differentiation, were found. Although most cell lines have remained stable with respect to growth characteristics and IFP expression patterns, five lung cancer cultures exhibited a transition from one cell type to another, paralleled by changes in IFP expression. Progressions from classic to variant SCLC cell lines have been observed, next to conversions from variant SCLC to cell lines re-expressing cytokeratins. In some cases this resulted in a coexpression of CKs and NFs within a cell line and even within individual tumour cells. These results strongly support the earlier finding that CK expression in SCLC cell lines is a reliable marker for the classic type of differentiation, while the absence of CKs and the presence of NFs marks the variant type of differentiation. Our results are discussed in view of previous histological findings.

Quantitative description of classic and variant small cell lung cancer cell lines by nuclear image cytometry

Six small cell lung cancer (SCLC) cell lines were examined using nuclear image analysis to find features characteristic of the classic and the variant type of SCLC. On the basis of their biochemical and biological properties three of these cell lines have been shown to represent the classic types, and three represent the variant type of SCLC. Using a combination of the image-derived run length, density, and geometric features, it was possible to distinguish between the classic and variant SCLC cell lines. The results of this study may be of help in assessing photometric features for the separation of the classic and variant subtypes of SCLC in solid tumors. Because of differences in treatment and prognosis between these two subtypes, such a separation may be of clinical value.

Cytokeratins in different types of human lung cancer as monitored by chain-specific monoclonal antibodies

The expression of cytokeratins (CKs) in human lung cancer was studied using chain-specific monoclonal antibodies to CKs 4, 7, 8, 10, 13, 18, and 19. When applied to adenocarcinomas (ACs) of the lung, high levels of CKs 7, 8, 18, and 19 were detected in all tumors, while CK 4 was found in high concentrations in some ACs. CK 10 and 13 were completely absent, or only present in low numbers of cells. Small cell lung cancers (SCLCs) and lung carcinoids contained CK 18 and sometimes 8 and 19, but no CK 7 in most cases. Three out of four tumors, histologically classified as SCLC, and expressing CK 7 in a variable number of cells were found by electron microscopic studies to contain regions with AC and/or squamous cell carcinoma (SQC) differentiation. The monoclonal antibody specific for CK 7 can therefore possibly help to distinguish AC differentiation within SCLC. CKs 10 and 13 were completely absent in SCLCs and lung carcinoids, while few CK 4-positive cells were found in some SCLCs and in one lung carcinoid. Within SQCs the monoclonal antibodies revealed a pronounced heterogeneity in CK expression. CKs 4, 7, 8, 10, 13, 18, and 19 could be detected, although not evenly distributed among all tumor cells. Highly differentiated SQCs expressed high levels of the CKs specific for squamoid differentiation, i.e., CKs 4, 10, and 13 in variable numbers of cells. With decreasing histologically detectable SQC differentiation these markers were gradually lost, while the number of cells containing CKs 7, 8, 18, and 19 increased. Application of this panel of monoclonal antibodies can therefore distinguish not only the main subtypes of lung cancer, but can also indicate the degree of differentiation and the degree of heterogeneity. These findings can be used as a diagnostic aid in lung tumor pathology, which may have an impact on treatment and prognosis.

Immunocytochemical detection of human lung cancer heterogeneity using antibodies to epithelial, neuronal, and neuroendocrine antigens

Lung cancers were investigated for their heterogeneity as expressed by their immunoreactivity for cytokeratins and neurofilament proteins, as well as for the neuroendocrine differentiation antigen MOC-1. Using broadly cross-reacting antibodies, cytokeratins were detected in nearly all cases of lung carcinomas. Keratinization could be detected only in cases of moderately to well-differentiated squamous cell carcinoma (SQC) using a monoclonal antibody to cytokeratin 10, while a monoclonal antibody reactive with cytokeratin 18, and specific for glandular epithelia, reacted with adenocarcinomas, small cell lung carcinomas (SCLC), and lung carcinoids. In SQC this antibody could detect non-squamous cell differentiation, showing increasing numbers of positive cells with decrease of histologically detectable SQC differentiation. Cells positive for neurofilaments were demonstrated in some of the poorly differentiated SQCs and in some of the cases of SCLC, possibly representing the variant type of SCLC. Also in some of the lung carcinoids neurofilament proteins were present, colocalizing with cytokeratins. MOC-1 was present in all SCLC and lung carcinoids. This antibody could also detect neuroendocrine differentiation in all combined small cell carcinomas, in one poorly differentiated adenocarcinoma, and in about 30% of the poorly differentiated SQCs. Therefore, lung cancer heterogeneity can be detected using a panel of well-defined antibodies to intermediate filaments in combination with the MOC-1 antibody. The use of these antibodies in diagnosis can have prognostic significance and can lead to a more selective therapeutic approach.

Intermediate filament proteins in classic and variant types of small cell lung carcinoma cell lines: a biochemical and immunochemical analysis using a panel of monoclonal and polyclonal antibodies

The intermediate filament protein (IFP) characteristics of a panel of lung cancer cell lines including adenocarcinoma (two cell lines) and small cell lung cancer (SCLC, three classic and three variant cell lines) were examined using one- and two-dimensional gel electrophoretic techniques, immunocytochemical techniques and immunoblotting assays. A panel of 28 monoclonal and polyclonal antibodies to the five different types of IFP were used. The results of our studies indicate that these human lung adenocarcinoma, classic SCLC and variant SCLC cell lines can be differentiated on the basis of their pattern of IFP. The main conclusions from this study can be summarized as follows. The two adenocarcinoma cell lines contain cytokeratins 7, 8, 18, and sometimes 19, next to vimentin intermediate filament (IF). The three classic-type SCLC cell lines contain only cytokeratin IFs but not vimentin IF or neurofilaments (NFs). Cytokeratin polypeptides 7, 8, 18 and 19 could be detected. All three variant-type SCLC cell lines do not contain detectable amounts of cytokeratins. In contrast, two out of three variant SCLC cell lines contain neurofilament proteins. All three variant-type SCLC cell lines contain vimentin IF. Using immunoblotting assays with monoclonal and polyclonal antibodies to defined NF proteins the presence of the 68 X 10(3) Mr and the 160 X 10(3) Mr NF polypeptide could be demonstrated in two variant SCLC cell lines. As patients with SCLC-variant phenotype have a poorer prognosis after cytotoxic therapy than patients with ‘pure’ SCLC, the use of antibodies to IFP in staining fresh lung tumours, especially anaplastic ones, may differentiate the two subtypes of SCLC. Such a distinction would have a major impact on therapy selections and may be of prognostic importance.

Cytopress: automated slide preparation of cytologic material from suspension

This paper describes a new automated system to prepare slides of cytological material from suspension. The system collects material on a filter tape by filtration and transfers it to glass slides by means of pressure-fixation. Using cervical cells as a model, results show that a well-defined cell number is evenly deposited over a standardized area, while a small number of cells is retained on the tape and a negligible number lost in the filtrate. Contamination is very small. Application of the system to other cytological material (fine needle aspirations, monolayer and cell suspension cultures, agar cultures, and isolated nuclei) is shown. In general, more than one slide can be made from one sample. Several histological staining procedures as well as immunofluorescence labeling protocols can be applied to the preparations obtained in this way. This system thus introduces a method that will standardize specimen preparation, is quick, saves operator time, and can be used for both diagnostic and research applications.