Nucleolar antigen found in several human tumors but not in the nontumor tissues studied

Cell cycle regulated expression of nucleolar antigen P120 in normal and transformed human fibroblasts

Normal and SV40 virus-transformed WI-38 human lung fibroblasts were serum starved and refed, or synchronized by double thymidine block and released from the block. At different time points in the cell cycle, steady state levels of P120 mRNA and P120 protein content of the cells were determined by densitometric scans of Northern and Western blots. At the same time points, [3H]thymidine uptake was measured and flow cytometric analysis performed for DNA content and P120 antigen staining. Levels of P120 protein and P120 mRNA were approximately 4 times greater in non-synchronous, exponentially growing transformed cells than in similarly growing normal cells. Early G1-phase cells, synchronized either with serum deprivation or with metabolic block, contained only a trace amount of P120 protein and mRNA. The P120 gene was transcribed early in G1 and P120 protein synthesis initiated in middle G1. A dramatic increase of P120 protein level occurred in S-phase with a corresponding mRNA peak preceding the P120 protein peak. These results indicate that P120 is overexpressed in transformed WI-38 cells and that P120 is temporally regulated during the cell cycle of both transformed and normal fibroblasts. The dramatic increase in P120 protein expression at the G1 to S boundary suggests that P120 may play a role in the regulation of cell cycle and increased nucleolar activity that is associated with cell proliferation.

Immunohistochemical and biochemical characterization of antisera raised to human tumor nucleoli

Antinucleolar antisera were raised in rabbits, goats and sheep to nucleoli isolated from three human tumor cell lines. The antisera were shown to cross-react by immunofluorescence with human tumor cell lines originating from different organs and with frozen sections from a wide variety of human malignant and non-malignant tissues. Tumor versus normal tissue discrimination by several antisera was significantly improved by treatment of frozen tissues with a buffered glutaraldehyde/Triton X-100 solution prior to immunofluorescent staining. The molecular specificity of these antisera was determined by immunostaining electrotransfer nitrocellulose strips following SDS-PAGE of nucleolar preparations and nuclear extracts. Although different immunostaining patterns were obtained for individual antinucleolar antisera, nucleolar proteins of molecular weight 120, 100, 94, 68, 54, 38, 33, and 32 kDa were the most often recognized by antisera raised in the three different species. G187 antiserum strongly reacted with 100, 94, and 38 kDa proteins from freshly obtained leukemic specimens. The Immunoreactivity of the 100, 94, and 38 kDa proteins was unaffected by glutaraldehyde/Triton X-100 treatment when immunostained with antisera that demonstrated the greatest tumor specificity on sections treated with glutaraldehyde/Triton X-100. These three nucleolar proteins may be more highly associated with nucleoli of malignant cells than with nucleoli of normal cells.

Characterization of Novikoff hepatoma small RNAs homologous to repetitive DNAs

Three minor small RNA species from Novikoff hepatoma cells, with homology to repetitive DNA sequences, have been identified and characterized. These small RNAs, designated 5.1S, 6S and T3 RNAs, show homology to Alu 1, Alu 2, and Alu 3 sequences, respectively. 6S and T3 RNAs were found both in the nucleus and cytoplasm, whereas 5.1S RNA was not found in the nucleus. Neural tissues were found to contain a 6S-sized BC1 RNA with homology to I.D. sequences; in contrast, the current study shows that Novikoff hepatoma cells contain a 75-80 nucleotide long (T3) RNA, homologous to I.D. sequences. These data suggest that BC1 and T3 small RNAs, homologous to I.D. sequences, are expressed in a tissue-specific manner. These results also show that in addition to the abundant 7SL, 4.5S and 4.5S1 RNAs having homology to repetitive DNA, Novikoff hepatoma cells also contain several minor small RNAs with homology to repetitive sequences.

A monoclonal antibody (HO-No-1) with specificity for a human nucleolar protein

A murine monoclonal antibody (named HO-No-1) which specifically reacts with a target antigen of 72,000 mol. wt (p72) in the nucleoli of human cells, has been isolated. Using an avidin-biotin peroxidase immunoperoxidase method, it was found that this antibody stains exclusively the nucleolus and not other portions of the nucleus and cytoplasm. This reaction pattern was observed consistently, although to different degrees in 14 human normal tissues and human malignant cell lines. However, after pretreatment with actinomycin D (250 ng/ml) for 2 h, the antibody stains the nucleoplasm uniformly. Thus this study demonstrates evidence for an antibody which reacts specifically with human nucleoli to a protein which could play an important role in rRNA synthesis.

Identification of "tumor-associated" nucleolar antigens in human urothelial cancer

Nucleoli isolated from HeLa S3 cells were used to produce rabbit antisera capable of binding nucleoli of transitional cell carcinomas (TCCa) of the bladder. Cross-reactivity of the rabbit antiserum with normal nucleoli was reduced by absorption with fetal calf serum, normal human serum, and human placental nucleoli. This antinucleolar antiserum exhibited strong reactivity in immunoperoxidase assays performed on specimens of human bladder cancer. In frozen tissue sections of 24 patients with TCCa and eight individuals without tumor, nucleolar staining was observed in all malignant specimens, but was not observed in seven of the normal specimens. Cytologic examination of bladder washing specimens from 47 normal individuals showed absence of nucleolar staining in 43 (91%) of 47 normal specimens while 12 (86%) of 14 specimens from patients with TCCa were positive. These results suggest that there are antigens associated with the nucleoli of HeLa cells and transitional cell carcinomas which are generally absent (or in low concentration) in normal human urothelial cells, and that antisera to these antigens may be useful in the cytologic diagnosis of human transitional cell carcinoma.

Double immunoenzymatic labeling of lymphomatous tissues for both immunologic phenotype and a malignancy-associated nucleolar antigen

Defining cell lineage in the non-Hodgkin's lymphomas (NHL) is challenging for the immunopathologist. Cell surface marker techniques have made a major contribution to the understanding of the biology and classification of lymphoproliferative disorders by permitting the determination of the lymphoid (B- or T-cell) or monocytic lineage of the tumors. Because lymphoma cells often simulate the morphologic features and cell surface phenotype of their normal lymphocytic counterparts, it is difficult to discriminate normal from neoplastic lymphocytes. The authors have used representative monoclonal antibodies (MAb) to cell surface antigens to assess tumor cell surface antigens associated with various lymphoreticular cell lineages. Heteroantisera to the human malignancy-associated nucleolar antigen (HMNA) was utilized as a marker for neoplastic lymphoid cells as previously described. The use of double immunoenzymatic staining with both peroxidase and alkaline phosphatase allow us simultaneously to determine lymphoid lineage and malignancy on human lymphoma cells. In 101 cases of various cell types of NHL, the anti-HMNA antiserum reacted with nucleoli in the morphologically neoplastic lymphoma cells, but not with normal-appearing lymphoid and other cell types present in the lesions. Control specimens from normal and hyperplastic lymphoid tissue also failed to react with anti-HMNA antibodies.

The technique of premature chromosome condensation to study the leukemic process: review and speculations

The technique of premature chromosome condensation involves the fusion of mitotic cells with interphase cells resulting in the immediate condensation of the interphase chromatin into discrete chromosome units, the prematurely condensed chromosomes (PCC). The ability to visualize the interphase chromosomes of bone marrow and blood cells by this technique has proved useful in the study of human leukemia. This article describes how the PCC technique has been used to predict clinical outcome as well as gain insight into the biology of leukemia.

Antibodies directed against guanylic acid and guanosine are nucleolus specific probes

Purified antibodies against guanylic acid and guanosine binding to RNA at guanosine residues were used to probe human lymphocyte preparations by indirect immunofluorescence. Neither antibody gave any banding pattern with metaphase chromosomes but both showed binding to specific sites in the interphase nuclei. Evidence presented indicates that these sites are guanosine residues on rDNA transcripts at the nucleolar organizer regions.

The spectrum of complement-fixing antinuclear antibodies in patients with hepatocellular carcinoma

Sera from 230 hepatocellular carcinoma patients were tested for antinuclear antibodies by anticomplement immunofluorescence in 16 types of transformed, diploid or primary cells of human, monkey, chimpanzee or rat origin. As controls, we tested 85 sera from patients with chronic liver diseases, 48 sera from patients with nonhepatic cancers and 164 sera of normal controls. Exactly 11.2% of all cancer patients but only 3.6% of noncancer patients had complement-fixing antinuclear antibody that reacted with all substrates. Only sera from hepatocellular carcinoma reacted with subsets of the tumor cell substrates. These sera reacted with hepatocellular carcinoma cells and nonhepatic cancer cells (antitumor) or only with one or more of the human hepatocellular carcinoma cell lines, PLC/PRF/5, Hep3B and Mahlavu, that were derived from HBsAg-positive patients (antihepatocellular carcinoma). Three of these reacted only with hepatitis B virus DNA-positive cells (PLC/PRF/5 and Hep3B) that contained "hepatitis B-associated nuclear antigen," 1 reacted only with hepatitis B virus DNA-negative Mahlavu cells, 1 reacted with PLC/PRF/5 and Mahlavu and 3 reacted with all 3 cells. The nuclear antigen in Mahlavu was expressed as a homogeneous fluorescence that spared the nucleoli, was present in a lower percentage of cells than hepatitis B-associated nuclear antigen and was more thermostable than hepatitis B-associated nuclear antigen. However, it resembled hepatitis B-associated nuclear antigen in kinetics of expression and susceptibility to digestion with DNase, RNase and proteinase K. The nature of the nuclear antigens in the hepatocellular carcinoma cells is poorly understood but one possibility is that they may represent the expression of viral or tumor-related genes.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophoretic analysis of HeLa cell and human liver nucleolar proteins and antigens

The major antigens in HeLa nucleolar extracts recognized by immunoblots with rabbit antisera had molecular weights of 145, 110, and 34 kd. The major antigens in the HeLa nucleolar residues had molecular weights of 145, 110, 86, 68, 55, 48, and 34 kd. In the liver, the major antigens in the nucleolar extracts had molecular weights of 86 and 76 kd. In the liver residues, the major antigens had molecular weights of 110, 86, 76, 65, and 55 kd. On two-dimensional gels stained with Coomassie blue, the HeLa nucleolar extract contained large amounts of protein B23 and lesser amounts of protein C23. In the liver nucleolar samples separated on two-dimensional (2-D) gels, protein 55/7.6 (Mr/pI) was the major protein in the extract. Lesser amounts of protein B23 were identified. Addition of protease inhibitors markedly improved the quality of the protein samples as shown in one-dimensional gel patterns for liver nucleolar proteins and to a lesser extent for HeLa nucleolar proteins. In the 2-D immunoblots of the HeLa extract and HeLa residues, the major stained band was protein C23 (110/5.2-5.6). In the liver extract, the major bands were 70/5.8-7 and 60/5.8-7. With a monoclonal antibody (MS-3) to protein C23 a 76/5.8 band was more notable in the residue which supported the results of the Coomassie blue and immunostains with rabbit antinucleolar antibodies. Some degradation products of protein C23 were observed in both the liver extract and the liver residue despite the use of protease inhibitors. Protein C23 along with other proteins are major antigens in HeLa nucleoli. In human liver nucleoli, a major protein 55/7.6 was identified which was not observed in the HeLa extracts. These studies show that a combination of protease inhibitors markedly reduced degradation of proteins in liver samples and provided a more satisfactory sample for comparison with HeLa cells. Qualitative and quantitative differences were found in the nucleolar proteins by Coomassie blue and immunostaining.

A human nucleolar antigen (pp90) associated with cell growth and its induction by Epstein-Barr virus and human cytomegalovirus

Immunofluorescent staining of HeLa cells with rabbit antiserum raised against isolated HeLa cell nucleoli showed bright nucleolar fluorescence. Immunoprecipitation of nuclear extracts obtained from HeLa cells labelled with 35S-methionine or 32P-orthophosphate followed by gel electrophoresis of the precipitate revealed a major band of 90 kd. This antigen, called pp90, was judged to be responsible for the nucleolar fluorescence. Serine residues were predominantly phosphorylated in pp90. Similar nucleolar fluorescence was observed commonly in human cells derived from malignant tumors including acute lymphatic leukemia, adult T-cell leukemia, hepatitis B virus-associated hepatoma, adenocarcinoma, and in 5 lymphoid cells derived from Burkitt lymphoma but not in normal human lymphocytes or liver cells. In immunoprecipitation, 32P-labelled pp90 was commonly detected as the major component in all of those cells which showed nucleolar fluorescence. Resting human embryo lung (HEL) cells were negative for both nucleolar fluorescence and pp90 in immunoprecipitation, but turned positive when stimulated to grow, suggesting the involvement of pp90 in cell growth. Antigen pp90 was also induced in human lymphocytes and HEL cells by infection with Epstein-Barr virus in human cytomegalovirus, respectively, which are known to induce cell DNA synthesis in early stages of infection. A cross-reacting nucleolar antigen was detected in 2 monkey cells but not in 3 rodent cells tested.

A monoclonal antibody (HNo-g7) with specificity for a human nucleolar protein

A murine monoclonal antibody which reacts strongly with the nucleoli of human epithelial cells has been isolated. The antibody is of the IgM class and the antigen has a molecular weight of 45 000. The antibody appears to react with interphase chromatin only and to have specificity for epithelial cells.

Proliferating cell nuclear antigen (PCNA) and human malignant tumor nucleolar antigens (HMTNA) in nucleoli of human hematological malignancies

Lymphoma (Lymphocytic non-Hodgkin's malignant lymphoma) and leukemic (chronic lymphocytic, acute and chronic myeloid, myelomonocytic leukemia) cells were studied by indirect immunofluorescence to evaluate the presence of proliferating cell nuclear antigen (PCNA) and human malignant tumor nuclear antigen (HMTNA) in their nucleoli. Most cells in lymph node smears of lymphocytic non-Hodgkin's malignant lymphoma (NHML) developed a bright nucleolar fluorescence with HMTNA antibodies. PCNA was detected in nucleoli of a limited number of cells which apparently represent the proliferating cell population in these lymphomas. Similarly, in the bone marrow smears of patients with chronic lymphocytic leukemia most cells possessed a nucleolar fluorescence for HMTNA and PCNA was present in nucleoli of a limited number of cells. In the bone marrow smears of patients with myeloid or myelomonocytic leukemias most blastic or monocytoid cells also developed a bright nucleolar fluorescence with HMTNA antibodies and PCNA was present only in a small percentage of these cells. Leukemic cells with PCNA in their nucleoli like thekhuntigen might represent a proliferating cell population in late G1-early S phase.

Identification and purification of Namalwa nuclear RNP antigen 52/5.3

Using affinity purified rabbit antibodies to HeLa nucleoli and the Western blotting techniques, an antigen with an approximate molecular weight of 52,000 and pI of 5.3 was found in Namalwa cells (a Burkitt lymphoma), but not in normal liver cells. This antigen was purified from Namalwa RNP by column chromatography on Sephacryl S-200, hydroxylapatite and one-dimensional SDS gel electrophoresis. A liver protein with the same molecular weight and pI value was purified from RNP fraction by one-dimensional SDS gel electrophoresis. Both proteins had similar amino-acid compositions. The tryptic map of 125I-labeled protein 52/5.3 contained approximately nine major spots; spot 9 was present in the Namalwa protein but not in the liver protein. The similarity of the structures of these proteins and their differences in antigenicity are noteworthy and require further structural and functional analysis.

Enzyme-linked immunosorbent assay for use with nuclear protein-DNA complex antigens

An enzyme-linked immunosorbent assay (ELISA) was developed for identification and quantification of nuclear antigens (nonhistone protein-DNA complexes from chromatin). Until now, the complement fixation assay has been the only immunoassay routinely applied to nonhistone protein-DNA complexes. The ELISA is considerably more sensitive than the micro-complement fixation test for assaying the immunospecificity of nuclear protein-DNA complexes. Dilutions of rabbit antisera as great as 1:6400 could be used to detect nanogram quantities of antigen, chicken reticulocyte chromatin or dehistonized rat liver chromatin.

Ultrastructural and purification studies on human tumor nucleolar antigens and nucleolar particles

The presence of common nucleolar antigens in a broad array of human malignant tumors has led to several lines of investigations. In addition to studies on an increasing number of benign and malignant neoplasms with a variety of antibodies designed to statistically evaluate the presence of nucleolar antigens, purification procedures and chemical analyses are being used to characterize the specific antigens. The localization of the nucleolar antigens in HeLa cells was studied by the postembedding immunoelectron microscopic procedure employing rabbit antibodies to nucleoli or nuclear Tris extracts of these cells. The products of the peroxidase-antiperoxidase complexes visualized by the reaction with diaminobenzidine in nucleoli were mainly found in the nucleolonemas which contain the dense nucleolar RNP components. When these nucleoli became compact after treatment of HeLa cells with adriamycin, the distribution of the immunoreactive products was altered along with distribution of the dense nucleolar components. The human nucleolar antigens were mainly localized to nucleolar regions containing the nucleolar RNP components. Improved purification of the antigens made it possible to provide a satisfactory amino acid analysis of one pI 6.3 antigen. Interestingly, some of the nucleolar antigen was found in miniparticle undescribed until now.

Immunological localization of a major karyoskeletal protein in nucleoli of oocytes and somatic cells of Xenopus laevis

Oocyte nuclei of Xenopus laevis contain two major karyoskeletal proteins characterized by their resistance to extractions in high salt buffers and the detergent Triton X-100, i.e. a polypeptide of 68,000 mol wt which is located in the core complex-lamina structure and a polypeptide of 145,000 mol wt enriched in nucleolar fractions. Both proteins are also different by tryptic peptide maps and immunological determinants. Mouse antibodies were raised against insoluble karyoskeletal proteins from Xenopus oocytes and analyzed by immunoblotting procedures. Affinity purified antibodies were prepared using antigens bound to nitrocellulose paper. In immunofluorescence microscopy of Xenopus oocytes purified antibodies against the polypeptide of 145,000 mol wt showed strong staining of nucleoli, with higher concentration in the nucleolar cortex, and of smaller nucleoplasmic bodies. In various other cells including hepatocytes, Sertoli cells, spermatogonia, and cultured kidney epithelial cells antibody staining was localized in small subnucleolar granules. The results support the conclusion that this "insoluble" protein is a major nucleus-specific protein which is specifically associated with--and characteristic of--nucleoli and certain nucleolus-related nuclear bodies. It represents the first case of a positive localization of a karyoskeletal protein in the nuclear interior, i.e. away from the pore complex-lamina structure of the nuclear cortex.

Isolation and partial characterization of a nuclear antigen (68/6.3) from the Namalwa cell line (a Burkitt lymphoma)

A nuclear antigen was purified from the 0.01 M Tris-HCl/pH8 extract of nuclei of the Burkitt tumor Namalwa cell line to electrophoretic homogeneity by DEAE cellulose chromatography, affinity chromatography, and preparative isoelectric focusing. The yield of antigens was 0.02% of the nuclear 0.01 M Tris-HCl/pH8 extract. On two-dimensional gel electrophoresis, the major antigen separated into two adjacent protein spots with molecular weights of 68,000 and an approximate pI of 6.3 (68/6.3 A and 68/6.3 B). A minor antigen had a molecular weight of 61,000 and pI of 6.0 (61/6.0). Fourteen 125I-labeled peptides were obtained from the tryptic digest of the major antigen (68/6.3 A and 68/6.3 B). The amino-acid composition analysis of the purified antigens indicated that the amino acids in the highest content were glycine (15%), glutamic acid (11.6%), and serine (9%); the ratio of acidic to basic amino acids was 1.95. In studies on nucleolytic activity, the purified antigen produced a single-stranded and then a double-stranded cleavage of PM 2 and pBR 322 DNA. This antigen is the first purified nuclear antigen that reacts with the HeLa-specific nucleolar antibodies.

Nucleolar immunofluorescence in bone marrow specimens of human hematological malignancies

Leukemic cells and myeloma cells were studied in bone marrow of untreated patients with acute and chronic myeloid leukemia, chronic lymphocytic leukemia, and multiple myeloma to provide more information on the nucleolar immunofluorescence produced by antibodies no nucleoli of HeLa cells. The nucleolar immunofluorescence was mainly observed in myeloblasts of myeloid leukemias an in immature as well as mature cells of the plasmacytic or lymphocytic cell lines of multiple myeloma or chronic lymphocytic leukemia. With respect to the nucleolar immunofluorescence, both positive and negative populations of cells were noted in the specimens of all patients studied.