Production and characterization of monoclonal antibody against 10S DNA polymerase alpha from calf thymus

Monoclonal antibodies as diagnostics; an appraisal

Ever since the development of Hybridoma Technology in 1975 by Kohler and Milstein, our vision for antibodies as tools for research for prevention, detection and treatment of diseases, vaccine production, antigenic characterization of pathogens and in the study of genetic regulation of immune responses and disease susceptibility has been revolutionized. The monoclonal antibodies being directed against single epitopes are homogeneous, highly specific and can be produced in unlimited quantities. In animal disease diagnosis, they are very useful for identification and antigenic characterization of pathogens. Monoclonal antibodies have tremendous applications in the field of diagnostics, therapeutics and targeted drug delivery systems, not only for infectious diseases caused by bacteria, viruses and protozoa but also for cancer, metabolic and hormonal disorders. They are also used in the diagnosis of lymphoid and myeloid malignancies, tissue typing, enzyme linked immunosorbent assay, radio immunoassay, serotyping of microorganisms, immunological intervention with passive antibody, antiidiotype inhibition, or magic bullet therapy with cytotoxic agents coupled with anti mouse specific antibody. Recombinant deoxyribonucleic acid technology through genetic engineering has successfully led to the possibility of reconstruction of monoclonal antibodies viz. chimeric antibodies, humanized antibodies and complementarily determining region grafted antibodies and their enormous therapeutic use.

Engagement of DNA polymerases during apoptosis

DNA replicative and repair machinery was investigated by means of different techniques, including in vitro nuclear enzymatic assays, immunoelectron microscopy and confocal microscopy, in apoptotic cell lines such as HL-60 treated with methotrexate, P815 and K562 exposed to low temperatures and Friend cells exposed to ionizing radiation. The results showed a shift of DNA polymerase alpha and beta activities. DNA polymerase alpha, which in controls was found to be the principal replicative enzyme driving DNA synthesis, underwent, upon apoptosis, a large decrease of its activity being replaced by DNA polymerase beta which is believed to be associated with DNA repair. Such a modulation was concomitant with a topographical redistribution of both DNA polymerase alpha and the incorporation of BrdUrd throughout the nucleus. Taken together, these results indicate the occurrence of a dramatic response of the DNA machinery, through a possible common or at least similar behaviour when different cell lines are triggered to apoptosis. Although this possibility requires further investigation, these findings suggest an extreme attempt of the cell undergoing apoptosis to preserve its nuclear environment by switching on a repair/defence mechanism during fragmentation and chromatin margination.

Induction of apoptosis in a human hepatocellular carcinoma cell line by a neutralizing antibody to transforming growth factor-alpha

A cell line derived from a Japanese man with hepatocellular carcinoma was established in culture and designated OCUH-16. The cell line has the morphological and chromosomal features of hepatocellular carcinoma cells and has a short doubling time (approximately 33 h). OCUH-16 cells were shown to express transforming growth factor-alpha (TGF-alpha) in addition to albumin, DNA polymerase-alpha, c-JUN, and the retinoblastoma gene product. Electron microscopy revealed TGF-alpha immunoreactivity associated with the cell membrane, but TGF-alpha was not detected in medium conditioned by OCUH-16 cells by enzyme-linked immunosorbent assay. Reverse transcription and polymerase chain reaction analysis revealed the presence of TGF-alpha messenger RNA in these cells. Culture of OCUH-16 cells in the presence of a neutralizing antibody to TGF-alpha inhibited cell proliferation and induced many cells to undergo apoptosis (programmed cell death). These observations suggest that endogenous TGF-alpha is necessary for OCUH-16 cell growth.

Expression of antigens related to apoptosis and cell proliferation in chronic nonsuppurative destructive cholangitis in primary biliary cirrhosis

The initial injury in primary biliary cirrhosis (PBC) is the destruction of portal bile ducts. Little information is available on apoptosis and cell proliferation in such bile ducts, so we used immunohistochemical techniques to locate molecules related to apoptosis [Fas antigen, Lewis Y antigen (BM1/JIMRO), and bcl-2 protein] and to cell proliferation (proliferating cell nuclear antigen, PCNA) in 21 patients with PBC. In addition, nick-end labelling was done to locate DNA fragmentation. The expression of these molecules in chronic nonsuppurative destructive cholangitis (CNSDC) was examined. Cell death and PCNA expression were both found in portal bile ducts affected by CNSDC in 7 of the 13 CNSDC patients examined. Fas antigen was found on the plasma membrane and rough endoplasmic reticulum of bile-duct cells with CNSDC in the frozen sections of all 6 patients with CNSDC out of the 9 patients inspected, and this antigen was found also in bile-duct cells without CNSDC in 2 of these 9 patients. It was not found in anatomically normal liver (from 2 patients with Gilbert's disease). The Lewis Y antigen was found in bile ducts with CNSDC and in proliferated ductules in all 16 patients examined. No bcl-2 protein was found in any bile-duct or ductule cells, but it was found in the cytoplasm of lymphocytes surrounding or invading CNSDC. DNA fragmentation was found in the nuclei of bile-duct cells with CNSDC by nick-end labelling. Our study indicated that Fas-mediated apoptosis might be involved in CNSDC, but that bcl-2 protein seems to participate less than Fas. Although the Lewis Y antigen was found in many bile ducts, the relationship between the antigen and apoptosis remains unknown because there was no evidence that this antigen mediates apoptosis.

On the presence of DNA polymerase alpha in human lymphocyte nuclei and chromosomes

Experiments were carried out to correlate the cytological localization of DNA polymerase alpha with the presence of its specific mRNA in human lymphocytes studied at different times after phytohaemagglutinin stimulation. Our data indicated that in resting cells it is not possible to detect DNA polymerase alpha protein or mRNA by Northern hybridization. By contrast, in stimulated cells the detection of mRNA specific for DNA polymerase alpha synthesis is possible after 16 h phytohaemagglutin stimulation, whereas immunolocalization is possible after only 4 h stimulation. Observation of cytological preparations from cells stimulated for times long enough to obtain mitoses surprisingly showed an intense immunoreaction in mitotic chromosomes treated with monoclonal antibodies to DNA polymerase alpha.

Immunohistochemical analysis of retinoblastoma gene product (pRB) expression in malignant and non-malignant liver diseases

The retinoblastoma gene product is a nuclear phosphoprotein that undergoes cell cycle-dependent changes in its phosphorylation status. To analyze the expression of retinoblastoma gene product in the process of liver regeneration and the initiation of hepatocellular carcinoma, we studied immunohistochemically the expression of retinoblastoma gene product and DNA polymerase alpha (DPA) in 33 patients with various liver diseases. Only a few hepatocytes positive for retinoblastoma gene product were found in undamaged, nonregenerating liver tissues, whereas many hepatocytes positive for retinoblastoma gene product were detected in specimens of regenerating liver obtained from patients with acute or chronic liver diseases. Similarities were found between distribution patterns of hepatocytes positive for retinoblastoma gene product and those of hepatocytes positive for DPA, and a highly significant positive correlation was found between the number of hepatocyte nuclei stained for retinoblastoma gene product per 1000 nuclei examined (R-LI) and the number of hepatocyte nuclei stained for DPA per 1000 nuclei examined (D-LI) in tissues obtained from patients with nonmalignant liver disease. Hepatocellular carcinoma cells positive for DPA were detected in the 14 hepatocellular carcinoma specimens tested. In ten of these specimens, hepatocellular carcinoma cells positive for retinoblastoma gene product were found but not in the other four. For all hepatocellular carcinoma specimens, R-LI was proportional to D-LI. Thus in both nonmalignant and malignant liver, retinoblastoma gene product increased in proportion to proliferation of hepatocytes or hepatocellular carcinoma cells.

The significance of nucleolar organizer region (AgNOR) score in predicting meningioma recurrence

BACKGROUND

Argyrophilic nucleolar organizer region (AgNOR) has been demonstrated in recent studies of human brain tumors, including meningiomas. The authors used this technique in meningiomas to analyze whether the mean numbers of AgNOR per nucleus (AgNOR score) are related to the recurrence rate or the proliferative potential of meningiomas.

METHODS

AgNOR staining technique was applied to paraffin-embedded sections of 60 meningiomas. Twenty of these specimens also were investigated immunohistochemically with monoclonal antibody (MoAb) against DNA polymerase alpha (Pol.alpha) and with MoAb Ki-67 to compare the AgNOR score with the proliferative potential.

RESULTS

There was a statistically significant difference between the AgNOR score in nonrecurrent meningiomas (2.48 +/- 0.73) and recurrent histologically benign meningiomas after gross total resection (3.20 +/- 0.96) (P < 0.02). The recurrence rate of tumors after gross total resection with an AgNOR score of 3.0 or more was significantly higher than that with an AgNOR score of less than 3.0. The AgNOR score did not always correlate with Pol.alpha or Ki-67 score; the AgNOR score of malignant meningioma that had high proliferative score was not always high.

CONCLUSIONS

This study indicates that AgNOR staining appears to be a simple and useful method for estimating the probability of histologically benign meningioma recurrence even after gross total resection.

Sulfate- and sialic acid-containing glycolipids inhibit DNA polymerase alpha activity

The effects of various glycolipids on the activity of immunoaffinity-purified calf thymus DNA polymerase alpha were studied in vitro. Preincubation with sialic acid-containing glycolipids, such as sialosylparagloboside (SPG), GM3, GM1, and GD1a, and sulfatide (cerebroside sulfate ester, CSE) dose-dependently inhibited the activity of DNA polymerase alpha, while other glycolipids, as well as free sphingosine and ceramide did not. About 50% inhibition was achieved by preincubating the enzyme with 2.5 microM of CSE, 50 microM of SPG or GM3, and 80 microM of GM1. Inhibition was noncompetitive with both the DNA template and the substrate dTTP, as well as with the other dNTPs. Since the inhibition was largely reversed by the addition of 0.05% Nonidet P40, these glycolipids may interact with the hydrophobic region of the enzyme protein. Apparently, the sulfate moiety in CSE and the sialic acid moiety in gangliosides were essential for the inhibition since neither neutral glycolipids (i.e., glucosylceramide, galactosylceramide, lactosylceramide) nor asialo-gangliosides (GA1 and GA2) showed any inhibitory effect. Furthermore, the ceramide backbone was also found to be necessary for maximal inhibition since the inhibition was largely abolished by substituting the lipid backbone with cholesterol. Increasing the number of sialic acid moieties per molecule further enhanced the inhibition, while elongating the sugar chain diminished it. It was clearly shown that the N-acetyl residue of the sialic acid moiety is particularly essential for inhibition by both SPG and GM3 because the loss of this residue or substitution with a glycolyl residue completely negated their inhibitory effect on DNA polymerase alpha activity.

Flow cytometric detection of proliferative cells in leukemias

We studied the proliferative activity of leukemic cells obtained from the peripheral blood and bone marrow of 34 patients; 30 with acute leukemia and 4 with chronic myelogenous leukemia in blastic crisis. Flow cytometry was performed using monoclonal antibody against DNA polymerase alpha. Since fresh and frozen cells showed virtually identical DNA polymerase alpha-positive populations and flow cytometric histograms, 52 cryopreserved samples (25 from peripheral blood and 27 from bone marrow) were used in this study. The DNA polymerase alpha-positive population ranged from 20.4% to 84.7% in peripheral blood, and from 6.5% to 92.1% in bone marrow. A positive correlation (r = 0.76, P < 0.01) was found between DNA polymerase alpha-positive populations in peripheral blood and bone marrow from the same patient. This suggests that the DNA polymerase alpha-positive population in the bone marrow can be estimated from that in peripheral blood. No relationship was observed between the positive population and the response to chemotherapy. Statistical analyses for all cases showed no relationship between the DNA polymerase alpha-positive population and either the tumor cell count or time to reach a nadir. However, a negative correlation was observed between the positive population in bone marrow samples and the time to reach a nadir (r = -0.64, P < 0.05) in those patients who achieved a complete response. In addition, in the cases of acute non-lymphocytic leukemia who did not respond to chemotherapy, a positive correlation was observed between the tumor cell count in bone marrow and the DNA polymerase alpha-positive population (r = 0.93, P < 0.01). Thus, the method described here provides a simple and time-efficient means of detecting the proliferative activity of leukemic cells, which is a useful parameter in the treatment of leukemia.

Detection of the preneoplastic lesions of small hepatocellular carcinoma in cirrhotic livers

To identify the preneoplastic lesions of hepatocellular carcinoma and the fine structure of preneoplastic hepatocytes, we studied proliferative conditions in cirrhosis of the liver. In all, 46 foci of cellular alteration (FCA), three regions of adenomatous hyperplasia (ADH), and 21 small hepatocellular carcinomas (sHCC) were studied by published criteria for sHCC and by the proliferative activity of the lesions as examined with monoclonal antibodies against DNA polymerase alpha and proliferating cell nuclear antigen. The four patients with FCA composed of basophilic hepatocytes were classified by the criteria as having sHCC; cells had features similar to those of sHCC. Two of these four patients with FCA were found to have HCC several years later. The number of hepatocytes stained for proliferating cell nuclear antigen was 72 and 81 per 1000 hepatocyte nuclei in the two patients who developed HCC. In one of the three patients with ADH, a sHCC was found 1 year later, and dysplastic hepatocytes from the region of ADH in this patient had features similar to those of HCC cells by light and electron microscopy. In this patient, the number of hepatocytes stained for DNA polymerase alpha was 452 per 1000 nuclei. Therefore, FCA and ADH might be preneoplastic lesions of sHCC in cirrhosis of the liver. Preneoplastic hepatocytes seem to be small cells with basophilic cytoplasm, with a large nucleus to cytoplasm ratio, finely indented nuclei with a smaller amount of condensed chromatin than normal, and poorly to moderately developed organelles.

Distribution of asialoglycoprotein receptor in human hepatocellular carcinoma

Altered expression of asialoglycoprotein (ASGP) receptors on hepatocytes has been reported during hepatic neoplasia mostly in animal models. In this study, we examined immunohistochemically the distribution of the ASGP receptor in humans with various liver diseases, including ten cases of hepatocellular carcinoma (HCC). In livers of acute hepatitis, chronic hepatitis, cirrhosis and the non-cancerous tissues (mostly cirrhosis) adjacent to HCC, the receptor was present in its normal distribution, i.e. mostly along the sinusoidal margin and partly on the lateral surface of hepatocytes. In four of six well-differentiated HCCs, the receptor was also normally distributed on the plasma membrane; by immunoelectron microscopy, it was seen in the endoplasmic reticulum and in pits in the plasma membrane but not on bile canaliculus-like structures, suggesting that it was synthesized, transported, and integrated into the plasma membrane in a polar manner. In contrast, there was no surface expression of the ASGP receptor in the remaining six HCCs (two well-differentiated and four poorly differentiated). In two of the poorly differentiated HCCs, the receptor, although absent from the cell surface, was prominent in the endoplasmic reticulum, suggesting disturbed transport of the ASGP receptor to the cell surface. When we examined proliferative activity of HCCs by immunohistochemical labeling of DNA polymerase alpha, HCCs with high percentages (above 30%) of DNA polymerase alpha-positive cells had lost the cell-surface expression of the receptor. Thus, the expression of the ASGP receptor in human HCC appears to be closely related to differentiation and proliferative activity of the tumor cells.

Natural killer cell may impair liver regeneration in fulminant hepatic failure

The authors established a new experimental model of fulminant hepatic failure (FHF) with prolonged hepatocellular necrosis and impaired liver regeneration, and evaluated the immunological mechanisms related to the impaired liver regeneration in this model. A novel lipid A analogue, FS-112, was injected intravenously into male Balb/c mice, followed by a 70% partial hepatectomy 2 days later. Serum levels of T.Bil. and ALT rose 7 days after the partial hepatectomy, as compared with controls. In mice pretreated with FS-112, labeling indices of both BrdU and PCNA 36 hrs after the partial hepatectomy were significantly lower than those in the controls. Splenic lymphocytes harvested from the FHF mice 1-5 days after the partial hepatectomy showed a cytotoxic activity against regenerating hepatocytes with a peak effect on day 5. Cytotoxic activity against YAC-1 cells was also found up to 5 days after the partial hepatectomy, and resembled that directed against the regenerating hepatocytes. On the 5th day of FS-112 administration, there was a marked rise in the production of IFN-gamma from splenocytes. When FK-506, an immunosuppressive agent, was given intracutaneously daily for 7 days, serum levels of T.Bil. and ALT significantly decreased, as compared with controls. Furthermore, the PCNA-labeling index 36 hrs after the partial hepatectomy was enhanced by the administration with FK-506 in the FHF mice. These results strongly suggest that the NK cells activated by IFN-gamma may be involved in killing the regenerating liver cells, and thus play a role in the pathogenesis of the impaired liver regeneration in FHF.2+ recovery from the impaired liver regeneration in FHF.

Analysis of proliferating biliary epithelial cells in human liver disease using a monoclonal antibody against DNA polymerase alpha

The proliferative activity and ultrastructural characteristics of proliferating biliary epithelial cells were analysed immunohistocytochemically in 39 biopsied liver specimens from patients with acute viral hepatitis, chronic hepatitis and liver cirrhosis using a monoclonal antibody against DNA polymerase alpha (DNA-PA). In acute viral hepatitis with perivenular confluent necrosis, proliferation of typical bile ducts was found frequently in portal areas. In chronic aggressive hepatitis and cirrhosis, ductular proliferation of both typical and atypical forms was found in enlarged portal and periportal areas and in confluent necrotic areas. The number of proliferating biliary epithelial cells that stained positive for DNA-PA was small. There were very few positively stained cells in atypical bile ducts in confluent necrotic areas of cirrhosis. Atypical bile ducts seen in chronic aggressive hepatitis, cirrhosis and acute hepatitis with confluent necrosis were positively stained for both cytokeratins 8 and 19. In cirrhosis, the number of stained biliary epithelial cells in typical bile ducts was larger than the number of such cells in atypical bile ducts (P < 0.01). By electron microscopy, the cells positively stained for DNA-PA were mostly so-called clear cells with irregular nuclei containing coarse nucleoplasm, and a few small cells with scanty cytoplasm and few organelles.

Proliferative potential of brain tumors. Analyses with Ki-67 and anti-DNA polymerase alpha monoclonal antibodies, bromodeoxyuridine labeling, and nuclear organizer region counts

Histochemical analyses with Ki-67 and anti-DNA polymerase alpha monoclonal antibodies were done, and argyrophilic nucleolar organizer regions (Ag-NOR) were counted to estimate the proliferative potential of 200 brain tumors. The findings were compared with the bromodeoxyuridine labeling index (BrdU LI), or S-phase fraction. The proliferating cell indexes (PCI), determined by Ki-67 and anti-DNA polymerase alpha monoclonal antibodies were higher and Ag-NOR more numerous in medulloblastomas, glioblastomas, and metastatic carcinomas than in astrocytomas or meningiomas. The Ki-67 and DNA polymerase alpha PCI correlated with the BrdU LI (r = 0.87 and r = 0.84, respectively) and with each other (r = 0.94). The number of Ag-NOR correlated less strongly with these indexes in some tumors. These findings suggest that Ki-67 and anti-DNA polymerase alpha monoclonal antibodies may be useful for estimating the proliferative potential of individual tumors in routine clinical practice. The number of Ag-NOR, however, does not always reflect the growth potential of each tumor.

Expression of p53 protein in colorectal cancer and its relationship to short-term prognosis

BACKGROUND AND METHODS

The expression of p53 protein in 100 large bowel cancers was studied immunohistochemically by use of a monoclonal antibody (PAb1801).

RESULTS

Immunoreactivity was found in 61.0% of specimens from 100 patients with colorectal cancer. The pattern of p53 expression was mainly detected in the nuclei of the cancer cells. There was no significant correlation between the expression of p53 and the histologic grade, tumor size, serosal invasion, lymphatic invasion, venous invasion, lymph node metastasis, or liver metastasis. However, patients with p53-positive tumors had a greater relative risk of death compared with those with p53-negative tumors. The p53 negative-tumors showed a recurrence rate of 5.9%; for the p53 positive-tumors, a recurrence rate of 23.8% was recorded. The 3-year survival rate was 96.7% of 39 patients with p53-negative carcinomas and 61.8% for the patients with p53-positive tumors; there was a significant difference in the rate between the two groups of patients (P < 0.05). The growth fraction of p53-positive tumors determined with a monoclonal antibody against DNA polymerase alpha (49.0%) was significantly higher than that of p53-negative tumors (40.7%, P < 0.01).

CONCLUSIONS

These results suggest that the immunoreactivity of p53 may be a biologic marker of prognostic significance.

Histochemical study of pituitary adenomas with Ki-67 and anti-DNA polymerase alpha monoclonal antibodies, bromodeoxyuridine labeling, and nucleolar organizer region counts

The growth potential of 65 pituitary adenomas was determined by histochemical analysis with Ki-67 and anti-DNA polymerase alpha monoclonal antibodies, bromodeoxyuridine (BrdUdR) labeling, and counts of argyrophilic nucleolar organizer regions (Ag-NORs). The mean proliferating cell indices (PCIs) determined by Ki-67 and anti-DNA polymerase alpha and the BrdUdR labeling index (LI) were generally very low [1.0 +/- 0.2%, 1.1 +/- 0.2%, and 0.5 +/- 0.1% (+/- SE), respectively]. Apart from adrenocorticotropic hormone-positive adenomas, which had significantly higher indices, there were no statistically significant differences in the indices among the other subtypes of pituitary adenomas. Recurrent tumors had higher Ki-67 and DNA polymerase alpha PCIs and BrdUdR LIs (3.6%, 4.2%, 1.4%) than primary tumors (0.8%, 0.8%, 0.3%; P less than 0.005). The number of Ag-NORs did not correlate significantly with any of the three indices. The mean number of Ag-NORs was higher in nonfunctioning adenomas than in functioning adenomas (2.04 vs 1.66, P less than 0.005); among prolactin-positive adenomas, those treated preoperatively with bromocriptine had more Ag-NORs than untreated tumors (1.75 vs 1.57, P less than 0.005). These results suggest that the Ki-67 and DNA polymerase alpha PCIs and the BrdUdR LI predict the growth potential of individual pituitary adenomas, whereas the number of Ag-NORs appears to correlate with hormone production rather than with the proliferative potential.

An analysis of proliferating cells in biopsy specimens from patients with small hepatocellular carcinoma

The proliferation of neoplastic and nonneoplastic hepatocytes is caused by various humoral growth factors with autocrine and paracrine mechanisms, and the proliferative activity of both hepatocytes and nonhepatocytic cells contributes to neoplastic growth. The authors attempted to detect various kinds of proliferating cells immunohistochemically in small hepatocellular carcinoma (HCC) using a monoclonal antibody against DNA polymerase alpha. Most of the HCC cells that stained for this enzyme were small, had basophilic cytoplasm with poorly developed organelles, and aggregated to form clusters distributed randomly within cancer nests. Nonhepatocytic cells also were stained, including some endothelial cells, Kupffer's cells, macrophages, and lymphocytes. Fat-storing cells were not stained. The number of stained sinusoidal (capillary) cells decreased in this order: Kupffer's cells and macrophages, endothelial cells, and fat-storing cells. Nonhepatocytic cells, including lymphocytes, proliferated more actively in areas with actively growing HCC cells than in those with quiescent cancer cells. The relationship between stained HCC cells and stained sinusoidal cells was clearly defined; the correlation coefficient was 0.97. These findings suggest the possibility of a relationship between the proliferative activity of neoplastic hepatocytes and that of sinusoidal cells, including lymphocytes.

DNA polymerase alpha positive-cell rate in colorectal cancer and its relationship to prognosis

A total of 63 patients with colorectal cancer were studied for proliferative activity by an immunohistochemical technique using a monoclonal antibody against DNA polymerase alpha. The DNA polymerase alpha positive cell rates ranged from 24.0% to 74.6%. There was a correlation between the DNA polymerase alpha positive cell rates of biopsies and resected specimens. There was no significant correlation between DNA polymerase alpha positive cell rates and histological type, tumour size, invasion of bowel wall, lymphatic invasion, venous invasion, lymph node metastasis or peritoneal metastasis. Tumours with a high growth fraction (a DNA polymerase alpha positive cell rate greater than or equal to 42%) were more frequently associated with liver metastasis than those with a low growth fraction (a DNA polymerase alpha positive cell rate less than 42%). Patients with high growth fraction tumours had significantly poorer prognoses than those with low growth fraction tumours. The results of multivariate analysis using the proportional hazard model of Cox indicated that the DNA polymerase alpha positive cell rates, liver metastasis, and peritoneal metastasis were independent prognostic factors. The results indicate that the DNA polymerase alpha positive cell rate may be a useful prognostic marker of colorectal cancers.

Cell proliferation kinetics of human gastric carcinoma: an immunohistochemical study with a monoclonal antibody against DNA polymerase-alpha

Cell proliferation kinetics of human gastric carcinoma were studied immunohistochemically using a monoclonal antibody against DNA polymerase-alpha (Pol-alpha). The distribution patterns and percentages of proliferative cells were examined in cases with various histological types of gastric carcinoma and compared with those of normal epithelium of the gastric foveolae. Pol-alpha-positive epithelial cells were localised at the isthmus of the normal foveola, while Pol-alpha-positive cancer cells were distributed irregularly in the cancer nests. The percentage of Pol-alpha-positive cells (%PPC) was significantly higher in the carcinoma [mean (S.D.) 41.6 (12.9)%] than in the normal foveola [24.8 (6.4)%] (P < 0.01). Also, the intestinal-type carcinoma showed a relatively higher %PPC [44.9 (12.0)%] than the diffuse type [36.2 (15.1)%] (P<0.05), and the %PPC of signet ring cell carcinoma was extremely low [7.3 (2.2)%] (P< 0.01). Pol-alpha-positive cancer cells were observed most abundantly in the lamina propria of the mucosa. They decreased in number with the depth of cancer infiltration down to the subserosa.

Detection of proliferating liver cells in various diseases by a monoclonal antibody against DNA polymerase-alpha: with special reference to the relationship between hepatocytes and sinusoidal cells

Proliferating cells in liver specimens from patients with various diseases were detected by use of a monoclonal antibody against human DNA polymerase-alpha, which is present in the nuclei of cells in the G1, S, M and G2 phases of the mitotic cell cycle and absent in the G0 phase, to clarify the kinetics and morphological characteristics of these cells. This monoclonal antibody was supernatant derived from clone CL22-2-42B, and the peroxidase antiperoxidase method was used. Not only epithelial cells (hepatocytes, biliary epithelial cells and hepatocellular carcinoma cells) but also nonepithelial cells (Kupffer cells and other macrophages, endothelial cells, fat-storing cells, lymphocytes and fibroblasts) were stained for DNA polymerase-alpha. In acute viral hepatitis with confluent necrosis, small hepatocytes with basophilic cytoplasm next to the necrosis accounted for most of the proliferating cells. In these areas, Kupffer cells and other macrophages and lymphocytes had often proliferated. Hepatocellular carcinoma cells were frequently stained for DNA polymerase-alpha, in addition to endothelial cells, macrophages and lymphocytes. These nonepithelial cells were stained more frequently in specimens with many stained carcinoma cells than in those with only a few cells stained. In fibrotic areas, fibroblasts were often stained for this enzyme. In proliferating bile ducts, both small epithelial cells and large mature cells were stained. The differences between stained and nonstained cells that were not hepatocytes could not be defined by their ultrastructural characteristics. From these findings, it seemed possible that sinusoidal cells, especially Kupffer cells and other macrophages, might be much involved in hepatocytic proliferation during regeneration of the liver and also in the occurrence of malignant tumors.

DNA polymerase-alpha as a putative early relapse marker in non-small cell lung cancer. An immunohistochemical study

The authors examined 72 fresh frozen sections of primary lung cancer using a monoclonal antibody for DNA polymerase-alpha (POL-alpha). The percentage of POL-alpha-positive cells was 17.3%. The tumors were divided into two groups. In one group, more than 5% of the POL-alpha-positive cells were designed POL-alpha-positive, and in the other group less than 5% were POL-alpha-negative. The incidence of POL-alpha-positive in men was statistically higher than that in women (P less than 0.05). The incidence correlated with the T (tumor) status, with a significance. Based on data on 43 patients with non-small cell lung cancer and who underwent a complete resection, the 3-year disease-free survival rates of POL-alpha-positive and POL-alpha-negative cells were 42% and 81%, respectively (P less than 0.05). When the patients were restricted to the class of N0 disease or Stage I, all the patients diagnosed as a cases of a relapse of lung cancer were POL-alpha positive. The 3-year disease-free survival rate of patients with POL-alpha negative was 100%. Our data suggest that in cases of non-small cell lung cancer, POL-alpha expression is associated with the extent of malignancy and a recurrence. Thus POL-alpha may prove to be a pertinent marker of an early relapse.

Growth fraction of human bladder tumors

The growth fraction of bladder tumors was immunohistochemically assessed in situ using anti-DNA polymerase (Pol alpha) monoclonal antibody. This enzyme is known to be present in the nucleus of the cells in G1, S, and G2 phases. The percentage of labeled cells was expressed as the labeling index (LI). The average LI was 6.0% in normal epithelium and 17.8% in bladder tumors, this difference being significant. The labeled cells were distributed throughout both the basal and surface layers of bladder tumors. However, in some bladder tumors, the distribution of Pol alpha-labeled cells varied from area to area. The higher fraction of labeled cells was found in high grade or invasive tumors. Papillary and nodular bladder tumors showed a greater rate of cell proliferation than papillary tumors. These findings suggest that Pol alpha immunostaining could be a potent tool for easy and quick evaluation of proliferating cells in bladder tumors, thereby providing a supplement to conventional histological findings.

Detection of proliferating hepatocytes in patients with acute hepatic failure by mitotic figures and a monoclonal antibody against DNA polymerase alpha

Information on the ultrastructure and phenotypes of proliferative hepatocytes is scarce, so we set out to detect proliferating hepatocytes immunohistochemically by use of a monoclonal antibody against DNA polymerase alpha (DNA-PA). The findings from this method were compared with conventional features, such as mitotic figures, and hepatic regeneration after injury was considered in the light of these findings. The subjects of the basic study were 23 patients with acute hepatic failure. There were 6.8 +/- 5.5 (mean +/- SD) mitotic hepatocytes per 1,000 hepatocytic nuclei, and 209 +/- 158 hepatocytes stained for DNA-PA per 1,000 hepatocytic nuclei. By light and electron microscopy (n = 4), hepatocytes stained for DNA-PA showed various morphological features, including development of organelles, but some resembled hepatocytes in mitosis. Accordingly, this histochemical method may be useful in studies of hepatic regeneration. In acute confluent necrosis, when hepatocytic proliferation is urgently needed for survival, small hepatocytes next to necrotic areas (probably immature cells, to judge from the development of their organelles) were predominant in hepatic regeneration. These findings suggest that hepatocytes in different stages of development can easily enter the mitotic cell cycle repeatedly when rapid regeneration is needed.

Identification and fine structure of proliferating hepatocytes in malignant and nonmalignant liver diseases by use of a monoclonal antibody against DNA polymerase alpha

To analyze the process of liver regeneration and the initiation of hepatocellular carcinoma (HCC), we studied histochemically the morphologic features of proliferating parenchymal cells stained for DNA polymerase alpha (DPA), in 31 patients with various diseases, by use of a monoclonal antibody against DPA. In specimens from patients with acute viral hepatitis with confluent necrosis, most stained hepatocytes were small, with basophilic cytoplasm, and were located next to the necrotic areas. Under electron microscopy, stained granules were seen in the nucleus. Most stained hepatocytes had immature organelles. In specimens from patients with cirrhosis of the liver, the number of stained hepatocytes greatly differed in different pseudolobules. In specimens from patients with adenomatous hyperplasia, stained hepatocytes, mostly small and basophilic, were found diffusely; electron microscopy showed slightly indented nuclei with a few organelles and less condensed chromatin than normal. In specimens from patients with HCC, most stained cancer cells were small and basophilic; electron microscopy showed indented nuclei with a few organelles and less than normal condensed chromatin. Staining showed that during regeneration, immature hepatocytes reentered the cell cycle and repaired a large necrotic area. It was conceivable that in the initiation of HCC, some small hepatocytes with indented nuclei and less condensed chromatin might become HCC cells.

Detection of the growth fraction in colorectal tumours by a monoclonal antibody against DNA polymerase alpha

The cell kinetics of 54 colorectal tumours were examined by immunohistochemical methods, using the monoclonal antibody DNA polymerase alpha which reacts with an antigen found only in proliferating cells. The rate of DNA polymerase alpha positive cells in colorectal cancer was 44.8%, a figure that was significantly higher than the 21.9% found in colorectal adenomas. The rate of DNA polymerase alpha positive cells tended to rise as the degree of differentiation decreased according to the standard histological grading criteria for colorectal cancer. Positive cells were detected in much greater numbers in tumours with liver metastasis (55.4%) than in those without metastasis (41.7%). The rate of DNA polymerase alpha positive cells for aneuploid lesions was higher than that for lesions with a diploid pattern. The determination of growth fractions with a monoclonal antibody (DNA polymerase alpha) may be a biological marker of great prognostic significance.

Immunohistochemical demonstration of DNA polymerase alpha in human brain-tumor cells

The proliferative capacity of brain-tumor cells was analyzed in vitro and in situ using monoclonal antibody (MAb) against deoxyribonucleic acid (DNA) polymerase alpha. For the in vitro studies, two cultured human glioma cell lines were investigated using MAb against DNA polymerase alpha, the MAb Ki-67, a serum against proliferating cell nuclear antigen (PCNA/cyclin), bromodeoxyuridine (BUdR), and an anti-BUdR MAb. During exponential growth of the cells, the percentage of polymerase alpha-positive cells (the "polymerase alpha score") ranged from 72.0% to 77.1%, the Ki-67-positive cells (the "Ki-67 score") ranged from 43.4% to 59.4%, the PCNA/cyclin-positive cells from 30.9% to 41.4%, and the BUdR labeling index from 28.6% to 39.3%. For the in situ studies, tissue from 60 human brain tumors and from two normal human brains was investigated and the polymerase alpha scores and Ki-67 scores were compared. In normal brain tissue, no immunostaining was found by either method. In brain tumors, both the polymerase alpha scores and the Ki-67 scores correlated with the histological grade of malignancy. Polymerase alpha scores were generally higher than Ki-67 scores in the same specimen, especially in malignant brain tumors. These findings suggest that immunostaining of DNA polymerase alpha is a convenient and important new method by which to estimate the cellular proliferation rate of brain tumors. Polymerase alpha scores may be closer to the growth fraction of the individual tumor than the MAb Ki-67 or other scores.

Expression of DNA polymerase alpha and Leu3a molecules in growing and saturated cultures of human leukemic cells: phenotype analysis of proliferative cells by flow cytometry

A flow cytometric method to analyze phenotypes of proliferative cells was developed using human leukemic cell line MOLT 4. A nuclear protein, DNA polymerase alpha (pol alpha), was selected as a marker for proliferative cells, and Leu3a molecule as a cell-surface antigen phenotype marker of the cells. The procedure involved the simultaneous use of fluorescein-conjugated anti-pol alpha antibody, developed by us, and commercially available phycoerythrin-conjugated anti-Leu3a antibody. The optimal fixative for both proteins was phosphate-buffered 2% paraformaldehyde. The pol alpha-positive population in logarythmically growing MOLT 4 cells was estimated, by flow cytometry, to be ca. 95%. A sharp flow cytometry histogram with a strong pol alpha-linked fluorescence was observed. On the other hand, the pol alpha-positive population in the saturated culture was ca. 70%, with weaker pol alpha-linked fluorescence. Thus, the population of pol alpha-positive cells and the amount of pol alpha in cells was dependent on the cell density of the culture. In contrast, ca. 90% Leu3a-positive populations with similar flow cytometry histograms were seen in either growing or saturated states, suggesting that expression of Leu3a was independent of cell density. The flow cytometric method using fluorescein isothiocyanate-conjugated anti-pol alpha antibody is useful for detecting proliferative fractions of free tumor cells, such as leukemic cells. Furthermore, analysis of the phenotype of the proliferative or non-proliferative cells became easier by simultaneous labeling with antibodies against pol alpha and phenotype-specific proteins.

Proliferative cell index in endometrial adenocarcinoma of different nuclear grades

Proliferative cell indices (PCI) in 20 cases of endometrial adenocarcinoma were obtained by staining DNA polymerase alpha. The PCI ranged from 11.1 to 42.1, averaging 24.7 +/- 8.7. Four cases of stage III all exhibited fairly large PCI (30.4-32.9). In contrast, in 16 cases of stage I the values were spread over a wide range. In 13 cases with histological grade (HG) 1 of stage I, larger PCI were obtained in the nuclear grade (NG) 2 group; the mean PCI values of HG 1-NG 1 and HG 1-NG 2 were 16.5 +/- 4.6 and 25.6 +/- 5.2, respectively. Because of the good correlation between PCI and HG or NG, PCI may be useful as an additional prognostic factor in endometrial adenocarcinoma, especially in stage I cases.

Structural study of immunoaffinity-purified DNA polymerase alpha-DNA primase complex from calf thymus

The DNA polymerase alpha-DNA primase complex was purified over 17,000-fold to near homogeneity from calf thymus using an immunoaffinity column. Sodium dodecyl sulfate gel electrophoresis revealed three polypeptides with molecular weights of 140, 50 and 47 kDa, in a ratio of 1:2:0.25. The complex showed a sedimentation coefficient of 9.7 S, a Stokes radius of 56 A and a native molecular weight of 250-260 kDa. Taken together, the data suggest that the calf thymus dNA polymerase alpha-DNA primase complex is essentially a heterotrimer of large (140 kDa) and small (50 kDa) subunits in a ratio of 1:2, with a globular conformation. Electron-microscopic studies of the complex revealed a spherical particle of 120 A in diameter, in agreement with the physiochemical results. The binding of the complex to DNA was also demonstrated.

Detection of proliferative cells in dysplasia, carcinoma in situ, and invasive carcinoma of the uterine cervix by monoclonal antibody against DNA polymerase alpha

The distribution of DNA polymerase alpha-positive cells in neoplasia of the uterine cervix and in normal cervical epithelium was studied using a monoclonal antibody against DNA polymerase alpha. The positive cells were found only in the parabasal layer of normal cervical epithelium and only in the nonkeratinized areas of the cancer nests of invasive keratinizing carcinoma. Most cells in cancer nests of an invasive nonkeratinizing carcinoma were found to be DNA polymerase alpha-positive. In cases of mild or moderate dysplasia DNA polymerase alpha-positive cells were found only in the lower half of the epithelium. DNA polymerase alpha-positive cells in severe dysplasia to carcinoma in situ were distributed throughout the full thickness of the epithelium. The percentages of DNA polymerase alpha-positive cells in mild or moderate dysplasia, severe dysplasia to carcinoma in situ, and invasive carcinoma were 32.2%, 45.7%, and 53.7%, respectively. The authors previously developed immunohistochemical methods for detecting DNA polymerase alpha by monoclonal antibody that allowed the proliferative activity of cells in normal and neoplastic tissues to be estimated.

Monoclonal antibody that blocks phosphoinositide-dependent activation of mouse tumor DNA polymerase alpha

A monoclonal antibody (MaB) against mouse sarcoma DNA polymerase alpha was isolated from the culture medium of an IgG-secreting hybridoma. The MaB demonstrated reactivity against two murine DNA polymerase alpha preparations and a calf thymus DNA polymerase alpha. Murine sarcoma polymerase was activated in vitro by phosphatidylinositol-4-monophosphate (PIP) showing increased deoxynucleotidyltransferase activity and enhanced binding affinity to activated DNA template. The MaB did not neutralize polymerase activity, but blocked further activation of the enzyme by PIP. Treatment of polymerase with MaB prior to treatment with PIP inhibited both increased enzyme activation and increased binding of the enzyme to DNA template. Treatment of polymerase with MaB subsequent to treatment with PIP did not block enzyme activation or increased DNA template binding. The data suggest that this anti-DNA polymerase alpha IgG is directed against a regulatory subunit of the polymerase rather than the catalytic subunit. The antibody may serve to distinguish between DNA polymerase alpha preparations with distinctly different regulatory subunits.

Synthesis of DNA polymerase alpha analyzed by immunoprecipitation from synchronously proliferating cells

Synchronously proliferating TC7 monkey and 3T3 mouse cells were pulse labeled with [35S]methionine. Radioactively labeled DNA polymerase alpha was immunoprecipitated with polymerase-specific monoclonal antibodies. The precipitated polypeptides were identified by gel electrophoresis and fluorography. The increase in DNA polymerase alpha activity during S phase was accompanied by an increased synthesis of the enzyme. Some DNA polymerase alpha was synthesized in growth-arrested TC7 cells whereas the synthesis of the large polymerase subunit in 3T3 cells was strictly coupled to the replicative phase of the cell cycle. We also found that DNA polymerase alpha was more prone to proteolysis in TC7 cells than in 3T3 cells. In 3T3 cells, a polymerase subunit with an apparent molecular weight of 186 000 was observed; this subunit was most probably associated with two smaller subunits of Mr 74 000 and 52 000. Synthesis of these three polymerase-associated polypeptides appeared to be regulated differently.

Characterization of a Mr = 56,000 polypeptide associated with 10S DNA polymerase alpha purified from calf thymus using monoclonal antibody

Existence of a Mr = 56,000 polypeptide associated with 10S DNA polymerase alpha was shown by production of a monoclonal anti-calf thymus 10S DNA polymerase alpha antibody secreted from a hybridoma line named 3H1. The antibody bound three polypeptides with Mr = 180,000, 56,000 and 32,000 in hydroxylapatite fraction of 10S DNA polymerase alpha by immunoblot. The antibody co-precipitated the polypeptides with the large polypeptide (Mr = 150,000-140,000) of 10S DNA polymerase alpha with the aid of second antibody. Among three polypeptides, the Mr = 56,000 polypeptide was co-purified with DNA polymerase alpha through DNA-cellulose chromatography and repeated sucrose rate-zonal centrifugations. The Mr = 56,000 polypeptide was still associated with 10S DNA polymerase alpha after second sucrose rate-zonal centrifugation, but the amount of it was reduced. The polypeptide was banded at pH 7.2-8.0 and displayed microheterogeneity in respect of isoelectric point by isoelectrofocusing with 7 M urea, and showed weak DNA-binding property after blotting onto a nitrocellulose. The antibody against the polypeptide precipitated DNA polymerase alpha from human, rat, and mouse, and Mr = 56,000 and 32,000 polypeptides were detected in these DNA polymerase alpha fractions by immunoblot. These results suggest that the polypeptide with Mr = 56,000 may take part in the DNA polymerase reaction.

Properties and applications of new monoclonal antibodies raised against calf DNA polymerase alpha

A panel of 12 hybridoma cell lines secreting monoclonal antibodies against alpha-polymerase were prepared by fusion of mouse myeloma cells and spleen cells of a rat immunized with homogeneous calf thymus alpha-polymerase. Hybridomas were selected and cloned on the basis of immunobinding to pure alpha-polymerase in solid phase radioimmunoassay. Antibodies secreted by these cells eventually were purified in milligram quantities from ascites fluids. These antibodies, all of the rat immunoglobulin M class, cross-reacted with alpha-polymerases from calf and monkey cells as revealed by immunobinding in radioimmunoassay and by immunoprecipitation of DNA polymerase activity. The antibodies were not capable of neutralizing the enzyme activity. With the methods described these antibodies may be used to immunoprecipitate alpha-polymerase from crude extracts of mammalian cells and to measure levels of the enzyme protein.

Monoclonal antibodies in enzyme research: present and potential applications

Hybridoma antibodies are powerful tools. Their impact is already apparent in many areas of basic and applied research. In contrast, their impact is just beginning to be felt in enzymology. The existing literature on monoclonal antibodies to enzymes and isozymes, reviewed in this article, is as yet largely descriptive. However, the potential applications discussed herein promise to revolutionize existing strategies of unraveling the basic biochemistry, immunochemistry, and developmental, somatic cell, and molecular genetics of enzymes and isozymes. At a clinical level, monoclonal antibodies to enzymes promise to radically improve the current modalities of diagnosis and therapy in clinical enzymology and oncology. It is becoming increasingly apparent that the future applications of hybridoma antibodies to enzymes and isozymes appear to be limited only by our imagination.

Identification of a higher molecular weight DNA polymerase alpha catalytic polypeptide in monkey cells by monoclonal antibody

A monoclonal antibody against purified calf DNA polymerase alpha (deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase, EC 2.7.7.7) was used to immunoprecipitate proteins from a crude soluble extract of growing monkey BSC-1 cells. Immunoprecipitates contained familiar DNA polymerase alpha catalytic polypeptides of Mrs approximately equal to 115,000 and 70,000 and also a Mr 40,000 catalytic polypeptide; the major component in the immunoprecipitates, however, was a polypeptide of Mr approximately equal to 190,000 not previously identified as a DNA polymerase. This protein was capable of DNA polymerase activity after electroelution from NaDodSO4/polyacrylamide gels and renaturation. The highly purified enzyme so obtained was active with poly(dT).oligo(rA) as template.primer, resistant to dideoxy TTP (ddTTP), and inhibited by aphidicolin and butylphenyldeoxyguanosine 5'-triphosphate, thus identifying it as a DNA polymerase alpha. The results indicate that a polypeptide of Mr approximately equal to 190,000 is an abundant component among DNA polymerase alpha catalytic polypeptides in growing monkey cells.

Large polypeptides of 10S DNA polymerase alpha from calf thymus: rapid isolation using monoclonal antibody and tryptic peptide mapping analysis

The polypeptides recognized by a monoclonal antibody against calf thymus DNA polymerase alpha (secreted from a hybridoma CL22 -2- 42B , Nucleic Acids Res. (1982) 10, 4703-4713) were identified by the immunoblot method as the large polypeptides of the partially-purified 10S DNA polymerase alpha fraction. Using an immunoprecipitation technique with the monoclonal antibody, a rapid immunological isolation of the polypeptides has been achieved. By this method, the large polypeptides with Mr = 140,000, 145,000, and 150,000 were isolated from a partially-purified preparation of 10S DNA polymerase alpha. On the other hand, the polypeptides with Mr = 150,000, 180,000, and 240,000 were obtained from a crude extract of calf thymus. Tryptic peptide maps showed that the large polypeptides with Mr = 150,000, and 180,000 were very similar in primary structure and that the structures of Mr = 180,000 and 240,000 polypeptides contained partially common sequences. Among these polypeptides, the Mr = 150,000 polypeptide was shown to correlate with the enzyme activity. These results suggest that the large polypeptide of 10S DNA polymerase alpha is initially synthesized as Mr = 180,000 or larger polypeptide, then converted to the form with Mr = 150,000. The Mr = 140,000 and 145,000 polypeptides in the purified preparation may be artificial products formed during purification.

Intracellular localization and metabolism of DNA polymerase alpha in human cells visualized with monoclonal antibody

Indirect immunofluorescence microscopy with monoclonal antibody against DNA polymerase alpha revealed the intranuclear localization of DNA polymerase alpha in G1, S, and G2 phases of transformed human cells, and dispersed cytoplasmic distribution during mitosis. In the quiescent, G0 phase of normal human skin fibroblasts or lymphocytes, the alpha-enzyme was barely detectable by either immunofluorescence or enzyme activity. By exposing cells to proliferation stimuli, however, DNA polymerase alpha appeared in the nuclei just prior to onset of DNA synthesis, increased rapidly during S phase, reached the maximum level at late S and G2 phases, and was then redistributed to the daughter cells through mitosis. It was also found that the increase in the amount of DNA polymerase alpha by proliferation stimuli was not affected by inhibition of DNA synthesis with aphidicolin or hydroxyurea.

DNA primase associated with 10 S DNA polymerase alpha from calf thymus

Among multiple subspecies of DNA polymerase alpha of calf thymus, only 10 S DNA polymerase alpha had a capacity to initiate DNA synthesis on an unprimed single-stranded, circular M13 phage DNA in the presence of ribonucleoside triphosphates (DNA primase activity). The primase was copurified with 10 S DNA polymerase alpha through the purification and both activities cosedimented at 10 S through gradients of either sucrose or glycerol. Furthermore, these two activities were immunoprecipitated at a similar efficiency by a monoclonal antibody directed against calf thymus DNA polymerase alpha. These results indicate that the primase is tightly bound to 10 S DNA polymerase alpha. The RNA polymerizing activity was resistant to alpha-amanitin, required high concentration of all four ribonucleoside triphosphates (800 microM) for its maximal activity, and produced the limited length of oligonucleotides (around 10 nucleotides long) which were necessary to serve as a primer for DNA synthesis. Covalent bonding to RNA to DNA was strongly suggested by the nearest neighbour frequency analysis and the DNAase treatment. The DNA synthesis primed by the RNA oligomers may be carried out by the associating DNA polymerase alpha because it was strongly inhibited by araCTP, resistant to d2TTP, and was also inhibited by aphidicolin but at relatively high concentration. The primase preferred single-stranded DNA as a template, but it also showed an activity on the double-stranded DNA from calf thymus at an efficiency of approx. 10% of that with single-stranded DNA.