Ribavirin dose reduction raises relapse rate dose-dependently in genotype 1 patients with hepatitis C responding to pegylated interferon alpha-2b plus ribavirin.

The impact of ribavirin exposure on virologic relapse remains controversial in combination therapy with pegylated interferon (Peg-IFN) and ribavirin for patients with chronic hepatitis C (CH-C) genotype 1. The present study was conducted to investigate this. Nine hundred and eighty-four patients with CH-C genotype 1 were enrolled. The drug exposure of each medication was calculated by averaging the dose actually taken. For the 472 patients who were HCV RNA negative at week 24 and week 48, multivariate logistic regression analysis showed that the degree of fibrosis (P = 0.002), the timing of HCV RNA negativiation (P < 0.001) and the mean doses of ribavirin (P < 0.001) were significantly associated with relapse, but those of Peg-IFN were not. Stepwise reduction of the ribavirin dose was associated with a stepwise increase in relapse rate from 11% to 60%. For patients with complete early virologic response (c-EVR) defined as HCV RNA negativity at week 12, only 4% relapse was found in patients given > or = 12 mg/kg/day of ribavirin and ribavirin exposure affected the relapse even after treatment week 12, while Peg-IFN could be reduced to 0.6 microg/kg/week after week 12 without the increase of relapse rate. Ribavirin showed dose-dependent correlation with the relapse. Maintaining as high a ribavirin dose as possible (> or = 12 mg/kg/day) during the full treatment period can lead to suppression of the relapse in HCV genotype 1 patients responding to Peg-IFN alpha-2b plus ribavirin, especially in c-EVR patients.

Pegylated interferon alpha-2b (Peg-IFN alpha-2b) affects early virologic response dose-dependently in patients with chronic hepatitis C genotype 1 during treatment with Peg-IFN alpha-2b plus ribavirin.

Chronic hepatitis C (CH-C) genotype 1 patients who achieved early virologic response have a high probability of sustained virologic response (SVR) following pegylated interferon (Peg-IFN) plus ribavirin therapy. This study was conducted to evaluate how reducing drug doses affects complete early virologic response (c-EVR) defined as hepatitis C virus (HCV) RNA negativity at week 12. Nine hundred eighty-four patients with CH-C genotype 1 were enrolled. Drug doses were evaluated independently on a body weight base from doses actually taken. From multivariate analysis, the mean dose of Peg-IFN alpha-2b during the first 12 weeks was the independent factor for c-EVR (P = 0.02), not ribavirin. The c-EVR rate was 55% in patients receiving > or = 1.2 microg/kg/week of Peg-IFN, and declined to 38% at 0.9-1.2 microg/kg/week, and 22% in patients given <0.9 microg/kg/week (P < 0.0001). Even with stratified analysis according to ribavirin dose, the dose-dependent effect of Peg-IFN on c-EVR was observed, and similar c-EVR rates were obtained if the dose categories of Peg-IFN were the same. Furthermore, the mean dose of Peg-IFN during the first 12 weeks affected HCV RNA negativity at week 24 (P < 0.0001) and SVR (P < 0.0001) in a dose-dependent manner. Our results suggest that Peg-IFN was dose-dependently correlated with c-EVR, independently of ribavirin dose. Thus, maintaining the Peg-IFN dose as high as possible during the first 12 weeks can yield HCV RNA negativity and higher c-EVR rates, leading to better SVR rates in patients with CH-C genotype 1.

Unusually high mitochondrial alpha glycerophosphate dehydrogenase activity in rat brown adipose tissue.

Brown adipose tissue of the rat has been found to have an unusually high activity of mitohondrial alpha-glycerophosphate dehydrogenase (alpha-GPD) when assayed both by a histochemical staining procedure and by a quantitative biochemical method with isolated mitochondria. In contrast to succinic, glutamic, and beta-hydroxybutyrate dehydrogenases, all mitochondrial enzymes, the activity of alpha-GPD in brown fat was 10 times that in liver, more than 20 times that in white adipose tissue, and 9 times that in kidney. The soluble NAD-linked alpha-GPD was also higher in brown adipose tissue than in white adipose tissue, liver, or kidney, but the differences were much less marked. The possible importance of the high activity of mitochondrial alpha-GPD in the regulation of synthesis of esterified lipid and in thermogenesis in brown fat is discussed.

Therapeutic effect of treatment with polyclonal or monoclonal antibodies to alpha-fetoprotein that have been conjugated to daunomycin via a dextran bridge: studies with an alpha-fetoprotein-producing rat hepatoma tumor model.

Purified monoclonal mouse or polyclonal horse antibodies (Ab) to rat alpha-fetoprotein (AFP) were conjugated with daunomycin via a dextran bridge. The therapeutic effect of these Ab-daunomycin conjugates on an AFP-producing rat hepatoma which was inoculated s.c. in Donryu rats was studied. Tumors (s.c.) and distant metastases were present by 14 days after tumor inoculation and the serum AFP level was 35 micrograms/ml. The injection of the Ab-daunomycin conjugate, started on day 14, significantly prolonged host survival with inoculated controls having a median survival of 25 days compared to 57 and 60 days for the treated groups. In a second study the Ab-daunomycin conjugates were injected i.v. every other day for five times after the surgical resection of the s.c. tumor. There was a slight therapeutic effect with either antibody or daunomycin alone but treatment with the AFP Ab-daunomycin conjugates significantly prolonged survival and 60% of these treated animals were "tumor free" when sacrificed on day 100. Serial quantitation of the concentration of AFP in the serum of the treated tumor-bearing or in the tumor-resected rats correlated with the therapeutic effectiveness of the Ab-daunomycin conjugates. These experiments show that the optimal treatment with specific antibody-drug conjugates will be in hosts where there is a small residual tumor burden such as may exist following resection of a primary tumor mass. They further show that the serial quantitation of serum AFP can be utilized to determine if residual tumor is present following treatment with Ab-daunomycin conjugates.

Bovine serum albumin-doxorubicin conjugate overcomes multidrug resistance in a rat hepatoma.

A bovine serum albumin-conjugated doxorubicin via the glutaraldehyde bridge (BSA-DXR conjugate) showed potent dose-dependent inhibition of cell growth against daunorubicin-resistant AH66 (AH66DR) cells as well as parental AH66 (AH66P) cells in vitro as compared to treatment with DXR or BSA-glutaraldehyde conjugate without DXR (BSA-GA). In the culture of AH66DR with BSA-DXR conjugate, drug accumulation in the AH66DR cells increased as a function of time up to 24 h reaching approximately the same drug level as AH66P cells treated with DXR. The intracellular accumulation of the BSA-DXR conjugate was inhibited by the addition of ammonium chloride, while that of DXR alone was not inhibited. Intracellular DXR was effluxed rapidly from AH66DR cells, but BSA-DXR conjugate or pharmacologically active DXR adduct remained in the cells at a relatively high concentration over a 36-h time period. The life-prolonging effect of the conjugate was assessed using rats inoculated i.p. with AH66P or AH66DR. The rats were treated with the BSA-DXR conjugate, DXR, a mixture of DXR with BSA, or BSA-GA by either the i.p. or i.v. route. Treatment with DXR had no significant surviving effect as compared to that with saline in AH66P-bearing rats. By contrast, BSA-DXR conjugate showed a significant life-prolonging effect as compared with DXR alone in the same degree both in AH66P- and AH66DR-bearing rats. BSA-GA did not show any toxicity in vivo as well as in vitro. These results indicate that the BSA-DXR conjugate allows DXR to escape from the multidrug resistance mechanism.

Expression of vascular permeability factor/vascular endothelial growth factor in human hepatocellular carcinoma.

Vascular permeability factor (VPF)/vascular endothelial growth factor (VEGF) is unique in its ability to promote vascular permeability and endothelial cell growth, and its role in tumor development has received considerable attention. In this report, we describe the elevation of VPF/VEGF transcript expression in human hepatocellular carcinoma. Surgical samples of 23 patients with hepatocellular carcinoma were studied using reverse transcription-PCR analysis. The oligonucleotide primers were designed to amplify all four known splicing variants that could be expressed in the samples studied. Sixteen cases showed VPF/VEGF transcript expression in the tumor (16/23, 69.6%), whereas only 9 of the 23 patients showed it in the corresponding nontumoral part. There was no difference between the pattern of expression of VPF/VEGF isoforms in tumoral and nontumoral tissues. VPF/VEGF mRNA expression in the liver tumors was associated with fibrous capsule formation and septal formation (P < 0.05 respectively, Fisher's exact P test). In situ hybridization confirmed the presence of VPF/VEGF mRNA expression in tumor cells and less intensely in hepatocytes of nontumoral liver. We also found that VPF/VEGF expression in the tumor cell was increased in the area adjacent to necrotic regions (presumably hypoxic regions). As a regulator of vascular permeability and endothelial cell growth factor, VPF/VEGF may play an important role in the development of hepatocellular carcinoma.

Ability of ubiquitin radioimmunoassay to discriminate between monoubiquitin and multi-ubiquitin chains.

Free ubiquitin (mainly monoubiquitin) and multi-ubiquitin chains coexist in eukaryote cells and serve distinct cellular roles. However, any immunoassay systems established previously have not been proved to be applicable for measuring the former without cross-reactive responses with the latter. For this purpose, we developed a radioimmunoassay specific to monoubiquitin by employing antiserum US-1 against ubiquitin. In this assay, ubiquitin-protein conjugates, prepared by a reticulocyte lysate fraction II and fractionated on Moro Q and Superdex 200 columns, exhibited practically no cross-reactivity. The cross-reactivity of fractionated ubiquitin-lysozyme conjugates was also analyzed as a function of their multi-ubiquitin chain size. As a result, the larger the conjugates were found to be, the weaker were the cross-reactive responses they showed, and the multi-ubiquitin chains (n > approx. 20) were substantially unreactive in the radioimmunoassay. By using the radioimmunoassay, heat-shock-induced decrease in the level of cellular free (mono)ubiquitin was detected. In addition, the standard preparation of multi-ubiquitin chains was not cross-reactive in all other five radioimmunoassays employing distinct antibodies to ubiquitin (four antisera and a monoclonal antibody). These data suggest that radioimmunoassays employing ubiquitin antibodies raised by the general methods can discriminate between monoubiquitin and multi-ubiquitin chains and quantitate cellular free ubiquitin.

Clear cell carcinoma of the human ovary synthesizes and secretes a transferrin with microheterogeneity of lectin affinity.

Human ovarian clear cell carcinoma cell line (transferrin (Tf)-non-producer), HAC 2, cells were adapted to grow in chemically defined synthetic medium when the cells were cultured with medium containing 10 micrograms/ml of insulin at least for 6 months. They synthesized and secreted constantly the 80 kDa protein immunologically similar to human serum Tf (15 +/- 12 ng/ml/10(7) cells/3 days). By sensitive lectin-affinity electrophoresis followed by antibody-affinity blotting technique, a concanavalin A weakly bound or unbound, lentil lectin, a strongly reactive abnormal band, which was rarely found in human serum Tf, was detectable in the Tf synthesized by HAC 2 cells (HACTf). These findings suggest that the HACTf may act as one of the autocrine growth factors and that this heterogeneity of HACTf for lectin affinity is ascribed to differences in the carbohydrate moiety of the Tf.

Expression of insulin receptor substrate-1 in hepatocytes: an investigation using monoclonal antibodies.

To investigate the expression and subcellular distribution of insulin receptor substrate-1 in hepatocytes, which are major targets of insulin along with muscle and adipose tissue, we obtained monoclonal antibodies by immunizing mice with a fusion protein consisting of the C-terminal portion of the human insulin receptor substrate-1 and glutathione-S-transferase. Two of the monoclonal antibodies (designated as 7B3 and 6G5) were found to be useful for immunohistochemical studies. Using 6G5 we demonstrate a high level of expression of insulin receptor substrate-1 in liver cirrhosis hepatocytes and variable expression in hepatocellular carcinoma cells. These results suggest that insulin receptor substrate-1 may play a role in liver regeneration during cirrhosis and that an insulin signaling cascade may be involved in hepatocarcinogenesis.

Monoclonal-antibodies 5g8 and 2h6 are complementary immunohistochemical markers of lung carcinomas.

Two murine monoclonal antibodies (MAbs) 5G8 and 2H6 were generated by fusing spleen cells obtained from mice immunized with human fetal tissue extract (14 weeks, Nonidet P-40 membrane fraction) from the early first trimester, followed by a booster injection of a lung cancer cell line. The MAb 5G8 recognized antigens with a molecular weight of 90, 50, 20 kDa, was neuraminidase-resistant and showed cross-reactivity with both carcinoembryonic antigen and non-specific cross-reacting antigen. The MAb 2H6 reacted with a sialomucin whose molecular weight was more than 1000 kDa and was different from previously known tumor associated-marker antigens. The distribution of the MAb-recognizing antigens in various tissues was investigated immunohistochemically. In malignant epithelial tumors of the lung, acinar adenocarcinoma and bronchioloalveolar carcinoma were positive for both MAbs; papillary adenocarcinoma, squamous cell carcinoma, and adenoid cystic carcinoma were positive only for MAb 5G8; solid carcinoma with mucin formation, small cell carcinoma, and large cell carcinoma were positive only for MAb 2H6. The combination of the two MAbs covered almost all histological types of lung carcinomas (23 of 24 cases) except carcinoid tumors. MAbs 5G8 and 2H6 reacted also with a restricted number of adenocarcinomas of the other organs. MAb 5G8 did not react with normal fetal or adult tissues, except for metaplastic gastric mucosa, acinar cells of the breast and leucocytes, whereas MAb 2H6 reacted with the surface epithelium of the stomach and colon, the Brunner gland of the duodenum and uterine cervix as well as the epithelium of the fetal digestive tract. Thus, MAb 2H6 which recognized oncofetal sialomucin, played a complementary role to MAb 5G8 as a CEA-related MAb in the immunohistochemical diagnosis of lung carcinomas.

A monoclonal antibody CF703 raised against human fetal lung recognizes a novel onco-fetal mucin.

To obtain murine monoclonal antibodies (MAb), mice were immunized with the extract of a human fetal lung from the first trimester of gestation as initial immunogen followed by booster immunization with a human lung cancer cell line. MAb CF703 which reacted to the booster material was screened and selected. In adults, expression of the antigen defined by MAb CF703, CF703 antigen, was shown immunohistochemically in 78% of gastric carcinomas (14/18), 59% of ovarian adenocarcinomas (10/17), 50% of pancreatic carcinomas (5/10), 17% of lung carcinomas (4/24), 50% of uterine cervical adenocarcinomas (2/4), 20% of endometrial adenocarcinomas (1/5) and 10% of renal cell carcinomas (1/10). Other malignant tumors failed to demonstrate the reactivity. MAb CF703 was weakly reactive with only three adult normal tissues including surface lining of gastric mucosa, Brunner's glandular epithelia of the duodenum and columnar epithelia in the uterine endocervix. In fetal tissues, 5 of 23 tissues including squamous epithelia in lower portion of the;esophagus, surface epithelia of gastric mucosae and goblet cells in the small and large intestine were reactive. The CF703 antigen had a molecular weight over 500 kDa and its epitope was carbohydrate in nature by reason of the resistance to proteinase digestion and sensitivity to periodate oxidation, neuraminidase and alkaline-borohydrite. MAb CF703 recognizes probably a unique epitope in oncodevelopmental mucin glycoprotein. Additionally, this immunization method has the advantage of rapid acquirement of MAbs with restricted, narrow cancer spectrum and is a worthy strategy for generating the new MAbs.

Monoclonal-antibody against Doxorubicin (dxr) - some characteristics and utilization for dxr-immunoassay.

To establish a rapid, specific, sensitive and simple assay method for doxorubicin (DXR) in body fluid, monoclonal antibodies (MAbs) against DXR were generated by immunizing mice with keyhole limpet hemocyanin-DXR conjugate, cell fusion, and a one step, time saving screening ELISA method using aminoplate-coupled DXR via a glutaraldehyde bridge as solid phase antigen. Inhibition ELISA for DXR-immunoassay was established using anti-DXR MAb of the best producer (2E9) and aminoplate-coupled DXR as antigen and DXR ranging from 50 pg to 50 ng in the body fluid or in the cell extract could be detected. MAb 2E9 cross-reacted to various degrees to anthracycline compounds, such as some DXR analogues and derivatives, but did not recognize anthracene and anthraquinone structures.

Mechanism-related circumvention of Cisplatin resistance in human ovarian-carcinoma cells by (-)-(R)-2-aminomethylpyrrolidine(1,1-cyclobutanediacarboxylato)-platinum (ii) monohydrate and modulation of its sensitivity by 12-o-tetradecanoylphorbol-13-acetate.

DWA2114R, (-)-(R)-2-aminomethylpyrrolidine (1,1-cyclobutanedicarboxylato)-platinum( monohydrate, circumvented resistance in cisplatin (DDP)-resistant 2008/C13*5.25 cells to produce some collateral sensitivity. Intracellular platinum levels were not significantly different between parent 2008 and 2008/C13*5.25 cells after exposure to DWA2114R. At equimolar doses, platinum levels were 3.7 +/- 0.4 (SD)-fold (N=4; P<0.01) higher after exposure to DWA2114R than to DDP in 2008/C13*5.25 cells. This suggests that DWA2114R collateral sensitivity was due to its circumvention of impaired platinum accumulation in 2008/C13*5.25 cells, In contrast to our findings that 12-O-tetradecanoylphorbol- 13-acetate (TPA) induced cellular sensitivity to DDP and carboplatin in those cells, TPA did not alter the DWA2114R sensitivity in 2008 cells. Furthermore, it did reduce the DWA211R-resistance of 2008/C13*5.25 cells by a factor of 1.7 +/- 0.2 (SD)-fold (N=4; P<0.05) rather than increase sensitivity. This suggests that TPA sensitization effect was not common to any platinum compounds but was strongly related to their ligands.

Doxorubicin enhances transient expression of p-glycoprotein and modulates activity and isoform expression of protein-kinase-C in ah66 rat hepatoma-cells.

Intracellular changes in enzyme activity and the isoform pattern of protein kinase C (PKC) during treatment with doxorubicin (DXR) were examined in a rat ascites hepatoma AH66 parental cell line (AH66P), which shows slight expression of P-glycoprotein (Pgp) on the cell membrane and is classified as an intrinsic multidrug-resistant cell. AH66P cells, treated for 10 days with DXR at the concentrations of 0.3 or 5.0 muM, exhibited moderate to severe inhibition of PKC activity after transient increase of the activity, which mainly was either Ca2+-independent and phospholipid-dependent or Ca2+-independent and phospholipid-independent. PKC isoform analysis of the treated cells also indicated the transient 1.5- and 1.8-fold increase of PKC-delta and PKC-zeta as well as slight increase of PKC-alpha in treatment with 0.3 muM DXR and 1.9- and 1.6-fold increase of PKC-alpha and PKC-zeta with slight increase of PKC-delta in treatment with 5.0 muM, respectively. A small, but interesting discrepancy between the markedly elevated enzyme activity, which was composed particularly of both cofactor-independent forms, and the relatively low levels of isoform expression, was found when the cells were treated with 5.0 muM DXR. It is of great interest that DXR-treatment, while only slight increasing P-glycoprotein (Pgp) phosphorylation, enhanced the transient expression of Pgp on the cell membrane with good correlation with the fluctuating change in PKC activity. These results indicate that the possible expression of some or novel specific isoform(s) of PKC may modulate and be associated with expression of the Pgp.

Calpain inhibitor causes accumulation of ubiquitinated P-glycoprotein at the cell surface: possible role of calpain in P-glycoprotein turnover.

P-glycoprotein (Pgp) is a plasma-membrane glycoprotein that confers multi-drug resistance (MDR) on cells and displays ATP-driven drug pumping. The possible contribution of calpain-mediated proteolytic pathways to the functional regulation of the Pgp molecule was evaluated using K562/DXR, MDR cells. N-Acetyl-L-leucyl-L-leucyl-norleucinal was effluxed by Pgp, but N-benzyloxycarbonyl-L-leucyl-L-leucinal (zLLal), an inhibitor of calpain, retarded the degradation of Pgp leading to accumulation of the molecule largely at the cell surface membrane. Treatment with brefeldin A did not obstruct the zLLal-induced Pgp accumulation. NH4Cl increased the cytoplasmic Pgp level, with a slight to significant decrease at the cell surface membrane. Ubiquitin-ELISA and western blot analysis confirmed that the Pgp molecule, which accumulated mainly at the cell surface, was ubiquitinated. However, lactacystin did not show any accumulation of Pgp in either the cytoplasm or the cell surface membrane, suggesting that the proteasome did not participate in the phenomenon. Additionally, the Pgp was limitedly proteolyzed by calpain into two 98 kDa and 69 kDa, fragments within one minute. Despite the increased accumulation of Pgp at the cell surface after treatment with calpain inhibitor, the cytoplasmic doxorubicin level of the cells treated with a calpain inhibitor was higher than that of non-treated cells and approached that of parental cells. These results indicated that calpain involved Pgp turnover and that calpain inhibition induced ubiquitinated Pgp-accumulation mainly at the cell surface membrane with a reduction in its own functions suggesting that the modulation of Pgp-turnover involves MDR-reversal by another approach.

Biodegradation of ornithine-containing polylysine hydrogels.

The degradation of the cross-linked cationic poly(amino acid)-glutaraldehyde (GA) hydrogels by two kinds of proteolytic enzymes, trypsin and Aspergillus Protease Type XXIII, and by seven species of soil filamentous fungi has been investigated using homo- and copolypeptides of lysine (Lys) and ornithine (Orn). Trypsin degraded the hydrogels prepared from poly(Lys) and copoly(Lys Orn)s but not poly(Orn), while Aspergillus protease degraded all of them. Degradation time of hydrogels by the two proteases became longer with increasing Orn content in the gel. Seven species of soil filamentous fungi were cultured with hydrogels on Czapeck medium to evaluate the degree of microbial degradation of the hydrogels, and the three species of the fungi, Aspergillus oryzae, Penicillium citrinum and Curvularia sp., were grown in culture with an accompanying degradation of the gel matrix, while the other four species, Mucor sp., Rhizopus sp., Cladosporium sp., and Trichoderma sp., were not. The degree of degradation of gel matrix with growth of the three fungi became lower with increasing Orn content in the gel matrix. The results might offer some clues to the applications for the controlled biodegradation of cationic poly(amino acid) hydrogel by introduction of Orn, suggesting that unnatural amino acid resists hydrolysis by proteases or microorganisms.

UV-irradiation-induced DNA immobilization and functional utilization of DNA on nonwoven cellulose fabric.

Immobilization of double-stranded DNA onto nonwoven cellulose fabric by UV irradiation and utilization of DNA-immobilized cloth were examined. The immobilized DNA was found to be stable in water, with the maximum amount of fabric-immobilized DNA being approximately 20 mg/g of nonwoven fabric. The DNA-immobilized cloth could effectively accumulate endocrine disruptors and harmful DNA intercalating pollutants, such as dibenzo-p-dioxin, dibenzofuran, biphenyl, benzo[a]pyrene and ethidium bromide. Additionally, DNA-immobilized cloth was found to bind metal ions, such as Ag+, Cu2+, and Zn2+. The maximum amounts of bound Ag+, Cu2+, and Zn2+ onto DNA-immobilized cloth (1 g) were approximately 5, 2, and 1 mg, respectively. DNA-immobilized cloth containing Ag+ showed antibacterial activity against Escherichia coli and Staphylococcus aureus. DNA-immobilized cloth without metal ion and with Cu2+ or Zn2+ did not show antibacterial activity. These results suggest that immobilized DNA imparts useful functionality to cloth. DNA-immobilized cloth prepared by UV irradiation has potential to serve as a useful biomaterial for medical, engineering, and environmental application.

Monoclonal antibody, Mab 12C3, is a sensitive immunohistochemical marker of early malignant change in epithelial ovarian tumors.

A murine monoclonal antibody (MAb 12C3) that is specific to human ovarian carcinomas was generated by immunizing mice with a human ovarian germinoma cell line (JOHYC-2). The antigen distribution that was defined by MAb 12C3 in normal and malignant human tissues was analyzed by immunohistochemistry on paraffin-embedded and frozen sections. The antibody reacted with 67.7% (21 of 31 cases) of epithelial ovarian carcinomas (6 of 12 cases of serous cystadenocarcinoma, 5 of 7 cases of mucinous cystadenocarcinoma, 7 of 9 cases of clear cell carcinoma, 3 of 3 cases of endometrioid adenocarcinoma), but did not react with any of the benign epithelial ovarian adenomas tested. Partial regions of borderline ovarian malignancies that exhibited marked papillary projection of the lining cells with cellular atypia reacted positively with MAb 12C3 in 14 of 25 cases (56.0%). The histologic features of regional early malignant change corresponded to the expression of the MAb 12C3 epitope in the borderline malignant tumor cells. There was a low frequency of reaction (4.3%) between the antibody and other gynecologic and nongynecologic malignancies (46 cases of 12 tissues). In normal tissues, the antibody reacted positively with only three tissues, including corpora lutein cells, excretory ducts in the submandibular gland, and basal cells of the sebaceous glands. The antigen epitope defined by MAb 12C3 was present on a glycoprotein with a molecular mass of 200 kDa and did not exhibit any cross-reactivity with other well-known tumor markers. These data suggest that MAb 12C3 may be a useful tool for the immunohistologic detection of early malignant changes in epithelial ovarian tumors. In addition, MAb 12C3 also may facilitate a differential diagnosis between benign and borderline malignancies.