OVX1 as a marker for early stage endometrial carcinoma

BACKGROUND

Endometrial carcinoma is generally diagnosed only after the onset of postmenopausal bleeding. Although most patients with Stage I disease can be cured, the prognosis worsens significantly when the tumor is no longer confined to the uterine corpus. Serum CA 125 is elevated in only 10-20% cases of Stage I and II endometrial carcinoma. A serum tumor marker that can detect early stage endometrial cancer might aid in management of the disease.

METHODS

An OVX1 double-determinant radioimmunoassay was used to detect an epitope on a high-molecular-weight mucinlike glycoprotein found in the sera of 45 patients with endometrial cancer.

RESULTS

Apparently healthy persons had serum OVX1 antigen levels of 2.23 plus or minus 2.48 U/ml (mean +/- standard deviation). Elevated levels of OVX1 antigen (> 7.2 U/ml) were found in 5% of 184 healthy persons and in 64% of 45 patients with endometrial cancer. OVX1 antigen was elevated in 64% of 36 patients with Stage I, 50% of 2 patients with Stage II, 60% of 5 patients with Stage III, and each of 2 patients with Stage IV endometrial cancer, but only 8.6% of 58 patients with endometriosis. Elevation of serum OVX1 was found more frequently in patients with deep myometrial invasion and with poorly differentiated tumors (P < 0.01).

CONCLUSIONS

The OVX1 antigen deserves further evaluation as a marker for early detection of endometrial cancers and as a prognostic factor for women with apparent early stage disease.

Vasoconstriction induced by inhalation of irritant vapour is associated with appearance of Fos protein in C1 catecholamine neurons in rabbit medulla oblongata

The medulla oblongata was examined with Fos and tyrosine hydroxylase (TH) immunohistochemistry after 2 h of intermittent nasopharyngeal stimulation with formaldehyde vapour in the conscious rabbit. The stimulation caused apnoea, bradycardia and a rise in blood pressure known to be associated with vigorous vasoconstriction. Fos-positive neurons occurred in the spinal trigeminal nucleus, the nucleus tractus solitarius, the raphe nuclei and the ventrolateral medulla. In the rostral ventrolateral medulla, 68% of the Fos-positive neurons were TH-positive C1 cells. Our data indicate that nasopharyngeally-evoked peripheral vasoconstriction is associated with activation of C1 neurons.

Elevation of multiple serum markers in patients with stage I ovarian cancer

BACKGROUND

The high overall mortality from ovarian cancer (> 60%) relates, in part, to delays in diagnosis. When ovarian cancer is detected in stage I (International Federation of Gynecology and Obstetrics staging), up to 90% of patients can be cured. Transvaginal sonography can detect early-stage disease with great sensitivity, but it is expensive and lacks specificity. Although serum marker assays could provide a less expensive and more convenient initial screening test, the sensitivity of assays varies. Measurement of serum CA 125 in conjunction with ultrasound screening as a second-line test confers high specificity but detects only about one half of early stage ovarian carcinomas.

PURPOSE

The purpose of this retrospective study was to determine whether assays of multiple serum markers would improve sensitivity by detecting a higher percentage of stage I ovarian cancers than the CA 125 assay alone.

METHODS

Using immunoradiometric assays, we measured preoperative serum levels of CA 125 tumor-associated antigen, macrophage colony-stimulating factor (M-CSF), and OVX1 in 46 patients with stage I ovarian cancer of different histologies and 237 patients with benign pelvic masses. We also assayed sera from 204 apparently healthy women who had participated in a screening trial and remained free from cancer at 1 year of followup. All specimens were obtained from cryopreserved aliquots. Marker levels were considered to be elevated when levels of CA 125 were greater than 30 U/mL, M-CSF levels were greater than 3.1 ng/mL, or OVX1 levels were greater than 12.1 U/mL.

RESULTS

At least one of the serum markers was elevated in 98% of patients with stage I ovarian cancer; CA 125 levels were elevated in 67%. By the same criteria, 11% of healthy individuals and 51% of patients with benign pelvic masses had at least one elevated marker value. Thus, the sensitivity of the combination of assays for the three serum markers was significantly greater than the sensitivity of the CA 125 assay (P < .0005) and specificity was moderate.

CONCLUSION

A panel of these three tumor markers can identify early-stage ovarian cancer with extremely high sensitivity and moderate specificity.

IMPLICATIONS

Elevation of one or more serum markers should be evaluated further as an indication for transvaginal sonography in apparently healthy women. Such a strategy might substantially reduce the expense and improve the specificity of screening compared to the use of ultrasound alone. Prospective studies with a large cohort of patients at high risk for ovarian cancer will be required to confirm these findings.

OVX1 radioimmunoassay complements CA-125 for predicting the presence of residual ovarian carcinoma at second-look surgical surveillance procedures

PURPOSE

At second-look surgical surveillance procedures, normal CA-125 levels can be associated with persistent disease in 50% to 60% of patients. A novel radioimmunoassay (RIA) has been evaluated for the ability to identify patients with persistent disease who have normal levels of CA-125.

MATERIALS AND METHODS

The OVX1 double-determinant assay used a murine monoclonal antibody to detect an epitope on a high-molecular weight mucin-like glycoprotein.

RESULTS

Apparently healthy individuals had serum OVX1 levels of 2.23 +/- 2.48 U/mL (mean +/- SD). Elevated serum OVX1 levels (> 7.2 U/mL) were found in 5% of 184 normal individuals and in 70% of 93 epithelial ovarian cancer patients with clinically evident disease. Among sera from these ovarian cancer patients, OVX1 was elevated in 68% of 76 samples with CA-125 levels more than 35 U/mL and in 76% of 17 samples with CA-125 levels less than 35 U/mL. In serum samples obtained at the time of positive second-look laparotomy, 59% of 41 patients with CA-125 levels less than 35 U/mL had elevated OVX1 antigen levels, whereas 41% of 22 patients with CA-125 levels more than 35 U/mL had elevated serum OVX1 levels. In patients with negative second-look laparotomies, false-positive results were eliminated by increasing the threshold of OVX1 to 10.5 U/mL. At this level, 32% of 41 patients with positive second-look operations had an elevated OVX1 level, despite a normal CA-125 level. When used in combination, CA-125 (> 35 U/mL) and OVX1 (> 10.5 U/mL) detected persistent disease in 56% of 63 patients with positive surveillance procedures, compared with 35% when CA-125 was used alone (P < .05).

CONCLUSION

An elevated OVX1 level can alert oncologists to the possibility that ovarian cancer has persisted, despite the return of CA-125 to a normal range.

A combination of two immunotoxins exerts synergistic cytotoxic activity against human breast-cancer cell lines

In previous studies, combinations of immunotoxins reactive with different cell-surface antigens have exerted additive cytotoxicity against tumor cells in culture. In this report we describe a combination of 2 immunotoxins that produce synergistic cytotoxic activity. Recombinantly derived ricin A chain (RTA) was conjugated with murine monoclonal antibodies (MAbs) 317G5, 260F9, 454A12 and 741F8 that bound to cell-surface determinants of 42, 55, 180 (transferrin receptor) and 185 kDa (HER-2/neu) expressed by the SKBr3 human breast-cancer cell line. When inhibition of clonogenic growth was measured in a limiting dilution assay, the combination of 260F9-RTA and 454A12-RTA produced synergistic cytotoxic activity against SKBr3 and 2 other breast-cancer cell lines. All other combinations produced only additive inhibition of clonogenic growth. Simultaneous binding of 260F9 and 454A12 was not supra-additive, but sub-populations of cells which lacked one or the other antigen could be detected. Kinetic studies of internalization, using antibodies conjugated with gold particles, indicated that 454A12 remained within peripheral endosomes for a longer interval in the presence of 260F9. This change in the traffic of the transferrin receptor may contribute to synergy between 260F9-RTA and 454A12-RTA.

Development of two new monoclonal antibodies reactive to a surface antigen present on human ovarian epithelial cancer cells

Monoclonal antibodies which bind selectively to cancer cells are currently used for tumor localization and for targeting cytotoxic reagents. The success of these approaches depends on the specificity of the antibody and its reactivity to a majority of the tumor samples. Frequently, monoclonal antibodies are generated by immunizing mice with antigenic preparations from a single tumor cell line. Antibodies generated under these conditions often react to a narrow range of tumors. In the present study, mice were immunized with multiple ovarian cancer cell lines in a sequential manner to amplify the immune response against common antigenic determinants expressed in these cell lines. Spleen cells from the immunized mice were then fused with NS-1 myeloma cells to establish hybridomas. Two cell lines were selected on the basis of their selective reactivity to ovarian cancer cells after extensive screening. Monoclonal antibodies OVX1 and OVX2 bound to all 5 ovarian carcinoma cell lines tested and did not bind to normal fibroblast cells. These antibodies recognized a unique antigenic determinant present in ovarian and breast cancer cells. Cross-blocking studies showed that the binding of OVX1 and OVX2 is not displaceable by 10 other previously described anti-ovarian antibodies including OC125. In immunocytochemical studies, OVX1 reacted to a majority of ovarian cancer tissues (17 of 20) and did not bind to normal ovarian tissues. Preliminary results indicate that OVX1 and OVX2 antibodies are directed to a high molecular weight antigen. These antibodies could be used in the preparation of cytotoxic conjugates.

Coexpression of different antigenic markers on moieties that bear CA 125 determinants

CA 125 has been extensively evaluated as a serum marker for monitoring patients with epithelial ovarian carcinoma. Recently, consideration has been given to the use of CA 125 as one component in a strategy for early detection of this disease. A number of benign conditions can, however, increase CA 125 in serum, limiting the utility of a single antigen determination for identifying ovarian cancer patients. Coexpression of different epitopes on the high molecular weight complexes that express CA 125 determinants might provide a more specific test for malignant disease, provided that adequate sensitivity were maintained. To determine how frequently determinants are coexpressed, macromolecular moieties containing CA 125 determinants have been isolated from ascites fluid of ovarian cancer patients by immunoaffinity chromatography. CA 125+ moieties have been probed on Western transfers with several murine monoclonal antibodies that recognize distinct tumor-associated epitopes. Marked heterogeneity was observed between patients with regard to antigenic determinants that could be coexpressed with CA 125. A fraction of ascites fluids from different ovarian cancer patients contained moieties which bound to OC 125 on a solid phase immmunoadsorbent and which also bound 125I-labeled monoclonal antibodies NS 19-9, B72.3, DF3, or the novel murine monoclonal antibody OC 3632 in a double determinant immunoradiometric assay. Serum samples were evaluated from patients with ovarian cancer and from apparently healthy individuals. Coexpression of TAG 72 and CA 125 was observed most frequently. When the double determinant assay for coexpression of TAG 72 and CA 125 was compared to assays for the individual antigens, the assay for coexpression was substantially less sensitive than those for the individual markers.

Antiribophorin antibodies inhibit the targeting to the ER membrane of ribosomes containing nascent secretory polypeptides

Polyclonal antibodies directed against ribophorins I and II, two membrane glycoproteins characteristic of the rough endoplasmic reticulum, inhibit the cotranslational translocation of a secretory protein growth hormone into the lumen of dog pancreas or rat liver microsomes. As expected, site-specific antibodies to epitopes located within the cytoplasmic domain of ribophorin I, but not antibodies to epitopes in the luminal domain of this protein, were effective in inhibiting translocation. Since monovalent Fab fragments were as inhibitory as intact IgG molecules, ribophorins must be closely associated with the translocation site and, therefore, are likely to function at some stage in the translocation process. In all cases, the antibodies that inhibited translocation also caused a significant reduction in total protein synthesis and treatments that neutralized their capacity to inhibit translocation also prevented their inhibitory effect on protein synthesis. This would be expected if the antibodies blocked the membrane-mediated relief of the SRP-induced arrest of polypeptide elongation. The antibodies were effective only when added before translocation was allowed to begin. In this case, they prevented the targeting of active ribosomes containing mRNA and nascent chains to the ER membrane. Thus, ribophorins must either directly participate in targeting or be so close to the targeting site that the antibodies sterically blocked this early phase of the translocation process.

[Synergistic antitumor activity of human breast cancer immunotoxins]

Three anti-breast carcinoma monoclonal antibodies 317G5, 260F9 and 741F8 linked to ricin A chain (rRTA) were selected for the present investigation. Attempts were made to understand the relative efficiency of these immunotoxins in relation to: a) binding, b) internalization, and c) clonogenic suppression of breast cancer cells in vitro. The results indicated that 317G5-rRTA combined with 260F9-rRTA had synergistic antitumor activity against SKBr3 breast carcinoma cell line. Individually, 10 micrograms/ml 260F9-rRTA or 317 G5-rRTA alone could only eliminate 2-3 logs of clonogenic SKBr3 cells. When used in combination, 260F9-rRTA and 317G5-rRTA, 1 microgram/ml each, could kill 4 logs of clonogenic tumor cells. The mechanism of the synergistic action is discussed.

Use of immunotoxins in combination to inhibit clonogenic growth of human breast carcinoma cells

Substantial heterogeneity has been observed in the expression of individual antigens within tumor cell populations. Immunotoxins which bind to different cell surface antigens might exert additive or synergistic cytotoxicity when used in combination to eliminate all clonogenic cells within a tumor. Immunotoxins have been prepared by conjugating recombinantly derived toxin A chain to different monoclonal reagents which recognize cell surface determinants of Mr 42,000 (317G5), 55,000 (260F9), and 200,000 (741F8). Each immunotoxin was evaluated for binding, internalization, and cytotoxicity with four breast cancer cell lines. Each of the three immunotoxins bound to the SKBr3 cell line and exerted antitumor activity in a limiting dilution clonogenic assay. Simultaneous treatment with two immunotoxins produced additive antitumor activity with each of the possible combinations. Additive binding could be demonstrated by immunofluorescent techniques, however, with only one of three combinations. With two of the three combinations, subpopulations of tumor cells could be identified which lacked one or the other antigenic determinant but not both. Consequently, log-additive antitumor activity was produced by immunotoxins in combination, and heterogeneity of antigenic targets may have contributed to the combined cytotoxicity in some but not all cases.

Reconstitution of translocation-competent membrane vesicles from detergent-solubilized dog pancreas rough microsomes

Dog pancreas rough microsomes were solubilized in 1% octyl beta-glucoside, and membrane vesicles were reconstituted by slow 30-fold dilution with a buffer of low ionic strength. Asymmetric assembly of the membranes occurred during reconstitution since the vesicles formed contained ribosomes bound only to the vesicular outer surfaces. The reconstituted vesicles were similar in protein composition to native rough microsomes, although these vesicles were largely devoid of luminal-content proteins. These reconstituted vesicles could translocate and process nascent secretory (human placental lactogen) and membrane proteins (influenza hemagglutinin and rat liver ribophorin I) synthesized in cell-free translation systems programmed with the corresponding mRNAs. Signal cleavage and N-glycosylation only occurred when the reconstituted membranes were present during translation, providing evidence that the translocation apparatus was asymmetrically assembled into the reconstituted membranes. When a supernatant lacking ribosomes and particles greater than 50S from centrifuging the detergent-solubilized microsomes at high speed was used for reconstitution, smooth-surfaced membrane vesicles were obtained that, except for the absence of ribosomal proteins, were similar in protein composition to that of the reconstituted vesicles from total solubilized rough microsomes. The reconstituted smooth-surfaced vesicles, however, were totally inactive in cotranslational processing and translocation of nascent polypeptides. These findings suggest that ribosomes and/or large macromolecular complexes, not dissociated under our solubilization conditions, are essential for in vitro assembly of a functional translocation apparatus.

Assay of biological activity of synthetic yeast alanine transfer RNA (tRNAAlay)

The biological activity of the synthetic tRNAAlay was studied with an extremely sensitive method. tRNAAlay accepted alanine in the presence of rat liver aminoacyl-tRNAAlay-synthetase (this was called the accepting activity). The aminoacylated tRNAAlay was conveniently precipitated by ethanol with good recovery. The efficiency of transferring alanine from the aminoacylated tRNAAlay into the protein was determined in in vitro rabbit reticulocyte lysate cell-free protein-synthesizing system (this was called the incorporation activity). Both accepting and incorporation activities could be determined in one assay with only 5-7 pmoles of tRNAAlay either in ligation mixture or in purified form. Our results show that the accepting activities of the synthetic products were 51.6-65.6% and 91.3-106.0% of that of natural and reconstituted natural tRNAAlay respectively. The efficiency of the incorporation of alanine in the aminoacylated tRNAAlay into the protein was 61.6-63.1%, corresponding to 90.6-91.7% and 97.2-115.8% of that of the natural and the reconstituted natural tRNAAlay respectively.

Total synthesis of yeast alanine transfer ribonucleic acid

By a combination of chemical and enzymatic methods, small oligonucleotides with lengths varying from 2 to 8 nucleotides were synthesized from mononucleotides. The small oligonucleotides were then ligated with T4 RNA ligase into six large oligonucleotides (9 to 19 nucleotides long) which were further ligated to form two half molecules with 35 and 41 nucleotides respectively. Finally, the two synthetic half molecules were annealed and ligated to obtain the whole molecule of yeast alanine tRNA (tRNAAlay). Prior to this, two semi-syntheses were performed, i.e. ligation of the synthetic 5'-half molecule with the natural 3'-half molecule and that of the natural 5'-half molecule with the synthetic 3'-half molecule. Both the semi-synthetic tRNAAlay and the synthetic tRNAAlay occupy the same position as the natural tRNAAlay after electrophoresis on a 20% polyacrylamide gel. They have the same chemical composition (containing 9 modified nucleotides of 7 different species) and structure as the natural tRNAAlay and are biologically active, i.e. accepting and transferring alanine into proteins in a cell-free protein synthesizing system, the accepting activity of the synthetic product is 52-66% of that of the natural tRNAAlay and 91-106% of that of the reconstituted product of the two natural half molecules. The incorporation activity of alanine into proteins of the synthetic 3H-alanine tRNAAlay is 63%, corresponding to 91% of that of the natural tRNAAlay and 115% of that of the reconstituted product of the two natural half molecules. To the best of our knowledge, this is the first time that a natural RNA with biological activity is synthesized.