Tumour associated antigens CA 15.3 and CA 125 in ovarian cancer

CA 125 and CA 15.3 antigens were determined by enzyme immunoassay in 78 patients with ovarian cancer for a total of 540 determinations. The antigens were also investigated in sera from 100 women with other gynaecological diseases, 82 lung cancer patients and in 39 pleural fluids of varying origin. CA 15.3 reference values were evaluated in 91 healthy women (cut-off: 25 U/ml). CA 15.3 sensitivity at diagnosis (60%) and for detecting relapse (44%) was lower than that of CA 125 (90% and 64.7%, respectively). However, CA 15.3 does not increase with aspecific mesothelial cell reaction and thus it is more specific than CA 125. Combined use of the markers during follow-up improves early detection of relapse (at least one of the two was positive in 79% of cases). Therefore both CA 15.3 and CA 125 should be routinely determined for the detection and monitoring of ovarian cancer.     

Tissue quantification of CA 125 in epithelial ovarian cancer.

The objectives of this study were the determination of CA 125 in the cytosol of healthy and carcinomatous ovarian tissue by immunoanalysis, analysis of its correlation with the biological characteristics of ovarian carcinoma, determination of serum CA 125 levels, and study of the prognostic value of the marker in cytosol. The levels of the marker depend not only on the tumor's production rate, so its determination in tissue can indicate more accurately if the tumor is a producer of the marker and establish its value for the prognosis of the disease. Determination of CA 125 in tissue was performed by immunoanalysis in 50 ovarian epithelial cancer samples, 13 benign pathology samples and 32 healthy ovary samples. The presurgical serum level of the marker was also obtained. The correlation between the CA 125 level in the cytosol and the different biological characteristics of the ovarian carcinoma, the serum levels of the marker and survival were analyzed. The CA 125 level proved to be higher in malignant tissue (p < 0.0001). There was a significant association between the tissue marker and histological type (high CA 125 was associated with serous and endometrioid tumors) and between the marker and survival. No relation with stage was found. There was a correlation between the CA 125 level in the cytosol and serum both variables being dependent, with a correlation coefficient of 0.44. This good correlation speaks in favor of the usefulness of CA 125 determination in serum in the follow-up of ovarian cancer. Tumors having high tissue expression of CA 125 were found to have a double relative risk of death, independently of tumor stage.     

The role of CA 125 in screening for ovarian cancer

Ovarian cancer has the worst prognosis of any gynaecological malignancy, primarily because it tends to present at an advanced stage. The excellent survival rates of early stage disease have provided the rationale for efforts to detect ovarian cancer early by screening, in the hope that survival rates will be improved. Available data suggests that CA 125 is elevated in the majority of epithelial ovarian malignancies prior to clinical presentation. Large trials of screening for ovarian cancer indicate that using a CA 125 cutoff value of 30 U/mL has good sensitivity, but inadequate specificity for detecting preclinical disease. Use of transvaginal ultrasonography as a second-line test in women with elevated CA 125 levels improves specificity to acceptable levels, as does use of a mathematical algorithm which analyses rates of change of CA 125. Two major randomised controlled trials, investigating the effect of screening strategies incorporating CA 125 on mortality, are currently underway.     

CA 125 production and release by ovarian cancer cells in vitro

The antigenic determinant CA 125 is a high molecular weight glycoprotein which is elevated in more than 80% of patients with epithelial ovarian cancer. Despite its good performance as a human tumor marker, only little is known about its physiological function. According to recent publications, CA 125 production and release appear to be related to cellular growth. In order to investigate this putative relationship more closely, we analyzed the pattern of CA 125 production and release by ovarian cancer cells during exponential cell growth, during cell cycle arrest by colchicine and during inhibition of cellular protein synthesis by cycloheximide. The results were correlated with the cell cycle distribution. According to our results, the main determinant of CA 125 release into the culture supernatant is the total cell count. Although cell cycle arrest in the G2 + M phase by means of colchicine treatment resulted in the death of most cells, which was reflected by an increased release of CA 125, no differences in the intracellular production rate between colchicine treated and untreated cells were seen. In contrast, treatment of cells with cycloheximide not only resulted in decreasing cell numbers but also in a complete inhibition of CA 125 production by surviving cells.     

Prognostic value of CA125 kinetics and half-life in advanced ovarian cancer

This retrospective study was undertaken in order to assess the prognostic value of prechemotherapy serum CA125 level, CA125 kinetics, and CA125 half-life compared to the ten common clinicopathological variables in patients with advanced ovarian cancer (AOC). CA125 serum levels were determined before and during induction cisplatin polychemotherapy in 222 patients. A prechemotherapy CA125 level higher than 35 U/mL was found in 134 patients. Blood samples were further obtained before each course of chemotherapy (CT). CA125 half-life values were calculated in 112 patients with CA125 levels above 60 U/mL using van der Burg's exponential regression model. The prechemotherapy CA125 level had no prognostic value for survival. However, the median survival time of patients with CA125 levels below the upper normal limit of normality after two courses of CT was 101 months compared to a median survival of 21 months in patients without CA125 normalization (p=0.0000). Half-life calculation showed a significant correlation with survival. The median survival times of patients with T1/2 <20 days and T1/2 >20 days were 101+ and 18 months, respectively (p=0.0003). In a survival analysis using the Cox proportional hazard model, independent prognostic variables for survival included therapeutic response (p<0.0001), Karnofsky index (p<0.0001), residual disease (p<0.0001), tumor grade (p=0.0002), CA125 half-life (p=0.007), and CA125 kinetics (p=0.04). As a consequence, the possibility to predict treatment response by the CA125 half-life during chemotherapy and the time needed for normalization of CA125 levels can divide patients into good and poor prognostic groups early during chemotherapy.     

Early detection of ovarian cancer: preliminary results of the Yale Early Detection Program.

Eighty-four women at high risk for ovarian cancer by having first-degree relatives with epithelial ovarian cancer participated in a newly established, early ovarian cancer detection program at Yale University. Participants were to be evaluated with physical examinations and circulating tumor markers at entry and every six months thereafter. Endovaginal ultrasound and color Doppler flow studies were to be performed at three and nine months following entry into the program. In addition, women were encouraged to follow American Cancer Society guidelines for mammography. Stool was checked for occult blood. Endometrial sampling was offered to post-menopausal women. No participant has developed an ovarian cancer since entering the program. One woman has been diagnosed to have breast cancer. False-positive levels of circulating tumor markers (CA 125, 4/84 [4.8 percent]; lipid-associated sialic acid in plasma, 13/84 [15.5 percent]; NB/70K, 4/84 [4.8 percent]; and urinary gonadotropin fragment, 1/65 [1.5 percent]) were observed on entry into the program. Low resistive indices (less than 0.5) were documented in 8/91 (8.8 percent) ovaries studied by the color Doppler flow technique. One participant underwent a laparotomy based on a false-positive endovaginal ultrasound examination. Tests now being employed in community practice have a high likelihood of being associated with false-positive results. Therapeutic interventions based on isolated abnormal tumor markers or ultrasound studies obtained from women with family histories of ovarian cancer may lead to inappropriate surgery. It is necessary for cancer centers to develop expertise in ovarian cancer detection techniques to advise physicians in their geographic areas appropriately about the significance of the abnormal screening test.     

A human/mouse chimeric monoclonal antibody against CA125 for radioimmunoimaging of ovarian cancer

Murine monoclonal antibody 196-14 recognizes the ovarian-cancer-associated antigen CA 125, but the epitope it recognizes is different from that of monoclonal antibody OC125. We developed a human/mouse chimeric 196-14 using the variable regions of the murine 196-14 and human heavy-chain (l) and light-chain () constant regions. Cell binding and competitive inhibition assays using chimeric 196-14 labeled with¹²⁵I,¹¹¹In or^99mTc demonstrated that the in vitro immunoreactivity of the chimeric antibody was identical to that of the parental murine monoclonal antibody. However, in mice bearing human ovarian cancer xenografts, the clearance from blood was faster and absolute levels of accumulation in the tumor were lower for the¹²⁵I-labeled or^99mTc-labeled chimeric antibody than for the murine antibody labeled with the corresponding radionuclides. The tumor-to-blood radioactivity ratio was not significantly different between the chimeric antibody and the murine antibody, regardless of the radionuclide used for labeling. Chimeric antibody 196-14 labeled with¹³¹I,¹¹¹In or^99mTc is promising for the radioimmunoimaging of ovarian cancer.     

Roles of CA125 in diagnosis,prediction, and oncogenesis of ovarian cancer

After it was discovered approximately 40 years ago, carbohydrate antigen 125 (CA125) became the most widely used and concerning biomarker in ovarian cancer screening. However, there is still controversy about its role in clinical practice. CA125 is not sufficiently reliable in diagnosis to screen for early-stage ovarian cancer. On the other hand, CA125 has been a valuable indicator for evaluating chemotherapeutic efficacy and prognosis. We still do not know much about its biological role, and several studies have indicated that this marker participates in the occurrence and development of ovarian cancer. Currently, an increasing number of scholars have begun to pay attention to CA125-targeted treatment strategies. In the interest of better design and development of anticancer therapies, a renewed and systematic understanding of the roles of CA125 in diagnosis, prediction, and tumorigenesis is warranted.     

The biological tumor markers' myopia: a model with CA 125 and second-look in ovarian cancer

Preoperative CA 125 levels were measured in 36 patients with advanced epithelial ovarian carcinoma in clinical response undergoing a second-look operation. All the patients had positive levels (greater than 35 U/ml) of this tumor marker at diagnosis. The correlation between antigen levels and disease status at surgery revealed a sensitivity of this assay of 0.55 (only 11/20 patients still with tumor had positive levels) and a specificity of 0.94 (15/16 patients with no tumor had less than 35 U/ml). The predictive value of a positive test was 0.92. This method unfortunately proved unable to recognize microscopic residual tumor burden, less than 0.5 cm.     

Relationship of CA 125 and CA 19.9 with lung carcinoma histological subtype: preliminary study

The aim of this work was to study the possible utility of simultaneous determination of CA 125 and CA 19.9 in patients with lung cancer. Serum levels of both markers were studied in 87 patients without metastases (Mo), 72 patients with distant metastases (MT) and 15 cases without clinical evidence of disease after primary treatment (NED). Sixty-five tumors were epidermoid, 34 were adenocarcinomas, 24 were cell undifferentiated carcinomas and 51 were small-cell carcinomas. Sera from 75 healthy subjects and 20 patients with benign lung disease were used as controls. The cut-off values used were 35 and 37 U/ml for CA 125 and CA 19.9, respectively. CA 125 and CA 19.9 serum levels were within normal limits in all control patients. In NED patients these markers were not elevated, except in one with chronic liver disease who showed elevated CA 19.9 (76 U/ml). Twenty-five percent of Mo lung cancer patients and 40.3% of MT cases had CA 19.9 over 37 U/ml. Abnormally high levels of CA 125 were found in 18.7% and 22.9% of Mo and MT patients, respectively. Sixty percent of patients with large cell undifferentiated carcinoma had elevated CA 125 (mean 176 U/ml) compared to 15.4% of patients with all other histological types of tumors combined (54.3 U/ml, p less than 0.01). CA 19.9 serum levels were also more often elevated in patients with large cell undifferentiated carcinomas (50%, 7/14 cases) than in other histological types (30%, 36/120 patients), but the difference was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)     

Solution structure of the SEA domain from the murine homologue of ovarian cancer antigen CA125 (MUC16)

Human CA125, encoded by the MUC16 gene, is an ovarian cancer antigen widely used for a serum assay. Its extracellular region consists of tandem repeats of SEA domains. In this study we determined the three-dimensional structure of the SEA domain from the murine MUC16 homologue using multidimensional NMR spectroscopy. The domain forms a unique alpha/beta sandwich fold composed of two alpha helices and four antiparallel beta strands and has a characteristic turn named the TY-turn between alpha1 and alpha2. The internal mobility of the main chain is low throughout the domain. The residues that form the hydrophobic core and the TY-turn are fully conserved in all SEA domain sequences, indicating that the fold is common in the family. Interestingly, no other residues are conserved throughout the family. Thus, the sequence alignment of the SEA domain family was refined on the basis of the three-dimensional structure, which allowed us to classify the SEA domains into several subfamilies. The residues on the surface differ between these subfamilies, suggesting that each subfamily has a different function. In the MUC16 SEA domains, the conserved surface residues, Asn-10, Thr-12, Arg-63, Asp-75, Asp-112, Ser-115, and Phe-117, are clustered on the beta sheet surface, which may be functionally important. The putative epitope (residues 58-77) for anti-MUC16 antibodies is located around the beta2 and beta3 strands. On the other hand the tissue tumor marker MUC1 has a SEA domain belonging to another subfamily, and its GSVVV motif for proteolytic cleavage is located in the short loop connecting beta2 and beta3.     

Tumor antigen NB/70K and CA 125 levels in the blood of preoperative ovarian cancer patients and controls: a preliminary report of the use of the NB12123 and CA 125 radioimmunoassays alone and in combination

The NB12123 and CA125 radioimmunoassays, murine monoclonal antibody assays for measuring circulating levels of human ovarian tumor associated antigens NB/70K and CA 125, respectively, have been previously described. In the present study, preoperative serum samples were obtained from patients undergoing laparotomy for benign neoplastic ovarian tumors (N = 16), cancer of the cervix (N = 22), cancer of the uterus (N = 20), and cancer of the ovary (N = 47). Controls (N = 50) were obtained from healthy blood bank donors. No correlation was observed between the levels of NB/70K and CA 125 in these samples (r2 = .079, linear regression analysis). In general, increasing levels of both antigens were present with increasing tumor burden and higher histological grade. In addition, both markers were most elevated in the serum of ovarian cancer patients with serous and unclassified adenocarcinomas. Using 40 AU and 35 unit cut-offs for the NB/70K and CA 125 assay, respectively, overall specificity for healthy controls and patients with benign diseases approaches 100%. The combined sensitivity of the assays for ovarian cancer patient sera in this study indicates that the assays may be helpful in establishing a pre operative diagnosis of ovarian cancer. Complementarity of the NB/70K and CA 125 assays has been demonstrated, indicating that one or both assays may be used to monitor as many as 85% of ovarian cancer patients.     

Characterization of the oligosaccharides associated with the human ovarian tumor marker CA125

CA125 is a mucin commonly employed as a diagnostic marker for epithelial ovarian cancer. Induction of humoral responses to CA125 leads to increased survival times in patients with this form of cancer, suggesting a potential role for this mucin in tumor progression. In this study, oligosaccharides linked to CA125 derived from the human ovarian tumor cell line OVCAR-3 were subjected to rigorous biophysical analysis. Sequencing of the O-glycans indicates the presence of both core type 1 and type 2 glycans. An unusual feature is the expression of branched core 1 antennae in the core type 2 glycans. CA125 is also N-glycosylated, expressing primarily high mannose and complex bisecting type N-linked glycans. High mannose type glycans include Man5-Man9GlcNAc2. The predominant N-glycans are the biantennary, triantennary, and tetraantennary bisecting type oligosaccharides. Remarkably, the N-glycosylation profiles of CA125 and the envelope glycoprotein gp120 (derived from H9 lymphoblastoid cells chronically infected with HIV-1) are very similar. The CA125-associated N-glycans have also recently been implicated in crucial recognition events involved in both the innate and adaptive arms of the cell-mediated immune response. CA125 may therefore induce specific immunomodulatory effects by employing its carbohydrate sequences as functional groups, thereby promoting tumor progression. Immunotherapy directed against CA125 may attenuate these immunosuppressive effects, leading to the prolonged survival of patients with this extremely serious form of cancer.     

Prevalence screening for ovarian cancer in postmenopausal women by CA 125 measurement and ultrasonography.

OBJECTIVE--To assess the performance of the sequential combination of serum CA 125 measurement and ultrasonography in screening for ovarian cancer. DESIGN--The serum CA 125 concentration of each subject was determined and those with a concentration > or = 30 U/ml were recalled for abdominal ultrasonography. If ultrasonography gave abnormal results surgical investigation was arranged. Volunteers were followed up by annual postal questionnaire. SETTING--General practice, occupational health departments, ovarian cancer screening clinic. SUBJECTS--22,000 women volunteers who were postmenopausal and aged over 45 years. MAIN OUTCOME MEASURES--Apparent sensitivity, specificity, positive predictive value, years of cancer detected. RESULTS--41 women had a positive screening result and were investigated surgically. 11 had ovarian cancer (true positive result) and 30 had other disorders or no abnormality (false positive result). Of the 21,959 volunteers with a negative screening result, eight subsequently presented clinically with ovarian cancer (false negative result) and 21,951 had not developed ovarian cancer during follow up (apparent true negative result). The screening protocol achieved a specificity of 99.9%, a positive predictive value of 26.8%, and an apparent sensitivity of 78.6% and 57.9% at one year and two year follow up respectively. The estimated number of years of cancer detected by the prevalence screen was 1.4 years. CONCLUSIONS--This screening protocol is highly specific for ovarian cancer and can detect a substantial proportion of cases at a preclinical stage. Further investigation is required to determine the effect of the screening protocol on the ratio of early to late stage disease detected and on mortality from ovarian cancer.     

X-ray analysis of a progesterone-binding protein (uteroglobin): preliminary results

Uteroglobin, which is a progesterone-binding protein of the rabbit uterine secretion, has been crystallized and subjected to X-ray diffraction analysis. Two crystalline forms have been observed: a triclinic one ($\text{P1, Z = 2, a = 36.36 (4)}\text{A}\text{?}\text{, b = 37.40 (4)}\text{A}\text{?}\text{, c = 53.28 (4)}\text{A}\text{?}\text{, α = 104.6 (1) °, β = 97.0 (1) °, γ = 111.3(1) °}$); and an orthorhombic one for which the cell is C-centred with $\text{a = 50.86 (5)}\text{A}\text{?}\text{, b = 52.22 (5)}\text{A}\text{?}\text{, c = 47.28 (5)}\text{A}\text{?}$, space group C222₁, Z = 4. Three isomorphous derivatives have been obtained. The crystals appear suitable for detailed study of the three-dimensional structure of the protein.     

An antibody-lectin sandwich assay for the determination of CA125 antigen in ovarian cancer patients

A two-step forward sandwich assay was developed for the determination of the ovarian tumour associated glycoconjugate antigen CA125 with anti-CA125 Monoclonal antibody B27.1 on the solid phase and¹²⁵I-labelled wheat germ lectin as tracer in the solution phase. This Mab-lectin heterosandwich assay was optimized and the clinical utility was evaluated in sera from healthy volunteers and ovarian cancer patients. A correlation was established between Mab-lectin assay and the dual monoclonal antibody sandwich assay, TRUQUANT®OV2 RIA, that uses the same MAb B27.1 on the solid phase and a second¹²⁵I-labelled B43.13 MAb in the solution phase. A potentially improved clinical utility is suggested for the Mab-lectin assay. The unique format seems to identify novel isoforms of CA125 with different carbohydrate side chains that would otherwise be undetectable in the MAb-MAb sandwich assay wherein the paratopes are likely directed to protein determinants.     

Binding of ovarian cancer antigen CA125/MUC16 to mesothelin mediates cell adhesion

Mesothelin is a glycosylphosphatidylinositol-linked cell surface molecule expressed in the mesothelial lining of the body cavities and in many tumor cells. Based on the finding that a soluble form of mesothelin specifically binds to ovarian carcinoma cell line OVCAR-3, we isolated cDNAs encoding a mesothelin-binding protein by expression cloning. The polypeptides encoded by the two cloned cDNA fragments matched to portions of CA125, an ovarian cancer antigen and a giant mucin-like glycoprotein present at the surface of tumor cells. By flow cytometric analysis and immunoprecipitation, we demonstrate that CA125 binds to mesothelin in a specific manner. Binding of CA125 to membrane-bound mesothelin mediates heterotypic cell adhesion as anti-mesothelin antibody blocks binding of OVCAR-3 cells expressing CA125 to an endothelial-like cell line expressing mesothelin. Finally, we show that CA125 and mesothelin are co-expressed in advanced grade ovarian adenocarcinoma. Taken together, our data indicate that mesothelin is a novel CA125-binding protein and that CA125 might contribute to the metastasis of ovarian cancer to the peritoneum by initiating cell attachment to the mesothelial epithelium via binding to mesothelin.     

Risk of diagnosis of ovarian cancer after raised serum CA 125 concentration: a prospective cohort study.

OBJECTIVE: To determine the risk of invasive epithelial ovarian cancer and fallopian tube cancer associated with a raised concentration of the tumour marker CA 125 in asymptomatic postmenopausal women. DESIGN: Serum CA 125 concentration was measured annually in study participants for one to four years. Participants with a concentration > or = 30 U/ml were recalled for abdominal ultrasonography. Follow up was by annual postal questionnaire. SETTING: General practice, occupational health departments, ovarian cancer screening unit in a teaching hospital. SUBJECTS: 22,000 volunteers, all postmenopausal women > or = 45 years of age; recruited between 1 June 1986 and 1 May 1990. INTERVENTION: Surgical investigation if the ultrasound examination was abnormal. MAIN OUTCOME MEASURES: Cumulative and relative risk of developing an index cancer (invasive epithelial cancer of the ovary or fallopian tube) after a specified CA 125 result. RESULTS: 49 index cancers developed in the study population during a mean follow up of 6.76 years. The overall cumulative risk of developing an index cancer was 0.0022 for the entire study population and was lower for women with a serum CA 125 concentration < 30 U/ml (cumulative risk 0.0012) but was appreciably increased for women with a concentration > or = 30 U/ml (0.030) and > 100 U/ml (0.149). Compared with the entire study population the relative risk of developing an index cancer within one year and five years was increased 35.9-fold (95% confidence interval 18.3 to 70.4) and 14.3-fold (8.5 to 24.3) respectively after a serum CA 125 concentration > or = 30 U/ml and 204.8-fold (79.0 to 530.7) and 74.5-fold (31.1 to 178.3) respectively after a concentration > or = 100 U/ml. CONCLUSION: CA 125 is a powerful index of risk of ovarian and fallopian tube cancer in asymptomatic postmenopausal women.     

Molecular cloning of the CA125 ovarian cancer antigen: identification as a new mucin, MUC16

CA125 is an ovarian cancer antigen that is the basis for a widely used serum assay for the monitoring of patients with ovarian cancer; however, detailed information on its biochemical and molecular nature is lacking. We now report the isolation of a long, but partial, cDNA that corresponds to the CA125 antigen. A rabbit polyclonal antibody produced to purified CA125 antigen was used to screen a lambdaZAP cDNA library from OVCAR-3 cells in Escherichia coli. The longest insert from the 54 positive isolated clones had a 5797-base pair sequence containing a stop codon and a poly(A) sequence but no clear 5' initiation sequence. The deduced amino acid sequence has many of the attributes of a mucin molecule and was designated CA125/MUC16 (gene MUC16). These features include a high serine, threonine, and proline content in an N-terminal region of nine partially conserved tandem repeats (156 amino acids each) and a C-terminal region non-tandem repeat sequence containing a possible transmembrane region and a potential tyrosine phosphorylation site. Northern blotting showed that the level of MUC16 mRNA correlated with the expression of CA125 in a panel of cell lines. The molecular cloning of the CA125 antigen will lead to a better understanding of its role in ovarian cancer.