The radioimmunoassay of circulating carcinoembryonic antigen of the human digestive system

Overview of tumor immunology in gynecologic oncology

Highlights of recent advances in the field of gynecologic tumor immunology are presented in an effort to demonstrate that at least some cancers of the female genitalia evoke an immune response that can be quantitated in the laboratory. The overview will discuss investigations into the various in vitro assays of both humoral and cell-mediated immunity. The concept of clinical testing of delayed hypersensitivity reactions as it relates to the clinical outcome of the patients with malignancy is presented. Along this line, preliminary studies at our own institution are reviewed in an attempt to establish a rough correlation between patients with a healthy outcome and patients with a strong immunologic index as manifested by skin testing. A progress report on the isolation of tumor-associated antigens in cancer of the cervix and ovary is presented. The prevalence of carcinoembryonic antigen in the plasma of patients with gynecological malignancy is then discussed. Finally, approaches to immunotherapy are discussed, with a suggestion as to future directions.

Immunological cross-reactivity of antibodies to a synthetic undecapeptide analogous to the amino terminal segment of carcinoembryonic antigen, with the intact protein and with human sera

A peptide corresponding to the 11 amino acid residues of the NH2-terminal portion in the sequence of carcinoembryonic antigen(CNTHETIC CEA(1-11) peptide was attached by means of a water-soluble carbodiimide reagent to multichain poly(DL-alanine( as well as to bovine serum albumin. Both macromolecular conjugates provoked in rabbit anti-CEA(1-11) peptide antibodies. The specificity of this immunological system and the crossreactivity between the peptide and intact CEA were investigated by two methods--passive hemagglutination and modified bacteriophage inactivation. Hemmagglutination experiments showed that not only anti-CEA(1-11) sera, but also anti-CEA sera, agglutinated CEA(1-11)-coated sheep erythrocytes, and both these reactions were inhibited with CEA(1-11) peptide. In experiments with the chemically modified bacteriophage technique CEA(1-11)-coated phase was efficiently inactivated with antisera against the CEA(1-11) conjugates, and the inactivation reaction could be totally inhibited with the free peptide. The semipure CEA, but not the pure protein, could also inhibit the phage inactivation, even though less efficiently. On the basis of the above results, sera of some cancer patients were tested for their capacity to inhibit the inactivation of CEA(1-11)-coated phage by means of anti-CEA(1-11) antiserum. The results indicate that sera from a large proportion of patients with adenocarcinomas of the digestive tract, pancreas, and breast are capable of inhibiting the above inactivation, whereas most normal sera do not inhibit.

Detection of tumor-associated antigen in human melanoma cell line supernatants

Spent tissue culture medium (CDM-S) removed from a single cell line of human malignant melanoma grown in serum-free CDM, contained tumor-associated antigenic activity. Antibodies to CDM-S measured by complement fixation were detected in 44% (31/70) melanoma, 55% (15/27) sarcoma, 63% (24/38) carcinoma and 15% (11/72) normal sera. Delayed cutaneous hypersensitivity reactions (DCHR) were demonstrated in 4/5 melanoma patients at a 500 mug dose, 3/5 at a 100 mug dose and in 1/7 carcinoma patients at the 500 mug dose. One ml of CDM-S was shown to contain antigen equivalent to that obtained from the membranes of 2.9 X 10(7) tissue-cultured melanoma cells. After purification, 84% (16/19) sera from melanoma patients, 66% (12/18) from sarcoma and carcinoma patients and 8% (2/26) from normal controls were positive to the antigen by complement fixation.

Monkey antisera with increased specificity to carcino-embryonic antigen (CEA)

Three Macaca irus monkeys were immunized with purified human CEA. One received unmodified CEA and two were immunized with haptenated (4-hydroxy-5-iodo-3-nitrophenyl acetyl) CEA. All three monkeys formed precipitating antibodies to CEA. The antisera did not precipitate the CEA-related normal glycoprotein antigen (NCA). In contrast, CEA-immunized rabbits, sheep and goats invariably form antibodies against NCA. Radio-immunoassays showed the monkey antisera to contain trace amounts of antibodies to NCA but the titers were about 10-1,000 times lower than those in rabbit and sheep sera with comparable anti-CEA titers. These results show that monkeys produce antibodies against CEA, but respond weakly to a normal, CEA-related antigen. The weak response to NCA suggests that monkeys may possess an NCA-related antigen. Antisera lacking reactivity to normal CEA-related antigens may be helpful in establishing a more specific diagnostic test for CEA.

Carcinoembryonic antigen in colorectal practice: report of three cases

CEA, in combination with the time-honored barium enema, sigmoidoscopy, rectal examination with guaiac determinations, and thorough clinical history, is a useful tool for the colorectal surgeon in following the progression of disease in both colorectal carcinoma patients and patients who have certain premalignant conditions. In this high-risk group of patients, CEA determinations as well as colonoscopy are becoming increasingly useful. That tumors on the left side are associated with higher CEA levels than those on the right side, due to vascular invasion or the grades of the tumors, and that often CEA antigenicity and severity of symptoms in ulcerative colitis correlate well, are emphasized. Finally, following total colectomy in five cases of ulcerative colitis, all CEA titers decreased to the normal range and have remained there.

CEA family syndrome. Abnormal carcinoembryonic antigen (CEA) levels in asymptomatic retinoblastoma family members

Plasma carcinoembryonic antigen (CEA) levels were studied in all available members of 17 families in which a presumed sporadic retinoblastoma had occurred. In 9 of the 17 families, close relatives of the patient had elevated CEA levels in the absence of demonstrable disease; this we have termed the "CEA family syndrome." In two families (Nos. 8 and 17) one or both parents and all of the siblings had elevated CEA levels. To our knowledge, this is the first report of abnormal CEA levels in unaffected family members of patients with nonadenocarcinoma-type malignancies. As follow-up studies of such families become available, detection of the "CEA family syndrome" may prove to be a useful means of locating individuals with inherited premalignant or malignant conditions and may provide a stimulus for additional clinical examination of asymptomatic individuals considered at risk for developing malignancies.

Fetal antigens in retinoblastoma

Plasma carcinoembryonic antigen (CEA) and alpha fetoprotein (AFP) levels were studied in five patients with retinoblastoma. CEA and AFP were found elevated in four of five patients prior to therapy. Following enucleation and/or radiation therapy, the elevated values were significantly lowered. This preliminary study suggests that CEA and AFP levels may be of value in the diagnosis of retinoblastoma, and that serial CEA levels may be useful in evaluation of retinoblastoma patients after treatment.

Plasma CEA, tumor CEA, and tumor histology

Carcinoembryonic antigen (CEA) has been thought to be a diagnostic and prognostic indicator of colorectal cancer. Initial descriptions of CEA as a tumor specific antigen suggests a relationship between tumor CEA and circulating plasma CEA. To define the relationship between CEA and colorectal carcinoma, we have studied the CEA concentration of preoperative plasma, tumor tissue, and normal bowel distant from tumor in 35 patients who had clinically curative resections. Tumor histology was evaluated for Dukes class, histologic grade, necrosis, and vessel invasion. Regression analysis yielded no evidence of correlation between tumor CEA and plasma CEA. No correlation could be shown between tumor concentration of CEA and the histological parameters previously noted. CEA was found in all specimens of normal bowel. Furthermore, in 34% of the cases studied, the tumor CEA was not significantly higher than in normal bowel. No significant difference was shown when histopathological findings were compared to normal and abnormal plasma CEA values. These findings suggest the following conclusions: CEA is not tumor specific. Increased levels of CEA in tumor tissue are not a constant finding in colorectal carcinoma. Tumor levels of CEA do not appear to correlate with histologic degree of tumor differentiation. Elevated plasma levels of CEA do not necessarily connote elevated tumor tissue levels of CEA, and conversely, normal plasma levels of CEA do not necessarily mean low levels of tumor CEA.

Carcinoembryonic antigen: clinical and historical aspects

To further define and determine the usefulness of CEA, 1100 CEA determinations have been made over the past two years at The Ohio State University Hospitals on patients with a variety of malignant and nonmalignant conditions. Correlation of CEA titers with history and clinical course has yielded interesting results not only in cancers of entodermally derived tissues, for which CEA has become an established adjunct in management, but also in certain other neoplasms and inflammatory states. The current total of 225 preoperative CEA determinations in colorectal carcinomas shows an 81% incidence of elevation, with postoperative titers remaining elevated in patients having only palliative surgery but falling to the negative zone after curative procedures. An excellent correlation exists between CEA levels and grade of tumor (more poorly differentiated tumors showing lower titers). Left-side colon lesions show significantly higher titers than right-side lesions. CEA values have been shown to be elevated in 90% of pancreatic carcinomas studied, in 60% of metastatic breast cancers, and in 35% of other tumors (ovary, head and neck, bladder, kidney, and prostate cancers). CEA levels in 35 ulcerative colitis patients show elevation during exacerbations (51%). During remissions titers fall toward normal, although in 31% still remaining greater than 2.5 ng/ml. In the six colectomies performed, CEA levels all fell into the negative zone postoperatively. Forty percent of adenomatous polyps showed elevated CEA titers (range 2.5-10.0) that dropped following polypectomy to the negative zone. Preoperative and postoperative CEA determinations are important in assessing the effectiveness of surgery. Serial CEA determinations are important in the follow-up period and in evaluation of the other modes of therapy (e.g., chemotherapy). These determinations of tumor antigenicity give the physician added prognostic insight into the behavior of the tumor growth. Rectal examination with guaiac determinations, sigmoidoscopy, cytology, barium enema, and a good clinical evaluation remain the primary tools for detecting colorectal disease. However, in the high-risk patient suspicious of developing cancer, CEA determinations as well as colonoscopy are now being used increasingly and provide additional highly valuable tools in the physician's armamentarium.

Carcinoembryonic antigen and bladder carcinoma

The 24-hour urinary carcinoembryonic antigen determinations were performed on 61 patients with different stages of bladder carcinoma. Elevated titers were found in 81 per cent of the patients with active tumors and falsely positive studies were found in 7 per cent. High stage lesions were found to have high carcinoembryonic antigen levels. Plasma carcinoembryonic antigen determinations were elevated in only 45 per cent of the patients with active tumors but further study may be warranted in advanced bladder cancer cases. The 24-hour urinary carcinoembryonic antigen measurements yield the highest percentage elevations in bladder carcinoma and further investigation is required to better define its clinical application.

Carcinoembryonic antigen: clinical application

Carcinoembryionic antigen (CEA) a glycoprotein extracted from colonic cancer tissue (beta-globulin electrophoretic mobility, sedimentation coefficient 7 to 8S, and mol wt approximately 200,000) can be detected and measured by radioimmunoassay. Clinical evaluations of CEA determination have given the following results: In health: (1) Serum CEA level is not influenced by sex, age, blood type, time of blood sampling, or family history of cancer; (2) serum CEA level is influenced by a history of smoking or inflammatory disease of the bowel, lung, pancreas, and other organs (occasionally, a CEA level as high as 10 ng/ml is noted); and (3) currently, CEA positivity is defined as greater than 2.5 ng/ml, however, 5 ng/ml may be more realistic. In cancer: (1) CEA level may be increased in primary cancer of the gastrointestinal (GI) tract as well as in non-GI neoplasia; (2) the CEA test is not recommended for screening to detect early cancer; (3) serum CEA level depends on the stage of the neoplasia and usually is not influenced by the grade of differentiation; and (4) markedly increased (greater than 25 ng/ml serum CEA values are highly suggestive of metastatic cancer, particularly hepatic metastasis. In biological fluid: The CEA or CEA-like activity can be measured in gastrointestinal secretions. Quantitative studies of CEA levels in such fluids may yield more information than is obtainable from studies of serum. However, this possibility needs more study at present. Therefore, the currently available CEA tests cannot replace any of the now standard diagnostic methods for cancer detection. This use for assessment of therapy in selected patients or for following those known to be a high risk for cancer appears promising in preliminary studies, but clinical value, if any, remains to be determined.

Immunologic approaches to the diagnosis of cancer

A variety of immunologic approaches can be applied to the diagnosis of human cancer, and these have the potential advantages of specificity and sensitivity. Many tumor distinctive markers have been detected in the circulation of cancer patients. Cancer patients frequently have detectably depressed immune competence, but also have cell-mediated and humoral immune reactivity against tumor-associated antigens. Radiolabeling of specific antibodies may allow localization in vivo of tumors. With each of these potential immunodiagnostic approaches, it is necessary to systematically evaluate the assays and determine their value for specific clinical applications.

Carcinoembryonic antigen (CEA) as a prognostic and monitoring test in clinically complete resection of colorectal carcinoma

The prognostic and postoperative monitoring capabilities of the CEA assay were compared to pathological staging of the operative specimens, clinical followup including endoscopy, radiology and scanning techniques, as well as DNCB skin testing and laboratory enzyme determinations (alkaline phosphatase and transaminase). A total of 46 patients with curative resection for colorectal carcinoma were studied. This included 23 patients with recurrent tumors compared to 23 long-term survivors without signs of recurrence at the time of the study. Preoperative CEA determinations were a good prognostic tool comparable to pathological staging of the specimen. Post operative CEA monitoring was the earliest sign of recurrence in 14 of 23 patients and was positive at the time of recurrence determined by other methods in 20; it was negative in only three cases. The incidence of false positive results among the non recurrent group became a lesser problem when repeated elevated values were required before considering the patient as having a recurrence. From these data, it seems reasonable to propose the use of a second-look operation in patients with maintained elevation of circulating CEA and no clinical signs of tumor presence, if we are to treat recurrence at an early stage. Chemotherapy would be an alternative way to deal with this problem, since the absence of clinical signs in general correlate with small bulk of tumor which at this time may be more susceptible to chemotherapeutic agents.

Carcinoembryonic antigen in 228 patients with carcinoma of the lung

Two hundred and twenty-eight patients who were treated for carcinoma of the lung were followed and their plasma CEA levels assessed at intervals during the course of the disease. In addition, plasma samples were taken from 487 healthy blood donors for comparison as a control. CEA assay is not selective or specific enough, at this time, to be used for screening purposes even though 68% of the patients who have lung cancer will have an elevated concentration of CEA regardless of the histological cell type. In patients with plasma levels of CEA above 15 ng/ml the prognosis is uniformly poor. CEA in the author's view does have value as a prognostic marker capable of suggesting the successful resection of a tumor and to a lesser degree confirming the clinical objective response to the radiotherapy or chemotherapy. It was found that the presence of CEA was not necessarily related to the volume of the tumor or the site of organ metastasis, but reflects the metabolic properties and characteristics of the individual tumor as it occurs in the patient.

CEA levels in patients with colorectal polyps

Preoperative plasma CEA levels were measured in 93 selected patients with histologically defined colorectal adenomata removed at fibroptic colonoscopy in order to determine whether CEA levels are elevated in patients with colonic polyps, or vary with different histologic patterns. None of the patients had inflammatory bowel disease, previous history of carcinoma, or evidence of liver disease. Fifteen percent of the patients had elevated CEA levels (greater than or equal to 2.5 ng/ml; Hansen method), and two-thirds of these were between 2.5 and 4.0 ng/ml. Increased association of elevated CEA levels was noted with old age, villous adenomas (2- to 4-fold), and increased tumor size (greater than 2.3-cm diameter; 2-fold), but not with foci of dysplasia or carcinoma in situ as such. One-half (7/14) of the patients with elevated CEA levels showed the following: two patients had villous tumors with carcinoma in situ, one had a villous adenoma, two had mixed villous and tubular adenomas (with a high proportion of villous pattern), and two were subsequently shown to have carcinoma elsewhere in the colon. It is uncertain that the polyps were the source of the elevated circulating CEA levels; other factors including smoking and patient selection need to be considered. This preliminary study suggests that patients with colorectal adenomata and elevated circulating CEA may be at higher risk for the development of carcinoma. Further follow-up studies of the malignant potential of the polyp-bearing colon are essential.

The present status of DEA in diagnosis, prognosis, and evaluation of therapy

Despite nonspecificity for the diagnosis of colon cancer, the assays for CEA widely studied to date may be useful in the management of patients with colorectal cancer by aiding detection of colonic cancer and especially of widespread metastases to the liver. Use of serial quantitative measurements may also be useful in determining persistence of residual or metastatic tumor after apparently complete surgical resection, in enabling detection of recurrence at an earlier stage than may be otherwise possible, and in helping to evaluate the effects of chemotherapy, provided that the assays are used only in context with complete clinical and laboratory findings, including cancer staging, histopathologic findings, assessment of liver status, and with appreciation of methodologic complexities. Both the further investigation of the clinical use of CEA and the intensified search for more specific markers are encouraged by the findings to date.

A technical improvement in the radioimmunoassay of cyclic-AMP

An improvement in the technique for the radioimmunoassay of cyclic-AMP, wherein ammonium sulfate precipitation is replaced with zirconyl phosphate gel, is presented. This substitution produces a more stable pellet than that obtained with ammonium sulfate. This greatly reduces a potential source of error due to pellet instability.

Carcinoembryonic antigen: evidence for multiple antigenic determinants and isoantigens

Carcinoembryonic antigen (CEA) preparations, from various sources were compared by radioimmunoassay. The preparations studied included four CEA standards (CEA-Roch, CEA-Montreal, CEA-City of Hope, and CEA-British) and CEA from serum and liver metastases of a patient with cancer of the colon who had an extremely high concentration of serum CEA (more than 26,000 ng/ml). The data indicate that the CEA-Roche standard differs significantly from the other three CEA standards tested, and that the serum CEA from the patient was antigenically different from currently available CEA standards as well as from the CEA obtained from the patient's own liver metastases. These antigenic differences were reflected in radioimmunoassay inhibition curves that were different and that were not affected by perchloric acid extraction of CEA. Because of the antigenic variation in the serum CEA, markedly different CEA concentrations (varying by three orders of magnitude) were measurable by two different antisera (Roche and Montreal). All the various CEA standards and samples cochromatographed on columns of Sepharose-6B, despite the large antigenic variation. We postulate that CEA consists of a family of "isoantigens" with multiple antigenic determinants. We identified a serum CEA isoantigen that was different from the currently available standards. Consequently, we believe that results of radioimmunoassays currently used for CEA measurement may not represent absolute concentrations of serum "CEA", but may reflect the binding affinity of different isoantigens to a particular polyvalent CEA antiserum.

Measurement of urinary CEA-like substance. An aid in management of patients with bladder carcinoma

Urine and serum samples from patients with bladder carcinomas were studied for the occurrence of and variations in CEA content before, during, and after radiation therapy. The concentration of CEA-like substances in urine increased with a more advanced clinical stage of the tumor, although there were large intercase variations. In serum, slightly increased values were noted only in advanced cases. During radiation therapy, high CEA values were found at around mid-course. This could be related to a breakdown of tumor tissue. Judging from data for urine from radiation-treated prostatic carcinomas without known tumors in the bladder, radiation alone was not responsible for the elevation of CEA. Urinary infections contributed to raised levels of CEA-like substances in some cases. At the end of successful radiation therapy (as verified by cystoscopy, cytology, and clinical examination), 25 patients had CEA values in the urine comparable to normal values (14 +/- 7 ng CEA/ml). The decrease was significant from the initial values to those after radiotherapy (p less than 0.01). Four patients whose tumors persisted had high values (68 +/- 46 ng CEA/ml). In patients who had previously received radiation treatment for bladder carcinomas, CEA values were high in 20 with recurrences (58 +/- 36 ng CEA/ml) while they were lower in 13 who were free of recurrence (14 +/- 6 ng CEA/ml). These findings indicate that urinary CEA determinations may be used in the immediate followup and management of patients treated for bladder carcinoma. It also appears to be of prognostic significance.

Plasma levels of carcinoembryonic antigen in bronchial carcinoma and chronic bronchitis

The plasma levels of carcinoembryonic antigen were increased in 80% of 49 patients with bronchial carcinoma and in 68% of 25 patients with an acute exacerbation of chronic bronchitis. There was no statistically significant difference between the two groups. A single determination of the plasma carcinoembryonic antigen level has no prognostic value in patients with bronchial carcinoma.

First British standard for carcinoembryonic antigen (CEA)

In 1974, the National Institute for Biological Standards and Control (NIBSC) established the first British Standard for carcinoembryonic antigen (CEA) for use in comparative quantitative assays. The Standard, which was prepared for material processed by the Chester Beatty Research Institute, is in the form of a freeze-dried powder, sealed in all glass ampoules code labelled 73/601 and containing pure dry nitrogen. For practical purposes, each ampoule contains 100 units of CEA activity.

Carcinoembryonic antigen in an unselected elderly population: a four year follow up

Sera obtained in 1969 from 956 unselected elderly persons in Busselton, Western Australia were tested for carcinoembryonic antigen (CEA) by a "double antibody" microradioimmunoassay. Forty-four (4-5%) were positive for CEA (5 ng/ml or greater). Review of health records for the 4-year period subsequent to accession of sera showed that 6 (14%) of the 44 persons positive for CEA died of CEA associated cancers, 15 were heavy smokers, 2 had colonic diverticula and 1 a peptic ulcer. On the other hand, 18 (2%) of the 912 persons negative for CEA developed CEA associated cancers. Thus, a significantly greater proportion of cancers (P = 0-01) was found in the persons positive for CEA. Furthermore, when 21 persons who were positive for CEA in 1969, but clinically well 4 years later, were examined 2 had occult cancer of lung and colon respectively. However, the relatively low yield of diagnosis of cancer from our present population survey led to the conclusion that, if screening for cancer were to be solely dependent on testing for CEA, increased specificity and sensitivity of test systems should be awaited.

Association of an isomeric species of carcinoembryonic antigen with neoplasia of the gastrointestinal tract

We studied the association between serum levels of an isomeric species of carcinoembryonic antigen and neoplasia of the gastrointestinal tract in 993 patients. With use of an empirically determined threshold, the antigen was found to be elevated in 80.4 per cent of 138 patients with neof other tumors, predominantly lung and breast tumors. Serum levels were elevated in 0.23 per cent of random patients and 0.41 per cent of 725 patients without neoplasia, including those with liver diseases, inflammatory bowel disease and chronic renal disease. The results of this study suggest that this species of carcinoembryonic antigen, and that assay for it offers an improved approach to the diagnosis and management of neoplasia of the gastroinetestinal tract.

Soluble tumour-specific antigen and its relationship to tumour growth

Hooded rats bearing a syngeneic methylcholanthrene-induced tumour were evaluated for extent of in vivo host immunity and this was correlated by in vitro techniques with the levels of circulating tumour antigen and specific antibody. Early tumour growth was associated with detectable immunity, as measured by the capacity of the animal to reject a second direct challenge of the same tumour at a remote site. Radioimmunoassay for circulating tumour antigen and indirect membrane immunofluorescence for antitumour antibody did not detect either component at this stage. Animals with advanced tumours lost immunity as detected by direct tumour challenge, and this closely coincided with the appearance of rising levels of circulating soluble tumour antigen. Although the host possessed the immunologic ability to react against its own neoplasm, this ability was insufficient to produce tumour rejection. Active immunotherapy initiated at the time of, or up to 10 days after, intramuscular challenge with tumour, increased tumour immunity sufficiently for tumour growth to be prevented. Successful immunization was associated with the early appearance (16 days) of measurable levels of antitumour antibody and absence of circulating antigen. It is concluded that soluble tumour antigen present in the local microenvironment of the tumour in the early stages of tumour growth interferes with the ability of immune cells to cause tumour rejection. As the tumour progressively grows, sufficient soluble antigen is produced and released systemically to suppress the effector arm of the host's tumour immune response at distant sites. The levels of circulating soluble tumour antigen attained may be of critical importance in the suppression of rejection responses that prevent metastasis.

Electron microscopy and physical characterization of the carcinoembryonic antigen

Carcinoembryonic antigen (CEA), a glycoprotein material purified from human tumors, has been visualized by electron microscopy. At neutral pH, it consists largely of relatively homogenous, morphologically distinctive twisted rod or cruller shaped particles, with dimensions 9 x 40 nm. The particle length is considerably diminished at pH 40.0, which correlates with a known diminution of charge. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated a molecular weight of 180,000 in the peak region of the CEA band for both 10 and 15% acrylamide. When native CEA was treated with neuraminidase, reduced, and alkylated, a relatively compact random coil was produced, whereas reduction and alkylation without neuraminidase treatment produced a less configuration, as determined by sedimentation studies and by electron microscopy. Electrophoretic migration, however, was apparently unaffected by reduction and alkylation. Thus the characteristic CEA particle appears by several lines of evidence to be substantially folded into a recognizably tertiary structural arrangement.

Isolation and characterization of a homogeneous isomeric species of carcinoembryonic antigen: cea-s

A single homogeneous isomeric species of carcinoembryonic antigen was isolated by reference to solubility in 0.9 M perchloric acid, isoelectric focusing, molecular exclusion chromatography, ion exchange chromatography, passage through immuno-absorbants, and isopyknic density gradient ultracentrifugation. The final product, representing approximately 1.8% of the perchloric acid soluble glycoprotein of the tumor, is homogeneous and devoid of other proteins by polyacrylamide gel electrophoresis. This single species of carcinoembryonic antigen, CEA-S, has a sedimentation velocity of 6.6, a diffusion constant of 3.05 times 10-minus 7 cm-2/sec, a mean Stokes radius of 65 A, a density of 1.41 ml/g in cesium chloride and an estimated molecular weight of 181,000, and it is devoid of detectable A or B blood-group antigens. Immunochemical studies demonstrate qualitative similarities between CEA-S and conventional carcinoembryonic antigens; however, competitive inhibition analyses demonstrate significant quantitative immunochemical differences between CEA-S and preparations of carcinoembryonic antigen. These results are consistent with the concept that CEA-S is an immunochemical isomer of carcinoembryonic antigen.

Carcinoembryonic antigen in patients with gynecologic malignancy

Carcinoembryonic antigen (CEA) was elevated (greater than 2.5 ng/ml) in 81 of 100 patients with gynecologic malignancy and in 17 of 95 patients with benign gynecologic disease. CEA concentration was, in general, related to the extent of disease, and in early stage cancer often returned to normal following complete surgical excision. Tumors were classified morphologically according to cell type, lymphoplasmacytic infiltration, necrosis, vascular invasion, desmoplasia, and degree of differentiation. The only histologic characteristic associated with elevated CEA levels was the presence of vascular invasion. Further investigation is needed to define the structure, function, and metabolism of CEA in patients with gynecologic malignancy.

Carcinoembryonic antigen and alpha fetoprotein in malignant tumors of the female genital tract

Circulating carcinoembryonic antigen (CEA) and alpha fetoprotein (AFP) levels were measured by radioimmunoassay in 53 patients with carcinoma of the ovary, 16 patients with other malignant genital tumors, and 31 women with nonmalignant diseases of the genital tract. The serum CEA concentration was elevated (greater than 5 ng/ml) in 11 patients with ovarian cancer, 2 patients with endometrial cancer, 1 patient with carcinoma of the cervix, and 1 patient with a benign embryonal cystic teratoma. Elevated CEA levels were found only in patients with advanced malignant disease, while early stages were associated with normal CEA concentrations. AFP levels were normal in all but 1 patient. Both CEA and AFP levels were markedly raised in a case of advanced genital carcinoma arising probably from the ovary. Ascitic fluid of another patient with ovarian cancer contained a high concentration of CEA, giving an identical reaction in immunodiffusion with CEA from colon cancer. The present results indicate that while the increased expression of carcinofetal components takes place in some malignant tumors of the female genital tract, it is usually a late phenomenon.

[Carcinofetal antigens. III. Further carcinofetal antigens (author's transl)]

The occurrance and significance of important carcinofetal antigens other than AFP and CEA are reported. These included the alpha 2 H-protein which is produced in the liver and increases in serum of patients with various tumors, the fetal sulphoglycoprotein antigen FSA from the gastric juice of patients with gastric cancer, the carcinoplacental alkaline phosphatase (REGAN-isoenzyme)which is found in the serum of patients suffering from e.g. bronchogenic, mammary, urogenital and gastrointestinal carcinomas, the beta-S-fetoprotein which is most likely to be identical with C-reactive protein, gamma-fetoprotein, the carcinofetal antigen in glial tumors (CFGA); ectopic production of placental hormones like human gonadotropin, placental lactogen, plasminogen-activators; leukemia-associated antigens. Furthermore, some other less known carcinofetal antigens are mentioned.

Carcinoembryonic antigen in patients suffering from ulcerative proctocolitis

Carcinoembryonic antigen (CEA) has been measured by radioimmunoassay in samples obtained from all patients suffering from ulcerative proctocolitis and seen within a four-month period. The characteristics of this group of patients have been compared with reported epidemiological studies in this disease, and have been found to have a similar sex ratio and age of onset, but a more limited disease. Among 59 patients, 11 were found to have elevated circulating CEA values. One of the 11 had a colonic carcinoma and another was pregnant. Excluding these two patients, an overall prevalence of elevated CEA levels of 17.5% was found. The prevelance in ulcerative proctitis was 7.1%, and in colitis was 19.9%. The patients in whom elelvated plasma CEA values were found were compared with the remaining patients in relation to factors known to be associated with an increased propensity for the development of colorectal carcinoma complicating ulcerative colitis. There was no difference in mean age of the patients at disease onset, nor was there any difference in disease duration, extent, and control. A significant correlation was found between elevated plasma CEA levels and the severity of the initial attack. One patient with premalignant changes in the rectal mucosa had consistently normal concentrations of plasma CEA. There was no significant correlation between elevated plasma CEA values and disease activity. The mean age of the two groups of patients was similar. No carcinoma has manifested in any patient during follow-up periods of at least 18 months.

Estimation of carcinoembryonic antigen in ulcerative colitis with special reference to malignant change

The levels of plasma carcinoembryonic antigen (CEA) were estimated in 59 control subjects attending St Mark's Hospital and in 139 patients with uncomplicated ulcerative colitis. There was little difference in the CEA levels in the two groups. In the colitic patients, the actual CEA values could not be correlated with the age of the patient, the activity of the disease, the extent of bowel involvement, or the length of history. In addition, seven colitic patients with severe dysplastic changes in the rectal mucosa and seven patients with established carcinoma in colitis were studied. With one exception in each group, the CEA levels in these patients were within the range shown by the St Mark's Hospital control population.

Nature of the tumor-associated determinant(s) of carcinoembryonic antigen

The carbohydrate moiety of carcinoembryonic antigen could be sequentially degraded by repeated cycles of periodate oxidation, reduction, and mild acid hydrolysis (Smith degradation). After three complete degradations, all fucose and sialic acid, 80% of the galactose, 65% of the mannose, and about 40% of the N-acetylglucosamine were eliminated without impairing the ability of degraded carcinoembryonic antigen to react with specific antisera against the antigen. Inhibition studies in a carcinoembryonic antigen/rabbit anti-carcinoembryonic antigen precipitating system with oligosaccharides covering previously known internal structures of glycoproteins and presumably corresponding to the internal carbohydrate region of the antigen, demonstrated that none of the compounds tested was inhibitory. Nor could any inhibitory effect on the binding of carcinoembryonic antigen to antibody against the antigen in a radioimmunoassay system be domonstrated for the carbohydrate moiety prepared by hydrazinolysis or the glyco peptide fraction isolated after papain degradation of the antigen. However, if carcinoembryonic antigen is completely reduced and alkylated, with three intrachain disulfide bonds cleaved per 10-5 g, the immunological activity is reduced to 3-5% of untreated antigen. Furthermore, treatment of the antigen with 0.5 NaOH at 20 degrees for 2 hr completely abolished its ability to react with antiserum, whereas its ability to precipitate with a series of lectins was unchanged. No release of low-molecular-weight carbohydrate orchange in sugar composition of alkali-treated antigen was observed. Our tentative conclusion is that the carbohydrate moiety of carcinoembryonic antigen does not contain the tumor-associated determinant(s).

Carcinoembryonic antigen: characterization of binding with insoluble lectins

Insoluble conanavalin A and wheat germ agglutinin (WGA) were found to bind to carbohydrates on radio-labelled carcinoembryonic antigen (CEA). Binding by WGA was inhibited both by N-acetyl D-glucosamine and fragments of antibody to CEA, but was increased by intact antibody to CEA. This suggests that WGA binds to exposed N-acetyl D-glucosamine determinants on 125I CEA and also on antibody molecules. It also suggests that 125I CEA contains binding sites for anti-CEA which contain N-acetyl D-glucosamine as well as others which do not. Molecules of 125I CEA which bound to the insoluble lectins were more antigenic for anti-CEA than unbound molecules. These results suggest that the principal antigenic site on CEA contains N-acetyl D-glucosamine and may help to explain the agglutination of tumour cells by lectins.

CEA as a monitor of gastrointestinal malignancy

Ninety-four patients with carcinoma of the colon have been followed with serial determinations of plasma CEA (carcinoembryonic antigen) levels over a 3-year period using the Hansen assay. Nine hundred twelve CEA determinations have been made in these patients. Plasma CEA levels rose in 90% of the instances of clinical progression documented in these patients. In 30% of patients, this rise indicated progression 6 months or more before it was detected by standard clinical methods. Unfortunately, a few patients never developed elevated CEA levels even though disease clearly progressed. False positive results have also been encountered, with significant elevations occurring in patients who have since remained without evidence of disease for several months. Our data indicate that at least two sequential elevated CEA values, the second being higher, must be a minimal criterion for consideration of possible progression of disease. Even with this standard, we have encountered false positive results in 10% of our patients, indicating recurrence or progression where none has occurred clinically. CEA measurement is of limited usefulness for 30 days after curative surgery, because the elevation of CEA levels due to the original amount of tumor present as well as due to surgery per se may persist for this length of time in a significant number of patients. On the other hand, CEA levels have responded to chemotherapy in close correlation with observed clinical course in those patients with metastatic disease treated in this series. Initial pretherapy CEA values have so far proved to be good prognostic indicators of disease course following complete resection. With an initial CEA value of less than 2.5 ng/ml of plasma, recurrent has been rare (1/20). If the pretreatment CEA was greater than 7.0 ng/ml, it has been the rule (7/9).

Urinary carcinoembryonic antigen (CEA)-like molecules and urothelial malignancy: a clinical appraisal

A total of 190 patients being treated or followed up for urothelial carcinoma have been studied by the serial estimation of their urinary and plasma CEA levels. Only 46% of patients with a urothelial neoplasm present have a raised urinary CEA level. Infection or ileal conduit urine vitiate the result as they produce high CEA levels in the urine in the absence of any neoplastic disease. The accuracy of urinary CEA estimations is compared with that of cytology. Plasma CEA levels do not serve as a useful guide to the presence of extra-urinary tract tumour spread if taken as isolated readings. However, serial plasma CEA estimations may indicate that metastatic disease is present several months before its detection by the more usual clinical methods in a minority of patients.

Human tumour-associated and tumour-specific antigens: some concepts in relation to clinical oncology

The concept of tumour-specific antigens is constantly undergoing reappraisal with the development of more sensitive methods for their detection. This has resulted in the finding that the many 'new' antigens produced by human tumours or materials immunologically closely related to them are also present in non-neoplastic tissues, albeit in small amounts. However, other antigens still appear to exist almost entirely in or on tumour cells so that the antigens of human tumours may be subdivided into either tumour-associated macromolecules or tumour-specific antigens. The elucidation of the chemical nature of the tumour-specific antigens may result in important advances in cancer diagnosis and therapy. As many are organ specific, it should be possible to evolve test systems which will enable tumours to be diagnosed and located before they become apparent clinically. On the other hand the tumour-associated macromolecules, of which the oncofetal antigens are the principal examples, are found in elevated amounts in some non-neoplastic disorders. It is now clear that serial estimation of the levels of these macromolecules is of considerably more diagnostic value than single random measurements. Current work is establishing their value in the detection of recurrent and metastatic tumours before they become apparent by other methods, which is probably their most important role, and also their value as aids to monitor therapeutic efficacy. The future use of both types of antigen may unfold a new era in cancer detection and therapy but many basic chemical and immunological studies are needed before their clinical use can be fully defined.

[Immunochemical identification of carcinoembryonic antigen in ovarian adenocarcinoma and pseudomucinous cystoma extracts]

Carcinoembryonic antigen (CEA) was found in 3 of 17 individual extracts of adenocarcinoma and in 7 or 8 individual samples of pseudomucinous cystoma of the human ovaries. Rabbits were immunized for the purpose of preparation of specific antisera against CEA by individual fractions (ammonium sulfate, sulfosalicylic acid and phosphotungstic acid) of CEA-positive adenocarcinomas of the ovary.