Collaborative study of bronchial tumour-associated antigens

Eleven groups of workers submitted a total of 21 bronchial tumour-associated antigen preparations and 19 antisera for comparative studies. Many of the antisera proved to be polyspecific despite absorption procedures. Most of the antigen preparations contained some material reactive towards a reference antiserum to normal human serum proteins. While it appeared that no participants were studying identical antigen-antibody reactions, several cross-reactivities were identified in the antisera. When immune reactions to CEA, AFP, NCA, ferritin, lactoferrin, human pepsin and gastricsin, and the pregnancy proteins, SP1 and SP3 were excluded by use of reference antisera and electroimmunoprecipitation methods, there remained 5 antigen-antibody reactions defining unique antigens. The clinical usefulness of any of these 5 antigens has yet to be determined.

Monoclonal antibodies to carcinoembryonic antigen produced by somatic cell fusion

Hybridoma cell lines secreting monoclonal antibodies to carcinoembryonic antigen (CEA) were generated by fusing mouse immune lymphocytes with the mouse myeloma variant cell line, NS-1. Antibody secreted by one cloned hybrid cell line could bind only a select portion of the CEA bound by the commercially available goat anti-CEA antiserum used in clinical assays. Radiolabeled CEA could be purified on a monoclonal antibody affinity column. Incorporation of this purified radiolabeled CEA in a double-antibody solid-phase assay with goat anti-CEA antiserum led to an approximately 2.5-fold increase in sensitivity of the assay. Genetically stable hybrid clones may be sources of virtually unlimited quantities of such antibodies which may have potential utility in improving the cancer specificity of clinical assays.

Application of monoclonal antibodies to purified CEA in clinical radioimmunoassay of human serum

Double-antibody radioimmunoassay using a mouse monoclonal anti-CEA (MA/1) has been used to measure CEA in human serum. Low levels of MA/1-binding CEA have been found in serum from normal individuals and moderately raised levels are sometimes associated with certain non-malignant diseases. As with conventional anti-CEA, the MA/1 antibodies can recognize significant amounts of CEA in serum from patients with a variety of solid tumours. However they appear to recognize a different immunodeterminant and possibly a different population of CEA molecules to, or a subset of, those measured by two routine assays. Studies in which the MA/1 assay was directly compared with the results of the Charing Cross routine and Abbott EIA assays have indicated that different immunological forms of CEA may be expressed in the course of tumour progression but no prognostic value was evident in this study. Our results stress the need to resolve immunological specificities expressed by CEA-like molecules and evaluate their clinical importance.

Preparation and specificities of antisera to the amino-terminal sequence of the carcinoembryonic antigen

A tetracosapeptide (peptide-24) corresponding to the amino-terminal sequence of the carcinoembryonic antigen (CEA) was synthesized and characterized. Antisera were produced to the peptide-24, and a radioimmunoassay was developed utilizing peptide-24 with a tyrosine residue on the amino-terminal end (Tyr-peptide-24). Inhibitions of anti-peptide-24-125I-Tyr-peptide-24 complex formation were done with several preparations of CEA and the normal cross-reacting antigen. The extent of cross-reactivities was low, one CEA preparation requiring a 250-fold molar quantity greater than peptide-24 to obtain the same degree of inhibition. Attempts to degrade the CEAs and normal cross-reacting antigens in order to possibly expose the amino-terminal ends for reactivity with antibody did not result in any great increase in inhibitory capacity. It was concluded that either the conformations of the antigenic determinant(s) of the peptide-24 and of the amino-terminal end of CEA were sufficiently different to result in little cross-reacting antigen are blocked for reactivity with antibody by other portions of the molecule.

The antigenicity and immunology of human cervical squamous cell carcinoma: a review

Numerous studies have demonstrated an altered antigenicity in the carcinomatous cervix. Whether the neoplasia-associated antigens are of viral origin, are actually normal antigens expressed in elevated levels, or are true tumor-associated antigens has not been precisely determined, since evidence has been presented for all of these possibilities. These antigens associated with cervical squamous cell carcinoma have been demonstrated not only biochemically and by raising antisera to the tumors in animals but also by studies of the humoral and cell-mediated immune responses of cervical cancer patients. Immunodiagnosis of cervical cancer with the use of these antigens has, to date, not been feasible, although several of the assays appear potentially useful.

Localization of human breast-carcinoma xenografts using antibodies to carcinoembryonic antigen

Affinity-purified antibodies to carcinoembryonic antigen (CEA) have been injected into immune-suppressed mice bearing xenografts of human breast tumours. It has been shown that the antibodies localized in the tumours but not in normal tissues. The degree of tumour localization correlates with the amount of tumour CEA, and is unaffected by levels of circulating CEA or CEA/anti-CEA immune complexes.

Demonstration of elevated anti-Lewis antibodies in sera of cancer patients using a carcinoembryonic antigen-polyethylene glycol immunoassay

The serum levels of carcinoembryonic antigen (CEA) and CEA-binding proteins of 68 controls and 170 cancer patients were determined. The CEA levels were determined by a double-antibody radioimmunoassay using radiolabeled CEA, and the CEA-binding proteins were determined by an immunoassay utilizing radiolabeled CEA and polyethylene glycol. The major CEA-binding proteins in serum were anti-blood group antibodies as demonstrated by differential binding of serum proteins from A, B, or O positive individuals to radiolabeled CEA's which were previously shown to carry specific blood group determinants. No statistically significant differences were observed for the binding of control versus cancer patient sera to CEA-A (carrying blood group A1), except, as expected, A negative (O or B positive) individuals gave high binding to CEA-A, while A positive individuals gave low binding to CEA-A. Statistically significant differences were observed for controls versus cancer patients for binding to CEA-Lewisab (CEA-Leab). CEA-Leab-binding activity was higher in females and smokers in the control group, but this distinction was not found in the cancer patients. The high levels of anti-Leab antibodies may be explained in females by exposure to fetal antigens during pregnancies and in smokers or cancer patients by exposure to precursors to blood group substances. The sera of 7% of the patients with colonic carcinoma, 18% of the patients with breast carcinoma, and 23% of the patients with bronchogenic carcinoma bound more CEA-Leab than did the serum of the highest male control. A correlation between CEA-Leab-binding activity and the levels of serum CEA was found for patients with colonic carcinoma but was not significant for the groups with other cancers or the control group. Serial determinations of CEA-Leab-binding activity for 21 patients with bronchogenic carcinoma changed congruently with the serum levels of CEA in 12 cases. The significance of these results in terms of expression of immature blood group antigens, the subsequent production of antibodies against them, and the prognostic value of this response is discussed.

Sensitive detection of carbohydrate determinants on carcinoembryonic antigen preparations by lectin and antibody binding using polyethylene glycol

Blood group determinants have been found in five carcinoembryonic antigen (CEA) preparations with a lectin and antibody-binding assay using polyethylene glycol 6000 to separate free from bound radiolabeled antigen. The assay described gives excellent sensitivity for the binding or inhibition of binding of various lectins or antibodies to CEA. One of the CEA preparations investigated has an A1 determinant, another has a B determinant, and all have H, Lea, Leb, and MN blood group determinants. In addition, all of the preparations tested bound concanavalin A. These findings are consistent with the idea that incomplete or unexpected glycosylation patterns occur in glycoproteins produced by tumor cells. Since antibodies directed against blood group substances cross react with carbohydrate determinants on CEA, clinical determinations of CEA or anti-CEA levels in serum may be adversely affected.

Surface membrane glycoproteins of cultured human pancreatic cancer cells

The cell-surface glycoproteins and proteins of four human pancreatic cell lines (MIA PaCa-2, PANC-1, HS766T, and CAPAN-1) were separately tritiated using galactose oxidase/NaB(3H)4 and iodinated using lactoperoxidase/125I. Gel electrophoresis showed that the cell lines had very different surface components. All four cell lines were tested for cell-surface antigens that cross-reacted with antisera raised against carcinoembryonic antigen and against the membrane fractions of MIA Pa Ca-2 and CAPAN-1 cells. CAPAN-1 cells reacted most strongly with all three antisera. Seventeen cell-surface proteins can be detected when CAPAN-1 cells are labeled using lactoperoxidase. The labeled membranes were solubilized in detergent and subjected to affinity chromatography on Sepharose-conjugated lectins. The bound proteins were eluted and analyzed on gel electrophoresis . All 17 proteins capable of being labeled by lactoperoxidase bound to at least one lectin column, indicating they are all glycoproteins.

Hyperthermia enhancement of antibody-complement cytotoxicity for human colon tumor cells

HCT-8R human colon tumor cells heated for 60 minutes at 37-44.5 degrees C showed an increased sensitivity to lysis by rabbit anti-HCT-8R antibodies and complement (Ab-C) at the higher temperatures. As compared to the 51Cr release assay, the colony formation (CF) assay was a more sensitive measure of hyperthermia-induced cell damage and sensitization to Ab-C lysis. Also the CF assay was more efficient than the 51Cr assay in detecting effects of low-temperature heating (41.5 degrees C) on Ab-C cytotoxicity. The direct toxicity of heating alone was minimal. Because heating did not influence the pH of the medium, the pH of our assay system did not appear to be factor in the enhanced sensitivity of heated cells to Ab-C cytotoxicity. Significantly smaller amounts of antibodies were capable of lysing heated cells as compared to unheated cells, but heated cells did not bind more antibodies than did unheated cells. This suggests that the hyperthermia effect on the cell occurs at some stage of the lytic event after antibody binding. Hyperthermia treatment at 43.5 degrees C enhanced cytotoxicity by antibodies monospecific to carcinoembryonic antigen, which is expressed on the surface of these cells. Thus hyperthermia may be an effective tool in augmenting specific immune reactions against tumor-associated cell membrane antigens.

Experimental studies of tumor radioimmunodetection using antibody mixtures against carcinoembryonic antigen (CEA) and colon-specific antigen-p (CSAp)

Experiments with the GW-39 human colonic carcinoma growing in hamsters showed that injection of radioactive antibody to a colorectal-specific, tumor-associated antigen, CSAp, results in better tumor radiolocalization than was seen previously with radioantibodies to carcinoembryonic antigen (CEA). However, a mixture of both radioactive antibodies resulted in potentiation of CEA-tumor radioimmunodetection without affecting CSAp-tumor radiolocalization. Hence, multi-marker antibody mixtures may be the method of choice in cancer radioimmunodetection.

Somatic-cell hybrids producing antibodies against CEA

Monoclonal antibodies to carcinoembryonic antigen (CEA) promise improved specificity for the measurement of this widely expressed human cancer antigen. A mouse monoclonal antibody binds weakly to CEA in perchloric acid extracts of tumour but strongly to CEA similarly isolated from serum, and its spectrum of cancer detection differs from conventional antisera.

Preliminary therapeutic and localization studies with human chorionic gonadotrophin

Studies in both patients and mice have been carried out using heterologous antibody directed at secreted products of tumors. In preliminary therapeutic studies in patients with drug-resistant choriocarcinoma and malignant teratoma, heterologous anti-human chorionic gonadotrophin (HCG) and anti-alpha-fetoprotein have been combined with continued cytotoxic chemotherapy. The results to date, although interesting, are inconclusive. In nude mice, anti-HCG administration at the time of inoculation with choriocarcinoma cells failed to inhibit tumor growth. 131I-Labeled anti-HCG and anti-carcinoembryonic antigen have been used in localization studies. Specific:nonspecific ratios of up to 2:1 were obtained in human and murine studies with HCG- and carcinoembryonic antigen-producing tumors.

Historical development and potential uses of tumor antigens as markers of human cancer growth

During the past 30 years, the rapidly developing and changing concepts and technology of the discipline of immunobiology have been applied to studies in oncology. After the definitive demonstration of so-called tumor-specific transplantation antigens in chemically and virally induced tumors in syngeneic rodent and murine species, numerous efforts were then directed toward the demonstration of comparable materials in human tumors. After a number of false starts in an overzealous search for a marker that would serve as a panacea for human cancer diagnosis, more rational approaches have been taken to the problem and valuable information from the points of view of both the cell biologist and clinical oncologist has been forthcoming. The present paper presents an overview of human tumor antigens as biological markers of tumor growth. Reference is made to the fact that normally occurring biological materials of known function that are qualitatively and/or quantitatively altered during the process of malignant transformation may be most useful in the diagnosis and management of the cancer patient. The role of the presently available radioimmunoassays for carcinoembryonic antigen in clinical medicine is outlined.

Use of limitations of radiolabeled anti-CEA antibodies and their fragments for photoscanning detection of human colorectal carcinomas

Fifty-three patients with histologically proven carcinoma were injected with highly purified [131I]-labeled goat antibodies or fragments of antibodies against carcinoembryonic antigen (CEA). Each patient was tested by external photoscanning 4, 24, 36 and 48 h after injection. In 22 patients (16 of 38 injected with intact antibodies, 5 of 13 with F(ab')2 fragments and 1 of 2 with Fab' fragments), an increased concentration of 131I radioactivity corresponding to the previously known tumor location was detected by photoscanning 36-48 h after injection. Blood pool and secreted radioactivity was determined in all patients by injecting 15 min before scanning, [99mTc]-labeled normal serum albumin and free 99mTc04-. The computerized subtraction of 99mTc from 131I radioactivity enhanced the definition of tumor localization in the 22 positive patients. However, in spite of the computerized subtraction, interpretation of the scans remained doubtful for 12 patients and was entirely negative for 19 additional patients. In order to provide a more objective evaluation for the specificity of the tumor localization of antibodies, 14 patients scheduled for tumor resection were injected simultaneously with [131I]-labeled antibodies or fragments and with [125I]-labeled normal goat IgG or fragments. After surgery, the radioactivity of the two isotopes present either in tumor or adjacent normal tissues was measured in a dual channel scintillation counter. The results showed that the antibodies or their fragments were 2-4 times more concentrated in the tumor than in the normal tissues. In addition, it was shown that the injected antibodies formed immune complexes with circulating CEA and that the amount of immune complexes detectable in serum was roughly proportional to the level of circulating CEA.

Radioimmunodetection of gastrointestinal neoplasms with antibodies to carcinoembryonic antigen

Primary and secondary gastrointestinal tumors have been identified using sheep immunoglobulin G antibody to carcinoembryonic antigen radiolabeled with 131I. 99mTc-pertechnetate and 99mTc-human serum albumin were used to identify tissue spaces and blood pool and to facilitate external substraction imaging. In 13 patients with tumors, 4 of 5 primary sites and 8 of 11 secondary sites were successfully demonstrated. Two patients with benign disease had negative scans. Comparison with conventional methods of scanning showed good correlation.

Lymphoscintigraphy with radionuclide-labeled antibodies to carcinoembryonic antigen

Upper- and lower-extremity lymphoscintigraphy was performed on 50 patients with proven carcinoma of the breast, gastrointestinal system, genitourinary tract, lung, and vulva; 42 patients had 131I-antibodies to carcinoembryonic antigen (CEA) and 8 patients had 131I-normal goat immunoglobulin G. All metastases in the axillary or inguinal lymph nodes were detected with the CEA antibodies. In nine patients without metastases, radioactivity was observed in inguinal or axillary nodes. It is postulated that the nodal sequestration of antibody in the absence of metastatic carcinoma is due to captured CEA in lymph nodes draining the tumor site. This study has demonstrated the high sensitivity for detecting nodal metastases by labeled antibodies to CEA draining from primary or recurrent tumors.

Radiolabeling of affinity-purified goat anti-carcinoembryonic antigen immunoglobulin G with technetium-99m

Affinity-purified goat anti-carcinoembryonic antigen immunoglobulin G was labeled with 99mTc, utilizing stannous tartrate as the reducing agent. The radiochemical yield of labeled antibody ranged from 18 to 37% and was inversely proportional to the initial quantity of pertechnetate ion used. Yields up to 60% could be obtained using small amounts of pertechnetate. The 99mTc-labeled anti-carcinoembryonic antigen immunoglobulin G preparations had a specific activity range of 1 to 6 microCi/microgram protein and had 60% or greater immunoreactivity. Human serum albumin and goat immunoglobulin G were used as model systems to evaluate labeling parameters and analytical methods.

Use of isotopic immunoglobulin in therapy

Antibodies raised in heterologous species against tumor-associated antigens such as ferritin and carcinoembryonic antigen may be utilized in diagnostic scanning and in cancer therapy. The radiolabeled (131I) antibodies have a mean effective half-life of 3 days. The tumor-bearing regions retain activity which was associated with objective evidence of remission in primary hepatic cancers. Major organ toxicity was not apparent in eight of nine patients treated with radioactive antibody. Objective evidence of clinical remission was documented by computer-assisted axial tomography scan remission in sequential studies that determine residual tumor in the same planar cuts. Future possible improvements in radioimmunoglobulin are discussed in light of the clinical findings.

Are circulating CEA immune complexes a prognostic marker in patients with carcinoma of the gastrointestinal tract?

CEA immune complexes and free CEA were determined to 363 patients with histologically confirmed adenocarcinoma of the gastrointestinal tract before surgery and in a post-operative follow-up. Circulating CEA immune complexes (CEA-IC) could be detected preoperatively in 89 patients. Incidence of CEA-IC increased with increasing tumour extension; 72/89 patients with CEA-IC showed already metastatic disease progression, 40/89 had nonresectable tumours. Patients with preoperative CEA-IC had a poorer prognosis than patients without CEA-IC but with high levels of free CEA, or CEA-negative patients. The appearance of CEA-IC with consecutive increases in the postoperative follow-up indicated disease recurrence. In 32/55 relapse cases, circulating CEA-IC were detected postoperatively, all 32 cases developing metastatic spread of disease.

Purification of tumor-associated embryonic substance from mouse ascites tumor cells: its cross-reactivity with human CEA

1. Tumor-associated embryonic substance (TAES), which was detected on MM2 cells by cell agglutination method using MM2-regressor mouse serum, was purified from MM2 cells to gel electrophoretically pure substance. The recovery was 0.9 mg (protein) from 100 g (wet weight) cells. TAES is a glycoprotein of 21S. 2. TAES inhibited cross-agglutination of MM2 cells by various syngeneic regressor serum, tumor-bearer serum or pregnant mouse serum. 3. From agglutination inhibition experiment, it was concluded that TAES and human CEA have a common binding site for the agglutination factor. 4. The binding site contains saccharide moiety of these molecules with N-acetyl glucosamine at the non-reducing terminus. 5. Although TAES and CEA cross-reacted in agglutination-inhibition experiments, their antigenicity to xenogeneic animal did not show cross-reactivity.

Ampullary carcinoma associated with multiple duodenal villous adenomas

A 39-year old Asian with multiple duodenal villous adenomas and an adenocarcinoma arising from one of these tumors is described. The rarity of villous adenomas at this site is stressed and their tendency to undergo malignant change reviewed. Immunoperoxidase studies using carcinoembryonic antigen (CEA) antiserum were positive in high dilutions (1 in 8,000) in the carcinoma and the largest adenoma. This stain would appear to show functional malignancy before histological evidence of malignancy is found.

Further characterization of a melanoma-specific protein from human urine

Isolation of a melanoma-specific protein (MSP) from human urine has been achieved using antibody affinity chromatography. MSP migrates as a single homogeneous protein on SDS PAGE and comparison of these data and ultracentrifuge analyses indicates that MSP contains a single polypeptide chain. MSP, however, shows considerable charge heterogeneity on isoelectric focusing. The desialo form, alpha 2 MSP, is found predominantly in patients with advanced metastatic disease, whilst only the sialo form alpha 1 MSP, is obtained from the urine of patients with early-stage disease. MSP does not react with antisera raised to alpha 1 foetoprotein (AFP) or carcinoembryonic antigen (CEA) and hence is immunologically distinct from these other tumour-associated glycoproteins. Antisera raised to MSP do not react with normal skin melanocytes nor with any foetal tissue tested, and hence the origin of MSP remains unresolved.

Diffusion control of the binding of carcinoembryonic antigen (CEA) with insoluble anti-CEA antibody

Analysis of the kinetics of CEA binding to rabbit anti-CEA antibody insolubilized on filter paper discs provided six lines of evidence indicating diffusion control of this reaction: 1) The observed forward rate constant, k1obs, decreased when solvent viscosity was increased with sucrose or Ficoll. 2) k1obs per receptor site increased from 1.2 x 10(4) M-1 sec-1 to 2.6 x 10(4) M-1 sec-1 as receptor site density on immunosorbent discs decreased from 5.2 x 10(-13) to 2.1 x 10(-13) moles/disc. 3) Stirring the reacting mixture of CEA and insoluble anti-CEA increased k1obs from 1.2 x 10(4) M-1 sec-1 to 3.4 x 10(4) M-1 sec-1. 4) The activation energy for CEA-insoluble anti-CEA binding was indistinguishable (p greater than 0.1 by t-test) from 4.1 Kcal/mole expected for diffusion controlled reactions. 5) Bimolecular reaction theory predicted a diffusion limited forward rate constant, k1max, for CEA binding to insoluble anti-CEA, which was consistent with our observed k1 of 1.2 x 10(4) M-1 sec-1. 6) k1obs for CEA binding to soluble rabbit anti-CEA antibody was 6.4 x 10(4) M-1 sec-1, 5 times faster than the k1obs of the heterogeneous phase reaction for receptor site density of 5.2 x 10(-13) moles/disc. Diffusion control of ligand binding to insoluble receptors, as exemplified by the CEA-insoluble anti-CEA model system, may be a very general biologic phenomenon.

Neo-antigenic expression in rheumatoid synovia?

CEA-like activity was found in eight synovial samples of ten rheumatoid patients and in two samples of patients with recurrent arthrosynovitis. No CEA-like activity was found instead in seven synovial samples of patients with gonarthrosis. The plasmatic values result always within normal range in the non-rheumatoid patients and high only in two cases of rheumatoid ones. Since enzymatic proteolysis induces a synovial CEA-like activity fall, the A.A. think that the antigenic determinants belong to a "protein" locally synthesized.

Radioimmunodetection of colorectal cancer

This study examines the accuracy of colorectal cancer radioimmunodetection. Twenty-seven patients with a history of histologically-confirmed colonic or rectal carcinoma received a high-titer, purified goat anti-CEA IgG labelled with 131-I at a total dose of at least 1.0 muCi. Various body views were scanned at 24 and 48 hours after administration of the radioantibody. Three additional cases were evaluated; one had a villous adenoma in the rectum and received the 131-I-labelled anti-CEA IgG, while two colonic carcinoma patients received normal goat IgG labelled with 131-I. All of the 7 cases with primary colorectal cancer showed true-positive tumor localization, while 20 of 25 sites of metastatic colorectal cancer detected by immune scintigraphy were corroborated by other detection measures. The sensitivity of the radioimmunodetection of colorectal cancers (primary and metastatic) was found to be 90% (true-positive rate), the putative specificity (true-negative rate) was 94%, and the appraent overall accuracy of the technique was 93%. Neither the case of a villous adenoma receiving the anti-CEA IgG nor the two cases of colonic cancer receiving normal goat IgG showed tumor radiolocalization. Very high circulating CEA titers did not appear to hinder successful tumor radiolocalization. These findings suggest that in colorectal cancers the method of CEA radioimmunodetection may be of value in preoperatively determining the location and extent of disease, in assessing possible recurrence or spread postoperatively, and in localizing the source of CEA production in patients with rising or elevated CEA titers. An ancilliary benefit could be a more tumor-specific detection test for confirming the findings of other, more conventional diagnostic measures.

[Prognostic value of circulating immune complexes of carcinoembryonic antigen (CEA) in patients with adenocarcinoma of the gastrointestinal tract (author's transl)]

CEA immune complexes and unbound CEA were preoperatively determined in 350 patients with histologically confirmed adenocarcinoma of the gastrointestinal tract. Circulating CEA immune complexes could be detected in 86 patients (25%) where an increase of tumor extension according to TNM classification was concomitant with an increasing percentage of patients with CEA immune complexes. 74/86 patients showed simultaneously pathological concentrations of unbound CEA. During postoperative surveillance the determinations of circulating CEA immune complexes could be used as prognostic criteria. In 30/50 patients with recurrent cancer CEA immune complexes were detected latest at the time of clinical diagnosis. Appearance of CEA immune complexes might contribute to characterization of the immune status of the patients. Some of the patients with widespread tumors exhibited a rapid increase of CEA immune complexes a few months before exitus (44% of the patients). Before exitus 13% of the patients again showed a greatly decreased concentration of CEA-immune complexes.

Direct tissue visualization of normal cross-reacting antigen in neoplastic granulocytes

Normal cross-reacting antigen, a glycoprotein that shares some antigenic determinants with carcinoembryonic antigen, was consistently demonstrated by tissue immunoperoxidase staining in the cytoplasm of both non-neoplastic and neoplastic neutrophilic granulocytes. It was absent in lymphoid cells, but occasional cells of the macrophage/histiocyte series showed variable staining. Malignant cells from patients who had non-Hodgkin or Hodgkin lymphomas were negative for normal cross-reacting antigen. These findings were in contrast to the findings of specific normal cross-reacting antigen positivity in neoplastic granulocytes from three patients who had acute granulocytic leukemia, three who had chronic granulocytic leukemia, and one who had a granulocytic sarcoma. Similar normal cross-reacting antigen positivity was also seen in granulocytes from two patients who had granulocyte dysplasia. It is suggested that direct tissue visualization of normal cross-reacting antigen using immunoperoxidase technics may be of value in the classification and diagnosis of hematologic malignancies, and may provide an additional marker for cells of the granulocytic series.

Detection of new cross-reacting carcinoembryonic antigen(s) on cultured tumor cells by mixed hemadsorption assay

Antisera highly specific for carcinoembryonic antigen (CEA) from New Zealand White rabbits and a goat reacted strongly in antibody binding tests with cultured tumor cell lines, irrespective of the ability of the cell lines to produce CEA. The most reactive were colon carcinoma and melanoma cell lines, the former known to produce CEA and the latter not associated with CEA production. The reactivity was not diminished by absorption with perchloric acid extracts of normal lung or spleen, whereas absoprtion with purified CEA preparations abolished the reactivity. Quantitative absorption studies indicated that reactivity against CEA-producing cell lines could be totally removed by absorption with other CEA-producing lines but not with melanoma cell lines. Reactivity against melanoma cell lines could be completely removed by colon carcinoma cells as well as by melanoma cells. Antisera raised against purified CEA, after absorption with extracts of normal lung, still contained two populations of antibodies, one that binds a newly described antigen cross-reacting with CEA which is present on melanoma cells.

Another oncofoetal antigen in colonic carcinoma

Images