Monoclonal antibody CC3C195, which detects cancer-associated antigens in serum, binds to the human Lea blood group antigen and to its sialylated derivative

Alterations in glycosylation as biomarkers for cancer detection

Glycoconjugates constitute a major class of biomolecules which include glycoproteins, glycosphingolipids and proteoglycans. Glycans are involved in several physiological and pathological conditions, such as host-pathogen interactions, cell differentiation, migration, tumour invasion and metastisation, cell trafficking and signalling. Cancer is associated with glycosylation alterations in glycoproteins and glycolipids. This review describes various aspects of protein glycosylation with the focus on alterations associated with human cancer. The application of these glycosylation modifications as biomarkers for cancer detection in tumour tissues and serological assays is summarised.

Serum tumor markers in pancreatic cancer-recent discoveries

The low prevalence of pancreatic cancer remains an obstacle to the development of effective screening tools in an asymptomatic population. However, development of effective serologic markers still offers the potential for improvement of diagnostic capabilities, especially for subpopulations of patients with high risk for pancreatic cancer. The accurate identification of patients with pancreatic cancer and the exclusion of disease in those with benign disorders remain important goals. While clinical experience largely dismissed many candidate markers as useful markers of pancreatic cancer, CA19-9 continues to show promise. The present review highlights the development and the properties of different tumor markers in pancreatic cancer and their impact on the diagnostic and treatment of this aggressive disease.

Comparative evaluation of serum CA 195 and carcinoembryonic antigen in metastatic carcinoma

BACKGROUND

Carcinoembryonic antigen (CEA) is a well-described human tumor-associated antigen most useful clinically in colon cancer. However, the clinical usefulness of CEA is limited by the marker's overall poor specificity and low sensitivity in patients with minimal disease. CA 195 is a recently discovered human tumor-associated glycoprotein that can be measured in serum using an immunoradiometric assay. CA 195 is expressed on the membrane of human colon cancer cells and shares an epitope with the Lewis A blood group antigens. The authors initiated a study to compare the clinical utility of serum CA 195 with CEA in patients with advanced cancer. A control population was studied to assess the effects of age, gender, alcohol, and tobacco on the measured levels of serum CA 195.

METHODS

Using a solid-phase two-site immunoradiometric assay, serum CA 195 and CEA levels were measured in 71 control subjects and 167 patients with a prior diagnosis of cancer. The tumor histologic types included breast cancer, 49 patients; colon cancer, 38; prostate cancer, 24; lung cancer, 22; gastrointestinal noncolon cancer, 7; and miscellaneous, 27. Among patients with a history of cancer, 124 (74%) had active metastatic disease, and 43 (26%) were without evidence of active disease. The control population was composed of subjects without a history of malignancy. Clinical data collected from them included age, gender, smoking history, and alcohol consumption.

RESULTS

In this laboratory, the normal ranges established for CA 195 and CEA in the control group were: 0.0-8.3 U/ml and 0.2-4.2 ng/ml, respectively. In the control subjects, the serum CA 195 level, unlike that of CEA, was not affected by age, gender, alcohol consumption, or tobacco use. In the study population, CA 195 had either equivalent or inferior specificity and sensitivity to CEA in all tumor types. A determination of the additive specificity and sensitivity of CA 195 and CEA did not significantly improve its clinical utility compared with CEA alone. However, CA 195 was significantly elevated in three patients with a prior history of colon cancer thought to be without evidence of active disease. Because all three of these patients had a relapse within the next 1-15 months, CA 195 might identify early relapses of colon cancer in some patients.

CONCLUSIONS

Based on these results, it was concluded that CA 195 is not superior to CEA as an indicator of disease activity in advanced colon cancer or other solid tumors. However, studies utilizing CA 195 in the detection of early relapses of colon cancer may be warranted. A review of the English literature revealed that CA 195 might be a useful marker in pancreatic cancer.

Comparison of four serum tumour markers in the diagnosis of colorectal carcinoma

The assessment of the diagnostic power of four serum tumour markers, CEA, CA 19-9, CA 50 and CA 195 for colorectal carcinoma is described, according to recently formulated guidelines. Preoperative serum concentrations of the four markers were determined in 198 colorectal cancer patients and 57 patients with a benign colorectal disorder. The cumulative frequency distributions of the malignant and benign group show strong overlap for all markers, which indicates low diagnostic ability. This is confirmed by the Receiver Operating Characteristic curves, which have areas under the curve of 0.65 (95% confidence interval (CI) 0.58-0.73) for CA 19-9, CA 50 and CA 195 and of 0.70 (95%) CI 0.63-0.77) for CEA. The new tumour markers appear to be of slightly less diagnostic value than CEA for the primary diagnosis of colorectal cancer, although the discrepancy is not statistically significant. The low diagnostic power of CA 19-9, CA 50 and CA 195 may be due to a high proportion of colorectal cancer patients having the Lewis(a-b-) phenotype, who cannot synthesise these markers.

Tumor markers CA 19-9 and CA 195 are also useful as markers for cystic fibrosis

When monoclonal kits are used we can no longer detect highly elevated serum concentrations of carcinoembryonic antigen in cystic fibrosis (CF) patients as we could earlier (Pediatr Res 10:223-236, 1975). Instead, we find increased concentrations of CA 19-9 or CA 195 in the CF sera. The serum levels of CA 19-9 not only reflect the pulmonary condition of CF patients but also respond well to antibiotic therapy. Several lines of evidence suggest that the elevated serum concentration of CA 19-9 is derived from sputum and corresponds with the amount of sputum in the lung. Correlations between CA 19-9 and CA 195 in random and serial specimens from both patients with CF and patients with pancreatic carcinoma suggest that all sera contain heterogeneous, Lewis blood group-related epitopes and the proportions of various epitopes are different among individual patients. When monitored on multiple tumor markers, the pattern of CF is different from that of pancreatic carcinoma although both usually show elevated CA 19-9. Our study indicates that both CA 19-9 and CA 195 can be used as sensitive markers for the early detection of exacerbation in CF patients.

Comparative analysis of cancer-associated antigen CA-195, CA 19-9 and carcinoembryonic antigen in diagnosis, follow-up and monitoring of response to chemotherapy in patients with gastrointestinal cancer

To establish further the clinical significance of the CA-195 tandem immunoradiometric assay in gastro-intestinal malignancies, the sera of a total of 222 subjects have been analysed and compared with assays of the "classical gastrointestinal tumour markers", CA19-9 and carcinoembryonic antigen (CEA). CA-195 elevations above normal (greater than 10 U/ml) were noted in 51/72 (70.8%) colorectal, 15/15 (100%) pancreatic, and in 6/12 (50%) gastric cancer patients. Whereas CA19-9 was increased (greater than 37 U/ml) in 65%, 93%, and 42% of cases, only 54% colorectal, 45% pancreatic, and 42% gastric cancer patients had pathologically elevated serum CEA levels (greater than 5 ng/ml). No abnormal increase of both CA-195 and CA19-9 was found in healthy volunteers, whereas 3/20 (smoking) individuals had CEA levels slightly above normal. With a 29% false-positive rate noted among 103 patients with benign gastrointestinal disorders, the specificity of CA-195 was superior to that of CA19-9 (58%) and comparable with that of CEA (31%). A significant correlation between CA-195 levels and the clinical/pathological stage of disease was noted in colorectal (P less than 0.01) and pancreatic cancer patients (P less than 0.007). Preliminary results of serial measurements of CA-195 in colorectal cancer suggest that this new marker protein, which has no cross-reactivity with CEA, may be useful as a non-invasive test for postoperative surveillance of patients to detect disease recurrence, and serve to complement (though certainly not replace) standard clinical measurements of response to chemotherapy.

Evaluation of CEA, CA 19-9, CA-50, CA-195, and TATI with special reference to pancreatic disorders

The tumor markers CEA, CA 19-9, CA-50, CA-195, and TATI were analyzed in patients with pancreatic diseases as well as disorders in the upper quadrant of the abdomen. Two different methods for CA-50, namely CA-50 IRMA and CA-50 DELFIA, which are based on the same monoclonal antibody, were used. The sensitivities, specificities, and predictive values of positive and negative results were calculated at one, three, and ten multiples of the upper reference value ("cutoff") for each method. All the tumor markers except TATI had sensitivities exceeding 90% at one cutoff level, but CEA had low specificity. Poor sensitivities were observed for CEA and TATI at three cutoff levels, whereas CA 19-9, CA-50, and CA-195 had sensitivities and specificities greater than 80%. The sensitivities of these tumor markers decreased at 10 cutoff levels, although the specificities exceeded 95%. The predictive values of positive and negative results were also evaluated at these three cutoff levels. High scores were observed at three cutoff levels. Examined together with the sensitivity and specificity, the evaluation at three cutoff levels indicated that CA 19-9, CA-50, and CA-195 can be used in the diagnostic arsenal for the detection of cancer of the exocrine pancreas in symptomatic patients, and in the differential diagnosis between pancreatic cancer and chronic pancreatitis. Although CA-50 IRMA and CA-50 DELFIA are based on the same monoclonal antibody, there were substantial differences in the levels of CA-50 in a lot of the patients when samples were analyzed by the two methods. These differences were shown to be methodological, and they affected the test evaluations to some extent.

Tissue distribution of 2-3 and 2-6 sialyl Lewis A antigens and significance of the ratio of two antigens for the differential diagnosis of malignant and benign disorders of the digestive tract

The authors investigated the tissue distribution of two kinds of sialylated derivatives of Lewis A (Le(a)) antigen in patients with cancers of the digestive system using specific monoclonal antibodies, and evaluated the significance of determining the 2-3 and 2-6 sialylated Le(a) antigen levels for the diagnosis of cancer. In most specimens from patients with cancers of the pancreas, biliary tract, stomach, and colon, the 2-3 sialylated Le(a) antigen was strongly expressed in cancer cells. However, 2-6 sialylated Le(a) antigen was less frequently expressed in cancer cells. The former is therefore more specific to cancer than the latter. Also, the serum level of the 2-3 sialylated Le(a) antigen was significantly higher than that of the 2-6 counterpart in patients with cancers of pancreas, biliary tract, stomach, and colon. The resulting ratio of serum 2-3/2-6 sialylated Le(a) antigens was frequently high in patients with malignancy and was low in patients with benign disorders of these digestive organs. Therefore, the 2-3/2-6 sialylated Le(a) antigen ratio is a useful for the differential diagnosis of malignant disorders in these organs. However, liver disorders were found to be exceptional in that both antigens were mostly absent in hepatocellular carcinoma (HCC) cells in immunohistologic examination, as well as in nonmalignant parenchymal liver cells. Only the epithelial cells of the intrahepatic bile ducts expressed the 2-6 sialylated Le(a) antigen strongly, and expressed the 2-3 sialylated Le(a) antigen moderately. The levels of both antigens were sometimes high in patients with liver disorders, but the ratio always remained low in patients with HCC as well as benign liver disorders such as cirrhosis or chronic hepatitis. The sialylated Le(a) antigens, which sometimes accumulate in the sera of patients with HCC, were concluded to originate from the epithelial cells of the proliferating small bile ducts, and those serum antigens cannot be considered as evidence for the presence of liver cancer cells.

Sialyllacto-N-fucopentaose II (sialylated Le(a)) coupled to humanserum albumin used as standard in immunoassays of tumour associated antigens CA 19-9 and CA-50 in serum

Penta and hexasaccharides from human milk, containing sialic acid and/or fucose residues were conjugated to human serum albumin and used as antigens in three different methods for CA 19-9, two methods for CA-50 and one method for CA-195. In accordance with reported results, the 19-9, CC 3C 195 and C-50 monoclonal antibodies were found to react with the sialyllacto-N-fucopentaose II conjugate, although to a different extent. A negligible reaction was observed with the isomeric conjugate, sialyllacto-N-fucopentaose III, and no reaction was seen with the sialyllacto-N-tetraose conjugate. The use of defined oligosaccharide conjugates for the standardization of assays of tumour markers in serum is discussed.

Serum levels of cancer-associated antigen CA-195 in gastrointestinal cancers and its comparison with CA19-9

The antibody against CA-195 binds to an epitope that consists of both Lewis A and sialylated Lewis A blood group antigen, whereas CA19-9 has shown specificity for sialylated Lewis A blood group antigen. CA19-9 and CA-195 levels were measured in the sera of 52 normal subjects; 65 benign disease patients; and 74 non-gastrointestinal, 149 colorectal, and 119 upper gastrointestinal cancer patients to correlate their levels with disease status of the patients. Low incidence and levels were found among normal subjects for both markers; however, in the benign disease group a slightly higher incidence of elevation was seen for CA19-9. Among colorectal cancer patients CA-195 appeared to show higher sensitivity for primary as well as advanced disease. Levels of both markers showed similar incidences of elevation among upper gastrointestinal cancer patients. Based on these results the contribution of Lea specificity of CA-195 cannot be ruled out, and it may be used alone or in combination with other markers for monitoring of patients with colorectal, pancreatic, gastric, gall bladder, bile duct, and liver cancers.

Malignant cell glycoproteins and glycolipids

The cell surface is involved in cell growth and division, cell-cell interaction, communication, differentiation and migration, and other processes likely to be involved in malignant transformation and/or the metastatic spread of cancer. Although there are many alterations of glycoproteins and glycolipids on the malignant cell surface, it is unclear whether these alterations are epiphenomena or an integral part of the malignancy process. This article reviews the recent literature and some earlier studies relevant for understanding emerging concepts and trends with respect to malignant cell glycoconjugates. Emphasis is on structural alterations of the carbohydrate portions of malignant cell glycoproteins and glycolipids and on the enzymes (glycosyltransferases and glycosidases) involved in their metabolism. Practical applications derived from malignant cell glycoconjugate studies are discussed briefly with respect to the diagnosis, staging, monitoring, and treatment of malignant disease. The review concludes by indicating which research areas on malignant cell glycoconjugates are likely to be fruitful in increasing our basic understanding of, and ability to deal effectively with, malignant disease.