Isolation and partial characterization of macromolecular urinary aggregates containing carcinoembryonic antigen-like activity

Trends in urine biomarker discovery for urothelial bladder cancer: DNA, RNA, or protein?

Urothelial bladder cancer is a complex disease displaying a landscape of heterogenous molecular subtypes, mutation profiles and clinical presentations. Diagnosis and surveillance rely on flexible cystoscopy which has high accuracy, albeit accompanied by a high-cost burden for healthcare providers and discomfort for patients. Advances in "omic" technologies and computational biology have provided insights into the molecular pathogenesis of bladder cancer and provided powerful tools to identify markers for disease detection, risk stratification, and predicting responses to therapy. To date, numerous attempts have been made to discover and validate diagnostic biomarkers that could be deployed as an adjunct to the cystoscopic diagnosis and long-term surveillance of bladder cancer. We report a comprehensive literature analysis using PubMed to assess the changing trends in investigating DNA, RNA, or proteins as diagnostic urinary biomarkers over a period of 5 decades: 1970-2020. A gradual shift has been observed in research away from protein biomarkers to nucleic acids including different classes of RNA, and DNA methylation and mutation markers. Until 2000, publications involving protein biomarker discovery constituted 87% of the total number of research articles with DNA comprising 6% and RNA 7%. Since 2000 the proportion of protein biomarker articles has fallen to 40%, and DNA and RNA studies increased to 32% and 28%, respectively. Clearly research focus, perhaps driven by technological innovation, has shifted from proteins to nucleic acids. We optimistically hypothesise that, following thorough validation, a clinically useful detection test for bladder cancer based on a panel of DNA or RNA markers could become reality within 5-10 years.

Determination of incidence and partial characterization of tumor-associated antigens found in the urine of patients bearing solid tumors

Urine samples from patients with solid tumors and from donors without malignant disease were concentrated and tested for the presence of tumor-associated antigens. In the complement-fixation assay using serum from a source autologous with the source of the urine, 87.4% of cancer patients were positive, while only 6.9% of control donors were positive. When serum from an allogenic source was used, 94.7% of cancer patients and 35.1% of control donors were positive. Absorption of a cancer patient's serum with autologous tumor cells removed antibody activity to autologous and allogeneic urine samples. Normal lymphocytes, skin, or muscle-cell suspensions were ineffective as absorbents. The excretion of antigen into urine is dependent upon the presence of tumor. Surgical removal of tumor resulted in cessation of antigen excretion. The urine remained antigen-negative as long as the patient remained disease-free. The antigenic activity was heat-stable and comprised molecules of greater than 1,000,000 daltons which could be dissociated into smaller molecular weight active fractions by treatment with 6 M urea.

Improved performance of a double antibody radioimmunoassay for carcinoembryonic antigen

A new double antibody solid-phase radioimmunoassay (RIA) for carcinoembryonic antigen (CEA) is critically analyzed. The aim of the study was 4-fold: (a) to define the level of sensitivity (a comparison of 3 different assay procedures revealed that our sequential assay was more sensitive than most previously reported RIAs, while competitive and non-equilibrium assay had wider measuring ranges); (b) to analyze recoveries of CEA in either serum, plasma or urine (the recovery, even in urine, was very close to expected values, indicating that no CEA is lost or degraded during brief storage or in the extraction procedure); (c) to evaluate inter- and intra-assay variations, since most clinical management is dependent on serial assays rather than single determinations. The coefficients of variation were low both within and between assays. A change of 3 ng CEA is required for significant change (greater than 2 S.D.) at the normal serum level which is 16 ng CEA/ml in our assay. At levels above normal, a change of 4 ng is required; (d) the assay was also developed for determination of CEA levels in a large series of perchlorid acid treated serum, plasma or urine samples. This forms the basis for an assay suitable for serial assays with high sensitivity and accuracy in various neoplastic diseases.

Detection of cancer-associated antigen(s) in urine of sarcoma patients

Tumor-associated antigens were demonstrated in concentrated and dialyzed urine of several sarcoma patients with large tumor burden. The antigens were detected by complement fixation using autologous and allogeneic sera from sarcoma patients. The antigenic activity in three patients who were studied sequentially disappeared after surgical ablation of tumor. In two of these three patients, the antigenic activity reappeared before tumor recurrence. The reactivity of the sarcoma sera to the urine could be abolished by absorption of the sera with human sarcoma cells but not by normal human liver cells, which indicates that the same antigen was present in the urine and on biopsy-obtained sarcoma cells. Urine from cancer patients with high tumor burden may be useful as a source of tumor-associated antigen. Further studies on the presence of these antigens in urine of sarcoma patients may lead to a method for detecting subclinical tumor recurrence.

Cellular content of carcinoembryonic antigen in urothelial carcinoma

CEA containing cells can be demonstrated in 25--60% of urothelial carcinomas. No staining was seen with benign urothelial cells. Using microfluorometry of single cells, mean fluorescence intensity with anti-CEA antisera was 3--6 times that of preparations stained in parallel with nonimmune sera. A comparison of the IF results with RIA implies a possibility to detect less than 1 pg CEA/cell in unfixed specimens. The cells which stained with anti-CEA antisera did not have any apparent morphologic properties differentiating them from neighboring nonstained cells but it was mainly in the cell populations from well- and moderately well-differentiated tumors that CEA containing cells were seen. Therefore quantitative measurements of CEA amount/cell may be a parameter, in addition to morphologic differentiation, to study new properties of tumor cell populations.

Use of heterogenous and monospecific antisera for the diagnosis of bladder cancer

A rabbit antibody to antigens present in urine from bladder cancer patients was prepared and used in conjunction with various monospecific antisera to detect urine components related to bladder cancer. All urine samples were centrifuged routinely, dialyzed and concentrated 10 times before assay by gel diffusion versus the various antisera. Urine was considered positive when it showed reactivity with 2 or more antibodies. This method of analysis resulted in the diagnosis of 64% of the bladder papillomas and 77% of the bladder cancers tested, compared to only a 7% falsely positive rate with normal urine. These data support the potential usefulness of an antiserum panel in the immunological diagnosis of bladder cancer in the general population and in high risk individuals.

Characterization of urothelial carcinoma with respect to the content of carcinoembryonic antigen in exfoliated cells

A sutstance immunologically similar to carcinoembryonic antigen (CEA) was demonstrated in urothelial bladder carcinoma cells. When indirect immunofluorescence with specific anti-CEA antisera was used, CEA-containing cells were seen in 18 out of 40 cases in 5% to 30% of the cells. Among patients with tumor cells of well differentiated morphology, 61% had CEA-containing cells, compared with only 24% of patients with a poorly differentiated tumor. Microfluorometry of single cells was performed in six cases to estimate the range of CEA content. The mean fluorescence intensity with anti-CEA antiserum was three to six times that of the same tumor cell population stained with non-immune rabbit sera. This fluorescence was decreased when the anti-CEA anti-sera were incubated with CEA but not with nonspecific cross-reactive antigen. The results show a wide range of CEA antigen content in exofoliated bladder tumor cells. In addition to proliferative status and differentiation, quantitative CEA measurements give further possibilities to study characteristics of tumor cell populations.

Immunological detection of human bladder carcinoma

A rabbit antiserum (RABCa) to membrane antigenic extracts of human bladder carcinomas was produced. RABCa failed to detect bladder cancer-specific antigens in gel diffusion reaction against antigenic extracts of bladder carcinoma and normal bladder mucosa. However, RABCa showed higher complement fixation activity against urines from bladder cancer patients compared with normal urines. The micro-complement fixation (CF) assay (108 patients) was positive in 17 of 27 bladder cancer patients (62.9%) compared to only 1 of 29 normals (3.4%). However, 10 of 11 patients with urinary infections also were positive. A micro-Ouchterlony agar gel diffusion assay was also used to study urine samples (118 patients). RABCa produced separate precipitin bands against 20 of 30 bladder cancer urines (66.7%) while only 1 of 24 normal urines gave these bands (4.2%). Again, infected urines were positive (9 of 11). Additionally, urine from patients with benign urological disease was often positive in CF (11 of 41) and Ouchterlony (15 of 43) assays. RABCa serum was absorbed with normal bladder mucosa membrane extracts either once (1X) or three times (3X) to increase the specificity of the Ouchterlong gel diffusion assay. Using RABCa (1X) the per cent of positive bladder cancer urines and normals decreased only slightly, while the number of positive reactions against benign urological disease urines dramatically decreased (17.9%). RABCa (3X) further reduced the per cent of positive reactions with benign urological disease urines (10.3%), greatly reduced the reactivity with infected urines (60.0%), and gave no positive reactions with normal urines, without significantly decreasing the abiltiy to detect bladder carcinoma (51.9%). Although RABCa was 100% effective in detecting high grade (III) bladder tumors, almost two-thirds of all transitional cell papilloma urines were also positive. The nature of the material detected in bladder cancer and infected urines by RABCa is probably a product of in vivo inflammation. It does not appear to be part of the bacterial cell membrane or a bacterial metabolite. CEA (up to 10 ng/ml) did not produce positive precipitin bands with RABCa. Sephadex G-100 fractionation of urines suggests that RABCa reacts in the CF and Ouchterlony assays with a component or urine which has a molecular weight greater than 100,000-200,000 M.W. In summary, an antiserum has been prepared which may be used in micro-complement fixation and micro-Ouchterlony agar gel diffusion assays for immunological screening in the early detection of clinical disease, especially bladder cancer and urinary infection.

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.