Quantitative study of apoptosis in normal rat gastroduodenal mucosa

The occurrence of apoptosis in the normal gastrointestinal mucosa has been given little consideration until now, although the phenomenon may be of interest in the light of recent hypotheses about its role in physiological cell renewal. In the present study, a quantitative evaluation conducted on normal gastric and duodenal mucosa of young rats has shown that apoptosis is a rare but constant phenomenon: 1.4 +/- 1.1 (mean +/- 1 s.d.) apoptotic bodies were observed within the surface epithelium of single gastric pits and 3 +/- 1 in duodenal villi. In both situations, the apoptosis showed a preferential localization in the juxtaluminal segments of the epithelium. This phenomenon appears distinct from passive exfoliation of mucosal cells and, as an expression of 'programmed cell death', it is likely to contribute to the normal intestinal epithelial cell turnover.

Association between high concentrations of Mr 52,000 cathepsin D and poor prognosis in primary human breast cancer

The Mr 52,000 cathepsin D is the precursor of a lysosomal protease secreted in excess by breast cancer cells. This protease can degrade extracellular matrices and proteoglycans and is induced by estrogens in estrogen receptor-positive breast cancer cell lines. In a 4- to 6-yr retrospective cohort study, the concentration of the total cathepsin D (precursor plus intermediate and mature chains) was assayed in cytosols of primary tumors from 242 pre/perimenopausal and 154 postmenopausal breast cancer patients in a solid-phase immunoassay using two specific monoclonal antibodies. Patients were initially divided into groups with low, intermediate, or high concentrations of cathepsin D corresponding to the quartiles of the overall distribution. Using these groupings, the level of Mr 52,000 cathepsin D was not significantly associated with the recognized prognostic factors of age, lymph node involvement, tumor size, and/or grade of anaplasia. A significant association was found between cathepsin D concentrations and estrogen receptor status only among pre/perimenopausal patients. Receptor-positive tumors (greater than or equal to 10 fmol of estrogen receptor/mg of cytosol protein) had a significantly greater proportion of patients with high Mr 52,000 cathepsin D concentrations. Patients with high Mr 52,000 cathepsin D concentrations (greater than 78 pmol/mg for pre/perimenopausal and greater than 24 for postmenopausal patients) have shorter recurrence-free survival (P = 0.06 for pre/peri- and P = 0.039 for postmenopausal patients) and have a trend toward shorter overall survival (P = 0.30 and P = 0.089 for pre/peri- and postmenopausal groups, respectively). In multivariate analysis, Mr 52,000 cathepsin D status was found to be an independent prognostic factor for recurrence-free survival of about the same import as lymph node status for both menopausal groups. This first retrospective study demonstrates that the level of Mr 52,000 cathepsin D in cytosol of primary breast cancer biopsies is an independent prognostic factor in predicting relapses in both pre/peri- and postmenopausal patients.

A two-site immunoenzymometric assay of 52-kDa pro-cathepsin D, and its use in human breast diseases

After isolating monoclonal antibodies specific for the 52-kDa precursor of cathepsin D (cath-D), which is secreted in excess in both hormone-dependent and hormone-independent breast cancer, we developed a two-step double-determinant immunoenzymometric assay that is specific for this pro-enzyme. The assay combines the use of a monoclonal antibody specific for the precursor and bound to microtiter plates, and a second antibody directed against a smaller processed form of the mature enzyme, coupled to alkaline phosphatase. The specificity of the assay relies on separate and sequential additions of the antigen and the conjugated second antibody. It allows rapid measurement of the analyte in plasma and cytosols of normal and neoplastic mammary tissues, with a detection limit of 5 fmol and a maximal interassay coefficient of variation of 9%. This assay is particularly useful for tissue cytosol samples where the pro-enzyme form co-exists with large quantities of the mature processed forms of the enzyme. Comparative assays of 52-kDa pro-cath-D and total cath-D in cytosols of breast cancers and benign mastopathies indicate that the present assay better discriminates between benign and cancerous mammary tumors.

A two-site immunoenzymometric assay of 52-kDa pro-cathepsin D, and its use in human breast diseases

After isolating monoclonal antibodies specific for the 52-kDa precursor of cathepsin D (cath-D), which is secreted in excess in both hormone-dependent and hormone-independent breast cancer, we developed a two-step double-determinant immunoenzymometric assay that is specific for this pro-enzyme. The assay combines the use of a monoclonal antibody specific for the precursor and bound to microtiter plates, and a second antibody directed against a smaller processed form of the mature enzyme, coupled to alkaline phosphatase. The specificity of the assay relies on separate and sequential additions of the antigen and the conjugated second antibody. It allows rapid measurement of the analyte in plasma and cytosols of normal and neoplastic mammary tissues, with a detection limit of 5 fmol and a maximal interassay coefficient of variation of 9%. This assay is particularly useful for tissue cytosol samples where the pro-enzyme form co-exists with large quantities of the mature processed forms of the enzyme. Comparative assays of 52-kDa pro-cath-D and total cath-D in cytosols of breast cancers and benign mastopathies indicate that the present assay better discriminates between benign and cancerous mammary tumors.

Two-site immunoenzymometric assay for the 52-kDa cathepsin D in cytosols of breast cancer tissues

We developed a solid-phase two-site immunoenzymometric assay (IEMA) of the estrogen-induced 52-kDa cathepsin D (EC 3.4.23.5) and its processed forms (48-kDa and 34-kDa proteins) in cytosols of breast cancer tissues, using two monoclonal antibodies directed against two different epitopes of these antigens. The first antibody is bound to a polystyrene microtiter well; the second is labeled with alkaline phosphatase. The assay involves a simultaneous incubation of the antigen with both antibodies, because we observed signal loss during sequential incubations. Alkaline phosphatase was chosen because other enzymes (peroxidase, beta-galactosidase) were inhibited by cytosol extraction buffers. The measurable range of 52-kDa-related proteins is from 0.3 to 6 nmol/L with precision (CVs) within and between runs of 3.9% and 15.8%, respectively. The sensitivity, accuracy, and rapid turnaround time of the two-site IEMA should facilitate the clinical evaluation of this new marker in oncology.

Two-site immunoenzymometric assay for the 52-kDa cathepsin D in cytosols of breast cancer tissues

We developed a solid-phase two-site immunoenzymometric assay (IEMA) of the estrogen-induced 52-kDa cathepsin D (EC 3.4.23.5) and its processed forms (48-kDa and 34-kDa proteins) in cytosols of breast cancer tissues, using two monoclonal antibodies directed against two different epitopes of these antigens. The first antibody is bound to a polystyrene microtiter well; the second is labeled with alkaline phosphatase. The assay involves a simultaneous incubation of the antigen with both antibodies, because we observed signal loss during sequential incubations. Alkaline phosphatase was chosen because other enzymes (peroxidase, beta-galactosidase) were inhibited by cytosol extraction buffers. The measurable range of 52-kDa-related proteins is from 0.3 to 6 nmol/L with precision (CVs) within and between runs of 3.9% and 15.8%, respectively. The sensitivity, accuracy, and rapid turnaround time of the two-site IEMA should facilitate the clinical evaluation of this new marker in oncology.

Immunoenzymatic assay of Mr 52,000 cathepsin D in 182 breast cancer cytosols: low correlation with other prognostic parameters

The Mr 52,000 cathepsin-D-like protease induced by estrogens in MCF7 human breast cells was assayed in 182 primary breast cancer cytosols prepared for receptor assays from pre- and post-menopausal patients. Using two solid-phase sandwich immunoenzymatic assays, we quantified the total Mr 52,000 cathepsin D (52K-cath-D) (the Mr 52,000 precursor protein and its Mr 48,000 and 34,000 processed forms) and the Mr 52,000 precursor alone. The value of total 52K-cath-D varied between 3 and 165 pmol/mg protein and the proportion of the precursor varied from 0 to 28% of total 52K-cath-D. There was no correlation between the concentrations of 52K-cath-D and estrogen receptor, but the estrogen receptor status (greater than or less than 10 fmol/mg protein) was correlated to the 52K-cath-D status (greater than or less than 15 pmol/mg protein) according to the chi 2 test (P less than 0.001). The correlation with progesterone receptor concentrations and status was low (r = 0.43) and absent, respectively. There was no correlation with Scarff and Bloom stages, tumor size, or patient's age. The percentage of patients with invaded lymph nodes was significantly higher (80%) in the subgroup with the highest total 52K-cath-D levels (greater than or equal to 42 pmol/mg protein), representing only 12% of the population but not in the total population. On the basis of this prospective study, before clinical follow-up can be evaluated, we conclude that in the total population examined, the 52K-cath-D concentration was only correlated with estrogen receptor status, but not with any other prognostic parameter.

Monoclonal antibody mapping of the antigenic surface of human thyrotropin and its subunits

Although the amino acid sequence of the alpha- and beta-subunits of glycoprotein hormones in various species has been deciphered, data on their tertiary structure are not abundant. This impedes correlation between structure and function. The availability of monoclonal antibodies to human TSH (hTSH) offers the opportunity to enumerate the antigenic determinants present on the surface of hTSH and its subunits and to examine their spatial relationships. Twenty-eight monoclonal antibodies to hTSH were obtained from several fusions, and screens carried out separately in the laboratories involved in this study. Affinities for hTSH ranged from 10(8)-10(11) M-1. Cross-reactivity with bovine TSH (bTSH), human gonadotropins (hLH, hFSH, and hCG), and the alpha- and beta-subunits of hTSH distinguished 10 groups of monoclonal antibodies (mAb) according to their main cross-reactions: 1) hTSH alpha, hLH, hFSH, and hCG; 2) hTSH alpha, bTSH, hLH, hFSH, and hCG; 3) hFSH; 4) bTSH and hFSH; 5) bTSH, hLH, and hFSH; 6) bTSH, hLH, hFSH, and hCG; 7) hTSH beta; 8) hTSH beta and bTSH; 9) hTSH beta and hFSH; and 10) hTSH beta, hLH, hFSH, and hCG. mAb were incorporated into 2-site binding assays to probe hTSH by a 28 X 28 matrix, the free alpha-subunit by a 4 X 4 matrix, and the free beta-subunit by a 18 X 18 matrix. Regarding intact hTSH, 12 different clusters of mAb were distinguished and interpreted as reflecting 12 distinct antigenic regions on the surface of the hTSH molecule. Two of them were localized on the alpha-subunit, and 6 on the beta-subunit; 4 were only expressed by the holo-hormone and, thus were designated conformational antigenic regions (alpha beta). Surface mapping of the free alpha- and beta-subunits was virtually identical to that observed with the holo-hormone. Modification of the operative conditions of mAb reacting only with holo-hTSH shows that they recognize the alpha-subunit, but not the beta-subunit of hTSH. These results indicate that 1) hTSH beta presents epitopes that are evolutionary conserved; 2) hTSH alpha presents several epitopes that are species specific and 2 that are not hormone specific; 3) dissociation of hTSH does not modify the antigenic surface expressed by both subunits when they are associated; and 4) some of the conformational determinants expressed only by holo-hTSH are more likely derived from the alpha-subunit than from the beta-subunit.

Production and characterization of monoclonal antibodies to human growth hormone

Three BIOZZI-HR mice were immunized with human growth hormone (hGH). From the determination of the titer, the average equilibrium association constant and the heterogeneity index of the antisera, it was possible to select the most suitable mouse for production of monoclonal antibodies (Mabs). Resulting from a single fusion, eight Mabs were produced, purified and characterized. The equilibrium association constant of the Mabs ranged from 5.10(8) M-1 to 9.109 M-1 at physiological pH. Four areas on hGH are recognized by the Mabs (the topology of the Mabs was investigated by two-site immunoradiometric assays). The Mabs, which recognize a same area, show similar cross-reactivities between hGH and human Placental Lactogen (hPL). No selected Mabs bound human Prolactin (hPRL), equine Growth Hormone (eGH) and porcine Growth Hormone (pGH). Two complementary Mabs enable a two-site immunometric assay of pituitary and E. Coli derived hGH.

Immunotoxins: hybrid molecules of monoclonal antibodies and a toxin subunit specifically kill tumour cells

Several attempts to attack tumours in experimental systems have been made using conjugates of chemotherapeutic agents or potent toxins with antibodies (immunotoxins). In vitro studies have been highly successful, showing target specificity of a high order in some cases. However, so far, such conjugates have been inadequate in vivo, probably for two main reasons. First, conventional heteroclonal antibodies are perhaps inappropriate, because purification by biochemical methods leaves a large amount of non-antibody gamma-globulins. The use of monoclonal antibodies may overcome this problem. Second, when whole toxins have been conjugated to antibodies there has been a strong residual nonspecific cytotoxicity due to the binding capacity of a subunit, the B-piece of the toxin. (Diphtheria toxin or ricin consist of two polypeptide subunits. The A-piece is responsible for inhibition of protein synthesis on ribosomes, and the B-piece binds to galactose residues on the cell membrane and facilitates the transmembrane passage of the A-piece.) In the present work the problem of nonspecific binding by the B-piece has been circumvented by using the A-piece only as the toxin component of immunotoxins; these immunotoxins are active both in vitro and in vivo.