Cleavage of a hydrophilic C-terminal domain increases growth-inhibitory activity of oncostatin M.

Oncostatin M is a polypeptide cytokine, produced by normal and malignant hematopoietic cells, that has several in vitro activities, including the ability to inhibit growth of cultured carcinoma cells. Here we present a structural and functional comparison of two oncostatin M-related proteins (Mr 36,000 and 32,000) secreted by COS cells transfected with oncostatin M cDNA. The smaller of these forms lacked a hydrophilic C-terminal domain comprising predominantly basic amino acids. This domain was also absent from native oncostatin M produced by U937 cells. The 32,000-Mr form of oncostatin M was not produced by cells transfected with plasmids (G195 and G196) in which a potential trypsinlike cleavage site within the hydrophilic C-terminal domain was altered by site-directed mutagenesis. A 32,000-Mr fragment was produced by trypsin treatment of the 36,000-Mr form of oncostatin M. These observations suggest that the 32,000-Mr form of oncostatin M was derived from the 227-amino-acid propeptide by proteolytic cleavage at or near the paired basic residues at positions 195 and 196. Pro-oncostatin M was equally active in radioreceptor assays as the processed form but was 5- to 60-fold less active in growth inhibition assays. Likewise, nonprocessed mutant protein encoded by plasmid G196 was equally active in the radioreceptor assays as the processed form but was five- to ninefold less active in growth inhibition assays. Thus, the highly charged C-terminal domain of pro-oncostatin M is not required for receptor binding or growth-inhibitory activity but may alter the functional properties of the molecule. Propeptide processing of oncostatin M may be important for regulating in vivo activities of this cytokine.

Molecular cloning, sequence analysis, and functional expression of a novel growth regulator, oncostatin M.

Oncostatin M is a polypeptide of Mr approximately 28,000 that acts as a growth regulator for many cultured mammalian cells. We report the cDNA and genomic cloning, sequence analysis, and functional expression in heterologous cells of oncostatin M. cDNA clones were isolated from mRNA of U937 cells that had been induced to differentiate into macrophagelike cells by treatment with phorbol 12-myristate 13-acetate, and a genomic clone was also isolated from human brain DNA. Sequence analysis of these clones established the 1,814-base-pair cDNA sequence as well as exon boundaries. This sequence predicted that oncostatin M is synthesized as a 252-amino-acid polypeptide, with a 25-residue hydrophobic sequence resembling a signal peptide at the N terminus. The predicted oncostatin M amino acid sequence shared no homology with other known proteins, but the sequence of the 3' noncoding region of the cDNA contained an A + T-rich stretch with sequence motifs found in the 3' untranslated regions of many cytokine and lymphokine cDNAs. Oncostatin M mRNA of approximately 2 kilobase pairs was detected in phorbol 12-myristate 13-acetate-treated U937 cells and in activated human T cells. Transfection of cDNA encoding the oncostatin M precursor into COS cells resulted in the secretion of proteins with the structural and functional properties of oncostatin M. The unique amino acid sequence, expression by lymphoid cells, and growth-regulatory activities of oncostatin M suggest that it is a novel cytokine.

Heritable variation in expression of multiple tumor associated epitopes on a high molecular weight mucin-like antigen.

Monoclonal antibodies with specificity for mucin-like antigens have shown great promise for the diagnosis and therapy of human cancer. Heterogeneity in the expression of mucin-like antigens by tumor and normal cells has been noted in several previous studies. An understanding of the nature of this heterogeneity has important implications for the diagnostic and therapeutic usefulness of antibodies to mucin-like antigens. We have studied the mechanism of variability in expression of epitopes on a mucin-like antigen defined by monoclonal antibodies W1, W5, and W9 in the lung carcinoma cell line, Calu-1. Using the fluorescence activated cell sorter and clonal analysis, we have demonstrated that intercellular variability in mucin antigen expression by Calu-1 cells can be explained in part by heritable variation in the tumor cell population. Clonal cell lines were isolated which differ greatly in levels of epitopes for all three mucin directed antibodies. Levels of all three epitopes showed significant variation between different clonal lines but in general were coordinately regulated. Differences in epitope expression between two lines studied in detail could be attributed to a dramatic difference in expression of a high molecular weight mucin-like glycoprotein. In immunoblotting experiments the binding of all three antibodies to this glycoprotein was affected by sodium periodate and/or neuraminidase treatment, suggesting that the antibodies recognize carbohydrate epitopes. Thus, heterogeneity in expression of mucin-like glycoprotein antigens can result from heritable variations which affect expression of multiple carbohydrate epitopes.

Elevated levels of a high molecular weight antigen detected by antibody W1 in sera from breast cancer patients.

A novel screening assay was used to test 13 previously described antibreast cancer antibodies for those which recognize antigens elevated in serum of breast cancer patients. Binding of three of these antibodies to breast or lung carcinoma cells was inhibited to a significantly greater extent by tumor patient serum than by normal serum, suggesting that the antigens might be useful serum markers. Two of these antibodies, W1 and W9, were shown to recognize nonoverlapping epitopes on a high molecular weight molecule(s) purified from serum from breast cancer patients. A sensitive double determinant immunoassay was developed to measure W1 antigen levels in sera from a total of 389 cancer patients and controls. Forty seven % (37 of 79) of individuals having breast cancer showed elevated serum levels of the W1 antigen, whereas only 4% (1 of 25) of normal controls and 2% (1 of 47) of patients hospitalized for nonmalignant disorders showed elevated levels. These differences were statistically significant (P less than 0.001). The percentage of breast cancer patients showing elevated serum levels was greater for individuals with metastatic disease. Statistically significant numbers of lung, ovarian, and prostate, but not colon, cancer patients also had elevated serum levels of the W1 antigen. These data suggest that measurement of the W1 antigen in serum might provide clinically useful information on the course of metastatic breast and other cancers.

Primary health care providers' knowledge gaps on Parkinson's disease.

In order to determine primary health care providers' (PCPs) knowledge gaps on Parkinson's disease, data was collected before and after a one-hour continuing medical education (CME) lecture on early Parkinson's disease recognition and treatment in a sample of 104 PCPs participating at an annual meeting. The main outcome measure was the proportion of questions answered correctly by each PCP before the lecture. We measured the change in proportion of correct answers before and after the lecture (delta). Ninety-nine percent of the PCPs who attended the lecture returned the questionnaire. The level of knowledge on Parkinson's disease before the lecture was relatively low, particularly in management (61.4%) and diagnosis (34.4%). PCPs' perceived knowledge was not associated with the number of correct responses on management at baseline. Test scores significantly improved after the CME lecture. Our results show that PCPs' baseline knowledge of diagnosis and management of Parkinson's disease and self-perceived knowledge on this topic are relatively limited. Appropriately, US reaccreditation programs do not only rely on self-perception. Longitudinal studies are needed to determine the impact of CME in knowledge retention and patient care in Parkinson's disease.

Identification and characterization of cellular receptors for the growth regulator, oncostatin M.

Oncostatin M is a polypeptide growth regulator produced by activated T cells and phorbol ester-treated U937 cells. To identify specific cellular receptors for this factor, we have characterized the binding of 125I-labeled oncostatin M to a variety of normal and malignant mammalian cells. Recombinant oncostatin M was labeled with 125I with full retention of growth inhibitory activity on A375 melanoma cells. 125I-Oncostatin M bound to sensitive cells in a time- and temperature-dependent fashion. Binding was specifically inhibited by unlabeled native or recombinant oncostatin M, but not by other polypeptide growth factors tested. Binding to human leukemic and normal blood cells was generally less than to nonhematopoietic cells. With four different cell lines, maximal growth inhibition by oncostatin M was achieved at less than maximal binding site occupancy. Scatchard graphs of direct binding data were curvilinear and indicated that 125I-oncostatin M bound with higher apparent affinity at lower 125I-oncostatin M concentrations. Using a two binding site model, affinity constants of Kd1 = 11 +/- 11 pM and Kd2 = 1000 +/- 380 pM were extrapolated from binding data with A375 cells, and values of Kd1 = 3 +/- 2 pM and Kd2 = 400 +/- 44 pM from A549 cells. The major 125I-oncostatin M binding species in a number of mammalian cell lines was identified by chemical cross-linking as a specific protein(s) of Mr = 150,000-160,000. 125I-Oncostatin M was internalized (t1/2 = 30 min) and degraded subsequent to binding to a responsive cell line.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of a novel serum protein secreted by lung carcinoma cells.

The murine anti-human lung tumor monoclonal antibody L3 recognizes antigens found both in the medium of cultured carcinoma cells and in normal human serum. Sequential immunoprecipitation experiments indicate that the L3 antigen is also recognized by a previously described monoclonal antibody directed against a melanoma-associated antigen [Natali, P. G., Wilson, B. S., Imai, K., Bigotti, A., & Ferrone, S. (1982) Cancer Res. 42, 583-589]. This antibody precipitated a Mr 76000 glycoprotein from metabolically labeled extracts of the lung carcinoma cell line Calu-1 and a Mr 94 000 glycoprotein from labeled culture medium. Pulse-chase experiments suggested a precursor-product relationship between these molecules. Analysis of glycosidase sensitivities of the two forms indicated that maturation of carbohydrate side chains correlated with the apparent increase in molecular weights. L3 antigenic activity, measured in a competitive radiometric cell binding assay, was purified more than 90-fold from serum-free medium of Calu-1 cells and more than 3000-fold from normal human serum. The major immunoreactive components purified from culture medium and serum were identical with respect to apparent molecular weight, electrophoretic mobility, pI, glycosidase sensitivity, and V8 protease fingerprints. In addition, the sequence of the amino-terminal 16 N-terminal amino acid residues of the major immunoreactive species from both sources was identical. The properties of the L3 antigen did not correspond to those of any known protein, suggesting that this serum protein has not been previously characterized.

Regulation of cell growth by recombinant oncostatin M.

Oncostatin M is a novel growth regulator originally isolated from differentiated human histiocytic lymphoma cells and activated T-lymphocytes based on its ability to inhibit the growth of A375 melanoma cells. We report here that oncostatin M is a widely acting regulator which alters the growth and/or morphology of cells derived from a variety of cancer cell types. At picomolar concentrations, recombinant oncostatin M inhibited the growth of 13/24 tumor cell lines. Six out of 7 lung cancer cell lines were inhibited by oncostatin M, but none of 6 colon cancer cell lines were affected. Oncostatin M also stimulated the growth of some normal cells (3/6), indicating that it, like many growth regulators, is bifunctional. Oncostatin M receptors appear necessary but not sufficient for a growth response to oncostatin M, since none of the cell lines lacking receptor responded to oncostatin M, whereas many but not all cell lines with receptor responded to oncostatin M. Receptor size (Mr congruent to 150,000) was similar for cells in which growth was inhibited, stimulated, or unaffected by oncostatin M.