Oncogene-related serum proteins and cancer risk: a nested case-control study

Proto-oncogenes are genes coding for factors involved in cellular growth, reproduction, and differentiation. Cancer results through mutations of proto-oncogenes or through other mechanisms involving the products of proto-oncogenes. This study asks whether serum proteins immunologically related to the products of proto-oncogenes distinguish older men and women who manifest a new cancer during a 2-year follow-up. The authors conducted a nested case-control study that involved 248 men and women selected from a larger group of older (age > or = 65 years) healthy volunteers in a randomized clinical trial of preventive clinical services. Study subjects included 37 with a fatal cancer, 59 non-fatal breast, prostate, colon, or lung cancer, 58 hospitalized with at least one discharge diagnosis that coded to benign neoplasia (International Classification of Diseases, 9th Revision codes 210-239), and 94 randomly selected controls. Using seven monoclonal antibodies prepared against ras, erb-B, FES, myb, and SIS polypeptide sequences, immunoblots detected 17 proteins in serum collected from subjects before the clinical recognition of cancer. Five oncogene-related serum proteins appeared to distinguish older persons who manifested fatal (but not non-fatal) cancer over a brief (2-year) follow-up. Older persons hospitalized with benign neoplasia also had higher levels of these serum proteins. Relative to the 94 control subjects, a 52,000 dalton SIS-related protein (odd ratio (OR) = 5.9, 95% confidence interval (CI) 1.4-24.9) and a 35,000 dalton k-ras-related protein (OR = 11.3, 95% CI 1.2-104) were particularly common in serum from the 37 subjects who manifested a fatal cancer.

Evaluation of oncogene-related proteins in serum

We hypothesize that the products of cellular oncogenes and antioncogenes are biomarkers of events related to cancer risk. This study uses monoclonal antibody technology to examine serum proteins which are immunologically related to ras oncogene and epidermal growth factor receptor proteins. We measured the prevalence of ras- and epidermal growth factor receptor-related proteins in stored and freshly frozen serum from cancer patients, male heavy smokers, and older healthy subjects. Work emphasized the attainment of inter- and intraobserver agreement between independent readings of immunoblot gels. Although we achieved acceptable levels of agreement, we uncovered evidence for blood collection and storage artifacts. Accounting for these artifacts, we compared 80 cancer patients and 188 middle-aged and older community controls and found a strong relationship (odds ratio = 11.1; 95% confidence interval, 6.0-20.6) between cancer and a M(r) 21,000 serum protein related to the ras oncogene product. These results indicate the need and importance of comprehensive pretesting of putative cancer biomarkers before use in applied or etiological epidemiological research.

Protein binding, sister chromatid exchange and expression of oncogene proteins in patients treated with cisplatinum (cisDDP)-based chemotherapy

The aim of this pilot was to evaluate the feasibility of incorporating several complementary biologic markers into a molecular epidemiologic study of chemotherapy patients. Thirty-two cancer patients being treated with cis-DDP-based chemotherapy for the first time were enrolled in the study and donated a baseline sample and at least one post-treatment sample of blood. Sister Chromatid Exchange (SCEs) and plasma protein and hemoglobin binding by cisDDP were significantly increased in samples drawn at various timepoints following treatment. The pattern of nine different oncogene protein products (including those of ras, fes, and myc) remained unchanged in sera of six patients followed over the course of their treatment. However, the levels of ras P21 product were significantly elevated above normal, control levels in all six cancer patients--both prior to and throughout the course of chemotherapy. These results suggest the usefulness of utilizing a battery of markers to evaluate biologic response to cisplatinum-based chemotherapy.

Serum oncogene proteins in foundry workers

A new technique for detecting oncogene activation based on immunoblotting for oncogene proteins in serum has been applied to screen a cohort of foundry workers with well-defined workplace exposures to polycyclic aromatic hydrocarbon carcinogens. Three of the 18 individuals screened were found to have abnormal expression of the proteins of the ras and fes oncogenes. These three individuals were known to have had medium to high workplace exposures to benzo(a)pyrene and to have correspondingly high levels of benzo(a)pyrene-DNA adducts in their peripheral leukocytes. No individuals among the unexposed controls were found to have abnormal serum oncogene protein expression. These results suggest the feasibility of using serum oncogene proteins along with DNA-carcinogen adducts as potential molecular epidemiological markers in exposed worker populations; further, larger scale studies will be necessary to demonstrate the utility of these markers for identifying individuals at risk for the development of malignant disease due to their occupational exposures.

Serum oncogene proteins in hazardous-waste workers

Oncogene protein detection may be a valuable molecular epidemiological marker of commitment to the carcinogenic pathway in worker populations exposed to carcinogens. This paper reports the use of serum immunoblotting with monoclonal antibodies to oncogene proteins to screen hazardous waste workers with potential carcinogen exposure who employ state-of-the-art work practices and personal protective equipment to minimize real exposures. Two individuals in this cohort were found to be trace positive for the ras oncogene protein in their serum, but this may have been due to their cigarette smoking. These results are contrasted to previous results in hazardous waste workers with real workplace carcinogen exposures.

Serum screening for oncogene proteins in workers exposed to PCBs

A cohort of 16 municipal workers engaged in cleaning oil from old transformers was examined for possible health effects from exposure to polychlorinated biphenyls (PCBs). In addition to the evaluation of routine clinical parameters (history, physical examination, liver function tests, serum triglycerides, serum PCB values), a new screening technique for the presence of oncogene proteins in serum using monoclonal antibodies was used to ascertain the potential carcinogenic risk from exposure in these workers. Except for one individual, serum PCB concentrations were found to be relatively low in this cohort, probably due to the observance of appropriate protective precautions. The results of liver function test were within normal limits and serum triglyceride concentrations showed no consistent relation to PCB concentrations. Six individuals, all of whom were smokers, showed abnormal banding patterns for fes oncogene related proteins. The individual with the highest serum PCB concentration also exhibited significantly raised levels of the H-ras oncogene related P21 protein in his serum. These oncogene protein findings may be indicative of an increased risk for the development of malignant disease in these individuals.

Expression of p21ras in normal and malignant human tissues: lack of association with proliferation and malignancy

Proteins encoded by cellular ras oncogenes (p21ras) are expressed in a wide variety of malignant tumors, including carcinomas, lymphomas, and neuroectodermal tumors. The function of p21ras in these tumors and the distribution and role of p21ras in corresponding normal tissues are unclear. This immunohistochemical study examined the relationship between p21ras expression and malignant transformation, cellular differentiation, and proliferative activity in vivo. p21ras was found to be widely expressed in normal tissues, but within those tissues expression was often sharply restricted to cells at specific stages of differentiation; terminally differentiated cells generally showed stronger reactivity with antibodies to p21ras than did rapidly proliferating cells. Fetal and adult tissues had corresponding patterns of p21ras expression, and the distribution of p21ras in neoplasms paralleled the pattern in normal tissue from which they were derived. Thus, p21ras seems to play a role in many fully differentiated cell types, and levels of p21ras expression do not correlate with proliferative activity in normal cell or, in contrast to past reports, with the transformed phenotype.

Human oncogene-related proteins in urine during pregnancy and neoplasia

The use of site-directed monoclonal antibodies for the detection of oncogene-related proteins in human urine samples is described. This approach identifies differential elevations of such proteins in the urine of various cancer and pregnant patients.

Anti-peptide antibodies detect oncogene-related proteins in urine

Antisera to a number of synthetic peptides predicted from nucleic acid sequences of oncogenes have been used to screen 483 urine samples of cancer patients, pregnant women, and normal controls for the presence of immunologically related proteins. Increased levels of oncogene-related proteins are found during neoplasia and pregnancy. The differential detection of these oncogene-related proteins indicates that panels of monoclonal antibodies may provide a convenient noninvasive means of detecting, classifying, and staging a wide variety of malignancies and may be useful in following fetal development during pregnancy.

Blockade of autocrine stimulation in simian sarcoma virus-transformed cells reverses down-regulation of platelet-derived growth factor receptors

The viral (v)-sis oncogene encodes a protein (p28sis) that is structurally homologous to platelet-derived growth factor (PDGF). We have shown that simian sarcoma virus (SSV)-transformed cells containing the v-sis oncogene release a Mr 20,000 substance that is recognized by antisera to synthetic peptide sequences contained in p28sis. Medium conditioned by SSV-transformed cells competes with 125I-labeled PDGF for specific PDGF receptor sites, initiates DNA synthesis, and stimulates tyrosine phosphorylation of the PDGF receptor when added to normal cells. When normal cells are co-cultured with SSV-transformed cells, the PDGF receptors of the normal cells are down-regulated by factors released from the transformed cells. Thus, SSV-transformed cells release material that is functionally similar to PDGF. We have used anti-phosphotyrosine antibodies to purify PDGF receptors and to detect PDGF-stimulated receptors in normal cells. SSV-transformed cells have no PDGF receptors detectable by these antibodies or by 125I-labeled PDGF binding studies. However, when SSV-transformed cells are exposed to suramin, a compound that blocks binding of PDGF to its receptors, the receptors reappear on the cell surface and within 8 hr are present at the same levels as in control cells. These "new" receptor sites can be phosphorylated in response to PDGF. Thus, the absence of PDGF receptors in SSV-transformed cells is due to down-regulation of the receptors by an autocrine mechanism that can be blocked by suramin.

Detection of high molecular weight forms of platelet-derived growth factor by sequence-specific antisera

Antisera to synthetic peptides representing sequences of both chains of platelet-derived growth factor (PDGF) were used to structurally analyze PDGF isolated from outdated human platelets and PDGF-like proteins in normal and transformed cells. Most PDGF isolated from platelets did not contain the carboxyl portion of PDGF-2 in contrast to p20sis, the major form of p28sis detected in simian sarcoma virus-transformed cells. In addition, higher molecular weight forms of molecules containing PDGF-1 and PDGF-2 sequences were detected in all cell lines tested. These lines were heterogeneous with respect to species, cell type, and transforming agent.

The structure of an antigenic determinant in a protein

The immunogenic and antigenic determinants of a synthetic peptide and the corresponding antigenic determinants in the parent protein have been elucidated. Four determinants have been defined by reactivity of a large panel of antipeptide monoclonal antibodies with short, overlapping peptides (7-28 amino acids), the immunizing peptide (36 amino acids), and the intact parent protein (the influenza virus hemagglutinin, HA). The majority of the antipeptide antibodies that also react strongly with the intact protein recognize one specific nine amino acid sequence. This immunodominant peptide determinant is located in the subunit interface in the HA trimeric structure. The relative inaccessibility of this site implies that antibody binding to the protein is to a more unfolded HA conformation. This antigenic determinant differs from those previously described for the hemagglutinin and clearly demonstrates the ability of synthetic peptides to generate antibodies that interact with regions of the protein not immunogenic or generally accessible when the protein is the immunogen.

Proteins of the sea urchin egg vitelline layer

The vitelline layers (VL) of unfertilized sea urchin eggs were isolated, and the diversity of their polypeptide constitutents estimated by two-dimensional polyacrylamide gel electrophoresis. At least 25 components are reproducibly observed. While VL polypeptides are almost certainly synthesized in the growing oocyte, they are not among the more prevalent newly synthesized proteins detected in oocytes that were isolated and labeled in vitro for 4 hr. A set of monoclonal antibodies was raised against VL components and partially characterized. The 31 monoclonals analyzed fell into 11 classes with respect to their avidity for VL proteins solubilized under mild and under strongly denaturing conditions, and to their reactions with surface components of the VLs of living eggs. Fluorescence microscopy showed diverse patterns of surface reactivity when different monoclonal antibodies were compared. Two of the monoclonal antibodies reacted with specific sets of three proteins each on VL protein blots. It is concluded that the VL is a complex structure containing a large number of different polypeptide components, the genes for several of which should now be experimentally accessible.

Antisera to a synthetic peptide of the sis viral oncogene product recognize human platelet-derived growth factor

It has recently been reported that the sequences of the sis oncogene of simian sarcoma virus (SSV) and of human platelet-derived growth factor (PDGF) are very similar, establishing the most solid link yet between the mitogenic actions of growth factors and the transforming proteins of retroviruses. To investigate molecular mechanisms of transformation I have produced antisera against synthetic peptides corresponding to segments of the protein sequences predicted by the nucleotide sequences of viral oncogenes. Applying this approach to the case of sis and PDGF, I report here the results of probing outdated human platelets with an antiserum directed against a synthetic peptide representing residues 139-155 of the predicted sequence of the SSV transforming protein, p28sis (ref. 3). I detected peptides of apparent molecular weights (MWs) 30,000 to 31,000 (30-31K) and 16-18K, which correspond to the apparent molecular weights of nonreduced and reduced PDGF. In addition, a peptide of MW 21,000 was detected in platelets and a protein of MW 56,000 was detected in SSV-infected marmoset cells.

Monoclonal antibodies to the sea urchin egg vitelline layer inhibit fertilization by blocking sperm adhesion

Thirty-one mouse hybridomas were produced against the vitelline layer (VL) of the egg of the sea urchin S. purpuratus. Ascites fluids of eight of the 31 bound to the VL surface in the high ionic strength conditions of sea water. Binding was specific to the VL, since immunofluorescence showed that the antibodies elevated from the egg surface with the fertilization envelope after activation with ionophore A23187. Antibody binding was strictly species-specific, the eggs of L. pictus showing no reaction. An immunoperoxidase surface-binding assay showed a wide range in the amount of each monoclonal antibody binding to the VL surface at saturation. All eight monoclonals inhibit fertilization by inhibiting the binding of sperm to the VL. None of the eight ascites fluids reacted with egg jelly. The inhibition of fertilization correlates positively with amount of antibody binding the egg surface. In contrast to the effects of polyclonal rabbit antisera raised against whole eggs or egg cortices, these eight monoclonal antibodies to the VL do not induce the wrinkling of the egg, the cortical granule reaction, the centering of pronuclei, or any other visual indication of metabolic activation.

Generation of protein-reactive antibodies by short peptides is an event of high frequency: implications for the structural basis of immune recognition

Recent studies have shown that chemically synthesized small peptides can induce antibodies that often react with intact proteins regardless of their position in the folded molecule. These findings are difficult to explain in view of the experimental and theoretical data which suggest that in the absence of forces provided by the folded protein, small peptides in aqueous solution do not readily adopt stable structures. In order to rationalize the two findings, there has been general acceptance of a stochastic model which suggests that the multiple conformers of a peptide in solution induce sets of antibodies with a small percentage reactive with conformations shared by the folded protein. This stochastic model has become less tenable as the success rate for the generation of protein-reactive anti-peptide antibodies has grown. To test the stochastic model, we have used monoclonal anti-peptide antibodies as a way of estimating the frequency with which small peptides induce antibodies that react with folded proteins. We have made monoclonal antibodies to six chemically synthesized peptides from three proteins. The frequency with which the peptides induce protein-reactive antibodies is at least 4 orders of magnitude greater than expected from previous experimental work and vastly different from what would be predicted by calculating the possible number of peptide conformers in solution. These findings make the stochastic model less likely and lead to consideration of other models. Aside from their practical significance for generation of highly specific reagents, these findings may have important implications for the protein folding problem.

Monoclonal antibody recognizing gp80, a membrane glycoprotein implicated in intercellular adhesion of Dictyostelium discoideum

WE have raised a monoclonal antibody, designated E28D8, which reacts with an 80,000-dalton membrane glycoprotein (gp80) of Dictyostelium discoideum. gp80 has been implicated in the formation of the EDTA-resistant adhesions ("contact sites A") which appear during development. The monoclonal antibody reacted with other developmentally regulated proteins of D. discoideum, confirming previous results indicating the presence of common antigenic determinants recognized by polyclonal rabbit antibodies directed to gp80. Periodate sensitivity of the determinants suggests that carbohydrate may be necessary for reactivity. Thus, the determinant recognized by E28D8 may result from a posttranslational modification common to a number of proteins. Some of the proteins that carry the determinant were preferentially localized to posterior cells in slugs. Monoclonal antibody E28D8 did not inhibit contact-sites-A-mediated intercellular adhesion. However, gp80 affinity purified on immobilized monoclonal antibody was able to neutralize the adhesion-blocking effect of rabbit antiserum to gp80. Although gp80 itself may not be essential for cell-cell adhesion, it appears to carry the determinants associated with adhesion.

Chemical synthesis of a polypeptide predicted from nucleotide sequence allows detection of a new retroviral gene product

We previously determined the nucleotide sequence of the 3' end of Moloney leukaemia virus and discovered the potential coding region for an unknown protein, R. We now show that this region does encode a protein. A pentadecapeptide of R was chemically synthesized and antibodies raised against it. Antisera to the synthetic peptide recognize the R protein and the env precursor polyprotein in infected cells. The strategy presented here should provide a general method for accessing proteins predicted by nucleotide sequences.

Molecular dissection of Rauscher virus gp70 by using monoclonal antibodies: localization of acquired sequences of related envelope gene recombinants

Using hybridoma-specific immune precipitations of fragments derived from Rauscher virus gp70, coupled with peptide patterns (fingerprinting) and partial amino acid sequence analyses, we have generated a linear map of Rauscher gp70. We used a panel of 56 hybridomas derived from the fusion of the drug-selected SP-2 myeloma line with spleen cells from either a 129 GIX+ or a GIX- mouse immunized with purified Rauscher virus gp70. The results showed that by "natural" breakdown, gp70 splits into predominant fragments, with Mr 45,000 (P45), 34,000 (P34), and 32,000 (P32). Peptide fingerprinting of these as well as overlapping fragments coupled with partial amino acid sequence analyses allowed us to align the fragments into the linear arrangement NH2-P45-P32-COOH, with P34 being an NH2-terminal degradation product of P45. Of the 56 hybridomas, 20 immunoprecipitated both P45 and P34; 18 immunoprecipitated only P45; and 18 immunoprecipitated only P32. The hybridomas thus define three domains of the molecule as NH2-P45/P34, P45 only, and P32-COOH. Allowing these hybridomas to react with two Rauscher-derived envelope gene recombinant viruses yielded the following results: (i) all 20 P45/34 reactors bound to the two Rauscher recombinants; (ii) of 18 P45-only hybridomas, 10 reacted; and (iii) only 1 of 18 P32 reactors bound to the Rauscher recombinants. This last hybridoma reacted with various murine retroviruses, indicating that it was directed at conserved determinants of gp70. Peptide fingerprinting of R-gp70, the recombinant gp70s, and their respective breakdown products confirmed the homologies and nonhomologies defined by the hybridomas. Furthermore, peptide patterns showed that these acquired sequences on the COOH-terminal portion of the recombinant gp70s are related to xenotropic virus gp70s.

Endogenous RD-114 virus genome expression in malignant tissues of domestic cats

Endogenous xenotropic cat type C virus (RD-114)- and infectious feline leukemia virus (FeLV)-specific gene expressions were measured in spontaneous sarcomas carcinomas, and nonmalignant cat tissues by molecular hybridization for virus-specific RNA and competition radio-immunoassays for the major internal protein (p30) of these two viruses. The results indicate that RD-114 gene expression in sarcomas and carcinomas at both RNA and p30 levels is significantly higher than histologically normal tissues from cats free of cancer. In contrast, the levels of FeLV viral RNA and p30 are fount to be low or undetectable in the majority of these tumored and normal tissues examined. Whereas variability in the amounts of RD-114 OR FeLV RNA and p30 expressed is found in tissues from different cats, their expression is fairly uniform in multiple malignant tissues of the same cat. The finding of widespread occurrence of elevated RD-114 gene expression in sarcomas and carcinomas is consistent with our similar observation with natural lymphomas of domestic cats and suggests that expression of certain functions of this endogenous virus may be etiologically involved in the development of many different spontaneous neoplasms of cats.