Cell cycle inhibition in human BE-13 T cell leukemia cells by haptoglobin-related (HPR) antisense cDNA.

We have recently cloned and sequenced a human haptoglobin-related cDNA. Hpr expression was found in various tumor cell lines. To determine whether the haptoglobin related protein (hpr) affects the growth of an established T-cell leukemia cell line, an Hpr antisense expression vector that specifically reduces hpr production was constructed. The vector was transfected into BE-13 cells, an established T-cell leukemia cell line in which Hpr is expressed. Three stable clones were isolated in which hpr protein expression was reduced. These established cell lines proliferated more slowly than vector transfected cells in proportion to Hpr antisense mRNA expression and the reduction in hpr protein production. Following a BrdU pulse, flow cytometric analysis was performed to estimate the fraction of cells in S phase. Hpr antisense transfected cells contained less cells in S phase compared to vector transfected cells. Also in soft agar, cells expressing the antisense cDNA insert, formed on average at least 7-fold fewer colonies than cells transfected with the vector alone. The data suggest that Hpr inhibitors might be of therapeutic value for T-cell leukemia.

Haptoglobin-related protein as a serum marker in malignant lymphoma.

A novel serum 21 kDa haptoglobin-related protein (Hpr) was investigated in patients with malignant lymphoma, to evaluate its correlation with clinical and histologic features at presentation and its possible role as a tumor marker for patient outcome. One hundred fifty eight serum samples were taken from 88 patients with non-Hodgkin's lymphoma (n=58) and Hodgkin's disease (n=30) at presentation and in the course of follow-up. Sera from 61 healthy volunteers served as normal controls. Serum Hpr levels in the lymphoma patients (median 430x10 u/ml, range 0-4000x10 ) were significantly higher than in the control group (median 68x10 u/ml, range 0-180x10 )(p=0.0001). Higher median Hpr values were detected in patients with advanced disease (p=0.013), "B" symptoms (p=0.029) and in males (p=0.053). There was also a significant correlation between Hpr and erythrocyte sedimentation rate (p=0.028). Serial determinations showed a significant decrease of the initial Hpr values obtained after treatment in 41 patients, 38 of whom achieved complete remission. In the follow-up period additional Hpr measurements were taken from 17 patients. Three of them eventually relapsed, and showed increased Hpr levels at the time of relapse. Hpr levels remained low in 11 of 14 patients who maintained complete remission, and increased in three. In conclusion, serum Hpr is a new serum tumor marker of potential use in the clinical setting of lymphoma.

Transcriptionally active haptoglobin-related (Hpr) gene in hepatoma G2 and leukemia molt-4 cells.

The aim of the present study was to answer the question: Is the haptoglobin-related (Hpr) gene expressed in tumor cells? Our strategy of cloning the cDNA was to screen a human hepatoma G2 cDNA expression library in lambda gt11 using three different probes complementary to the coding strands of regions of the Hpr gene that contain codon changes permitting a discrimination from haptoglobin gene Hp1F. Among 8 x 10(5) recombinant phages screened, 2 hybridized to all three probes under stringent conditions. A 1.5 kb cDNA designated ST-1 was subcloned and sequenced. Almost total identity was found with the Hpr predicted exons 2-5, although exon 1 was missing. The ST-1 partial cDNA clone was used as a probe to screen a human leukemia molt-4 cDNA expression library in lambda gt11. Among 10(6) recombinant phages screened, 1 hybridized under stringent conditions. A 1.5 kb cDNA designated ST-2 was subcloned and sequenced. ST-1 and ST-2 cDNA were identical except for an insert of A at position 500 of ST-1 cDNA. Two different nucleotide changes were observed in the ST-1 and ST-2 sequences as compared with the expected Hpr cDNA sequence. An alternative processing of Hpr pre-mRNA was found in both cDNA clones that included 126 bp of the 3'-region of intron 1. This intronic sequence is thereby retained in the mature mRNA. cDNA analysis revealed an in-frame ATG in intron 1. Transcription/translation assay was used to demonstrate that the Hpr message could be translated from the internal methionine codon. We have thus shown for the first time that the Hpr gene is expressed in the human hepatoma G2 and leukemia molt-4 cell lines.

Alkynyl phosphates are potent inhibitors of serine enzyme.

Propynyl, hexynyl and t-butylethynyl diethyl phosphates were found to be very powerful covalent inhibitors of serine enzymes. Esterases were inhibited with second-order rate constants of 10(7)-10(8) m(-1) min(-1). Most proteases were inhibited with a rate constant of 10(4)-10(5) M(-1) min(-1). By inhibiting chymotrypsin with (3-14C)-1-propynyl diethyl phosphate, it was established that inhibition was caused by binding of the phosphate group to the enzyme active site.

Increased levels of a 21-kDa protein in the circulation of tumor-bearing patients.

A novel non-ras 21-kDa protein (p21) was detected in sera of cancer patients by enzyme-linked immunosorbent assay (ELISA), using polyclonal anti-p21 antibodies. While only 4.6% of the healthy donors (n = 43) showed p21 serum levels higher than the mean +/- 2 SD of the normal group, 33 to 80% of the cancer patients (n = 94) with various tumors were positive in the ELISA test. In particular, patients with malignant lymphoma, urogenital, and gastrointestinal tumors had a 2.8- to ninefold increase in p21 serum levels. Elevated serum levels were also found in patients with benign prostatic hyperplasia (3.2-fold increase). In 17 out of 22 patients with urogenital tumors, changes in serum p21 levels correlated with the clinical course of the disease. In 15 patients, a favorable response to therapy was correlated with a decline in serum p21 level. Two patients with renal cell carcinoma showed increased or persistently high levels of p21 after surgery and were subsequently found to have distant metastases. Expression of p21 in ten renal cell carcinoma tissues was determined by Western blotting. There was a trend toward a higher content of p21 in the less-differentiated tumor tissues. In conclusion, p21 may be a useful indicator in monitoring the outcome of treatment in patients with various malignant tumors. In patients with renal cell carcinoma, p21 serum levels may be of particular importance because no other tumor marker is available.

Characterization of DNA binding properties of Yp20: an abundant nuclear protein isolated from Saccharomyces cerevisiae.

The aim of this study was to elucidate the function of Yp20 (yeast 20 kDa protein) which is an abundant basic DNA-binding protein copurified with yeast chromatin. The work presented here shows that Yp20 is a sequence specific DNA binding protein. DNA binding activity was extremely thermostable. The affinity of binding to TRP1 was higher than the affinity of binding to the B domain of ARS1. The dissociation half time of Yp20-DNA complexes was less than 1 min. Yp20 showed no homology to a similar abundant 21 kDa ARS binding factor II (ABFII), previously described. Competitive gel retardation assays revealed two different regions that were protected by Yp20. One was overlapping the ABF1 binding site on ARS1 and another protected region was found upstream to the translational start codon of the TRP1 gene. It thus appears that Yp20 may have a role in DNA replication and/or transcription.

Analysis of a non-ras 21-kDa protein in patients with metastatic testicular germ-cell tumors.

A novel protein of 21 kDa (p21) has been detected in the sera of patients with different solid tumors. The serum levels of this p21 protein were measured in seven patients with metastatic testicular germ-cell tumors before and after chemotherapy using an enzyme-linked immunosorbent assay. In five out of six patients who responded to chemotherapy a concomitant decrease of p21 serum levels was found. The decrease of p21 was in accordance with the decline of the established tumor markers alpha-fetoprotein, human chorionic gonadotropin beta-subunit and lactate dehydrogenase in three patients with non-seminomatous tumors and with the decline of lactate dehydrogenase and the clinical response in two patients with seminoma. In one patient the predicted decline of p21 did not occur despite the patient's clinical response to chemotherapy. In the seventh patient, who relapsed directly after chemotherapy, no decline of either p21 levels or tumor markers was observed. The absolute amount of the p21 protein prior to chemotherapy did not correlate with the patients' tumor burden. Elevated levels of p21 were found in patients with seminomatous and non-seminomatous germ-cell tumors. Since seminoma patients do not secrete tumor markers like alpha-fetoprotein or human chorionic gonadotropin beta, the determination of p21 levels may help to evaluate the efficacy of chemotherapy in patients with seminomatous as well as in patients with marker-negative non-seminomatous germ-cell tumors. The biological role of p21 and its clinical significance will be further investigated.

Enzyme-linked-immunosorbent-assay for the detection of a novel 21-kda protein associated with the clinical course of patients with urogenital tumors.

A novel 21 kDa protein (p21) was detected in sera of patients with urogenital tumors by ELISA, using rabbit polyclonal antibodies generated against the p21 polypeptide. Eight out of 11 patients (72%) exhibited a 2-5 fold increase in pre-treatment p21 serum levels as compared with 20 healthy individuals. A decrease of p21 levels was observed in 6 out of 8 patients in which a regression of the disease was shown post-treatment. An increase or no change in p21 levels was observed in 3 patients with no change or progression of the disease. The ELISA described herein may be useful for clinical monitoring of patients with urogenital tumors, some of which have no available tumor marker.

A novel 21-kDa protein as a serum marker for benign and malignant urogenital tumors: preliminary communication.

A novel 21-kDa protein (p21) was isolated from auto-immune complexes, found in sera of 14 patients with malignant urogenital tumors and isolated on Protein A-Sepharose. Isolated complexes were analyzed in 15% polyacrylamide-SDS minigels. After staining with Coomassie blue R, the bands were scanned with a clinical densitometer. The level of p21 in sera of cancer patients was 3 times higher than that found in normal individuals. An attempt was made to correlate consecutive levels of p21 in the sera of these cancer patients with the clinical course. In 4 cases a significant decrease (57-75%) in the level of p21 was observed in parallel with response to treatment. In 9 of 10 cases where no response or tumor progression was observed, the relative abundance of p21 increased or remained unchanged. Thus, the level of p21 was indicative of progression or regression of the disease in 13 out of 14 patients. Similar high levels of p21 in sera were also found in 22 patients with benign hyperplasia of prostate. The p21 protein was not immunoreactive with known anti-ras antibodies such as Y13-259, 142-24E05 and anti-rap1. Partial amino acid analysis of this protein showed no complete homology to any known protein, but a partial homology to known bacterial proteins involved in DNA replication or transcription was observed. Monitoring of the novel p21 levels before and after treatment may be useful in follow-up of cancer patients, providing evidence of response to treatment.

Nuclear proteins from HeLa cells are immunoreactive with anti-yeast Yp20 ras related antibodies.

Immunoblot analysis using antibody specific to yeast ras-related protein Yp20 revealed a 21kDa protein associated with HeLa cell chromatin which immunologically cross-reacted with this ras-related protein. The 21kDa protein can be rapidly released from the HeLa nuclei by micrococcal nuclease digestion. It seems to be associated with long mononucleosomes as determined by separation of chromatin subunits on sucrose gradients. We suggest that the 21kDa HeLa protein may be the human homologue of yeast Yp20.

DNA binding properties of Saccharomyces cerevisiae chromatin associated ras-related protein Yp20.

Yp20 is an abundant 20 kDa chromatin associated protein which has been shown to be related antigenically to genuine Hras products. Using Southwestern blots we have demonstrated that Yp20 is a DNA binding protein. It is also shown that protein Yp20 like protein HM (an abundant thermostable 20 kDa DNA binding protein isolated from mitochondria) and like the 21 kDa autonomously replicating sequence binding factor II (ABFII) is able to introduce superhelical turns into circular relaxed DNA in the presence of DNA topoisomerase I activity. We suggest that this protein may be important for chromatin structure and function.

Saccharomyces cerevisiae chromatin associated protein Yp20 is a guanine nucleotide binding protein.

Yp20 is a 20kD protein whose role is still obscure which copurifies with yeast histones. Yeast histones were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and transferred to nitrocellulose. Incubation of the nitrocellulose blots with [gamma-35S] GTP gamma S demonstrated that Yp20 is a GTP binding protein. A polyclonal antiserum raised against purified Yp20 cross reacted with bacterially expressed cHras and T24 Hras genuine ras products. The results obtained suggest that Yp20 is a yeast chromatin associated ras-related antigen.

Yeast as source of oncoproteins.

The properties of a Saccharomyces cerevisiae 20 kDa polypeptide (Yp20) and its relationship to human ras antigen were tested. Yp20 was isolated from commercial yeast cells by the procedure of Sommer (1978). Proteins associated with yeast chromatin were released by micrococcal nuclease digestion and purified by sucrose gradient centrifugation. Rabbit polyclonal and mouse monoclonal antibodies specifically detecting the Yp20 antigen have been generated. We observed that Yp20 was recognized by anti-ras polyclonal and monoclonal antibodies. Mammalian Ha-ras and Ki-ras proteins were specifically detected by anti-Yp20 antibodies. Based on immunological cross-reactivities, we believe that Yp20 may share some homology with the yeast YP2 gene previously described. Anti-Yp20 antibodies will be used to isolate the gene that encodes the protein. Practical applications of our antibodies for the detection of tumor specific antigens will be discussed.

Competitive ELISA for detection of native ras gene-related products in sera of cancer patients.

A solid phase, enzyme-linked immunosorbent assay (ELISA) competition kit was developed to detect circulating native ras gene-related products in sera of 151 healthy volunteers and cancer patients. This assay uses monoclonal antibody (mAb) BST-6A generated against a yeast-derived, native ras-related polypeptide Yp20. Only 2% (1 of 58) of normal control sera showed strong competition, as compared to 15% (5 of 34) of patients with early stage or no evidence of disease, and 44% (26 of 59) of patients with advanced disease. These differences were statistically significant (x2, P less than 0.05-0.001). Eleven sera samples of cancer patients found to be strong competitors in the ELISA competition kit were tested for the presence of anti-ras antibodies by ELISA. None showed higher ELISA values as compared with pooled normal human serum and control sera. It is thus suggested that our procedure detected circulating ras-related onco-proteins in sera of cancer patients mainly with advanced disease.

A yeast-derived ras-gene-related protein expressed in human tumor cells. I. Detection by polyclonal antibodies.

Rabbit polyclonal antibodies (pAb) were raised against a yeast ras-related protein YP20 and shown to be immunoreactive with human normal as well as altered Ha-ras and Ki-ras p21 gene products using immunoblotting and immunoprecipitation techniques. The p21 protein revealed by anti-YP20 antibodies comigrates with p21 protein detected by anti-p21 monoclonal antibody (Cetus Diagnostics). These pAbs were tested against a panel of human acetone-fixed tumor cell lines and malignant effusions and nonfixed fresh-frozen tissue sections obtained from cancer patients by the indirect immunofluorescence assay (IFA). Twelve of sixteen (75%) sarcoma and carcinoma cells lines and one fibroblast cell line were stained by the anti-YP20 pAb. The binding occurred most commonly in the cytoplasm. Six of eight fresh-frozen colon and breast cancer tissue sections were immunostained and normal sections from these organs or skin showed only low level of binding to the pAbs. Four of five malignant effusions were distinctively immunostained. These antibodies are suggested to serve as additional probes for assessing the expression of ras gene-related proteins in human malignancy.

Spermidine inhibits degradation of yeast chromatin.

A procedure has been developed for the isolation of intact yeast chromatin from yeast nuclei. Autodigestion of chromatin observed during nuclear preparation was inhibited by the addition of 5 mM spermidine. The procedure is useful for the analysis of proteins associated with yeast chromatin.

An improved isolation procedure for yeast two-micrometer minichromosomes.

Two micrometer minichromosomes from Saccharomyces cerevisiae were isolated without detergent using metrizamide gradients. 2 µm minichromosomes showed a lower density in metrizamide gradients relative to genomic chromatin. Our results suggest a lower ratio of proteins to DNA in 2-µm minichromosomes as compared with genomic chromatin. The procedure described herein yields minichromosomes free of cellular chromatin and ribosomal protein contamination. This method may be useful for the isolation and characterization of other yeast minichromosomes.

Killer double-stranded ribonucleic acid synthesis in cell division cycle mutants of Saccharomyces cerevisiae.

The synthesis of killer double-stranded ribonucleic acid (dsRNA) in Saccharomyces cerevisiae was examined in seven different cell division cycle mutants (cdc) that are defective in nuclear deoxyribonucleic acid replication and contain the "killer character." In cdc28, cdc4, and cdc7, which are defective in the initiation of nuclear deoxyribonucleic acid synthesis, and in cdc23 or in cdc14, defective in medial or late nuclear division, an overproduction of dsRNA at the restrictive temperature was observed. In contrast to the above mutants, the synthesis of killer dsRNA is not enhanced at the restrictive temperature in either cdc8 or cdc21, which are defective in deoxyribonucleic acid chain elongation. Examination of killer sensitive strains (cdc7 K- and cdc4 K-) has shown that the complete killer dsRNA genome is essential for the overproduction of dsRNA at the restrictive temperature.

Increased synthesis of abundant poly(A)-containing RNA in a DNA defective mutant of Saccharomyces cerevisiae containing the "killer character".

A Saccharomyces cerevisiae strain which contains both the "killer character" and a ts mutation in the initiation of nuclear DNA synthesis (cdc4) was studied. Incubation of this strain at the restrictive temperature caused a 3--4 fold increase in the relative rate of synthesis of abundant RNA which contains poly(A) and a 2--3-fold increase in the relative rate of synthesis of killer dsRNA. Thus, the amount of killer dsRNA found in these cells seems to be correlated to the amount of abundant poly(A)-RNA.

Abundant species of poly(A)-containing RNA from Saccharomyces cerevisiae.

Hybridization experiments using uniformly labeled poly(A) RNA derived from Saccharomyces cerevisiae strains carrying the "killer character" showed that (1) these molecules appear to be transcribed from repetitive DNA sequences. (2) there are approximately 35 DNA template sequences that are transcribed into poly(A) RNA. It is concluded that under the RNA extraction procedure used, most of the poly (A) RNA represents killer-RNA as judged by the dependence of the kinetic complexity of poly(A) RNA on the genomic complexity of killer-RNA.