Biologic markers in risk assessment for environmental carcinogens

The potential of biologic markers to provide more timely and precise risk assessments for environmental carcinogens is viewed against the current state-of-the-art in biological monitoring/molecular epidemiology. Biologic markers such as carcinogen-DNA adducts and oncogene activation are currently considered valid qualitative indicators of potential risk, but for most chemical exposures research is needed to establish their validity as quantitative predictors of cancer risk. Biologic markers have, however, already provided valuable insights into the magnitude of interindividual variation in response to carcinogenic exposures, with major implications for risk assessment.

Induction of carcinoembryonic-antigen-gene expression in human colorectal carcinoma by sodium butyrate

The effect of sodium butyrate on the expression of the carcinoembryonic-antigen (CEA) gene was studied in two poorly differentiated colorectal-carcinoma cell lines (Clone-A and MIP-101) and in one well-differentiated cell line (LS-174T); A.T.C.C. no. CCL 188). Northern-blot and dot-blot analyses indicated a steady increase in CEA mRNA from day 4 to a maximal level by day 14 after these cells were exposed to 2 mM-sodium butyrate. Studies using nuclear run-off assays followed by dot-blot hybridization to a partial CEA cDNA clone demonstrated that specific increases in gene transcription rates (3-fold in MIP-101, 4-fold in LS-174T and 6-fold in Clone-A) are not sufficient to account for the observed increases in CEA mRNA abundance. Further studies showed that CEA-specific transcripts have a half-life of about 60-80 min, and treatment with sodium butyrate increased the stability of CEA-specific transcripts to about 340 min in LS-174T cells and to about 500 min in Clone-A cells. We conclude that the induction of the CEA-gene expression by sodium butyrate in colorectal-cancer cells is mediated by both transcriptional and post-transcriptional mechanisms, with CEA mRNA stability as one of the major check-points.

Inhibition of PC-12 cell differentiation by the immediate early gene fra-1

The rat pheochromocytoma cell line (PC-12) offers a powerful in vitro model to study the mechanism of growth factor-induced differentiation and proliferation. Within minutes of addition, agents such as nerve growth factor (NGF), epidermal growth factor (EGF), basic fibroblast growth factor (bFGF) and dibutyryl cyclic AMP (db cAMP) rapidly activate cellular immediate early genes such as c-fos, c-jun, jun-B, and egr-1. fra-1, a member of the immediate early gene family, follows a distinctly later time course of induction than c-fos, c-jun, jun-B, and egr-1, suggesting that fra-1 may attenuate the action of genes induced earlier. We demonstrate that constitutive expression of fra-1 in PC-12 cells results in pronounced inhibition of NGF-induced differentiation. Transcriptional activation of c-fos, c-jun, jun-B, and egr-1 by NGF, EGF, and db cAMP was down-regulated to a varying extent whereas NGF-induced ornithine decarboxylase (ODC) was not affected. Expression of jun-D was not affected in PC-12 fra-1 cells. Transfection of fos and egr-1 promoter-chloramphenicol acetyl transferase (CAT) plasmid into these stable fra-1-expressing PC-12 cells revealed that repression of fos and egr-1 was exerted at the promoter level. Thus deregulated fra-1 expression may inhibit PC-12 cell differentiation by altering the patterns of immediate early gene expression.

Induction of plasminogen activator inhibitor type 2 expression during differentiation of human K562 cells towards a macrophage phenotype

Human K562 cells, a multipotential cell line of hematopoietic origin, were found to differentiate towards a macrophage-like cell when incubated in the presence of phorbol myristate acetate (PMA). Differentiation was accompanied by the expression and secretion of a plasminogen activator inhibitor (PAI). Incubation of the cells in the presence of other agents (dimethyl sulfoxide, retinoic acid, vitamin D3) capable of inducing differentiation towards other phenotypes did not lead to the induction of PAI expression. The inhibitor induced by PMA was partially purified and it exhibited biochemical characteristics similar to PAI-2. The molecule is a glycoprotein with a pI of 5.8. Northern blot analysis of mRNA isolated from control and PMA-treated cells revealed the presence of an approximately 2-kilobase mRNA from treated cells that hybridized to a PAI-2-specific synthetic oligonucleotide. This mRNA did not hybridize with a PAI-I-specific oligonucleotide and was absent from control cells. These observations are consistent with the literature regarding PAI-2 expression by cells of the monocyte-macrophage lineage. Therefore, commitment of this multipotential cell line towards the macrophage lineage results in specific activation of the PAI-2 gene. Further analysis of the regulatory elements of the PAI-2 gene may provide additional insight into the relationship between this gene and the macrophage phenotype.

Cyclosporin A suppresses cisplatin-induced oncogene expression in human cancer cells

Most cancer chemotherapeutic agents are designed to damage DNA directly or indirectly. One mechanism of cellular resistance to these agents is enhanced DNA repair. Human ovarian carcinoma cells resistant to cisplatin (A2780DDP) respond to cisplatin treatment with a 3-6-fold increase in gene expression for oncogenes, DNA repair enzymes and enzymes necessary for the synthesis of thymidine. Cyclosporin A has been shown to reverse drug resistance, but its mechanism of action is unclear. In this study, weekly exposures of A2780DDP cells to cyclosporin A resulted in the evolution of a revertant cell line A2780DDP/CSA that was sensitive to cisplatin again and suppressed the induction of genes necessary for the repair of drug-induced DNA damage.

Modulation of tPA, PAI-1 and PAI-2 antigen and mRNA levels by EGF in the A431 cell line

It has been reported that EGF treatment enhances uPA but not tPA in the A431 epidermoid carcinoma cell line. To determine whether the absence of tPA modulation by EGF could be due to the action of inhibitors, we assayed tPA, PAI-1, PAI-2 and tPA/PAI-1 complexes by immunological assays and zymography in A431 serum-free medium. We found that, under conditions in which EGF had no effect on tPA activity, tPA antigen increased with a concomitant rise of tPA/PAI-1 complexes, indicating the action of an inhibitor. Both tPA antigen and tPA/PAI-1 complexes were modulated by EGF in a time and concentration dependent manner. tPA/PAI-1 complex levels were lower than tPA levels, suggesting the presence of other inhibitors. Immunological assays detected PAI-2 in addition to PAI-1 and showed a time and dose response to EGF. Modulation of tPA and the anti-activators by the growth factor was confirmed by identification of the corresponding transcripts with cDNA probes. We conclude that the net plasminogen activator activity in A431 cells is the result of a balance between activators and inhibitors.

Inhibitory effects of fucoxanthin, a natural carotenoid, on N-myc expression and cell cycle progression in human malignant tumor cells

Fucoxanthin, a natural carotenoid prepared from brown algae, inhibited the growth of GOTO cells, a human neuroblastoma cell line. Fucoxanthin at 10 micrograms/ml reduced the growth rate of GOTO cells to 38% of the control at day 3 after drug treatment. Flowcytometric analysis revealed that fucoxanthin caused the arrest in the G0-G1 phase of cell cycle. Expression of N-myc gene was proved to be decreased by fucoxanthin as early as 4 h after treatment at 10 micrograms/ml and that may be important for the mechanism of anti-proliferative action of the carotenoid.

Regulation of Ki-ras expression in Reuber H35 cells

Glucagon at a low concentration has a stimulatory effect on Ki-ras expression, whereas, at high concentrations the hormone suppresses the level of the Ki-ras transcripts. Incubation of the hepatoma cells with 10 microM dibutyryl cyclic AMP results in suppression of Ki-ras expression but the phorbol ester, 21-O-tetradecanoylphorbol 13-acetate (TPA) causes an increase. Down regulation of protein kinase C by prolonged exposure of hepatoma cells to TPA causes a dramatic decrease in the glucagon-stimulated effect on Ki-ras expression. The presence of diacylglycerol for 2 h in the culture medium results in a significant increase in Ki-ras expression, while treatment of the cells with 1-(5-isoquinolinylsulphonyl)-2-methylpiperazine, a potent inhibitor of protein kinase C, leads to a dramatic reduction. The calcium ionophore, A23187 is able to stimulate Ki-ras expression, whereas, addition of verapamil or EGTA results in its suppression. The present findings suggest that the inductive effect of glucagon on Ki-ras expression at low concentrations is via the activation of protein kinase C which causes phosphorylation of some regulatory proteins that may eventually affect the level of Ki-ras mRNA. The suppressive effect of glucagon at higher concentrations is via an increase in cAMP through activation of adenylate cyclase.

Role of the maternal environment in determining susceptibility to transplacentally induced chemical carcinogenesis in mouse fetuses

Treatment of pregnant mice with 3-methylcholanthrene (MC) causes lung and liver tumors in the offspring, the incidences of which are greatly influenced by the Ah locus regulated induction phenotype for aryl hydrocarbon hydroxylase activity (AHH) in both the mother and fetuses. In order to examine the biochemical and molecular mechanisms responsible for the modulating effect of maternal environment on tumor susceptibility, reciprocal crosses between responsive C57BL/6 and non-responsive DBA/2 mice were made and the pregnant mothers were treated i.p. on the 17th day of gestation with either olive oil alone, 30 mg/kg of MC, or 30 mg/kg of beta-naphthoflavone (beta NF). At various times after injection, the mothers were killed and the fetuses removed for enzymatic and molecular blot analysis. In fetal lung tissues, the absolute levels and relative induction ratios of AHH activity from D2B6F1 fetuses were very similar to those obtained in B6D2F1 fetuses during the first 24 h following a transplacental exposure to either inducing agent. This was also the case 48 h after an injection of beta NF. However, 48 h after exposure to MC, the AHH activity in fetal lungs from B6 mothers had declined to practically control values, whereas fetal lungs from D2 mothers still exhibited a high level of AHH activity. Similar induction kinetics for the CYPIA1 gene were obtained in fetal livers. These results were confirmed at the RNA level by quantitative slot-blot analysis of fetal RNA preparations. In both organs, treatment with inducing agents for the P450IA1 gene resulted in a rapid and early induction of CYPIA1 RNA by 4 h. Fetuses from D2 mothers, however, showed a more sustained induction of CYPIA1 RNA following exposure to MC than did fetuses from B6 mothers. These results suggest that the observed increase in tumor susceptibility observed in the offspring of D2 mothers compared to the offspring of B6 mothers was due, at least in part, to the differences in the persistence of induction of the CYPIA1 gene locus, and may be the result of differences in the clearance rates of MC from the fetal and maternal compartments or its pharmacokinetic distribution in the two types of maternal environments.

Novel NGF-induced proteins in PC12 cells: immunological evidence for their presence in brain nerve endings using a single monoclonal antibody

A monoclonal antibody, S-11D9, detected a group of novel polypeptides whose expression was induced 6 hr after incubation of PC12 cells with nerve growth factor. The antigens also were visualized by immune precipitation and Western blotting in synaptic vesicles, clathrin-coated vesicles, and synaptic plasma membrane prepared from bovine brain. A large polypeptide was detected on the synaptic plasma membrane; an intermediate size protein was visualized on the plasma membrane and on both synaptic and clathrin-coated vesicles, while a smaller molecule was found only on brain Golgi-enriched membrane preparations. Immunofluorescence labeling with S-11D9 on nerve growth factor-stimulated PC12 cells showed the antigens distributed in the cytoplasm and concentrated in discrete areas on the tip of most neurites. The particular distribution of these proteins in vesicles and synaptic plasma membrane and the finding that the different antigens share a common epitope recognized by a single monoclonal antibody open the possibility that these molecules are related markers for organelle transport pathways in nerve cells.

Gamma-interferon reduces expression of the protooncogene c-erbB-2 in human ovarian carcinoma cells

The overexpression of the protooncogene c-erbB-2 (HER-2/neu) in ovarian and mammary carcinoma is an important indicator for a bad prognosis. In this study we demonstrate that, in three of four ovarian carcinoma cell lines, there is a gamma-interferon-mediated reduction in c-erbB-2 specific protein, and this effect was found to correlate with the antiproliferative action. It is interesting to note that there is no relation between the absolute amount of c-erbB-2 protein expressed and the sensitivity of the ovarian carcinoma cells for an antiproliferative activity of gamma-interferon. Other chemotherapeutic agents did not affect c-erbB-2 expression, although they inhibited the proliferation. The oncogene expression was lowered only in the ovarian carcinoma cell lines and not in three gamma-interferon-sensitive human breast cancer cell lines. Expression of the oncogene c-erbB-2 is the leading prognostic factor in ovarian cancer. Its modulation might represent a mechanism by which gamma-interferon inhibits cell proliferation.

Changes in PC12 cell morphology induced by transfection with 42C cDNA, coding for a member of the S-100 protein family

The cloned DNA coding for 42C protein (light chain of calpactin I), whose mRNA is induced in PC12 cells by treatment with nerve growth factor (NGF), was reintroduced into these cells. A cell line was obtained in which the outgrowth of processes in the absence of added NGF, similar to that induced in the parental PC12 cells by the factor, was accompanied by high levels of 42C RNA. The apparent reason for this constitutive overexpression of 42C is the stable integration of multiple copies of the 42C DNA into the cell genome. These results further support the notion that S-100 protein family, of which 42C is a member, may play an important role in development.

Decreased expressions of c-myc and H-ras oncogenes in vitamin E succinate induced morphologically differentiated murine B-16 melanoma cells in culture

Treatment of B-16 melanoma cells in culture with d-alpha-tocopheryl succinate (vitamin E succinate) at concentrations of 11.3 and 15.1 microM inhibited growth and induced cell differentiation in culture. Vitamin E succinate treatment decreased the levels of c-myc and H-ras specific mRNAs in melanoma cells. Similar results were obtained by the vitamin retinoic acid and the nonvitamin agents R020-1724 (4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone), an inhibitor of cyclic nucleotide phosphodiesterase (0.72 mM), and sodium butyrate (1 mM), which induced differentiation and (or) inhibited growth of melanoma cells in culture. The extent of inhibition of c-myc mRNA was greater than that of H-ras mRNA. These results indicate that vitamin E succinate induced reduction of the levels of c-myc and H-ras mRNAs is related to growth inhibition of melanoma cells in culture.

Opposite effects of estrogen and the progestin R5020 on cell proliferation and GCDFP-15 expression in ZR-75-1 human breast cancer cells

We have recently demonstrated that physiological concentrations of androgens caused a marked inhibition of basal and 17 beta-estradiol (E2)-induced cell growth in ZR-75-1 human breast cancer cells. Moreover, these steroids exert effects on GCDFP-15 (gross cystic disease fluid protein-15) expression that are opposite to their above-indicated actions on cell proliferation. The synthetic progestin R5020 (17.21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione), on the other hand, causes a potent inhibition of E2-induced ZR-75-1 cell growth. In order to further characterize the hormonal regulation of GCDFP-15 expression and to better understand the antagonism between progestin and estrogen action in breast cancer cells, we have studied the effect of R5020 on both GCDFP-15 expression and cell growth in ZR-75-1 cells. After a 10-day incubation, the 4-fold stimulatory effect of 1 nM E2 on cell growth was 60% decreased by maximal effective concentrations of R5020 (greater than 1 nM) while, in the absence of E2, R5020 had no effect. The mitogenic action of E2 was accompanied by a 75% inhibition of GCDFP-15 secretion while nanomolar concentrations of R5020 induced 1.4- and 5.2-fold increases in GCDFP-15 secretion in control and E2-treated ZR-75-1 cells, respectively. While E2 caused a marked inhibition of GCDFP-15 mRNA levels, R5020 induced a maximal 2- to 3-fold increase (above control) in GCDFP-15 mRNA accumulation in cells simultaneously incubated with E2.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative analysis of CD5 antigen modulation by 12-O-tetradecanoylphorbol-13-acetate in T-lymphoblastic leukemia cells: individual response patterns and their relationships with both maturation and protein kinase C content

Modulation of CD5 expression by TPA was investigated on T-leukemic cell lines corresponding to different stages of ontogeny. These CD5 changes have been analyzed simultaneously with modifications of cell growth, cell cycle, cell surface phenotype, and PKC content. CD5 expression was found 6- to 17-fold increased by TPA in a dose-dependent manner on phenotypically mature T-cells (Jurkat, JM, and T-CLL) while T-cells from earlier stages of differentiation (CEM III, CEM 95, and CEM 44) were found unresponsive. CD5 upregulation on TPA-sensitive JM cells appears correlated with inhibition of cell growth, blockage in G1 phase, and phenotypic maturation (downregulation of CD7 and CD1 antigens) and seemed to be related to PKC activation since DiC8 (a PKC activator) mimicked this TPA effect and H7 (a PKC inhibitor) partially reduced it. On the other hand, on CEM III cells TPA induced no modulation of CD5 antigen, a less dramatic effect on cell growth and cell cycle, but a CD7 downregulation. TPA appeared fully effective in binding and translocating PKC in both CEM III and JM cells, although the PKC activity level was three times higher in the latter. Finally, our study suggests that CD5 expression is at least partially under control of PKC in phenotypically mature neoplastic T-cells while PKC could not be directly involved in the regulation of CD5 antigen in leukemic cells arrested at earlier stages of differentiation.

Antisense inhibition of single copy N-myc expression results in decreased cell growth without reduction of c-myc protein in a neuroepithelioma cell line

The N-myc gene is transiently expressed during normal embryonic development and abnormally expressed in several tumors of neuroendocrine origin. Little is known of the function of the N-myc gene product in either normal or neoplastic tissue. We utilized synthetic antisense oligodeoxynucleotides to specifically inhibit N-myc gene expression in the neuroepithelioma cell line CHP100. These cells contain single copy N-myc alleles but overexpress c-myc. N-myc antisense oligomer treatment was found to be growth inhibitory without affecting levels of c-myc protein. N-myc antisense oligomer-treated cells also lost the characteristic cellular heterogeneity displayed by CHP100 in vitro.

Induction of differentiation of the human histiocytic lymphoma cell line U937 in the absence of vimentin expression

We have studied the expression of vimentin in the human histiocytic lymphoma cell line U937, induced to differentiate along the monocyte/macrophage pathway. Normal monocytes possess a network of vimentin intermediate filaments (IFs) at all stages of maturation. The undifferentiated U937 leukemia cells contain very low amounts of vimentin, but express a conspicuous IF network when exposed to phorbol myristate acetate. In parallel, they acquire functional properties typical of cells of the monocyte lineage. These concomitant variations suggest that vimentin IFs could play a role in the process of differentiation. However, we observed that all-trans-retinoic acid and 1,25-dihydroxyvitamin D3 confer monocyte-like properties upon U937 cells without inducing vimentin expression. We obtained increased phenotypic changes, yet in the absence of a vimentin network, by combining the effects of both inducers. These results show that vimentin expression is not crucial for the acquisition of some of the functions characteristic of the monocyte/macrophage lineage.

Regulation of jun-B gene expression by 1-beta-D-arabinofuranosyl-cytosine in human myeloid leukemia cells

The jun-B gene is a member of the jun family of immediate early response genes that regulate cellular responses to growth factors. The present studies have examined the effects of 1-beta-D-arabinofuranosylcytosine (ara-C) on jun-B expression in human KG-1 myeloid leukemia cells. The results demonstrate that ara-C increases jun-B mRNA levels. The level of jun-B transcripts was maximal after 12 hr of exposure to 10(-5) M ara-C and persisted through 72 hr. Nuclear run-on assays demonstrated that ara-C treatment is associated with an increased rate of jun-B gene transcription. The results also demonstrate that ara-C-induced jun-B mRNA levels are regulated by a posttranscriptional mechanism. The level of jun-B transcripts in ara-C-treated cells was superinduced by inhibition of protein synthesis. Moreover, cycloheximide prolonged the half-life of ara-C-induced jun-B transcripts. These results, thus, demonstrate that ara-C induces expression of the jun-B gene in KG-1 cells and that this effect is mediated by transcriptional and posttranscriptional mechanisms.

Gonadotropin-releasing hormone regulates gonadotropin beta-subunit and chromogranin-B messenger ribonucleic acids in cultured chromogranin-A-positive pituitary adenomas

Chromogranin-A-positive pituitary adenomas include glycoprotein hormone-producing adenomas, null cell adenomas, and a few other pituitary adenomas. We studied the effects of GnRH, CRF, dexamethasone, and phorbol 12-myristate 13-acetate on FSH and LH secretion and on FSH beta and chromogranin-A and -B mRNA expression in 10 chromogranin-A-positive adenomas in vitro to analyze the regulation of FSH and chromogranin-A and -B expression in these neoplasms. Most adenomas responded to GnRH stimulation during 7 days in culture with a 2- to 10-fold increase in FSH and LH secretion and a 2- to 7-fold increase in FSH beta mRNA compared to control values. CRF and phorbol 12-myristate 13-acetate also stimulated FSH and LH secretion 2- to 5-fold in five of seven and three of three cases, respectively, during 7 days in culture. Dexamethasone stimulated both FSH and LH secretion in two of three cases as well as FSH beta mRNA in vitro in the one case examined. GnRH treatment consistently produced a 2-fold increase in chromogranin-B mRNA, but not in chromogranin-A mRNA, after 7 days of culture. These results indicate that many chromogranin-A-positive adenomas respond to GnRH and CRF in vitro by increased hormone secretion and that GnRH stimulation leads to increased amounts of FSH beta and chromogranin-B mRNAs. The differential response of chromogranin-A and -B mRNAs after GnRH stimulation indicates that the chromogranin genes are highly regulated in these tumors.

Inhibitory effect of the somatostatin analog octreotide on rat pituitary tumor cell (GH3) proliferation in vitro

The effects of somatostatin-14 (SS-14) and the somatostatin-analog octreotide (SMS 201-995, Sandostatin) on proliferation of GH3 pituitary tumor cells were investigated in vitro. SMS 201-995 exerted a significant, but transient, inhibition on GH3 cell growth which reached a maximum at 24 h and was no longer detectable at 48 h. The concentration that evoked the strongest inhibitory effect was 10 nM SMS 201-995, while lower and higher doses resulted in a less pronounced effect. The inhibitory effect SMS 201-995 exerted on cell proliferation was associated with a dose- and time-related reduction in both c-myc and c-fos mRNA levels. SS-14 had no noteworthy influence on either cell proliferation or c-myc and c-fos protooncogene expression. These data demonstrate that SS-analogs transiently inhibit pituitary tumor cell proliferation in vitro.

Phorbol ester treatment down-regulates immunoglobulin RNA steady-state levels in B type chronic lymphocytic leukemia and non-Hodgkin's lymphoma cells

The human B-lymphoma cell lines BJAB and Daudi, as well as the human pre-B cell line KM3, were found to down-regulate steady-state immunoglobulin RNA levels 2- to 4-fold after stimulation with phorbol 12-myristate-13-acetate (PMA) for 24 hr. No down-regulation of the transcriptional rate of a kappa promoter could be observed in any of these cell lines upon transient expression transfection. The observed down-regulation of steady-state immunoglobulin RNA affected both the secretory and the membrane form of the mu transcript equally. When freshly isolated chronic lymphocytic leukemia (CLL) cells where tested for their response to PMA, three of four isolates responded by down-regulating their steady-state immunoglobulin RNA levels.

Microgravity decreases c-fos induction and serum response element activity

Several studies have shown that altered gravity conditions influence mammalian cell growth and differentiation. The molecular mechanisms underlying these effects, however, remain relatively obscure. In this paper we show that microgravity reached in a sounding rocket strongly decreases epidermal growth factor (EGF)-induced expression of the proto-oncogenes c-fos and c-jun, which are both implicated in the regulation of proliferation and differentiation. Decreased activity of the serum response element (SRE), present in the c-fos promoter-enhancer region, is probably responsible for the decrease in EGF-induced c-fos expression. In addition, we show that gravity alterations differentially modulate distinctive signal transduction pathways, indicating that gravity-dependent modulations of mammalian cell proliferation are unlikely to be caused by a nonspecific stress response of the cell.

Molecular biology of type A endogenous retrovirus

Intracisternal A particles (IAPs) are retrovirus-like structures consistently observable in a variety of mouse tumor cells such as myeloma and hybridoma and in early embryonic cells derived from rodents but nothing is known of their infectivity. Mouse IAPs contain a gag-like protein, a reverse transcriptase and a polyadenylated RNA molecule (IAP RNA). DNA sequences complementary to IAP RNA (IAP genome) are interspersedly present in rodent such as mice, rats, Chinese hamsters and Syrian hamsters at several hundred to a thousand copies per haploid genome. Molecularly cloned IAP genomes from two species Mus and Syrian hamster were 6 to 8 kb in length with LTRs of about 0.4 kb long. The nucleotide sequence of the Syrian hamster IAP genome, H18, predicted a typical LTR-gag-prt-pol-env-LTR structure, although many stop codons were present in the region corresponding to env. The comparison of the deduced amino acid sequences of the pol region showed IAP (type A), mouse mammary tumor virus (MMTV) (type B), and squirrel monkey retrovirus (SMRV) (type D) genomes to be closely related. By using a DNA fragment encoding the pol region of the Syrian hamster IAP genome, human endogenous retroviruses termed HERV-K, were cloned from a fetal human liver gene library. Typical HERV-K genome was 9.5 kb in length having LTRs of about 1.0 kb. The HERV-K provirus could encode gag (666 codons), prt (334 codons), pol (937 codons), and env (618 codons) genes. HERV-K was shown to be closely related to types A, B and D retroviruses. The HERV-K genomes are present at about 50 copies per haploid human genome. In several human tumor cell lines, the HERV-K genome was expressed as 8.8 kb poly(A)+ RNA which appeared to be a full-size transcript of this genome. In the human breast cancer cell line T47D, stimulation of HERV-K genome expression was observed following female steroids treatment. In a detailed investigation on the organization of HERV-K proviruses in human genome, we found repetitive sequences homologous to the LTR region of the HERV-K genome. They were about 630 bp in length with an A rich tail at 3' end and found to be a SINE type nonviral retroposon. These elements were present at 4,000 to 5,000 copies per haploid human genome.

Expression of P0- and P3-RNA from the normal and translocated c-myc allele in Burkitt's lymphoma cells

We have studied the allele specific expression of c-myc P0- and P3-RNA in Burkitt's lymphoma (BL) cells. The steady state levels of P0-RNA show considerable variations in BL cells. Expression of P0-RNA was found to be restricted to the translocated allele, but could be induced by TPA from the normal allele. P0-transcription was particularly sensitive to inhibitors of protein synthesis compared to expression of P1-, P2- and P3-RNA. Transcription of P3-RNA is initiated in the first intron of the c-myc gene and has previously been described to be specific for translocated c-myc alleles in BL cells broken within exon 1 or intron 1. Here we show that P3-RNA is also expressed from an unrearranged c-myc gene. In the BL cell line Raji, substantial amounts of c-myc RNA are derived from the P3-promoter of the normal allele. This indicates that repression of the normal allele in BL cells does not include the P3-promoter. The potential coding capacity of P3-RNA is discussed.

Different regulation of mid-size neurofilament and N-myc mRNA expression during neuroblastoma cell differentiation induced by retinoic acid

1. Neuroblastoma (NB) is an unusual neuroectodermal tumor showing a high degree of spontaneous regression. NB cells can be induced to differentiate in vitro by various agents. Cell differentiation results in morphological changes characteristic of the mature neuronal phenotype, including outgrowth of neurite-like structures with several interconnections. 2. Recent experiments indicate that morphological differentiation of NB cells is associated with changes in expression of N-myc, c-myc, and c-myb oncogenes and synthesis of neurofilament proteins. However, little is known about the transcription of neurofilament genes during differentiation. 3. We have analyzed the expression of both the N-myc oncogene and mid-size neurofilament (NF) genes in the LAN-1 human NB cell line, cultured in the presence of retinoic acid (RA). Continuous treatment with RA induced morphological differentiation within 5-6 days. The transcription of N-myc was down-modulated within 24 hr of the initial exposure to RA. The mid-size NF mRNA was increased at this time. The expression of N-myc was not modified in serum-deprived LAN-1 cells, indicating that N-myc transcription is unaffected by the arrest of the cells in the G1 phase. 4. We conclude that new synthesis of mid-size NF mRNA and a decrease in N-myc transcription precede de novo formation of neurite-like processes and morphological cell differentiation of neuroblastoma cells.

Aristolochic acid activates ras genes in rat tumors at deoxyadenosine residues

Aristolochic acid I (AAI), a nitrophenanthrene derivative, is the major component of the carcinogenic plant extract aristolochic acid, which has been used as a medicine since antiquity. Long term oral administration of AAI to male Wistar rats induces multiple tumors, mainly in the forestomach, ear duct, and small intestine. The presence of activated transforming genes was investigated in various tumors of 18 AAI treated rats, namely in 14 squamous cell carcinomas of the forestomach, 7 squamous cell carcinomas of the ear duct, 8 tumors of the small intestine, 3 tumors of the pancreas, 1 adenocarcinoma of the kidney, 1 lymphoma, and 2 metastases in the lung and the pancreas. By utilizing the tumorigenicity assay and Southern blot analysis, we have detected an activated c-Ha-ras gene in the DNAs of 5 of 5 squamous cell carcinomas of the forestomach. Direct sequencing of amplified material revealed an AT----TA transversion mutation at the second position of codon 61 of the c-Ha-ras gene (CAA to CTA) in all transfectants as well as in the 5 original rat tumors. Enzymatic amplification of ras sequences followed by selective oligonucleotide hybridization detected identical mutations in 93% (13 of 14) of forestomach tumors, in 100% (7 of 7) of ear duct tumors, and in the lung metastasis. Among those tumors tested, we had 4 cases in which the forestomach tumors and the ear duct tumors originated from the same rat, showing the same mutation in both tissues. Moreover, similar mutations were demonstrated at c-Ki-ras codon 61 in 1 of 7 ear duct tumors (CAA to CAT) and in 1 of 8 tumors of the small intestine (CAA to CTA) as well as at c-N-ras 61 (CAA to CTA) in a pancreatic metastasis. Additional transfection experiments of some tumors scoring negative for ras gene mutations in dot blot analyses revealed a CAA to CTA transversion at codon 61 of the c-Ha-ras gene in 1 forestomach tumor as well as at codon 61 of the c-N-ras in 1 hyperplasia of the pancreas and in 1 lymphoma. The apparent selectivity for mutations at adenine residues in AAI induced tumors is consistent with the identification of an N6-deoxyadenosine-AAI adduct formed by reaction of AAI with DNA in vitro, suggesting that carcinogen-deoxyadenosine adducts are the critical lesions in the tumor initiation by aristolochic acid.

Synergistic effect of recombinant human leukemia inhibitory factor (LIF) and 1-beta-D-arabinofuranosylcytosine (Ara-C) on proto-oncogene expression and induction of differentiation in human U 937 cells

The in vitro action of recombinant human leukemia inhibitory factor (LIF) and 1-beta-D arabinofuranosylcytosine (ara-C) was studied on the human leukemia cell line U 937. Parameters investigated included monitoring of transcript levels of the proto-oncogenes C-MYC, C-FOS, and C-FMS, and analysis of nitroblue tetrazolium (NBT) reduction and of surface expression of the C3 bi receptor. Furthermore clonal proliferation of U 937 cells was assessed in soft agar cultures. The results indicate that both agents have only little effects on U 937 cells when acting alone. When combined in culture, however, they synergize to induce monocytic differentiation of U 937 cells as disclosed by significant increase of cells capable of reducing NBT and displaying surface C3 bi receptor that was accompanied by reduction of clonogenicity in colony assays. Induction of differentiation and inhibition of proliferation of U 937 cells was preceded by downregulation of transcript levels of C-MYC, increase of C-FOS mRNA, and induction of accumulation of C-FMS mRNA. By sequential use of LIF and ara-C we also demonstrate that the basis of synergism of both agents does not involve mechanisms at the level of receptor ligation but that synergism may be initiated by complementary intracellular metabolic cascades.

Down-regulation of tyrosinase mRNA levels in melanoma cells by tumor promoters and by insulin

Mouse melanoma cells in culture respond to melanocyte-stimulating hormone (MSH) or to cyclic AMP analogues by demonstrating an increase in tyrosinase activity. In this study the effect of the tumor promoter, 12-O-tetradecanoylphorbol 13-acetate (TPA), on the hormonal induction of tyrosinase was examined. TPA was found to lower basal levels of tyrosinase activity in melanoma cells and to reduce tyrosinase levels in cells treated with either MSH (10(-7) M), dibutyryl cAMP (10(-4) M), isobutylmethylxanthine (IBMX, 10(-4) M), or with the potent MSH analogue, [Nle4,D-phe7]-alpha-MSH. The phorbol ester, phorbol 12,13-dibutyrate was also effective in lowering tyrosinase activity levels, while 4 alpha-phorbol 12,13-didecanoate, which does not bind protein kinase C, was ineffective. In order to determine how TPA may reduce tyrosinase activity in melanoma cells, the levels of tyrosinase mRNA in untreated or TPA-treated cells were determined by Northern blot analysis. A marked down-regulation of constitutive levels of tyrosinase mRNA was observed in cells treated with the tumor promoter. Tyrosinase mRNA levels in cultures exposed to TPA for 48 h were only 7% of control levels. Tyrosinase mRNA levels in cells treated with both MSH and TPA were also lower than in cells treated with MSH alone. Previous studies from this laboratory have shown that insulin both lowers basal tyrosinase activity in melanoma cells and antagonizes the MSH stimulation of the enzyme. We have now determined that this inhibition is also due to reduced levels of tyrosinase mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced MYCN oncogene expression in human neuroblastoma cells results in increased susceptibility to growth inhibition by TNF alpha

Human neuroblastoma cells with normal expression of the endogenous MYCN oncogene were transfected with a vector containing an exogenous MYCN gene. The transfected cells expressed the exogenous MYCN at high levels and had acquired a phenotype resembling that of cells from advanced human neuroblastomas. Proliferation of the MYCN-transfected, but not of the untransfected, neuroblastoma cells was inhibited by low concentrations of recombinant human tumor necrosis factor alpha (TNF alpha). Our results suggest that TNF alpha could be useful for the treatment of advanced human neuroblastomas, in which high MYCN expression seems to be a causative factor.

Reduction of N-myc expression by antisense RNA is amplified by interferon: possible involvement of the 2-5A system

Expression of myc-box genes can be reduced by Interferon (c-myc in Daudi cells) or Retinoic acid (N-myc in neuroblastoma cells). Interferon did not reduce N-myc expression in neuroblastoma cells. However, after transfection of the human neuroblastoma cell line LS with a vector, providing the Cadmium inducible expression of an antisense N-myc transcript, drastic reduction of N-myc RNA was achieved in these cells by incubation with Cadmium and Interferon. Treatment with Cadmium alone resulted in a comparably small reduction of N-myc transcripts in these cells. Interferon alone did not appreciably affect N-myc expression. Reduction of N-myc was accompanied with reduced cell proliferation and morphological differentiation. It is assumed that most of the inhibitory effects observed are mediated by the Interferon inducible 2-5A system.

Multiple protein forms of the human breast tumor-associated epithelial membrane antigen (EMA) are generated by alternative splicing and induced by hormonal stimulation

Cloning and sequencing of epithelial membrane antigen (EMA) has demonstrated the existence of a variable number of tandem repeats (VNTR) flanked by unique sequences, and alternative splicing has been proposed to result in secreted and membrane-bound antigenic forms. Antisense oligonucleotides, specific for the VNTR region and various alternative splice forms, were used as probes to define EMA transcripts in poly A+ RNA from a mucinous breast tumor cell line. The BT549 line has been shown to exhibit enhanced expression and secretion of EMA when the cells are cultivated in a medium supplemented with hydrocortisone and insulin, and Northern blot analysis demonstrated that EMA-related RNA transcripts are commensurately enhanced. As a result of the large increase in EMA RNA levels, two major transcripts in BT549 have been identified as coding for either the secreted or transmembrane EMA forms and two antigenic forms have been immunoprecipitated from BT549 cell layer and medium translation products.

Regulation of mdr RNA levels in response to cytotoxic drugs in rodent cells

The mdr gene, which encodes an energy-dependent multidrug efflux pump termed P-glycoprotein, is expressed in some normal human and rodent tissues, including the adrenal gland, kidney, liver, colon, small intestine, and brain and testis capillary endothelial cells. Because of the important role played by the multidrug transporter in determining sensitivity of normal tissues and resistance of cancers to chemotherapeutic drugs, we and others have been determining the environmental factors which regulate expression of the mdr gene. In previous studies, expression of the human MDR1 gene has been shown to be regulated by heat shock, arsenite, and cadmium in a kidney carcinoma cell line, and mdr RNA is dramatically elevated in rat liver after partial hepatectomy or treatment of the animals with cytotoxic agents. We have now investigated the genetic response of the mdr gene to acute cytotoxic insults in rodent and human tissue culture cells. Following exposure to several drugs, most of which are known to be substrates for the multidrug transporter, mdr RNA levels were found to increase substantially in the rodent cells, but not the human cells. Furthermore, RNA levels for topoisomerase II, an intracellular target for these drugs, decreased in the rodent cells. These results suggest a complex pattern of regulation of mdr RNA levels, depending on animal species and cell type, and possible coordinate regulation with topoisomerase II RNA levels.

Effect of transforming growth factor beta on the EL4 thymoma variant EL4/6.1: dissociation of inhibition of proliferation from expression of IL-1 and IL-2 receptors

In order to further characterize the action of transforming growth factor beta (TGF-beta) on lymphoid cells, we investigated the effects of porcine TGF-beta 1 and -2 on the IL-1 sensitive EL4/6.1 thymoma cell line. The proliferation of EL4/6.1 thymoma cells was inhibited by TGF-beta 1 and TGF-beta 2 (1 ng/ml) to a similar degree, the population doubling time was increased by 50-60%, total inhibition was not achieved. This decrease of proliferation was associated with an increase of the number of cells in the G0/G1 compartment of the cell cycle. TGF-beta-mediated inhibition could not be overcome by adding exogenous rIL-1 nor was the binding capacity for IL-1 reduced. In addition, TGF-beta did not interfere with the induction of IL-2 receptors by a combination of Ionomycin+PMA+IL-1. The data suggest that TGF-beta mediated inhibition of thymocyte/lymphocyte proliferation is not associated with an inhibition of the expression or the induction of expression of IL-2 or IL-1 receptors.

Induction of growth factor-receptor and metalloproteinase genes by epidermal growth factor and/or transforming growth factor-alpha in human gastric carcinoma cell line MKN-28

We examined the effects of epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) on EGF receptor (EGFR) phosphorylation and the expression of mRNAs for oncogenes, growth factors, their receptors and metalloproteinase genes by MKN-28 gastric carcinoma cells which express EGF, TGF-alpha and EGFR genes. Both EGF and TGF-alpha stimulated EGFR phosphorylation, EGF and TGF-alpha induced FOS, MYC and ERBB-2 oncogene expression. Interestingly, EGF increased the expression of mRNAs for TGF-alpha and EGFR. On the other hand, TGF-alpha increased TGF-alpha mRNA but decreased the expression of mRNAs for EGFR and TGF-beta. Furthermore, mRNAs for interstitial collagenase, stromelysin and procollagen type I genes were also enhanced after treatment with EGF and TGF-alpha. These results indicate that EGF and TGF-alpha successively evoke cascade phenomena which favor tumor progression, invasion and extracellular matrix formation, acting as autocrine growth regulators for gastric carcinomas.

Induction of F9 cell differentiation by transient exposure to retinoic acid

The F9 cell is a mouse embryonal teratocarcinoma which can be induced to differentiate into visceral endoderm by treatment with retinoic acid (RA). Treatment with RA in conventional studies was carried out in the constant presence of RA. Here we demonstrate that treatment with RA can be as short as 3 hrs to induce differentiation of F9 cells. Morphology, alpha-fetoprotein gene activity, and temporal patterns of F9 cell differentiation are the same with both short- and long-term treatment with RA.

Insulin's regulation of c-fos gene transcription in hepatoma cells

In H4IIE rat hepatoma cells insulin interacts with its receptors to induce DNA synthesis and promote cell division. However, the postreceptor events that lead to DNA synthesis and cell division have not been well characterized. Previous studies indicate that insulin can regulate the expression of several genes in H4 cells. One of these genes is the proto-oncogene c-fos, a cellular gene whose deregulation has been implicated in the process of cellular differentiation and division. In the present work insulin is shown to regulate cellular c-fos mRNA accumulation and the transcription rate of the c-fos gene. Insulin caused a rapid, dose-dependent increase in the cytoplasmic concentration of c-fos mRNA which was maximal by 30 min. Preceding this, a more rapid 6-8 fold increase in transcription of the c-fos gene was observed. Induction of transcription was apparent following only 5 min of insulin addition. This is the most rapid effect of insulin yet demonstrated on the induction of gene expression. Protein synthesis inhibitors (cycloheximide, anisomycin) also induced the transcription of the c-fos gene. However, they stimulated a much greater increase in transcription than did insulin, and followed a different time course of action. The addition of insulin in combination with a protein synthesis inhibitor resulted in no greater increase in c-fos transcription than did the addition of a protein synthesis inhibitor alone. The nonadditivity of H4 cell c-fos gene expression may indicate a similar mode of action by insulin and protein synthesis inhibitors.

Thymosin beta 10 levels in developing human brain and its regulation by retinoic acid in the HTB-10 neuroblastoma

Human fetal brain expresses high levels of a polypeptide identified by protein biochemistry and molecular cloning as thymosin beta 10. Within the first 18 months after birth, the thymosin beta 10 content of human brain falls to undetectable levels. In order to establish the molecular basis of this process we screened a number of human tumor cell lines derived from the nervous system for the presence of thymosin beta 10. All of the cell line expressed authentic thymosin beta 10. However, in the HTB-10 neuroblastoma, retinoic acid caused a reduction in the level of thymosin beta 10. This effect of the retinoid was conditional upon its continual presence in the tissue culture medium and was not evident in the other cell lines examined. These results suggest that the thymosin beta 10 gene may be a target for retinoids in the developing nervous system.

Transforming growth factor-beta activities in 'in vivo' lines of hormone-dependent and independent mammary adenocarcinomas induced by medroxyprogesterone acetate in BALB/c mice

We have determined the presence of transforming growth factor-beta (TGF-beta)-like polypeptides in mammary adenocarcinomas induced by medroxyprogesterone acetate (MPA) in BALB/c mice. In hormone-dependent tumors (HD) from nontreated and MPA-treated mice a high molecular weight (43 kDa) transforming activity was purified by Bio-Gel P-60 chromatography. This TGF was able to confer the neoplastic phenotype on NRK-49F cells without the addition of epidermal growth factor (EGF), though its activity was potentiated by EGF. It did not compete for binding to the EGF receptor, had no mitogenic activity on monolayer cultures of NRK fibroblasts, and was a potent inhibitor of DNA synthesis induced in these cells by EGF and insulin. In HD and hormone-independent tumors (HI) another TGF with a Mr of 13 kDa was isolated. This transforming activity showed the same biological properties as 43 kDa TGF, with the exception that in the absence of EGF it did not stimulate soft agar growth of NRK-49F cells. The synthesis of both factors in 'in vivo' HD tumors seems to be under MPA control, since it is much lower in HD tumors from MPA-treated mice. Further purification of the 13 and 43 kDa TGFs by hydrophobic interaction HPLC demonstrated that each one eluted in a different position, and that their elution profile differed from the TGF-beta from human platelets. The biological activity of the 13 and 43 kDa TGFs was not neutralized by a specific anti-TGF-beta antibody.

Effects of hepatocarcinogenic initiators on aldehyde dehydrogenase gene expression in cultured rat hepatic cells

The effects of certain in vivo inducers of tumor-associated aldehyde dehydrogenase (aldehyde:NAD+ oxidoreductase, EC 1.2.1.3; ALDH) activity on the expression of tumor-associated ALDH (T-ALDH) in vitro have been investigated using cultured rat hepatocytes and hepatoma cell lines. Two distinct groups of T-ALDH inducers have been identified. Three hepatocarcinogenic initiators 2-acetylaminofluorene, diethylnitrosamine and ethionine, which cause changes in T-ALDH in vivo, do not induce T-ALDH activity in cultured rat hepatocytes or hepatoma cell lines following either short-term or long-term exposures. In contrast, polycyclic aromatic hydrocarbons, such as 3-methylcholanthrene, benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene, induce an immediate increase of T-ALDH activity in both cultured rat hepatocytes and hepatoma cell lines. Synthesis and degradation rates of T-ALDH mRNA and protein have also been determined. The synthesis of T-ALDH protein is coupled with the increased synthesis of T-ALDH mRNA when the T-ALDH gene is constitutively expressed or activated by an inducer. Both T-ALDH mRNA (t1/2 = 25 - 34 h) and protein (t1/2 = 88 - 95 h) in high T-ALDH activity cell lines or low-activity cell lines treated with an inducer are relatively stable. Combined with previous studies, the results suggest that at least two different mechanisms are involved in T-ALDH gene expression; events occurring during initiation as well as during promotion appear to be involved in the genetically stable changes in T-ALDH gene expression which occur in vivo. The results also indicate that the lack of T-ALDH activity in normal hepatocytes or low-activity hepatoma cell lines is due to repression of the T-ALDH gene rather than to the differential stability of T-ALDH mRNA or protein.

[The role of interferons in neuroblastoma. 1: Antiproliferative effects]

Antiproliferative effects of interferon alpha, beta and gamma were investigated on several human neuroblastoma cell lines using the soft agar colony forming assay and the MTT-test. Investigations were carried out in order to prove whether there is any relationship between antiproliferative effects, inhibition of N-myc expression and the 2-5A system. Growth of neuroblastoma cells was inhibited by all three kinds of interferons in a concentration-dependent manner, however, rather high concentrations were necessary in some cell lines. Expression of N-myc oncogen was not inhibited by interferon-beta and no relationship between antiproliferative effects and the 2-5A system was observed. A vector containing a small N-myc fragment in antisense direction was constructed and transferred into the interferon insensitive human neuroblastoma cell line LS. After transformation, LS cells became sensitive to interferon beta: Proliferation as well as N-myc expression were inhibited and these processes are most probably associated with activation of the 2-5A system.

An experimental analysis of cancer: role of ras oncogenes in multistep carcinogenesis

Carcinogen-induced animal tumor models are invaluable resources for studies aimed at understanding the participation of ras oncogenes in multistep carcinogenesis. Mutationally activated ras oncogenes are frequently detected in chemically induced animal tumors. The nature of the mutations in ras oncogenes reflects the chemical specificity of the carcinogen, implying that the carcinogen interacts with ras sequences. In chemically induced rat mammary tumor models, ras activation is the earliest detectable change in the mammary gland cells following administration of the chemical. Further, expression of the tumorigenic phenotype of cells containing activated ras requires the cooperation of normal physiological factors that are active during puberty.

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.

Effect of gamma interferon on HLA class-I and -II transcription and protein expression in human breast adenocarcinoma cell lines

The spontaneous expression of HLA class-I and class-II molecules in 5 human breast carcinoma cell lines, MCF-7, T47D, ZR75-1, HSL-53, MDA-MB 231, and their modulation during IFN-gamma treatment, are reported. The expression of cell-surface determinants was examined by indirect immunofluorescence using monoclonal antibodies (MAbs) specific for HLA class-I and class-II (DR, DQ and DP) antigens. The biosynthesis and maturation of these molecules were analyzed by 2-dimensional gel electrophoresis analysis (2D-PAGE) of class I, DR alpha, beta and invariant immunoprecipitates. Transcription was analyzed by Northern blot hybridization with HLA class-I and -II cDNA-specific probes. In all cell lines, more than 80% of cells expressed HLA class-I antigens at their surface. 2D-PAGE and mRNA studies showed a variable basal level of HLA class-I biosynthesis and transcription with a constant increase after 1,000 U/ml IFN-gamma treatment. HLA class-II determinants were totally absent from the surface of MCF-7, MDA MB231, ZR75-1 and T47D but they were detected in a small subpopulation of HSL-53 cells (DR 6%, DQ 6%, DP 20%). Spontaneous biosynthesis of HLA-DR molecules in immunoprecipitates analyzed by 2D-PAGE or transcripts in Northern blot were not detected in the 5 cell lines. Treatment with 1000 U/ml IFN-gamma induced or increased the expression of HLA class-II molecules in all cell lines but DQ expression was variable. While T47D, ZR75-1 and HSL-53 increased their transcripts and antigen expression, MDA, MB231 and MCF-7 showed no DQ mRNA transcript. Biochemical analysis of the DR products revealed a classical alpha, beta and invariant (li) chain pattern, but indicated a constant glycosylation defect in the invariant chain in all cell lines, associated with weak expression of the beta chain and the presence of an extra spot of low molecular weight in the acidic part of the gel. Thus, post-transcriptional events did not appear to be totally controlled by IFN-gamma in the different cell lines. These differences in DQ expression and glycosylation process in different breast cancer cells may be important in the activation of the immune response among different individuals.

Estrogen regulation of placental alkaline phosphatase gene expression in a human endometrial adenocarcinoma cell line

A human endometrial tumor (Ishikawa) cell line in culture responded to estradiol stimulation, as measured by growth and alkaline phosphatase activity. These effects were similar whether the medium was enriched with serum or was serum-free. Estradiol increased placental alkaline phosphatase activity 2-3-fold over control in these Ishikawa cells. The mechanism for this increase appeared to be at the level of transcription, at least in part, since there was an increase in the concentration of placental alkaline phosphatase mRNA. The administration of tamoxifen or 4-hydroxytamoxifen was unable to antagonize the estradiol-stimulated alkaline phosphatase enzyme activity or mRNA expression. The administration of tamoxifen alone had no effect on alkaline phosphatase enzyme activity, but tamoxifen did stimulate the steady state concentration of alkaline phosphatase mRNA. In contrast, a new antiestrogen, ICI 164,384, was able to antagonize both of these estradiol-stimulated effects.

Emergence and decay of the human Mx homolog in cancer patients during and after interferon-alpha therapy

The human Mx, an interferon (IFN)-alpha- and IFN-beta-induced 76-kd protein, is a homolog (Mx-homolog) to the murine Mx protein, which is necessary and sufficient to provide adequate resistance against influenza virus in murine cells and in mice. Leukocytes from 36 patients with tumors (chronic myelogenic leukemia, hairy cell leukemia, and malignant melanoma) were monitored for their Mx-homolog content before, during, and after rIFN-alpha-2b therapy. Before therapy, only one patient was slightly positive for Mx-homolog. All 36 patients showed a significant increase of Mx-homolog in their mononuclear cells within the first day of IFN therapy. During therapy, the Mx-homolog levels remained elevated. After cessation of treatment, the Mx-homolog content in the mononuclear cells decreased slowly; within 2 weeks, it was about 20-30% of its value during therapy. However, even after 3 weeks, the Mx-homolog was still detectable. The maximally induced Mx-homolog concentration showed a significant correlation to the IFN dose given in vivo. These data indicate that the Mx-homolog is an excellent marker for monitoring the activity of IFN during IFN therapy. In addition, the in vivo endogenous activation of the IFN system might be detectable by the determination of the Mx-homolog despite the lack of circulating IFN.

Production of interleukin 6 by hepatoma cells

Five rat hepatoma cell lines were shown to secrete hepatocyte-stimulating factors (HSFs) capable of inducing a characteristic spectrum of acute phase genes. Three of these lines, but not normal rat livers or livers from rats with an experimentally induced acute inflammation, produced interleukin 6 (IL6) mRNA. An anti-rat IL6 serum was prepared against synthetic peptides derived from the rat IL6 cDNA sequence. This antiserum cleared authentic rat IL6 and a fraction of the HSF activities secreted by the hepatoma cell lines. After concentration of culture supernatants from FTO2B hepatoma cells, IL6 was detected with the anti-IL6 serum by immuno-blot analysis. Biosynthesis of IL6 in the HTC line was demonstrated by metabolic labeling and immunoprecipitation. Secretion of HSF activities by hepatoma cells was increased by serum factors. These data suggest that different rat hepatoma lines each secrete different characteristic sets of HSF activities and establish unambiguously that IL6 is secreted by at least some of these lines.

Interferon-regulatory factor 1 is an immediate-early gene under transcriptional regulation by prolactin in Nb2 T cells

The pituitary peptide hormone prolactin (Prl) is a potent inducer of Nb2 T lymphoma cell proliferation. To analyze the early genetic response to the mitogenic signals of Prl, a cDNA library was constructed from Nb2 T cells stimulated for 4 h with Prl and the protein synthesis inhibitor cycloheximide. Of 26 distinct clones isolated by differential screening, one clone, designated c25, exhibited extremely rapid but transient kinetics of induction by Prl and superinduction by Prl plus cycloheximide. Run-on transcription analysis indicated that c25 gene transcription was induced greater than 20-fold within 30 to 60 min of Prl stimulation. Surprisingly, DNA sequence analysis of c25 cDNA revealed that this Prl-inducible early-response gene is the rat homolog of the mouse transcription factor interferon-regulatory factor 1 (IRF-1), sharing 91% coding sequence similarity with mouse IRF-1. At the protein level, rat IRF-1 shares 97% and 92% homology with mouse IRF-1 and human IRF-1, respectively, suggesting that this molecule has been functionally conserved throughout evolution. Our studies show that the gene for IRF-1 is an immediate-early gene in Prl-stimulated T cells, which suggests that IRF-1 is a multifunctional molecule. In addition to its role in regulating growth-inhibitory interferon genes, IRF-1 may, therefore, also play a stimulatory role in cell proliferation. The gene for IRF-1 is one of the earliest genes known to be transcriptionally regulated by Prl.