Purification and biological properties of type beta transforming growth factor from mouse transformed cells.

Transforming growth factor type beta (TGF beta) has been purified from serum-free culture fluids of transformed mouse L-929 cells which are capable of continual growth in serum-free medium in the absence of any exogenously added polypeptide growth factors. TGF beta has been purified to homogeneity as judged by NH2-terminal amino acid sequence analysis. Analysis of the purified polypeptide by gel electrophoresis indicates that TGF beta is composed of two polypeptide chains of Mr 12,500 cross-linked by disulfide bonds. TGF beta was characterized by its ability to induce anchorage-dependent normal rat kidney (NRK) cells to grow in soft agar in the presence of epidermal growth factor (EGF). TGF beta was also able to enhance both EGF-induced DNA synthesis and cell proliferation on growth-arrested NRK cells in monolayer cultures under serum-free conditions. We also show that in mouse melanoma B-16 cells under serum-free conditions TGF beta stimulates both DNA synthesis in monolayer cultures and anchorage-independent growth in soft agar. Paradoxically, the anchorage-independent growth in the presence of serum of many human cell lines, including melanomas, and mammary, prostatic, vulvar, and lung carcinomas is inhibited by TGF beta at saturating concentrations similar to those that stimulate colony formation of the rodent cell lines L-929 and B-16 under serum-free conditions. The peculiar action of TGF beta is further revealed by the observations that while EGF and TGF beta synergize to induce inhibition of anchorage-independent growth of A-431 human vulvar carcinoma cells, their effects on the anchorage-independent growth of one human lung carcinoma cell line (A-549) and two human prostatic carcinoma cell lines (PC-3 and DU-145) are antagonistic. Moreover, we show that in the rodent and human cell lines TGF beta interacts with specific cellular receptors which may mediate the actions of TGF beta. We conclude that the expression of both TGF beta and TGF beta receptors by L-929 cells and the stimulation of growth of L-929 cells in serum-free medium by TGF beta suggests that TGF beta may be important for maintaining the transformed state of this tumor cell line, and the way in which a cell responds to TGF beta is dependent on the presence or absence of growth factors contained in the serum.

Correlation between the loss of the transformed phenotype and an increase in superoxide dismutase activity in a revertant subclone of sarcoma virus-infected mammalian cells.

We have studied the effects of paraquat (methyl viologen), a herbicide that increases intracellular production of superoxide radical, on the viability of virus-transformed and nontransformed normal rat kidney (NRK) cells in culture. We have shown that a low concentration of paraquat (12.5 microM) is cytotoxic toward virus-transformed cell lines, including Kirsten sarcoma virus- and SV40-transformed NRK cells. The corresponding untransformed NRK cells were resistant to the same and a 4-fold higher concentration of paraquat. There was a good correlation between the susceptibility of transformed and untransformed cells to paraquat cytotoxicity and their ability to increase the superoxide dismutase (SOD) enzymatic activity. We found that paraquat is cytotoxic toward Kirsten sarcoma virus-transformed and SV40-transformed NRK cells which showed low intracellular SOD activity. The relationship between SOD activity and paraquat cytoxicity was strengthened by the finding that the tolerance of NRK cells to the drug was associated with high intracellular SOD activity. This report also describes the isolation of a revertant (revertant RE8G3) cell line derived from Kirsten sarcoma virus-transformed NRK cells after paraquat treatment which contains SOD activity at levels much higher than those found in NRK cells. This revertant is undistinguishable from NRK cells with respect to its lack of transformed cell properties. Not only are these cells normal morphologically but also they do not grow in soft agar, an in vitro property that closely correlates with in vivo tumorigenicity. Several biological and biochemical properties of RE8G3 cells, including growth characteristics, surface receptors for both transferrin and epidermal growth factor (EGF), and the EGF-dependent 32P phosphorylation of specific membrane polypeptides have been studied. The most interesting conclusion that can be drawn from these studies is that there is a correlation between loss of the transformed phenotype and an increase in both EGF receptors and EGF-dependent 32P phosphorylation of a m.w. 170,000 membrane-associated protein.

Modulation of epidermal growth factor receptor gene expression by transforming growth factor-beta in a human breast carcinoma cell line.

Modulation of epidermal growth factor (EGF) receptor expression determines cellular responsiveness to EGF and might play an important role in growth inhibition. We have investigated the actions of EGF and/or transforming growth factor type beta (TGF beta) on EGF receptor gene expression in MDA-468 human breast carcinoma cell line, which responds to EGF and/or TGF beta with growth inhibition. Using the cDNA clone pE7, which encodes 2.4 kilobases of the human EGF receptor mRNA, as a hybridization probe, we have found that exposure of MDA-468 cells to EGF results in elevated levels of EGF receptor mRNA. This increase in mRNA accumulation showed time and dose dependence. Addition of TGF beta enhances the accumulation of EGF receptor mRNA induced by EGF. Under this condition, stimulation could be detected after 1 h exposure to TGF beta with a maximum at 6-8 h. A concentration of 10 pM TGF beta gave detectable stimulation with maximal stimulation occurring at 300 pM in the presence of EGF (50 ng/ml). In contrast, TGF beta alone had no significant effect on EGF receptor mRNA accumulation. In the presence of cycloheximide, the EGF receptor mRNA was super-induced in response to EGF. Treatment of the cells with TGF beta enhances the EGF-dependent superinduction of EGF receptor mRNA produced by cycloheximide, suggesting that the stimulatory action of TGF beta does not depend on continuous protein synthesis. The results described here are consistent with the hypothesis that the growth inhibitory action of TGF beta in MDA-468 cells may be mediated, at least in part, by modulation of EGF receptor gene expression.

Antiviral, cytotoxic and apoptotic activities of picolinic acid on human immunodeficiency virus-1 and human herpes simplex virus-2 infected cells.

The antiviral, cytotoxic and apoptotic effects of picolinic acid against human immunodeficiency virus-1 (HIV-1) and human herpes simplex virus-2 (HSV-2) infected cells were evaluated in cultured cells using in vitro assays. Picolinic acid was tested at several concentrations (from 0.15 to 3 mM) against one input dilution of the viruses to determine if the agent had any antiviral activity against HIV-1 or HSV-2. The results showed that picolinic acid at 1.5 mM (185 ug/mL) and 3 mM (369 ug/mL) was active against HIV-1 and HSV-2-infected cells, causing cytotoxicity which resulted in apoptosis and lack of viral replication. In parallel control experiments with non-infected cells, picolinic acid also caused cytotoxicity and apoptosis, which was more prominent at 3 mM than at 1.5 mM. Thus, infected cells appear to be slightly more sensitive to the cytotoxic and apoptotic effects of picolinic acid. The overlapping of the antiviral profile with the cytotoxic profile of picolinic acid indicates that, in vitro, the most likely sequence of events is that picolinic acid initially causes cytotoxicity which in turn results in apoptosis of cells infected with HIV-1 or HSV-2 and thus reduces the amount of viral replication.

Essential viral and cellular zinc and iron containing metalloproteins as targets for novel antiviral and anticancer agents: implications for prevention and therapy of viral diseases and cancer.

In this review the authors summarize the experimental data on the role of a selected group of metalloproteins, particularly viral (v) and cellular (c) zinc finger proteins (ZFP) and iron containing proteins which are involved in cell proliferation, neovascularization, apoptosis, and viral infection. Furthermore, this review summarizes the data embracing the hypothesis that disruption of certain metalloproteins by novel pharmacological agents is a key factor in controlling viral and proliferative diseases. The primary goal of this review is to show the potential therapeutic applications of ZFP disrupting agents, zinc chelators and iron chelators in the control of viral diseases and cancer. It is known that zinc or iron deficiency, resulting from exposure of culture cells to membrane-permeable Zn2+ or Fe(2+)-chelators, can induced apoptosis in virally transformed cells while normal cells remain unaffected under these conditions. Apoptosis is possibly due to simultaneous inactivation of vZFP, cZFP, and/or iron containing proteins, which are essential for maintenance of cellular and viral structure and which are activated in virally transformed cells. New insights concerning apoptosis, viral metalloproteins, and novel antiviral agents will also be reviewed. From the evidence reviewed, one can infer that development of a variety of drugs that control or neutralize vZFP may lead to a new therapeutic approach directed at controlling and preventing a wide spectrum of viral diseases and cancer. Furthermore, the results suggest that these agents may be useful to prevent transmission of viral diseases. Finally, this review not only points out the limits of our understanding of this system, but also directs scientists to opportunities for future research.

Cytotoxic activity of fusaric acid on human adenocarcinoma cells in tissue culture.

When cultured human normal WI-38 fibroblasts were exposed to 500 microM fusaric acid (5-butylpicolinic acid), cell proliferation ceases. The majority of the WI-38 cells remained in a quiescent G1(G0) state and viable for approximately 30 to 48 h. The effect of fusaric acid on WI-38 cell growth was slowly reversible after removal of the agent from the culture media. In contrast, within 24 h of exposure to 500 microM fusaric acid, most of the human colon adenocarcinoma LoVo cells were blocked at random in the cell cycle and approximately 80% of the cells were dead after 30 h. Three additional human colorectal adenocarcinoma cell lines, denoted SW48, SW480, and SW742, were also sensitive to the inhibitory and cytotoxic effects of fusaric acid. Of all the cell lines tested, the human mammary adenocarcinoma cell line MDA-MB-468 was the most sensitive to the growth inhibitory and cytotoxic effects of fusaric acid. Further experiments with MDA-MB-468 cells demonstrated that fusaric acid is a potent inhibitor of DNA synthesis. Fusaric acid also inhibited the growth of human epidermoid carcinoma KB cells and showed cytotoxic actions for this cell line but its effects on cell viability were not as pronounced. The results presented here indicate that fusaric acid has potent anti-proliferative activity in vitro on various normal and cancer cell lines and suggest that it exhibits some cytotoxic specificity for growing and confluent colorectal adenocarcinoma and mammary adenocarcinoma cell lines.

Expression of transforming growth factor alpha mRNA in benign and malignant tissues derived from gynecologic patients with various proliferative conditions.

Growth factors are polypeptides involved in the regulation of normal and malignant cell growth. Transforming growth factor alpha (TGF alpha) is one of such protein growth factors that plays an important role in the regulation of mammalian cell growth. In this study, the expression of TGF alpha mRNA was studied in tissue specimens obtained at the time of surgery from patients with benign and malignant gynecologic proliferative conditions. To analyze TGF alpha mRNA expression we utilized the highly sensitive technique denoted Message Amplification Phenotyping which can detect mRNA in single cells. This technique consists of isolating RNA, reverse transcription of total cellular RNA to produce copy DNA, followed by enzymatic amplification of TGF alpha cDNA fragments using specific TGF alpha primers and polymerase chain reaction. The results showed significant levels to TGF alpha mRNA expression in vulvar (100% of the cases positive), cervical (66% positive), and endometrial (66% positive) carcinomas. Moreover, vulvar condylomas produced by human papilloma virus (HPV) showed the highest levels of TGF alpha mRNA expression of all the pathological tissues examined. In contrast, vulvar melanoma, fibrocystic disease of the breast, and certain ovarian tumors showed undetectable TGF alpha mRNA expression. Normal mesodermal tissues such as myometrium, abdominal rectus muscle, and fallopian tubes were negative for TGF alpha mRNA expression. However, TGF alpha mRNA was present in normal cervix and in normal endometrium. The results showed that TGF alpha mRNA expression is frequently associated with various malignant tumors and HPV-induced lesions of epithelial origin, suggesting that TGF alpha mRNA protein product may be a contributory factor in the progression of these pathological tissue alterations. Finally, TGF alpha mRNA expression was not restricted to malignant cells, suggesting that the TGF alpha mRNA protein product may function as a mitogen in the normal human epithelial tissues examined.

Expression of metallopanstimulin and oncogenesis in human prostatic carcinoma.

BACKGROUND: We have previously shown that human metallopanstimulin (MPS-1) is a 9.4-kDa multifunctional ribosomal S27/nuclear "zinc finger" protein which is expressed in a wide variety of actively proliferating cells and tumor tissues. Furthermore, we have shown that detection of MPS-N immunoreactive material in sera corresponding to the NH2 terminus of MPS-1 provides a method for determining the presence of certain types of abnormal proliferative conditions and/or active oncogenic processes in patients. In this study, we investigated MPS-N and MPS-N-like antigens present in the blood of patients with prostatic carcinoma (PC) and their relationship to the clinical status of patients with PC. METHODS: The presence of MPS-N immunoreactive material was determined using a sensitive and specific radioimmunoassay (RIA) which has been developed to measure circulating levels of MPS-N antigen(s). In addition, MPS-N levels were compared to the primary bio-marker used in PC patient management, Prostatic Specific Antigen (PSA). RESULTS: MPS-N concentrations were determined in the blood of 107 males having no evidence of PC, and in 126 patients diagnosed with PC. In patients, not having PC the MPS-N levels were lower than 10 ng/mL. In untreated patients having PC stages T1/T2, the MPS-N level range was 10-30 ng/mL; in stages T3/T4 the MPS-N level range was 30-50 ng/mL; and in stage Mlb (distant metastasis to the bones) the MPS-N levels were extremely high (> 50 ng/mL). In Mlb patients that did not respond to therapy, the MPS-N levels remained very high (> 50 ng/mL). In Mlb patients that went into remission after treatment, the MPS-N levels were dramatically reduced. In addition, a comparison of the test properties of MPS-N and PSA for prostate cancer were evaluated in a total of 231 patients. In both the low and high value range, both MPS-N and PSA appear to be equally effective in modifying the probability of the target condition-prostatic cancer. CONCLUSIONS: These findings show that (1) in untreated PC patients, the increase in serum MPS-N correlated with the stage of the disease; (2) MPS-N tumor marker predicted the degree of aggressiveness of tumor growth and response to therapy. In summary, despite the uncertainties of the relative contributions of the molecules being measured in cancer patients (authentic MPS-1, and MPS-N-like protein sequences), the MPS-N test is a pragmatic test that correlates well with active prostatic malignancy.

Expression of metallopanstimulin in condylomata acuminata of the female anogenital region induced by papilloma virus.

We have identified by cDNA cloning a gene, denoted MPS-1, that is activated in cultured human transformed cells by growth factors. The MPS-1 gene contains one zinc finger domain similar to those present in the C4 family of DNA binding proteins. In this study, the expression of MPS-1 mRNA and protein were examined in HPV-induced human condylomata acuminata. Initially, we detected the presence of MPS-1 mRNA by message amplification phenotyping in all condylomata tissues examined. Subsequently, the cellular distribution and abundance of MPS-1 mRNA was studied by in situ hybridization with specific MPS-1 DNA and RNA probes. We found that MPS-1 mRNA is expressed at high levels in the cytoplasm of condylomata cells. In contrast, the MPS-1 mRNA is expressed at low levels in nonneoplastic tissues. Moreover, antibodies were raised against the predicted N-terminal sequence of the MPS-1 protein and used to detect MPS-1 in condylomata cells. MPS-1 immunoreactivity was detected in the cytoplasm and/or the perinuclear regions of condylomata cells, with marked staining in areas of active proliferation. In distinction, MPS-1 immunoreactivity was very weak in normal epithelial cells. The results support the contention that the MPS-1 protein may be a potentially important mediator of proliferative responses induced by HPV.

Isolation and characterization of normal rat kidney cell membrane proteins with affinity for transferrin.

Studies were performed to identify membrane receptors for transferrin in cultured normal rat kidney (NRK) cells. Cells were surface iodinated or metabolically labeled with radioactive glycoprotein precursors. Membrane receptors for transferrin were solubilized with the nonionic detergent Triton X-100. The soluble transferrin receptor has been purified approximately 1500-fold by affinity chromatography using transferrin coupled to Sepharose. Experiments demonstrated that the receptor can be adsorbed to a transferrin-Sepharose gel and be eluted specifically with transferrin. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the receptor preparations obtained by one cycle of affinity chromatography display, in addition to components of Mr lower than 20 000, a major glycoprotein component of approximately 170 000. Solubilized receptor preparations subjected to two cycles of affinity chromatography revealed a single polypeptide of approximately 20 000 daltons. Further studies indicated that the 20 000-dalton polypeptide is a degradation product of the 170 000 glycoprotein. Immunological studies showed that antitransferrin antibodies specifically precipitate a transferrin-170 000 complex and that a specific antibody against 170 000 glycoprotein precipitates the same complex. These results suggest that the 170 000 glycoprotein associates with transferrin in specific fashion and that this protein may be a subunit of the transferrin receptor of NRK cells.

Modulation of transforming growth factor alpha-dependent expression of epidermal growth factor receptor gene by transforming growth factor beta, triiodothyronine, and retinoic acid.

We have investigated the actions of transforming growth factor (TGF) type alpha on epidermal growth factor (EGF) receptor mRNA expression in MDA-468 human mammary carcinoma cells in serum-free media. We found that exposure of MDA-468 cells to TGF alpha results in elevated levels of EGF receptor mRNA. This increase in mRNA accumulation showed time and dose dependence. Addition of TGF beta 1 enhanced the accumulation of EGF receptor mRNA induced by TGF alpha in a time- and dose-dependent manner. We also found that triiodothyronine at physiological concentrations exerts synergistic control on the action of TGF alpha alone, or in association with TGF beta 1, on EGF receptor mRNA expression. Similarly, retinoic acid treatment also enhanced in a time- and dose-dependent manner the TGF alpha-dependent response of EGF receptor mRNA and acted synergistically with TGF beta 1. The results described here suggest that optimum regulation of EGF receptor gene expression by TGF alpha is a complex process involving synergistic interactions with heterologous growth factors and hormones.

Metallopanstimulin gene product produced in a baculovirus expression system is a nuclear phosphoprotein that binds to DNA.

The protein product of the human Metallopanstimulin (MPS-1) gene was produced in the insect cell line Spodoptera frugiperda (Sf9) using the baculovirus expression vector system Autographa californica nuclear polyhedrosis virus (AcNPV). When a cloned MPS-1 complementary DNA sequence was inserted into the AcNPV viral genome downstream from the promoter of the polyhedrin gene, a polypeptide with an apparent molecular weight of approximately 10,000 was observed in extracts of infected Sf9 cells. This protein was not detected in Sf9 cells infected with AcNPV-MPS-1-Del, a vector in which the MPS-1 gene was deleted. The MPS-1 protein was produced at high levels in this host-vector system (congruent to 12% of total labeled soluble protein). Characterization of the MPS-1 protein extracted from Sf9 infected cells showed that it: binds zinc ions specifically; is phosphorylated; accumulates in the nucleus; is tightly bound to the nucleus; and binds to calf thymus DNA-cellulose. The MPS-1 protein constitutes one of the major proteins in the nuclear fraction of Sf9 cells and can be purified from this source to near homogeneity by a two-step procedure composed of high-performance liquid chromatography and gel electrophoresis. Antibodies were raised against selected peptide sequences of the MPS-1 protein and used to detect MPS-1 in insect cells and in various cultured mammalian cell types. Western analysis demonstrated that the baculovirus-generated protein had electrophoretic and immunological properties equivalent to those of MPS-1 spontaneously expressed in various human mammalian cell lines. Finally, recombinant MPS-1 generated a specific protein-DNA complex with a duplex oligomer containing a cyclic AMP-responsive element, as assessed by gel mobility shift assays. These results support the hypothesis that the MPS-1 protein may act, at least in part, by interacting with genes possessing the cyclic AMP-responsive element sequence.

Suppression of the EGF-dependent induction of c-myc proto-oncogene expression by transforming growth factor beta in a human breast carcinoma cell line.

Alterations in c-myc proto-oncogene expression after treatment of human mammary carcinoma MDA-468 cells with epidermal growth factor (EGF) and/or transforming growth factor beta (TGF beta) have been investigated. A stimulation of c-myc messenger RNA was detected within 60 min after treatment with EGF. This induction persisted for at least 24 hr, albeit to a lower extent. The early and late increase in c-myc mRNA levels induced by EGF were inhibited by the presence of TGF beta. TGF beta alone induced little change in c-myc mRNA levels. The effect of TGF beta represents a novel action of this hormone at the level of gene expression.

Transcriptional regulation of proto-oncogene expression by epidermal growth factor, transforming growth factor beta 1, and triiodothyronine in MDA-468 cells.

We have examined the epidermal growth factor (EGF) dependence of the transcription of different proto-oncogenes, using cultured human mammary carcinoma MDA-468 cells and a nuclear run-on transcription assay. We found that the stimulation of MDA-468 cells with EGF regulates moderately and to different extents the transcription of the EGF-receptor(R) and c-erbB-2 proto-oncogenes. In contrast, the transcription of other proto-oncogenes, including c-myc, c-H-ras, and c-fps, was unchanged. Furthermore, we provide evidence that transforming growth factor beta 1 (TGF-beta 1) selectively and to different degrees modulates the EGF-dependent transcription of EGF-R and c-erbB-2 genes. In this study, we also discovered that T3 (triiodothyronine) exerts synergistic control on the action of EGF alone or in association with TGF-beta 1, on EGF-R and c-erbB-2 gene transcription. Moreover, we established that within 6 h after the addition of EGF, cytoplasmic EGF-R mRNA levels are increased several-fold and that this accumulation is enhanced by the presence of TGF-beta 1 and/or T3. The results described here are consistent with the hypothesis that a complex program of cooperative interactions among EGF-, TGF-beta 1-, and T3-generated signals at the transcriptional level may mediate, at least in part, the combined actions of EGF, TGF-beta 1, and T3 in target cells.

Differential expression of metallopanstimulin/S27 ribosomal protein in melanocytic lesions of the skin.

We have previously shown that human metallopanstimulin (MPS-1) is a ubiquitous 9.4-kDa multifunctional ribosomal S27/nuclear "zinc finger" protein which is expressed at high levels in a wide variety of cultured proliferating cells and tumor tissues, including melanoma. In the present study, we have examined the expression of the MPS-1 protein in various types of human benign and malignant melanocytic lesions of the skin. The expression of the MPS-1 protein was studied by immunohistochemistry using specific anti-MPS-1 antibodies. We found that in benign nevi, the staining is weak and in a gradient; most often, only type A melanocytes stain positive. The B and particularly the C types are negative. Remarkably, congenital nevi show a similar gradient staining of regular benign nevi, but in addition one example showed intensely positive dermal nodules adjacent to areas of negative melanocytes. In melanomas, the staining patterns for MPS-1 are more complex. While some melanomas stain evenly and intensely positive, others have remarkably variable expression of MPS-1. The scattered melanocytes migrating to the upper layers of the epidermis are usually intensely positive. In summary, benign lesions stain in an orderly pattern with staining gradients that correlate with the cellular differentiation of the nevi. Malignant melanomas have an erratic, often intense staining that also correlates with the disorderly growth of these neoplasms. These differential results indicate that the MPS-1 antigen is a useful marker for melanocytic lesions at the immunohistochemical level.

Mechanism of hepatic extraction of gelatinized 99m technetium sulfur colloid.

Hepatic extraction, cellular and subcellular localization of gelatin stabilized Tc-99m sulfur colloid was studied in the rat model with time sequenced microautoradiography from 15 min to 24 h following I.V. administration of the tracer. Hepatic lobular and cellular distribution, quality and quantity of focal grain pattern, grain clusters, remained essentially constant for the period of study. Grain clusters were associated predominantly with Kupffer cells lining the peripheral segment of hepatic lobular sinusoids. Subcellular localization of gelatinized Tc sulfur colloid, stained prior to the I.V. administration with osmium tetroxide, was demonstrated with a transmission electron microscope in unosmicated liver tissue. Extracted Tc sulfur colloid particles were attached in groups to cytoplasmatic membranous intrasinusoidal projections of activated Kupffer cells. Intracytoplasmatic phagocytosis was not demonstrated. The kinetic arrest and en groupe extraction of Tc sulfur colloid particles at the Kupffer cell membrane suggests a specific membrane receptor site and specific Tc sulfur colloid particle-plasma protein interaction at the time of extraction. Hepatic extraction of gelatinized Tc sulfur colloid thus reflects primarily extra and intra hepatic hemodynamics and does not serve as an indicator of phagocytic hepatic reticuloendothelial system function.

A growth factor-inducible gene encodes a novel nuclear protein with zinc finger structure.

Growth factors rapidly induce numerous genes that encode regulatory proteins, many of which have been identified by cDNA cloning. In this study, differential hybridization was used to screen a cDNA library constructed from human mammary carcinoma MDA-468 cells that were stimulated with transforming growth factor beta-1 (TGF-beta 1) in the presence of cycloheximide. One of the cDNA clones that was induced by TGF-beta 1 was found to have a nucleotide sequence that predicts a 9,450-Da protein with homology to regulatory DNA-binding proteins. This clone was designated metallopan-stimulin-1 (MPS-1) because it encodes a metalloprotein whose mRNA is expressed in a wide variety of actively proliferating cells and tumor tissues. MPS-1 protein contains one "zinc finger" domain of the C4 type, similar to those present in proteins of the steroid/thyroid hormone receptor superfamily and other DNA-binding proteins. The mRNA for MPS-1 was induced in MDA-468 cells by fetal calf serum, TGF-beta 1, TGF-beta 2, and cAMP analogues. The MPS-1 gene is expressed at relatively high levels in several human carcinoma cell lines, particularly those derived from ectodermal layers, and at higher levels in melanomas (ontogenically of neural origin). In contrast, the MPS-1 mRNA is expressed at low levels in normal WI-38 human lung diploid fibroblasts in culture. We hypothesize that MPS-1 protein may play a role as a potentially important mediator of cellular proliferative responses to various growth factors and other environmental signals.

Differential expression of metallopanstimulin/S27 ribosomal protein in hepatic regeneration and neoplasia.

We have previously shown that human metallopanstimulin-1 (MPS-1) is a ubiquitous 9.4-kd multifunctional ribosomal S27/nuclear "zinc finger" protein that is expressed at high levels in a wide variety of actively proliferating cells and tumor tissues. In this study, we examined the expression of MPS-1 in chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Tissue samples were obtained at the time of tumor resection, needle biopsy, or liver transplantation. MPS- 1 was studied by immunohistochemistry by use of specific antibodies to the N-terminus of MPS-1 in a biotin/streptavidin-amplified system. In chronic hepatitis, hepatocytes had very weak MPS-1 immunostaining. In contrast, hepatocytes in regenerating cirrhotic nodules stained strongly for MPS-1. In well-differentiated hepatocellular carcinoma, MPS-1 presence was intense at the periphery of the malignant nodule. In poorly differentiated hepatocellular carcinoma, MPS-1 presence was notably intense in malignant hepatocytes invading the septal tissues, in close contact with neovascular structures. These results suggest that MPS-1 may be involved in both progression toward malignancy in regenerating cirrhotic nodules and in subsequent steps of hepatocarcinogenesis.