Transfection of human insulin-like growth factor-binding protein 3 gene inhibits cell growth and tumorigenicity: a cell culture model for lung cancer

IGF-I and IGF-II are potent mitogens, postulated to exert autocrine/paracrine effects on growth regulation in human lung cancer. Their proliferative effects are modulated by IGF-binding proteins (IGFBPs), which are found in conditioned medium (CM) of lung cancer cell lines. The biological role of the IGFBPs, which are ontogenetically and hormonally regulated, is not fully understood. Both inhibitory and stimulatory effects on cell growth have been demonstrated. Exogenous IGFBP-3 has been consistently shown to block IGF action, inhibiting cell growth in vitro. In order to evaluate the action of endogenously produced IGFBP-3 on cell growth in lung cancer, we stably transfected the non-small cell lung cancer cell line NCI-H23 with human IGFBP-3 cDNA (resulting in NCI-H23 pOPI3/BP-3) or with the vector pOPI3CAT as control (resulting in NCI-H23 pOPI3CAT). RT-PCR confirmed expression of IGFBP-3-specific mRNA in NCI-H23 pOPI3/BP-3, but not in N! CI-H23 or NCI-H23 pOPI3CAT. Western ligand blot and Western immunoblot analysis of CMs yielded strong signals of the characteristic 40-44 kDa human IGFBP-3 protein in NCI-H23 pOPI3/BP-3. An IGFBP-3 ELISA demonstrated a 20-fold increase in IGFBP-3 protein expression in NCI-H23 pOPI3/BP-3 as compared with NCI-H23. The growth of NCI-H23 pOPI3/BP-3 in serum-containing medium was significantly slower (1.7-fold) than that of NCI-H23 or the vector-transfected control NCI-H23 pOPI3CAT. While the proliferation rate of parental and vector-transfected cells could be stimulated by IGF-I, IGF-II, IGF-I analog Long R(3) IGF-I or insulin, that of NCI-H23 pOPI3/BP-3 could not. Xenotransplantation in nude mice resulted in marked tumor growth after the injection of NCI-H23 or NCI-H23 pOPI3CAT, but absent or minimal growth for the IGFBP-3-transfected cell line. These data suggest that IGFBP-3 is a potent inhibitor of cell growth in human lung cancer c! ell lines and may impair tumorigenicity in vivo.     

Cancer associated thrombosis in pediatric patients

The etiology of pediatric cancer associated thrombosis (CAT) is multifactorial and may reflect pro-coagulant alterations of the hemostatic system induced by presence of cancer itself or by therapeutic chemotherapy, tumor mass effects, tumor thrombi, and inherited thrombophilia. Age, diagnosis of hematological malignancy and presence of a central venous line significantly increase the risk of thrombosis. With over 80% cure rates of childhood cancer, strategies for prevention as well as for early diagnosis and optimal treatment of (thromboembolism) TE in children with malignancies are of major importance. Currently use of therapeutic low molecular heparin (LMWH) still prevails, as prospective studies and real world data regarding Direct oral anticoagulant (DOAC) use for treatment or prevention of pediatric CAT are scarce. The following review will address the epidemiology, etiology and risk factors for CAT in children, and describe the presently available evidence associated with anticoagulant therapy and prevention strategies.     

Cationic amino acid transporter 2 regulates inflammatory homeostasis in the lung

Arginine is an amino acid that serves as a substrate for nitric oxide synthase and arginase. As such, arginine has the potential to influence diverse fundamental processes in the lung. Here we report that the arginine transport protein, cationic amino acid transporter (CAT)2, has a critical role in regulating lung inflammatory responses. Analysis of CAT2-deficient mice revealed spontaneous inflammation in the lung. Marked eosinophilia, associated with up-regulation of eotaxin-1, was present in the bronchoalveolar lavage fluid of 3-week-old CAT2-deficient mice. The eosinophilia was gradually replaced by neutrophilia in adult mice, while eotaxin-1 levels decreased and GRO-alpha levels increased. Despite the presence of activated alveolar macrophages in CAT2-deficient mice, NO production was compromised in these cells. Examination of dendritic cell activation, which can be affected by NO release, indicated increased dendritic cell activation in the lungs of CAT2-deficient mice. This process was accompanied by an increase in the number of memory T cells. Thus, our data suggest that CAT2 regulates anti-inflammatory processes in the lungs via regulation of dendritic cell activation and subsequent T cell responses.     

Prevention of metastasis by inhibition of the urokinase receptor.

The plasminogen activator urokinase (u-PA) mediates proteolysis by a variety of human tumor cells. Competitive displacement of u-PA from cellular binding sites results in decreased proteolysis in vitro, suggesting that the cell surface is the preferred site for u-PA-mediated protein degradation. We studied the effect of u-PA receptor blockade on the metastatic capacity of human PC3 prostate carcinoma cells, using transfectants which expressed chloramphenicol acetyl-transferase (CAT). Eight weeks after subcutaneous inoculation of these cells into nude mice, CAT activity was detected in regional lymph nodes, femurs, lungs, and brain, thereby mimicking the organ tropism observed for naturally occurring metastases of prostate cancer. In a second transfection, CAT-expressing PC3 cells received cDNA encoding a mutant u-PA (Ser356-->Ala) which lacks enzymatic activity but which retains full receptor binding affinity. Three mutant u-PA expressors, each with < 5% of wild-type cell-associated u-PA activity, were compared in vivo with independently derived controls. Primary tumor growth was similar in each group of animals and all tumors expressed comparable CAT activity. In contrast, metastasis (as assessed by CAT activity) was markedly inhibited when cell surface u-PA activity was blocked. Levels of CAT activity were reduced by a factor of > 300 in regional lymph nodes, 40-100 in brain tissue, and 10-20 in lung tissue. Metastatic capacity was inhibited similarly when animals were given intermittent intraperitoneal injections of a u-PA/IgG fusion protein capable of displacing u-PA activity from the tumor cell surface. Our results indicate that cell surface u-PA activity is essential to the metastatic process. In addition, the assay system employed in these experiments may be generally useful in testing other therapeutic modalities to limit the spread of primary tumors.     

Antiestrogen-resistant human breast cancer cells require activated protein kinase B/Akt for growth

Development of acquired resistance to antiestrogens is a major clinical problem in endocrine treatment of breast cancer patients. The IGF system plays a profound role in many cancer types, including breast cancer. Thus, overexpression and/or constitutive activation of the IGF-I receptor (IGF-IR) or different components of the IGF-IR signaling pathway have been reported to render breast cancer cells less estrogen dependent and capable of sustaining cell proliferation in the presence of antiestrogens. In this study, growth of the antiestrogen-sensitive human breast cancer cell line MCF-7 was inhibited by treatment with IGF-IR-neutralizing antibodies. In contrast, IGF-IR-neutralizing antibodies had no effect on growth of two different antiestrogen-resistant MCF-7 sublines. A panel of antiestrogen-resistant cell lines was investigated for expression of IGF-IR and either undetectable or severely reduced IGF-IR levels were observed. No increase in insulin receptor substrate 1 (IRS-1) or total PKB/Akt (Akt) was detected in the resistant cell lines. However, a significant increase in phosphorylated Akt (pAkt) was found in four of six antiestrogen-resistant cell lines. Overexpression of pAkt was associated with increased Akt kinase activity in both a tamoxifen- and an ICI 182,780-resistant cell line. Inhibition of Akt phosphorylation by the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin or the Akt inhibitor SH-6 (structurally modified phosphatidyl inositol ether liquid analog PIA 6) resulted in a more pronounced growth inhibitory effect on the antiestrogen-resistant cells compared with the parental cells, suggesting that signaling via Akt is required for antiestrogen-resistant cell growth in at least a subset of our antiestrogen-resistant cell lines. PTEN expression and activity was not decreased in cell lines overexpressing pAkt. Our data demonstrate that Akt is a target for treatment of antiestrogen-resistant breast cancer cell lines and we suggest that antiestrogen-resistant breast cancer patients may benefit from treatment targeted to inhibit Akt signaling.     

Bc1-2 protects mice against fatal alphavirus encephalitis.

Virus-induced apoptosis has been well characterized in vitro, but the role of apoptosis in viral pathogenesis is not well understood. The suicide of a cell in response to viral infection is postulated to be an important host defense for the organism, leading to a reduction in its total viral burden. However, virus-induced death of nonregenerating cells in the central nervous system may be detrimental to the host. Therefore, to investigate the role of apoptosis in the pathogenesis of fatal encephalitis, we constructed a recombinant alphavirus chimera that expresses the antiapoptotic gene, bcl-2, in virally infected neural cells. Infection of neonatal mice with the alphavirus chimera expressing human bcl-2 [Sindbis virus (SIN)/bcl-2] resulted in a significantly lower mortality rate (7.5%) as compared with infection with control chimeric viruses containing a chloramphenicol acetyltransferase (CAT) reporter gene (SIN/CAT) (78.1%) or bcl-2 containing a premature stop codon (SIN/bcl-2stop) (72.1%) (P < 0.001). Viral titers were reduced 5-fold 1 day after infection and 10-fold 6 days after infection in the brains of SIN/bcl-2-infected mice as compared to SIN/CAT or SIN/bcl-2stop-infected mice. In situ end labeling to detect apoptotic nuclei demonstrated a reduction in the number of foci of apoptotic cells in the brains of mice infected with SIN/bcl-2 as compared with SIN/bcl-2stop. The reduction in apoptosis was associated with a reduction in the number of foci of cells expressing alphavirus RNA. Thus, the antiapoptotic gene, bcl-2, suppresses viral replication and protects against a lethal viral disease, suggesting an interaction between cellular genetic control of viral replication and cell death.     

Effect of lycopene on insulin-like growth factor-I,IGF binding protein-3 and IGF type-I receptor in prostate cancer cells

Purpose Prostate cancer is the second most common cancer that leads to death in elderly men. The risk of prostate cancer prevalence is often associated with the elevated level of insulin-like growth factor-I (IGF-I) and decreased level of IGF-binding protein 3 (IGFBP-3). Lycopene, a carotenoid, reduces the proliferation of cancer cells and induces apoptosis. Hence, higher intake of lycopene can be associated with the lower risk of prostate cancer. However, the mechanism of action of lycopene in the prevention of prostate cancer is still unclear. The present study was carried out to study the effects of lycopene on the components of IGF system and apoptosis in androgen-independent prostate cancer cells (PC-3 cells). Methods PC-3 cells were treated with various concentrations of lycopene, (20, 40 and 60 μM) for 24, 48, 72 and 96 h. IGF-I, IGFBP-3 and IGF-I receptor (IGF-IR) levels in lycopene-treated cells were evaluated. Annexin V and propidium iodide (PI) binding studies were done to assess apoptosis. Results PC-3 cells treated with lycopene showed a significant decrease in cell proliferation. Lycopene, at a dose of 40 μM, significantly increased the level of IGFBP-3. Lycopene-induced apoptosis was confirmed by annexin V and PI binding. Lycopene-induced DNA fragmentation was absent after 24 h treatment whereas the same was observed after 48 h treatment. There was a significant decrease in the IGF-IR expression after the cells were treated with lycopene and IGF-I. Conclusion The data obtained suggest that the components of the IGF system may act as a positive regulator of lycopene-induced apoptosis in PC-3 cells. Thus, the observed lycopene-induced biological effects and their associated mechanisms are encouraging and may lead to the development of a highly successful drug for the treatment of prostate cancer.     

Differences and relationships of thymidine phosphorylase expression in tumor-associated macrophages and cancer cells in squamous cell carcinoma of the esophagus

Thymidine phosphorylase (TP), which has been shown to be identical to platelet-derived endothelial cell growth factor, is expressed in tumor-associated macrophages (TAMs) as well as cancer cells. The aim of this study was to clarify the differences or relationships of TP expression in TAMs and cancer cells in esophageal squamous cell carcinoma (SCC). Tissues samples were taken from 56 patients with esophageal SCC after curative surgery. The expression of TP in TAMs or SCC cells was examined using a monoclonal antibody to TP (clone 654-1). Microvessels in SCC that stained positively for Factor VIII-related antigen were counted (microvessel density, MVD). Macrophages in SCC that stained positively for CD68 antigen were counted (monocytic count). Ki-67 antigen was immunostained with MIB-1, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate biotin nick end labeling was performed, and Ki-67 labeling index (LI) and apoptotic index were calculated. The expression of TP in stromal cells and cancer cells was observed in 43 (76.8%) and 33 patients (58.9%), respectively. There were significant correlations between TP expression in stromal cells (TAMs) as well as in cancer cells and venous invasion, distant metastasis, or MVD. There was a correlation between TP expression in cancer cells and lymph node metastasis, and there were correlations between TP expression in TAMs and monocytic count or Ki-67 LI; however, there was no correlation between TP expression in TAMs and lymph node metastasis. On the other hand, in SCCs with TP expression in both TAMs and cancer cells, higher frequencies of venous invasion and distant metastasis, higher MVD and lower apoptotic index were observed than in other SCCs. The 5-year survival rate in patients with TP expression in both TAMs and cancer cells was poorer than that in patients with TP expression in neither TAMs and cancer cell. In conclusion, these results suggest that co-expression of TP in TAMs and cancer cells is strongly associated with angiogenic promotion and distant metastasis. However, other effects of TP, such as promotion of tumor growth and lymph node metastasis, may be different depending on whether these are expressed in TAMs or cancer cells in esophageal SCCs. Patients with coexpression of TP in TAMs and cancer cells may be associated with a poor prognosis.     

Effect of insulin-like growth factor I on HIV type 1 long terminal repeat-driven chloramphenicol acetyltransferase expression.

In this study, we have investigated the ability of insulin-like growth factor I (IGF-I) to inhibit HIV long terminal repeat (LTR)-driven gene expression. Using COS 7 cells cotransfected with tat and an HIV LTR linked to a chloramphenicol acetyltransferase (CAT) reporter, we observed that physiological levels of IGF-I (10(-9) M) significantly inhibited CAT expression in a concentration- and time-dependent manner. IGF-I did not inhibit CAT expression in COS 7 cells transfected with pSVCAT, and did not affect CAT expression in the absence of cotransfection with tat. Transfection of HIV-1 proviral DNA into COS 7 cells +/- IGF-I resulted in a significant decrease (p < 0.05) in infectious virion production. Both IGF-I and Ro24-7429 inhibited LTR-driven CAT expression, while TNF-alpha-enhanced CAT expression was not affected by IGF-I. On the other hand, a plasmid encoding parathyroid hormone-related peptide exhibited dramatic additivity of inhibition of CAT expression in COS 7 cells. Finally, we show that in Jurkat or U937 cells cotransfected with HIVLTRCAT/tat, IGF-I significantly inhibited CAT expression. Further, interleukin 4 showed in U937 cells inhibition of CAT expression that was not additive to IGF-I induced inhibition. Our data demonstrate that IGF-I can specifically inhibit HIVLTRCAT expression. This inhibition may occur at the level of the tat/TAR interaction. Finally, this IGF-I effect is seen in target cell lines and similar paths of inhibition may be involved in the various cell types employed.     

Transfer of foreign genes into intact maize cells with high-velocity microprojectiles

This report describes a process for delivering foreign genes into maize cells that does not require the removal of cell walls and is capable of delivering DNA into embryogenic and nonembryogenic tissues. Plasmid harboring a chimeric chloramphenicol acetyltransferase (CAT) gene was adsorbed to the surface of microscopic tungsten particles (microprojectiles). These microprojectiles were then accelerated to velocities sufficient for penetrating the cell walls and membranes of maize cells in suspension culture. High levels of CAT activity were consistently observed after bombardment of cell cultures of the cultivar Black Mexican Sweet, which were comparable to CAT levels observed after electroporation of protoplasts. Measurable increases in CAT levels were also observed in two embryogenic cell lines after bombardment. Gene expression was observed only when an intron from the alcohol dehydrogenase 1 gene of maize was ligated between the 35S promoter and the CAT coding region. CAT activity was detected in cell cultures bombarded with microprojectiles with an average diameter of 1.2 μm, but not after bombardment with microprojectiles 0.6 or 2.4 μm in diameter. Bombarding the same sample several times was found to markedly enhance CAT activity. These results demonstrate that the particle bombardment process can be used to deliver foreign DNA into intact cells of maize. Because this process circumvents the difficulties associated with regenerating whole plants from protoplasts, the particle bombardment process may provide significant advantages over existing DNA delivery methods for the production of transgenic maize plants. In addition, the process should be of value for studying transient and stable gene expression within intact cells and tissues.     

Thromboprophylaxis of cancer patients undergoing systemic therapy in the ambulatory setting

Cancer-associated Thrombosis (CAT) is a common complication among patients with cancer which is associated with significant morbidity and mortality. The risk of CAT varies widely depending on cancer types and treatments and its cumulative incidence increases over time. Although patients with cancer have a high risk of developing venous thromboembolism, pharmacological thromboprophylaxis is not routinely recommended for ambulatory patients receiving chemotherapy but is suggested for those deemed as high-risk. Risk assessment models can help clinicians identify ambulatory patients at high risk who would most benefit from thromboprophylaxis with low molecular weight heparin or direct oral anticoagulants (apixaban or rivaroxaban). This narrative review will summarize the data on pharmacological thromboprophylaxis in ambulatory patients with cancer, provide further insights into the safety and efficacy of different anticoagulants, and suggest implementation methods using a multidisciplinary approach leading to an optimization of preventative strategies in this patient population.     

Insulin-like growth factor binding protein-3 expression is associated with growth stimulation of T47D human breast cancer cells: the role of altered epidermal growth factor signaling

IGF binding protein (IGFBP)-3 has antiproliferative and proapoptotic effects on the growth of human breast cancer cells in vitro. However, clinical studies suggest that high levels of IGFBP-3 in breast tumor tissue are associated with large, highly proliferative tumors. In this study, we examined the effects of stable transfection with human IGFBP-3 cDNA on the growth of T47D human breast cancer cells in vitro and in vivo. Expression of IGFBP-3 initially inhibited the growth of T47D in vitro but was associated with enhanced growth in vivo. Furthermore, IGFBP-3-expressing cells in vitro became growth stimulated at higher passages post transfection, suggesting breast cancer cells may switch their response to IGFBP-3 with increasing tumorigenicity. These stimulatory effects observed in IGFBP-3-expressing cells were associated with an enhanced responsiveness to the proliferative effects of epidermal growth factor (EGF). When EGF receptor (EGFR) kinase activity was blocked using PD153035, high passage IGFBP-3 transfectants were growth inhibited compared with controls treated with inhibitor. These findings suggest that the interaction between IGFBP-3 and the EGFR system is central to whether IGFBP-3 acts as a growth stimulator or inhibitor in breast cancer cells and that therapies targeting EGFR may have increased efficacy in breast tumors expressing high levels of IGFBP-3.     

The human immunodeficiency virus type-1 Tat protein upregulates Bcl-2 gene expression in Jurkat T-cell lines and primary peripheral blood mononuclear cells

The regulatory Tat protein of human immunodeficiency virus type-1 (HIV- 1) exerts a pleyotropic activity on the survival and proliferation of different cell types in culture. In this report, we investigated the effect of either endogenous or exogenous Tat on Bcl-2 proto-oncogene expression and cell survival in Jurkat T-cell lines and primary peripheral blood mononuclear cells. Stable and transient transfections of Jurkat cells with the cDNA of tat and a plasmid containing Bcl-2 promoter in front of CAT (Bcl-2 Pr/CAT) stimulated CAT activity and showed an increase of Bcl-2 mRNA and protein expression. This effect was specifically related to tat, because Jurkat cells transfected with the cDNA of tat in antisense orientation, tat carrying a mutation in the amino acid cys22-gly22, or the control vector alone (pRPneo-SL3) did not show any significant difference in Bcl-2 promoter activity with respect to parental Jurkat cells. We also observed a specific correlation between tat-induced Bcl-2 gene expression and inhibition of apoptosis induced by serum withdrawal. Our results suggest that the structural integrity of the activation domain of Tat was required for the promotion of the Bcl-2 promoter and Jurkat cell survival, because a single mutation in the aminoacid cys22 was sufficient to completely block the upregulation of Bcl-2 and inhibition of apoptosis. Moreover, picomolar concentrations of native or recombinant Tat were able to upregulate Bcl-2 expression both in Jurkat and primary peripheral blood mononuclear cells, suggesting that extracellular Tat, actively released by infected cells, may also play a significant role in suppressing apoptosis. An aberrant cell survival of lymphoid cells consequent to the upregulation of Bcl-2 may represent an additional pathogenetic mechanism that could help explain both the dysregulated immune response and the frequent occurrence of hyperplastic/neoplastic disorders in HIV- 1-seropositive individuals.     

A cancer-associated PCNA expressed in breast cancer has implications as a potential biomarker

Two isoforms of proliferating cell nuclear antigen (PCNA) have been observed in breast cancer cells. Commercially available antibodies to PCNA recognize both isoforms and, therefore, cannot differentiate between the PCNA isoforms in malignant and nonmalignant breast epithelial cells and tissues. We have developed a unique antibody that specifically detects a PCNA isoform (caPCNA) associated with breast cancer epithelial cells grown in culture and breast-tumor tissues. Immunostaining studies using this antibody suggest that the caPCNA isoform may be useful as a marker of breast cancer and that the caPCNA-specific antibody could potentially serve as a highly effective detector of malignancy. We also report here that the caPCNA isoform functions in breast cancer-cell DNA replication and interacts with DNA polymerase delta. Our studies indicate that the caPCNA isoform may be a previously uncharacterized detector of breast cancer.     

Angiotensin II Type 1 Receptor Expression in Human Gastric Cancer and Induces MMP2 and MMP9 Expression in MKN-28 Cells

Angiotensin II (Ang II), a main effector peptide in the renin–angiotensin system, acts as a growth-promoting and angiogenic factor via angiotensin II receptor1 (AT1R). In this study, we investigated the expression of angiotensin II type1 receptor (AT1R) in gastric cancer and the effects of Ang II on the expression of MMP2 and MMP9 in the human gastric cancer cell line MKN-28 cells. The expression of the Ang II type I receptor was examined by western and immunocytochemistry in gastric cancer cell lines and detected by real-time PCR and immunohistochemistry in normal and gastric cancer tissues. The expression of MMP2 and MMP9 were detected by real-time PCR and western after treatment with Ang II and/or AT1R antagonist. AT1R were expressed in all human gastric cancer lines and the expression of AT1R was significantly higher in cancer tissues than that in normal gastric tissues (P < 0.01). Furthermore, Ang II promoted the expression of MMP2 and MMP9 in MKN-28 cells, and the stimulatory effects of Ang II could be blocked by AT1R antagonist. These results suggest that AT1R is involved in the progression of gastric cancer and may promote the angiogenesis of gastric cancer cell line (MKN-28), and these effects may be associated with the upregulation of MMP2 and MMP9.     

Exposure to xenobiotic compounds: looking for new biomarkers

A variety of antropogenic compounds that have an estrogenic effect, and are known to be present in the environment, shows a significant potential for interference with the health and reproduction of both wildlife and humans. In this review, the effect of estrogenic and antiestrogenic chemicals with widely divergent potencies-nonylphenol (NP), which acts by binding with the estradiol response element, and beta-naphthoflavone (beta-NF), a dioxin-like compound that exerts its toxic action through the aryl hydrocarbon receptor-was compared with that induced by 17beta-estradiol (E(2)) in a marine teleost, the Gobius niger, under controlled laboratory experiments. The capacity of these compounds to affect the levels of estrogen-regulated proteins such as cathepsin D (CAT D)-in humans, a protein associated with the development of breast cancer, and, in oviparous vertebrates, with reproductive success-was assessed. The results of this study showed that both the estradiol and the higher dose of NP induce CAT D gene expression and its associated activity. On the contrary, beta-NF treatments inhibited CAT D gene expression and, at lengthier exposure (96 h), its enzymatic activity. Based on these results, we suggest CAT D as a novel bioindicator of the presence of endocrine-disrupting substances in the environment. The other biomarker assessed in this study is the Heath Shock Protein 70 (HSP70); this protein protects cells against harmful conditions by binding and refolding damaged proteins. Interestingly, HSP70 was found to be affected by all the toxicant compounds employed in the study. The HSP70 gene expression was significantly increased by both NP concentrations and the exposure time of beta-NF, with the E(2) being the most potent inducer. These data indicate that HSP70 may provide a useful early warning biomarker for studies on the presence of exogenous pollutants in the environment.     

Transfected endometrial cultured cells: a system to study gene-regulation by estrogens.

Glandular epithelial (GE) and stromal cells were isolated from guinea-pig endometrium, cultured and subcultured separately. At the end of subculture, the purity of each cell population was higher than 95% and cells displayed a high level of estrogen receptors. Calcium phosphate transfection conditions were defined using a control plasmid containing the bacterial CAT gene driven by viral promoter and enhancer sequences. Transfection experiments were performed with other plasmids in which CAT gene was linked to different estrogen response elements (EREs) derived from those of vitellogenin genes. CAT activity was significantly increased by estradiol-17 beta treatment only when GE or stromal cells were transfected with plasmids containing EREs previously reported as functional EREs in other cell types. This induction was abolished by ICI 164,384 diethylstilbestrol was as effective as estradiol-17 beta for CAT induction and estradiol-17 alpha was ineffective. Transiently transfected endometrial cells in subculture are a suitable system to study the estrogen effect on gene regulatory elements.