Amiodarone inhibits the Toll-like receptor 3-mediated nuclear factor κB signaling pathway by blocking organelle acidification.

Toll-like receptor (TLR) agonists or pro-inflammatory cytokines converge to activate the nuclear factor κB (NF-κB) signaling pathway, which provokes inflammatory responses. In the present study, we identified amiodarone hydrochloride as a selective inhibitor of the TLR3-mediated NF-κB signaling pathway by screening the RIKEN NPDepo Chemical Library. In human umbilical vein endothelial cells (HUVEC), amiodarone selectively inhibited the expression of intercellular adhesion molecule-1 (ICAM-1) induced by polyinosinic-polycytidylic acid (Poly(I:C)), but not tumor necrosis factor-α, interleukin-1α, or lipopolysaccharide. In response to a Poly(I:C) stimulation, amiodarone at 20 µM reduced the up-regulation of mRNA expression encoding ICAM-1, vascular cell adhesion molecule-1, and E-selectin. The nuclear translocation of the NF-κB subunit RelA was inhibited by amiodarone at 15-20 µM in Poly(I:C)-stimulated HUVEC. Amiodarone diminished the fluorescent dots of LysoTracker® Red DND-99 scattered over the cytoplasm of HUVEC. Therefore, the present study revealed that amiodarone selectively inhibited the TLR3-mediated NF-κB signaling pathway by blocking the acidification of intracellular organelles.

Alantolactone derivatives inhibit the tumor necrosis factor α-induced nuclear factor κB pathway by a different mechanism from alantolactone.

Alantolactone is a eudesmane-type sesquiterpene lactone that exerts various biological effects, including anti-inflammatory activity. In the present study, screening using the RIKEN Natural Products Depository chemical library identified alantolactone derivatives that inhibited the expression of intercellular adhesion molecule-1 (ICAM-1) on human umbilical vein endothelial cells stimulated with proinflammatory cytokines and Toll-like receptor ligands. In human lung adenocarcinoma A549 cells stimulated with tumor necrosis factor-α (TNF-α), six alantolactone derivatives inhibited ICAM-1 expression in a dose-dependent manner and at IC50 values of 13-21 µM, whereas that of alantolactone was 5 µM. Alantolactone possesses an α-methylene-γ-lactone moiety, whereas alantolactone derivatives do not. In the nuclear factor κB (NF-κB) signaling pathway, alantolactone prevented the TNF-α-induced phosphorylation and degradation of the inhibitor of NF-κB α (IκBα) protein, and its downstream signaling pathway. In contrast, alantolactone derivatives neither reduced TNF-α-induced IκBα degradation nor the nuclear translocation of the NF-κB subunit RelA, but inhibited the binding of RelA to the ICAM-1 promoter. The inhibitory activities of alantolactone and alantolactone derivatives were attenuated by glutathione. These results indicate that alantolactone derivatives inhibit the TNF-α-induced NF-κB pathway by a different mechanism from alantolactone.

Lonidamine and domperidone inhibit expansion of transformed cell areas by modulating motility of surrounding nontransformed cells.

Cancer cells intrinsically proliferate in an autonomous manner; however, the expansion of cancer cell areas in a tissue is known to be regulated by surrounding nontransformed cells. Whether these nontransformed cells can be targeted to control the spread of cancer cells is not understood. In this study, we established a system to evaluate the cancer-inhibitory activity of surrounding nontransformed cells and screened chemical compounds that could induce this activity. Our findings revealed that lonidamine (LND) and domperidone (DPD) inhibited expansion of oncogenic foci of KRASG12D-expressing transformed cells, whereas they did not inhibit the proliferation of monocultured KRASG12D-expressing cells. Live imaging revealed that LND and DPD suppressed the movement of nontransformed cells away from the attaching cancer cells. Moreover, we determined that LND and DPD promoted stress fiber formation, and the dominant-negative mutant of a small GTPase RhoA relieved the suppression of focus expansion, suggesting that RhoA-mediated stress fiber formation is involved in the inhibition of the movement of nontransformed cells and focus expansion. In conclusion, we suggest that elucidation of the mechanism of action of LND and DPD may lead to the development of a new type of drug that could induce the anticancer activity of surrounding nontransformed cells.

Teratogenicity and Fetal-Transfer Assessment of the Retinoid X Receptor Agonist Bexarotene.

Bexarotene, a retinoid X receptor (RXR) agonist, is used to treat cutaneous T-cell lymphoma, and drug repositioning research has also been reported, despite warnings of teratogenicity. However, fetal transfer of bexarotene and its effect on rat fetal bone formation have not been examined. In this study, we conducted a detailed teratogenicity and fetal transferability assessment of bexarotene in rats. Repeated administration of bexarotene during pregnancy caused marked fetal atrophy and bone dysplasia. Although fetal transfer was not detectable by dynamic imaging of [11C]bexarotene by means of positron emission tomography, transfer to the fetus was confirmed by using a gamma counter. Similar levels were found in mother and fetus. In addition, we found that bexarotene was accumulated in the placenta. These findings will be useful for the toxicity assessment of bexarotene as well as for drug discovery research targeting RXR agonists, which are expected to have therapeutic effects in various diseases.

Application of the Luminescence Syncytium Induction Assay to Identify Chemical Compounds That Inhibit Bovine Leukemia Virus Replication.

Bovine leukemia virus (BLV) infection causes endemic bovine leukemia and lymphoma, resulting in lower carcass weight and reduced milk production by the infected cattle, leading to economic losses. Without effective measures for treatment and prevention, high rates of BLV infection can cause problems worldwide. BLV research is limited by the lack of a model system to assay infection. To overcome this, we previously developed the luminescence syncytium induction assay (LuSIA), a highly sensitive and objectively quantifiable method for visualizing BLV infectivity. In this study, we applied LuSIA for the high-throughput screening of drugs that could inhibit BLV infection. We screened 625 compounds from a chemical library using LuSIA and identified two that markedly inhibited BLV replication. We then tested the chemical derivatives of those two compounds and identified BSI-625 and -679 as potent inhibitors of BLV replication with low cytotoxicity. Interestingly, BSI-625 and -679 appeared to inhibit different steps of the BLV lifecycle. Thus, LuSIA was applied to successfully identify inhibitors of BLV replication and may be useful for the development of anti-BLV drugs.

Fluorine-18 (18F)-labeled retinoid x receptor (RXR) partial agonist whose tissue transferability is affected by other RXR ligands.

Bexarotene (1), a retinoid X receptor (RXR) agonist approved for the treatment of cutaneous T cell lymphoma (CTCL), was reported to migrate into baboon brain based on findings obtained by positron emission tomography (PET) with a 11C-labeled tracer. However, co-administration of non-radioactive 1 had no effect on the distribution of [11C]1, probably due to non-specific binding of 1 as a result of its high lipophilicity. Here, we report a fluorine-18 (18F)-labeled PET tracer [18F]6 derived from RXR partial agonist CBt-PMN (2), which has lower lipophilicity and weaker RXR-binding ability than [11C]1. The concomitant administration of 1 or 2 with [18F]6 with resulted in decreased accumulation of [18F]6 in liver, together with increased brain uptake and increased accumulation in kidney and muscle, as visualized by PET. A plausible explanation of these findings is the inhibition of [18F]6 uptake into the liver by concomitantly administered 1 or 2, leading to an increase in blood concentration of [18F]6 followed by increased accumulation in other tissues.

Development of Mirror-Image Screening Systems for XIAP BIR3 Domain Inhibitors.

The X-linked inhibitor of apoptosis protein baculovirus IAP repeat (XIAP BIR3) domain is a promising therapeutic target for cancer treatment. For the mirror-image screening campaign to identify drug candidates from an unexplored mirror-image natural product library, a facile synthetic protocol for XIAP BIR3 domain synthesis was established by a native chemical ligation strategy using conserved cysteines present among BIR domains. The native and mirror-image XIAP BIR3 domains with an appropriate functional group for labeling were prepared using the established protocol. Taking advantage of the resulting synthetic proteins, several bioassay systems were developed to characterize inhibitors of the protein-protein interaction between the XIAP BIR3 domain and the second mitochondria-derived activator of caspases.

Chemical array system, a platform to identify novel hepatitis B virus entry inhibitors targeting sodium taurocholate cotransporting polypeptide.

Current anti-hepatitis B virus (HBV) agents including interferons and nucleos(t)ide analogs efficiently suppress HBV infection. However, as it is difficult to eliminate HBV from chronically infected liver, alternative anti-HBV agents targeting a new molecule are urgently needed. In this study, we applied a chemical array to high throughput screening of small molecules that interacted with sodium taurocholate cotransporting polypeptide (NTCP), an entry receptor for HBV. From approximately 30,000 compounds, we identified 74 candidates for NTCP interactants, and five out of these were shown to inhibit HBV infection in cell culture. One of such compound, NPD8716, a coumarin derivative, interacted with NTCP and inhibited HBV infection without causing cytotoxicity. Consistent with its NTCP interaction capacity, this compound was shown to block viral attachment to host hepatocytes. NPD8716 also prevented the infection with hepatitis D virus, but not hepatitis C virus, in agreement with NPD8716 specifically inhibiting NTCP-mediated infection. Analysis of derivative compounds showed that the anti-HBV activity of compounds was apparently correlated with the affinity to NTCP and the capacity to impair NTCP-mediated bile acid uptake. These results are the first to show that the chemical array technology represents a powerful platform to identify novel viral entry inhibitors.

Human ABC transporter ABCG2 in cancer chemotherapy: drug molecular design to circumvent multidrug resistance.

Human ATP-binding cassette (ABC) transporter ABCG2 (BCRP) is critically involved in multidrug resistance of human cancer. This transporter exhibits broad substrate specificity toward structurally diverse compounds, as do other ABC transporters, such as ABCB1 (P-glycoprotein/MDR1), ABCC1 (MRP1/GS-X pump), and ABCC2 (MRP2/cMOAT). To gain insight into the relationship between the molecular structure of compounds and the ABCG2-mediated transport activity, we have developed a high-speed screening method to analyze the substrate specificity of ABCG2. In addition, we have developed an algorithm that analyzes QSAR to evaluate ABCG2-drug interactions. This chapter presents our strategy of transport mechanism-based molecular design to circumvent multidrug resistance of cancer.

Emerging new technology: QSAR analysis and MO Calculation to characterize interactions of protein kinase inhibitors with the human ABC transporter, ABCG2 (BCRP).

Protein kinases are potential drug targets for the treatment of a variety of diseases, including cancer. In particular, specific tyrosine kinase inhibitors are rapidly being developed as new drugs for the inhibition of malignant cell growth and metastasis formation. Most of these newly developed tyrosine kinase inhibitors are hydrophobic and thus rapidly penetrate the cell membrane to reach intracellular targets. However, intracellular accumulation of a drug is regulated by multiple factors, including influx and efflux as well as metabolism. In cancer chemotherapy, overexpression of drug efflux transporters in cancer cells is a major cause of multidrug resistance that reduces the efficacy of anticancer drugs. Thus, the transport mechanism-based molecular design strategy would provide an effective tool for chemotherapy against cancer. To develop a platform for molecular modeling to circumvent multidrug resistance and reduce drug-induced adverse effects, we established methods for high-speed screening for human ABCG2-drug interactions, quantitative structure-activity relationship (QSAR) analysis, and quantum chemical calculation for lead optimization. This review addresses recent advances in the strategy of transport mechanism-based molecular design.

Emerging new technologies in Pharmacogenomics: rapid SNP detection, molecular dynamic simulation, and QSAR analysis methods to validate clinically important genetic variants of human ABC Transporter ABCB1 (P-gp/MDR1).

Pharmacogenomics, the study of the influence of genetic factors on drug action, is increasingly important for predicting pharmacokinetics profiles and/or adverse reactions to drugs. Drug transporters as well as drug-metabolism play pivotal roles in determining the pharmacokinetic profiles of drugs and, by extension, their overall pharmacological effects. There are an increasing number of reports addressing genetic polymorphisms of drug transporters. A key requirement for the development of individualized medicine or personalized therapy is the ability to rapidly and conveniently test patients for genetic polymorphisms and/or mutations. We have recently developed a rapid and cost-effective method for single nucleotide polymorphism (SNP) detection, named Smart Amplification Process 2 (SmartAmp2), which enables us to detect genetic polymorphisms or mutations in 30 to 45min under isothermal conditions without DNA isolation and PCR amplification. Furthermore, high-speed functional screening, quantitative structure-activity relationship (QSAR) analysis, and molecular dynamic (MD) simulation methods have been developed to study the substrate specificity of ABC transporters and to evaluate the effect of genetic polymorphisms on their function and substrate specificity. These methods would provide powerful and practical tools for screening synthetic and natural compounds, and the deduced data can be applied to the molecular design of new drugs. This review addresses such new methods for validating genetic polymorphisms of human ABC transporter ABCB1 (P-gp/MDR1) which is critically involved in the pharmacokinetics of drugs.

Inhibition of P-glycoprotein by wogonin is involved with the potentiation of etoposide-induced apoptosis in cancer cells.

Etoposide induces apoptotic cell death in normal and cancer cells. This apoptosis plays a role not only in anticancer effects but also in adverse reactions, such as myelosuppression. Because we had previously found that wogonin, a flavone found in a plant, suppresses thymocyte apoptosis induced by etoposide, we examined the effect of this flavone in cancer cells. Wogonin significantly potentiated etoposide-induced apoptosis in HL-60 cells. This flavone impaired the function of P-glycoprotein and then increased cellular content of etoposide in the cells. Thus, this flavone is likely to act as an inhibitor of P-glycoprotein and potentiate the apoptotic action of etoposide. On the other hand, wogonin inhibited etoposide-induced apoptosis in thymocytes, one of the normal cells. The potentiation by wogonin is likely to be a specific action for cancer cells but not normal cells. Therefore, this flavone may be used to reduce the excretion of the anticancer agents via P-glycoprotein and increase the pharmacological action of it in cancer cells. These results suggest that wogonin may play a role in overcoming multidrug resistance.

Technical pitfalls and improvements for high-speed screening and QSAR analysis to predict inhibitors of the human bile salt export pump (ABCB11/BSEP).

Drug-induced hepatotoxicity is one of the major problems encountered in drug discovery and development. Selection of a candidate compound for pre-clinical studies in the drug discovery process is a critical step that can determine the speed and expenditure of clinical development. Because inhibition of human adenosine triphosphate-binding cassette transporter ABCB11 (SPGP/bile salt export pump) has severe consequences, which include intrahepatic cholestasis and hepatotoxicity, resulting from exposure to toxic xenobiotics or drug interactions, in vitro screening methods are necessary for quantifying and characterizing the inhibition of ABCB11. In line with such initiatives, we developed methods for in vitro high-speed screening and quantitative structure-activity relationship (QSAR) analysis to investigate the interaction of ABCB11 with a variety of compounds. We identified one set of chemical fragmentation codes closely linked with inhibition of ABCB11. Furthermore, the high-speed screening method enables us to analyze the kinetics of ABCB11-inhibition by test compounds and to distinguish competitive and non-competitive inhibitors. Troglitazone and novobiocin were found to be competitive inhibitors to taurocholate, whereas porphyrins were non-competitive inhibitors. Kinetics-based classification of inhibitors is considered important to improve the accuracy of our QSAR analysis. The present mini-review addresses technical pitfalls and improvements for high-speed screening and QSAR analysis in the ABCB11 inhibition study.

Quantitative structure--activity relationship analysis and molecular dynamics simulation to functionally validate nonsynonymous polymorphisms of human ABC transporter ABCB1 (P-glycoprotein/MDR1).

Several preclinical and clinical studies suggest the importance of naturally occurring polymorphisms of drug transporters in the individual difference of drug response. To functionally validate the nonsynonymous polymorphisms of ABCB1 (P-glycoprotein/MDR1) in vitro, we generated SNP variant forms (i.e., S400N, R492C, R669C, I849M, A893P, A893S, A893T, M986V, A999T, P1051A, and G1063A) and expressed them in Sf9 cells. The kinetic properties (Km and Vmax) of those variants were analyzed by measuring the ATPase activity to obtain the ATPase profile for each variant toward structurally unrelated substrates. On the basis of the experimental data, we determined the substrate specificity of ABCB1 WT and its variants by the quantitative structure-activity relationship (QSAR) analysis method. While several SNP variants appeared to influence the substrate specificity of ABCB1, the nonsynonymous polymorphisms of 2677G > T, A, or C at amino acid position 893 (Ala > Ser, Thr, or Pro) have great impacts on both the activity and the substrate specificity of ABCB1. The A893P variant (2677G > C), a rare mutation, exhibited markedly high activity of ATPase toward different test compounds. Molecular dynamics (MD) simulation based on a three-dimensional structural model of human ABCB1 revealed that multiple kinks are formed in the intracellular loop between transmembrane domains 10 and 11 of the A893P variant (2677G > C) protein. The polymorphisms of 2677G, 2677T, and 2677A exhibit wide ethnic differences in the allele frequency, and these nonsynonymous polymorphisms are suggested to be clinically important because of their altered ATPase activity and substrate specificity toward different drugs.

Wogonin, a plant flavone, potentiates etoposide-induced apoptosis in cancer cells.

Etoposide, a podophylotoxin anticancer agent, induces apoptotic cell death in normal and cancer cells. Etoposide-induced apoptosis plays a role in not only anticancer effect but also adverse reaction, such as myelosuppression. Since we have found that wogonin, a flavone found in Scutellaria baicalensis Georgi, prevents thymocyte apoptosis induced by various compounds including etoposide, we examined the effect of this flavone on etoposide-induced apoptosis in cancer cells. Although 100 muM wogonin itself significantly increased DNA fragmentation in HL-60 cells, this change was not observed in Jurkat cells. On the other hand, this flavone significantly potentiated etoposide-induced apoptosis in Jurkat and HL-60 cells. Similarly, wogonin accelerated etoposide-induced cell death in lung cancer cells. Since wogonin had no effect on the action of other anticancer agents, such as 5-FU and cisplatin, this flavone seems to accelerate only etoposide-induced apoptotic cell death in cancer cells. These results suggest that the modification of etoposide-induced apoptosis by wogonin may be available to reduce the adverse reaction of this agent.

High-speed screening and QSAR analysis of human ATP-binding cassette transporter ABCB11 (bile salt export pump) to predict drug-induced intrahepatic cholestasis.

Human ATP-binding cassette transporter ABCB11 (SPGP/BSEP) mediates the elimination of bile salts from liver cells and thereby plays a critical role in the generation of bile flow. In the present study, we have developed in vitro high-speed screening and quantitative structure-activity relationship (QSAR) analysis methods to investigate the interaction of ABCB11 with a variety of drugs. Plasma membrane vesicles prepared from insect cells overexpressing human ABCB11 were used to measure the ATP-dependent transport of [14C]taurocholate. Over 40 different drugs and natural compounds were tested to evaluate their interaction with ABCB11-mediated taurocholate transport. On the basis of the extent of inhibition, we have analyzed the QSAR to identify one set of chemical fragmentation codes closely associated with the inhibition of ABCB11. This approach can be used to predict compounds with a potential risk of drug-induced intrahepatic cholestasis.

A new strategy of high-speed screening and quantitative structure-activity relationship analysis to evaluate human ATP-binding cassette transporter ABCG2-drug interactions.

The human ATP-binding cassette (ABC) transporter ABCG2 (BCRP/MXR1/ABCP) plays a critical role in cellular protection against xenobiotics as well as pharmacokinetics of drugs in our body. In the present study, we aimed to analyze the quantitative structure-activity relationship (QSAR) latently residing in ABCG2-drug interactions. We first established standard methods for expression of human ABCG2 in insect cells, quality control of plasma membrane samples by using electron microscopy techniques, and high-speed screening of ABCG2 inhibition with test compounds. Plasma membrane vesicles prepared from ABCG2-expressing Sf9 cells were used as a model system to measure the ATP-dependent transport of [3H]methotrexate (MTX). Forty-nine different therapeutic drugs and natural compounds were tested for their ability to inhibit ABCG2-mediated MTX transport. Based on their inhibition profiles, we performed QSAR analysis using chemical fragmentation codes deduced from the structures of test compounds. Multiple linear regression analysis delineated a relationship between the structural components and the extent of ABCG2 inhibition, allowing us to identify one set of structure-specific chemical fragmentation codes that are closely correlated with the inhibition of ABCG2 transport activity. Based on the QSAR analysis data, we predicted the potency of gefitinib to inhibit ABCG2. The validity of our QSAR-based prediction for gefitinib was examined by actual experiments. Our kinetic analysis experiments suggest that the ABCG2-ATP complex binds gefitinib. The present study provides a new strategy for analyzing ABCG2-drug interactions. This strategy is considered to be practical and useful for the molecular designing of new ABCG2 modulators.

High-speed screening of human ATP-binding cassette transporter function and genetic polymorphisms: new strategies in pharmacogenomics.

Drug transporters represent an important mechanism in cellular uptake and efflux of drugs and their metabolites. Hitherto a variety of drug transporter genes have been cloned and classified into either solute carriers or ATP-binding cassette (ABC) transporters. Such drug transporters are expressed in various tissues such as the intestine, brain, liver, kidney, and, importantly, cancer cells, where they play critical roles in the absorption, distribution, and excretion of drugs. We developed high-speed functional screening and quantitative structure-activity relationship analysis methods to study the substrate specificity of ABC transporters and to evaluate the effect of genetic polymorphisms on their function. These methods would provide powerful and practical tools for screening synthetic and natural compounds, and the deduced data can be applied to the molecular design of new drugs. Furthermore, we demonstrate a new "SNP array" method to detect genetic polymorphisms of ABC transporters in human samples.

Human gingival epithelial cells produce chemotactic factors interleukin-8 and monocyte chemoattractant protein-1 after stimulation with Porphyromonas gingivalis via toll-like receptor 2.

BACKGROUND: The mechanism of stimulation of human gingival epithelial cells (HGEC) by Porphyromonas gingivalis (Pg) has not been fully clarified yet. In order to investigate the possible activation of HGEC by Pg through Toll-like receptors (TLRs), we analyzed the production of chemotactic factors and the activated nuclear factor-kappa B (NF-kappaB). METHODS: The mRNA expression of TLRs and the protein expression of TLR2 and TLR4 in HGEC and gingival tissue were assessed using reverse transcription-polymerase chain reaction (RT-PCR) assay and immunohistochemical staining. Primary cultured HGEC (nHGEC) and HGEC transformed by simian virus 40 T antigen (OBA-9) were activated by a sonic extract (SE) of Pg to examine cytokine production and NF-kappaB activation using enzyme-linked immunosorbant assay (ELISA). In addition, Pg mediated activation of NF-kappaB in a TLR2-transfectant was also investigated. RESULTS: RT-PCR results revealed that HGEC expressed mRNA of TLR2, TLR4, TLR5, and TLR9, although the expression profiles of each cell line were slightly different. In addition, immunostaining revealed the prominent expression of TLR2 not only in nHGEC, but also in the gingival epithelium of the tissue specimen. Interestingly, nHGEC and OBA-9 secreted IL-8 and monocyte chemoattractant protein (MCP)-1 upon stimulation with Pg SE more efficiently than LPS and fimbriae of Pg. Furthermore, Pg SE increased the activated NF-kappaB not only in OBA-9, but also in 293T cells transfected with the human TLR2 gene. CONCLUSION: TLR2 participates, at least partly, in the signaling pathway to induce chemokine production in gingival epithelium as a reaction against Pg component(s), probably other than lipopolysaccharide and fimbriae.

Effects of basic fibroblast growth factor on human gingival epithelial cells.

BACKGROUND: Our previous reports found that basic fibroblast growth factor (FGF-2; bFGF) influences the proliferation and extracellular matrix production of periodontal ligament (PDL) cells. In this study, we examined FGF-2 expression in gingival epithelium and the effect of FGF-2 on proliferative responses by gingival epithelial (GE) cells. METHODS: Human GE cells were isolated from healthy gingival epithelium, and the mRNA expression of FGF-2 and FGF receptors (FGFRs) was examined by reverse transcription-polymerase chain reaction (RT-PCR). The distribution of FGF-2 in gingival tissues was detected by immunohistological analysis using the monoclonal antibody for human recombinant FGF-2, which was newly established and designated as BF-2. Further, the proliferative responses of GE cells to FGF-2 were investigated by measuring [3H]-thymidine uptake. RESULTS: RT-PCR revealed that GE cells express FGFR-1, FGFR-2, FGFR-3, and FGFR-4 mRNA; however, not that of FGF-2. Employing immunohistochemical staining with BF-2, FGF-2 was observed localized in the intercellular spaces of gingival epithelium, though not in the cytoplasm of epithelial cells. Interestingly, staining by BF-2 in the intercellular spaces was diminished after treatment of the tissue sections with heparitinase. Further, an in vitro analysis revealed that FGF-2 enhanced the proliferative responses of human GE cells. However, costimulation with fetal calf serum inhibited the FGF-2-induced proliferation of GE cells, whereas the same costimulation synergistically enhanced FGF-2-induced PDL cell proliferation. CONCLUSIONS: FGF-2 is anchored in the intercellular spaces of gingival epithelium via heparansulfate and may regulate the growth and cytodifferentiation of GE cells via cell-type specific receptors.