Human Epidermoid Cell Line Research Articles

Synthesis and cytotoxic evaluation of a series of resveratrol derivatives modified in C2 position

Eleven C2-substituted derivatives of resveratrol ( trans-3,4′,5-trihydroxystilbene, RES) were prepared by partial synthesis from RES and evaluated for their cytotoxic activities against a human nasopharyngeal epidermoid tumor cell line KB. Among them, compounds 2 and 3 were more active than 5-fluorouracil (5-FU), an anticancer drug, and compound 5f exhibited similar activity to 5-FU. On the basis of the biological results, structure–activity relationships were discussed.

Synthesis and Cytotoxic Evaluation of a Series of Resveratrol Derivatives

A total of 17 resveratrol (=(E)-5-[2-(4-hydroxyphenyl)ethenyl]benzene-1,3-diol) derivatives were synthesized from resveratrol (RES) through a facile approach. Among them, 13 compounds, 2 and 6-17, were reported for the first time, while 1 and 3-5 had already been reported several years ago. The cytotoxic activities of these compounds were evaluated against human nasopharyngeal epidermoid tumor cell line KB, and compounds 1 and 8-11 showed strong anticancer activities in vitro, comparable with that of 5-fluorouracil, an anticancer drug. On the basis of the experimental data obtained, structure-activity relationships are discussed.

Cytotoxicity of a Novel Fibroblast Growth Factor Receptor Targeted Immunotoxin on a Human Ovarian Teratocarcinoma Cell Line

Basic fibroblast growth factor (bFGF) is an important tumor-associated growth factor that contributes to proliferation and angiogenesis of tumor. The high-affinity receptor for bFGF, fibroblast growth factor receptor (FGFR), is found to be overexpressed in a number of tumor cells. For the purpose of exploring the significance of bFGF/FGFR in tumor-targeted therapy, a recombinant immunotoxin contained the N-terminal 389 residues of diphtheria toxin (DT), and the full length of human bFGF was designed, expressed, and purified. The bioactivity of the product was evaluated by testing the cytotoxicity on PA-1 cells (a human ovarian teratocarcinoma cell line with high-level expression of FGFR) in vitro. The immunotoxin showed a significant cytotoxicity on PA-1 cells (IC(50) 8 - 9 ng/mL), and this effect could be antagonized by equine diphtheria antitoxin (DAT), bFGF, anti-bFGF monoclonal antibody (MAb), and anti- FGFR polyclonal antibody (PAb), respectively. Additionally, Chinese hamster ovary (CHO) cells and Hep-2 cells (a human epidermoid laryngocarcinoma cell line) with low expression of FGFR were tested to be resistant to the immunotoxin. The results indicated that FGFR might be an effective target for tumor therapy, and bFGF-mediated immunotoxin could be a potential candidate in the treatment of cancer.

Neoplaether, a new cytotoxic and antifungal endophyte metabolite fromNeoplaconema napellumIFB-E016

A new diphenyl ether, named neoplaether, together with five known compounds monomethylsulochrin, physcion, helvolic acid, ergosterol and ergosterol peroxide, was isolated from the culture of Neoplaconema napellum IFB-E016, an endophytic fungus residing in the healthy leaves of Hopea hainanensis. The structure of neoplaether was elucidated by a correlative interpretation of its infrared spectrometry, mass spectroscopy and nuclear magnetic resonance spectra, and confirmed by its single-crystal X-ray diffraction analysis. Neoplaether exhibited significant cytotoxic activity against the human nasopharyngeal epidermoid tumor KB cell line, with an IC(50) value of 13.0 microg mL(-1), comparable to that of 5-fluorouracil (2.5 microg mL(-1)) co-assayed as a positive reference. In addition, it showed antifungal activity against Candida albicans, with a minimal inhibitory concentration value of 6.2 microg mL(-1) (amphotericin as a positive control had a value of 1.5 microg mL(-1)).

Selective Toxicity of NSC73306 in MDR1-Positive Cells as a New Strategy to Circumvent Multidrug Resistance in Cancer

ATP-binding cassette (ABC) proteins include the best known mediators of resistance to anticancer drugs. In particular, ABCB1 [MDR1/P-glycoprotein (P-gp)] extrudes many types of drugs from cancer cells, thereby conferring resistance to those agents. Attempts to overcome P-gp-mediated drug resistance using specific inhibitors of P-gp has had limited success and has faced many therapeutic challenges. As an alternative approach to using P-gp inhibitors, we characterize a thiosemicarbazone derivative (NSC73306) identified in a generic screen as a compound that exploits, rather than suppresses, P-gp function to induce cytotoxicity. Cytotoxic activity of NSC73306 was evaluated in vitro using human epidermoid, ovarian, and colon cancer cell lines expressing various levels of P-gp. Our findings suggest that cells become hypersensitive to NSC73306 in proportion to the increased P-gp function and multidrug resistance (MDR). Abrogation of both sensitivity to NSC73306 and resistance to P-gp substrate anticancer agents occurred with specific inhibition of P-gp function using either a P-gp inhibitor (PSC833, XR9576) or RNA interference, suggesting that cytotoxicity was linked to MDR1 function, not to other, nonspecific factors arising during the generation of resistant or transfected cells. Molecular characterization of cells selected for resistance to NSC73306 revealed loss of P-gp expression and consequent loss of the MDR phenotype. Although hypersensitivity to NSC73306 required functional expression of P-gp, biochemical assays revealed no direct interaction between NSC73306 and P-gp. This article shows that NSC73306 kills cells with intrinsic or acquired P-gp-induced MDR and indirectly acts to eliminate resistance to MDR1 substrates.

Synthesis and Cytotoxic Evaluation of a Series of Genistein Derivatives

Thirty genistein (= 5,7-dihydroxy-3-(4-hydroxyphenyl)-4H-1-benzopyran-4-one; GEN) derivatives were synthesized from genistein through a facile approach in high yields. Compounds 9, 11, 12, 23-30 were reported for the first time, while 13-22 have already been reported in our recent paper. The cytotoxic activities of these compounds were evaluated against a human nasopharyngeal epidermoid tumor cell line KB. Compounds 7-9, 12, 14, 16-19, 21, 24, 27, 29 showed remarkable antitumor activities in vitro, which was comparable with 5-fluorouracil, an anticancer drug. On the basis of the obtained experimental data, structure-effect relationships were discussed.

Chaetoglobosin U, a Cytochalasan Alkaloid from Endophytic Chaetomium globosum IFB-E019

A new cytotoxic cytochalasan-based alkaloid named chaetoglobosin U (1), along with four known analogues, chaetoglobosins C (2), F (3), and E (5) and penochalasin A (4), has been characterized from the EtOAc extract of a solid culture of Chaetomium globosum IFB-E019, an endophytic fungus residing inside the stem of healthy Imperata cylindrica. The structure of chaetoglobosin U was determined through correlative analyses of its UV, IR, CD, MS, and 1D ((1)H and(13)C NMR and DEPT) and 2D NMR (COSY, NOESY, HMQC, and HMBC) data. Chaetoglobosin U (1) exhibited cytotoxic activity against the human nasopharyngeal epidermoid tumor KB cell line with an IC(50) value of 16.0 microM, comparable to that (14.0 microM) of 5-fluorouracil co-assayed as a positive reference. The known analogues 2-5 were moderately active to the cell line, with IC(50) values of 34.0, 52.0, 48.0, and 40.0 microM, respectively.

Antimalarial Compounds from Grewia bilamellata

Bioassay-directed fractionation led to the isolation of 12 compounds from a sample of the dried leaves, twigs, and stems of Grewia bilamellata. Five of the isolates, 3alpha,20-lupandiol (1), grewin (2), nitidanin (4), 2alpha,3beta-dihydroxy-olean-12-en-28-oic acid (5), and 2,6-dimethoxy-1-acetonylquinol (6), showed varying degrees of in vitro antimalarial activity against Plasmodium falciparum, but were devoid of significant cytotoxicity to the human oral epidermoid KB cancer cell line. Of the 12 isolates, compounds 1, 2, and 3 (bilagrewin) were determined to be a new triterpene, a new coumarinolignan, and a new neolignan, respectively. Other known compounds isolated in this study were 8-O-4' neolignan guaiacylglycerol-beta-coniferyl ether isomers (threo and erythro), cleomiscosin D, icariol A(2), ciwujiatone, and daucosterol. The structures of 1-3 were elucidated and identified on the basis of spectroscopic data including 1D and 2D NMR analysis.

Cytotoxic Clerodane Diterpenoids from Casearia membranacea

Bioassay-guided fractionation of the EtOAc extract of Casearia membranacea leaves and twigs afforded three new clerodane diterpenes, caseamembrins M-O (1-3), and the known rel-(2S,5R,6R,8S,9S,10R,18S,19R)-2-(2-methylbutyryloxy)-6-hydroxy-18,19-di-O-acetyl-18,19-epoxycleroda-3,13(16),14-triene (4) and caseamembrin D (5). The structures of 1-3, including the relative configurations, were established by extensive NMR spectroscopic analyses. The cytotoxic activities of the isolated diterpenoids against human oral epidermoid (KB), medulla (Med), and colon (DLD-1) cancer cell lines were evaluated.

Ultraviolet B Radiation Generates Platelet-activating Factor-like Phospholipids underlying Cutaneous Damage

Ultraviolet B light (UVB) causes cutaneous inflammation and cell death, but the agents responsible are not defined. These studies examined the role of the platelet-activating factor (PAF) signaling system in UVB-mediated effects. Expression of the PAF receptor in the PAF receptor-negative epidermoid cell line KB augmented apoptosis in response to UVB irradiation. Overexpression of the PAF receptor in primary human keratinocytes also enhanced UVB-mediated apoptosis in vitro, and it enhanced apoptosis in an in vivo model of human keratinocytes grafted onto severe combined immune-deficient (SCID) mice. To define the mechanism by which UVB activates the PAF receptor, we used mass spectrometry to demonstrate significant amounts of the C4 PAF analogs 1-alkyl-2-(butanoyl and butenoyl)-sn-glycero-3-phosphocholine, as well as native PAF in an epidermal cell line after UVB irradiation. Supplementing the cells with the precursor phospholipid 1-hexadecyl-2-arachidonoyl-sn-glycero-3-phosphocholine (HAPC) increased the amount of C4 PAF analogs recovered after UVB exposure. We irradiated HAPC directly and found, even in the absence of a photosensitizer, fragmentation to C4-PAF receptor ligands. We conclude UVB photo-oxidizes cellular phospholipids, creating PAF analogs that stimulate the PAF receptor to induce further PAF synthesis and apoptosis. PAF signaling may participate in the cutaneous inflammation that occurs during photo-aggravated dermatoses.

Cytotoxic constituents of the twigs of Simarouba glauca collected from a plot in Southern Florida

Activity-guided fractionation of a chloroform-soluble extract of Simarouba glauca twigs collected from a plot in southern Florida, and monitored with a human epidermoid (KB) tumor cell line, afforded six canthin-6-one type alkaloid derivatives, canthin-6-one (1), 2-methoxycanthin-6-one (2), 9-methoxycanthin-6-one (3), 2-hydroxycanthin-6-one (4), 4,5-dimethoxycanthin-6-one (5) and 4,5-dihydroxycanthin-6-one (6), a limonoid, melianodiol (7), an acyclic squalene-type triterpenoid, 14-deacetyleurylene (8), two coumarins, scopoletin (9) and fraxidin (10), and two triglycerides, triolein (11) and trilinolein (12). Among these isolates, compounds 1-4, 7 and 8 exhibited cytotoxic activity against several human cancer cell lines. 14-Deacetyleurylene (8) was selectively active against the Lu1 human lung cancer cell line, but was inactive in an in vivo hollow fiber assay using this same cell type.

Antiproliferative activity of new 1-aryl-4-amino-1 H-pyrazolo[3,4- d]pyrimidine derivatives toward the human epidermoid carcinoma A431 cell line

Synthesis and biological evaluation of a new class of 1-aryl-4-amino-1 H-pyrazolo[3,4- d]pyrimidine derivatives are reported. A preliminary cellular assay system using the tumor cell line A431 responding to epidermal growth factor (EGF) for its growth, shows that the new compounds are potent inhibitors of cell growth. The inhibition of tumor cell proliferation is not associated with blockage of EGF receptor (EGFR), but substantially due to the interference with the signalling pathway at the level of Src tyrosine kinase and at the level of the downstream effector signal mitogen activated protein kinases (MAPKs), ERK1-2.

Messenger RNA expression profiling of genes involved in epidermal growth factor receptor signalling in human cancer cells treated with scanning array-designed antisense oligonucleotides

Scanning oligodeoxynucleotide (ODN) arrays appear promising in vitro tools for the prediction of effective antisense reagents but their usefulness has not yet been reported in mammalian systems. In this study, we have evaluated the use of scanning ODN arrays to predict efficacious antisense ODNs targeting the human epidermal growth factor receptor (EGFR) mRNA in a human epidermoid cancer cell line and in primary human glioma cells. Hybridisation accessibility profile of the first 120 nt in the coding region of the human EGFR mRNA was determined by hybridising a radiolabelled EGFR transcript to a scanning array of 2684 antisense sequences ranging from monomers to 27-mers. Two ODNs, AS1 and AS2, complementary to accessible sequences within the EGFR mRNA, were designed and their ability to hybridise to EGFR mRNA was further confirmed by in vitro RNase H-mediated cleavage assays. Phosphorothioate-modified 21-mer AS1 and AS2 ODNs inhibited the growth of an established human A431 cancer cell line as well as primary glioma cells from human subjects when delivered as cationic lipoplexes. In contrast, scrambled controls and AS3—an antisense ODN complementary to an inaccessible site in EGFR mRNA—were inactive. Western blots showed that AS1 ODN exhibited a dose-dependent inhibition of EGFR protein expression in A431 cells in the nanomolar range. Microarray-based gene expression profiling studies of A431 cells treated with the 21-mer phosphorothioate AS1 ODN demonstrated successful inhibition of downstream signalling molecules further confirming the effective inhibition of EGFR expression in human cancer cells by antisense ODNs designed by scanning ODN array technology.

Combination chemotherapy of paclitaxel and cisplatin induces apoptosis with Bcl-2 phosphorylation in a cisplatin-resistant human epidermoid carcinoma cell line.

Paclitaxel (Taxol, TXL) is an antimicrotubule agent that stabilizes microtubules, arrests the cell cycle at the G(2)/M phase and induces apoptosis. In vitro drug sensitivity assays have shown that the combination of TXL and CDDP is more effective in CDDP-resistant ovarian carcinoma cell lines, with different cytotoxicities depending on the sequence of drug exposure. CDDP also shows poor results in human epidermoid carcinoma particularly of the head and neck region. We investigated the effects and the molecular mechanisms of combination chemotherapy with TXL and CDDP in the CDDP-resistant cell line A431/CDDP2, and in its parental human epidermoid cell line A431/P. Drug sensitivity was determined using the MTS assay and cell cycle perturbation was analyzed using flow cytometry. DNA fragmentation was then analyzed and the protein levels of caspase-3 and Bcl-2, and phosphorylated of Bcl-2 were determined by Western blotting. In the drug sensitivity assay, exposure to CDDP prior to TXL was more effective than exposure TXL prior to CDDP in A431/P cells. In A431/CDDP2 cells, exposure to TXL prior to CDDP was more effective than exposure to CDDP prior to TXL. Exposure to TXL arrested the cells in the G(2)/M phase in both cell lines. In A431/CDDP2 cells, exposure to TXL prior to CDDP arrested the cells in the G(2)/M phase, an effect caused by either CDDP or TXL. Analysis of DNA fragmentation showed similar results to the drug sensitivity assay. Expression of caspase-3 protein active form was detected following exposure to TXL only and to the TXL/CDDP combination in both A431/P and A431/CDDP2 cells, but phosphorylation of Bcl-2 protein was detected only following exposure to TXL and only in A431/CDDP2 cells. These results indicate that exposure to TXL prior to CDDP plays a key role in circumventing CDDP resistance by phosphorylating Bcl-2 protein in the human epidermoid carcinoma cell line A431/CDDP2.

Radiation therapy depletes extrachromosomally amplified drug resistance genes and oncogenes from tumor cells via micronuclear capture of episomes and double minute chromosomes

Purpose: To determine if clinically relevant doses of ionizing radiation are capable of inducing extrachromosomal DNA loss in transformed human cell lines. Methods and materials: The multidrug-resistant (MDR) human epidermoid KB-C1 cell line and the human neuroendocrine colon carcinoma line COLO320, which contain extrachromosomally amplified MDR1 drug resistance genes and MYCC oncogenes, were irradiated with 2 Gy fractions up to a total dose of 28 Gy. To track the fate of extrachromosomally amplified genes, cells surviving radiation therapy and unirradiated control cells were analyzed by fluorescent in situ hybridization of chromosomes using MDR1 and MYCC-specific cosmid DNA probes. In addition, total DNA and protein isolated from irradiated and control cells was subjected to Southern and Western blotting procedures, respectively, to determine amplified gene copy number and protein expression levels. Dose–response assays to follow loss of function of the MDR1 gene from KB-C1 cells were also performed. Results: A significant reduction in extrachromosomal DNA, amplified gene copy number, and expression was detected in surviving cells after relatively low doses of radiation. Entrapment of extrachromosomal DNA into micronuclei was a consistent feature of irradiated cells. Conclusions: Clinically relevant doses of radiation can deplete extrachromosomal DNA in viable human malignant cells and alter their phenotype. Depletion of extrachromosomally amplified genes from tumor cells occurs via entrapment in radiation-induced micronuclei.

Affinity adsorption of glucose degradation products improves the biocompatibility of conventional peritoneal dialysis fluid

Reactive carbonyl compounds (RCOs) present in peritoneal dialysis (PD) fluid have been incriminated in the progressive deterioration of the peritoneal membrane in long-term PD patients. They are initially present in fresh conventional heat-sterilized glucose PD fluid and are supplemented during dwell time by the diffusion of blood RCOs within the peritoneal cavity. In the present study, RCO entrapping agents were immobilized on affinity beads to adsorb RCOs both in fresh PD fluid and in PD effluent. The RCO trapping potential of various compounds was assessed in vitro first by dissolving them in the tested fluid and subsequently after coupling with either epoxy- or amino-beads. The tested fluids include fresh heat-sterilized glucose and non-glucose PD fluids, and PD effluent. Their RCOs contents, that is, glyoxal (GO), methylglyoxal (MGO), 3-deoxyglucosone (3-DG), formaldehyde, 5-hydroxymethylfuraldehyde, acetaldehyde, and 2-furaldehyde were monitored by reverse-phase high-pressure liquid chromatography. The biocompatibility of PD fluid was assessed by a cytotoxic assay with either human epidermoid cell line A431 cells or with primary cultured human peritoneal mesothelial cells. Among the tested RCO entrapping agents, hydrazine coupled to epoxy-beads proved the most efficient. It lowered the concentrations of three dicarbonyl compounds (GO, MGO, and 3-DG) and those of aldehydes present in fresh heat-sterilized glucose PD fluid toward the low levels observed in filter-sterilized glucose PD fluid. It did not change the glucose and electrolytes concentration of the PD fluid but raised its pH from 5.2 to 5.9. Hydrazine-coupled epoxy-bead also lowered the PD effluent content of total RCOs, measured by the 2,4-dinitrophenylhydrazone (DNPH) method. The cytotoxicity of heat-sterilized PD fluid incubated with hydrazine-coupled epoxy-beads was decreased to the level observed in filter-sterilized PD fluid as the result of the raised pH and the lowered RCOs levels. Hydrazine-coupled epoxy-beads reduce the levels of a variety of dicarbonyls and aldehydes present in heat-sterilized glucose PD fluid to those in filter-sterilized PD fluid, without altering glucose, lactate, and electrolytes contents but with a rise in pH. Incubated with PD effluents, it is equally effective in reducing the levels of serum-derived RCOs. RCO entrapping agents immobilized on affinity beads improve in vitro the biocompatibility of conventional heat-sterilized glucose PD fluid. Their clinical applicability requires further studies.

Cytotoxic flavonoids from the stem bark of Lonchocarpus aff. fluvialis.

Activity-guided fractionation of a chloroform-soluble extract of Lonchocarpus aff. fluvialis stem bark using a human epidermoid (KB) tumour cell line as a monitor afforded five rotenoids, one pterocarpan, one chalcone, three flavanones, one flavone and one triterpenoid. All of the compounds isolated proved to be of previously known structure. Among them, the rotenoids (-)-sumatrol and (+/-)-villosinol, the dibenzoylmethane derivative (+)-3,4-methylenedioxy-2'-methoxy-[2",3":4',3']-furanodibenzoylmethane, and the flavanones (-)-isoglabrachromene and (-)-candidone have been shown to exhibit significant cytotoxic activity against human cancer cells for the first time. This is the first report of the chemical constituents of this species, and the profile of compounds obtained was in accordance with the established chemosystematic patterns of species in the tribe Tephrosieae (Leguminosae, Papilionoideae).

Characterization of the carbohydrate chains of the secreted form of the human epidermal growth factor receptor.

The human epidermal growth factor receptor (EGFR) is a transmembrane glycoprotein having 11 potential N-glycosylation sites in its extracellular domain. N-Glycosylation is needed for proper membrane insertion, EGF binding and receptor functioning. The human epidermoid carcinoma A431 cell line secretes a soluble 105 kDa glycoprotein (sEGFR) that represents the extracellular domain of the membrane-bound form, and its glycosylation pattern has been investigated. After liberation of the oligosaccharides from sEGFR with PNGase F, the glycans were fractionated along different routes, including Concanavalin A affinity chromatography, anion-exchange chromatography, HPLC and high-pH anion-exchange chromatography. The oligosaccharide fractions were characterized by 500- and 600-MHz 1H-NMR spectroscopy and mass spectrometry (FAB, ESI, and MALDI-TOF). The oligomannose-type glycans range from Man5GlcNAc2 to Man8GlcNAc2 and account for 17% of the total carbohydrate moiety. Furthermore, di-, tri'- and tetraantennary complex-type structures are present, both neutral and (alpha2-3)-sialylated (up to tetrasialo), comprising 24 and 59%, respectively, of the total carbohydrate moiety. In this study, 32 new complex-type glycans are characterized containing the Le(x), Le(Y), and sialyl-Le(x) determinants, the bloodgroup A and H antigens, as well as the ALe(Y) determinant. This first comprehensive glycosylation study on a human nonrecombinant receptor shows the immense heterogeneity of the glycosylation of sEGFR.

Invasion of endothelial and epithelial cells by strains of Porphyromonas gingivalis

Porphyromonas gingivalis is a periodontal pathogen that may also be involved in the pathogenesis of coronary heart disease. This microorganism has the ability to invade several cell lines. In this study, 26 different strains of P. gingivalis were tested for invasion of human umbilical vein endothelial cells and KB cells, a human oral epidermoid cell line. Abilities to invade both cell lines by an individual strain were similar, and their invasion efficiencies could be assembled into four groups: high, moderate, low and non-invasive. Of the 26 strains, only P. gingivalis AJW4 was non-invasive. Since the fimbriae are implicated as having a key role in invasion by this species, the presence of fimbriae on strain AJW4 was investigated. Using polymerase chain reaction (PCR), strain AJW4 was found to contain the fimA gene. Sequence analysis revealed it to be type IV according to the typing scheme developed by Amano et al. Further, fimA is transcribed in this strain as demonstrated by reverse transcription PCR and is expressed on the cell surface as visualized by negative staining and electron microscopy. The adherence+invasion of strain AJW4 was 38.7% of the most invasive strain (strain 381). However, the CFU ml −1 of strain AJW4 recovered from within cells was 2.9% of strain 381. Even though strains AJW4 and W50 have the same type IV fimbriae, strain AJW4 is 8.9-fold more adhesive yet is internalized 170-fold less. These data indicate that the invasion efficiency of P. gingivalis is variable among the different strains, and that the expression of FimA is not sufficient for invasion.

Invasion of endothelial and epithelial cells by strains of Porphyromonas gingivalis.

Porphyromonas gingivalis is a periodontal pathogen that may also be involved in the pathogenesis of coronary heart disease. This microorganism has the ability to invade several cell lines. In this study, 26 different strains of P. gingivalis were tested for invasion of human umbilical vein endothelial cells and KB cells, a human oral epidermoid cell line. Abilities to invade both cell lines by an individual strain were similar, and their invasion efficiencies could be assembled into four groups: high, moderate, low and non-invasive. Of the 26 strains, only P. gingivalis AJW4 was non-invasive. Since the fimbriae are implicated as having a key role in invasion by this species, the presence of fimbriae on strain AJW4 was investigated. Using polymerase chain reaction (PCR), strain AJW4 was found to contain the fimA gene. Sequence analysis revealed it to be type IV according to the typing scheme developed by Amano et al. Further, fimA is transcribed in this strain as demonstrated by reverse transcription PCR and is expressed on the cell surface as visualized by negative staining and electron microscopy. The adherence+invasion of strain AJW4 was 38.7% of the most invasive strain (strain 381). However, the CFU ml(-1) of strain AJW4 recovered from within cells was 2.9% of strain 381. Even though strains AJW4 and W50 have the same type IV fimbriae, strain AJW4 is 8.9-fold more adhesive yet is internalized 170-fold less. These data indicate that the invasion efficiency of P. gingivalis is variable among the different strains, and that the expression of FimA is not sufficient for invasion.