Growth Of KB Cells Research Articles

Rigid Analogues of Antimitotic Indolobenzazepinones: New Insights into Tubulin Binding via Molecular Modeling.

Two rigid analogues of 5-ethylindolobenzazepinone 4, a potent cytotoxic agent and inhibitor of tubulin polymerization, were prepared. The first was the indane derivative 5, in which the ethyl group is attached to the benzo moiety. The second was the pyrrolidine analogue 6, in which the ethyl chain was bound to the lactam nitrogen. While both compounds were considerably less active inhibitors of KB cell growth as compared to 4, inhibition of tubulin polymerization was only moderately reduced. Tubulin docking studies indicated that the aR and aS atropoisomers of 5 and 6 occupy different binding pockets at the colchicine binding site. Conversely, both aS-5 and aS-6 occupy the same binding pocket as aSS-4 but do not benefit from the favorable hydrophobic interactions provided by the C5 alkyl group of 4, thus possibly explaining their lower activities.

Terbinafine inhibits oral squamous cell carcinoma growth through anti‐cancer cell proliferation and anti‐angiogenesis

Terbinafine (TB), an oral antifungal agent used in the treatment of superficial mycosis, has been reported to exert an anti-tumor effect in various cancer cells. However, the effect of TB on oral cancer has not been evaluated. Herein we demonstrate that TB (0-60 µM) concentration-dependently decreased cell number in cultured human oral squamous cell carcinoma (OSCC), KB cells. The anti-proliferation effect of TB was also observed in two other OSCC cell lines, SAS and SCC 15. TB (60 µM) was not cytotoxic and its inhibition on KB cell growth was reversible. [(3) H]thymidine incorporation and flow cytometric analyses revealed that TB-inhibited DNA synthesis and induced the G0/G1 cell-cycle arrest. The TB-induced cell-cycle arrest occurred when the cyclin-dependent kinase 2 activity was inhibited just as the protein levels of p21(cip1) and p27(kip1) were increased. The TB-induced G0/G1 cell-cycle arrest was completely blocked when the expressions of p21(cip1) and p27(kip1) were knocked-down together. Taken together, these results suggest that the p21(cip1) - and p27(kip1) -associated signaling pathways might be involved in the TB-induced anti-proliferation in KB cells. In vivo, TB (50 mg/kg, i.p.) significantly inhibited the KB tumor size. In these TB-treated tumors, increases in the levels of p21(cip1) and p27(kip1) protein and decreases in the number of proliferating cell nuclear antigen-positive cells and the microvessel density were observed. These findings demonstrate for the first time that TB might have potential to serve as a therapeutic tool in the treatment of oral cancer.

Apoptotic effect of Polygonum Cuspidatum in oral cancer cells through the regulation of specificity protein 1

The aim of this study was to evaluate the growth inhibitory and apoptosis-inducing effects and mechanisms of Polygonum cuspidatum root in oral cancer cells. The testing materials were separated by normal-phase silica gel liquid chromatography. The effect of P. cuspidatum root on apoptotsis and its mechanism were performed using 3-(4,5-dimethylthiazol-20yl)-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2H-tetrazolium) (MTS) assay, western blot analysis, RT-PCR, promoter assay, and (4'-6-Diamidino-2-phenylindole) (DAPI) staining. The methanol extract of P. cuspidatum (MEPC) inhibited the proliferation of oral cancer cells by inducing caspase-dependent apoptosis. Protein and mRNA expression levels and the transactivation of Specificity protein 1 (Sp1) were markedly decreased in KB cells treated with MEPC. Ethyl acetate fraction (EA) from MEPC was more potent than aqueous fraction (AQ) from MEPC to induce apoptosis. F2, F3, and F4 from EA differentially inhibited the growth of KB cells, and it depends on the amount of Emodin in F2, F3, and F4. Moreover, Emodin inhibited oral cancer cell growth and induced caspase-dependent apoptosis by decreasing Sp1. MEPC also decreased an apoptosis-related downstream target of Sp1 protein, survivin. The results from this study strongly suggest that MEPC, its fraction, and Emodin may be potential bioactive materials to cause apoptosis mechanism via the down-regulation of Sp1 in oral cancer cells.

Anthracenedione Derivatives as Anticancer Agents Isolated from Secondary Metabolites of the Mangrove Endophytic Fungi

In this article, we report anticancer activity of 14 anthracenedione derivatives separated from the secondary metabolites of the mangrove endophytic fungi Halorosellinia sp. (No. 1403) and Guignardia sp. (No. 4382). Some of them inhibited potently the growth of KB and KBv200 cells, among which compound 6 displayed strong cytotoxicity with IC50 values of 3.17 and 3.21 μM to KB and KBv200 cells, respectively. Furthermore, we demonstrate that the mechanism involved in the apoptosis induced by compound 6 is probably related to mitochondrial dysfunction. Additionally, the structure-activity relationships of these compounds are discussed.

Abstract 223: Apoptotic activity of Polygonum cuspidatum in KB human oral cancer cells through the downregulation of specificity protein 1

Abstract Polygonum cuspidatum (Polygonaceae) has traditionally been used in folk medicine to improve oral public health. However, there are no reports related to its potential of controlling oral cancer. In this study, we evaluated the anti-tumorigenic effects and mechanisms of methanol extract and its fractions separated from Polygonum cuspidatum root in KB human oral cancer cells. The methanol extract of Polygonum cuspidatum (MEPC) inhibited the proliferation of KB cells in a dose- and time-dependent manner by inducing caspase-dependent apoptosis. Protein and mRNA expression levels and the transactivation of Specificity protein 1 (Sp1) were markedly decreased in KB cells treated with MEPC. Ethyl acetate fraction (EA) from MEPC was more potent than aqueous fraction (AQ) from MEPC to induce apoptosis. F2, F3 and F4 from EA differentially inhibited the growth of KB cells and it depends on the amount of Emodin in F2, F3 and F4. Moreover, Emodin inhibited KB cell growth and induced caspse-dependent apoptosis. Thus, the results from this study strongly suggest that MEPC, its fraction and Emodin may be potential bioactive materials to cause apoptosis mechanism via the down-regulation of Sp1 in KB human oral cancer cells. This paper was supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD, Basic Research Promotion Fund, KRF-2008-331-E00260) and Bio R&D program through the Korea Science and Engineering Foundation funded by the Ministry of Education, Science and Technology (M10870050003-08N7005-00311). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 223.

Inhibition of L-Type Amino Acid Transporter Modulates the Expression of Cell Cycle Regulatory Factors in KB Oral Cancer Cells

The purpose of this study was to examine the effect of 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH), an inhibitor of L-type amino acid transporters, on the cell growth suppression in KB human oral cancer cells and to study the roles of cell cycle regulatory factors in the BCH-induced growth inhibition. The effect of BCH on cell growth suppression and the influence of BCH to cell cycle regulatory factors in KB cell growth inhibition were examined using cell cycle analysis, immunoblotting and immunoprecipitation. The BCH treatment induced cell cycle arrest at G1 phase in KB cells. The expression of cyclin D3 was remarkably decreased by BCH treatment. The BCH inhibited the expression of cyclin-dependent protein kinase 6 (CDK6) in a time-dependent manner. In addition, the expression of CDK inhibitor p27 was increased by BCH treatment in KB cells, but not CDK inhibitors p21 and p15. These results suggest that, in KB cells, the inhibition of LAT1 by BCH causes cell cycle arrest at G1 phase by inhibiting cyclin D3-CDK6 complex whereas increasing expression of a CDK inhibitor p27.

Control of cell motility by interaction of gangliosides, tetraspanins, and epidermal growth factor receptor in A431 versus KB epidermoid tumor cells

Growth of epidermoid carcinoma cell lines, A431 and KB, has been known to be controlled by the interaction of epidermal growth factor (EGF) and its receptor (EGFR) with tyrosine kinase. Ganglioside GM3 was previously found to interact with EGFR and to inhibit EGFR tyrosine kinase. However, motility of these cells, controlled by EGFR and ganglioside, was not studied. The present study is focused on the control mechanism of the motility of these cells through interaction of ganglioside, tetraspanin (TSP), and EGFR. Key results are as follows: (i) The level of EGFR expressed in A431 cells is ∼6 times higher than that expressed in KB cells, and motility of A431 cells is also much higher than that of KB cells, yet growth of A431 cells is either not affected or is inhibited by EGF. In contrast, growth of KB cells is enhanced by EGF. (ii) Levels of TSPs (CD9, CD82, and CD81) expressed in A431 cells are much higher than those expressed in KB cells, and TSPs expressed in A431 cells are reduced by treatment of cells with EtDO-P4, which inhibits the synthesis of glycosphingolipids (GSLs) and gangliosides. (iii) These TSPs are co-immunoprecipitated with EGFR in both A431 and KB cells, indicating that TSPs are closely associated with EGFR. (iv) High motility of A431 cells is greatly reduced, while low motility of KB cells is not affected, by treatment of cells with EtDO-P4. These results, taken together, suggest that there is a close correlation between high motility of A431 cells and high expression of EGFR and TSPs, and between ganglioside GM3/GM2 and TSP. A similar correlation was suggested between the low motility of KB cells and low levels of EGFR and TSP. The correlation between high motility and high level of EGFR with the ganglioside–TSP complex in A431 cells is unique. This is in contrast to our previous studies that indicate that motility of many types of tumor cells is inhibited by a high level of CD9 or CD82, together with growth factor receptors and integrins.

Differential effects of selective cyclooxygenase-2 inhibitors in inhibiting proliferation and induction of apoptosis in oral squamous cell carcinoma

Cyclooxygenase-2 (COX-2), an enzyme that catalyzes the synthesis of prostaglandins, is made inducible by various stimuli such as inflammation. Although COX-2 is commonly overexpressed in a variety of premalignant and malignant conditions including oral leukoplakia and squamous cell carcinoma, relatively little research has compared the effects of various COX-2 inhibitors (celecoxib, NS-398, nimesulide and meloxicam). Therefore, we investigated the effects of four different selective COX-2 inhibitors on the growth of KB cells, derived from oral squamous cell carcinoma (OSCC) and its mechanisms. Celecoxib and NS-398 strongly suppressed the proliferation of KB cells at 10-100 microM, whereas nimesulide and meloxicam are less potent proliferation inhibitors. Only celecoxib induced apoptosis of the KB cells, as detected on the basis of DNA fragmentation, caspase-3/7 activation and cleaved poly(ADP-ribose) polymerase (PARP) fragmentation. All four COX-2 inhibitors increased COX-2 protein expression but suppressed prostaglandin (PG) E2 production in the KB cells, suggesting that the pro-apoptotic effect of celecoxib was unrelated to the inhibition of COX-2. Mechanistically, a high level of p53 protein and a low level of multidrug-resistant protein 1 (MRP1) and breast cancer resistant protein (BCRP) mRNA in KB cells with celecoxib may explain the differential effect of these selective COX-2 inhibitors in KB cells. Taken together, celecoxib is a good therapeutic candidate for treating OSCC through the suppression of cell proliferation and the induction of apoptosis in a COX-2 independent manner.

Serial recombinant expression and activity against tumor cells in vitro of antibacterial peptide Alloferon-1

To construct a prokaryotic expression system to serially express Alloferon-1 and to determine the anti-tumor activity of its products in vitro. An artificial fusion gene containing 6 x His-EK-8 x Alloferon-1-EK-6 x His sequences was constructed by linking primer PCR. By using routine molecular biological methods, the artificial fusion gene was cloned and its prokaryotic expression system was then constructed. SDS-PAGE and BioRad Agarose Image Analysor was applied to measure the expression and output of the target recombinant products 8 x rAlloferon-1-EK. Ni-NTA affinity chromatography and EK digestion and Sephadex G-50 chromatography were performed to extract 8 x rAlloferon-1-EK and rAlloferon-1-EK, respectively. The proliferation of KB, SGC and HL-60 tumor cells was tested by using MTT method after treatment with directly synthesized Alloferon-1 (sAlloferon-1), Aloferon-1-EK (sAlloferon-1-EK) and rAlloferon-1-EK. The target artificial fusion gene and its prokaryotic expression system pET42a-8 x rAlloferon-1-EK-E. coliBLDE3 with the expected sequences were obtained. Under inducement of IPTG, the prokaryotic expression system expressed the target serial recombinant protein 8 x rAlloferon-1-EK and its output was approximate 30 % of the total bacterial proteins. 8 x rAlloferon-1-EK and rAlloferon-1-EK were obtained through Ni-NTA and Sephadex G-50 columns. sAlloferon-1, sAlloferon-1-EK and rAlloferon-1ìrAlloferon-EK showed similar remarkable effects of inhibiting the growth and proliferation of KB, SGC and HL-60 cells in vitro within 25 approximately 100 microg/ml concentration range (P<0.01), and there were no significant differences in the inhibiting effects among the three agents (P>0.05). A prokaryotic expression system to serially express rAlloferon-1 has been successfully constructed. The product rAlloferon-1-EK has a similar anti-tumor activity compared to both the synthesized Alloferon-1 and Alloferon-1-EK in vitro.

Aurora kinase small molecule inhibitor destroys mitotic spindle, suppresses cell growth, and induces apoptosis in oral squamous cancer cells

Mitotic Aurora kinases are required for accurate chromosome segregation during cell division. Ectopic expression of Aurora-A (Aur-A) kinase results in centrosome amplification, aberrant spindles, and consequent aneuploidy. In the present study, we showed that Aurora kinase inhibitory small molecule VX-680 inhibited histone H3 phosphorylation at Ser10, a known in vivo substrate residue of Aurora kinase, in oral squamous cell carcinoma (OSCC) KB cells. In addition, monopolar spindle structures, typical abnormalities induced by inhibition of Aur-A, were generated in VX-680-treated cells. Inhibition of Aurora kinase led to reduced KB cell growth, as assessed by MTT assay. Western blot analysis revealed that VX-680 caused cleavage of two critical apoptotic associated proteins, PARP and caspase-3. In contrast, expression of cell survival factor Bcl-2 was reduced by VX-680 treatment in a dose-dependent manner. Subsequently, nuclear characteristic of DNA fragmentation, indicative of apoptotic cell death, was clearly observed in these OSCC cells with Aurora kinase inhibitory VX-680. Taken together, we showed that Aurora kinase inhibitory VX-680 led to apoptotic cell death in OSCC cells, suggesting a novel therapeutic target in oral cancer.

Non-viral delivery of the connexin 43 gene with histone deacetylase inhibitor to human nasopharyngeal tumor cells enhances gene expression and inhibits in vivo tumor growth

Dysregulation of connexin expression is believed to have a role in carcinogenesis, because levels of connexin are reduced in various tumors. We examined the role of connexin 43 (Cx43) alone and combined with a histone deactylase (HDAC) inhibitor in tumor growth inhibition. The transfection of Cx43 plasmid DNA (pCMV-Cx43) into human nasopharyngeal cancer KB cells using folate-linked nanoparticles induced inhibition of cell growth. Cx43 induced a tumor suppressive effect via a gap junctional intercellular communication-independent mechanism. The transfection of pCMV- Cx43 along with an HDAC inhibitor, 4-phenylbutyrate (4-PB), enhanced Cx43 expression greatly in vitro, and inhibited significantly the tumor growth of KB cells and xenografts compared with that of pCMV-Cx43 alone. 4-PB induced increased expression of genes of DNA damage checkpoints and of apoptosis via the down-regulation of anti-apoptotic bcl-2 mRNA expression and up-regulation of the activity of the apoptosis-associated enzyme caspase-3/7. Thus, the amplified Cx43 expression by an antitumor agent, an HDAC inhibitor, may have great potential as a growth inhibitor for nasopharyngeal tumors.

들깨잎과 쑥 추출물의 구강병 원인균에 대한 항균 및 KB 세포 증식 억제효과

Methanol extracts of Perilla and Mugwort were stepwise extracted with hexane, chloroform, ethyl acetate, butanol and water. Anti-microbial activities and inhibitory effect on growth of oral tumor cell of each extract were investigated. Each extracts of Perilla and Mugwort were investigated to anti-microbial effects on oral microbes by means of agar diffusion method and MIC. These results suggest that the hexane extracts of Perilla and Mugwort have antimicrobial activities against S. mutans and potent inhibitory Effect to KB cell growth.

작약 추출물의 구강병원균에 대한 항균성 및 구강암 세포 증식 억제효과

Paeonia lactiflora was stepwise extracted with hexane, chloroform, ethyl acetate, butanol and water. Anti-microbial activity of each extract was investigated. Methanol extract of P. lactiflora revealed anti-microbial activity against S. mutans, C. albicans, and S. aureus. Also, hexane fraction revealed anti-bacterial activity against S. mutans and ethyl acetate fraction acted as potent anti-microbial agent on C. albicans and S. aureus. The relative growth ratio (RGR) of hexane fraction of P. lactiflora against S. mutans were determined as 77.8% in concentration of 0.125 ㎎/ml, 98.46% in 0.25 ㎎/ml and 100% in 0.5 ㎎/ml. The ethyl acetate fraction of P. lactiflora revealed RGR against C. albicans as 52.5% in concentration of 0.125 ㎎/ml, 60.83% in 0.25 ㎎/ml and 78.33% in 0.5 ㎎/ml. It indicate that increasing concentration increase RGR. The measured minimal inhibitory concentration (MIC) of hexane fraction on S. mutans KCTC 5316 strain was 0.5 ㎎/ml and MIC of ethyl acetate fraction on C. albicans KCTC 7270 was 2.0 ㎎/ml. The experiment of inhibition to growth of KB cell (oral squamous cell carcinoma) result 61.9% in butanol, 76.7% in hexane extract of P. lactiflora. The hexane extract exhibit potent inhibition effect to the growth of KB cell. These results suggest that the hexane extract of Paeonia lactiflora has antimicrobial activity against S. mutans and has preventive effect to dental caries in addition to potent inhibition to KB cell growth.

Ganglioside GM3 Derivatives with Truncated Ceramide Moiety: Facial Synthesis and Inhibitory Activity against KB Cell Growth

An expeditious sialylation reaction with phenylthioglycoside 4 as a sialyl donor and MeSOTf as a promoter was developed. These conditions are very useful for synthesizing ganglioside GM3 (1), its C8‐ceramide analog 2, and 3‐deoxy analog 3 of 2 in an efficient manner. The GM3 analog 2, whose hydrophilicity is increased by shortening the ceramide moiety, exhibits increased growth inhibiton of KB cells. The 3‐hydoxy group of ceramide does not influence its activity against KB cells.

Lentivirus-mediated gene therapy by suppressing survivin in BALB/c nude mice bearing oral squamous cell carcinoma

Despite advances in surgery, radiotherapy, and chemotherapy, the long-term survival rates with oral squamous cell carcinoma (OSCC) have not significantly improved. Gene therapy for OSCC is currently under investigation in clinical trials. Lentivirus vector is considered to be a promising gene delivery tool, but their value in cancer gene therapy has not been studied thoroughly. Survivin is overexpressed in OSCC, making it a promising target for gene therapy. This study was conducted to determine whether lentivirus-mediated gene therapy by suppressing survivin can be exploited in the treatment of OSCC. A lentivirus vector encoding short hairpin RNA (shRNA) targeting survivin was constructed and transfected into KB cells in vitro. The results showed that survivin was persistently and markedly reduced by lentivirus-mediated RNA interference (RNAi); the growth of KB cells was decreased by 34.2% on day 5; the apoptosis rate induced by vincristine (VCR) was increased by 29.8% and caspase-3 activity was also significantly increased; the IC50 value of adriamycin (ADM) were 0.09 µg/ml, which indicated that survivin-knockout KB cells were 2.1 times more susceptible to ADM than the control; the clonogenic survival rate at 6 Gy of X ray was 3.7%, less than 15.3% of the control. In the xenograft model, the development of tumors as well as the growth of established tumors was inhibited by transfection of lentivirus. Our study indicates that lentivirus-mediated gene therapy is an attractive strategy in the treatment of OSCC and justifies the use of lentivirus in cancer gene therapy studies.

Prolonged exposure to arecoline arrested human KB epithelial cell growth: Regulatory mechanisms of cell cycle and apoptosis

Arecoline, the main areca alkaloid in betel quid (BQ), is reported to have cytotoxic, genotoxic, and mutagenic effects in various cells. It shows strong correlation to the incidence of oral submucous fibrosis, leukoplakia, and oral cancer. To clarify the role of arecoline in BQ-induced carcinogenesis, primary human gingival keratinocyes (GK) and human KB epithelial cells were used for studying the molecular mechanisms of arecoline-mediated cell cycle deregulation for comparison. After 24 h of exposure, arecoline (0.2–0.8 mM) inhibited KB cell growth in a dose- and time-dependent manner with a reduction in cell number by 27–37 and 37–58%, respectively, as determined by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) and sulforhodamine B (SRB) assays. Incubation of KB cells with arecoline (0.1–0.4 mM) caused late-S and G2/M phases’ cell cycle arrest. Western blot analysis revealed that arecoline induced cyclin Bl, Wee 1, and phosphorylated cdc2 protein levels whereas it declined p21 protein expression in KB cancer cells. Nevertheless, arecoline induced p21, but decreased cdc2 and cyclin B1 protein levels in GK. We demonstrated that higher concentrations of arecoline (0.2–1.2 mM) induced both cell necrosis and apoptosis as detected by DNA fragmentation and Annexin V–PI staining after long-term (48 h) treatment. Our results suggest that differential regulation of S and/or G2/M cell cycle-related proteins in the GK and KB cells play a crucial role in different stages of BQ-mediated carcinogenesis.

Minimal contribution of desmethyl-gefitinib, the major human plasma metabolite of gefitinib, to epidermal growth factor receptor (EGFR)-mediated tumour growth inhibition

Desmethyl-gefitinib is a major metabolite of gefitinib observed in human plasma at concentrations similar to those of gefitinib. The epidermal growth factor receptor (EGFR)-related inhibitory effects of gefitinib and desmethyl-gefitinib have been compared both in vitro, using enzyme kinase assays and tumour cell growth inhibition, and in vivo by assessment of tumour xenografts growth inhibition in the mouse. Both gefitinib (IC50 = 0.022 µM) and its desmethyl metabolite (0.036 µM) inhibited subcellular EGFR tyrosine kinase activity with a similar potency and selectivity. However, desmethyl-gefitinib (IC50 = 0.76 µM) was 15 times less active than gefitinib (0.049 µM) against EGF-stimulated KB cell growth in a whole cell assay. Following a preliminary pharmacokinetic study to compare apparent oral bioavailability, gefitinib (75 mg kg−1) and desmethyl-gefitinib (150 mg kg−1) were administered orally for 15 days to female nude mice bearing LoVo tumour xenografts. Tumour concentrations of gefitinib (AUC = 300 µg h g−1) were much higher than those of desmethyl-gefitinib (44.3 µg h g−1), although plasma concentrations of gefitinib (48.4 µg h ml−1) and desmethyl-gefitinib (39.0 µg h ml−1) were quite similar at these dose levels. Gefitinib produced significant tumour growth inhibition throughout the course of the study ultimately resulting in a 50% decrease (compared with controls) by day 15. In contrast, although present at comparable plasma levels, desmethyl-gefitinib had little effect on tumour growth and is, therefore, considered unlikely to contribute significantly to the therapeutic activity of gefitinib in the clinical situation.

The ribonucleotide reductase subunit M2B subcellular localization and functional importance for DNA replication in physiological growth of KB cells

Ribonucleoside diphosphate reductase (EC 1.17.4.1) (RR) is a potential target for antineoplastic agents due to its crucial role in DNA replication and repair. The expression and activity of RR subunits are highly regulated to maintain an optimal dNTP pool, which is required to maintain genetic fidelity. The human RR small subunit M2B (p53R2) is thought to contribute to DNA repair in response to DNA damage. However, it is not clear whether M2B is involved in providing dNTPs for DNA replication under physiological growth conditions. Serum starvation synchronized studies showed that a rapid increase of M2B was associated with cyclin E, which is responsible for regulation of G 1/S-phase transition. A living cell sorting study that used KB cells in normal growth, further confirmed that M2B increased to maximum levels at the G 1/S-phase transition, and decreased with DNA synthesis. Confocal studies revealed that M2B redistributed from the cytoplasm to the nucleus earlier than hRRM2 in response to DNA replication. Nuclear accumulation of M2B is associated with dynamic changes in dNTP at early periods of serum addition. By using M2B-shRNA expression vectors, inhibition of M2B may result in growth retardation in KB cells. We conclude that M2B may translocate from the cytoplasm into the nucleus and allow dNTPs to initiate DNA synthesis in KB cells under physiological conditions. Thus, our findings suggested that M2B might play an important role for initiating DNA replication of KB cells in normal growth.

Reovirus oncolysis in human head and neck squamous carcinoma cells

Objective: To determine whether reovirus, a double-standed RNA virus is effective on the growth of a human head and neck squamous cell carcinoma cell line. Designs: In vitro cell proliferation assay, KB cells, a human oral floor squamous cell carcinoma cell line, were treated with reovirus and the number of cells was quantitated by an assay, using trypan blue staining. In vivo tumor growth assay, KB cells were injected subcutaneously into athymic nude mice, which were given an intratumoral injection of reovirus to a maximum four times in every week. The tumor size was measured once a week. Simultaneously, apoptosis and necrosis of KB cells were investigated, using technique of immunohistochemistry. Results: In vitro, the multiplication of the KB cell was inhibited depending on the concentration of reovirus. In vivo, athymic nude mice bearing KB tumors were injected with the virus intratumorally, and the tumor growth was suppressed proportionally depending on the injection time of reovirus. Necrosis was recognized extensively in the pathological specimen. On the other hand, apoptosis-inducing effect was not obvious in these specimen. Conclusions: Reovirus suppressed tumor growth of KB cells in vivo as well as in vitro. The possibility that reovirus could become the means of treatment for head and neck carcinoma, was suggested with further work.

Reovirus oncolysis in human head and neck squamous carcinoma cells

Objective: To determine whether reovirus, a double-standed RNA virus is effective on the growth of a human head and neck squamous cell carcinoma cell line. Designs: In vitro cell proliferation assay, KB cells, a human oral floor squamous cell carcinoma cell line, were treated with reovirus and the number of cells was quantitated by an assay, using trypan blue staining. In vivo tumor growth assay, KB cells were injected subcutaneously into athymic nude mice, which were given an intratumoral injection of reovirus to a maximum four times in every week. The tumor size was measured once a week. Simultaneously, apoptosis and necrosis of KB cells were investigated, using technique of immunohistochemistry. Results: In vitro, the multiplication of the KB cell was inhibited depending on the concentration of reovirus. In vivo, athymic nude mice bearing KB tumors were injected with the virus intratumorally, and the tumor growth was suppressed proportionally depending on the injection time of reovirus. Necrosis was recognized extensively in the pathological specimen. On the other hand, apoptosis-inducing effect was not obvious in these specimen. Conclusions: Reovirus suppressed tumor growth of KB cells in vivo as well as in vitro. The possibility that reovirus could become the means of treatment for head and neck carcinoma, was suggested with further work.