Cultured KB Cells Research Articles

Synthesis and Evaluation of Folate-Conjugated Phenanthraquinones for Tumor-Targeted Oxidative Chemotherapy.

Almost all cells are easily killed by exposure to potent oxidants. Indeed, major pathogen defense mechanisms in both animal and plant kingdoms involve production of an oxidative burst, where host defense cells show an invading pathogen with reactive oxygen species (ROS). Although cancer cells can be similarly killed by ROS, development of oxidant-producing chemotherapies has been limited by their inherent nonspecificity and potential toxicity to healthy cells. In this paper, we describe the targeting of an ROS-generating molecule selectively to tumor cells using folate as the tumor-targeting ligand. For this purpose, we exploit the ability of 9,10-phenanthraquinone (PHQ) to enhance the continuous generation of H2O2 in the presence of ascorbic acid to establish a constitutive source of ROS within the tumor mass. We report here that incubation of folate receptor-expressing KB cells in culture with folate-PHQ plus ascorbate results in the death of the cancer cells with an IC50 of ~10 nM (folate-PHQ). We also demonstrate that a cleavable spacer linking folate to PHQ is significantly inferior to a noncleavable spacer, in contrast to most other folate-targeted therapeutic agents. Unfortunately, no evidence for folate-PHQ mediated tumor regression in murine tumor models is obtained, suggesting that unanticipated impediments to generation of cytotoxic quantities of ROS in vivo are encountered. Possible mechanisms and potential solutions to these unanticipated results are offered.

Abstract 5492: Study the variation of the glutamate moiety of AG94, a targeted, potent GARFTase inhibitor, as antitumor agents with the 2-amino-6-substituted pyrrolo[2,3-d]pyrimidine scaffold.

Abstract We have been extensively involved in the elaboration of substituted pyrrolo[2,3-d]pyrimidines to obtain potential targeted agents without reduced folate carrier (RFC) activity. Lack of selectivity for RFC is a major cause of significant toxicity in the clinic associated with antifolate anticancer agents. These efforts have led to the discovery of several series of potent targeted agents, which showed specificity for folate receptors (FRs) and/or the proton coupled folate transporter (PCFT). These transport systems are two targets for selective cancer chemotherapy. One such targeted agent, AG94, was reported by us as the most efficacious targeted antifolate antitumor agent with PCFT and FR selectivity over RFC. AG94 is a GARFTase inhibitor and its targeted transport and inhibition of GARFTase was demonstrated to be responsible for its selective in vitro and in vivo antitumor activity. We were interested in carrying out a structure-activity relationship study (SAR) with AG94 as the lead compound. For this study we elected the glutamate moiety of AG94 for modification to determine the effect of this variation on transport as well as cell inhibition in culture. The glutamate moiety of AG94 was replaced with various natural and unnatural amino acids or completely deleted in an attempt to vary the chain length between the two carboxylic groups and retain one or none of the carboxylic moieties in the target compounds. The results showed that AG190 was relatively potent with an IC50 of 9.0 nM in human tumor KB cells in culture. A complete set of cell proliferation assays in CHO sublines afforded a SAR study of the transporters with defined transport as well as for GARFTase inhibitory activity. With FRα expressing RT16 CHO cells, an order of decreasing sensitivities (AG94>AG189∼AG190>AG213>AG214>AG187) was obtained. For FRβ expressing D4 CHO cells, it showed that AG94>AG190>>AG189, whereas AG187, AG213 and AG214 are inactive. All target compounds are inactive in PCFT expressing R2/PCFT4 cells. In the binding assays towards PCFT and FRα with AG189 and AG190, we found that AG190 and AG189 still bound to PCFT although somewhat less avidly than that for AG94 towards PCFT, and AG189 along with AG190 exhibited very similar binding affinity towards FRα compared to AG94. In nucleoside protection assay, surprisingly neither adenosine nor AICA protect and suggested a change in intracellular target for AG189 and AG190 compared to AG94. Based on the profile of protection, we postulate that both AG189 and AG190 retain their targeted mechanism for transport but may not act as GARFTase inhibitors, a role previously established for AG94. Further study to elucitdate their exact role is currently underway. The ability to manipulate the intracellular target by variation in the glutamate moiety is novel and remarkable for this series. Citation Format: Aleem Gangjee, Sai Zhao, Lalit Kumar, Christina Cherian, Steven Orr, Jenny Huang, Zhanjun Hou, Larry H. Matherly. Study the variation of the glutamate moiety of AG94, a targeted, potent GARFTase inhibitor, as antitumor agents with the 2-amino-6-substituted pyrrolo[2,3-d]pyrimidine scaffold. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5492. doi:10.1158/1538-7445.AM2013-5492

Synthesis and Application of a Full Water‐Soluble and Red‐Emitting Chemosensor Based on Phenoxazinium for Copper(II) Ions

AbstractA phenoxazinium‐based chemosensor (1) bearing di(2‐picolyl)amine unit was successfully synthesized. The result shows that it is a red‐emitting and full water‐soluble chemosensor for the selective detection of Cu2+ in pure water. The fluorescence on‐off mechanism was studied by ab initio calculations. To confirm the suitability of 1 for biological applications, it was employed in the fluorescence detection of the intracellular Cu2+ with cultured KB cells. The results indicated that 1 had good membrane permeability and could be useful for the fluorescence microscopic imaging.

Immunofluorescence examination of CK-13 expression in cell line KB differentiated by all-trans retinoic acid or As2 O3

To examine the expression of cytokeratin-13 (CK-13) in oral squamous cell carcinoma (OSCC) and to discuss the effects of all-trans retinoic acid (ATRA) or arsenic trioxide (As2 O3) on the differentiation of human oral undifferentiated squamous cell carcinoma cell line KB cells. The cultured KB cells were divided into three groups, ATRA group, As2 O3 group, and control. The expression of CK-13 in KB cells was detected using the immunofluorescence before and after KB cells were induced by ATRA or As2 O3. The expression rates of CK-13 in KB cells in the ATRA group and As2 O3 group were significantly higher than that in the control (P < 0.05), but there was no significant difference in the expression between ATRA and As2 O3 group(P > 0.05). ATRA and As2 O3 both have the ability to differentiate the KB cells, and the expression is associated with the degree of tumor differentiation. CK-13 may serve as a molecular marker to evaluate the effect of the differentiation treatment on OSCC.

Evaluation of plants used for antimalarial treatment by the Maasai of Kenya

Semi-structured interviews with three Maasai herbalists led to the identification and collection of 21 species of plants used to treat malaria. Extracts were evaluated using in vitro antimalarial and cytotoxicity assays. Of the species tested, over half were antiplasmodial (IC 50 < 10 μg/ml), and all but one ( Gutenbergia cordifolia Benth.) displayed selectivity for the malaria parasite Plasmodium falciparum as indicated by a lack of cytotoxicity (ED 50 > 20 μg/ml) against cultured KB cells. The results of this preliminary investigation support the traditional knowledge of Maasai herbalists and justify ethnomedical inquiry as a promising method, specifically, in antimalarial therapy, to yield leads for drug discovery.

Anti-Staphylococcal and Cytotoxic Compounds fromHyptis pectinata

Bioassay-guided fractionation of a CHCl (3) extract prepared from the Mexican medicinal plant Hyptis pectinata led to the isolation of four pyrones, pectinolides A-C ( 1-3) and H ( 4). Activity was tracked using cultured KB cells. Multidrug-resistant strains of Staphylococcus aureus were sensitive to pectinolide H ( 4; KB > 20 microg/mL) in the concentration range of 32-64 microg/mL. The absolute stereochemistry of this new compound was established as 5 S-[(4 S-acetyloxy)-(1 S-hydroxy)-2 Z-octenyl]-2(5 H)-furanone on the basis of spectral, chiroptical data and chemical correlation with pectinolide A ( 1). Mosher ester derivatives were used with pectinolide B ( 2) for confirmation of the 3'-( S) absolute stereochemistry on the side chain chiral center of pectinolides A-C.

Synthesis of A/B Ring Analogs of Territrem B and Evaluation of Their Biological Activities

AbstractTwo series of territrem B analogs, i.e., 5–10, containing both the 2‐en‐1‐one‐A‐ring and the aromatic‐E‐ring pharmacophores were designed and synthesized from jujubogenin (4a). The anti‐acetylcholinesterase (anti‐AChE), anti‐caspase‐3, and other biological activities of these territrem‐B analogs and their intermediates were assessed. Compound 9b, 22a, and 24f were shown to be weak inhibitors of AChE. None of the synthesized compounds exhibited significant inhibitory activity on caspase‐3. On the other hand, compounds 22e, 24a, 7b, and 8a showed mild cytotoxicity on cultured KB cells, with IC50 values of 2.0, 3.5, 6.5, and 14 μM, respectively. In addition, compounds 23b and 5f were active against injury arising from oxygen‐glucose deprivation.

Inhibition of metastasis of tumor cells overexpressing thymidine phosphorylase by 2-deoxy-L-ribose.

Thymidine phosphorylase (TP) catalyzes the reversible conversion of thymidine to thymine, thereby generating 2-deoxy-D-ribose-1-phosphate, which upon dephosphorylation forms 2-deoxy-D-ribose (D-dRib), a degradation product of thymidine. We have previously shown that D-dRib promotes angiogenesis and chemotaxis of endothelial cells and also confers resistance to hypoxia-induced apoptosis in some cancer cell lines. 2-Deoxy-L-ribose (L-dRib), a stereoisomer of D-dRib, can inhibit D-dRib anti-apoptotic effects and suppressed the growth of KB cells overexpressing TP (KB/TP cells) transplanted into nude mice. In this study, we examined the ability of L-dRib to suppress metastasis of KB/TP cells using two different models of metastasis. The antimetastatic effect of L-dRib was first investigated in a liver-metastasis model in nude mice inoculated with KB/TP cells. Oral administration of L-dRib for 28 days at a dose of 20 mg/kg/day significantly reduced the number of metastatic nodules in the liver and suppressed angiogenesis and enhanced apoptosis in KB/TP metastatic nodules. Next, we compared the ability of L-dRib and tegafur alone or in combination to decrease the number of metastatic nodules in organs in the abdominal cavity in nude mice receiving s.c. of KB/TP cells into their backs. L-dRib (20 mg/kg/day) was significantly (P < 0.05) more efficient than tegafur (100 mg/kg/day) in decreasing the number of metastatic nodules in organs in the abdominal cavity. By in vitro invasion assay, L-dRib also reduced the number of invading KB/TP cells. L-dRib anti-invasive activity may be mediated by its ability to suppress the enhancing effect of TP and D-dRib on both mRNA and protein expression of vascular endothelial growth factor and interleukin-8 in cultured KB cells. These findings suggest that L-dRib may be useful in a clinical setting for the suppression of metastasis of tumor cells expressing TP.

Folate receptor-mediated liposomal delivery of a lipophilic boron agent to tumor cells in vitro for neutron capture therapy.

This study was aimed at the in vitro evaluations of folate receptor (FR)-targeted liposomes as carriers for a lipophilic boron agent, K[nido-7-CH3(CH2)15-7,8-C2B9H11, in FR-overexpressing tumor cells for neutron capture therapy. Large unilamellar vesicles (-200 nm in diameter) were prepared with the composition of egg PC/chol/K[nido-7-CH3(CH2)15-7,8-C2B9H11] (2:2:1, mol/mol), with an additional 0.5 mol % of folate-PEG-DSPE or PEG-DSPE added for the FR-targeted or nontargeted liposomal formulations, respectively. Boron-containing, FR-targeted liposomes readily bound to KB cells, an FR-overexpressing cell line, and were internalized via FR-mediated endocytosis. The boron uptake in cells treated with these liposomes was approximately 10 times greater compared with those treated with control liposomes. In contrast, FR-targeted and nontargeted liposomes showed no difference in boron delivery efficiency in F98 cells, which do not express the FR. The subcellular distribution of the boron compound in KB cells treated with the FR-targeted liposomes was investigated by cellular fractionation experiments, which showed that most of the boron compound was found in either the cytosol/endosomal or cell membrane fractions, indicating efficient internalization of the liposomal boron. FR-targeted liposomes incorporating the lipophilic boron agent, K[nido-7-CH3(CH2)15-7,8-C2B9H11], into its bilayer were capable of specific receptor binding and receptor-mediated endocytosis in cultured KB cells. Such liposomes warrant further investigations for use in neutron capture therapy.

Involvement of staphylococcal protein A and cytoskeletal actin in Staphylococcus aureus invasion of cultured human oral epithelial cells

Following the coincidental discovery that beta-actin isolated from renal epithelial cells was precipitated by staphylococcal protein A (SPA), the possibility that SPA and cytoskeletal actin filaments may be involved in Staphylococcus aureus infection of epithelial cells was considered. Therefore, to clarify the potential role of SPA and actin filaments in S. aureus infection, the invasion efficiency of S. aureus was determined quantitatively by measuring the number of cfu of viable organisms recovered from cultured KB cells. S. aureus invasion was found to be time dependent (0-60 min) and increased linearly when increasing numbers of bacteria were added (10(4)-10(6) cfu/ml). However, significant variation in the level of invasion was noted in protein A-deficient S. aureus Wood 46. Cytochalasin B inhibited the invasion efficiency of S. aureus in a dose-dependent manner. The present study suggests that interaction of staphylococcal protein A and cytoskeletal actin filaments is involved in the S. aureus invasion of cultured KB cells, and this process may contribute, in part, to the intracellular movement, cell-to-cell spread and dissemination of S. aureus within human oral epithelial cells in vivo.

Delivery of N-(Phosphonacetyl)-L-aspartic acid encapsulated in thermosensitive sterically stabilized liposomes into cultured KB cells via folate receptor

Delivery of N-(Phosphonacetyl)-L-aspartic acid encapsulated in thermosensitive sterically stabilized liposomes into cultured KB cells via folate receptor

Cytotoxic Activity of Some Indole Derivatives and Indole Metabolites of Streptomyces staurosporeus

The cytotoxic potential and structure activity relationships of several indole metabolites obtained from feeding experiments using Streptomyces staurosporeus, a staurosporine producer, are described. 6-Fluoro-tryptamine and N b -acetyl-tryptamine-5- O -a-L-rhamnopyranoside, a metabolite obtained from the feeding experiment, demonstrated greatest activity with KB cells in culture, by means of an unknown mechanism.

Reversal of multidrug resistance by the staurosporine derivatives CGP 41251 and CGP 42700.

It has been shown previously that the staurosporine derivative CGP 41251, a specific inhibitor of protein kinase C (IC50 = 50 nM), exhibits antitumor activity and reverses mdr1 mediated multidrug resistance. At present, the compound is evaluated as an anticancer drug in clinical phase I trials. We compared the effects of CGP 41251 with CGP 42700, another staurosporine derivative, which exhibits low protein kinase C inhibiting activity (IC50 = > 100 microM). We found that in contrast to CGP 41251, CGP 42700 does not show antiproliferative activity in HeLa and KB cells in tissue culture (up to a concentration of 10 microM). We compared both compounds for their ability to reverse mdr1-mediated resistance in KB-C1 and in HeLa-MDR1 cells (transfected with the mdr1 gene). CGP 42700 is able to reverse mdr1-mediated resistance to a similar extent as CGP 41251. The intracellular accumulation of rhodamine 123 in KB-C1 cells following pretreatment with CGP 41251 for 30 min was higher than that following treatment with CGP 42700 if determined in medium without serum. However, quantitation of rhodamine efflux in an ex vivo assay using human CD8+ cells in serum showed that CGP 42700 is more effective in inhibiting the efflux of rhodamine 123 than CGP 41251. We conclude from our results that (1) CGP 42700 is more effective in reversal of multidrug resistance in serum than CGP 41251, indicating that the compound may be useful for treatment of patients, and (2) CGP 42700 does not inhibit protein kinase C and cell proliferation and, therefore, may be less toxic and elicit less side effects in humans than other chemosensitizers.

Cytotoxic effect of pingyangmycin on cultured KB cells.

The antitumour antibiotic pingyangmycin (PYM; bleomycin A5) was isolated from many components of bleomycin (BLM) produced by Streptomyces pingyangensisn. PYM has a similar chemical structure to that of BLM but the terminal amine moiety is different. Therefore, it would be of significance to demonstrate the antitumour effect and action mechanism of PYM on cultivated tumour cells. In this study, we used the cell growth curve, plating efficiency, and DNA synthesis inhibition assay to demonstrate the cytotoxicity of PYM on cultured KB cells. In the meantime, the morphological variations of drug-treated cells were also observed. In addition, we used the DNA precipitation assay, a simple and rapid assay, for detecting DNA damage caused by PYM on cultured KB cells for potential genotoxicity. Our results indicate that the effect of PYM significantly inhibits the cell growth, colonyforming ability, and DNA synthesis of KB cells in a dose-dependent manner. Furthermore, when treated with 5 micrograms/ml of PYM for 24 h on cultured KB cells, DNA strand breaks can be induced (P < 0.05). Therefore, it is considered that the action mechanism of PYM is due to its ability to inhibit the synthesis of DNA and split the DNA chains.

Effects of modulators of multidrug resistance on the expression of the MDR1 gene on human KB cells in culture.

The effect of four modulators of multidrug resistance (MDR) on the expression of the MDR1 gene was studied in two resistant variants of the KB cell lines, KB V1 and KB A1. This was done using a semi-quantitative assay based on mRNA reverse transcription coupled with polymerase chain reaction of the cDNA obtained. An automatic DNA sequencer was used for the measurement of the fluorescent amplification products and the MDR1 signal was compared to that of the beta-actin gene of the cells. After 24 h incubation with 15 microM of the modulators, MDR1 gene expression was slightly but significantly decreased by two of them, quinine and cyclosporine A, whereas verapamil and S-9788 had very little effect on this parameter. The effect were more pronounced in the KB A1 line than in the KB V1 line. The effect of quinine was studied over a longer time period (4-48 h) and was shown to be maximum at 24 h. These results favor the existence of a direct effect of some MDR reverters, especially quinine, on the expression of the MDR1 gene and could partially explain their modulating effect of MDR.

Anti-interferon activity of adenovirus-2-encoded VAI and VAII RNAs in translation in cultured human cells

The mode of anti-interferon action of VAI and VAII RNAs of adenovirus type 2 (Ad2) was studied by transfecting interferon-α (IFN-α)-treated KB cells in culture with a plasmid construct containing the VAI or VAII RNA gene and an SV40 promoter-chloramphenicol acetyltransferase (CAT) gene construct as reporter (pSV2-CAT). The longer the treatment of KB cells with IFN-α (2000 IU/ml) lasted, the higher was the inhibition of CAT expression. A maximum of 76% inhibition was attained without pronounced cytotoxicity during 48 h of treatment. The earlier the VAI RNA gene was transfected, the higher was the enhancement of CAT expression. CAT activity increased from 113 to 157% in normal cells and 200–400% in IFN-α treated cells, as compared with the corresponding controls without VAI RNA transfection. The level of CAT mRNA was neither appreciably decreased by IFN-α treatment, nor detectably increased by VAI or VAII RNA. The effect of VA RNA thus appeared to be on translation rather than on transcription. The relative constancy of the level of CAT mRNA indicated that IFN-α inhibition of CAT expression was not due to the activation of RNase L, but due mainly to translational repression. The level of VAII RNA expressed was only 9–13% of that of VAI RNA. Nevertheless, VAII RNA gene transfection stimulated CAT activity to 112% of the control in non-IFN-α-treated cells, and 126–182% in IFN-α-inhibited cells. When IFN-α treatment was started late after VAI RNA cotransfection, CAT expression increased to 169% which was higher than the expression in cotransfected control cells without IFN-α treatment. The enhanced level of CAT activity was in remarkable contrast to the IFN-α inhibited level of 25% without VA RNA co-transfection when IFN-α was added upon seeding. The enhanced CAT activity in cells treated late with IFN-α could be ascribed to higher levels of VA RNAs.

Synthesis, purification, and tumor cell uptake of 67Ga-deferoxamine--folate, a potential radiopharmaceutical for tumor imaging.

The vitamin folic acid was covalently linked to the chelating agent deferoxamine (DF) via an amide bond using a simple carbodiimide coupling reaction. A mixture of two isomers, DF--folate(alpha) and DF--folate(gamma), was produced involving the alpha- and gamma-carboxyl group of folic acid, respectively. These two isomers were separated by anion-exchange chromatography using a NH4HCO3 gradient. Competitive binding studies revealed that only the DF-folate(gamma) is recognized by the folate receptor on KB cells, interacting with an affinity comparable to unconjugated folic acid. The DF--folate conjugates were radiolabeled with the gamma-emitting radionuclide 67Ga3+ and tested for uptake by cultured KB cells overexpressing the folate receptor. The cellular accumulation of 67Ga-DF-folate(gamma) tracer exhibited rapid uptake kinetics in cell culture with a t1/2 of approximately 3 min. The KB cell association of 67Ga-DF--folate(gamma) was competitively blocked by free folic acid, indicating that uptake of the 67Ga-DF--folate(gamma) was specifically mediated by the folate receptor. Since the folate receptor is overexpressed on the surfaces of many neoplastic cells, these results suggest that 67Ga-DF--folate(gamma) complex might be useful as a diagnostic agent for noninvasive imaging of folate receptor-positing tumors.

Delivery of antisense oligodeoxyribonucleotides against the human epidermal growth factor receptor into cultured KB cells with liposomes conjugated to folate via polyethylene glycol.

Antisense oligodeoxyribonucleotides targeted to the epidermal growth factor (EGF) receptor were encapsulated into liposomes linked to folate via a polyethylene glycol spacer (folate-PEG-liposomes) and efficiently delivered into cultured KB cells via folate receptor-mediated endocytosis. The oligonucleotides were a phosphodiester 15-mer antisense to the EGF receptor (EGFR) gene stop codon (AEGFR2), the same sequence with three phosphorothioate linkages at each terminus (AEGFR2S), a randomized 15-mer control of similar base composition to AEGFR2 (RC15), a 14-mer control derived from a symmetrized Escherichia coli lac operator (LACM), and the 5'-fluorescein-labeled homologs of several of the above. Cellular uptake of AEGFR2 encapsulated in folate-PEG-liposomes was nine times higher than AEGFR2 encapsulated in nontargeted liposomes and 16 times higher than unencapsulated AEGFR2. Treatment of KB cells with AEGFR2 in folate-PEG-liposomes resulted in growth inhibition and significant morphological changes. Curiously, AEGFR2 and AEGFR2S encapsulated in folate-PEG-liposomes exhibited virtually identical growth inhibitory effects, reducing KB cell proliferation by > 90% 48 hr after the cells were treated for 4 hr with 3 microM oligonucleotide. Free AEGFR2 caused almost no growth inhibition, whereas free AEGFR2S was only one-fifth as potent as the folate-PEG-liposome-encapsulated oligonucleotide. Growth inhibition of the oligonucleotide-treated cells was probably due to reduced EGFR expression because indirect immunofluorescence staining of the cells with a monoclonal antibody against the EGFR showed an almost quantitative reduction of the EGFR in cells treated with folate-PEG-liposome-entrapped AEGFR2. These results suggest that antisense oligonucleotide encapsulation in folate-PEG-liposomes promise efficient and tumor-specific delivery and that phosphorothioate oligonucleotides appear to offer no major advantage over native phosphodiester DNA when delivered by this route.

Delivery of liposomes into cultured KB cells via folate receptor-mediated endocytosis.

Folic acid was covalently conjugated to 66-nm liposomes via spacers of various lengths in an attempt to target the liposomes to KB cells expressing folate receptors. Spacers of short and intermediate lengths were unable to mediate association of folate-conjugated liposomes with receptor-bearing cells, however, use of a 250 A polyethyleneglycol spacer (PEG, M(r) approximately 3350) permitted avid uptake of the liposomes at approximately 2.5 x 10(5) sites/cell. The binding of folate-PEG liposomes to KB cells could be competitively inhibited by excess free folate or by antiserum against the folate receptor, demonstrating the interaction is mediated by the cell surface folate-binding protein. Following binding, cell-associated folate-PEG liposomes were internalized by folate-receptor-mediated endocytosis at 37 degrees C but not at 4 degrees C. These folate-PEG liposomes show potential for delivering large quantities of low molecular weight compounds nondestructively into folate receptor-bearing cells.

Bitetrahydroanthracenes from flowers of Cassia torosa Cav.

A new bitetrahydroanthracene derivative, torosaol-III, was isolated from the flowers of Cassia torosa Cav. along with physcion, 5,7'-physcionanthrone-physcion, 5,7'-biphyscion, torosanin-9,10-quinone, 5,7-dihydroxy-chromone, naringenin, and chrysoeriol. The structure of torosaol-III was established as 3,3'-4,4'-tetrahydro-3,3'8,8'9,9'-hexahydroxy-6,6'-dimethoxy-3,3'- dimethyl-1(2H),1'(2H)-5,7'-bianthracenone on the basis of spectral and chemical evidence. Dimeric tetrahydroanthracenes exhibited cytotoxic activity against KB cells in the tissue culture.