Phenoxazine Derivatives Research Articles

Influence of the Electrode Material on the Electrochemical Behavior of Carbon Paste Electrodes Modified with Meldola Blue and Methylene Green Adsorbed on a Synthetic Zeolite

AbstractCarbon paste electrodes modified with a phenoxazine derivative, Meldola blue, and a phenothiazine derivative, methylene green, both strongly adsorbed on a synthetic zeolite were investigated using either glassy carbon powder (Sigradur K, SK) or single‐walled carbon nanotubes (SWCNT) as conductive electrode material. In the case of SWCNT based electrodes, the formal potential of both mediators was pH dependent, as expected for a redox process involving proton transfer. In contrast, the formal potential of both mediators of SK based modified electrodes was practically insensitive to pH. This behavior is discussed in terms of interactions existing in the heterogeneous system mediator‐zeolite‐electrode material.

Synthesis of Heterocycle-linked Thioureas and Their Inhibitory Activities of NO Production in LPS Activated Macrophages

A series of thioureas were synthesized as inhibitors of NO production in lipopolysaccharide-activated macrophages. We investigated the effect of lipophilic moiety and N-substituents of the thioureas on the activity. Phenoxazine and carbazole-containing derivatives revealed higher activity than indole-containing thioureas. The appropriate spacer between lipophilic tail and thiourea head and methyl substituent at N3 position of thiourea brought beneficial effect on the inhibition of NO production. Among prepared compounds, phenoxazine-containing derivative 2a was the most potent with 2.32 μM of IC 50 value. RT-PCR analysis suggested that the prepared thioureas inhibited NO production through the suppression of iNOS mRNA expression.

In Vitro Antibacterial Activity of Phx-3 against Helicobacter pylori

Phx-3, one of the phenoxazine derivatives, is reported to have inhibitory effect on Mycobacterium species and Chlamydia pneumoniae but not Escherichia coli, Salmonella Typhimurium, Pseudomonas aeruginosa, Staphylococcus aureus, Listeria monocytogenes. The bactericidal activities of Phx-3 against Helicobacter pylori strains have not been assessed. Then, we measured minimum inhibitory concentration of Phx-3 for Helicobacter strains and assessed the morphological and biochemical effects of Phx-3 on H. pylori. In present study, it has shown that H. pylori strains including clarithromycin resistant strain and Helicobacter musterae were killed effectively by the treatment with Phx-3. Furthermore, severe morphological changes such as membrane blebbing and formation of hollows in H. pylori were detected. In addition, induction of heat shock protein 60 was observed. Taken together, Phx-3 has antibacterial activity against Helicobacter pylori.

Phenoxazine Derivatives Suppress the Infections Caused by Herpes Simplex Virus Type-1 and Herpes Simplex Virus Type-2 Intravaginally Inoculated Into Mice

We examined the in vivo antiviral activities of 2-amino-4,4α-dihydro-4α-7-dimethyl-3H-phenoxazine-3-one (Phx-1), 3-amino-1,4α-dihydro-4α-8-dimethyl-2H-phenoxazine-2-one (Phx-2), and 2-aminophenoxazine-3-one (Phx-3) against herpes viruses. The virus yield three days after administration, changes in the 6-degree’s lesion scores, and the morbidity were assessed after herpes simplex virus type-1 (HSV-1) [acyclovir (ACV)-sensitive KOS strain or ACV-resistant A4-3 strain] or HSV-2 (ACV-sensitive UW 268 strain) was inoculated intravaginally to mice with administration of Phx-1, Phx-2, Phx-3, or ACV (0.2 mg per administration, 3 times daily) for 8 days starting from 1 day before virus inoculation to 7 days after infection. Phx-1, Phx-2, and Phx-3 extensively suppressed the virus yield of HSV-1. Only Phx-2 exerted moderate inhibitory effects against HSV-2 in mice. The lesion scores, as clinical signs manifested by infection of the KOS strain of HSV-1, were extensively suppressed by intravaginal application of Phx-1, Phx-2, or Phx-3. The lesion scores in HSV-2–infected mice indicated moderate suppression, when Phx-1, Phx-2, or Phx-3 was applied. Without treatment by one of the compounds, none of the HSV-1– infected mice died, but all the HSV-2–infected ones did. However, by the administration of Phx-1, Phx-2, or Phx-3 fairly improved the survival rates of the HSV-2–infected mice. Phx-2 showed dose-dependent anti-HSV-2 efficacy when administered at doses of 0.2 and 1 mg per administration. The present in vivo data suggest that the Phx-1, Phx-2, and Phx-3 are attractive candidates for agents to prevent both replication of HSV and aggravation of lesions caused by these viruses.

Novel oxidative electrophilic coupling reactions of phenoxazine derivatives with MBTH and their applications to spectrophotometric determination of residual chlorine in drinking water and environmental water samples

Novel, sensitive and rapid spectrophotometric methods, using phenoxazine (PNZ), 2-chlorophe-noxazine (CPN) and 2-trifluoromethylphenoxazine (TPN) as chromogenic reagents for the determination of residual chlorine are proposed. The methods are based on the reduction of chlorine by an electrophilic coupling reagent, 3-methyl-2-benzothiazoline hydrazono hydrochloride hydrate (MBTH) in mild hydrochloric acid medium and subsequent coupling with PNZ, CPN or TPN. The blue color formed in the reaction showed maximum absorbance at 680–690 nm and obeyed Beer's law over the range 0.1–2.2 μg ml −1. The molar absorptivity values with PNZ, CPN and TPN were 2.80 × 10 4, 2.67 × 10 4 and 1.91 × 10 4 l mol −1 cm −1 and Sandell's sensitivity values were 0.028, 0.027 and 0.028 μg cm −2 respectively. The proposed methods were successfully applied in the determination of residual chlorine in drinking water and environmental water samples. The performance of proposed methods was evaluated in terms of Student's t-test and variance ratio F-test which indicated the significance of proposed methods over the standard spectrophotometric method.

Anticancer Effects of Phenoxazine Derivatives Revealed by Inhibition of Cell Growth and Viability, Disregulation of Cell Cycle, and Apoptosis Induction in HTLV-1–Positive Leukemia Cells

Adult T-cell leukemia (ATL) is a malignant tumor of human CD4(+) T cells infected with a human retrovirus, T lymphotropic virus type-1 (HTLV-1). The aim of the present study was to investigate the apoptotic effects of phenoxazines, 2-amino-4,4alpha-dihydro-4alpha,7-dimethyl-3H-phenoxazine-3-one (Phx-1), 3-amino-1,4alpha-dihydro-4alpha,8-dimethyl-2H-phenoxazine-2-one (Phx-2), and 2-aminophenoxazine-3-one (Phx-3) on a T cell leukemia cell line from ATL patients, MT-1 cells; HTLV-1 transformed T-cell lines, HUT-102 cells and MT-2 cells; and an HTLV-1-negative rat sarcoma cell line, XC cells. Among these phenoxazines, Phx-3 at concentrations of less than 10 microg/ml extensively inhibited growth and cell viability; arrested cell cycles at sub G(0)/G(1) phase; and augmented apoptosis of MT-1, HUT-102, and MT-2 cells. However, these phenoxazines did not affect the cell viability of an HTLV-1-negative rat sarcoma cell line, XC cells, and phytohemaggutinin-activated human peripheral blood mononuclear cells, although they markedly inhibited the growth of these cells. The transmission of HTLV-1 from HTLV-1-positive cells (MT-2 cells) to HTLV-1-negative cells (XC cells) was considered to be prevented by Phx-1, Phx-2, or Phx-3 because the syncytium formation between these cells was inhibited markedly in the presence of these phenoxazines. The present results suggest that Phx-1, Phx-2, and, in particular, Phx-3 may be useful as therapeutic agents against ATL, which is extremely refractory to current therapies.

Suppression of the proliferation of cancer cell lines, KB-3-1 and K562 cells preceded by a decrease in intracellular pH caused by phenoxazine derivatives

The intracellular pH (pHi) of cancer cells such as the KB-3-1 (human epidermoid carcinoma cell line) and K562 cells (human chronic myeloid leukemia cell line) cultured in a medium (pH 7.4) was found to be much higher (pH 7.65 and 7.8, respectively) than that of normal cells (pHi is usually < or =7.2). When a phenoxazine derivative, 2-aminophenoxazine-3-one (Phx-3) or 2-amino-4,4alpha-dihydro-4alpha-7-dimethyl-3H-phenoxazine-3-one (Phx-1) was added to these cells, pHi rapidly decreased within 20 min, dose-dependently, though the extent of the decrease of pHi was significantly larger for Phx-3 (a decrease of 0.9 units) than for Phx-1 (a decrease of 0.4 units). Phx-3 and Phx-1 caused the proliferative suppression of these cells 24 h after the addition, dose-dependently. The anti-proliferative effects of Phx-3 on KB-3-1 and K562 cells were far greater than those of Phx-1. It was proposed that the proliferative suppression of KB-3-1 and K562 cells caused by Phx-3 and Phx-1, may be preceded by a rapid and extensive decrease in pHi, which possibly influenced the intracellular homeostasis, finally causing the suppressed proliferation and apoptosis of these cancer cells. The present results suggest that the anti-cancer effects of Phx-3 and Phx-1 may be strengthened by the intracellular acidification of cancer cells by these compounds.

Phenoxazine derivative, 2-amino-4,4α-dihydro-4α,7-dimethyl-3H-phenoxazine-3-one suppresses growth of human retinoblastoma cell line Y79 in vitro and in vivo

The aim of the study was to evaluate the in vitro and in vivo antitumor effects of the 2-amino-4,4alpha-dihydro-4alpha,7-dimethyl-3H-phenoxazine-3-one (Phx-1) on the human retinoblastoma cell line Y79. The in vitro effects of Phx-1 on cell viability and apoptosis of the human retinoblastoma Y79 cells, were studied by using colorimetric and flow-cytometric methods. The in vivo antitumor effects of Phx-1 on the human retinoblastoma Y79 cells subcutaneously transplanted in BALB/c nude mice were studied, examining the tumor size, the adverse effects on the mice and the histopathological evaluations including hematoxylin and eosin and immunohistochemical staining in the mass of tumors of human retinoblastoma Y79 cells isolated from the mice. Phx-1 suppressed the viability of Y79 cells dose- and time-dependently and induced apoptosis in Y79 cells in vitro. Phx-1 markedly reduced the growth of Y79 cells transplanted into the mice without causing bodyweight loss. Pathological findings of the tumor mass isolated from mice revealed that the tumor of Y79 cells treated with Phx-1 had a decreased mitotic index, decreased expression of Ki67 and p53, no alteration of bcl-2 level and increased caspase-3 activity compared with the the control. Present results suggested that Phx-1 demonstrated antitumor activity against the human retinoblastoma Y79 cells in vitro and in vivo, by inhibiting cell growth and inducing apoptosis. In addition, Phx-1 exerted few adverse side effects on the mice. Phx-1 may be a useful antitumor drug in the treatment of retinoblastoma, which is the most common and serious intraocular malignant tumor.

Phenoxazine Derivatives Inactivate Human Cytomegalovirus, Herpes Simplex Virus-1, and Herpes Simplex Virus-2 In Vitro

We examined whether phenoxazine derivatives, 2-amino-4,4α-dihydro-4α-7-dimethyl-3H-phenoxazine-3-one (Phx-1), 3-amino-1,4α-dihydro-4α-8-dimethyl-2H-phenoxazine-2-one (Phx-2), and 2-amino-phenoxazine-3-one (Phx-3) may have antiviral activity against herpes family viruses: human cytomegalovirus (HCMV), herpes simplex virus type 1 (HSV-1), and herpes simplex virus type 2 (HSV-2). The antiviral activity was evaluated by the selectivity index (SI), which is the ratio of 50% cytotoxic concentration (CC50) and 50% antiviral concentration (IC50). Among these phenoxazines, Phx-2 exerted strong antiviral activity to HCMV with the SI of 200, while Phx-1 and Phx-3 exerted no marked anti-HCMV activity. Phx-2 also showed moderate inhibition of HSV-1 and HSV-2, with the SI of 6.7 and 17, respectively. In the time-of-addition experiments, inhibitory effect of Phx-2 against HCMV was active even when applied to cells at 100 h after HCMV infection, while ganciclovir (GCV) showed potent inhibition when applied to cells before 42-h post-infection, but its inhibitory effects disappeared thereafter. Attachment and penetration of HCMV was not affected by the presence of Phx-2. When HCMV was pretreated with Phx-2, concentration-dependent virucidal action was observed, suggesting that Phx-2 inactivates HCMV directly. From these data, it was found that Phx-2 might have a different anti-HCMV target from GCV.

Plasmid Loss in Plasmid-carrying Strains of Escherichia coli Treated with Phenoxazines and an Approach to Study Their DNA Binding Properties

The effect of subinhibitory concentrations of 2-trifluoromethyl-N10-substituted phenoxazines on plasmid-coded antibiotic resistance in Escherichia coli was investigated. Phenoxazine treatment resulted in the loss of resistance markers to an extent of 8-63% in all the strains tested, and the disappearance of plasmid DNA in phenoxazine sensitive colonies was evidenced by agarose gel electrophoresis. The resistant strains were sensitized in the presence of phenoxazines with a concomitant reduction in the MIC (minimum inhibitory concentration) values. The UV, fluorescence spectral, and ethidium bromide displacement agarose gel assay methods revealed that phenoxazines are intercalated with plasmid DNA. Progressive addition of DNA led to a significant reduction in the peak intensity of the absorption maximum of phenoxazine derivative. Further, destabilization of ethidium bromide-DNA complex as seen from fluorescence microscopy in the presence of phenoxazines was observed. The potency of phenoxazines to sensitize the resistant organisms follows the order butyl > propyl > acetyl derivatives.

Synthesis of short and long-wavelength functionalised probes: amino acids' labelling and photophysical studies

Fluorescent labelling of α-amino acids at their N or C terminals in the main and lateral chains at short and long wavelengths was carried out in different ways. The N-[3-(naphthalen-1-ylamino)propanoyl]amino acid methyl esters synthesised showed strong fluorescence in the visible region (∼415 nm) of the electromagnetic spectrum. Condensation of these compounds with 5-diethylamino-2-nitrosophenol or 5-ethylamino-4-methyl-2-nitrosophenol produced the benzo[ a]phenoxazine derivatives, with maximum emission wavelengths shifted to values higher than 644 nm. The synthesis of novel functionalised 5,9-diaminobenzo[ a]phenoxazinium salts, by reaction of 5-ethylamino-4-methyl-2-nitrosophenol and N-substituted 1-naphthylamine and their use in the covalent labelling of the N or C terminals of valine, produced derivatives with long-wavelength emissions (644–653 nm). Photophysical studies using the synthesised compounds both in different solvents and in controlled pH were undertaken. Preliminary evaluation of photostability of the cationic polycyclic heterocycles in ethanol and water at physiological pH was also performed.

Synthesis, characterisation and antimicrobial activity of new benzo[ a]phenoxazine based fluorophores

N-[5-(3-Aminopropylamino)-10-methyl-9 H-benzo[ a]phenoxazin-9-ylidene]ethanaminium chloride (Bze-NH 2) was prepared and used as a precursor in the synthesis of new polycyclic cationic dyes. In addition to the potentiality of Bze-NH 2 as a non-covalent fluorescent probe, the presence of a free amino group in its structure prompted us to study the application of this functionalised heterocycle in the covalent labelling of glycine and valine amino acids, as models of biomolecules. All compounds obtained showed strong absorbance and high emission at long-wavelengths ( λ em >640 nm). Furthermore, all benzo[ a]phenoxazine derivatives synthesised were evaluated as antifungal agents against Saccharomyces cerevisiae, considering the commercial Nile Blue A (NB) as a lead compound. The results revealed that they exhibited good activity, which was usually superior to NB, the most effective compound displaying a minimum inhibitory concentration (MIC) value of 15 μM.

Synthesis and characterization of a novel electroluminescent polymer based on phenoxazine and fluorene derivatives

A new electroluminescent polymer was prepared by oxidative coupling copolymerization of N-(4- n-butylphenyl)phenoxazine (PPX) and 9,9-di- n-butylfluorene (DBF) using iron(III) chloride. The obtained polymers were soluble in common organic solvents and had number-average molecular weight as high as 10,000. The UV–vis absorption maximum and photoluminescence peak shifted to longer wavelengths with the increase of PPX content. The increase of PPX content also caused increase of hole mobility and decrease of electron mobility. A simple single-layer light-emitting-diode device having a structure of indium tin oxide/polymer/Ca/Al was fabricated. The polymer containing 30% of PPX unit showed highest electroluminescent properties with a maximum luminance of 1084 cd/m 2 at 15.5 V operating voltage.

Caspase-independent cell death revealed in human gastric cancer cell lines, MKN45 and KATO III treated with phenoxazine derivatives

We examined whether phenoxazine derivatives such as 2-amino-4,4alpha-dihydro-4alpha,7-dimethyl-3H-phenoxazine-3-one (Phx-1) and 2-aminophenoxazine-3-one (Phx-3) may have anticancer effects on the human gastric cancer cell lines, MKN45, MKN74, MKN7 and KATO III in vitro. Phx-1 inhibited the growth of these cancer cells in a dose- and time-dependent manner. The IC50 was approximately 65, 25, 100 and 70 microM for MKN45, MKN74, MKN7 and KATO III respectively, after 72 h. Phx-3 exerted stronger antiproliferative effects against these cancer cells (IC50: approximately 5, 1, 10 and 10 microM for MKN45, MKN74, MKN7 and KATO III, respectively, after 72 h) than Phx-1. Phx-1 and Phx-3 increased the population of TUNEL-positive cells in MKN45 and KATO III time-dependently from 24 to 72 h, suggesting that Phx-1 and Phx-3 have apoptotic activity against these gastric cancer cells. The activity of effector caspase-3 significantly increased in MKN45 treated with Phx-3 for 24 h, but did not altered in the cells treated with Phx-1 for 24 h. When z-VAD-fmk, a pan-caspase inhibitor, was co-treated for 24 h, Phx-3-stimulated caspase-3 activity in MKN45 was reversed to the levels of normal activity, while the antiproliferative and apoptotic effects of Phx-3 against the cells were maintained. The activity of caspase-3 was not activated in KATO III by 24 h exposure for Phx-1 or Phx-3. In conclusion, both phenoxazines prevent the growth of the human gastric cancer cell lines, MKN45 and KATO III in vitro, and cause the apoptosis of these cell lines via a caspase-independent pathway. Although the intracellular action mechanisms of Phx-1 and Phx-3 are still unclear, these phenoxazines may be useful for the treatment of gastric cancer in the future.

Phenoxazine Derivatives 2-Amino-4,4.ALPHA.-dihydro-4.ALPHA.-phenoxazine-3-one and 2-Aminophenoxazine-3-one-Induced Apoptosis through a Caspase-Independent Mechanism in Human Neuroblastoma Cell Line NB-1 Cells

The aim of the present study was to determine whether phenoxazines such as 2-amino-4,4-alpha-dihydro-4alpha-phenoxazine-3-one (Phx-1) and 2-aminophenoxazine-3-one (Phx-3) may suppress the proliferation of human neuroblastoma cell line, NB-1 that is refractory to chemotherapeutic agents, inducing apoptosis through the activation of caspase pathway or not. Phx-1 and Phx-3 suppressed the proliferation of NB-1 cells extensively dependent on dose and time. The IC50 of Phx-1 and Phx-3 was about 20 microM and 0.5 microM, respectively, when the cells were treated with Phx-1 or Phx-3 for 72 h. Phx-1 and Phx-3 caused the mixed types of cell death-apoptosis and necrosis-in NB-1 cells, which was detected by flow cytometry. The induction of apoptosis/necrosis caused by these phenoxazines seemed to be correlated dominantly with the caspase independent pathway, because the increased activity of effector caspase 3/7 in NB-1 cells caused by 50 microM Phx-1 or 20 microM Phx-3 was completely cancelled by the addition of z-VAD-fmk, a pan-caspase inhibitor, but such phenoxazines-suppressed viability of NB-1 cells was not recovered to normal levels by this inhibitor. The results of this study demonstrate that Phx-1 and Phx-3 have antitumor activity against the neuroblastoma cell line, NB-1, though the IC50 was extremely low for Phx-3, inducing the mixed types of cell death, apoptosis and necrosis, caspase-independently.

Antioxidants determination with laccase

The spectrophotometric method of antioxidants determination using recombinant laccase Polyporus pinsitus (rPpL) and Myceliophthora thermophila (rMtL) was developed. The method includes simultaneous oxidation of the antioxidant and high reactive laccase substrate producing chromophoric radical cation. As laccase substrates ABTS and other high reactive phenoxazine derivatives: 2-phenoxazin-10-yl-ethanol (PET), 3-phenoxazin-10-yl-propane-1-sulfonic acid (PPSA) and 3-phenoxazin-10-yl-propionic acid (PPA) were used. The kinetic data were analysed using a scheme of simultaneous oxidation of the antioxidant and the substrate. In a range of (0.9–7.3) × 10 −6 M of Trolox the measurings recovered 91 and 99% of the antioxidant if ABTS and both laccases were used. The recovery varied between 82 and 124% if phenoxazine derivatives were used. The antioxidant activity determined in rich with antioxidants food samples, i.e. date-palm, black raisin, golden raisin, skin of red grape, dice of red grape, fitted the literature data.

Synthesis and characterization of a novel electroluminescent polymer based on a phenoxazine derivative

AbstractWe report the preparation of a new electroluminescent polymer by the oxidative coupling copolymerization of N‐(4‐n‐butylphenyl)phenoxazine and 9,9‐di‐n‐butylfluorene with ferric(III) chloride. The reaction yields soluble polymers with a weight‐average molecular weight as high as 9000. The reactivity has been studied with respect to the reaction time, temperature, and feed ratio of the comonomers. Under optimum conditions, a copolymer with a 50% comonomer incorporation ratio can be obtained in a 75% yield. The polymers have been characterized with differential scanning calorimetry, cyclic voltammetry, and optical spectroscopy. A simple single‐layer light‐emitting‐diode device of an indium tin oxide/polymer/Mg–Ag structure shows a luminance of 200 cd/m2 at an 18‐V operating voltage. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4338–4345, 2006

A study on the perturbation of model lipid membranes by phenoxazines

The interactions of six newly synthesized phenoxazine derivatives with lipid bilayers were studied by means of calorimetry, fluorescence spectroscopic methods and electron spin resonance. Depending on their structure studied compounds decreased membrane fluidity and increased lipid order in liquid-crystalline bilayers to different degrees. These studies showed also that phenoxazine molecules are located close to the polar/apolar interface of bilayer. The results allow to conclude that phenoxazines rather weakly interact with lipid bilayers.

A Long-Wavelength Fluorescent Glucose Biosensor Based on Bioconjugates of Galactose/Glucose Binding Protein and Nile Red Derivatives

Fluorescent biosensors based on galactose/glucose binding protein (GGBP) and environmentally sensitive derivatives of the phenoxazine dye Nile Red are described. These biosensors are proposed as the sensing platform for a minimally invasive, continuous glucose monitoring system that can be implanted under the skin and read transdermally using an external fluorometer. To construct the biosensors, the thiol-reactive Nile Red derivatives INR and IANR were prepared and conjugated to GGBP proteins possessing cysteine mutations that were designed for optimal site-specific fluorophore attachment. The attachment sites were selected to maximize the local environment change for attached dyes between the bound and unbound conformations of GGBP. Fluorescence responses at the selected cysteine sites of GGBP upon binding to glucose showed that the conjugates typically yielded fluorescence emission around 640-650 nm with up to 50% changes in fluorescence intensity. Conjugate E149C/A213C/L238S INR GGBP also displayed glucose binding in the human physiological range (K (D) = 7.4 mM). The phenoxazine derivatives fluoresced at longer wavelengths (>600 nm) approaching the near-infrared spectral window, where interference from scattering and tissue absorbance are minimal. Ultimately, we expect that monitoring systems based on GGBP and longwavelength dyes will be implanted for up to 6 months and can be used to transmit information through the skin to an external monitor.

Anticancer effects of phenoxazine derivatives combined with tumor necrosis factor-related apoptosis-inducing ligand on pancreatic cancer cell lines, KLM-1 and MIA-PaCa-2

The aim of this study was to investigate the anticancer effects of the phenoxazine derivatives, 2-amino-4,4alpha-dihydro-4alpha,7-dimethyl-3H-phenoxazine-3-one (Phx-1), 3-amino-1,4alpha-dihydro-4alpha,8-dimethyl-2H-phenoxazine-2-one (Phx-2), and 2-aminophenoxazine-3-one (Phx-3) on human pancreatic cancer cell lines, KLM-1 and MIA-PaCa-2, in combination with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a member of the tumor necrosis factor superfamily of cytokines. Of these three phenoxazines, Phx-1 and Phx-3 inhibited proliferation of KLM-1 dose-dependently, but Phx-2 did not. Phx-3 caused both apoptosis and necrosis in KLM-1 cells, as evidenced by the phosphatidylserine externalization and propidium iodide permeable cells detected by a flow cytometric method using annexin-V and propidium iodide. Down-regulation of Bcl-2 expression appeared to be involved in the Phx-3-induced cell death. TRAIL did not affect proliferation of KLM-1, and the inhibitory effects of Phx-1 and Phx-3 on the KLM-1 cell line were not augmented by the combination with TRAIL. On the other hand, proliferation of the MIA-PaCa-2 cell line was not affected by Phx-1, Phx-2 and Phx-3, although it was significantly inhibited by TRAIL in a dose-dependent manner. Inhibitory effects of TRAIL on MIA-PaCa-2 were synergistically augmented by the addition of Phx-1 and Phx-3, but not by Phx-2. These results suggest that both Phx-1 and Phx-3 exert anticancer effects against human pancreatic cancer cells, KLM-1 and MIA-PaCa-2, through distinct action modes. Phx-1 and Phx-3 may be effective for the treatment of pancreatic cancer.