Mouse Leukemia L1210 Cells Research Articles

Okeaniazole A: Thiazole-containing cyclopeptide from the marine cyanobacterium Okeania hirsuta with antileishmanial activity

A macrocyclic peptide, okeaniazole A (1), was isolated from the Okinawan marine cyanobacterium, Okeania hirsuta. The planar structure was elucidated by the analyses of MS and NMR spectra. The absolute configuration of the amino acid residues was determined by a combination of ozonolysis, hydrolysis, and Marfey’s analysis. Okeaniazole A (1) and a related cyclic heptapeptide dolastatin 3 (2) exhibited antileishmanial activity, with IC50 values of 12.1 and 12.5 µM, respectively. These two compounds did not show any cytotoxicity toward L1210 mouse leukemia cells at concentrations of 100 µM.

N-Desmethylmajusculamide B, a lipopeptide isolated from the Okinawan cyanobacterium Okeania hirsuta.

A new lipopeptide, N-desmethylmajusculamide B (1), was isolated from the Okinawan cyanobacterium Okeania hirsuta along with 2 known compounds majusculamide A (2) and majusculamide B (3). The planar structure of (1) was elucidated by a detailed analysis of mass spectrometry and nuclear magnetic resonance spectra. The absolute configurations of the amino acid residues were determined using Marfey's analysis. The configuration of C-16 in the α-methyl-β-keto-decanoyl moiety was determined unambiguously to be S by conducting a semisynthesis of N-desmethylmajusculamide B from 3. The cytotoxicity against mouse L1210 leukemia cells was evaluated for majusculamides (1-3).

Antiproliferative Activity of Extracts and Fractions from Irradiated Curcuma zanthorrhiza Rhizomes Against Mouse Leukemia and Human Cancer Cell Lines

Curcuma zanthorrhiza Roxb. is a medicinal plant that is used as a raw material in the herbal medicine and pharmaceutical industries. The main content of C. zanthorrhiza is curcuminoid, which is used as an antioxidant and an anticancer agent. The aim of this research was to study the effect of gamma radiation used for preserving simplicia or herbal drugs through the examination of their cytotoxicity against mouse leukemia L1210 cells and antiproliferative activity against human cancer cell lines HUT78, A549, HeLa, and THP1. The samples of curcuma rhizome were irradiated by gamma ray emitted by Cobalt-60 as a source at doses of 0 (control), 5, 7.5, 10, and 15 kGy. After irradiation, the samples were macerated using n -hexane, ethyl acetate, and ethanol, respectively. Preliminary cytotoxicity test toward extract from control sample against mouse leukemia L1210 cells revealed that the ethyl acetate extract was the most active extract inhibiting the growth of cells with an IC 50 value of 16.6 µg/mL, followed by ethanol extract (18.8 µg/mL) and n -hexane extract (42.7 μg/mL). Fractionation using a chromatography column of the ethyl acetate extract resulted in seven fractions denoted as F1-F7. The cytotoxicity test of the seven fractions against mouse leukemia L1210 cells showed that fraction 3 (F3) was the most active fraction with an IC 50 value of 10.0 μg/mL, followed by F7 (11.2 μg/mL), F6 (11.8 μg/mL), F5 (12.0 μg/mL), F1 (13.2 μg/mL), F4 (14.5 μg/mL), and F2 (27.8 μg/mL), respectively. Based on these results, all irradiated samples were then extracted, fractionated, and tested for cytotoxicity in a similar manner. The result showed that irradiation of samples under doses up to 10 kGy can be used to preserve Curcuma zanthorrhiza simplicia without damaging its efficacy. To ensure that the irradiation dose of 10 kGy did not reduce anticancer activity, the F3 from the irradiated sample at a dose of 10 kGy was also examined of its in-vitro antiproliferative activity using HUT78, A549, HeLa, and THP1 human cancer cell lines. The results showed that irradiation of the sample at a dose of 10 kGy reduced the antiproliferative activity of F3 against HUT78 (32 %), A549 (48 %), HeLa (42 %), and THP1 (31 %). However, its reduction did not eliminate its antiproliferative activities. These results indicated that the preservation of simplicia using radiation can be done at a maximum radiation dose of 10 kGy by modifying the concentration of simplicia in the fabrication process of herbal medicine formulation.

Chemotherapy medication of Vincristine and Vinblastine

Cancers treated with Vincristine and vinblastine include: acute leukemia, Hodgkin's and non- Hodgkin's lymphoma, neuroblastoma, rhabdomyosarcoma, Ewing's sarcoma, Wilms' tumor, multiple myeloma, chronic leukemias, thyroid cancer, brain tumors, non-small cell lung cancer, bladder cancer, melanoma, and testicular cancer andIt is also used to treat some blood disorders. It is given by injection into a vein. Vincristine and vinblastine exhibit differential activity against tumors and normal tissues. In this work, a number of cultured cell lines were assayed for their sensitivity to the antiproliferative and cytotoxic effects of the two drugs following short-term (4 hr) or during continuous exposures. Differential activity was not seen when cells were subjected to continuous exposures. The concentrations of Vincristine and vinblastine, respectively, that inhibited growth rates by 50% were: mouse leukemia L1210 cells, 4.4 and 4.0 nw; mouse lymphoma S49 cells, 5 and 3.5 nM; mouse neuroblastoma cells, 33 and 15 nw; HeLa cells, 1.4 and 2.6 nw; and human leukemia HL-60 cells, 4.1 and 5.3 nM. In contrast, differential toxicity was seen when cells were subjected to 4-hr exposures and transferred to drug-free medium: the 50% growth-inhibitory concentrations for Vincristine and vinblastine, respectively, for inhibition (a) of proliferation of L1210 cells were 100 and 380 nM and of HL-60 cells were 23 and 900 nM and (b) of colony formation of L1210 cells were 6 and >600 nM and of HeLa cells were 33 and 62 nM. Uptake and release of [3H]- vincristine and [3H]vinblastine were examined in L1210 cells under the conditions of growth experiments. Uptake of both drugs was dependent on the pH of culture media, and signifi cantly greater amounts of [3H]vinblastine than of [3H]vincristine were associated with cells after 4-hr exposures to equal concen trations of either drug. When cells were transferred to drug-free medium after 4-hr exposures, vinblastine was released much more rapidly from cells than was Vincristine, and by 0.5 hr after resuspension of cells, the amount of Vincristine associated with the cells was greater than the amount of vinblastine and remained so for up to at least 6 hr.

Preclinical Evaluation of the Short-Term Toxicity of 4-(N)-Docosahexaenoyl 2´, 2´- Difluorodeoxycytidine (DHA-dFdC).

This study was designed to test the short-term toxicity of DHA-dFdC in a mouse model and its efficacy in a mouse model of leukemia at or below its repeat-dose maximum tolerated dose (RD-MTD). A repeat-dose dose-ranging toxicity study was designed to determine the tolerability of DHA-dFdC when administered to DBA/2 mice by intravenous (i.v.) injection on a repeat-dose schedule (i.e. injections on days 0, 3, 7, 10, and 13). In order to determine the effect of a lethal dose of DHA-dFdC, mice were injected i.v. with three doses of DHA-dFdC at 100mg/kg on days 0, 3, and 5 (i.e. a lethal-RD). The body weight of mice was recorded two or three times a week. At the end of the study, major organs (i.e. heart, liver, spleen, kidneys, lung, and pancreas) of mice that received the lethal-RD or RD-MTD were weighed, and blood samples were collected for analyses. Finally, DHA-dFdC was i.v. injected into DBA/2 mice with syngeneic L1210 mouse leukemia cells to evaluate its efficacy at or below RD-MTD. The RD-MTD of DHA-dFdC is 50mg/kg. At 100mg/kg, a lethal-RD, DHA-dFdC decreases the weights of mouse spleen and liver and significantly affected certain blood parameters (i.e. white blood cells, lymphocytes, eosinophils, and neutrophil segmented). At or below its RD-MTD, DHA-dFdC significantly prolonged the survival of L1210 leukemia-bearing mice. DHA-dFdC has dose-dependent toxicity, affecting mainly spleen at a lethal-RD. At or below its RD-MTD, DHA-dFdC is effective against leukemia in a mouse model.

Carbon Isotopomer Analysis with Non-Unifom Sampling HSQC NMR for Cell Extract and Live Cell Metabolomics Studies.

Isotopomer analysis using either 13C NMR or LC/GC-MS has been an invaluable tool for studying metabolic activities in a variety of systems. Traditional challenges are, however, that 13C-detected NMR is insensitive despite its high resolution, and that MS-based techniques cannot easily differentiate positional isotopomers. In addition, current 13C NMR or LC/GC-MS has limitations in detecting metabolites in living cells. Here, we describe a non-uniform sampling-based 2D heteronuclear single quantum coherence (NUS HSQC) approach to measure metabolic isotopomers in both cell lysates and living cells. The method provides a high resolution that can resolve multiplet structures in the 13C dimension while retaining the sensitivity of the 1H-indirect detection. The approach was tested in L1210 mouse leukemia cells labeled with 13C acetate by measuring NUS HSQC with 25% sampling density. The results gave a variety of metabolic information such as (1) higher usage of acetate in acetylation pathway than aspartate synthesis, (2) TCA cycle efficiency changes upon the inhibition of mitochondrial oxidative phosphorylation by pharmacological agents, and (3) position-dependent isotopomer patterns in fatty acids in living cells. In addition, we were able to detect fatty acids along with other hydrophilic molecules in one sample of live cells without extraction. Overall, the high sensitivity and resolution along with the application to live cells should make the NUS HSQC approach attractive in studying carbon flux information in metabolic studies.

Equivalent chemotherapy efficacy against leukemia in mice treated with topical vasoconstrictors to prevent cancer therapy side effects.

Topically applied vasoconstrictor is a new strategy to prevent oral mucositis and alopecia, two complications of chemotherapy and stem-cell transplant. We sought to determine whether mice treated with topical vasoconstrictor minutes before chemotherapy to suppress L1210 leukemia would develop a vasoconstrictor-induced L1210 cell sanctuary, and with it, significantly worse survival outcomes. B6D2F1 mice received 10(4) mouse L1210 leukemia cells via retro-orbital intravenous injection and were then divided into treatment groups, which included: (i) no further treatment, (ii) a single, sub-curative, intraperitoneal dose of cyclophosphamide (90 µg/gm bw) 24 hr after L1210 cell inoculation, (iii) topical epinephrine (25-400 mM) to clipped dorsal backs 20 min before cyclophosphamide or (iv) orotopical phenylephrine (16-130 mM), epinephrine (10 mM) or norepinephrine (25 mM) 20 min before cyclophosphamide. All mice were then followed until day of death. Differences in median survival time and percent survival between mice receiving cyclophosphamide alone and mice treated with either orotopical phenylephrine, epinephrine or norepinephrine; or topical epinephrine before cyclophosphamide were not significantly different. A discernible leukemia sanctuary was not created by topical vasoconstrictor treatment prior to chemotherapy; there was no significant difference in leukemia progression between untreated mice and those treated with either orotopical or topical vasoconstrictor before chemotherapy. We have opened a Phase I/IIa dose escalation trial to evaluate the safety and efficacy of orotopical phenylephrine in preventing oral mucositis in subjects undergoing hematopoietic stem cell transplant conditioning with cyclophosphamide plus total body irradiation. This could provide a cost-effective and convenient method to prevent oral mucositis.

Properties of phosphorylated thymidylate synthase

Thymidylate synthase (TS) may undergo phosphorylation endogenously in mammalian cells, and as a recombinant protein expressed in bacterial cells, as indicated by the reaction of purified enzyme protein with Pro-Q® Diamond Phosphoprotein Gel Stain (PGS). With recombinant human, mouse, rat, Trichinella spiralis and Caenorhabditis elegans TSs, expressed in Escherichia coli, the phosphorylated, compared to non-phosphorylated recombinant enzyme forms, showed a decrease in Vmaxapp, bound their cognate mRNA (only rat enzyme studied), and repressed translation of their own and several heterologous mRNAs (human, rat and mouse enzymes studied). However, attempts to determine the modification site(s), whether endogenously expressed in mammalian cells, or recombinant proteins, did not lead to unequivocal results. Comparative ESI-MS/analysis of IEF fractions of TS preparations from parental and FdUrd-resistant mouse leukemia L1210 cells, differing in sensitivity to inactivation by FdUMP, demonstrated phosphorylation of Ser10 and Ser16 in the resistant enzyme only, although PGS staining pointed to the modification of both L1210 TS proteins. The TS proteins phosphorylated in bacterial cells were shown by 31P NMR to be modified only on histidine residues, like potassium phosphoramidate (KPA)-phosphorylated TS proteins. NanoLC–MS/MS, enabling the use of CID and ETD peptide fragmentation methods, identified several phosphohistidine residues, but certain phosphoserine and phosphothreonine residues were also implicated. Molecular dynamics studies, based on the mouse TS crystal structure, allowed one to assess potential of several phosphorylated histidine residues to affect catalytic activity, the effect being phosphorylation site dependent.

Influence of the Expression Level of O6-Alkylguanine-DNA Alkyltransferase on the Formation of DNA Interstrand Crosslinks Induced by Chloroethylnitrosoureas in Cells: A Quantitation Using High-Performance Liquid Chromatography-Mass Spectrometry.

Chloroethylnitrosoureas (CENUs), which are bifunctional alkylating agents widely used in the clinical treatment of cancer, exert anticancer activity by inducing crosslink within a guanine-cytosine DNA base pair. However, the formation of dG-dC crosslinks can be prevented by O6-alkylguanine-DNA alkyltransferase (AGT), ultimately leading to drug resistance. Therefore, the level of AGT expression is related to the formation of dG-dC crosslinks and the sensitivity of cells to CENUs. In this work, we determined the CENU-induced dG-dC crosslink in mouse L1210 leukemia cells and in human glioblastoma cells (SF-763, SF-767 and SF-126) containing different levels of AGT using high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry. The results indicate that nimustine (ACNU) induced more dG-dC crosslinks in L1210 leukemia cells than those induced by carmustine (BCNU), lomustine (CCNU) and fotemustine (FTMS). This result was consistent with a previously reported cohort study, which demonstrated that ACNU had a better survival gain than BCNU, CCNU and FTMS for patients with high-grade glioma. Moreover, we compared the crosslinking levels and the cytotoxicity in SF-763, SF-767 and SF-126 cells with different AGT expression levels after exposure to ACNU. The levels of dG-dC crosslink in SF-126 cells (low AGT expression) were significantly higher than those in SF-767 (medium AGT expression) and SF-763 (high AGT expression) cells at each time point. Correspondingly, the cytotoxicity of SF-126 was the highest followed by SF-767 and SF-763. The results obtained in this work provided unequivocal evidence for drug resistance to CENUs induced by AGT-mediated repair of DNA ICLs. We postulate that the level of dG-dC crosslink has the potential to be employed as a biomarker for estimating drug resistance and anticancer efficiencies of novel CENU chemotherapies.

Induction of apoptosis associated with chromosomal DNA fragmentation and caspase-3 activation in leukemia L1210 cells by TiO2 nanoparticles

We investigated the effects of nanosized TiO2 particles on the death of mouse leukemia L1210 cells. TiO2 particles suppressed proliferation and induced cell death, as measured by lactate dehydrogenase (LDH) release into the culture medium. Chromatin condensation, which is typical of the initiation of cell death, was observed in approximately 14% cells cultured with titanium dioxide (TiO2) particles for 12 h. Furthermore, giant DNA fragments of approximately 2 Mbp and high-molecular-weight DNA fragments between 100 kbp and 1 Mbp were observed in cells cultured for 18 h with TiO2 particles. These giant and high-molecular-weight DNA fragments were further degraded into smaller DNA fragments, appearing as DNA ladders. Corresponding to the generation of DNA fragments, caspase-3 activity increased in cells treated with TiO2 particles. TiO2 particle-induced LDH release was not inhibited by cytochalasin D, an inhibitor of endocytosis. These results suggest that nanosized TiO2 particles can induce apoptosis associated with DNA fragmentation and caspase-3 activation and that TiO2 particle-induced apoptosis is not caused by endocytosis but is associated with contact of the particles with the cell surface.

Synthesis and Cytotoxic Activity of Novel 5-Substituted-1-(β-L-Arabinofuranosyl) Pyrimidine Nucleosides

A series of new 5-halogeno-1-(ß-L-arabinofuranosyl)uracils and their cytosine analogues were synthesized by halogenation of ara-L-uridine and ara-L-cytidine, respectively. The 5-(2-thienyl) and 5-halogenothienyl derivatives of both series were also prepared in excellent yields by Stille coupling followed by halogenation. All of these syntheses were based on benzoyl-protected derivatives. In vitro cytotoxicity experiments carried out using L1210 mouse leukemia cells showed that 5-(2-thienyl)-ara-L-uridine was the most potent compound of the new compounds; the majority of the analogues were not effective up to 200 μM concentrations.

Effect of thapsigargin on P-glycoprotein-negative and P-glycoprotein-positive L1210 mouse leukaemia cells

Expression of drug-transporting P-glycoprotein (P-gp, an integral protein of the plasma membrane) in neoplastic cells confers multidrug resistance and also involves alteration of cell sensitivity to inhibitors of the sarco/endoplasmic reticulum calcium pump thapsigargin (Th). Mouse leukaemia L1210 cell sublines that overexpress P-gp due to selection with vincristine (R) or stable transfection with a gene encoding human P-gp (T) were less sensitive to Th than the parental cell line (S). Th at a concentration of 0.1 μmol/l did not induce alterations in the amount of P-gp mRNA in R or T cells (S cells did not contain any measurable amount of this transcript as assessed by RT-PCR) or in the amount of calnexin (CNX) or glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in all three cell sublines. However, when using a concentration of 10 μmol/l, Th decreases the amounts of CNX, GAPDH (in S, R and T cells) and P-gp (in R and T cells) mRNAs. In contrast to R and T cells (which contain abundant P-gp), S cells did not contain any P-gp detectable by the c219 antibody on a Western blot. Th at a concentration of 0.1 μmol/l induced a reduction in the amount of P-gp present in R and T cells, particularly in isoforms with higher molecular weights (i.e., mature fully glycosylated isoforms). Similar results were observed when Th was used at a concentration of 10 μmol/l. R and T cells contained lower levels of CNX than S cells. While Th at a lower concentration did not alter the levels of CNX in S, R or T cells, a higher concentration of this substance induced a measurable decrease in the amount of CNX. S, R and T cells did not differ with respect to GAPDH content, but Th induced a reduction in the amount of this protein in all cell sublines. More pronounced results were observed when Th was applied at a concentration of 10 μmol/l comparing with a concentration of 0.1 mmol/l. These changes may be involved together with the Th efflux activity of P-gp in Th-resistance associated with the P-gp-mediated multidrug resistance of R and T cells.

An antifungal defensin from Phaseolus vulgaris cv. ‘Cloud Bean’

An antifungal peptide with a defensin-like sequence and exhibiting a molecular mass of 7.3 kDa was purified from dried seeds of Phaseolus vulgaris ‘Cloud Bean’. The isolation procedure entailed anion exchange chromatography on DEAE-cellulose, affinity chromatography an Affi-gel blue gel, cation exchange chromatography on SP-Sepharose, and gel filtration by fast protein liquid chromatography on Superdex 75. Although the antifungal peptide was unadsorbed on DEAE-cellulose, it was adsorbed on both Affi-gel blue gel and SP-Sepharose. The antifungal peptide exerted antifungal activity against Mycosphaerella arachidicola with an IC50 value of 1.8 μM. It was also active against Fusarium oxysporum with an IC50 value of 2.2 μM. It had no inhibitory effect on HIV-1 reverse transcriptase when tested up to 100 μM. Proliferation of L1210 mouse leukemia cells and MBL2 lymphoma cells was inhibited by the antifungal peptide with an IC50 of 10 μM and 40 μM, respectively.

Activity of Indenoisoquinolines against African Trypanosomes

African trypanosomiasis (sleeping sickness), caused by protozoan Trypanosoma brucei species, is a debilitating disease that is lethal if untreated. Available drugs are antiquated, toxic, and compromised by emerging resistance. The indenoisoquinolines are a class of noncamptothecin topoisomerase IB poisons that are under development as anticancer agents. We tested a variety of indenoisoquinolines for their ability to kill T. brucei. Indenoisoquinolines proved trypanocidal at submicromolar concentrations in vitro. Structure-activity analysis yielded motifs that enhanced potency, including alkylamino substitutions on N-6, methoxy groups on C-2 and C-3, and a methylenedioxy bridge between C-8 and C-9. Detailed analysis of eight water-soluble indenoisoquinolines demonstrated that in trypanosomes the compounds inhibited DNA synthesis and acted as topoisomerase poisons. Testing these compounds on L1210 mouse leukemia cells revealed that all eight were more effective against trypanosomes than against mammalian cells. In preliminary in vivo experiments one compound delayed parasitemia and extended survival in mice subjected to a lethal trypanosome challenge. The indenoisoquinolines provide a promising lead for the development of drugs against sleeping sickness.

Cytotoxic activity and chemical reactivity of cis-platinum(II) and trans-palladium(II) complexes with diethyl (pyridinylmethyl)phosphates

A series of square-planar platinum(II) and palladium(II) complexes of the formula cis-[PtCl 2L 2] and trans-[PdCl 2L 2] [L stands for diethyl (pyridin-2-ylmethyl)phosphate (2-pmOpe) or diethyl (pyridin-3-ylmethyl)phosphate (3-pmOpe) or diethyl (pyridin-4-ylmethyl)phosphate (4-pmOpe)] have been synthesized and tested in vitro for their cytotoxicity against mouse leukemia L1210 cells. The results indicated that the cis-platinum complexes showed superior activity than trans-palladium complexes, but lower in comparison to cisplatin. The chemical reactivity of the tested complexes has been determined in an in vitro NBP test. The platinum complexes exhibited very high chemical reactivity in NBP test, higher than cisplatin. The results showed no correlation between cytotoxicity and chemical reactivity for platinum complexes. Two platinum(II) complexes { cis-[PtCl 2(2-pmOpe) 2], cis-[PtCl 2(3-pmOpe) 2]} have been synthesized and characterized by IR, 1H NMR, 31P NMR, and elemental analysis.

Synthesis and evaluation of unsymmetrical polyamine derivatives as antitumor agents

A series of unsymmetrically substituted polyamine derivatives were prepared and their cytotoxicities in mouse leukemia L1210, melanoma B16, and HeLa cells were investigated. The in vitro cytotoxicity revealed that these conjugates could recognize the polyamine transporter, and the N-ethyl modified homospermidine moiety may be another efficient carrier as homospermidine even though the introduction of terminal alkyl groups led to reduced cytotoxicity in comparison with the un-substituted counterpart 1. The ornithine decarboxylase and topoisomerase II inhibition experiments indicated that ODC and TOPO II were potential, but not unique targets of these conjugates. Furthermore, the in vivo antitumor activities illustrated that the representative conjugate 2f and the homospermidine analogue 1 evidently inhibited the tumor growth and significantly increased the survival time of mice-bearing sarcoma 180 cells.

Cisplatin-induced cytoxicity: is the nucleus relevant?

cisplatin is a potent chemotherapeutic agent widely used for the treatment of cancer. However, cisplatin is frequently associated with nephrotoxicity, manifesting as acute kidney injury accompanied by hypokalemia and hypomagnesemia ([6][1]). Overdose of cisplatin has been reported to cause a wide

The synthesis and molecular recognization of the polyamine transporter of hydrazine-modified diamine conjugates

A series of four novel hydrazine-modified diamine conjugates ( 7a- b, 8a- b) were synthesized and evaluated for cytotoxicity against Melanoma B16, α-difluoromethylornithine (DFMO)-treated B16, spermidine (SPD)-treated B16, Mouse leukemia L1210 and Hela cell lines. Both the DFMO-B16 and SPD-B16 experiments indicated that conjugates 7a- b and 8a- b could recognize the polyamine transporter (PAT) and enter the cells in part or in whole via PAT, although they were not as efficient as the reference, 9-anthracenemethyl homospermidine ( 1).

Apoptotic and autophagic responses to Bcl-2 inhibition and photodamage

Among the cellular responses to photodamage initiated by photodynamic therapy (PDT) are autophagy and apoptosis. While autophagy is a reversible process that can be both a survival and a death pathway, apoptosis is irreversible, leading only to cell death. In this study, we followed the fate of mouse leukemia L1210 cells after photodamage to the endoplasmic reticulum (ER) using a porphycene photosensitizer, where Bcl-2 was among the PDT targets. In wild-type cells, we observed a rapid wave of autophagy, presumed to represent the recycling of some damaged organelles, followed by apoptosis. Using shRNA technology, we created a Bax knockdown line (L1210/Bax(-)). In the latter cell line, we found a marked decrease in apoptosis after photodamage or pharmacologic inactivation of Bcl-2 function, but this did not affect PDT efficacy. Loss of viability was associated with a highly-vacuolated morphology consistent with autophagic cell death. Previous studies indicated pro-survival attributes of autophagy after low-dose PDT, suggesting that autophagy may be responsible for the 'shoulder' on the dose-response curve. It appears that attempts at extensive recycling of damaged organelles are associated with cell death, and that this phenomenon is amplified when apoptosis is suppressed.

Isolation and characterization of a novel protein toxin from fire coral

Fire corals ( Millepora spp.) cause severe pain and inflammatory effects in humans upon contact, and the organs responsible for these effects are called nematocysts. Here, we isolated an active cytotoxin of ca. 18 kDa (MCTx-1) from nematocysts of Millepora dichotoma var. tenera. MCTx-1 was potently cytotoxic (EC 50 value 79 ng/mL) towards L1210 mouse leukemia cells, hemagglutinated a 0.8% suspension of sheep erythrocytes (0.2 μg protein/mL) and was lethal in crayfish (LD 50, 106 μg/kg). We deduced the primary structure of MCTx-1 from the corresponding cDNA sequence and found that MCTx-1 is a novel dermatopontin that is an extracellular matrix protein in mammals. This is the first characterization of a proteinaceous toxin from fire coral.