L1210 Murine Leukemia Cells Research Articles

Designing the Polyamine Pharmacophore: Influence of N-Substituents on the Transport Behavior of Polyamine Conjugates

N-Ethylated N-arylmethyl polyamine conjugates were synthesized and evaluated for their ability to target the polyamine transporter (PAT). To understand the effect of N-ethylation upon PAT selectivity, ethyl groups were appended onto a PAT-selective N (1)-anthracenenylmethyl homospermidine derivative, 1b. Bioevaluation in L1210 murine leukemia cells and in two Chinese hamster ovary cell lines (PAT-active CHO and PAT-deficient CHO-MG) revealed a dramatic decrease in PAT targeting ability upon N (1) or N (5) ethylation of the pharmacophore 1b. Experiments using the amine oxidase inhibitor, aminoguanidine (AG, 2 mM), revealed that the N (9)-ethyl and N (9)-methyl analogues were able to retain their PAT selectivity and cytotoxicity properties in the presence or absence of AG. In contrast, the lead compound 1b (containing a terminal NH 2 group) revealed a dramatic reduction in both its PAT-targeting ability and cytotoxicity in the absence of AG. An improved balance between these three properties of PAT-targeting, cytotoxicity and metabolic stability can be attained via N-methylation at the N (9)-position.

Dynamics of antifolate transport via the reduced folate carrier and the membrane folate receptor in murine leukaemia cells in vitro and in vivo

Murine L1210 leukaemia cells expressing either the reduced folate carrier (RFC) or the membrane folate receptor (MFR) were studied in vitro and in vivo to assess the dynamics of membrane transport of two categories antifolates; folate-based inhibitors of dihydrofolate reductase (methotrexate, edatrexate, aminopterin, PT523, and PT644) and thymidylate synthase (TS) [CB3717, raltitrexed, plevitrexed (BGC9331), pemetrexed and GW1843]. The potency of in situ inhibition of TS was used as an endpoint to analyze the in vitro dynamics of RFC/MFR-membrane transport of these antifolates. Both for L1210-RFC and L1210-MFR cells, the potency of in situ TS inhibition was closely correlated with increasing affinities of these transporters for the antifolates (r = 0.64, P < 0.05 and r = -0.65, P < 0.05, respectively). Within the group of antifolates for which MFR had a low binding affinity, those that had the ability to become polyglutamylated, were more potent inhibitors of TS in situ activity than non-polyglutamatable antifolates. In vivo activity of methotrexate, edatrexate, raltitrexed and pemetrexed was assessed in L1210-RFC and L1210-MFR bearing mice that were fed either a standard or a folate-deficient chow. Dietary folate depletion significantly reduced the MTD for methotrexate (sevenfold), edatrexate (sevenfold), raltitrexed (50-fold) and pemetrexed (150-fold). Based on increased life spans, antitumor effects of methotrexate and edatrexate were markedly better in L1210-RFC bearing mice on the folate-deficient chow (ILS: 455 and 544%, respectively) than on standard chow (ILS: 213 and 263%, respectively). No therapeutic effects of methotrexate and edatrexate were observed for L1210-MFR bearing mice on either chow condition, which may be consistent with the low binding affinity for MFR. Irrespective of the folate diet status, pemetrexed and raltitrexed were inactive against both L1210-RFC and L1210-MFR bearing mice, which may be due to high circulating plasma thymidine levels. Collectively, this study underscores that modulation of dietary folate status can provide a basis within which the therapeutic effect of antifolates may be further improved.

Ester derivatives of gallic acid with potential toxicity toward L1210 leukemia cells

Gallic acid and gallates with the same number of hydroxyl groups and varying the length of the side carbon chain, with respective lipophilicity being defined through the C log P values, were examined for their ability to induce apoptosis (through the DNA ladder fragmentation pattern), mitochondrial and cytoplasmic GSH depletion and NF-κB activation in murine lymphoblastic L1210 leukemia cells. A relationship between cytotoxic effect and a limited degree of lipophilicity was observed.

Nitrogen-Containing Verticillene Diterpenoids from the Taiwanese Soft Coral Cespitularia taeniata

Extensive column chromatography of the ethanolic extract of the soft coral Cespitularia taeniata collected in Taiwan has resulted in the isolation of eight new nitrogen-containing verticillene diterpenes, designated cespitulactams D-K ( 1- 8), together with three known diterpenes, cespitulactams A ( 9) and B ( 10) and cespitularin F. In addition, one new derivative, 6- O-acetylcespitulactam F ( 11), was prepared from compound 3. The structures of these compounds were elucidated on the basis of spectroscopic analyses, especially HRMS and 2D NMR experiments. The cytotoxicity against human oral epidermoid carcinoma (KB) and murine L1210 leukemia cell lines and antimicrobial activities of 1- 8 and 11 were tested and evaluated. A biogenetic pathway for these novel diterpene alkaloids was also proposed.

Encapsulation of platinum(II)-based DNA intercalators within cucurbit[6,7,8]urils

The partial encapsulation of platinum(II)-based DNA intercalators of the type [Pt(5-Cl-phen)(ancillary ligand)](2+), where 5-Cl-phen is 5-chloro-1,10-phenanthroline and the ancillary ligand is ethylenediamine, (1S,2S)-diaminocyclohexane (S,S-dach) or (1R,2R)-diaminocyclohexane, within cucurbit[n]uril (CB[n], where n is 6, 7 or 8) has been examined by (1)H and (195)Pt NMR and mass spectrometry. For CB[7], the molecule encapsulates over the ancillary ligand of all metal complexes, whether this is ethylenediamine or diaminocyclohexane. For CB[8], encapsulation occurs over the sides of the 5-Cl-phen ligand at low [Pt(5-Cl-phen)(S,S-dach)](2+) (5CLSS) to CB[8] ratios (i.e. 0.25:1) but over the ancillary ligand at higher ratios (i.e. 2:1). For CB[6] binding, 5CLSS exhibits both portal and cavity binding, with the ancillary ligand displaying chemical shifts consistent with fast exchange kinetics on the NMR timescale for portal binding and slow exchange kinetics for cavity binding. Binding constants could not be determined using UV-vis, circular dichroism or fluorescence spectrophotometry, but a binding constant for binding of 5CLSS to CB[6] of approximately 10(5) M(-1) was determined using (1)H NMR. Finally, the effect of CB[n] encapsulation on the cytotoxicity of the metal complexes was examined using L1210 murine leukaemia cells in vitro growth inhibition assays. The cytotoxicity is highly dependent on both the metal complex and the CB[n] size, and whilst CB[7] and CB[8] generally decreased cytotoxicity, it was found that CB[6] increased the cyotoxicity of 5CLSS up to 2.5-fold.

E, E, E-1-(4-Arylamino-4-oxo-2-butenoyl)-3,5-bis(arylidene)-4-piperidones: A topographical study of some novel potent cytotoxins

A series of E, E, E-3,5-bis(arylidene)-1-(4-arylamino-4-oxo-2-butenoyl)-4-piperidones 4 (phenylidene) and 5 (4-nitrophenylidene) were prepared in order to explore the structural features of the N-acyl group which affects the cytotoxic potency. Evaluation toward human Molt 4/C8 and CEM T-lymphocytes revealed that many of the IC 50 figures were submicromolar and lower than melphalan. Marked inhibitory potencies toward murine leukemia L1210 cells were also noted. When evaluated against a panel of human tumor cell lines, three representative compounds in series 4 displayed selective toxicity to leukemia and colon cancer cell lines and were significantly more potent than the reference drug melphalan. Molecular modeling of representative compounds in both series 4 and the analogs, in which the configuration of the olefinic double bond was changed from E to Z (series 3), revealed that the torsion angles of the arylidene aryl rings and locations of the terminal arylaminocarbonyl groups may have contributed to the greater cytotoxic properties displayed in 3. Compounds 4c (3,4-dichlorophenylamino), d (4-methylphenylamino) and 5c (3,4-dichlorophenylamino), d (4-methylphenylamino) inhibited the activity of human N-myristoyltransferase by approximately 50% at concentrations of 50–100 μM. The compounds in series 4 and 5 were well tolerated in a short-term toxicity study in mice.

The effect of ancillary ligand chirality and phenanthroline functional group substitution on the cytotoxicity of platinum(II)-based metallointercalators

Fifteen platinum(II)-based metallointercalators have been synthesised that utilise substituted 1,10-phenanthroline (phen) ligands, including 5-chloro-1,10-phenanthroline (5-Cl-phen), 5-methyl-1,10-phenanthroline (5-CH 3-phen), 5-amino-1,10-phenanthroline (5-NH 2-phen), 5-nitro-1,10-phenanthroline (5-NO 2-phen) and dipyrido[3,2- d:2′,3′- f]quinoxaline (dpq), and achiral ethylenediamine (en) and the chiral ancillary ligands 1 S,2 S-diaminocyclohexane ( S, S-dach) and 1 R,2 R-diaminocyclohexane ( R, R-dach). Their cytotoxicity in the L1210 murine leukaemia cell line was determined using growth inhibition assays. The most cytotoxic metal complexes are those that contain S, S-dach ancillary ligands and 5-CH 3-phen intercalating ligands. One metallointercalator [Pt(5-CH 3-phen)( S, S-dach)]Cl 2 ( 5MESS), displays a 5–10-fold increase in cytotoxicity compared to the clinical agent cisplatin. From DNA binding experiments there appears to be no significant difference between any of the metal complexes, indicating that neither DNA binding affinity nor the mode of binding/DNA adduct formed is the sole determinant of the cytotoxicity of this family of platinum(II)-based metallointercalators.

Myriaporones 1−4, Cytotoxic Metabolites from the Mediterranean Bryozoan Myriapora truncata

Four novel polyketide-derived metabolites, myriaporones 1, 2, 3, and 4, have been isolated from the Mediterranean bryozoan Myriapora truncata. Their structures and stereochemistry have been assigned from the analysis of spectroscopic data. The inseparable equilibrium mixture of myriaporones 3 and 4 showed 88% inhibition of L1210 murine leukemia cells at 0.2 microg/mL.

Effects of Melophlins on Colony Formation of Chinese Hamster V79 Cells and IL-8 Production in PMA-stimulated HL-60 Cells

We have recently isolated four new melophlins P (1), Q (2), R (3), and S (4) together with seven known melophlins A (5), D (6), E (7), G (8), H (9), I (10), and O (11) from two marine sponges of the genus Melophlus collected in Palau. In this study, the influence of these compounds on the colony formation of Chinese hamster V79 cells and the production of IL-8 in PMA-stimulated HL-60 cells were examined. These 11 compounds did not show any effect on IL-8 production. The EC50 values of compounds 2, 3, 4, 5, 7, 9, 10, and 11 against V79 cells were 44.0, 13.3, 16.7, 27.2, 19.8, 8.5, 23.1, and 9.6 microM, respectively. The linear-chain-type compounds (1, 6, and 8) were not active against V79 cells at 50 microM. Although the growth inhibitory activity of these melophlins was not remarkable, some structure-activity relationships of these compounds against V79 and murine leukemia L1210 cells were observed.

Vascular targeting of doxorubicin using cationic liposomes

Tumor vessel has been recognized as an important target for anticancer therapy. Cationic liposomes have been shown to selectively target tumor endothelial cells, thus can potentially be used as a carrier for chemotherapy agents. In this study, cationic liposomes containing 20 mol% cationic lipid dimethyl dioctadecyl ammonium bromide (DDAB) and loaded with doxorubicin (DOX) were prepared and characterized. The cationic liposomal DOX showed 10.8 and 9.1 times greater cytotoxicity than control PEGylated liposomal DOX in KB oral carcinoma and L1210 murine lymphocytic leukemia cells, and 7.7- and 6.8-fold greater cytotoxicity compared to control neutral non-PEGylated liposomal DOX, repectively, in these two cell lines. Although cationic liposomal DOX had higher tumor accumulation at 30 min after intravenous administration compared to control liposomes ( p < 0.05), DOX uptake of these liposomes at 24 h post-injection was similar to that of PEGylated liposomal DOX ( p > 0.05) and approximately twice the levels of the free drug and non-PEGylated liposomes. In a murine tumor model generated using L1210 cells, increased survival rate was obtained with cationic liposomal DOX treatment compared to free DOX ( p < 0.01), neutral liposome control ( p < 0.01), as well as PEGylated liposomes ( p < 0.05). In conclusion, the cationic liposomal DOX formulation produced superior in vitro cytotoxicity and in vivo antitumor activity, and warrants further investigation.

Effects of Melophlins on Colony Formation of Chinese Hamster V79 Cells and IL-8 Production in PMA-stimulated HL-60 Cells

We have recently isolated four new melophlins P (1), Q (2), R (3), and S (4) together with seven known melophlins A (5), D (6), E (7), G (8), H (9), I (10), and O (11) from two marine sponges of the genus Melophlus collected in Palau. In this study, the influence of these compounds on the colony formation of Chinese hamster V79 cells and the production of IL-8 in PMA-stimulated HL-60 cells were examined. These 11 compounds did not show any effect on IL-8 production. The EC50 values of compounds 2, 3, 4, 5, 7, 9, 10, and 11 against V79 cells were 44.0, 13.3, 16.7, 27.2, 19.8, 8.5, 23.1, and 9.6 μM, respectively. The linear-chain-type compounds (1, 6, and 8) were not active against V79 cells at 50 μM. Although the growth inhibitory activity of these melophlins was not remarkable, some structure-activity relationships of these compounds against V79 and murine leukemia L1210 cells were observed.

Protein kinase C-alpha antagonizes apoptosis induction by histone deacetylase inhibitors in multidrug resistant leukaemia cells

Previous studies have documented that while several drug-resistant cells enter apoptosis upon treatment with histone deacetylase inhibitors (iHDACs), their drug-sensitive counterparts do not. In the present study, we have investigated at the molecular level why parental drug-sensitive tumor cells do not respond to Trichostatin A and suberoylanilide hydroxamic acid, two iHDACs that promote apoptosis in drug-resistant leukaemia cells. Taking murine leukaemia L1210 cells as a model, we have determined that: (i) PKC-α expression is more elevated in parental L1210 than in drug-resistant L1210/R cells, (ii) activation of PKC neutralizes iHDACs-mediated apoptosis in L1210/R cells, (iii) depletion of PKC in parental L1210 cells results in a positive response to iHDACs-mediated apoptosis, and (iv) transfection of a mutant constitutively active PKC-α form in L1210/R cells makes the cells refractory to apoptosis induction by iHDACs. These results allow us to conclude that activation/high expression of PKC-α protects parental drug-sensitive L1210 cells from iHDACs-mediated apoptosis. Thus, determination of PKC-α levels/activity in leukaemia seems to be relevant when choosing efficient chemotherapy protocols based on the use of apoptosis-inducing anticancer drugs.

Carrier Cell-based Delivery of an Oncolytic Virus Circumvents Antiviral Immunity

Oncolytic viruses capable of tumor-selective replication and cytolysis have shown early promise as cancer therapeutics. However, the host immune system remains a significant obstacle to effective systemic administration of virus in a clinical setting. Here, we demonstrate the severe negative impact of the adaptive immune response on the systemic delivery of oncolytic vesicular stomatitis virus (VSV) in an immune-competent murine tumor model, an effect mediated primarily by the neutralization of injected virions by circulating antibodies. We show that this obstacle can be overcome by administering virus within carrier cells that conceal viral antigen during delivery. Infected cells were delivered to tumor beds and released virus to infect malignant cells while sparing normal tissues. Repeated administration of VSV in carrier cells to animals bearing metastatic tumors greatly improved therapeutic efficacy when compared with naked virion injection. Whole-body molecular imaging revealed that carrier cells derived from solid tumors accumulate primarily in the lungs following intravenous injection, whereas leukemic carriers disseminate extensively throughout the body. Furthermore, xenogeneic cells were equally effective at delivering virus as syngeneic cells. These findings emphasize the importance of establishing cell-based delivery platforms in order to maximize the efficacy of oncolytic therapeutics.

Initiation of apoptosis and autophagy by the Bcl-2 antagonist HA14-1

L1210 murine leukemia cells exposed to an LD 90 concentration of the Bcl-2/Bcl-x L antagonist HA14-1 rapidly undergo apoptosis but also develop numerous intracellular vacuoles with double membranes, exhibit enhanced labeling by monodansylcadaverine, and convert the cytosolic protein LC3-I to LC3-II. These are hallmarks of autophagy. Autophagic vacuoles develop rapidly, preceding the appearance of an apoptotic nuclear morphology and can be observed in both non-apoptotic and apoptotic cells. Inhibition of autophagy by the PI 3-kinase inhibitor wortmannin promoted apoptosis; conversely inhibition of caspase-3/7 with zDEVD-fmk promoted autophagy. Neither process was dependent on calcium translocation. These results indicate that pharmacological suppression of Bcl-2 function can mimic the induction of autophagy that can occur following the down-regulation of Bcl-2 expression by molecular approaches.

Chemopreventive Potential of Flavonoid Extracts from Plantation‐Bred and Wild Aronia melanocarpa (Black Chokeberry) Fruits

ABSTRACT: European plantation‐bred (cultivated) and local Illinois (wild) Aronia melanocarpa (chokeberry) fruits were extracted with 70% aqueous acetone and separated into 6 fractions using vacuum liquid chromatography (VLC) over a Toyopearl (TP) polymer column. TP fractions 2 through 6 were recombined and further subfractionated using silica gel (SG) into 22 subfractions. Crude extract, TP fractions, and SG subfractions were screened in a L1210 murine leukemia cell assay and a human DNA catalytic topoisomerase II assay in order to gauge the cancer chemopreventive potential of each genotype. SG subfraction 6 from the cultivated genotype showed &gt;90% inhibitory activity at 25 μg/mL, and a similar fraction from the wild genotype showed &gt;95% inhibitory activity to L1210 leukemia cells at a concentration of 50 μg/mL. On the basis of topoisomerase inhibition, it can be concluded that all TP fractions of the wild genotype act as catalytic inhibitors. Similar anthocyanins and oligomeric proanthocyanidins were identified from both Aronia genotypes; however, HPLC‐ESI‐MS spectra indicated higher flavonoid concentration in the wild Aronia and a predominance (up to 67%) of nonphenolic compounds in the berries from the cultivated genotype. Both cultivated and wild genotypes exhibited promise toward chemoprevention, but differed in levels of activity in the assays used to determine chemoprotective potential.

Polyamide Platinum Anticancer Complexes Designed to Target Specific DNA Sequences

Two new platinum complexes, trans-chlorodiammine[N-(2-aminoethyl)-4-[4-(N-methylimidazole-2-carboxamido)-N-methylpyrrole-2-carboxamido]-N-methylpyrrole-2-carboxamide]platinum(II) chloride (DJ1953-2) and trans-chlorodiammine[N-(6-aminohexyl)-4-[4-(N-methylimidazole-2-carboxamido)-N-methylpyrrole-2-carboxamido]-N-methylpyrrole-2-carboxamide]platinum(II) chloride (DJ1953-6) have been synthesized as proof-of-concept molecules in the design of agents that can specifically target genes in DNA. Coordinate covalent binding to DNA was demonstrated with electrospray ionization mass spectrometry. Using circular dichroism, these complexes were found to show greater DNA binding affinity to the target sequence: d(CATTGTCAGAC)(2), than toward either d(GTCTGTCAATG)(2,) which contains different flanking sequences, or d(CATTGAGAGAC)(2), which contains a double base pair mismatch sequence. DJ1953-2 unwinds the DNA helix by around 13 degrees , but neither metal complex significantly affects the DNA melting temperature. Unlike simple DNA minor groove binders, DJ1953-2 is able to inhibit, in vitro, RNA synthesis. The cytotoxicity of both metal complexes in the L1210 murine leukaemia cell line was also determined, with DJ1953-6 (34 microM) more active than DJ1953-2 (>50 microM). These results demonstrate the potential of polyamide platinum complexes and provide the structural basis for designer agents that are able to recognize biologically relevant sequences and prevent DNA transcription and replication.

Synthesis and Cytotoxic Activity of Acronycine Analogues in the Benzo[c]pyrano[3,2‐h]acridin‐7‐one and Naphtho[1,2‐b][1,7] and ‐[1,10]‐phenanthrolin‐7(14H)‐one Series.

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Initiation of apoptosis and autophagy by photodynamic therapy

This study was designed to examine modes of cell death after photodynamic therapy (PDT). Murine leukemia L1210 cells and human prostate Bax-deficient DU145 cells were examined after PDT-induced photodamage to the endoplasmic reticulum (ER). Phase contrast, fluorescence and electron microscopy were used to identify changes in cellular morphology, chromatin condensation, loss of mitochondrial membrane potential, and formation of phagolysosomes. Western blots were used to assess the processing of LC3-I to LC3-II, a marker for autophagy. Inhibitors of apoptosis and/or autophagy were used to delineate the contributions of the two pathways to the effects of PDT. Both apoptosis and autophagy occurred in L1210 after ER photodamage with the latter predominating after 24 hours. In DU145 cells, PDT conditions causing comparable cytotoxicity only initiated autophagy. PI3-kinase inhibitors suppressed autophagy in both cell lines as indicated by inhibition of vacuolization and LC3 processing. Both autophagy and apoptosis were observed in L1210 cells following ER photodamage. In the Bax-deficient DU145 cell line only autophagy was observed. Current information suggests that autophagy can function as either a survival or death pathway. We propose that in the context of PDT, this may also be true.

Ceramide accumulation after photosensitization is absent after the Bcl‐2 inhibitor HA 14‐1

The oxidative stress initiated by photodynamic therapy (PDT) results in accumulation of ceramide in various cell types undergoing apoptosis. Apoptotic responses to PDT are similar to those of the oxidative stress inducer and the Bcl-2 inhibitor HA 14-1 in murine leukemia L1210 cells. Here we tested whether de novo ceramide accumulation can be induced by HA 14–1 during apoptosis in Jurkat T human leukemia cells. Similar to photosensitization with Pc 4, treatment of Jurkat cells with HA 14–1 leads to DEVDase activation and nuclear apoptosis. However, unlike Pc 4-PDT, HA 14–1 did not induce accumulation of de novo ceramide. The data suggest that, compared to HA 14–1, de novo ceramide accumulation is a distinct response to PDT in Jurkat cells.

Novel (S)-(-)- and R-(+)-seco-iso-cyclopropylfurano[e]indoline-5,6,7- trimethoxyindole-2-carboxamide (iso-CFI) Analogs of Duocarmycin C2: Synthesis and Biological Evaluation

Racemic seco-iso-CFI (cyclopropylfurano[e]indoline) analogs of the duocarmycins and CC-1065 have recently been reported by our group. These compounds covalently react with AT-rich sequences of DNA, and they exhibit potent cytotoxicity against cancer cells but are less toxic to normal bone marrow cells. This article details the synthesis of enantiomerically pure (S)-(-)- and R-(+)-seco-iso-CFI (cyclopropylfurano[e]indoline)-5,6,7-trimethoxyindole-2-carboxamide analogs, (S)-(-)-1 and (R)-(+)-1, respectively. The covalent DNA binding properties and cytotoxicity of both enantiomers against L1210 murine leukemia and B16 murine melanoma cells grown in culture are reported and compared to racemate (+/-)-1. The natural (S)-(-)-enantiomer of 1 is more reactive with DNA and more cytotoxic than its unnatural mirror image and the racemic mixture.