Induction of New Antigenic Properties on Dtic-Treated L1210 Clones

In vivo treatment of mouse leukemia L1210 with DTIC can induce new antigens on tumor cells that are not detectable on parental cells and that are transmissible as a genetic character. Moreover, L1210/DTIC is rejected by syngeneic hosts. The aim of this study was to investigate whether DTIC selects pre-existing immunogenic clones rather than inducing ex novo new antigenic determinants and to verify the number of induced antigens. L1210 leukemia was cloned in vitro and 4 clones were treated in vivo with DTIC. All the treated clones displayed antigenic properties since they were rejected by syngeneic hosts. Cytotoxic T lymphocytes (CTL) activated against one DTIC clone could recognize and lyse the relevant target. One of these DTIC-modified clones (L4/DTIC) was recloned and the subclones were tested in vivo and in vitro. Two out of six subclones were rejected by syngeneic hosts. CTL specific against these two clones were able to recognize and lyse all the other clones to different degrees. The degree of suscptibility to lysis did not correlate with the capability to evoke an immune response in vivo. Based on these findings we conclude that DTIC does not select pre-existing clones but modifies the tumor cells antigenically, and that the antigenicity induced by DTIC in a cloned tumor line is due to the presence of common antigens shared to different degrees with treated cells.

L-1210 and human acute leukemia kinetics as related to therapy

Comparative considerations are made between human acute leukemia (AL) and mouse transplantable L-1210 leukemia. The main kinetic parameters, such as the growth fraction (GF), growth rate, and cell cycle times, of both human and mouse diseases, are compared. The striking differences in cell kinetics and in response to treatment may be viewed as depending on different leukemogenesis mechanisms. Therefore, some improvement in human AL chemotherapy is considered possible both by researching a more rational employment of cytostatic drugs, and studying other animal models quite similar to the human disease, such as AKR leukemia.

Heterogeneity of tumor cell populations

Ascites tumor cell populations proved to be heterogeneous with respect to density. Subpopulations separated by isopycnic centrifugation differed from each other in several respects including cell cycle time, chromosome number and distribution and chemotherapeutic sensitivity. The results indicate that density separation is a useful technique to study the behavior of subpopulations within tumor and offers new possibilities in comparative experimental chemotherapy.

Cytotoxic α-Pyrones from Xylaria hypoxylon

Two new α-pyrone derivatives, xylarone (1) and 8,9-dehydroxylarone (2) possessing cytotoxic activities, were isolated from the culture fluid of submerged cultures of the ascomycete Xylaria hypoxylon, strain A27-94. Their structures were elucidated by spectroscopic methods.

Identification and characterization of a 66-68-kDa protein as a methotrexate-binding protein in murine leukemia L1210 cells

We previously observed an unidentified, tyrosine-phosphorylated, membrane-associated, 66-68-kDa protein which was present in the L1210 murine leukemia cells but not present, at least in the tyrosine-phosphorylated form, in cisplatin-methotrexate (CDDP-MTX) cross-resistant L1210/DDP cells. We purified and characterized this 66-68-kDa protein by affinity chromatography purification using its two identified properties, tyrosine phosphorylation and MTX-binding, and yielded a single band of 66-68 kDa. The purified protein was subjected to trypsin digestion and the isolated peptide fragments were sequenced and yielded two partial peptide sequences: VEIIANDQ and VTNAVVTVPAYFNDSQRQA. The two peptide sequences were used to search for the mouse genome at the national center for biotechnology information (NCBI) database for Open Reading Frame Sequence (ORFs) containing these peptides using the TBLASTN function. A single gene was identified containing both sequences, the HSPa8 gene, which codes for the heat shock family protein, HSC70. We further demonstrated that HSC70 is a MTX-binding protein using a binding assay with MTX-agarose beads followed by Western blotting. The HSC70 also existed in various cancer cell lines and showed binding to MTX. Additionally, the HSC70 protein, cloned from the L1210 murine leukemia cells, was expressed and purified from E. coli cells using a polyhistidine-tag purification system and it also showed the binding properties with MTX. DnaK, the HSC70 homologue in E. coli, also binds to MTX. By using the purified truncated HSC70 domains, we identified the adenosine triphosphatase (ATPase) domain of HSC70 that can bind to MTX. Thus, we have tentatively characterized a new, novel property of HSC70 as a MTX-binding protein.

Antitumor effects of synthetic 6,7-annulated-4-substituted indole compounds in L1210 leukemic cells in vitro

BACKGROUND

Because annulated indoles have almost no representation in the PubChem or MLSMR databases, an unprecedented class of an indole-based library was constructed, using the indole aryne methodology, and screened for antitumor activity. Sixty-six novel 6,7-annulated-4-substituted indole compounds were synthesized, using a strategic combination of 6,7-indolyne cycloaddition and cross-coupling reactions under both Suzuki-Miyaura and Buchwald-Hartwig conditions, and tested for their effectiveness against murine L1210 tumor cell proliferation in vitro.

MATERIALS AND METHODS

Various markers of tumor cell metabolism, DNA degradation, mitotic disruption, cytokinesis and apoptosis were assayed in vitro to evaluate drug cytotoxicity.

RESULTS

Most compounds inhibited the metabolic activity of leukemic cells in a time- and concentration-dependent manner but only 9 of them were sufficiently potent to inhibit L1210 tumor cell proliferation by 50% in the low-μM range after 2 (IC(50): 4.5-20.4 μM) and 4 days (0.5-4.0 μM) in culture. However, the antiproliferative compounds that were the most effective at day 4 were not necessarily the most potent at day 2, suggesting different speeds of action. A 3-h treatment with antiproliferative annulated indole was sufficient to inhibit, in a concentration-dependent manner, the rate of DNA synthesis measured in L1210 cells over a 0.5-h period of pulse-labeling with (3)H-thymidine. Four of the antiproliferative compounds had weak DNA-binding activities but one compound reduced the fluorescence of the ethidium bromide-DNA complex by up to 53%, suggesting that some annulated indoles might directly interact with double-stranded DNA to disrupt its integrity and prevent the dye from intercalating into DNA base pairs. However, all 9 antiproliferative compounds induced DNA cleavage at 24 h in L1210 cells, containing (3)H-thymidine-prelabeled DNA, suggesting that these antitumor annulated indoles might trigger an apoptotic pathway of DNA fragmentation. Indeed the antiproliferative annulated indoles caused a time-dependent increase of caspase-3 activity with a peak at 6 h. Interestingly, the compounds with the most potent antiproliferative IC(50) values at day 2 were consistently the most effective at inhibiting DNA synthesis at 3 h and inducing DNA fragmentation at 24 h. After 24-48 h, antiproliferative concentrations of annulated indoles increased the mitotic index of L1210 cells and stimulated the formation of many bi-nucleated cells, multi-nucleated cells, apoptotic cells and micronuclei, suggesting that these antitumor compounds might enhance mitotic abnormality, induce chromosomal damage or missegregation, and block cytokinesis to induce apoptosis.

CONCLUSION

Although annulated indoles may have interesting bioactivity, novel derivatives with different substitutions must be synthesized to elucidate structure-activity relationships, identify more potent antitumor lead compounds, and investigate their molecular targets and mechanisms of action.

[Part IV. Synthesis and antitumor evaluation of s-triazolothiadiazines and pyrazolo s-triazoles derived from ciproxacin]

An efficient modified route based on the targeting mechanism of antibacterial fluoroquinolones for the shift from the antibacterial activity to the antitumor one was further developed. Using a fused heterocyclic ring, s-triazolothiadiazine as a carboxyl bioisostere of ciprofloxacin, the title compounds, 1-cyclopropyl-6-fluoro-7-piperazin-1-yl-3-(6-substituted-phenyl-7H-[1, 2, 4]triazolo[3, 4-b][1, 3, 4]thiadiazin-3-yl)-quinolin-4(1H)-ones (5a-5e) and their corresponding N-acetyl products (6a-6e), were designed and synthesized, separately. Meaningfully, a ring-contraction of fused six-membered thiadiazine occurred by a sulfur extrusion reaction gave new tri-acetylated fused heterocycles related to pyrazolo[5, 1-c][1, 2, 4] triazoles (7a-7e). The in vitro antitumor activity against L1210, CHO and HL60 cell lines was also evaluated for the synthesized fifteen heterocycles compared to parent ciprofloxacin by methylthiazole trazolium (MTT) assay. Interestingly, the results displayed that fifteen fused heterocyclic compounds showed more significant growth inhibitory activity (IC50 < 25.0 micromo x L(-1)) than that of parent ciprofloxacin (IC50 > 150.0 micromol x L(-1)), and the active order decreased from 7a-7e to 5a-5e to 6a-6e, respective.

Bioactivity of synthetic 2-halo-3-aryl-4(3H)-quinazoliniminium halides in L1210 leukemia and SK-BR-3 mammary tumor cells in vitro

BACKGROUND

Because quinazolines and their derivatives exhibit a wide range of pharmacological profiles, there is a continuous interest among synthetic and medicinal chemists in the discovery of more potent analogs. Ten novel quinazoliniminium salts were synthesized and tested for their effectiveness against murine and human tumor cell proliferation in vitro.

MATERIALS AND METHODS

Various markers of tumor cell metabolism, DNA degradation and mitotic disruption were assayed in vitro to evaluate drug cytotoxicity.

RESULTS

All compounds induced concentration- and time-dependent antitumor effects in vitro but the 2-chloro-3-(4-methoxyphenyl)quinazolin-4(3H)-iminium chloride (4) was the most effective inhibitor of leukemia L1210 cell proliferation at days 2-4 (IC50: 2.1-0.9 μM), suggesting that the para-methoxyphenyl substituent on the N3 of 4 may enhance the antiproliferative properties of the quinazoliniminium scaffold. In mammary SK-BR-3 tumor cells, 4 reduced the Ki-67 marker of cell proliferation at 24 h and the metabolic activity at days 2 and 4. Moreover, a 1.5- or 3-h treatment with 4 was sufficient to inhibit the rates of DNA, RNA and protein syntheses measured in L1210 cells over 0.5- or 1-h periods of pulse-labeling with 3H-thymidine, 3H-uridine and 3H-leucine, respectively. As 4 did not reduce the fluorescence of the ethidium bromide-DNA complex, this compound was unlikely to directly bind to or destabilize double-stranded DNA. However, 4 induced DNA cleavage at 24 h in L1210 cells containing 3H-thymidine-prelabeled DNA, suggesting that this antitumor drug might trigger an apoptotic pathway of DNA fragmentation. After 12-48 h, 4 weakly increased the mitotic index of L1210 cells but stimulated the formation of many binucleated cells, multinucleated cells and micronuclei, suggesting that this antitumor compound might enhance mitotic abnormality, induce chromosomal damage or missegregation, and block cytokinesis.

CONCLUSION

Although 4 may have interesting bioactivity, more compounds based on the quinazoliniminium scaffold must be synthesized to elucidate structure-activity relationships, identify more potent antitumor lead compounds, and investigate their molecular targets and mechanisms of action.

[Heterogeneity of cell population of lymphoma NK/Ly and leukemia L-1210 according to carbohydrate structure of cell surface: immunocytochemical analysis of lectin binding]

The heterogeneity of tumor cell populations according to binding of lectins from lentil (LcL), wheat germs (WGA), peanut (PNA) and concanavalin A was investigated on a model of murine Nemeth-Kellner lymphoma (NK/Ly) and leukemia L-1210. Bound lectins were detected by indirect immunochemical method using home obtained polyclonal antilectin antibodies and immunogold silver staining (IGSS) technique. Significant differences in binding of Con A were revealed between NK/Ly (67% Con A+) and L-1210 (7.2% Con A+) cells, while the differences in binding of other lectins with both types of tumor cells were not significant. A relatively high percentage of PNA+ cells was registered that can indicate a high degree of desialization of membrane glycoproteins.

Cytotoxicity and antileukaemic activity of new duplexes linking 3-C-ethynylcytidine and 5-fluorodeoxyuridine

The cytotoxic and antineoplastic potential of two new duplex drugs, ECyd-5-FdU and ECyd- lipid- 5-FdU, were compared with the activity of the parent single-nucleoside analogues, 3-C-ethynylcytidine (ECyd) and 5-fluorodeoxyuridine (5-FdU), either applied as monotherapy or simultaneously in equimolar concentrations simulating their ratio in a duplex drug. Murine leukaemia L1210 cells were used for comparative in vitro tests of the duplex and the single drugs. The tested substances were evaluated for their cytotoxicity, combinatory potential and revitalisation properties. Additionally, an in vivo model of leukaemia L1210-bearing mice of the DBA/2J strain was used for testing of acute toxicity and antileukaemic activity using various chemotherapeutic regimes. Based on the results of this study, the suitability of ECyd and 5-FdU for forming a duplex drug was discussed from the perspective of their expected synergistic anticancer activities. We found an improvement of chemotherapy outcomes of the new duplex drugs tested by comparing their in vitro cytotoxicity and an increase of the time of survival of experimental leukaemia-bearing mice in a statistically significant manner.

[Suppressive effect of gypenosides on murine leukemia L1210 cell lines]

OBJECTIVE

To investigate the suppressive effect of gypenosides (Gyp) on murine leukemia L1210 cells.

METHODS

The growth inhabitation of murine leukemia L1210 cell was detected by MT assay. The production of reactive oxygen species and the change of mitochondrial membrane potential were detected by flow cytometry. The change of nuclear and DNA damage of murine leukemia L1210 cells were detected by DAPI staining and single cell gel electrophoresis.

RESULTS

Gyp (100-500 microg/mL) inhibited the growth of murine leukemia L1210 cells. The concentration of Gyp (350 microg/mL) treated murine leukemia L1210 cells at different time points, the mitochondrial membrane potential decrease obviously. L1210 cells were treated with Gyp (350 microg/mL) for 4 h, the highest production of reactive oxygen species was induced. DNA damage were detected after Gyp (350 microg/mL) treated for 4, 12, 24 h. The change of nuclear was treated by Gyp (350 microg/mL) with time-dependent.

CONCLUSION

Gypenosides has effects on cell viability, induce reactive oxygen species and decreases mitochondrial membrane potential, and can induce morphological changes and DNA damage.

Part II: Design, synthesis and antitumor action of C3/C3 bisfluoroquinolones linked-cross 2, 5-[1, 3, 4]oxadiazole

To develop a new small molecular probe for discovering an antitumor lead compound from the replacement of carboxylic group of two molecular antibacterial fluoroquinolones with a heterocyclic ring, a series of the C3/C3 bis-fluoroquinolones tethered with an 1, 3, 4-oxadiazole ring were synthesized as their respective HCl salts, and their structures were characterized by elemental analysis and spectral data. The in vitro antitumor activity against L1210, CHO and HL60 cell lines was also evaluated via the respective IC50 values by methylthiazole trazolium (MTT) assay.

[The lysosomal cathepsins B, L and D in development of murine experimental leukemias]

Lysosomal proteases are actively involved in pathogenesis of cancer progression. Alterations in proteases and their inhibitors interaction were suggested to be implicated in the processes of tumor invasion and metastasis. Among proteases connected with malignant growth, cysteine cathepsins B and L and aspartic cathepsin D play the main role in the tumor development. The present study was designed to investigate activity of cathepsins B, L and D activity in the development and treatment of murine experimental leukemias and to determine the correlation of these proteases with tumor malignancy and the chemotherapy effect. P-388 leukemia was characterized by a more aggressive development and unfavorable prognosis than L1210/1 leukemia. The activity of cathepsins B, L and D in tumor tissues of mice infected with P-388 leukemia, as well as in liver and spleen and the activity of cathepsins B and L in serum were lower than their activity in mice infected with L1210/1 leukemia. Changes of cathepsin activity in liver and spleen of mice with leukemias have demonstrated a level of aggressiveness of tumor development and invasion of liver and spleen by neoplastic cells. The treatment resulted in the increase of cathepsin B, L and D activities in tumor tissue, liver, spleen and cathepsin B and L activities in serum. The highest activity of proteases was revealed in the groups of mice characterized by the greatest suppression of tumor growth. These data have shown that lysosomal proteases are involved in progression of murine experimental leukemias and elimination of tumor cells in the result of treatment. Determination of the activity of cysteine and aspartic proteases can be used for evaluation of cancer diseases malignancy, their sensitivity for chemotherapy and efficiency of treatment.

Cytotoxicity and inhibitory properties against topoisomerase II of doxorubicin and its formamidine derivatives

This work was undertaken to compare cytotoxicity, DNA damaging properties and effect on DNA cleavage by topoisomerase II of the anthracycline drug doxorubicin (DOX) and its two derivatives with a formamidino group containing a cyclic amine moiety such as morpholine (DOXM) or hexamethyleneimine (DOXH). The tetrazolium dye colorimetric assay was used to determine the cytotoxic activity of anthracyclines toward L1210 leukemia cells. DNA damage was measured by alkaline elution technique. The effect of anthracyclines on DNA cleavage was studied in a cell-free system containing supercoiled pBR322 DNA and purified human topoisomerase II. The cytotoxicity data and the results of studies on the mechanism of DNA break formation by anthracyclines at the cellular level and in the cell-free system showed that the presence of the formamidino group in the doxorubicin molecule reduced its ability to stimulate DNA cleavage by DNA topoisomerase II.

CONCLUSION

DNA topoisomerase II is not a primary cellular target for DOXM or DOXH. An advantageous feature of formamidinoanthracyclines is their mechanism of cytotoxic action which is not related to the inhibition of DNA topoisomerase II. Therefore this class of anthracyclines seems to be a good source for selection of an anticancer drug directed toward cancer cells with the developed multidrug resistance attributed to the presence of altered DNA topoisomerase II.

[Synthesis and antitumor activity of C3 heterocyclic-substituted fluoroquinolone derivatives (I): ciprofloxacin aminothiodiazole Schiff-bases]

To discover a novel antitumor lead compound derived from fluoroquinolone, C3 carboxyl group of ciprofloxacin (1) was replaced with heterocyclic ring to form cyclopropyl fluoroquinolone aminothiadiazole scaffold (2), then reacted with aromatic aldehydes to give the Schiff bases compounds (3a-3j). The structures of new compounds were characterized by element analysis and spectral data, and their in vitro antitumor activity against SMMC-7721, HL60 and L1210 cell lines was evaluated by MTT assay via the respective IC50 values. The bioactive assay showed that eleven thiadiazole-substituted ciprofloxacin derivatives displayed potential cytotoxicity against the tested cancer cell lines, where the IC50 values of compounds 3d and 3f reached micromolar concentration. Therefore, the C3 carboxyl group of fluoroquinolone is not necessary to antitumor activity. Functionally modified heterocycle-substituted fluoroquinolone as potent antitumor lead compound is valuable for further study.

Synthesis and Cytotoxic Activity of Thiazolofluorenone Derivatives

The synthesis and biological evaluation of some novel thiazolofluorenones, thiazolofluorenes and thiazoloanthraquinones, substituted with amino side-chains are described. These polyheterocyclic compounds have been synthesized via the corresponding imino-1,2,3-dithiazoles. Their cytotoxic activity and their eventual selective effect on a phase of the cell cycle were evaluated in vitro, using the murine lymphocytic L1210 leukaemia cell line.

Potential antioxidant activity, cytotoxic and apoptosis-inducing effects of Chelidonium majus L. extract on leukemia cells

OBJECTIVES

The purpose of this study was to assess whether a methanol extract isolated from the greater celandine Chelidonium majus L. (CME) had antioxidant effect and was able to inhibit proliferation and to induce apoptosis in leukemia cells in vitro.

METHODS

The potential antioxidant activity of CME was proved by the 1,1-diphenyl- 2-picrylhydrazyl (DPPH) radical scavenging assay. The cytotoxicity of CME was measured by the cell growth inhibition assay using murine leukemia L1210 cell line and human promyelocytic HL-60 leukemia cells. Apoptosis-inducing effect was determined by fluorescence microscopy (chromatin condensation and nuclear DNA fragmentation).

RESULTS

In the DPPH assay CME acted as a scavenger of DPPH free radical. The results on antiproliferative properties assessment clearly demonstrated that CME had a cytotoxic effect towards both leukemia cell lines in a dose-dependent manner. In addition, the human promyelocytic HL-60 cells were more sensitive to CME treatment than the L1210 cells.

CONCLUSIONS

We concluded that the extract of C. majus L. had a strong antioxidant potential and exerted the antiproliferative activity via apoptosis on leukemia cells. CME due to the presence of the isoquinoline alkaloids and the flavonoid components may play an important role in both cancer chemoprevention through its antioxidant activity and modern cancer chemotherapy as cytotoxic and apoptosis-inducing agent.

Overexpression of P-glycoprotein in L1210/VCR cells is associated with changes in several endoplasmic reticulum proteins that may be partially responsible for the lack of thapsigargin sensitivity

L1210/VCR cells, which express an abundant amount of P-glycoprotein (P-gp), were found to be resistant to thapsigargin--an inhibitor of sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA). In the current paper, we have studied the possible differences among L1210 and L1210/VCR cells in expression of endoplasmic reticulum proteins involved in the regulation of calcium homeostasis and calcium-dependent processes. Amounts of mRNA encoding both calcium release channels (ryanodine receptor channels--RyR and IP3-receptor channels--IP3R) were found to be at similar levels in sensitive and resistant cells. However, mRNAs encoding IP3R1 or 2 were decreased in resistant cells cultivated in the presence of VCR (1.08 micromol/l), while mRNA encoding RyR remained unchanged. The amount of mRNA for SERCA2 was decreased in resistant cells when compared with sensitive cells. This decrease was more pronounced when resistant cells were cultivated in the presence of vincristine (VCR). Calnexin was found to be less expressed at the protein level in resistant as in sensitive cells. The level of mRNA encoding calnexin was decreased only when resistant cells were cultivated in the presence of VCR. Calnexin was found to be associated with immature P-gp in resistant cells. Thus, differences exist between sensitive and resistant cells in the expression of endoplasmic reticulum proteins involved in the control of intracellular calcium homeostasis or calcium-dependent processes. These changes may be at least partially responsible for the lack of sensitivity of resistant cells to thapsigargin.

Petiolins A-C, phloroglucinol derivatives from Hypericum pseudopetiolatum var. kiusianum

Two new phloroglucinol derivatives possessing chromane skeleton, petiolins A (1) and B (2), and a new phloroglucinol derivative containing a dihydrofuran ring, petiolin C (3), were isolated from aerial parts of Hypericum pseudopetiolatum var. kiusianum. The gross structures of 1-3 were elucidated by spectroscopic data, and the relative stereochemistry of 3 was elucidated by NOESY data. Petiolins A-C (1-3) showed modest cytotoxicity, while petiolin C (3) exhibited antifungal activity.

Design, synthesis and antiproliferative activity of some 3-benzylidene-2,3-dihydro-1-benzopyran-4-ones which display selective toxicity for malignant cells

A series of 3-benzylidene-4-chromanones 1a-l were prepared and their cytotoxicity towards human Molt 4/C8 and CEM T-lymphocytes as well as murine L1210 lymphoid leukemia cells were compared to the previously generated biodata in these three assays for the isosteric 2-benzylidene-1-tetralones 2a-l. Over 40% of the compounds in series 1 were more potent than their counterparts in series 2, while equipotency was noted in one-third of the comparisons made. In general the IC(50) values of 1a-l towards the human T-lymphocytes were in the low micromolar range. Molecular modelling revealed differences in shapes of representative molecules in series 1 and 2 which may contribute to the variation in cytotoxic potencies. Most of the compounds in series 1 displayed greater potencies towards HSC-2, HSC-3, HSC-4 and HL-60 neoplasms than HGF, HPC, and HPLF normal cells and were well tolerated in mice.

[Synthesis and antitumor activity of anthracene-9-carbaldehyde amino-s-triazole Schiff-bases with side-chain of S-acetic acid]

To find out a novel lead compound from heterocyclic amine Schiff bases for developing new antitumor agents, each of (4-amino-5-substituted-s-triazol-3-ylthio) -acetic acids 2a-j was condensed with anthracene-9-carbaldehyde to obtain Schiff-bases of [4-(anthracen-9-yl methylene) amino] -5-substituted-s-triazol-3-ylsulfanyl] -acetic acids 3a-j. The structures of new compounds synthesized were characterized by elemental analysis and spectral data, and in vitro antitumor activity was also evaluated against CHO, HL60 and L1210 cell lines by MTT assay.

A new nanomedicine of gemcitabine displays enhanced anticancer activity in sensitive and resistant leukemia types

Gemcitabine is an anticancer nucleoside analogue active against various solid tumors. However, it possesses important drawbacks like a poor biological half-life and the induction of resistance. With the objective of overcoming the above drawbacks, we designed a new nanomedicine of gemcitabine and studied its anticancer efficacy against leukemia at preclinic. Gemcitabine has been covalently coupled with 1,1',2-tris-nor-squalenic acid to obtain the new anticancer nanomedicine 4-(N)-Tris-nor-squalenoyl-gemcitabine (SQdFdC NA). The SQdFdC NA exhibited, in comparison to gemcitabine, 3.26- and 3.22-folds higher cytotoxicity respectively, in murine resistant leukemia L1210 10K cells and in human leukemia resistant cell line CEM/ARAC8C. Following intravenous treatment of murine aggressive metastatic leukemia L1210 wt bearing mice, the SQdFdC NA caused significant increase in survival time compared to gemcitabine and also led to long-term survivals, which was not the case after gemcitabine treatment. This was attributed to significantly higher deposition of SQdFdC NA in spleen and liver (P<0.05), the major metastatic organs. In comparison to gemcitabine, SQdFdC NA displayed greater ability to induce S-phase arrest of the cancer cells followed by increased apoptotic induction. Interestingly, like gemcitabine, SQdFdC NA didn't induce appreciable differences in blood parameters even at doses higher than those used for anticancer evaluation. The preclinical data obtained in vitro and in vivo with SQdFdC NA demonstrate that this nanomedicine represents a new therapeutic system for the effective treatment of leukemia.

[Apoptosis-inducing effect of alternol on mouse lymphocyte leukemia cells and its mechanism]

Alternol is purified from fermentation productions of microorganisms named as Alternaria alternata var. monosporus. The research is to investigate the apoptosis-inducing effect of alternol on mouse lymphocyte leukemia (L1210) cells and the possible mechanisms. MTT method was used to evaluate the viability of L1210 cells. Apoptosis of L1210 cells was detected by morphological assessment, DNA electrophoresis assay and flow cytometry. Western blotting analysis was carried out to determine the apoptosis-related proteins. Proliferation inhibition of L1210 cells by alternol was found remarkably in a dose-dependent manner. When treated with alternol, apoptotic morphological features of L1210 cells were observed by fluorescent microscopy (AO/EB) and the apoptosis rate was also elevated in a time-dependent manner. After treatments with various concentrations of alternol for 48 h, DNA laddering appeared. The increase of reactive oxygen species (ROS) production was found after cells were exposed to alternol for 6 h, while the decrease of mitochondrial transmembrane potential (delta psi m) was not found until cells were exposed to alternol for 24 h. Furthermore, the level of Bcel-2 and Bcl-2/Bax was down-regulated, while the level of caspase-3 and caspase-9 but not caspase-8 was up-regulated when alternol was added for 72 h. In summary, the results suggested that alternol could inhibit the proliferation of L1210 cells and induce apoptosis of L1210 cells, which was mediated by mitochondria-dependent pathway.

Alternol inhibits proliferation and induces apoptosis in mouse lymphocyte leukemia (L1210) cells

Alternol is a novel compound purified from the fermenting products by microorganisms named as Alternaria alternata var. monosporus from the bark of Yew. In this study, we tested its effect on mouse lymphocyte leukemia L1210 cells. Alternol was found to inhibit the proliferation and induce apoptosis in L1210 cells. When the cells were treated with Alternol, chromatin condensation and phosphatidylserine externalization were observed with the down-regulation of the pro-survival gene Bcl-2 and the activation of caspase-3, caspase-9, but not caspase-8. Moreover, exposure of cells to Alternol resulted in a significant increase in reactive oxygen species (ROS) and mitochondrial transmembrane potential (DeltaPsim) depolarization. Taken together, these results demonstrate that Alternol is a potent agent in inducing L1210 cells to apoptosis, which involve caspase activation and ROS generation.

Unique contrast patterns from resonance-enhanced chiral SHG of cell membranes

Chirality can produce novel nonlinear optical effects that may form the basis for new imaging contrast agents. In this paper, we developed a new chiral chromophore 2, which is the dimer of a known voltage sensitive dye, monomer 1, with the chirality originating from the twisted orientation between two subunits. Racemic dimer and monomer 1 were used as the references to study the effect of chirality in SHG microscopy of live cells. All these dyes selectively stain the outer leaflets of cell membranes, producing strong resonance-enhanced SHG images. At the symmetric junction between two adherent cells, monomer or racemic dimer SHG is forbidden due to centrosymmetry, and indeed little SHG was observed (10 +/- 1% relative to nonjunction). When stained with the chiral dimer, the junction is no longer centrosymmetric and much stronger SHG was observed (39 +/- 4% relative to nonjunction). Plane polarized light produces highly polarized images of spherical cells stained with racemic dye, but for the chiral dye, the polarized pattern is largely eliminated by the chiral SHG emanating from the subresolution membrane convolutions.

In vivo quantitation of rare circulating tumor cells by multiphoton intravital flow cytometry

Quantitation of circulating tumor cells (CTCs) constitutes an emerging tool for the diagnosis and staging of cancer, assessment of response to therapy, and evaluation of residual disease after surgery. Unfortunately, no existing technology has the sensitivity to measure the low numbers of tumor cells (<1 CTC per ml of whole blood) that characterize minimal levels of disease. We present a method, intravital flow cytometry, that noninvasively counts rare CTCs in vivo as they flow through the peripheral vasculature. The method involves i.v. injection of a tumor-specific fluorescent ligand followed by multiphoton fluorescence imaging of superficial blood vessels to quantitate the flowing CTCs. Studies in mice with metastatic tumors demonstrate that CTCs can be quantitated weeks before metastatic disease is detected by other means. Analysis of whole blood samples from cancer patients further establishes that human CTCs can be selectively labeled and quantitated when present at approximately 2 CTCs per ml, opening opportunities for earlier assessment of metastatic disease.

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 24h 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.

ANN-QSAR model for selection of anticancer leads from structurally heterogeneous series of compounds

Developing a model for predicting anticancer activity of any classes of organic compounds based on molecular structure is very important goal for medicinal chemist. Different molecular descriptors can be used to solve this problem. Stochastic molecular descriptors so-called the MARCH-INSIDE approach, shown to be very successful in drug design. Nevertheless, the structural diversity of compounds is so vast that we may need non-linear models such as artificial neural networks (ANN) instead of linear ones. SmartMLP-ANN analysis used to model the anticancer activity of organic compounds has shown high average accuracy of 93.79% (train performance) and predictability of 90.88% (validation performance) for the 8:3-MLP topology with different training and predicting series. This ANN model favourably compares with respect to a previous linear discriminant analysis (LDA) model [H. González-Díaz et al., J. Mol. Model 9 (2003) 395] that showed only 80.49% of accuracy and 79.34% of predictability. The present SmartMLP approach employed shorter training times of only 10h while previous models give accuracies of 70-89% only after 25-46 h of training. In order to illustrate the practical use of the model in bioorganic medicinal chemistry, we report the in silico prediction, and in vitro evaluation of six new synthetic tegafur analogues having IC(50) values in a broad range between 37.1 and 138 microgmL(-1) for leukemia (L1210/0) and human T-lymphocyte (Molt4/C8, CEM/0) cells. Theoretical predictions coincide very well with experimental results.

Cellular Pharmacology, Antineoplastic Activity and Low In Vivo Toxicity of a Carboxylato-Bridged Platinum(II) Complex bis(acetato)diammine-bis-μ-acetato diplatinum (II) Dihydrate

The dinuclear platinum complex bis(acetato)diammine-bis-micro-acetato diplatinum (II) dihydrate has been previously shown to exert profound cytotoxicity in diverse tumor cell lines, while being far less detrimental than the clinically applied platinum drugs against some susceptible to platinum toxicity non-malignant cellular populations. In the present study we report the investigation of the cellular accumulation kinetics and apoptosis induction of the dinuclear complex in K-562, its potent in vivo antineoplastic activity against L1210 leukemia and Lewis lung carcinoma tumor models and its lower nephrotoxicity, myelosuppressive potential and clastogenicity in vivo relative to cisplatin.

Understanding interactions between and among apoptosis inducing pathways in tumor cells

It has become increasingly clear that the induction of apoptosis in tumor cells can occur by at least three different pathways involving the cell surface receptors, the mitochondria and the endoplasmic reticulum. Specific drugs and conditions can trigger the apoptotic response via one of the three known pathways. What is less clear is how these three pathways can interact synergistically or antagonistically to influence a common convergence step leading to the programmed cell death. In this report we present data to show that fenretinide (a synthetic retinoid) potentiates the apoptotic effects of parthenolide (a drug that inhibits the activation of NF-kappa B) and BAY 11-7085 (an inhibitor of I-kappa B-alpha kinase). This potentiation of apoptosis by fenretinide is seen in the p53-deficient, deoxyadenosine-resistant L1210 cells, but not in the parental L1210 cells that express a mutant p53. These effects are seen at a concentration of fenretinide that have little effect by itself. These data strongly suggest that fenretinide activates or inhibits some step or pathway that interacts with the inhibition of NF-kappa B activation required for the apoptotic response. Since parthenolide, BAY 11-7085 and fenretinide are well known drugs in clinical trials, an understanding of the nature of the interactions between or among the apoptotic pathways could lead to the design of better clinical protocols using these drugs that will promote apoptosis in tumor cells.

Cytotoxic activity of the selected pyridinium salts against murine leukemia L1210

The objective of this work was to evaluate the relationship between chemical reactivity of 3-substituted pyridinium salts and their cytotoxic properties against murine leukemia L1210. Chemical reactivity of pyridinium salts towards NADH oxidation following one-step hydride transfer depends strongly on their redox properties. The investigated reaction may reflect the ability of the salts to deplete NADH level in cells and to affect their metabolic functions. On the other hand, the cytotoxic activity against murine leukemia cells, expressed as ED50 values, varied strongly depending upon the compound used. The investigated salts showed also a diverse antileukemic effect in in vivo experiments as measured by the increase in the survival time of L1210 leukemia-bearing mice. These biological effects were correlated with equilibrium constants found for the reaction of pyridinium salts with NADH.

Anti-tumor efficacy of Cloretazine (VNP40101M) alone and in combination with fludarabine in murine tumor and human xenograft tumor models

Cloretazine (VNP40101M), a new sulfonylhydrazine alkylating agent, has demonstrated broad-spectrum anti-tumor activity in preclinical studies. In this study, Cloretazine was evaluated both as a monotherapy and in combination with fludarabine in murine tumor and human tumor xenograft models. Cloretazine significantly inhibited the growth of subcutaneously implanted tumors, including B16F10 murine melanoma in C57BL/6 mice, and H460 human lung carcinoma and WiDr human colon carcinoma in athymic nude CD1 mice. The inhibition of tumor growth by Cloretazine was dose dependent, increasing from 42.2 to 87% as the dose escalated from 100 to 150 mg/kg. Cloretazine showed equivalent efficacy but lower toxicity compared to cyclophosphamide in these models. The combination therapy, consisting of a single dose of 10 mg/kg Cloretazine plus five doses of 70 mg/kg fludarabine, given every other day intraperitoneally, significantly increased the long-term survival of BDF1 mice bearing the L1210 murine leukemia. On Day 65 post-tumor implantation, the combination therapy yielded a 90% survival rate compared to 40% for Cloretazine alone and 0% for fludarabine alone.

Flavonoids potentiate the efficacy of cytarabine through modulation of drug-induced apoptosis

Recent studies have provided strong evidence for potential beneficial effects of flavonoids in chemoprevention or in combination with chemotherapeutics in tumor cells treatment. The aim of this work was to compare the antioxidant properties of four flavonoids with emphasis on association of these antioxidant properties with their effects on the therapeutic efficacy of cytarabine (AraC) using L1210 leukemia cells. The results of antiproliferative studies showed that antiproliferative potential of flavonoids tested decreased in the order: isorhamnetin > kaempferol > myricetin > rutin, while their antioxidant properties decreased in the order: rutin > myricetin > kaempferol > isorhamnetin. Combinational treatment of isorhamnetin, kaempferol and myricetin with AraC led to synergism in their antiproliferative activities (CIs < 1). Rutin exhibited antagonism with AraC (CIs > 1). Apoptotic DNA fragmentation and flow cytometry analyses revealed that synergism in antiproliferative activities of compounds tested might be due to potentiation of AraC-induced apoptosis. In conclusion, our results clearly indicate that isorhamnetin, kaempferol and myricetin despite their antioxidant properties might be used to increase the sensitivity of leukemia cells to AraC treatment.

[Study on the anticancer effects of extracts from roots of Livistona chinensis in vitro]

OBJECTIVE

To observe the effects of extracts from root of Livistona chinensis on the growth inhibition in seven carcinoma cell lines.

METHODS

The growth inhibition was analyzed by MTT, cell colony and cell growth curve measuremen technique in the stomach carcinoma SGC7901, Lymphocytic leukemia L1210, Lymphoid neoplasm P388D1, tumor of cervix uteri Hela, hepar carcinoma hele 7404, melanoma B16 and mouse neuroblastomax rat glioma hybrid NG108-15 cells lines.

RESULTS

The growth of all tumor cells were inhibited by ethyl acetate of alcohol extract from roots of Livistona chinensis. The growth of all tumor cells were not affected by low dose extracts (0.5 microg/ml). The growth of all tumor cells were obviously inhibited by higher dose extracts (5.0 microg/ml). The growth of all tumor cells were inhibited in growth curve measurement.

CONCLUSION

The results show that ethyl acetate of alcohol extracts from roots Livistona chinensis possesses the role of antitumor in cell culture.

In vitro and in vivo antileukemic effect of novel dimers consisting of 5-fluorodeoxyuridine and arabinofuranosylcytosine

Various amphiphilic heterodinucleoside phosphates containing 1-beta-D-arabinofuranosylcytosine (ara-C) and 5- fluorodeoxyuridine (5-FdUrd) have recently been synthesized in order to increase the efficacy of ara-C and 5-FdUrd. Employing growth inhibition and growth recovery assays, we evaluated the in vitro effects of four of these dimers (No. 2, 2A, 3, 10) in L1210 and P388D1 murine leukemia cells. Although ara-C and 5-FdUrd appeared equimolar in all dimers, their contribution to the cytotoxicity of these agents was different. Thus, the liberation of ara-C and 5-FdUrd from their dimeric origin and their subsequent metabolic activation had a different course. In another set of experiments, we examined the in vivo effects of these agents in mice. The dimer with the highest cytotoxicity in vitro exerted the lowest acute toxicity and yielded the lowest therapeutic effect in vivo. The obtained data indicate that dimers with slower liberation of ara-C and 5-FdUrd were less cytotoxic, but prolonged liberation of both antimetabolites protected them from inactivation and extended the time period of therapeutic action. Some of the dimers exceeded the synergistic effects yielded by simultaneous application of both ara-C and 5-FdUrd. The significantly higher therapeutic potential of these new antitumor agents indicates that further studies are warranted.

Structural differences between sensitive and resistant L1210 cells

The main structural differences between sensitive L1210 mouse leukaemic cells and their multidrug resistant counterpart, obtained by adaptation of the parental cell line to vincristine (VCR), concern the size and shape of the cells, their surface properties and changes in organelles involved in proteosynthesis and transport of substances. The resistant cells are larger with higher density of microvilli. In light and electron micrographs containing a group of cells, cells were found to be closer to each other in L1210/VCR cells than in L1210 cells. This difference in cell aggregation suggests different surface properties which could be visualised by decreased staining of L1210/VCR cell surface coat (glycocalyx) with a polycationic dye ruthenium red. A decrease in surface to volume ratio as a consequence of increased cell size in resistant cells is compensated by proliferation of villi and cytoplasmic protrusions of the cell surface. L1210/VCR cells were further distinguished by higher amount of euchromatin, increase in density of rough endoplasmic reticulum, more developed Golgi apparatus and aggregation of free ribosomes into tetrameric and pentameric polyribosomes. These structural changes may be interpreted as a sign of increase in proteosynthesis and transport of substances.

L1210 cells cultivated under the selection pressure of doxorubicin or vincristine express common mechanisms of multidrug resistance based on the overexpression of P-glycoprotein

Multidrug resistance of neoplastic tissue is often associated with the overexpression and increased drug transport activity of plasma membrane transporters like P-glycoprotein (P-gp), multidrug resistance associated proteins (MRPs) or breast cancer resistance protein, as well as with the elevation of the glutathione detoxification pathway. We have already described the overexpression of P-gp under the selection pressure of vincristine in L1210 mouse leukemia cells. In the present study, mechanisms of multidrug resistance induced in L1210 cells cultivated in the presence of doxorubicin were analyzed. The selection pressure of both vincristine (yielding a resistant subline of L1210 cells, R(V)) and doxorubicin (yielding a resistant subline of L1210 cells, R(D)) induced a dramatic depression of cell sensitivity to both drugs. Both R(V) and R(D) cells demonstrated a lack of ability to accumulate calcein/AM and fluo-3/AM as fluorescent substrates of P-gp and MRP. The retention of dyes could be reached in both cell sublines by the application of inhibitors of P-gp (like verapamil) but not by probenecid - an inhibitor of anion transporters, including MRPs. Massive protein bands, at a M(r) range of 130-180 kDa that interact with c219 antibody against P-gp, were detected in the crude membrane fraction isolated from both R(V) and R(D) (but not from L1210) cells by Western blot. The cytosolic activity of glutathione S-transferase was found to be similar in R(V) and R(D) cells and did not differ significantly from the activity ascertained in parental L1210 cells. Neither the R(V) nor R(D) cell sublines differed considerably, as measured by cell ultrastructure. In conclusion, based on P-gp overexpression, both doxorubicin and vincristine induce a common multidrug resistance phenotype in L1210 cells.

[Effect of T-bet on biological functions of mouse macrophage Raw264.7]

BACKGROUND & OBJECTIVE

T-bet (T box expressed in T cells), a Th1-specific T box transcription factor, controls many kinds of immune cells, such as Th1, NK, CD8+, dendritic cells, and B cells. This study was to explore potential effects of T-bet gene on biological functions of mouse macrophage Raw264.7 cells in vitro.

METHODS

The eukaryotic expression vector carrying mouse T-bet (pcDNA3.0-mT-bet) was constructed and identified by consequence analysis, double restrictive endonucleases digestion and polymerase chain reaction (PCR). The gene expression in Raw264.7 cells was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. PBS, pcDNA3.0, and pcDNA3.0-mT-bet were transiently transfected into Raw264.7 cells respectively; cell cycle, MHC I/II expression levels, phagocytic activity of FITC-dextran, nitric oxide (NO) secretion level, and the cytotoxicity of Raw264.7 cells to mouse leukemia cell line L1210 were evaluated 48 hours after transfection.

RESULTS

Eukaryotic expression vector which could express T-bet protein in Raw264.7 cells was successfully constructed. There was no difference in cell cycle between pcDNA3.0 group and pcDNA3.0-mT-bet group. There was significant difference in MHC I expression level between pcDNA3.0 group (20.8+/-0.7) and pcDNA3.0-mT-bet group (24.8+/-0.6, P<0.05), but not in MHC II expression level; there was also difference in mean fluorescence intensity of phagocytized dextran between pcDNA3.0 group (28.2+/-0.4) and pcDNA3.0-mT-bet group (32.8+/-0.8, P<0.05); there was also significant difference in NO secretion level between pcDNA3 group (0 pmol) and pcDNA3.0-mT-bet group [(1.7+/-0.6) pmol, P<0.05] without lipopolysaccharide (LPS) stimulation; meanwhile, significant difference was also observed between pcDNA3.0 group [(10.5 +/-1.3) pmol] and pcDNA3.0-mT-bet group [(15.6+/-1.6) pmol, P<0.05] under the stimulation of LPS (10 microg/ml) for 20 h; there was also difference in cytotoxicity of Raw264.7 cells to L1210 cells in vitro between pcDNA3 group [(35.6+/-2.1)%] and pcDNA3.0-mT-bet group [(51.9+/-3.5)%, P<0.05].

CONCLUSION

T-bet up-regulates MHC I expression and NO secretion level in Raw264.7 cells, increases their cytotoxicity to L1210 cells, but has no influences on the cell cycle and MHC II expression.

Structures, biogenetic relationships, and cytotoxicity of pimarane-derived diterpenes from Petalostigma pubescens

Extraction of Petalostigma pubescens heartwood followed by chromatographic purifications and crystallizations afforded five tricyclic diterpenes: 5,9-syn-rosanes petalostigmones A and B (1 and 2), the erythroxylane petalostigmone C (3), the norditerpene lactone pubescenone (4), and the known ent-cleistanthane diterpene (-)-sonderianol (5). The structures and relative stereochemistry were elucidated by means of spectroscopic methods, chemical correlations, and, in the cases of 1 and 4, by X-ray crystallographic analyses. The new isolates 1-4 are assumed to belong to the same absolute configurational family (9alphaCH3) of ent-pimarane-derived diterpenes as the known co-occurring (-)-5 (10alphaCH3). Biogenetic schemes originating from a common ent-copalyl diphosphate intermediate are presented to rationalize the structures of these natural products. A novel ring contraction-ring expansion mechanism is suggested to account for the 7-membered B ring of pubescenone. Compounds 1-5 were evaluated for their cytotoxicity; sonderianol (5) showed the highest activity against mouse leukemia cell lines L1210, P388 and mouse liver cancer cells HEPA1c1c7.

Dual activity of triterpenoids: apoptotic versus antidifferentiation effects

Triterpenoids are natural, biologically active compounds extracted from many plants. They possess antiinflammatory, anticancer, and antioxidant properties. In the report presented, antiproliferative effects and leukemia cell growth and apoptosis modulating activities of ursolic acid (UA) and oleanolic acid (OA) were investigated. Both triterpenoids are inhibitors of leukemia cell growth and inductors of apoptosis. However, when applied in combination with anthracycline antitumor antibiotic doxorubicin (Dox), UA and OA diversely modulate therapeutic efficacy of Dox, due to different antioxidant activities. Compare to OA showing synergism/additive effect with Dox, UA (stronger antioxidant) acts antagonistically and reduces leukemia cell growth inhibiting and differentiation effects induced by Dox. In conclusion, these findings suggest that although triterpenoids UA and OA can induce apoptosis, their antioxidant activities can interfere with the therapeutic effect of antitumor antibiotic Dox which mechanism of action is attributed to the production of reactive oxygen species.

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.

Protection of Bcl-2 by salubrinal

The drug salubrinal has been identified as an inhibitor of phosphatases that act on the eukaryotic translation initiation factor 2 subunit (eIF2alpha). The resulting maintenance of protein phosphorylation results in enhanced protection from the adverse effects of initiators of the unfolded protein response. We found that salubrinal can also interact with the anti-apoptotic protein Bcl-2, inhibiting binding of the non-peptidic antagonist HA14-1 and of a porphycene that can catalyze Bcl-2 photodamage. As a result, salubrinal offers protection from the apoptotic and autophagic effects that can result from loss of Bcl-2 function.

Anti-tumor effects of the bacterium Caulobacter crescentus in murine tumor models

Caulobacter crescentus is a gram negative, non-pathogenic bacterium, common in aquatic and soil environments. One feature of note is a protein surface layer (S-layer) composed of a single protein, organized as a self-assembled crystalline array that coats the bacterium. In the course of efforts to express cancer-associated peptides as genetic insertions into the S-layer, we noted a tumor suppressive effect of the unmodified bacterium. C. crescentus was examined for anti-tumor activity against three transplantable tumor mouse models: Lewis lung carcinoma cells transfected with the MUC1 gene in C57BL/6, murine mammary carcinoma (EMT-6) in BALB/c (both in prophylactic and therapeutic mode) and murine leukemia cells (L1210) in DBA2. Mice were immunized three times i.p. with C. crescentus (2 x 10(7) cells/mouse). In prophylactic mode, the mice were challenged with tumor cells two weeks after the last immunization. Immunization with live C. crescentus resulted in anti-tumor activity in all three transplantable tumor models, as measured by prolonged survival, reduced tumor mass or reduced number of lung nodules, compared to saline control groups. In the Lewis lung and the EMT-6 mammary carcinoma murine models the number of lung nodules as well as the tumor weight was lower in mice treated with C. crescentus, compared to the control group; for EMT-6, this was observed in prophylactic and therapeutic modes. In the murine leukemia and Lewis lung carcinoma models prolonged survival was observed in the groups of mice immunized with Caulobacters. In most cases the live C. crescentus cells were markedly more efficacious than heat killed or formalin fixed cells, despite the fact that they do not grow or persist in mice. The results suggest that C. crescentus may be a safe, bacterial immunomodulator for the treatment of tumors.

Bis(2-hydroxybenzylidene)acetone, a potent inducer of the phase 2 response, causes apoptosis in mouse leukemia cells through a p53-independent, caspase-mediated pathway

Bis(2-hydroxybenzylidene)acetone is a potent inducer of the phase 2 response through the Keap1-Nrf2-ARE pathway. This double Michael reaction acceptor reacts directly with Keap1, the sensor protein for inducers, leading to enhanced transcription of phase 2 genes and protection against oxidant and electrophile toxicities. In our efforts to identify potent chemoprotective agents, we found that in rapidly growing murine leukemia cells (L1210) low concentrations (in the submicromolar range) of bis(2-hydroxybenzylidene)acetone markedly increased the activities of NAD(P)H:quinone acceptor oxidoreductase 1 (NQO1) and glutathione reductase, and the levels of total glutathione, three markers of the phase 2 response. In contrast, at high concentrations (in the micromolar range) the same compound caused G2/M cell cycle arrest and apoptosis. Importantly, a mutant L1210 cell line (Y8), selected for resistance to deoxyadenosine and lacking expression of p53 protein, was considerably more sensitive to the apoptotic effects of bis(2-hydroxybenzylidene)acetone. When caspase activities were evaluated in cell-free extracts prepared from treated wild type or mutant L1210 cells, the activities of caspase-3, the terminal caspase in the cascade leading to apoptosis, and caspase-10 were found to be markedly elevated. The activities of other caspases measured, caspase-1, -6 and -8, were not appreciably affected. Thus, both induction of the phase 2 response and p53-independent, caspase-3-mediated apoptosis could act cooperatively in chemoprotection. The concentration-dependent differential effects on these two pathways should be carefully considered in mechanistic explanations and strategic designs.

Effects of PRIMA-1 on wild-type L1210 cells expressing mutant p53 and drug-resistant L1210 cells lacking expression of p53: necrosis vs. apoptosis

The effects of PRIMA-1 on wild-type (WT) mouse leukemia L1210 cells and drug-resistant L1210 cells (Y8) were studied with respect to the induction of apoptosis and necrosis in these cell lines. The WT L1210 cells express mutant p53 while the Y8 L1210 cells do not express p53 mRNA or protein, but do express WAF1/p21 and Gadd 45 mRNA's and proteins. It was found that, in response to treatment with PRIMA-1, the WT L1210 cells became necrotic with little apoptosis while the Y8 L1210 cells showed a much higher level of apoptosis than necrosis. Flavopiridol in combination with PRIMA-1 caused a synergistic increase in necrosis in the WT L1210 cells while LY 294002 in combination with PRIMA-1 caused a synergistic increase in apoptosis in the Y8 L1210 cells. These studies showed that PRIMA-1 had an effect not only on cells expressing mutant p53, but also on cells that do not express p53, suggesting that PRIMA-1 and PRIMA-1-like molecules have multiple sites of action independent of restoring p53 function and that these can interact with other signaling pathways involving CDK's and PI3 kinases.

NGF overexpression and distribution in cortical thymic epithelial cells of mice with experimentally-induced leukemia

BACKGROUND

Thymic epithelial cells often form lymphoid-epithelial cell (LEC) complexes, thought to contribute both to normal T-cell differentiation and to leukemogenesis. The distribution of the nerve growth factor (NGF) and NGF immunoreactivity modulation of complex-forming thymus epithelial cells were studied in mice with experimental acute L1210 leukemia.

MATERIALS AND METHODS

Light and electron microscopic methods and cell separation techniques were applied.

RESULTS

Immunoperoxidase and immunogold labelling showed subcapsular and subseptal overexpression of NGF by epithelial cells in leukemic thymus. NGF immunopositive epithelial cells were closely associated with lymphoid cells. The increased immunoreactivity of epithelial cells correlated with LEC complex formation, including thymic nurse cell-like structures and rosettes in the external cortex.

CONCLUSION

These results provide new structural and immunocytochemical evidence for intimate contact between NGF-producing epithelial cells and lymphoid cells and suggest that NGF immunoreactive LEC complexes are involved in thymic microenvironmental reorganization during leukemogenesis.

HAMLET triggers apoptosis but tumor cell death is independent of caspases, Bcl-2 and p53

HAMLET (Human alpha-lactalbumin Made Lethal to Tumor cells) triggers selective tumor cell death in vitro and limits tumor progression in vivo. Dying cells show features of apoptosis but it is not clear if the apoptotic response explains tumor cell death. This study examined the contribution of apoptosis to cell death in response to HAMLET. Apoptotic changes like caspase activation, phosphatidyl serine externalization, chromatin condensation were detected in HAMLET-treated tumor cells, but caspase inhibition or Bcl-2 over-expression did not prolong cell survival and the caspase response was Bcl-2 independent. HAMLET translocates to the nuclei and binds directly to chromatin, but the death response was unrelated to the p53 status of the tumor cells. p53 deletions or gain of function mutations did not influence the HAMLET sensitivity of tumor cells. Chromatin condensation was partly caspase dependent, but apoptosis-like marginalization of chromatin was also observed. The results show that tumor cell death in response to HAMLET is independent of caspases, p53 and Bcl-2 even though HAMLET activates an apoptotic response. The use of other cell death pathways allows HAMLET to successfully circumvent fundamental anti-apoptotic strategies that are present in many tumor cells.

Nocodazole does not synchronize cells: implications for cell-cycle control and whole-culture synchronization

It has been predicted that nocodazole-inhibited cells are not synchronized because nocodazole-arrested cells with a G2-phase amount of DNA would not have a narrow cell-size range reflecting the cell size of some specific, presumably G2-phase, cell-cycle age. Size measurements of nocodazole-inhibited cells now fully confirm this prediction. Further, release from nocodazole inhibition does not produce cells that move through the cell cycle mimicking the passage of normal unperturbed cells through the cell cycle. Nocodazole, an archetypal whole-culture synchronization method, can inhibit growth to produce cells with a G2-phase amount of DNA, but such cells are not synchronized. Cells produced by a selective (i.e., non-whole-culture) method not only have a specific DNA content, but also have a narrow size distribution. The current view of cell-cycle control that is based on methods that are not suitable for cell-cycle analysis must therefore be reconsidered when results are based on whole-culture synchronization.

Schedule-Dependent Antitumor Activity and Toxicity of Combinations of 5-Fluorouracil and Cisplatin/Carboplatin against L1210 Leukemia-Bearing Mice

The combination of cisplatin (CDDP) and 5-fluorouracil (5-FU) has been reported to show marked therapeutic effects on experimental tumors and human malignancies, such as head and neck cancer. In these clinical studies, CDDP was administered on day 1 and followed by a 5-d continuous infusion of 5-FU. However, it was repeatedly shown that the sequence of 5-FU followed by CDDP is more active and less toxic in tumor-bearing animals. Thus, the optimal administration schedule of CDDP and 5-FU against L1210 murine leukemia was examined and compared with that of the combination of 5-FU and carboplatin (JM-8). The combinations of 5-FU (days 1 to 5) and CDDP, given either on day 1 or on day 5, showed a similar level of antitumor activity and toxicity. On the other hand, the combinations of 5-FU (days 1 to 5) and JM-8 given on day 5 showed significantly higher antitumor activity and rather less toxicity, as compared with the combinations on the reverse sequence. Thus, the treatment sequence of platinum compounds followed by a 5-d continuous infusion of 5-FU in many clinical studies appears to be extremely favorable to CDDP than JM-8. In addition, pathological examinations of died mice showed that accumulation of ascites and pleural effusion was inhibited most effectively by JM-8, given alone or in combination with 5-FU. These results strongly suggest that the combination of 5-FU followed by JM-8 will be expected to show more excellent antitumor activity against human malignancies, and may be especially useful in patients who are unable to tolerate CDDP-related toxicity.