Synthesis and in vitro antiproliferative evaluation of some ring B abeo-sterols

Using cholesterol, β-sitosterol, dehydroisoandrosterone and pregnenolone as starting materials, a series of 5(6→7)abeo-sterols with different substituted groups and various side chains were synthesized and the antiproliferative activity of these compounds against HeLa, SMMC 7404 and MGC 7901 cells was investigated. The results revealed that the presence of a cholesterol-type side chain was very important for their cytotoxicity, and in particular a thiosemicarbazone at the C-6 position significantly enhanced the antiproliferative activity of these compounds. Although the elimination of 5-hydroxyl has no an obvious effect on their cytotoxic function, removal of the hydroxyl at the C-3 position decreased markedly the antiproliferative activity of the compounds. Some compounds have similar cytotoxic capability as cisplatin does.     

The synthesis of 18beta-glycyrrhetinic acid derivatives which have increased antiproliferative and apoptotic effects in leukemia cells

18beta-Glycyrrhetinic acid (GA), 3beta-hydroxyl-11-oxo-olean-12-ene-29-oic acid, has been found to inhibit growth and to induce apoptosis in cancer cells. Through structural modification, 16 GA derivatives (12 novel compounds) with modified structures at the C(3) and C(29) positions were synthesized. The antiproliferative effects and apoptosis induction abilities of these compounds were determined in human leukemia HL-60 cells. The replacement of the hydroxyl group of GA with a carbonyl group or an oxime group at C(3) position does not influence the antiproliferative effect. However, the antiproliferative and apoptosis induction abilities of the compounds with a replaced alkoxyimino group at position C(3) and a free C(29) carboxyl group are markedly increased.     

C29 sterols with a cyclopropane ring at C-25 and 26 from the Vietnamese marine sponge Ianthella sp. and their anticancer properties

Two new C₂₉ sterols with a cyclopropane ring at C-25 and C-26, petrosterol-3,6-dione (1) and 5α,6α-epoxy-petrosterol (2), along with petrosterol (3), were isolated from the Vietnamese marine sponge Ianthella sp. The structures of the new compounds were elucidated by comprehensive spectroscopic analyses. Compounds 1?3 showed cytotoxic activities on A549, HL-60, MCF-7, SK-OV-3, and U937 cancer cell lines with IC₅₀ in the range of 8.4–22.6 μM, whereas compounds 1?3 exhibited only weak cytotoxic activities on HT-29 cell. After HL-60 cells were treated with the compounds, several apoptosis events like chromatin condensation and the increase of the population of sub-G1 hypodiploid cells were observed. These data supported that the compounds might have potential for leukemia treatment.     

Design and synthesis of novel nitrogen mustard-evodiamine hybrids with selective antiproliferative activity

A series of novel nitrogen mustard-evodiamine hybrids were synthesized and evaluated for their antitproliferative properties. The antiproliferative activities of 10a–d, 11a–d, and 12a–d against four different kinds of human cancer cell lines (PC-3, HepG2, THP-1 and HL-60) and human normal peripheral blood mononuclear cells (PBMC) were determined. The results showed that all the target hybrid compounds exhibited antiproliferative activities against tested human tumor cell lines to some extent and no antiproliferative activities (>200?μM) against human normal PBMC cells. The antiproliferative selectivity between tumorous and normal cells was very useful for further antitumor drug development. Among the target compounds, 12c showed the strongest cytotoxicity against two tumor cell lines (THP-1 and HL-60) with IC₅₀ values of 4.05?μM and 0.50?μM, respectively, and selected for further mechanism study in HL-60 cells. The results showed that 12c could induce HL-60 cells apoptosis and arrest at G₂ phase at low sub-micromolar concentrations via mitochondria-related pathways.     

Design,synthesis, in vitro antiproliferative activity and apoptosis-inducing studies of 1-(3′,4′,5′-trimethoxyphenyl)-3-(2′-alkoxycarbonylindolyl)-2-propen-1-one derivatives obtained by a molecular hybridisation approach

Inhibition of microtubule function using tubulin targeting agents has received growing attention in the last several decades. The indole scaffold has been recognized as an important scaffold in the design of novel compounds acting as antimitotic agents. Indole-based chalcones, in which one of the aryl rings was replaced by an indole, have been explored in the last few years for their anticancer potential in different cancer cell lines. Eighteen novel (3′,4′,5′-trimethoxyphenyl)-indolyl-propenone derivatives with general structure 9 were synthesized and evaluated for their antiproliferative activity against a panel of four different human cancer cell lines. The highest IC₅₀ values were obtained against the human promyelocytic leukemia HL-60 cell line. This series of chalcone derivatives was characterized by the presence of a 2-alkoxycarbonyl indole ring as the second aryl system attached at the carbonyl of the 3-position of the 1-(3′,4′,5′-trimethoxyphenyl)-2-propen-1-one framework. The structure–activity relationship (SAR) of the indole-based chalcone derivatives was investigated by varying the position of the methoxy group, by the introduction of different substituents (hydrogen, methyl, ethyl or benzyl) at the N-1 position and by the activity differences between methoxycarbonyl and ethoxycarbonyl moieties at the 2-position of the indole nucleus. The antiproliferative activity data of the novel synthesized compounds revealed that generally N-substituted indole analogues exhibited considerably reduced potency as compared with their parent N-unsubstituted counterparts, demonstrating that the presence of a hydrogen on the indole nitrogen plays a decisive role in increasing antiproliferative activity. The results also revealed that the position of the methoxy group on the indole ring is a critical determinant of biological activity. Among the synthesized derivatives, compound 9e, containing the 2-methoxycarbonyl-6-methoxy-N-1H-indole moiety exhibited the highest antiproliferative activity, with IC₅₀ values of 0.37, 0.16 and 0.17?μM against HeLa, HT29 and MCF-7 cancer cell lines, respectively, and with considerably lower activity against HL-60 cells (IC₅₀: 18?μM). This derivative also displayed cytotoxic properties (IC₅₀ values ～1?μM) in the human myeloid leukemia U-937 cell line overexpressing human Bcl-2 (U-937/Bcl-2) via cell cycle progression arrest at the G₂-M phase and induction of apoptosis. The results obtained also demonstrated that the antiproliferative activity of this molecule is related to inhibition of tubulin polymerisation. The presence of a methoxy group at the C5- or C6-position of the indole nucleus, as well as the absence of substituents at the N-1-indole position, contributed to the optimal activity of the indole-propenone-3′,4′,5′-trimethoxyphenyl scaffold.     

Biological activities of marine sesquiterpenoid quinones: structure-activity relationships in cytotoxic and hemolytic assays

Sesquiterpenoid quinones from marine sponges and their semisynthetic derivatives were compared for cytotoxicity on developing eggs of sea urchin Strongylocentrotus nudus and Ehrlich carcinoma cells, and for hemolytic activities on mice red blood cells. Structure-activity studies showed that activities of these compounds with a hydroxyl group at C-20 ((2), (7)) were higher than their methoxyl ((1), (8)) and amino ((4), (5)) derivatives at this position. Sesquiterpenoid quinones containing a dihydropyran ring ((10)-(12)) had lower activity than noncyclic compounds. The structure of the terpenoid moieties of the compounds had no significant influence on biological activity. There was a direct correlation between cytotoxic and hemolytic activities. This report discusses the mechanism of action employed by these compounds against cell membranes.     

Isolation of apoptosis- and differentiation-inducing substances toward human promyelocytic leukemia HL-60 cells from leaves of Juniperus taxifolia

A chloroform extract of the leaves of Juniperas taxifolia exhibited a marked antiproliferative effect on human promyelocytic leukemia HL-60 cells at a concentration of 2.5 microg/ml. Deoxypodophyllotoxin (4) was identified in the extract as an outstanding antiproliferative compound, and five diterpenes (1-3, 5, and 6) were isolated as known compounds with weak or no cytotoxicity. These compounds were examined for their respective apoptosis- and differentiation-inducing activities toward HL-60 cells by DNA fragmentation and NBT-reducing assays, respectively. Among them, 7alpha-hydroxysandaracopimaric acid (6) was found to have a potent differentiation-inducing activity in a dose-dependent manner at 0.125-2 microg/ml (0.39-6.29 microM), together with apoptosis-inducing activity at concentrations of more than 2.5 microg/ml (7.86 microM). Deoxypodophyllotoxin (4) that exerted cytotoxic and apoptosis-inducing activities at 2 ng/ml (5 nM) did not induce differentiation at the same concentration, and the other diterpenes (1-3 and 5) showed no effect on cell differentiation, even at 5 microg/ml. It was thus demonstrated for the first time that 7alpha-hydroxysandaracopimaric acid was an effective differentiation-inducing compound toward HL-60 cells.     

Antileukemic effect of coral-prostanoids clavulones from the stolonifer Clavularia viridis on human myeloid leukemia (HL-60) cells

To elucidate the biological activities of coral-prostanoids, clavulones, discovered from the Japanese stolonifer Clavularia viridis, we examined the effect of clavulone on the cell growth of human cancer (human promyelocytic leukemia (HL-60) cells and HeLa cells) and normal (Chang liver cells and lung fibroblasts) cells in vitro. Clavulone showed strong antiproliferative and cytotoxic activities in the human cells and it had some selectivity to leukemic (HL-60) cells over other HeLa cells or normal cells on the basis of the IC50 values and cytotoxic effect of the cells. The IC50 value of clavulone in the HL-60 cells was about 0.4 microM (0.2 micrograms/ml). Over 1.0 microM (0.5 micrograms/ml), clavulone showed a significant cytotoxic activity on the HL-60 cells. The data on DNA synthesis and flow cytometric analysis revealed that clavulone arrests the cells in the G1-phase and inhibits the cell growth of HL-60 cells by inhibiting S-phase DNA synthesis. These results suggest that clavulone has a potent antileukemic effect on HL-60 cells.     

Synthesis,antioxidant and antiproliferative activities of 1,3,4-thiadiazoles derived from phenolic acids

Two 2-amino-1,3,4-thiadiazoles containing phenolic hydroxyl groups were combined with different carboxylic acid chlorides giving sixteen amide derivatives with good antioxidant and antiproliferative potential. The compound 3′c with an adamantane ring displayed excellent DPPH radical scavenging activity and good cytotoxic activity against human acute promyelocytic leukemia HL-60 cells, while 1,3,4-thiadiazole 3′h with 4-chlorophenyl moiety was found to be the most effective in inhibition of survival of lung carcinoma A549 cells. All examined thiadiazoles except 3a and 3′a exerted higher cytotoxic activities on A549 and HL-60 cancer cells when compared with normal fibroblasts MRC-5, pointing to selectivity in their antiproliferative action. Some of the most active novel compounds 3c, 3′c, 3′g and 3′h induced significant increase in the percentage of HL-60 cells in the subG1 cell cycle phase in comparison with the control cells. The induction of cell death in HL-60 cells by these compounds was at least partially dependent on activation of caspase-3 and caspase-8. The compounds 3c and 3′c exerted strong antiangiogenic activity. Furthermore, compounds 3c, 3′c, 3′g and 3′h showed the ability to down-regulate the MMP2 and VEGFA expression levels in the treated HL-60 cells when compared with the control cell samples.     

Synthesis and biological evaluation of hydroxylated 3-phenylcoumarins as antioxidants and antiproliferative agents

Based on the observed biological activities of coumarins and resveratrol, we synthesized fourteen hydroxylated 3-phenylcoumarins (stilbene-coumarin hybrids) including six novel ortho-hydroxy-methoxy substituted derivatives, 1-14, by Perkin reaction. We characterized these compounds concerning their antioxidant activity against 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced pBR322 DNA strand breakage, and their antiproliferative effects on human promyelocytic leukemia HL-60 and human lung adenocarcinoma epithelial A549 cells. Structure-activity relationship information suggests that the introduction of ortho-hydroxy-methoxy groups and ortho-dihydroxy groups on the aromatic A ring could efficiently improve antiproliferative activity. Interestingly, a new derivative, 6-methoxy-7-hydroxy-3-(4'-hydroxyphenyl)coumarin, 9, behaved as a poor antioxidant but appeared to be the most potent antiproliferative agent among the compounds examined, and this activity was mediated by deregulation in cell cycle and induction of apoptosis.     

Synthesis, DNA interaction and cytotoxicity studies of cis-{[1, 2-bis(aminomethyl)cyclohexane]dihalo}platinum(II) complexes

A series of platinum compounds with an analogue structure to cisplatin have been synthesized and their biological activity against HL-60 cancer cell line has been studied. The interaction with DNA was evaluated by circular dichroism (CD), electrophoresis and atomic force microscopy (AFM) techniques showing slight but significant structure-dependent differences among the evaluated complexes. The cytotoxicity assays afforded interesting relationships between the structure and the biological activity, thus, a better antiproliferative activity was observed for the complexes with higher hydrophobicity: the methoxylated complexes showed better activity than the hydroxylated ones (17versus20 and 19versus21). Especially compound 22 having a fatty acid subunit presented a promising cytotoxic activity. On the other hand, dichloro complexes 12 and 13 had better activities than the diiodo complexes, probably due to their better metabolic stability. Between both dichloro complexes the aromatic one showed much higher activity, which could be rationalized on the basis of the intercalating ability of the benzene ring. The flow cytometry assays indicated that most of the complexes induced the cell death by apoptosis except for aromatic compound 12 and the lipophilic compound 22 that induced preferably a mechanism of necrosis.     

Synthesis of a series of novel dihydroartemisinin derivatives containing a substituted chalcone with greater cytotoxic effects in leukemia cells

Fifteen dihydroartemisinin derivatives containing a substituted chalcone linked by either ether or ester were synthesized and investigated for their cytotoxicity in human leukemia HL-60 and mouse lymphoma P388 cells. These derivatives have greater antiproliferative and cytotoxic effects in both cell lines than dihydroartemisinin. Dihydroartemisinin chalcones linked by ether are more cytotoxic than dihydroartemisinin chalcones linked by ester with apoptosis induction abilities.     

Effect of C-ring modifications on the cytotoxicity of spirostan saponins and related glycosides

Twelve C-ring modified spirostanyl glycosides were synthesized and evaluated for their cytotoxicity against the human myeloid leukemia cell line (HL-60). With the aim of assessing the influence of the hydrophobic character, the conformational flexibility and the stereochemistry of the C-ring functionalities on the cytotoxic activity, a variety of spirostanic aglycones incorporating methylene, methoxyl, α,β-unsaturated ketone and lactone groups were subjected to a linear glycosylation strategy leading to glycosides derived from the 3,6-dipivaloylated β-D-glucoside and the β-chacotrioside moieties. The 3,6-dipivaloylated spirostanyl β-D-glucosides showed moderate to good cytotoxic activity against HL-60, but no significant cytotoxicity against benign blood cells. However, the cytotoxicity of spirostanyl β-chacotriosides was highly dependent on the nature of the C-ring functional groups of the steroidal aglycones. Actually, the chacotrioside-based saponins either with no functionality or bearing a hydrophobic methylene group at C-12 were the most cytotoxic ones against both HL-60 and benign blood cells. On the other hand, the incorporation of very polar functionalities and the opening of the ring C with the consequent loss of rigidity led to a significant drop in the cytotoxicity against HL-60. These results confirm that spirostanyl β-chacotriosides including very lipophilic aglycones are the most cytotoxic ones among their congeners.     

Differential apoptotic effect of wogonin and nor-wogonin via stimulation of ROS production in human leukemia cells

We investigate the roles of methoxyl (OCH(3)) and hydroxyl (OH) substitutions at C8 of flavonoids on their apoptosis-inducing activities. Wogonin (Wog) and nor-wogonin (N-Wog) are structurally related flavonoids, and respectively contain an OH and OCH(3) at C8. In leukemia HL-60 cells, N-Wog exhibited more-potent cytotoxicity than Wog according to the MTT and LDH release assays, and the IC(50) values of Wog and N-Wog in HL-60 cells were 67.5 +/- 2.1 and 21.7 +/- 1.5 microM, respectively. Apoptotic characteristics including DNA ladders, apoptotic bodies, and hypodiploid cells accompanied by the induction of caspase 3 protein processing appeared in Wog- and N-Wog-treated HL-60 cells. Interestingly, an increase in intracellular peroxide production was detected in N-Wog- but not Wog-treated HL-60 cells by the DCHF-DA assay, and the reduction of intracellular peroxide by catalase (CAT) induced by N-Wog significantly reduced the N-Wog- but not the Wog-induced cytotoxic effect according to the MTT assay in accordance with the blocking of DNA ladder formation and caspase 3 and PARP protein processing elicited by N-Wog. We further analyzed the effect of six structurally related compounds, including 5-OH, 7-OH, 5,7-diOH, 5,7-diOCH(3), 7,8-diOCH(3), and 7-OCH(3)-8-OH flavones, on apoptosis induction in HL-60 cells. Results suggested that OH at C5 and C7 is essential for both the apoptosis-inducing activity of flavonoids, and OH at C8 may contribute to apoptosis induction ability. Evidence to support a distinct structure-activity relationship in apoptosis induction of flavonoids is provided for the first time in this study.     

Evidence of multifactorial mechanisms in an adriamycin-resistant HL-60 promyelocytic leukemia cell line

HL-60/AR leukemia cells, which were 60-fold resistant to the growth inhibitory activity of adriamycin, remained sensitive to the antiproliferative and differentiation-inducing activities of aclacinomycin A. The replication of HL-60/AR and of adriamycin sensitive parental HL-60 cells was inhibited by greater than 80% by 30 nM aclacinomycin A and the majority of cells (about 60 to 70%) of each line underwent granulocytic differentiation when treated with this agent, as assessed by the reduction of nitroblue tetrazolium. Measurement of the initial rates of uptake of daunorubicin and steady-state levels of adriamycin in sensitive and resistant lines indicated that transport differences do not fully account for the insensitivity of HL-60/AR cells to these anthracyclines. Furthermore, 30-fold greater levels of cell-associated adriamycin were required in HL-60/AR cells for toxic effects equivalent to those occurring in parental HL-60 cells. Analysis of DNA histograms of adriamycin treated HL-60 cells indicated that cell-cycle progression was blocked in G2-M, while this antibiotic blocked progression of resistant HL-60/AR cells in the S phase. These results suggest that, in addition to alterations in membrane permeability, differential sensitivity of multiple biochemical targets may be important in the toxicity and the development of resistance to anthracyclines. Furthermore, the finding that HL-60/AR cells do not exhibit cross-resistance to aclacinomycin A indicates that this oligosaccharide-containing anthracycline may have utility in the treatment of adriamycin resistant neoplasms.     

New derivatives of 11-methyl-6-[2-(dimethylamino)ethyl]-6H-indolo[2,3-b]quinoline as cytotoxic DNA topoisomerase II inhibitors

Novel indolo[2,3-b]quinoline derivatives substituted at N-6 and C-2 or C-9 positions with (dimethylamino)ethyl chains linked to heteroaromatic core by ether, amide or amine bonds, were manufactured and evaluated in vitro for their cytotoxic activity against several cell lines of different origin including multidrug resistant sublines and tested for their ability to influence the cell cycle and inhibit topoisomerase II activity. It was found, that all compounds show cytotoxic activity against cell lines tested, including multidrug resistant LoVo/DX, MES-SA/DX5 and HL-60 sublines. The tested compounds induce the G(2)M phase cell cycle arrest in Jurkat cells, and inhibit topoisomerase II activity.     

Novel CADD-based peptidyl vinyl ester derivatives as potential proteasome inhibitors

A series of peptidyl vinyl ester derivatives bearing three different P1 substitutions as potential proteasome inhibitors were studied. The target molecules were designed based on CADD (computer aided drug design) protocol and synthesized. Their activities toward proteasome and four human cancer cell lines (including hepatoma cell line (Bel-7402), myeloid leukemic cell line (HL-60), gastric cancer cell line (BGC-823) and nasopharyngeal cancer cell line (KB)) were tested using fluorescence assay. Two compounds showed proteasome inhibitory activities, and four compounds showed weak antiproliferative activities toward HL-60 and BGC-823.     

Structural features of prostanoid analogues involved in hepatocytes protection against CCl4-induced injury

The ability of natural prostaglandins (PGs) and synthetic prostanoids of B, H and E(1)-types to prevent CCl(4)-induced liver injury in vitro was examined. Seven analogs of PGB, 3 derivatives of PGH and two 11-deoxy-analogs of PGE(1) decreased cytotoxic index of CCl(4) by 2-fold and were more effective then such well-known hepatoprotectors as silymarin, curcumin and PGI(2). These prostanoids reduced trien conjugates formation by 25-95% and strongly prevented LDH leakage through plasma membrane. The results from the structure-activity relationship (SAR) analysis can be summarized as follows: (1) the presence of 2-pyridyl at the 15 position of ω-chain plays the main role in cytoprotection for synthetic analogs of PGH; (2) among 11-deoxy-analogs of PGE(1) the most active substances possess the phenyl residue at C-15 connected with C-13 isoxazolin or C-13 isoxazol; (3) C-13 cyclohexylamine or C-15 phenyl groups in ω-chain and metoxy-group in α-chain are important for protective activity of PGB analogs; (4) synthetic analogs of PGB demonstrate more pronounced cytoprotective properties than prostanoids of H and E-types. This information suggests paths for further exploration in the area of hepatoprotection and the design of novel therapeutic agents.     

2,7-Dihydro-3H-pyridazino[5,4,3-kl]acridin-3-one derivatives, novel type of cytotoxic agents active on multidrug-resistant cell lines. Synthesis and biological evaluation

We have earlier postulated that the presence of a pyridazone ring fused with an anthracenedione moiety resulted in the analog's ability to overcome multidrug resistance of tumor cells [J. Med. Chem.1999, 42, 3494]. High cytotoxic activity of obtained anthrapyridazones [Bioorg. Med. Chem.2003, 11, 561] toward the resistant cell lines, prompted us to synthesize the similarly modified acridine compounds. A series of pyridazinoacridin-3-one derivatives (2b-h) were prepared from the reaction of 9-oxo-9,10-dihydroacridine-1-carboxylate with POCl(3), followed by addition of the appropriate (alkylamino)alkylhydrazines. In vitro cytotoxic activity toward sensitive and resistant leukemia cell lines: L1210, K562, K562/DX, HL-60, HL-60/VINC, and HL-60/DX, with various type of multidrug resistance (MDR and MRP) was determined. The compounds studied exhibited in comparison to the reference cytostatics (DX, MIT) desirable very low resistance indexes (RI). Variations have been observed depending upon the substituent and the type of drug exporting pump. The cytotoxic activities of examined compounds, as well as of model anthrapyridazone derivative PDZ, were lower than those of reference drugs (DX, MIT) due to their diminished affinity to DNA.     

Derivatives of antineoplastic antibiotics of the daunorubicin series containing methylurea or nitrosomethylurea residues

Derivatives of antitumour anthracycline antibiotics containing N-methylurea moiety in the carbohydrate ring were obtained by the interaction of methyl isocyanate with daunorubicin, doxorubicin, carminomycin and daunorubicin derivatives, substituted at C-13 or C-14 positions. N-Nitrosation of these compounds yielded modified anthracycline antibiotics containing the N-methyl-N-nitrosourea substituent at C-3' position. Alkaline degradation of these derivatives produced, through corresponding isocyanates cyclic 3'-N,4'-carbonylderivatives. In these anthracycline derivatives with sugar cycles conjugated with oxazoline-2-ones the predominant conformations of sugar ring has changed from 1C4 to 4C1, 2,5B, or B0,3 (shown by 1H NMR spectroscopy). It was demonstrated, both in vitro and in vivo, that introduction of methylurea or cytotoxic methylnitrosourea moieties does not potentiate antimicrobial, cytotoxic or antitumour properties of these compounds.