Design, synthesis, biological evaluation and molecular modeling studies of 1-aryl-6-(3,4,5-trimethoxyphenyl)-3(Z)-hexen-1,5-diynes as a new class of potent antitumor agents.

A series of novel enediyne-containing molecules, 1-aryl-6-(3,4,5-trimethoxyphenyl)-3(Z)-hexen-1,5-diynes, were synthesized and displayed significant IC50 values of 10(-7) to 10(-6) M against various cancer cell lines. Of these compounds, 1-(2-pyridinyl)-6-(3,4,5-trimethoxyphenyl)-3(Z)-hexen-1,5-diyne (8) demonstrated the greatest growth inhibition activity. Compound 8 also arrested cancer cells in the G2/M phase and induced apoptosis via activation of Caspase-3. In addition to the G2/M block, compound 8 caused microtubule depolymerization at low concentrations and markedly decreased tumor size in xenographic studies.

Synthesis and antitumor activity of cis-dichloridoplatinum(II) complexes of 1,1'-biisoquinolines.

A simple approach to 1,1',2,2',3,3',4,4'-octahydro-1,1'-biisoquinolines is described. Reaction of phenethylamines with oxalyl chloride led to N,N'-bis(phenethyl) oxamides (1). Cyclization of oxamides by using Bischler-Napieralski conditions gave 3,3',4,4'-tetrahydro-1,1'-biisoquinoline (3) and unusual products 2, 4, 5. Reduction of 3,3',4,4'-tetrahydro-1,1'-biisoquinolines with sodium boron hydride gave both rac-1,1',2,2',3,3',4,4'-octahydro-1,1'-biisoquinolines (6) and meso-1,1',2,2',3,3',4,4' -octahydro-1,1'-biisoquinolines (7). Compound 6 was resolved to (1S, 1S') (8) and (1R, 1R') (9) furtherly. By treating all the biisoquinolines with K2PtCl4 afforded their cis-dichloridoplatinum (II) complexes (12-18). The antitumor activity of these complexes was evaluated.

1-(2-((Z)-6-(2-(Trifluoromethyl)phenyl)hexa-3-en-1,5-diynyl)phenyl)piperidin-2-one as a new potent apoptosis agent.

Compounds 4a-f, 5a-f and 6-9, showed significant growth inhibition activity against human tumor cell lines. Of these compounds, 1-(2-((Z)-6-(2-(trifluoromethyl)phenyl)hexa-3-en-1,5-diynyl)phenyl)piperidin-2-one (8) displayed the most potent growth inhibition activity. Compound 8 also arrested cancer cells in G2/M phase and induced apoptosis via activation of caspase-3 and -9. According to western-blotting analysis, compound 8 can up-regulate Bax, down-regulate Bcl-2 and XIAP, as well as promote cytochrome c release.

Membrane-bound conformation and phospholipid components modulate membrane-damaging activity of Taiwan cobra cardiotoxins.

Membrane-damaging activity of Naja naja atra cardiotoxin 3 (CTX3) on 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC)/1,2-dimyristoyl-phosphatidic acid (DMPA) vesicles was approximately 3-fold that of N. naja atra cardiotoxin 4 (CTX4), while CTX3 and CTX4 displayed insignificantly permeabilizing activity in 1,2-dipalmitoyl-phosphatidylcholine (DPPC)/DMPA vesicles. Phospholipid-binding capability and oligomeric assembly upon binding with lipid vesicles did not closely correlate with membrane-damaging potency of CTX3 and CTX4. Geometrical arrangement of CTX3 in contact with POPC/DMPA vesicles was different from that noted with CTX4, and binding forces between CTX3 and POPC/DMPA were stronger than those between CTX4 and POPC/DMPA. Unlike POPC/DMPA, the interaction between CTXs and DPPC/DMPA was drastically reduced by increasing salt concentration. Color transformation of phospholipid/polydiacetylene membrane assay and FTIR spectra analyses revealed that CTX3 and CTX4 adopted different conformationsand modes upon absorption on POPC/DMPA and DPPC/DMPA vesicles. Taken together, our data show that, in addition to membrane packing density and phospholipid-binding capability, membrane-bound conformation of CTXs plays a vital role in displaying membrane-damaging activity.

Synthesis and antitumor activity of novel enediyne-linked pyrrolo[2,1-c][1,4]benzodiazepine hybrids.

A series of novel pyrrolo[2,1-c][1,4]benzodiazepine (PBD) hybrids linked with enediyne is described. These compounds were prepared by linking C-8 of DC-81 (1) with an enediyne (10-16) through carbon chain linkers to afford PBD hybrid agents 17-23 in good yields. Most of the hybrids on human cancer cell lines exhibited higher cytotoxicity, and an increase in the sub-G1 population than 1. In a previous article, we have demonstrated that DC-81-indole conjugate agents (3-6) are potent inducers of cell apoptosis in melanoma. In the present article, we investigated whether DC-81-enediyne agents possess more cytotoxicity than 6 on human 293T cells. Our data revealed that treatment of 293T cells with DC-81-enediyne resulted in a significant increase of annexin V binding, caspase-3 degradation, and p53 arrest to identify apoptotic cells than 6. These results suggest that the DC-81-enediyne agents are more efficient in inducing apoptosis than DC-81-indole in 293T cells.

Catalytic activity-independent pathway is involved in phospholipase A(2)-induced apoptotic death of human leukemia U937 cells via Ca(2+)-mediated p38 MAPK activation and mitochondrial depolarization.

In view of the controversial role of catalytic activity on the cytotoxicity of phospholipase A(2) (PLA(2)), the present study is conducted to explore whether PLA(2) induces apoptotic process of human leukemia U937 cells through catalytic activity-independent pathway. Modification of His-48 (according to the sequence alignment with porcine pancreatic PLA(2)) with p-bromophenacyl bromide (BPB) caused over 99.9% drop in enzymatic activity Naja naja atra PLA(2). It was found that BPB-PLA(2)-induced apoptotic death of U937 cells was associated with mitochondrial depolarization, modulation of Bcl-2 family members, cytochrome c release and activation of caspases 9 and 3. Upon exposure to BPB-PLA(2), elevation of intracellular Ca(2+) levels and p38 MAPK activation were observed in U937 cells. Pretreatment with BAPTA-AM (Ca(2+) chelator) and nifedipine (L-type Ca(2+) channel blocker) abrogated Ca(2+) increase and p38 MAPK activation, and rescued viability of BPB-PLA(2)-treated U937 cells. BPB-PLA(2)-induced dissipation of mitochondrial membrane potential and down-regulation of Bcl-2 were suppressed by SB202190 (p38MAPK inhibitor). Although PLA(2) mutants in which His-48 and Asp-49 were substituted by Ala and Lys, respectively, did not display detectable PLA(2) activity, they induced death of U937 cells. The signaling pathway of PLA(2) mutants in inducing cell death was indistinguishable from that of BPB-PLA(2). Taken together, our data indicate that catalytic activity-independent pathway is involved in PLA(2)-induced apoptotic death of human leukemia U937 cells via mitochondria-mediated death pathway triggering by Ca(2+)-mediated p38 MAPK activation.

Synthesis and biological evaluation of novel symmetry bis-enediynes.

A series of acyclic symmetry bis-enediynes have been synthesized successfully and their bioactivities were evaluated. Among them, 1,6-bis(4-((2-(pyridin-2-ylethynyl)phenyl)ethynyl)phenoxy)hexane 8g showed good inhibition activity against the CCRF-CEM (GI(50)=0.04 microM) and HL-60 (GI(50)=0.09 microM) cell lines of human leukemia. The cell cycle analysis shows that compound 8g arrests cell cycle via inhibiting Cyclin A and Cyclin B expressions in low concentration and induces a significant apoptosis progress in high concentration.

2-(6-aryl-3(Z)-hexen-1,5-diynyl)anilines as a new class of potent antitubulin agents.

Compounds 2a- h and 6 displayed significant GI 50 values of 10(-7)-10(-6) M against various cancer cell lines. Of these compounds, 2-(6-(2-trifluoromethylphenyl))-3(Z)-hexen-1,5-diynyl)aniline (2c) showed the most potent growth inhibition activity. Compound 2c also arrested cancer cells in the G2/M phase and in low concentration reduced a significant percentage of MDA-MB-231/ATCC breast cancer tetraploid cells. In addition to the G2/M block, compound 2c caused microtubule depolymerization and induced apoptosis via activation of the caspase family.

JNK and ERK mitogen-activated protein kinases mediate THDA-induced apoptosis in K562 cells.

2-(6-(2-thieanisyl)-3(Z)-hexen-1, 5-diynyl) aniline (THDA), an enediyne compound, was identified in our laboratory as a novel antineoplastic agent against human leukemia K562 cells. THDA-induced apoptosis was associated with the upregulation of Bax, downregulation of X-linked inhibitor of apoptosis (XIAP), as well as the activation of caspase-3 and caspase-9. In addition, the mitogen-activated protein family kinases, including c-Jun N-terminal kinase (JNK) and extracellular signal-regulated protein kinase (ERK) kinases, and the transcription factor c-Jun were all activated by phosphorylation after 6 h exposure to THDA. Phosphorylation (activation) of JNK and ERK kinases by THDA was blocked by an ERK inhibitor, PD98059, or a JNK inhibitor, JNK-1, respectively, suggesting that THDA-induced apoptosis in K562 cells is ERK and JNK dependent. Moreover, the blockade of ERK and JNK also attenuated the modulation of Bax and XIAP, as well as the activation of caspase-3 and caspase-9 induced by THDA. These findings suggest that the activation of JNK and ERK is involved in the THDA-induced apoptosis of K562 cells. Therefore, this investigation, for the first time, uncovered the biological properties of this novel antitumor enediyne.

Novel acyclic enediynes inhibit Cyclin A and Cdc25C expression and induce apoptosis phenomenon to show potent antitumor proliferation.

A series of acyclic enediynes showing significant inhibition on the growth of tumor cancer is disclosed. To investigate the structure-activity relationship, compounds 12-33 were synthesized. Among them, compound 17 showed most potent growth inhibition activity against all tumor cell lines at low concentration, such as SR (0.4microM) and MDA-MB-435 (0.8microM), and almost completely blocked cell cycle in G2/M phase via controlling Cyclin A and Cdc25C expression. On the other hand, compound 29 showed potent induced apoptosis activity by inducing activation of caspase-3, -8, and -9. Thus, this article disclosed a new multiple-protein regulator in cell cycle regulation and induced apoptosis to achieve the goal of anticancer drug.

Induction of G2/M phase arrest and apoptosis by a novel enediyne derivative, THDB, in chronic myeloid leukemia (HL-60) cells.

(Z)-2-(6-(Thieanisyl-2-yl)hexa-3-en-1,5-diynyl)benzenamine (THDB), an enediyne compound, was identified in our laboratory as a novel antineoplastic agent with broad spectrum of antitumor activities against many human cancer cells. THDB was found to inhibit the growth of HL-60 cells in a time-and dose-dependent manner. Cell cycle analysis showed G2/M phase arrest in HL-60 cells following 48 h exposure to THDB. Analysis of the cell cycle regulatory proteins demonstrated that THDB did not change the steady-state levels of cyclin B1, cyclin E, Cdk1 and Cdc25C, but decreased the protein levels of Cdk2 and cyclin A. THDB also caused a marked increase in apoptosis, as characterized by DNA fragmentation (DNA ladder and sub G1 formation), and poly (ADP-ribose) polymerase (PARP) cleavage, which was associated with activation of caspase-3, caspase-8 and caspase-9. Moreover, the THDB-induced apoptosis was significantly attenuated in the presence of specific inhibitors of caspase-3, -8 and -9. These molecular alterations provide an insight into THDB-caused growth inhibition, G2/M arrest and apoptotic death of HL-60 cells.

Synthesis and antitumor activity of cis-dichloroplatinum(II) complexes of 1-(2-aminophenyl)-1,2,3,4-tetrahydroisoquinolines.

Fifteen cis-dichloroplatinum complexes (5a-5o) were synthesized by treatment of 1-(2-aminophenyl)-1,2,3,4-THIQs (4a-4o) with K(2)PtCl(4). The antitumor activity of these compounds was examined against four different human tumor cell lines. Their structure-activity relationships for antitumor activity are reported. All of these compounds exhibited activity against MCF-7 cell line and showed good activity against WiDr cell line except 5c and 5f. On the other hand, compounds 5j and 5o are more active than the other compounds against Hepa59T/VGH cell line. The electron-donating group at the 6-position of isoquinoline ring seems to decrease the antitumor activity and the chloro substituent at the C-4 position of the aniline ring shown the highest potency. The "trans influence" dominates the control of the stability of [1-(2-aminophenyl)-1,2,3,4-THIQ]dichloroplatinums(II).

Induction of G2/M phase arrest and apoptosis by a novel enediyne derivative, THDA, in chronic myeloid leukemia (K562) cells.

We studied the effect of 2-(6-(2-thieanisyl)-3(Z)-hexen-1,5-diynyl)aniline(THDA), a newly developed anti-cancer agent, on cell proliferation, cell cycle progression, and induction of apoptosis in K562 cells. THDA was found to inhibit the growth of K562 cells in a time-and dose-dependent manner. Cell cycle analysis showed G2/M phase arrest and apoptosis in K562 cells following 24 h exposure to THDA. During the G2/M arrest, cyclin-dependent kinase inhibitors (CDKIs), p21 and p27 were increased in a time-dependent manner. Analysis of the cell cycle regulatory proteins demonstrated that THDA did not change the steady-state levels of cyclin B1, cyclin D3 and Cdc25C, but decreased the protein levels of Cdk1, Cdk2 and cyclin A. THDA also caused a marked increase in apoptosis, which was associated with activation of caspase-3 and proteolytic cleavage of poly (ADP-ribose) polymerase. These molecular alterations provide an insight into THDA-caused growth inhibition, G2/M arrest and apoptotic death of K562 cells.

Design, syntheses, and biological evaluations of squamostolide and its related analogs.

Squamostolide and its related analogs were designed and synthesized for biological evaluation. All these compounds were tested for growth inhibition activities against human tumor cell lines, in which one of the compounds showed the most potent cytotoxicity among these derivatives against a full panel of 60 human cancer cell lines. The same compound also showed G2/M phase arrest and a weak apoptotic effect during flow cytometric analysis.

Cytotoxicities, cell cycle and caspase evaluations of 1,6-diaryl-3(Z)-hexen-1,5-diynes, 2-(6-aryl-3(Z)-hexen-1,5-diynyl)anilines and their derivatives.

Compounds 3, 6-7, 9-10, 15-17, and 20-21 showed growth inhibition effects on a full panel of 60 human cancer cell lines, and most of the average IC50 values of the indicated analogues were from < 0.01 to 96.6 microM, in which analogues 16 and 17 revealed the highest cytotoxic activity with the cancer cell lines at 10(-7) M concentration range. During the cell cycle analysis, a moderate to high apoptotic progress induction was shown by 3, 9, 16-17, and 20 compared with the control, which 2-(6-(2-thienyl)-3(Z)-hexen-1,5-diynyl)aniline 16 showed the highest apoptotic effect. Structures 16-17 displayed a significant G2/M phase arrest in the cell growth cycle compared with other derivatives, which the proportions of the G2/M phase cells were accumulated to 71.5% and 82.6%, respectively. Moreover, the colorimetric assay of 16-17 also provided advanced evidence to the relationship between the compounds and the caspase-3 enzyme, which was one of the major promoters of apoptotic effect.

Synthesis of carbazoles via an intramolecular cyclization of 2-(6-substituted 3(Z)-hexen-1,5-diynyl)anilines and their related molecules.

Various 2-(6-substituted 3(Z)-hexen-1,5-diynyl)anilines 1a-g were treated with potassium tert-butoxide or potassium 3-ethylpentanoxide in NMP at 60 degrees C for 2 h to give the corresponding 5-substituted carbazoles 2a-g in 36-65% yields together with indoles 9a-g in 21-40% yields, respectively. Exposing the trifluoroacetamide analogues 10h-k under the same reaction conditions gave the carbazoles 2b-e in 37-57% yields and indoles 9b-e in 15-27% yields. Subsequent cyclizations of acetamide analogues 10a-g gave carbazoles 2a-g in 53-86% yields.

Remarkable G2/M phase arrest and apoptotic effect performed by 2-(6-aryl-3-hexen-1,5-diynyl) benzonitrile antitumor agents.

2-(6-aryl-3-hexen-1,5-diynyl)benzonitriles 3a-j showed growth inhibition effects on a full panel of 60 human cancer cell lines in low micro-concentrations, in which compounds 3c,d displayed a significant G2/M arrest in the cell growth cycle compared with other derivatives and an apoptotic progress induction were also shown by 3a-d.

A novel constituent from Rollinia mucosa, rollicosin, and a new approach to develop annonaceous acetogenins as potential antitumor agents.

Rollicosin (1), a new Annonaceous acetogenin, was isolated from the unripe fruits of Rollinia mucosa. Rollicosin (1) is the first compound of this type to contain lactone moieties on both sides of the aliphatic chain and to lack either tetrahydrofuran or tetrahydropyran rings. Its structure was determined on the basis of spectroscopic analyses. This compound may serve as a new prototype molecule to develop Annonaceous acetogenins as potential antitumor agents.

Bullatacin, a potent antitumor Annonaceous acetogenin, induces apoptosis through a reduction of intracellular cAMP and cGMP levels in human hepatoma 2.2.15 cells.

Bullatacin, a potential antitumor Annonaceous acetogenin (AA), is isolated from the seed of the Formosa Annona atemoya. We reported previously that bullatacin inhibits the secretion of hepatitis B surface antigen from 2.2.15 cells (human hepatoma HepG2 cells transfected with hepatitis B virus DNA plasmid). In the present study, we determined cell apoptosis by using double-dye staining with fluorescein-isothiocyanate-labeled annexin V and propidium iodide. We found that bullatacin induced apoptosis in 2.2.15 cells in a time-dependent manner; the most significant apoptotic change appeared at 16 hr. Moreover, different concentrations (10(-3) to 1.0 microM) of bullatacin induced apoptosis in a concentration-dependent manner at 16 hr. The determination of intracellular cyclic AMP (cAMP) and cyclic GMP (cGMP) levels in 2.2.15 cells after exposure to bullatacin demonstrated that bullatacin caused both to decrease in a time- and concentration-dependent manner. A time course (0.33, 1, 6, 16, 24hr) study indicated that while both cAMP and cGMP levels decreased early (at 0.33 hr), the most dramatic decline appeared at 6 hr. Meanwhile, the inhibitory effect on cAMP and cGMP levels reached a maximum at 16 hr (90.5+/-3.2 and 47.3+/-12.8%, respectively). The concentration-dependent decrease of both cAMP and cGMP induced by bullatacin was parallel with the magnitude of apoptosis induced by various concentrations (10(-3) to 1.0 microM) of bullatacin. Additionally, the bullatacin-induced apoptosis was inhibited by the addition of cAMP and cGMP elevating agents (forskolin and S-nitrosoglutathione). Our results suggest that a decrease of both cAMP and cGMP levels may play a crucial role in bullatacin-induced apoptosis in 2.2.15 cells.

New cytotoxic monotetrahydrofuran annonaceous acetogenins from Annona muricata.

Three new monotetrahydrofuran annonaceous acetogenins, muricin H (1), muricin I (2), and cis-annomontacin (3), along with five known acetogenins, annonacin, annonacinone, annomontacin, murisolin, and xylomaticin, were isolated from the seeds of Annona muricata. Additionally, two new monotetrahydrofuran annonaceous acetogenins, cis-corossolone (4) and annocatalin (5), together with four known ones, annonacin, annonacinone, solamin, and corossolone, were isolated from the leaves of this species. The structures of all new isolates were elucidated and characterized by spectral and chemical methods. These new acetogenins exhibited significant activity in in vitro cytotoxic assays against two human hepatoma cell lines, Hep G(2) and 2,2,15. Compound 5 showed a high selectivity toward the Hep 2,2,15 cell line.