Involvement of Akt in mitochondria-dependent apoptosis induced by a cdc25 phosphatase inhibitor naphthoquinone analog

Apoptotic Effects of a Thioether Analog of Vitamin K3 in a Human Leukemia Cell Line

Research suggests that thioether analogs of vitamin K₃ (VK₃) can act to preserve the phosphorylation of epidermal growth factor receptors by blocking enzymes (phosphatases) responsible for their dephosphorylation. Additionally, these derivatives can induce apoptosis via mitogen-activated protein kinase and caspase-3 activation, inducing reactive oxygen species (ROS) production, and apoptosis. However, vitamin K₁ exhibits only weak inhibition of phosphatase activity, while the ability of VK₃ to cause oxidative DNA damage has raised concerns about carcinogenicity. Hence, in the current study, we designed, synthesized, and screened a number of VK₃ analogs for their ability to enhance phosphorylation activity, without inducing off-target effects, such as DNA damage. 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay revealed that each analog produced a different level of cytotoxicity in the Jurkat human leukemia cell line; however, none elicited a cytotoxic effect that differed significantly from that of the control. Of the VK₃ analogs, CPD5 exhibited the lowest EC₅₀, and flow cytometry results showed that apoptosis was induced at final concentrations of ≥10 μM; hence, only 0.1, 1, and 10 μM were evaluated in subsequent assays. Furthermore, CPD5 did not cause vitamin K-attributed ROS generation and was found to be associated with a significant increase in caspase 3 expression, indicating that, of the synthesized thioether VK₃ analogs, CPD5 was a more potent inducer of apoptosis than VK₃. Hence, further elucidation of the apoptosis-inducing effect of CPD5 may reveal its efficacy in other neoplastic cells and its potential as a medication.

Investigation of the antimicrobial and anticancer activity of aminonaphthoquinones

In this study, we report on the inhibitory activity of synthesized aminonaphthoquinones against two bacterial and one fungal species to determine their antimicrobial properties. A minimum inhibitory concentration (MIC) of 7.8 μg/mL was obtained against the fungus, Candida albicans, which was better than that of Amphotericin B (MIC = 31.25 μg/mL). Escherichia coli (Gram -), was inhibited at a MIC of 23.4 μg/mL and Staphylococcus aureus (Gram +) at a MIC of 31.3 μg/mL. The aminonaphthoquinones were also screened against HCT116 colon, PC3 prostate and HepG2 liver cancer cell lines to evaluate their cytostatic effects. They had potent activity (GI₅₀  = 5.87-9.90 μM) which was about three-6-fold better than that of parthenolide (GI₅₀  = 25.97 μM) against the prostate cancer cell line. These compounds were generally more selective for cancer cells than for normal human lung fetal fibroblasts (WI-38).

Understanding cancer and the anticancer activities of naphthoquinones – a review

Naphthoquinone moieties are present in drugs such as doxorubicin which are used clinically to treat solid cancers.

A novel hydroxysuberamide derivative potentiates MG132-mediated anticancer activity against human hormone refractory prostate cancers--the role of histone deacetylase and endoplasmic reticulum stress

BACKGROUND

Histone deacetylase (HDAC) inhibitors are successful for treatment of advanced cutaneous T-cell lymphoma but only show modest effect in solid tumors. Approaches for HDAC inhibitors to improve activity against solid tumors are necessary.

METHODS

Sulforhodamine B assay and flow cytometric analysis detected cell proliferation and cell-cycle progression, respectively. Protein expression was determined by Western blotting. Comet assay and DNA end-binding activity of Ku proteins detected DNA damage and DNA repair activity, respectively. siRNA technique was used for knockdown of specific cellular target.

RESULTS

WJ25591 displayed inhibitory activity against HDAC1 and cell proliferation in human hormone-refractory prostate cancers PC-3 and DU-145. WJ25591 caused an arrest of cell-cycle at both G1- and G2-phase and increased protein expressions of p21 and cyclin E, followed by cell apoptosis. WJ25591-induced Bcl-2 down-regulation and activation of caspase-9, -8, and -3, suggesting apoptotic execution through both intrinsic and extrinsic apoptotic pathways. WJ25591 also significantly inhibited DNA repair activity but not directly induced DNA damage. Moreover, the proteasome inhibitor MG-132 dramatically sensitized WJ25591-induced cell apoptosis. The siRNA technique demonstrated that endoplasmic reticulum (ER) stress, in particular CHOP/GADD153 up-regulation, contributed to the synergistic effect.

CONCLUSIONS

The data suggest that WJ25591 inhibited HDAC activity, leading to cell-cycle arrest and inhibition of DNA repair. Caspase cascades are subsequently triggered to execute cell apoptosis. MG-132 dramatically sensitizes WJ25591-mediated apoptosis, at least partly, through ER stress response. The data also reveal that combination of HDAC inhibitors and proteasome inhibitors may be a potential strategy against hormone-refractory prostate cancers.

Ardisianone, a natural benzoquinone, efficiently induces apoptosis in human hormone-refractory prostate cancers through mitochondrial damage stress and survivin downregulation

BACKGROUND

Increasing evidence suggests that mitochondria play a central role in regulating cell apoptosis. Survivin, an inhibitor of apoptosis protein (IAP) family member, mediates resistance to cancer chemotherapy particularly in prostate cancers. Therefore, development of anticancer agents targeting mitochondria and survivin is a potential strategy.

METHOD

Cell proliferation was examined by sulforhodamine B, CFSE staining, and clonogenic assays. Mitochondrial membrane potential (ΔΨ(m) ) and reactive oxygen species (ROS) were detected by flow cytometric analysis. Protein expression was detected by Western blot. RNA levels were examined by reverse transcription polymerase chain reaction assay. Overexpression of constitutively active Akt was also used in this study.

RESULTS

Ardisianone, a natural benzoquinone derivative, displayed anti-proliferative and apoptotic activities against human hormone-refractory prostate cancer cells (HRPC), PC-3, and DU-145. Ardisianone dramatically induced mitochondrial damage, identified by downregulation of Bcl-2 family proteins, ROS production, and loss of ΔΨ(m) . Ardisianone also inhibited Akt and mTOR/p70S6K pathways and induced a fast downregulation of survivin, leading to activation of mitochondria-involved caspase cascades. Overexpression of constitutively active Akt partly rescued ardisianone-mediated apoptotic signaling cascades. Furthermore, a long-term treatment of ardisianone caused an increase of endoplasmic reticulum (ER) stress, upregulation of cIAP1 and cIAP2, and apoptosis-inducing factor (AIF)-mediated caspase-independent apoptosis.

CONCLUSIONS

The data suggest that the ardisianone induces apoptosis in human prostate cancers through mitochondrial damage stress, leading to the inhibition of mTOR/p70S6K pathway, downregulation of Bcl-2 family members, degradation of survivin, and activation of caspase cascades. The data provide evidence supporting that ardisianone is a potential anticancer agent against HRPCs.

Estrogen-induced reactive oxygen species-mediated signalings contribute to breast cancer

Elevated lifetime estrogen exposure is a major risk factor for breast cancer. Recent advances in the understanding of breast carcinogenesis clearly indicate that induction of estrogen receptor (ER) mediated signaling is not sufficient for the development of breast cancer. The underlying mechanisms of breast susceptibility to estrogen's carcinogenic effect remain elusive. Physiologically achievable concentrations of estrogen or estrogen metabolites have been shown to generate reactive oxygen species (ROS). Recent data implicated that these ROS induced DNA synthesis, increased phosphorylation of kinases, and activated transcription factors, e.g., AP-1, NRF1, E2F, NF-kB and CREB of non-genomic pathways which are responsive to both oxidants and estrogen. Estrogen-induced ROS by increasing genomic instability and by transducing signal through influencing redox sensitive transcription factors play important role (s) in cell transformation, cell cycle, migration and invasion of the breast cancer. The present review discusses emerging data in support of the role of estrogen induced ROS-mediated signaling pathways which may contribute in the development of breast cancer. It is envisioned that estrogen induced ROS mediated signaling is a key complementary mechanism that drives the carcinogenesis process. ROS mediated signaling however occurs in the context of other estrogen induced processes such as ER-mediated signaling and estrogen reactive metabolite-associated genotoxicity. Importantly, estrogen-induced ROS can function as independent reversible modifiers of phosphatases and activate kinases to trigger the transcription factors of downstream target genes which participate in cancer progression.

Induction of apoptosis by a stilbene analog involves Bax translocation regulated by p38 MAPK and Akt

trans-Stilbenes have been reported to induce cytochrome P450 1B1 (CYP1B1) inhibition and cell death, however, the molecular mechanisms of the effects are not fully understood. We report here that (1-(2-{3-[2-(2,4-dimethoxy-phenyl)-vinyl]-5-methoxy-phenoxy}ethyl)-1H-imidazole), a synthetic stilbene analog (SA) significantly suppressed TCDD-stimulated CYP1B1 mRNA expression. In HL-60 cells, SA induced apoptosis through activation of p38 MAPK and inactivation of Akt, which in turn activated Bad and mitochondrial death signaling pathway, as evidenced by Bax translocation and cytochrome c release. Expression of dominant negative p38 MAPK or constitutively active Akt significantly prevented cell death and mitochondrial Bax translocation, implicating that p38 MAPK and Akt signaling pathways play crucial roles in stilbene-induced apoptosis of HL-60 cells. These results suggest that SA induces apoptotic cell death as well as CYP1B1 inhibition and may thus be beneficial in cancer prevention.

Screening the active constituents of Chinese medicinal herbs as potent inhibitors of Cdc25 tyrosine phosphatase, an activator of the mitosis-inducing p34cdc2 kinase

OBJECTIVE

To screen and evaluate the active constituents of Chinese medicinal herbs as potent inhibitors of Cdc25 phosphatase.

METHODS

The affinity chromatography purified glutashione-S-transferase/Cdc25A phosphatase fusion protein and Cdc2/cyclin B from the extracts of starfish M phase oocytes are used as the cell cycle-specific targets for screening the antimitotic constituents. We tested 9 extracts isolated from the Chinese medicinal herbs and vegetables including the agents currently used in cancer treatment by measuring the inhibition of Cdc25A phosphatase and Cdc2 kinase activity. The antitumor activity of the extracts was also evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and flow cytometry.

RESULTS

Cdc25A inhibitory activity and antitumor activity are detected in the extracts isolated from three Chinese medicinal herbs Agrimona pilosa; Herba solani lyrati; Galla chinesis.

CONCLUSION

We found three extracts isolated from Chinese medicinal herbs have potential inhibitory activity of Cdc25 phosphatase using a highly specific mechanism-based screen assay for antimitotic drug discovery.

Elucidation of structure–activity relationships for 2- or 6-substituted-5,8-dimethoxy-1,4-naphthoquinones

1,4-Naphthoquinones have already been recognized to possess a wide range of biological activities. We have developed quantitative structure activity relationships (QSAR) for different series of 2- or 6-substituted-5,8-dimethoxy-1,4-naphthoquinones to understand the chemical-biological interaction governing antiproliferative/cytotoxic activities against L1210 cells. QSAR results have shown that these activities of 2- or 6-substituted-5,8-dimethoxy-1,4-naphthoquinones depend largely on their hydrophobicity.