Isokotomolide A, a new butanolide extracted from the leaves of Cinnamomum kotoense, arrests cell cycle progression and induces apoptosis through the induction of p53/p21 and the initiation of mitochondrial system in human non-small cell lung cancer A549 cells

MDM2: current research status and prospects of tumor treatment

Mousedouble minute 2 (MDM2) is one of the molecules activated by p53 and plays an important role in the regulation of p53. MDM2 is generally believed to function as a negative regulator of p53 by facilitating its ubiquitination and subsequent degradation. Consequently, blocked p53 activity often fails in damaged cells to undergo cell cycle arrest or apoptosis. Given that around 50% of human cancers involve the inactivation of p53 through genetic mutations, and directly targeting p53 through drug development has limited feasibility, targeting molecular regulation related to p53 has great potential and has become a research hotspot. For example, developing drugs that target the interaction between p53 and MDM2. Such drugs aim to reactivate p53 by targeting either MDM2 binding or p53 phosphorylation. Researchers have identified various compounds that can serve as inhibitors, either by directly binding to MDM2 or by modifying p53 through phosphorylation. Furthermore, a significant correlation exists between the expression of MDM2 in tumors and the effectiveness of immunotherapy, predominantly in the context of immune checkpoint inhibition. This review presents a comprehensive overview of the molecular characteristics of MDM2 and the current state of research on MDM2-targeting inhibitors. It includes a review of the impact of MDM2 targeting on the efficacy of immunotherapy, providing guidance and direction for the development of drugs targeting the p53-MDM2 interaction and optimization of immunotherapy.

Therapeutics Targeting p53-MDM2 Interaction to Induce Cancer Cell Death

Named as the guardian of the genome, p53 is a tumor suppressor that regulates cell function, often through many different mechanisms such as DNA repair, apoptosis, cell cycle arrest, senescence, metabolism, and autophagy. One of the genes that p53 activates is MDM2, which forms a negative feedback loop since MDM2 induces the degradation of p53. When p53 activity is inhibited, damaged cells do not undergo cell cycle arrest or apoptosis. As 50% of human cancers inactivate p53 by mutation, current research focuses on reactivating p53 by developing drugs that target the p53-MDM2 interaction, which includes the binding of MDM2 and phosphorylation of p53. The objective of this article is to provide a short list and description of p53-MDM2 antagonists that may be excellent candidates for inducing cancer cell death. Relevant articles were searched for and identified using online databases such as PubMed and ScienceDirect. Increasing p53 levels, by targeting the p53-MDM2 interaction, can help p53 play its role as a tumor suppressor and induce cancer cell death. Researchers have identified different compounds that can act as inhibitors, either by directly binding to MDM2 or by modifying p53 with phosphorylation. The results associated with the drugs demonstrate the importance of targeting such interactions to inhibit cancer cell growth, which indicates that the use of the compounds may improve cancer therapeutics.

Interaction of obtusilactone B and related butanolide lactones with the barrier-to-autointegration factor 1 (BAF1). A computational study

The barrier-to-autointegration factor 1 (BAF1) protein is a DNA-binding protein implicated in nuclear envelop repair and reformation after mitosis. This nuclear protein is frequently overexpressed in cancer cells and plays a role in the occurrence and development of different tumors. It is a potential therapeutic target for gastric cancer, breast cancer and other malignancies. For this reason, BAF1 inhibitors are searched. The butanolide lactone obtusilactone B (Ob-B) has been found to inhibit VRK1-dependent phosphorylation of BAF1, upon direct binding to the nuclear protein. Taking advantage of the known crystallographic structure of BAF1, we have elaborated molecular models of Ob-B bound to BAF1 to delimit the binding site and binding configuration. The long endoolefinic alkyl side chain of Ob-B extends into a small groove on the protein surface, and the adjacent exomethylene-γ-lactone moiety occupies a pocket comprising to the Ser-4 phosphorylation site of BAF1. Twenty butanolide lactones structurally close to ObB were screened for BAF1 binding. Several natural products with BAF1-binding capacity potentially superior to Ob-B were identified, including mahubanolide, kotomolide B, epilitsenolide D2, and a few other known anticancer plant natural products. Our study provides new ideas to guide the discovery and design of BAF1 inhibitors.

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Obtusilactone B (Ob-B) is an anticancer inhibitor of VRK1-mediated BAF1 phosphorylation.

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Molecular models of Ob-B bound to BAF1 have been constructed and the binding site determined.

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Screening of 20 butanolide lactones led to the identification of new potential BAF1 binders.

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Mahubanolide, kotomolide B and epilitsenolide D2 emerge as potential BAF1 inhibitors.

Isokotomolide A from Cinnamomum kotoense Induce Melanoma Autophagy and Apoptosis In Vivo and In Vitro

Melanoma is an aggressive cancer with high lethality. In order to find new anticancer agents, isokotomolide A (Iso A) and secokotomolide A (Sec A) isolated from Cinnamomum kotoense were identified to be potential bioactive agents against human melanoma but without strong antioxidative properties. Cell proliferation assay displayed Iso A and Sec A treated in the normal human skin cells showed high viabilities. It also verified that two of them possess strong antimelanoma effect in concentration-dependent manners, especially on B16F10, A2058, MeWo, and A375 cells. Wound healing assay presented their excellent antimigratory effects. Through 3-N,3-N,6-N,6-N-Tetramethylacridine-3,6-diamine (acridine orange, AO) staining and Western blot, the autophagy induced by treatment was confirmed, including autophagy-related proteins (Atgs). By using annexin V–FITC/PI double-stain, the apoptosis was confirmed, and both components also triggered the cell cycle arrest and DNA damage. We demonstrated the correlations between the mitogen-activated protein kinase (MAPK) pathway and antimelanoma, such as caspase cascade activations. To further evaluate in vivo experiments, the inhibition of tumor cell growth was verified through the histopathological staining in a xenograft model. In this study, it was confirmed that Iso A and Sec A can encourage melanoma cell death via early autophagy and late apoptosis processes.

Phytochemical Investigation and Anti-Inflammatory Activity of the Leaves of Machilus japonica var. kusanoi

In a series of anti-inflammatory screenings of lauraceous plants, the methanolic extract of the leaves of Machilus japonica var. kusanoi (Hayata) J.C. Liao showed potent inhibition on both superoxide anion generation and elastase release in human neutrophils. Bioassay-guided fractionation of the leaves of M. japonica var. kusanoi led to the isolation of twenty compounds, including six new butanolides, machinolides A–F (1–6), and fourteen known compounds (7–20). Their structures were characterized by 1D and 2D NMR, UV, IR, CD, and MS data. The absolute configuration of the new compounds were unambiguously confirmed by single-crystal X-ray diffraction analyses (1, 2, and 3) and Mosher’s method (4, 5, and 6). In addition, lignans, (+)-eudesmin (11), (+)-methylpiperitol (12), (+)-pinoresinol (13), and (+)-galbelgin (16) exhibited inhibitory effects on N-formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLP/CB)-induced superoxide anion generation in human neutrophils with IC₅₀ values of 8.71 ± 0.74 μM, 2.23 ± 0.92 μM, 6.81 ± 1.07 μM, and 7.15 ± 2.26 μM, respectively. The results revealed the anti-inflammatory potentials of Formosan Machilus japonica var. kusanoi.

A balancing act: using small molecules for therapeutic intervention of the p53 pathway in cancer

Small molecules targeting various aspects of the p53 protein pathway have shown significant promise in the treatment of a number of cancer types.

The complete chloroplast genome sequence of Cinnamomum kotoense

The first complete chloroplast genome (cpDNA) sequence of Cinnamomum kotoense was determined from Illumina HiSeq pair-end sequencing data in this study. The cpDNA is 154,010 bp in length, contains a large single copy region (LSC) of 93,676 bp and a small single copy region (SSC) of 18,830 bp, which were separated by a pair of inverted repeats (IR) regions of 20,752 bp. The genome contains 127 genes, including 82 protein-coding genes, 8 ribosomal RNA genes, and 36 transfer RNA genes. The overall GC content of the whole genome is 39.2%, and the corresponding values of the LSC, SSC, and IR regions are 37.9%, 33.9%, and 44.3%, respectively. Further phylogenomic analysis showed that C. kotoense and Cinnamomum bodinieri clustered in a clade in Cinnamomum genus.

Furanone derivative and sesquiterpene from Antarctic marine-derived fungus Penicillium sp. S-1-18

A new furanone derivative, butanolide A (1), and a new sesquiterpene, guignarderemophilane F (2), together with six known compounds, were isolated from the fungus Penicillium sp. S-1-18 derived from Antarctic marine. The new structures were determined by spectroscopic studies such as 1D- and 2D-NMR and MS analyses. The absolute configuration of 1 was determined by the modified Mosher's method, while the absolute configuration of 2 was determined by calculated ECD spectroscopy. The isolated secondary metabolites were evaluated for their protein tyrosine phosphatase 1B (PTP1B) inhibitory activity. Compound 1 showed moderate inhibitory activity against PTP1B with IC₅₀ value of 27.4 μM.

Natural products targeting the p53-MDM2 pathway and mutant p53: Recent advances and implications in cancer medicine

The p53 tumor suppressor plays a major role in controlling the initiation and development of cancer by regulating cell cycle arrest, apoptosis, senescence, and DNA repair. The MDM2 oncogene is a major negative regulator of p53 that inhibits the activity of p53 and reduces its protein stability. MDM2, p53, and the p53-MDM2 pathway represent well-documented targets for preventing and/or treating cancer. Natural products, especially those from medicinal and food plants, are a rich source for the discovery and development of novel therapeutic and preventive agents against human cancers. Many natural product-derived MDM2 inhibitors have shown potent efficacy against various human cancers. In contrast to synthetic small-molecule MDM2 inhibitors, the majority of which have been designed to inhibit MDM2-p53 binding and activate p53, many natural product inhibitors directly decrease MDM2 expression and/or MDM2 stability, exerting their anticancer activity in both p53-dependent and p53-independent manners. More recently, several natural products have been reported to target mutant p53 in cancer. Therefore, identification of natural products targeting MDM2, mutant p53, and the p53-MDM2 pathway can provide a promising strategy for the development of novel cancer chemopreventive and chemotherapeutic agents. In this review, we focus our discussion on the recent advances in the discovery and development of anticancer natural products that target the p53-MDM2 pathway, emphasizing several emerging issues, such as the efficacy, mechanism of action, and specificity of these natural products.

Discovery and synthesis of novel magnolol derivatives with potent anticancer activity in non-small cell lung cancer

EGFR T790 M accounts for 50% to 60% of cases of non-small-cell lung carcinoma (NSCLC) resistance to the first-generation EGFR tyrosine kinase inhibitors (TKIs). Hence, identifying novel compounds with activity against TKIs resistant is of great value. In this study, twenty honokiol and magnolol derivatives were isolated from the EtOH extract of Magnolia officinalis and the antiproliferative activity was evaluated on HCC827 (19del EGFR mutation), H1975 (L858 R/T790 M EGFR mutation), and H460 (KRAS mutation) cell lines. Among the isolated compounds, piperitylmagnolol (a 3-substituted magnolol derivative) showed the best antiproliferative activity against those three cell lines with the IC₅₀ values of 15.85, 15.60 and 18.60 μM, respectively, which provided a direction for the structural modification of magnolol. Further structural modification led to the synthesis of thirty-one magnolol derivatives, and compounds A13, C1, and C2 exhibited significant and broad-spectrum antiproliferative activity with the IC₅₀ values ranging from 4.81 to 13.54 μM, which were approximately 4- and 8-fold more potent than those of honokiol and magnolol, respectively. Moreover, their aqueous solubility was remarkably improved with 12-, 400- and 10⁵ fold greater than those of honokiol and magnolol. Anti-tumor mechanism research revealed that these three compounds were able to induce cell cycle arrest at G0/G1 phase, cause efficient apoptosis in H1975 cells, and also prevent the migration of HUVECs in a dose-dependent manner through Cdk2, Cdk4, Cyclin E, and Cyclin D1 inhibition as well as up-regulation of cleaved-PARP and cleaved-caspase 3 levels. In in vivo antitumor activity, C2 (10, 30 and 100 mg/kg, po) dose-dependently inhibited the tumor growth in H1975 xenograft model with the tumor inhibition rate of 46.3%, 59.3% and 61.2% respectively, suggesting that C2 is a potential oral anticancer agent deserving further investigation.

Cryptotanshinone induces cell cycle arrest and apoptosis through the JAK2/STAT3 and PI3K/Akt/NFκB pathways in cholangiocarcinoma cells

BACKGROUND

Cholangiocarcinoma (CCA) is the most common biliary tract malignancy in the world with high resistance to current chemotherapies and extremely poor prognosis. The main objective of this study was to investigate the inhibitory effects of cryptotanshinone (CTS), a natural compound isolated from Salvia miltiorrhiza Bunge, on CCA both in vitro and in vivo and to explore the underlying mechanisms of CTS-induced apoptosis and cell cycle arrest.

METHODS

The anti-tumor activity of CTS on HCCC-9810 and RBE cells was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay and colony forming assays. Cell cycle changes were detected by flow cytometric analysis. Apoptosis was detected by annexin V/propidium iodide double staining and Hoechst 33342 staining assays. The efficacy of CTS in vivo was evaluated using a HCCC-9810 xenograft model in athymic nude mice. The expression of key proteins involved in cell apoptosis and signaling pathway in vitro was analyzed by Western blot analysis.

RESULTS

CTS induced potent growth inhibition, S-phase arrest, apoptosis, and colony-forming inhibition in HCCC-9810 and RBE cells in a dose-dependent manner. Intraperitoneal injection of CTS (0, 10, or 25 mg/kg) for 4 weeks significantly inhibited the growth of HCCC-9810 xenografts in athymic nude mice. CTS treatment induced S-phase arrest with a decrease of cyclin A1 and an increase of cyclin D1 protein level. Bcl-2 expression was downregulated remarkably, while Bax expression was increased after apoptosis occurred. Additionally, the activation of JAK2/STAT3 and PI3K/Akt/NFκB was significantly inhibited in CTS-treated CCA cells.

CONCLUSION

CTS induced CCA cell apoptosis by suppressing both the JAK2/STAT3 and PI3K/Akt/NFκB signaling pathways and altering the expression of Bcl-2/Bax family, which was regulated by these two signaling pathways. CTS may serve as a potential therapeutic agent for CCA.

Tenuifolide B from Cinnamomum tenuifolium Stem Selectively Inhibits Proliferation of Oral Cancer Cells via Apoptosis, ROS Generation, Mitochondrial Depolarization, and DNA Damage

The development of drugs that selectively kill oral cancer cells but are less harmful to normal cells still provide several challenges. In this study, the antioral cancer effects of tenuifolide B (TFB), extracted from the stem of the plant Cinnamomum tenuifolium are evaluated in terms of their effects on cancer cell viability, cell cycle analysis, apoptosis, oxidative stress, and DNA damage. Cell viability of oral cancer cells (Ca9-22 and CAL 27) was found to be significantly inhibited by TFB in a dose-responsive manner in terms of ATP assay, yielding IC₅₀ = 4.67 and 7.05 μM (24 h), but are less lethal to normal oral cells (HGF-1). Dose-responsive increases in subG1 populations as well as the intensities of flow cytometry-based annexin V/propidium iodide (PI) analysis and pancaspase activity suggested that apoptosis was inducible by TFB in these two types of oral cancer cells. Pretreatment with the apoptosis inhibitor (Z-VAD-FMK) reduced the annexin V intensity of these two TFB-treated oral cancer cells, suggesting that TFB induced apoptosis-mediated cell death to oral cancer cells. Cleaved-poly (ADP-ribose) polymerase (PARP) and cleaved-caspases 3, 8, and 9 were upregulated in these two TFB-treated oral cancer cells over time but less harmful for normal oral HGF-1 cells. Dose-responsive and time-dependent increases in reactive oxygen species (ROS) and decreases in mitochondrial membrane potential (MitoMP) in these two TFB-treated oral cancer cells suggest that TFB may generate oxidative stress as measured by flow cytometry. N-acetylcysteine (NAC) pretreatment reduced the TFB-induced ROS generation and further validated that ROS was relevant to TFB-induced cell death. Both flow cytometry and Western blotting demonstrated that the DNA double strand marker γH2AX dose-responsively increased in TFB-treated Ca9-22 cells and time-dependently increased in two TFB-treated oral cancer cells. Taken together, we infer that TFB can selectively inhibit cell proliferation of oral cancer cells through apoptosis, ROS generation, mitochondrial membrane depolarization, and DNA damage.

Chemical constituents and bioactivity of Formosan lauraceous plants

Taiwan is rich in lauraceous plants. A review of 197 references based on the chemical analysis and bioactivity of indigenous lauraceous plants carried out by native scientists from 1963 to 2014 has been compiled. About 303 new compounds and thousands of known compounds comprising alkaloids and non-alkaloids with diverse structures have been isolated or identified from indigenous plants belonging to the 11 lauraceous genera. The volatile components, however, have been excluded from this review. This review provides an overview of the past efforts of Taiwan scientists working on secondary metabolites and their bioactivity in native lauraceous plants. The potential of lauraceous plants worthy of further study is also noted. The contents will be helpful for the chemotaxonomy of Lauraceae and be of value for the development of native Formosan lauraceous plants.

LYG-202 exerts antitumor effect on PI3K/Akt signaling pathway in human breast cancer cells

In this study, we aimed to investigate the antitumor effect of LYG-202, a newly synthesized piperazine-substituted derivative of flavonoid on human breast cancer cells and illustrate the potential mechanisms. LYG-202 induced apoptosis in MCF-7, MDA-MB-231 and MDA-MB-435 cells. LYG-202 triggered the activation of mitochondrial apoptotic pathway through multiple steps: increasing Bax/Bcl-2 ratio, decreasing mitochondrial membrane potential (ΔΨ(m)), activating caspase-9 and caspase-3, inducing cleavage of poly(ADP-ribose) polymerase, cytochrome c release and apoptosis-inducing factor translocation. Furthermore, LYG-202 inhibited cell cycle progression at the G1/S transition via targeting Cyclin D, CDK4 and p21(Waf1/Cip1). Additionally, LYG-202 increased the generation of intracellular ROS. N-Acetyl cysteine, an antioxidant, reversed LYG-202-induced apoptosis suggesting that LYG-202 induces apoptosis by accelerating ROS generation. Further, we found that LYG-202 deactivated the PI3K/Akt pathway, activated Bad phosphorylation, increased Cyclin D and Bcl-xL expression, and inhibited NF-κB nuclear translocation. Activation of PI3K/Akt pathway by IGF-1 attenuated LYG-202-induced apoptosis and cell cycle arrest. Our in vivo study showed that LYG-202 exhibited a potential antitumor effect in nude mice inoculated with MCF-7 tumor through similar mechanisms identified in cultured cells. In summary, our results demonstrated that LYG-202 induced apoptosis and cell cycle arrest via targeting PI3K/Akt pathway, indicating that LYG-202 is a potential anticancer agent for breast cancer.

III-10, a newly synthesized flavonoid, induces cell apoptosis with the involvement of reactive oxygen species-mitochondria pathway in human hepatocellular carcinoma cells

Study of the mechanisms of apoptosis in tumor cells is an important field of tumor therapy and cancer molecular biology. We recently established that III-10, a new flavonoid with a pyrrolidinyl and a benzyl group substitution, exerted its anti-tumor effect via inducing differentiation of human U937 leukemia cells. In this study, we demonstrated that III-10 induced cell apoptosis in human hepatocellular carcinoma cells. The activation of caspase-3, caspase-9, and the increased expression ratio of Bax/Bcl-2 were detected in III-10-induced apoptosis. Z-VAD-FMK, a pan-caspase inhibitor, partly attenuated the apoptotic induction of III-10 on both HepG2 and BEL-7402 cells. Furthermore, the increase of intracellular reactive oxygen species levels and the reduction of mitochondria ΔΨm were also observed in BEL-7402 and HepG2 cells after the treatment of III-10. Pretreatment with NAC, a reactive oxygen species production inhibitor, partly attenuated the apoptosis induced by III-10 via blocking the reactive oxygen species generation. Our data also showed that III-10 induced the release of cytochrome c and AIF to cytosol followed after the reactive oxygen species accumulation. Moreover, the GSH levels and ATP generation were both inhibited after III-10 treatment. Besides, the MAPK, the downstream effect of reactive oxygen species accumulation including JNK could be activated by III-10, as well as the inactivation of ERK. Collectively, the generation of reactive oxygen species might play an crucial role in III-10-induced mitochondrial apoptosis pathway, provided more stubborn evidence for III-10 as a potent anticancer therapeutic candidate.

By downregulating Ku80, hsa-miR-526b suppresses non-small cell lung cancer

Ku80 is involved in DNA double-strand breaks (DSBs) repair. Ku80 is overexpressed in lung cancer tissues, yet, molecular mechanisms have not been examined. We identified that miRNA, hsa-miR-526b, is bound to the 3'-UTR of Ku80 mRNA, thus decreasing Ku80 expression in NSCLC cells. Hsa-miR-526b was downregulated in NSCLC tissues compared with corresponding non-tumorous tissues, and its expression was inversely correlated with Ku80 upregulation. Overexpression of Ku80 and downregulation of hsa-miR-526b were associated with poor clinical outcomes of NSCLC patients. Hsa-miR-526b suppressed NSCLC cell proliferation, clonogenicity, and induced cell cycle arrest and apoptosis. Hsa-miR-526b inhibited xenografts and orthotopic lung tumor growth. Further, Ku80 knockdown in NSCLC cells suppressed tumor properties in vitro and in vivo similar to hsa-miR-526b overexpression. In agreement, Ku80 restoration partially reversed cell cycle arrest and apoptosis induced by hsa-miR-526b in NSCLC cells in vitro and in vivo. In addition, hsa-miR-526b overexpression or Ku80 knockdown increased p53 and p21CIP1/WAF1 expression. These findings reveal that hsa-miR-526b is a potential target in cancer therapy.

Isophilippinolide A arrests cell cycle progression and induces apoptosis for anticancer inhibitory agents in human melanoma cells

Three new butanolides, isophilippinolide A, philippinolide A, and philippinolide B, and an amide, cinnaretamine, were isolated from the roots of Cinnamomum philippinense to be identified by spectroscopic analysis. Four isolated compounds were screened to examine their radical-scavenging ability, metal-chelating power, and ferric-reducing antioxidant power assay (FRAP). Cinnaretamine showed powerful antioxidative properties in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and a reducing activity; all compounds presented minor inhibition of metal-chelating capacities. The effects of anti-tyrosinase of C. philippinense constituents were determined by the level of the suppression of hydroxylation that turned from L-tyrosine to L-dopa through an in vitro mushroom tyrosinase assay, and all testing samples illustrated slight mushroom tyrosinase inhibitory properties. Isophilippinolide A exhibited inhibitory effectivenesses against the A375.S2 melanoma cell line in a cell viability assay at concentrations ranging from 0 to 200 μM for 24 h. Propidium iodide staining and flow cytometry analyses were applied to assess cell cycle accumulative distribution. It was discovered that isophilippinolide A caused sub-G1 phase accumulation in positive correlation for apoptosis to inhibit cell growth. Further investigation revealed that isophilippinolide A induced A375.S2 cells with an increase of caspase-dependent apoptotic proteins to trigger correlated pathway mechanisms according to Western blotting results. Finally, isophilippinolide A displayed only low cytotoxicities to human normal epidermal cells (melanocytes) and dermal cells (fibroblasts). Altogether, the results implied C. philippinense compounds could be considered functional ingredients in cosmetics, foods, and pharmaceutical products, particularly for their anticancer ability on human skin melanoma cells.

A novel homosesquiterpenoid from the stems of Cinnamomum burmanii

A novel homosesquiterpenoid, burmanol (1), along with 16 known compounds, including one triterpenoid, one quinol, two chlorophylls, two coumarins, two steroids, three lignans and five benzenoids were obtained from the stems of Cinnamomum burmanii (Lauraceae). The structures of these compounds were determined on the basis of spectroscopic analysis.

A new benzodioxocinone from the leaves of Cinnamomum tenuifolium

Investigation of the leaves' extract of Cinnamomum tenuifolium (Lauraceae) led to the isolation of one novel benzodioxocinone, 2,3-dihydro-6,6-dimethylbenzo-[b][1,5]dioxocin-4(6 H)-one (1). The structure was determined through in-depth spectroscopic and mass-spectrometric analyses. The antioxidant potential was evaluated using the following in vitro method: scavenging of 1,1-diphenyl-2-picrylhydrazyl radical. We also detected the anti-proliferative effect of 1 on human oral cancer cells and its IC(50) is 107.7 µM.

Amides from the Stems of Cinnamomum burmannii

A novel amide, cinnabutamine (1), along with five known amides, cinnaretamine (2), N-trans-caffeoyl-5-hydroxytyramine (3), N-trans-feruloyltyramine (4), N-trans-feruloyl-5-methoxytyramine (5) and N-cis-feruloyl-5-methoxytyramine (6), were isolated from the stems of Cinnamomum burmannii (Lauraceae). Their structures were characterized and identified by spectral analysis.

Honokiol arrests cell cycle, induces apoptosis, and potentiates the cytotoxic effect of gemcitabine in human pancreatic cancer cells

Survival rates for patients with pancreatic cancer are extremely poor due to its asymptomatic progression to advanced and metastatic stage for which current therapies remain largely ineffective. Therefore, novel therapeutic agents and treatment approaches are desired to improve the clinical outcome. In this study, we determined the effects of honokiol, a biologically active constituent of oriental medicinal herb Magnolia officinalis/grandiflora, on two pancreatic cancer cell lines, MiaPaCa and Panc1, alone and in combination with the standard chemotherapeutic drug, gemcitabine. Honokiol exerted growth inhibitory effects on both the pancreatic cancer cell lines by causing cell cycle arrest at G₁ phase and induction of apoptosis. At the molecular level, honokiol markedly decreased the expression of cyclins (D1 and E) and cyclin-dependent kinases (Cdk2 and Cdk4), and caused an increase in Cdk inhibitors, p21 and p27. Furthermore, honokiol treatment led to augmentation of Bax/Bcl-2 and Bax/Bcl-xL ratios to favor apoptosis in pancreatic cancer cells. These changes were accompanied by enhanced cytoplasmic accumulation of NF-κB with a concomitant decrease in nuclear fraction and reduced transcriptional activity of NF-κB responsive promoter. This was associated with decreased phosphorylation of inhibitor of kappa B alpha (IκB-α) causing its stabilization and thus increased cellular levels. Importantly, honokiol also potentiated the cytotoxic effects of gemcitabine, in part, by restricting the gemcitabine-induced nuclear accumulation of NF-κB in the treated pancreatic cancer cell lines. Altogether, these findings demonstrate, for the first time, the growth inhibitory effects of honokiol in pancreatic cancer and indicate its potential usefulness as a novel natural agent in prevention and therapy.

LYG-202 inhibits the proliferation of human colorectal carcinoma HCT-116 cells through induction of G1/S cell cycle arrest and apoptosis via p53 and p21(WAF1/Cip1) expression

We recently established that LYG-202, a new flavonoid with a piperazine substitution, exerts an anti-tumor effect in vivo and in vitro. In the present study, we demonstrate that LYG-202 induces G1/S phase arrest and apoptosis in human colorectal carcinoma HCT-116 cells. Data showed that the blockade of the cell cycle was associated with increased p21(WAF1/Cip1) and Rb levels and reduced expression of cyclin D1, cyclin E, and CDK4. Moreover, PARP cleavage, activation of caspase-3, caspase-8, and caspase-9, and an increased ratio of Bax/Bcl-2 were detected in LYG-202-induced apoptosis. Additionally, activation of p53 resulted in the up-regulation of its downstream targets PUMA and p21(WAF1/Cip1), as well as the down-regulation of its negative regulator MDM2, suggesting that the p53 pathway may play a crucial role in LYG-202-induced cell cycle arrest and apoptosis. Furthermore, siRNA knockdown of p53 attenuated the G1 cell cycle arrest and apoptosis induced by LYG-202, as the effects of LYG-202 on up-regulation of p21(WAF1/Cip1) and down-regulation of Bcl-2 and pro-caspase-3 were partly inhibited in p53 siRNA transfected cells compared with control siRNA transfected cells. Collectively, these data indicate that LYG-202 exerts its anti-tumor potency by activating the p53-p21 pathway for G1/S cell cycle arrest and apoptosis in colorectal cancer cells.

Reactive oxygen species in cancer

Elevated rates of reactive oxygen species (ROS) have been detected in almost all cancers, where they promote many aspects of tumour development and progression. However, tumour cells also express increased levels of antioxidant proteins to detoxify from ROS, suggesting that a delicate balance of intracellular ROS levels is required for cancer cell function. Further, the radical generated, the location of its generation, as well as the local concentration is important for the cellular functions of ROS in cancer. A challenge for novel therapeutic strategies will be the fine tuning of intracellular ROS signalling to effectively deprive cells from ROS-induced tumour promoting events, towards tipping the balance to ROS-induced apoptotic signalling. Alternatively, therapeutic antioxidants may prevent early events in tumour development, where ROS are important. However, to effectively target cancer cells specific ROS-sensing signalling pathways that mediate the diverse stress-regulated cellular functions need to be identified. This review discusses the generation of ROS within tumour cells, their detoxification, their cellular effects, as well as the major signalling cascades they utilize, but also provides an outlook on their modulation in therapeutics.

Cytotoxic compounds from the stems of Cinnamomum tenuifolium

Three new butanolides, tenuifolide A (1), isotenuifolide A (2), and tenuifolide B (3), a new secobutanolide, secotenuifolide A (4), and one new sesquiterpenoid, tenuifolin (5), along with 16 known compounds were isolated from the stems of Cinnamomum tenuifolium. Their structures were determined by spectroscopic analyses. Compound 4 was found to induce apoptotic-related DNA damage, increase sub-G1 cells, and inhibit the growth of human prostate cancer cells, DU145. In addition, treatment with 4 significantly increased intracellular H2O2 and/or peroxide. The results show that 4 induced (a) noticeable reduction of mitochondrial transmembrane potential (DeltaPsim); (b) significant increase in the ratio of cytochrome c concentration (cytosol/mitochondria); and (c) subsequent activation of caspase-9/caspase-3. Antiproliferation caused by 4 was found to markedly decrease when pretreated with caspase-9/caspase-3 inhibitor. In ROS scavenging, antioxidant, NADPH oxidase, and NO inhibitor studies, pretreatment of DU145 cells with either DPI, dexamethasone, L-NAME, or mannitol decreased 4-induced intracellular DCF fluorescence of ROS. These results suggest that an increase of H2O2 and/or peroxide by 4 is the initial apoptotic event and 4 has anticancer effects on DU145 cells.

Implications of endoplasmic reticulum stress, the unfolded protein response and apoptosis for molecular cancer therapy. Part II: targeting cell cycle events, caspases, NF-κB and the proteasome

BACKGROUND

Endoplasmic reticulum stress (ERS), the unfolded protein response (UPR) and apoptosis signal transduction pathways are fundamental to normal cellular homeostasis and survival, but are exploited by cancer cells to promote the cancer phenotype.

OBJECTIVE

Collateral activation of ERS and UPR role players impact on cell growth, cell cycle arrest or apoptosis, genomic stability, tumour initiation and progression, tumour aggressiveness and drug resistance. An understanding of these processes affords promising prospects for specific cancer drug targeting of the ERS, UPR and apoptotic pathways.

METHOD

This review (Part II of II) brings forward the latest developments relevant to the molecular connections among cell cycle regulators, caspases, NF-κB, and the proteasome with ERS and UPR signalling cascades, their functions in apoptosis induction, apoptosis resistance and oncogenesis, and how these relationships can be exploited for targeted cancer therapy.

CONCLUSION

Overall, ERS, the UPR and apoptosis signalling cascades (the molecular therapeutic targets) and the development of drugs that attack these targets signify a success story in cancer drug discovery, but a more reductionist approach is necessary to determine the precise molecular switches that turn on antiapoptotic and pro-apoptotic programmes.

Kotomolide A arrests cell cycle progression and induces apoptosis through the induction of ATM/p53 and the initiation of mitochondrial system in human non-small cell lung cancer A549 cells

This study first investigates the anticancer effect of kotomolide A (KTA) in human non-small cell lung cancer cells, A549. KTA has exhibited effective cell growth inhibition by inducing cancer cells to undergo G2/M phase arrest and apoptosis. Blockade of cell cycle was associated with increased the activation of ataxia telangiectasia-mutated (ATM). Activation of ATM by KTA phosphorylated p53 at Serine15, resulting in increased stability of p53 by decreasing p53 and murine double minute-2 (MDM2) interaction. In addition, KTA-mediated G2/M phase arrest also was associated with the decrease in the amounts of cyclinB1, cyclinA, Cdc2 and Cdc25C and increase in the phosphorylation of Chk2, Cdc25C and Cdc2. Specific ATM inhibitor, caffeine, significantly decreased KTA-mediated G2/M arrest by inhibiting the phosphorylation of p53 (Serine15) and Chk2. KTA treatment triggered the mitochondrial apoptotic pathway indicated by a change in Bax/Bcl-2 ratios, resulting in mitochondrial membrane potential loss and caspase-9 activation. Taken together, these results suggest a critical role for ATM and p53 in KTA-induced G2/M arrest and apoptosis of human non-small cell lung cancer cells.