Therapeutic targeting of apoptosis pathways in cancer

Recent Advances in Anticancer Activity of Novel Plant Extracts and Compounds from Curcuma longa in Hepatocellular Carcinoma

PURPOSE

Among all forms of cancers, hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide. There are several treatment options for HCC ranging from loco-regional therapy to surgical treatment. Yet, there is high morbidity and mortality. Recent research focus has shifted towards more effective and less toxic cancer treatment options. Curcumin, the active ingredient in the Curcuma longa plant, has gained widespread attention in recent years because of its multifunctional properties as an antioxidant, anti-inflammatory, antimicrobial, and anticancer agent.

METHODS

A systematic search of PubMed, Embase and Google Scholar was performed for studies reporting incidence of HCC, risk factors associated with cirrhosis and experimental use of curcumin as an anti-cancer agent.

RESULTS

This review exclusively encompasses the anti-cancer properties of curcumin in HCC globally and it's postulated molecular targets of curcumin when used against liver cancers.

CONCLUSIONS

This review is concluded by presenting the current challenges and future perspectives of novel plant extracts derived from C. longa and the treatment options against cancers.

Determination of anticancer potential of a novel pharmacologically active thiosemicarbazone derivative in colorectal cancer cell lines

Thiosemicarbazones have received noteworthy attention due to their numerous pharmacological activities. Various thiosemicarbazone derivatives have been reported to play a key role as potential chemotherapeutic agents for the management of cancer. Herein, we aimed to establish the anticancer efficacy of novel thiosemicarbazone derivative C4 against colon cancer in vitro. The MTT viability assay identified C4 as a promising anticancer compound in a panel of cancer cell lines with the most potent activity against colon cancer cells. Further, anticancer potential of C4 was evaluated against HT-29 and SW620 colon cancer cell lines considering the factors like cell adhesion and migration, oxidative stress, cell cycle arrest, and apoptosis. Our results showed that C4 significantly inhibited the migration and adhesion of colon cancer cells. C4 significantly increased the intracellular reactive oxygen species (ROS) and induced apoptotic cell death. Cell cycle analysis revealed that C4 interfered in the cell cycle distribution and arrested the cells at the G2/M phase of the cell cycle. Consistent with these results C4 also down-regulated the Bcl-XL and Bcl-2 and up-regulated the caspase-3 expression. These findings introduced C4 as the potential anticancer agent against colon cancer.

Over Fifty Years of Life, Death, and Cannibalism: A Historical Recollection of Apoptosis and Autophagy

Research in biomedical sciences has changed dramatically over the past fifty years. There is no doubt that the discovery of apoptosis and autophagy as two highly synchronized and regulated mechanisms in cellular homeostasis are among the most important discoveries in these decades. Along with the advancement in molecular biology, identifying the genetic players in apoptosis and autophagy has shed light on our understanding of their function in physiological and pathological conditions. In this review, we first describe the history of key discoveries in apoptosis with a molecular insight and continue with apoptosis pathways and their regulation. We touch upon the role of apoptosis in human health and its malfunction in several diseases. We discuss the path to the morphological and molecular discovery of autophagy. Moreover, we dive deep into the precise regulation of autophagy and recent findings from basic research to clinical applications of autophagy modulation in human health and illnesses and the available therapies for many diseases caused by impaired autophagy. We conclude with the exciting crosstalk between apoptosis and autophagy, from the early discoveries to recent findings.

The Protective Role of Selenium Against AFB1-Induced Liver Apoptosis by Death Receptor Pathway in Broilers

Aflatoxin B1 (AFB₁) is the most toxic among the mycotoxins and causes detrimental health effects on the liver of human and animals. Selenium (Se) plays an important role in protection of various animal species against numerous notorious toxic agents. The present study is designed to explore the protective effects of Se against AFB₁-induced liver pathogenesis by the methods of histopathology, flow cytometry, quantitative real-time polymerase chain reaction (qRT-PCR), and biochemical analysis. A total of 312, 1-day-old healthy Cobb-500 broilers were randomly divided into four groups and fed with basal diet (control group), 0.6 mg/kg AFB₁ (AFB₁ group), 0.4 mg/kg Se (+ Se group), and 0.6 mg/kg AFB₁ + 0.4 mg/kg Se (AFB₁ + Se group) for 21 days, respectively. Our results showed that 0.4 mg/kg Se supplement in broiler's diets could alleviate the AFB₁-induced histological lesions in the liver. The apoptosis analysis by flow cytometry showed that 0.4 mg/kg Se ameliorated the AFB₁-induced apoptosis in the liver. Moreover, the mRNA expression levels of Fas, TNF-α, FAS-associated death domain, TNF receptor-associated death domain, TNF receptor-associated factor 2, caspase 10, caspase 8, B cell lymphoma 2, IκB kinase, X-linked inhibitor of apoptosis protein, caspase 9, and caspase 3 analyzed by qRT-PCR demonstrated that 0.4 mg/kg Se could relieve the impact caused by AFB₁ to these parameters. The biochemical analyses of activities of CAT, GSH-Px and SOD, hydroxyl ion scavenging and contents of MDA and GSH in liver cells also indicated that 0.4 mg/kg Se has positive effect on AFB₁-induced oxidative stress in the liver. In conclusion, Se could relieve AFB₁-induced apoptosis by the molecular regulation of death receptors pathway in the liver of broilers. The outcomes from the present study may lead to a better understanding of the nature of selenium's essentiality and its protective roles against AFB₁.

The ethanol extraction of prepared Psoralea corylifolia induces apoptosis and autophagy and alteres genes expression assayed by cDNA microarray in human prostate cancer PC-3 cells

Prostate cancer is the most common male reproductive system cancer. The prevalence of prostate cancer in Europe and the United States is higher than that in the Asian region. However, the treatment of prostate cancer remains unsatisfactory. Psoralea corylifolia has been used to cure this disease as Chinese medicine in the Asian region. In this study, we analyzed the components of ethanol extraction of unprepared and prepared P. corylifolia by HPLC. Psoralen and isopsoralen content from the prepared P. corylifolia is twofold higher than that from unprepared, so we use the prepared extraction in this study. However, the effects of the ethanol extraction of P. corylifolia (PCE) on PC-3 human prostate cancer cells remain unclear. PC-3 cells were treated with PCE for different time periods and cells were examined for cell morphological change and total viable cells by using contrast phase microscopy and flow cytometer, respectively. Results indicated that PCE induced cell morphological changes and cytotoxic effect in PC-3 cells in dose-dependent manners. PCE induced chromatin condensation of PC-3 cells dose-dependently. PCE also induced apoptosis and autophagy in PC-3 by western blotting and acridine orange (AO) staining, respectively. Furthermore, a complementary DNA microarray analysis demonstrated that PCE treatment led to 944 genes upregulation and 872 genes downregulation. For example, the DNA damage-associated gene DNA-damage-inducible transcript 3 (DDIT 3) had a 62.1-fold upregulation and CDK1 2.68-fold downregulation. The differential genes were classified according to the Gene Ontology. Furthermore, GeneGo software was used for the key genes involved and their possible interaction pathways. Those genes were affected by P. corylifolia, which provided information for the understanding of the antiprostate cancer mechanism at the genetic level and provide additional targets for the treatments of human prostate cancer.

Chemopreventive effects of some popular phytochemicals on human colon cancer: a review

The present review summarizes (1) the epidemiology and etiology of colon cancer, (2) generalized cancer chemoprotective mechanisms, and (3) the chemopreventive properties of some popular phytochemicals as well as some phytochemicals developed by our research group recently.

AG36 Inhibits Human Breast Cancer Cells Proliferation by Promotion of Apoptosis In vitro and In vivo

AG36 is the biotransformation product of triterpenoid saponin from Ardisia gigantifolia stapf. In this study, the antitumor activity and underlying molecular mechanisms of AG36 against human breast MCF-7, MDA-MB-231, and SK-BR-3 cancer cells were investigated. AG36 inhibited the viability of MCF-7, MDA-MB-231, and SK-BR-3 cells in a dose and time-dependent manner, with an IC₅₀ of approximately 0.73, 18.1, and 23.4 μM at 48 h, respectively. AG36 obviously induced apoptosis and G2/M arrest of all the three breast cancer cells. Moreover, AG36 decreased the protein expression of cycle regulatory proteins cyclin B1 or cyclin D1. In MCF-7 and MDA-MB-231 cells, AG36 strongly increased the cleaved caspase-3 and -8 protein expressions, while in SK-BR-3 cells, AG36 only increased the protein expression of cleaved caspase-3. In all the three breast cancer cells, the ratio of Bax/Bcl-2 and cytosolic cytochrome c content increased significantly compared with control group. The death receptor-related proteins Fas/FasL, TNFR1, and DR5 were detected by Western blot, it showed that different breast cancer cells activated the death receptor-mediated extrinsic caspase-8 pathway through different receptors. In addition, the caspase-8 inhibitor z-IETD-fmk could significantly block AG36-triggered MCF-7 cells apoptosis. The in vivo studies showed that AG36 significantly inhibited the growth of MCF-7 xenograft tumors in BALB/c nude mice comparing with control. In conclusion, AG36 inhibited MCF-7, MDA-MB-231, and SK-BR-3 cells proliferation by the intrinsic mitochondrial and the extrinsic death receptor pathways and AG36 might be a potential breast cancer therapeutic agent.

Cantharidin Induced Oral Squamous Cell Carcinoma Cell Apoptosis via the JNK-Regulated Mitochondria and Endoplasmic Reticulum Stress-Related Signaling Pathways

Oral cancer is a subtype of head and neck cancer which represents 2.65% of all human malignancies. Most of oral cancer is histopathologically diagnosed as oral squamous cell carcinoma (OSCC). OSCC is characterized by a high degree of local invasion and a high rate of metastasis to the cervical lymph nodes. How to prevention and treatment of OSCC is important and imperative. Here, we investigated the therapeutic effect and molecular mechanism of cantharidin, an active compound isolated from blister beetles, on OSCC in vitro. Results showed that cantharidin significantly decreased cell viability in human tongue squamous carcinoma-derived SAS, CAL-27, and SCC-4 cell lines. The further mechanistic studies were carried out in SAS cells. Cantharidin also significantly increased apoptosis-related signals, including caspase-9, caspase-7 and caspase-3 proteins. Besides, cantharidin decreased mitochondrial transmembrane potential (MMP) and induced cytochrome c and apoptosis inducing factor (AIF) release. Cantharidin also increased Bax, Bid, and Bak protein expressions and decreased Bcl-2 protein expression. Cantharidin could also increase the endoplasmic reticulum (ER) stress signals, including the expressions of phosphorylated eIF-2α and CHOP, but not Grp78 and Grp94. Furthermore, cantharidin reduced pro-caspase-12 protein expression. In signals of mitogen-activated protein kinases, cantharidin increased the phosphorylation of JNK, but not ERK and p38. Transfection of shRNA-JNK to OSCC cells effectively reversed the cantharidin-induced cell apoptotic signals, including the mitochondrial and ER stress-related signaling molecules. Taken together, these findings suggest that cantharidin induces apoptosis in OSCC cells via the JNK-regulated mitochondria and ER stress-related signaling pathways.

5‑bromo‑3‑(3‑hydroxyprop‑1‑ynyl)‑2H‑pyran‑2‑one induces apoptosis in T24 human bladder cancer cells through mitochondria-dependent signaling pathways

The present study was performed to investigate the effect of 5-bromo-3-(3-hydroxyprop-1-ynyl)-2H-pyran-2-one (BHP) on the induction of apoptosis and cell cycle arrest in T24 human bladder carcinoma cells. An MTT assay was used to investigate the inhibition of cell proliferation. Flow cytometry was used to observe alterations in the cell cycle, generation of reactive oxygen species (ROS), alterations in mitochondrial membrane potential (MMP) and induction of apoptosis in the T24 cells following BHP treatment. Western blot analysis was performed for the determination of expression levels of apoptotic proteins, and 4,6‑diamidino‑2‑phenylindole dihydrochloride staining was used to observe apoptosis and DNA damage. The results demonstrated that treatment of the bladder cancer cells with BHP enhanced the activation of caspases and increased the production of ROS. It also caused damage to DNA, reduced MMP, and increased the secretion of endonuclease G and apoptosis‑inducing factor from the mitochondria. The expression levels of cyclin E and cell division cycle 25C were reduced, whereas the expression levels of p21 and phosphorylated p53 were increased in the BHP‑treated cells. In addition, treatment with BHP caused cell cycle arrest at the G0/G1 phase, increased the expression levels of B cell lymphoma‑2 (Bcl‑2)‑associated X protein and poly(ADP‑ribose) polymerase, decreased the expression of Bcl‑2 and ultimately induced apoptosis of the T24 cells. Thus, BHP inhibited the proliferation of bladder cancer cells by inducing cell apoptosis through the mitochondrial pathway.

Gemcitabine impacts differentially on bladder and kidney cancer cells: distinct modulations in the expression patterns of apoptosis-related microRNAs and BCL2 family genes

Bladder and renal cancer are two representative cases of tumors that respond differentially to gemcitabine. Previous studies have shown that gemcitabine can trigger apoptosis in various cancer cells. Herein, we sought to investigate the impact of gemcitabine on the expression levels of the BCL2 family members BCL2, BAX, and BCL2L12 and the apoptosis-related microRNAs miR-182, miR-96, miR-145, and miR-16 in the human bladder and kidney cancer cell lines T24 and Caki-1, respectively. Cancer cells' viability as well as the IC50 doses of gemcitabine were estimated by the MTT assay, while the detection of cleaved PARP via Western blotting was used as an indicator of apoptosis. Furthermore, T24 and Caki-1 cells' ability to recover from treatment was also monitored. Two different highly sensitive quantitative real-time RT-PCR methodologies were developed in order to assess the expression levels of BCL2 family genes and microRNAs. Exposure of cancer cells to gemcitabine produced the IC50 values of 30 and 3 nM for Caki-1 and T24 cells, correspondingly, while cleaved PARP was detected only in Caki-1 cells. T24 cells demonstrated the ability to recover from gemcitabine treatment, whereas Caki-1 cells' recovery capability was dependent on the initial time of exposure. BCL2 and BAX were significantly modulated in treated Caki-1 cells. Instead, T24 cells exhibited alterations only in the latter, as well as in all studied microRNAs. Therefore, according to our data, bladder and renal cancer cells' response to gemcitabine is accompanied by distinct alterations in the expression levels of their apoptosis-related genes and microRNAs.

Hydroquinone analog 4-[(Tetrahydro-2H-pyran-2‑yl) oxy] phenol induces C26 colon cancer cell apoptosis and inhibits tumor growth in vivo

The 4[(Tetrahydro‑2H‑pyran‑2‑yl) oxy] phenol (XG‑d) hydroquinone analog, is found in Vaccinium vitis‑idaea  L. Although it is known for its antioxidant properties and high level of safety, its antitumor activity remains to be elucidated. In the present study, the anticancer effect of XG‑d was determined in vitro and in vivo. The cytotoxicity of XG‑d against C26 murine colon carcinoma cells was found to occur in a time‑ and concentration‑dependent manner, whereas little effect was observed in the two normal cell lines (HK‑2 and L02) investigated. Oral administration of XG‑d (100 mg/kg) had effects on the tumor growth of tumor‑bearing mice. Furthermore, marked apoptosis was observed using Hoechst 33258 staining and flow cytometric analysis with annexin V/propidium iodide double staining. XG‑d also downregulated the expression of B‑cell lymphoma 2 (Bcl‑2), increased the expression levels of Bcl‑2‑associated X protein and activated caspase‑9, caspase‑3 and poly(adenosine diphosphate‑ribose) polymerase. The present study demonstrated for the first time, to the best of our knowledge, that XG‑d inhibited cancer cell growth via the induction of apoptosis and was also able to inhibit tumor growth in vivo. These results demonstrated that XG‑d may be used as a potential natural agent for cancer therapy with low toxicity.

Apoptosis inducing lead compounds isolated from marine organisms of potential relevance in cancer treatment

Apoptosis is a critical defense mechanism against the formation and progression of cancer and exhibits distinct morphological and biochemical traits. Targeting apoptotic pathways becomes an intriguing strategy for the development of chemotherapeutic agents particularly if the process is selective to cancer cells. Marine natural products have become important sources in the discovery of antitumour drugs, especially when recent technological and methodological advances have increased the scope of investigations of marine organisms. A high number of individual compounds from diverse organisms have induced apoptosis in several tumour cell lines via a number of mechanisms. Here, we review the effects of selected marine natural products and their synthetic derivatives on apoptosis signalling pathways in association with their pharmacological properties. Providing an outlook into the future, we also examine the factors that contribute to new discoveries and the difficulties associated with translating marine-derived compounds into clinical trials.

Effect of a bispidinone analog on mitochondria‑mediated apoptosis in HeLa cells

The present study was carried out to investigate the effect of 2,4,6,8-tetraaryl-3,7-diazabicyclo[3.3.1]nonan-9-one (bispidinone) analogs on the in vitro growth of human cervical carcinoma (HeLa) cells. A series of 11 bispidinone analogs was synthesized with substituents, e.g., fluoro/methyl/ethyl/isopropyl/thiomethyl/methoxy groups, at various positions. These compounds were synthesized to identify which substituent and position induced the strongest cytotoxic effect in cancer cells. Among these synthetics, analog 9, which contains methoxy groups, had the most significant cytotoxic effect on HeLa cells, and its IC50 value was less than 13 µM. A WST-8 assay also showed that analog 9 inhibited the proliferation of HeLa cells. By using DNA content analysis, we found that analog 9 induced sub-G1 and G1 phase arrest in a time-dependent manner. A [3H]-thymidine incorporation assay suggested that analog 9 inhibited DNA replication in HeLa cells. On performing light microscopy, morphological changes such as cellular shrinkage and disruption, which are apoptotic features, were observed in HeLa cells. Annexin V/propidium iodide double staining and rhodamine-123 staining showed that analog 9 induced apoptosis and disrupted the intracellular mitochondrial membrane potential in HeLa cells. The western blot analysis results suggested that analog 9 induced mitochondria-mediated apoptosis. In addition, we have shown that analog 9 may play a role in the Fas signaling apoptotic pathway.

Saponin B, a novel cytostatic compound purified from Anemone taipaiensis, induces apoptosis in a human glioblastoma cell line

Glioblastoma multiforme (GBM) is one of the most common malignant brain tumors. Saponin B, a novel compound isolated from the medicinal plant, Anemone taipaiensis, has been found to have a strong time- and dose-dependent cytostatic effect on human glioma cells and to suppress the growth of U87MG GBM cells. In this study, we investigated whether saponin B induces the apoptosis of glioblastoma cells and examined the underlying mechanism(s) of action of saponin B. Saponin B significantly suppressed U87MG cell proliferation. Flow cytometric analysis of DNA in the U87MG cells confirmed that saponin B blocked the cell cycle at the S phase. Furthermore, treatment of the U87MG cells with saponin B induced chromatin condensation and led to the formation of apoptotic bodies, as observed under a fluorescence microscope, and Annexin V/PI assay further suggested that phosphatidylserine (PS) externalization was apparent at higher drug concentrations. Treatment with saponin B activated the receptor-mediated pathway of apoptosis, as western blot analysis revealed the activation of Fas-l. Saponin B increased the Bax and caspase-3 ratio and decreased the protein expression of Bcl-2. The results from the present study demonstrate that the novel compound, saponin B, effectively induces the apoptosis of GBM cells and inhibits glioma cell growth and survival. Therefore, saponin B may be a potential candidate for the development of novel cancer therapeutics with antitumor activity against gliomas.

Inonotus Obliquus Suppresses Proliferation of Colorectal Cancer Cells and Tumor Growth in Mice Models by Downregulation of β-Catenin/NF-κB-Signaling Pathways

Chaga mushroom (Inonotus obliquas) has been used as a folk remedy for several illnesses including gastrointestinal disorders. We recently reported the potent anti-inflammatory effect of chaga extract in experimental colitis. However, its effects on colorectal cancer (CRC) have not been clearly elucidated. We investigated the effects of an aqueous extract of Inonotus obliquus (IOAE) in vitro in HCT116 and DLD1 cell lines and in vivo for adenoma in APCMin/+ mice and colitis-associated colon cancer in AOM/DSS-treated mice. Results show that IOAE suppressed the proliferation of both cell lines, and inhibited the growth of intestinal polyps in APCMin/+ and colon tumors in AOM/DSS-treated mice. IOAE induced mitochondrial intrinsic pathway of apoptosis, autophagy, and S phase cell cycle arrest. IOAE suppressed the expression levels of iNOS and Cox-2 and mRNA levels of pro-inflammatory cytokines (IL-6, IL-1β, TNF-a and IFN-γ) in the intestine of mice models. IOAE suppressed the nuclear levels of β-catenin and inhibited its downstream targets (cyclin D1 and c-Myc) along with CRC oncogene CDK8. IOAE inhibited the expression of NF-κB at cytoplasmic and nuclear levels. Our results demonstrate that IOAE possess potent anti-inflammatory and anti-proliferative properties through downregulation of Wnt/β-catenin and NF-κB pathways. Considering recent anticancer approaches involving natural products with minimal side effects, we advocate that Inonotus obliquus could be a beneficial supplement in prevention of colorectal cancer.

Targeting cellular apoptotic pathway with peptides from marine organisms

Apoptosis is a critical defense mechanism against the formation and progression of cancer and exhibits distinct morphological and biochemical traits. Targeting apoptotic pathways becomes an intriguing strategy for the development of chemotherapeutic agents. Peptides from marine organisms have become important sources in the discovery of antitumor drugs, especially when modern technology makes it more and more feasible to collect organisms from seas. This primer summarizes several marine peptides, based on their effects on apoptotic signaling pathways, although most of these peptides have not yet been studied in depth for their mechanisms of action. Novel peptides that induce an apoptosis signal pathway are presented in association with their pharmacological properties.

Wedelolactone, a medicinal plant-derived coumestan, induces caspase-dependent apoptosis in prostate cancer cells via downregulation of PKCε without inhibiting Akt

Emerging studies indicate that metabolism of arachidonic acid through the 5-lipoxygenase (5-Lox) pathway plays a critical role in the survival of prostate cancer cells raising the possibility that 5-Lox can be targeted for an effective therapy of prostate cancer. Wedelolactone (WDL), a medicinal plant-derived natural compound, is known to inhibit 5-Lox activity in neutrophils. However, its effect on apoptosis in prostate cancer cells has not been addressed. Thus, we tested the effects of WDL on human prostate cancer cells in vitro. We observed that WDL kills both androgen-sensitive as well as androgen-independent prostate cancer cells in a dose-dependent manner by dramatically inducing apoptosis. We also found that WDL-induced apoptosis in prostate cancer cells is dependent on c-Jun N-terminal Kinase (c-JNK) and caspase-3. Interestingly, WDL triggers apoptosis in prostate cancer cells via downregulation of protein kinase Cε (PKCε), but without inhibition of Akt. WDL does not affect the viability of normal prostate epithelial cells (PrEC) at doses that kill prostate cancer cells, and WDL-induced apoptosis is effectively prevented by 5-oxoETE, a metabolite of 5-Lox (but not by 15-oxoETE, a metabolite of 15-Lox), suggesting that the apoptosis-inducing effect of WDL in prostate cancer cells is mediated via inhibition of 5-Lox activity. These findings indicate that WDL selectivity induces caspase-dependent apoptosis in prostate cancer cells via a novel mechanism involving inhibition of PKCε without affecting Akt and suggest that WDL may emerge as a novel therapeutic agent against clinical prostate cancer in human.

Targeting the inhibitor of apoptosis proteins as a novel therapeutic strategy in medulloblastoma

Medulloblastoma is the most common malignant brain tumor of childhood. Novel therapeutic strategies are urgently needed to overcome cytotoxic resistance. We hypothesized that antiapoptotic signals contribute to resistance and that treatment with proapoptotic agents could increase the efficacy of conventional therapies. A PCR array was used to assess the status of the apoptotic signaling pathway in medulloblastoma cells after treatment with cytotoxic chemotherapy. Treatment with cisplatin led to the upregulation of antiapoptotic signals, including inhibitor of apoptosis proteins (IAP), in medulloblastoma cells. We subsequently investigated the synergistic effect of a small-molecule IAP inhibitor, LBW242, in combination with cisplatin and/or radiotherapy in three human medulloblastoma cell lines and 5 short term primary patient medulloblastoma cultures. The addition of LBW242 to chemotherapy resulted in significantly increased antitumor activity with a similar effect observed in combination with radiotherapy. Measurement of caspase-8 and -9 activity indicated that the synergy resulted from induction of both the intrinsic and extrinsic apoptotic pathways. Apoptosis was confirmed by Annexin V staining and activation of caspases 3/7. Xenograft models were used to evaluate the mechanism of action and efficacy in vivo. The combination therapy significantly reduced the tumor burden in a medulloblastoma xenograft model and TUNEL analysis in a medulloblastoma orthograft confirmed in vivo induction of apoptosis. These findings support the strategy of targeting IAPs in combination with cytotoxic therapy as a novel treatment strategy for patients with medulloblastoma.

Structure-based design of potent Bcl-2/Bcl-xL inhibitors with strong in vivo antitumor activity

Bcl-2 and Bcl-xL are key apoptosis regulators and attractive cancer therapeutic targets. We have designed and optimized a class of small-molecule inhibitors of Bcl-2 and Bcl-xL containing a 4,5-diphenyl-1H-pyrrole-3-carboxylic acid core structure. A 1.4 Å resolution crystal structure of a lead compound, 12, complexed with Bcl-xL has provided a basis for our optimization. The most potent compounds, 14 and 15, bind to Bcl-2 and Bcl-xL with subnanomolar K(i) values and are potent antagonists of Bcl-2 and Bcl-xL in functional assays. Compounds 14 and 15 inhibit cell growth with low nanomolar IC(50) values in multiple small-cell lung cancer cell lines and induce robust apoptosis in cancer cells at concentrations as low as 10 nM. Compound 14 also achieves strong antitumor activity in an animal model of human cancer.

Norcantharidin triggers cell death and DNA damage through S-phase arrest and ROS-modulated apoptotic pathways in TSGH 8301 human urinary bladder carcinoma cells

Norcantharidin (NCTD) is one of the ingredients of blister beetles which have been used in Chinese medicine for a long time. The purpose of this study was to investigate the inhibitory effects of NCTD on TSGH 8301 human bladder cancer cells in vitro and the mechanisms through which it exerts its anticancer action. Cell morphological analysis was performed using a phase-contrast microscope. The percentage of viable cells, cell cycle distribution, sub-G1 phase (apoptosis), reactive oxygen species (ROS) production and the levels of mitochondrial membrane potential (∆Ψ(m)) were analyzed by flow cytometry. DNA condensation and damage were determined by DAPI staining and comet assay. Apoptosis-associated protein level changes in TSGH 8301 cells following exposure to NCTD were examined, measured and determined by western blotting. Analysis of protein translocation was conducted by immunostaining and confocal laser microscopy. The results indicated that NCTD promoted cytotoxic effects, including the induction of cell morphological changes and the decrease in the percentage of viability, the induction of S-phase arrest as well as sub-G1 phase (apoptosis) in TSGH 8301 cells. The activities of caspase-3 and -9 were upregulated following NCTD treatment. Western blotting indicated that NCTD upregulated Fas, FasL, Bax, Bid, cytochrome c, caspase-3, -8 and -9 that led to the induction of apoptosis through the Fas extrinsic pathway. Furthermore, NCTD induced AIF and Endo G that were released from mitochondria to induce apoptosis through the mitochondrial-independent pathway. NCTD upregulated ROS production, downregulated ∆Ψ(m) and ERK, JNK, p38 protein kinases in TSGH 8301 cells. These findings suggest that NCTD triggers apoptosis in TSGH 8301 human bladder cancer cells via the Fas receptor, activation of the caspse-8, -9 and -3, mitochondrial-dependent and -independent pathways. NCTD may be useful for developing new therapeutic regimens for the treatment of bladder cancer.

Design of Bcl-2 and Bcl-xL inhibitors with subnanomolar binding affinities based upon a new scaffold

Employing a structure-based strategy, we have designed a new class of potent small-molecule inhibitors of the anti-apoptotic proteins Bcl-2 and Bcl-xL. An initial lead compound with a new scaffold was designed based upon the crystal structure of Bcl-xL and U.S. Food and Drug Administration (FDA) approved drugs and was found to have an affinity of 100 μM for both Bcl-2 and Bcl-xL. Linking this weak lead to another weak-affinity fragment derived from Abbott's ABT-737 led to an improvement of the binding affinity by a factor of >10 000. Further optimization ultimately yielded compounds with subnanomolar binding affinities for both Bcl-2 and Bcl-xL and potent cellular activity. The best compound (21) binds to Bcl-xL and Bcl-2 with K(i) < 1 nM, inhibits cell growth in the H146 and H1417 small-cell lung cancer cell lines with IC(50) values of 60-90 nM, and induces robust cell death in the H146 cancer cell line at 30-100 nM.

Antitumor effects of emodin on LS1034 human colon cancer cells in vitro and in vivo: roles of apoptotic cell death and LS1034 tumor xenografts model

Emodin, an active natural anthraquinone derivative, is found in the roots and rhizomes of numerous Chinese medicinal herbs and exhibits anticancer effects on many types of human cancer cell lines. The aim of this study investigated that emodin induced apoptosis of human colon cancer cells (LS1034) in vitro and inhibited tumor nude mice xenografts bearing LS1034 in vivo. In in vitro study, emodin induced cell morphological changes, decreased the percentage of viability, induced G2/M phase arrest and increased ROS and Ca(2+) productions as well as loss of mitochondrial membrane potential (ΔΨ(m)) in LS1034 cells. Emodin-triggered apoptosis was also confirmed by DAPI staining and these effects are concentration-dependent. Western blot analysis indicated that the protein levels of cytochrome c, caspase-9 and the ratio of Bax/Bcl-2 were increased in LS1034 cells after emodin exposure. Emodin induced the productions of ROS and Ca(2+) release, and altered anti- and pro-apoptotic proteins, leading to mitochondrial dysfunction and activations of caspase-9 and caspase-3 for causing cell apoptosis. In in vivo study, emodin effectively suppressed tumor growth in tumor nude mice xenografts bearing LS1034. Overall, the potent in vitro and in vivo antitumor activities of emodin suggest that it might be developed for treatment of colon cancer in the future.

ADF/cofilin proteins translocate to mitochondria during apoptosis but are not generally required for cell death signaling

Non-muscle cofilin (n-cofilin) is a member of the ADF/cofilin family of actin depolymerizing proteins. Recent studies reported a mitochondrial translocation of n-cofilin during apoptosis. As these studies also revealed impaired cytochrome c release and a block in apoptosis upon small interfering RNA-mediated n-cofilin knockdown, n-cofilin was postulated to be essential for apoptosis induction. To elucidate the general importance of ADF/cofilin activity for apoptosis, we exposed mouse embryonic fibroblasts deficient for n-cofilin, ADF (actin depolymerizing factor), or all ADF/cofilin isoforms to well-characterized apoptosis inducers. Cytochrome c release, caspase-3 activation, and apoptotic chromatin condensation were unchanged in all mutant fibroblasts. Thus, we conclude that ADF/cofilin activity is not generally required for induction or progression of apoptosis in mammalian cells. Interestingly, mitochondrial association of ADF and n-cofilin during apoptosis was preceded by, and dependent on, actin that translocated by a yet unknown mechanism to mitochondria during cell death.

Antitumor peptides from marine organisms

The biodiversity of the marine environment and the associated chemical diversity constitute a practically unlimited resource of new antitumor agents in the field of the development of marine bioactive substances. In this review, the progress on studies of antitumor peptides from marine sources is provided. The biological properties and mechanisms of action of different marine peptides are described; information about their molecular diversity is also presented. Novel peptides that induce apoptosis signal pathway, affect the tubulin-microtubule equilibrium and inhibit angiogenesis are presented in association with their pharmacological properties. It is intended to provide useful information for further research in the fields of marine antitumor peptides.

Impact of anti-oxidant status and apoptosis on the induction phase of chemotherapy in childhood acute lymphoblastic leukemia

This study aimed to evaluate oxidative stress and apoptosis in childhood acute lymphoblastic leukemia (ALL) at diagnosis and their impact on outcome at the end of the induction phase. Our study included 50 newly diagnosed children with ALL. Evaluation of oxidative stresses (malondialdehyde and total anti-oxidant capacity) was made at diagnosis and at the end of the induction phase. Apoptosis level was determined by fluorometric terminal deoxynucleotidyl transferase dUTP nick end labeling system for patients at diagnosis and after 1 week of treatment. Our study showed that there was increased oxidative stress at diagnosis and after treatment with chemotherapy. Apoptosis index was higher after 1 week of treatment with chemotherapy when compared to its level at diagnosis.

A small-molecule IAP inhibitor overcomes resistance to cytotoxic therapies in malignant gliomas in vitro and in vivo

We tested the use of the small-molecule Inhibitor of Apoptosis Protein (IAP) inhibitor LBW242 in combination with the standard-of-care therapies of irradiation and temozolomide for malignant gliomas. In vitro assays demonstrated that LBW242 enhanced the cytotoxic activity of radiotherapy, and clonogenic assays showed that the combination therapy led to a synergistic anti-glioma effect in multiple cell lines. Neurosphere assays revealed that the combination of radiation and LBW242 led to a pro-apoptotic effect in these glioma-initiating cell-enriched assays, with a corresponding inhibition of primary tumor cell growth. Athymic mice bearing established human malignant glioma tumor xenografts treated with LBW242 plus radiation and temozolomide demonstrated a synergistic suppression of tumor growth. Taken together, these experiments show that the pro-apoptotic and anti-glioma effects of radiotherapy and chemotherapy can be enhanced by the addition of a small-molecule IAP inhibitor. These results are readily translatable to clinical trial and offer the potential for improved treatment outcomes for patients with glioma.

Anti-cancer effects of a novel compound HS-113 on cell growth, apoptosis, and angiogenesis in human hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is one of the most common malignancies, yet there have been no significant advances in effective therapeutics. In this study, HS-113 was synthesized as a novel compound, N-(5-(2-bromobenzyl) thiazole-2-yl) benzofuran-2-carboxamide and its cytotoxic activity and anti-cancer effect were examined in human HCC cells. HS-113 strongly suppressed growth of HCC cells in a dose-dependent manner, induced apoptosis by increasing the proportion of sub-G1 apoptotic cells, and caused cell cycle arrest at G0/G1 phase. Also, HS-113 increased the expression of p27 and decreased that of cyclin D1 associated with cell cycle arrest. Apoptosis by HS-113 was confirmed by DAPI and TUNEL staining, and the increases of the cleaved PARP and caspase-3 were observed. Furthermore, HS-113 decreased protein expression of HIF-1α and secretion of VEGF, and inhibited the tube formation of HUVECs. These results showed that HS-113 not only inhibited cell growth and angiogenesis, but also induced apoptosis of human HCC cells. We suggest that HS-113 may be a potential candidate for cancer therapy against HCC.

Kaempferol induced apoptosis via endoplasmic reticulum stress and mitochondria-dependent pathway in human osteosarcoma U-2 OS cells

Kaempferol is a natural flavonoid. Previous studies have reported that kaempferol has anti-proliferation activities and induces apoptosis in many cancer cell lines. However, there are no reports on human osteosarcoma. In this study, we investigate the anti-cancer effects and molecular mechanisms of kaempferol in human osteosarcoma cells. Our results demonstrate that kaempferol significantly reduces cell viabilities of U-2 OS, HOB and 143B cells, especially U-2 OS cells in a dose-dependent manner, but exerts low cytotoxicity on human fetal osteoblast progenitor hFOB cells. Comet assay, DAPI staining and DNA gel electrophoresis confirm the effects of DNA damage and apoptosis in U-2 OS cells. Flow cytometry detects the increase of cytoplasmic Ca(2+) levels and the decrease of mitochondria membrane potential. Western blotting and fluorogenic enzymatic assay show that kaempferol treatment influences the time-dependent expression of proteins involved in the endoplasmic reticulum stress pathway and mitochondrial signaling pathway. In addition, pretreating cells with caspase inhibitors, BAPTA or calpeptin before exposure to kaempferol increases cell viabilities. The anti-cancer effects of kaempferol in vivo are evaluated in BALB/c(nu/nu) mice inoculated with U-2 OS cells, and the results indicate inhibition of tumor growth. In conclusion, kaempferol inhibits human osteosarcoma cells in vivo and in vitro.

New biomarkers probing depth of cell senescence assessed by laser scanning cytometry

The imaging analytical capabilities of laser scanning cytometer (LSC) have been used to assess morphological features considered to be typical of the senescent phenotype. The characteristic “flattening” of senescent cells was reflected by the decline in the density of staining (intensity of maximal pixel) of DNA-associated fluorescence [4,6-diamidino-2-phenylindole (DAPI)] paralleled by an increase in nuclear size (area). The decrease in ratio of maximal pixel to nuclear area was even more sensitive senescence biomarker than the change in maximal pixel or nuclear area, each alone. The saturation cell density at plateau phase of growth recorded by LSC was found to be dramatically decreased in cultures of senescent cells, thereby also serving as an additional marker. The induction of cyclin dependent kinase inhibitors p21^WAF1 and p27^KIP1 and γH2AX and activation of ATM markers of DNA damage response were measured in parallel with DNA/DAPI maximal pixel and nuclear area. These biomarker indices were expressed in quantitative terms by reporting them as a fraction of the respective controls. The effect of treatment of A549 and WI-38 cells with different concentrations of mitoxantrone (Mxt) and trichostatin A for various time periods was studied to assess the degree (depth) of cell senescence. Also assessed was the effect of 2-deoxy-d-glucose, the agent attenuating metabolic cell activity, on the depth of senescence induced by Mxt. A relationship between the ability of cells to synthesize RNA (incorporate 5-ethynyluridine) that leads to growth imbalance and induction of cell senescence was also studied. The data show that morphometric analysis of cellular attributes by LSC offers an attractive tool to detect cell senescence and measure its degree particularly in assessing effects of the factors that enhance or attenuate this process. This methodology is of importance in light of the evidence that cellular senescence is not only a biological process that is fundamental for organismal aging but also impedes formation of induced-pluripotent stem cells providing the barrier for neoplastic transformation and is the major mechanism of induction of reproductive cell death during treatment of solid tumors. © 2010 International Society for Advancement of Cytometry.

Anti-apoptosis and cell survival: a review

Type I programmed cell death (PCD) or apoptosis is critical for cellular self-destruction for a variety of processes such as development or the prevention of oncogenic transformation. Alternative forms, including type II (autophagy) and type III (necrotic) represent the other major types of PCD that also serve to trigger cell death. PCD must be tightly controlled since disregulated cell death is involved in the development of a large number of different pathologies. To counter the multitude of processes that are capable of triggering death, cells have devised a large number of cellular processes that serve to prevent inappropriate or premature PCD. These cell survival strategies involve a myriad of coordinated and systematic physiological and genetic changes that serve to ward off death. Here we will discuss the different strategies that are used to prevent cell death and focus on illustrating that although anti-apoptosis and cellular survival serve to counteract PCD, they are nevertheless mechanistically distinct from the processes that regulate cell death.

Anticancer efficacy of a difluorodiarylidenyl piperidone (HO-3867) in human ovarian cancer cells and tumor xenografts

The purpose of this study was to evaluate the anticancer potency and mechanism of a novel difluorodiarylidenyl piperidone (H-4073) and its N-hydroxypyrroline modification (HO-3867) in human ovarian cancer. Studies were done using established human ovarian cancer cell lines (A2870, A2780cDDP, OV-4, SKOV3, PA-1, and OVCAR3) as well as in a murine xenograft tumor (A2780) model. Both compounds were comparably and significantly cytotoxic to A2780 cells. However, HO-3867 showed a preferential toxicity toward ovarian cancer cells while sparing healthy cells. HO-3867 induced G(2)-M cell cycle arrest in A2780 cells by modulating cell cycle regulatory molecules p53, p21, p27, cyclin-dependent kinase 2, and cyclin, and promoted apoptosis by caspase-8 and caspase-3 activation. It also caused an increase in the expression of functional Fas/CD95 and decreases in signal transducers and activators of transcription 3 (STAT3; Tyr705) and JAK1 phosphorylation. There was a significant reduction in STAT3 downstream target protein levels including Bcl-xL, Bcl-2, survivin, and vascular endothelial growth factor, suggesting that HO-3867 exposure disrupted the JAK/STAT3 signaling pathway. In addition, HO-3867 significantly inhibited the growth of the ovarian xenografted tumors in a dosage-dependent manner without any apparent toxicity. Western blot analysis of the xenograft tumor tissues showed that HO-3867 inhibited pSTAT3 (Tyr705 and Ser727) and JAK1 and increased apoptotic markers cleaved caspase-3 and poly ADP ribose polymerase. HO-3867 exhibited significant cytotoxicity toward ovarian cancer cells by inhibition of the JAK/STAT3 signaling pathway. The study suggested that HO-3867 may be useful as a safe and effective anticancer agent for ovarian cancer therapy.

Novel quinolone CHM-1 induces apoptosis and inhibits metastasis in a human osterogenic sarcoma cell line

Novel 2-phenyl-4-quinolone compounds have potent cytotoxic effects on different human cancer cell lines. In this study, we examined anticancer activity and mechanisms of 20-fluoro-6,7-methylenedioxy-2-phenyl-4-quinolone (CHM-1) in human osterogenic sarcoma U-2 OS cells. CHM-1-induced apoptosis was determined by flow cytometric analysis, DAPI staining, Comet assay, and caspase inhibitors. CHM-1-inhibited cell migration and invasion was assessed by a wound healing assay, gelatin zymography, and a Transwell assay. The mechanisms of CHM-1 effects on apoptosis and metastasis signaling pathways were studied using Western blotting and gene expression. CHM-1 induced G2/M arrest and apoptosis at an IC(50) (3 microM) in U-2 OS cells and caspase-3, -8, and -9 were activated. Caspase inhibitors increased cell viability after exposure to CHM-1. CHM-1-induced apoptosis was associated with enhanced ROS generation, DNA damage, decreased DeltaPsi(m) levels, and promotion of mitochondrial cytochrome c release. CHM-1 stimulated mRNA expression of caspase-3, -8, and -9, AIF, and Endo G. In addition, CHM-1 inhibited cell metastasis at a low concentration (<3 microM). CHM-1 inhibited the cell metastasis through the inhibition of MMP-2, -7, and -9. CHM-1 also decreased the levels of MAPK signaling pathways before leading to the inhibition of MMPs. In summary, CHM-1 is a potent inducer of apoptosis, which plays a role in the anticancer activity of CHM-1.