Anticancer drug targets: cell cycle and checkpoint control

Withania somnifera Induces Cytotoxic and Cytostatic Effects on Human T Leukemia Cells

Cancer chemotherapy is characterized by an elevated intrinsic toxicity and the development of drug resistance. Thus, there is a compelling need for new intervention strategies with an improved therapeutic profile. Immunogenic cell death (ICD) represents an innovative anticancer strategy where dying cancer cells release damage-associated molecular patterns promoting tumor-specific immune responses. The roots of Withania somnifera (W. somnifera) are used in the Indian traditional medicine for their anti-inflammatory, immunomodulating, neuroprotective, and anticancer activities. The present study is designed to explore the antileukemic activity of the dimethyl sulfoxide extract obtained from the roots of W. somnifera (WE). We studied its cytostatic and cytotoxic activity, its ability to induce ICD, and its genotoxic potential on a human T-lymphoblastoid cell line by using different flow cytometric assays. Our results show that WE has a significant cytotoxic and cytostatic potential, and induces ICD. Its proapoptotic mechanism involves intracellular Ca²⁺ accumulation and the generation of reactive oxygen species. In our experimental conditions, the extract possesses a genotoxic potential. Since the use of Withania is suggested in different contexts including anti-infertility and osteoarthritis care, its genotoxicity should be carefully considered for an accurate assessment of its risk–benefit profile.

AA-PMe, a novel asiatic acid derivative, induces apoptosis and suppresses proliferation, migration, and invasion of gastric cancer cells

Asiatic acid (AA; 2α,3β,23-trihydroxyurs-12-ene-28-oic acid) is widely used for medicinal purposes in many Asian countries due to its various bioactivities. A series of AA derivatives has been synthesized in attempts to improve its therapeutic potencies. Herein we investigated the anti-tumor activities of N-(2α,3β,23-acetoxyurs-12-en-28-oyl)-l-proline methyl ester (AA-PMe), a novel AA derivative. AA-PMe exhibited a stronger anti-cancer activity than its parent compound AA. AA-PMe inhibited the proliferation of SGC7901 and HGC27 human gastric cancer cells in a dose-dependent manner but had no significant toxicity in human gastric mucosa epithelial cells (GES-1). AA-PMe induced cell cycle arrest in G₀/G₁ phase and blocked G₁-S transition, which correlated well with marked decreases in levels of cyclin D1, cyclin-dependent kinase CKD4, and phosphorylated retinoblastoma protein, and increase in cyclin-dependent kinase inhibitor P15. Further, AA-PMe induced apoptosis of human gastric cancer cells by affecting Bcl-2, Bax, c-Myc, and caspase-3. Moreover, AA-PMe suppressed the migration and invasion of human gastric cancer cells (SGC7901 and HGC27) cells by downregulating the expression of MMP-2 and MMP-9. Overall, this study investigated the potential anti-cancer activities of AA-PMe including inducing apoptosis and suppressing proliferation, migration and invasion of gastric cancer cells, as well as the underlying mechanisms, suggesting that AA-PMe is a promising anti-cancer drug candidate in gastric cancer therapy.

A systematic study on drug-response associated genes using baseline gene expressions of the Cancer Cell Line Encyclopedia

We have studied drug-response associated (DRA) gene expressions by applying a systems biology framework to the Cancer Cell Line Encyclopedia data. More than 4,000 genes are inferred to be DRA for at least one drug, while the number of DRA genes for each drug varies dramatically from almost 0 to 1,226. Functional enrichment analysis shows that the DRA genes are significantly enriched in genes associated with cell cycle and plasma membrane. Moreover, there might be two patterns of DRA genes between genders. There are significantly shared DRA genes between male and female for most drugs, while very little DRA genes tend to be shared between the two genders for a few drugs targeting sex-specific cancers (e.g., PD-0332991 for breast cancer and ovarian cancer). Our analyses also show substantial difference for DRA genes between young and old samples, suggesting the necessity of considering the age effects for personalized medicine in cancers. Lastly, differential module and key driver analyses confirm cell cycle related modules as top differential ones for drug sensitivity. The analyses also reveal the role of TSPO, TP53, and many other immune or cell cycle related genes as important key drivers for DRA network modules. These key drivers provide new drug targets to improve the sensitivity of cancer therapy.

Role of apoptosis-related miRNAs in resveratrol-induced breast cancer cell death

Breast cancer is the most frequently diagnosed cancer in women, and one of the leading causes of cancer-related deaths worldwide. Recent evidences indicate that dietary agents such as resveratrol may inhibit cancer progression through modulation of microRNAs (miRNAs). We demonstrate that resveratrol regulates apoptotic and cell cycle machinery in breast cancer cells by modulating key tumor-suppressive miRNAs including miR-125b-5p, miR-200c-3p, miR-409-3p, miR-122-5p and miR-542-3p. Resveratrol-mediated miRNA modulation regulates key anti-apoptotic and cell cycle proteins including Bcl-2, X-linked inhibitor of apoptosis protein and CDKs, which are critical for its activity. Modulating miRNAs with mimics or inhibitors further validated a key role for miR-542-3p in MCF-7 and miR-122-5p in MDA-MB-231 breast cancer cell death in response to resveratrol. In conclusion, this study reveals novel miRNAs modulated by resveratrol that have a key role in breast cancer cell death.

Goniothalamin induces cell cycle arrest and apoptosis in H400 human oral squamous cell carcinoma: A caspase-dependent mitochondrial-mediated pathway with downregulation of NF-κβ

Goniothalamin is a natural occurring styryl-lactone compound isolated from Goniothalamus macrophyllus. It had been demonstrated to process promising anticancer activity on various cancer cell lines. However, little study has been carried out on oral cancer. The aim of this study was to determine the cytotoxic effects of goniothalamin against H400 oral cancer cells and its underlying molecular pathways. Results from MTT assay demonstrated that goniothalamin exhibited selective cytotoxicity as well as inhibited cells growth of H400 in dose and time-dependent manner. This was achieved primarily via apoptosis where apoptotic bodies and membrane blebbing were observed using AO/PI and DAPI/Annexin V-FITC fluorescence double staining. In order to understand the apoptosis mechanisms induced by goniothalamin, apoptosis assessment based on mitochondrial membrane potential assay and cytochrome c enzyme-linked immunosorbent assay were carried out. Results demonstrated that the depolarization of mitochondrial transmembrane potential facilitated the release of mitochondrial cytochrome c into cytosol. Caspases assays revealed the activation of initiator caspase-9 and executioner caspase-3/7 in dose-dependent manners. This form of apoptosis was closely associated with the regulation on Bcl-2 family proteins, cell cycle arrest at S phase and inhibition of NF-κβ translocation from cytoplasm to nucleus. Conclusion, goniothalamin has the potential to act as an anticancer agent against human oral squamous cell carcinoma (H400 cells).

Enhanced Human Epidermal Growth Factor Receptor 2 Degradation in Breast Cancer Cells by Lysosome-Targeting Gold Nanoconstructs

This paper describes how gold nanoparticle nanoconstructs can enhance anticancer effects of lysosomal targeting aptamers in breast cancer cells. Nanoconstructs consisting of anti-HER2 aptamer (human epidermal growth factor receptor 2, HApt) densely grafted on gold nanostars (AuNS) first targeted HER2 and then were internalized via HER2-mediated endocytosis. As incubation time increased, the nanoconstruct complexes were found in vesicular structures, starting from early endosomes to lysosomes as visualized by confocal fluorescence and differential interference contrast microscopy. Within the target organelle, lysosomes, HER2 was degraded by enzymes at low pH, which resulted in apoptosis. At specific time points related to the doubling time of the cancer cells, we found that accumulation of HER2-HApt-AuNS complexes in lysosomes, lysosomal activity, and lysosomal degradation of HER2 were positively correlated. Increased HER2 degradation by HApt-AuNS triggered cell death and cell cycle arrest in the G0/G1 phase inhibition of cell proliferation. This work shows how a perceived disadvantage of nanoparticle-based therapeutics-the inability of nanoconstructs to escape from vesicles and thus induce a biological response-can be overcome by both targeting lysosomes and exploiting lysosomal degradation of the biomarkers.

Different effects of LDH-A inhibition by oxamate in non-small cell lung cancer cells

Higher rate of glycolysis has been long observed in cancer cells, as a vital enzyme in glycolysis, lactate dehydrogenase A (LDH-A) has been shown with great potential as an anti-cancer target. Accumulating evidence indicates that inhibition of LDH-A induces apoptosis mediated by oxidative stress in cancer cells. To date, it's still unclear that whether autophagy can be induced by LDH-A inhibition. Here, we investigated the effects of oxamate, one classic inhibitor of LDH-A in non-small cell lung cancer (NSCLC) cells as well as normal lung epithelial cells. The results showed that oxamate significantly suppressed the proliferation of NSCLC cells, while it exerted a much lower toxicity in normal cells. As previous studies reported, LDH-A inhibition resulted in ATP reduction and ROS (reactive oxygen species) burst in cancer cells, which lead to apoptosis and G₂/M arrest in H1395 cells. However, when being exposed to oxamate, A549 cells underwent autophagy as a protective mechanism against apoptosis. Furthermore, we found evidence that LDH-A inhibition induced G₀/G₁ arrest dependent on the activation of GSK-3β in A549 cells. Taken together, our results provide useful clues for targeting LDH-A in NSCLC treatment and shed light on the discovery of molecular predictors for the sensitivity of LDH-A inhibitors.

Obatoclax induces G1/G0-phase arrest via p38/p21(waf1/Cip1) signaling pathway in human esophageal cancer cells

Pan-Bcl-2 family inhibitor obatoclax has been demonstrated to be effective against various cancers, of which the mechanism of action is not fully understood. In this study, we demonstrate that obatoclax suppressed esophageal cancer cell viability with concomitant G1/G0-phase cell cycle arrest. At the tested concentrations (1/2 IC50 and IC50), obatoclax neither induced PARP cleavage nor increased the Annexin V-positive population, suggesting G1/G0-phase arrest rather than apoptosis accounts for most of the reduction of cell viability produced by obatoclax. Double knockdown of Bak and Bax by small interference RNA failed to block obatoclax-induced G1/G0-phase arrest, implying its role in cell cycle progression is Bak/Bax-independent. The cell cycle arresting effect of obatoclax was associated with up-regulation of p21(waf1/Cip1). Knockdown of p21(waf1/Cip1) significantly attenuated obatoclax-induced G1/G0-phase arrest. Although obatoclax stimulated phosphorylation of Erk, p38, and JNK, pharmacological inhibition of p38 but not Erk or JNK blocked obatoclax-induced G1/G0-phase arrest. Moreover, knockdown of p38 abolished the cell cycle arresting effect of obatoclax. In consistent with this finding, inhibition of p38 blocked obatoclax-induced p21(waf1/Cip1) expression while inhibition of Erk or JNK failed to exert similar effect. To conclude, these findings suggest that obatoclax induced cell cycle arrest via p38/p21(waf1/Cip1) signaling pathway. This study may shed a new light on the anti-cancer activity of obatoclax in relation to cell cycle arrest.

Gambogic acid inhibits growth, induces apoptosis, and overcomes drug resistance in human colorectal cancer cells

The emergence of chemoresistance is a major limitation of colorectal cancer (CRC) therapies and novel biologically based therapies are urgently needed. Natural products represent a novel potential anticancer therapy. Gambogic acid (GA), a small molecule derived from Garcinia hanburyi Hook. f., has been demonstrated to be highly cytotoxic to several types of cancer cells and have low toxicity to the hematopoietic system. However, the potential role of GA in colorectal cancer and its ability to overcome the chemotherapeutic resistance in CRC cells have not been well studied. In the present study, we showed that GA directly inhibited proliferation and induced apoptosis in both 5-fluorouracil (5-FU) sensitive and 5-FU resistant colorectal cancer cells; induced apoptosis via activating JNK signaling pathway. The data, therefore, suggested an alternative strategy to overcome 5-FU resistance in CRC and that GA could be a promising medicinal compound for colorectal cancer therapy.

G2/M Cell Cycle Arrest and Tumor Selective Apoptosis of Acute Leukemia Cells by a Promising Benzophenone Thiosemicarbazone Compound

Anti-mitotic therapies have been considered a hallmark in strategies against abnormally proliferating cells. Focusing on the extensively studied family of thiosemicarbazone (TSC) compounds, we have previously identified 4,4'-dimethoxybenzophenone thiosemicarbazone (T44Bf) as a promising pharmacological compound in a panel of human leukemia cell lines (HL60, U937, KG1a and Jurkat). Present findings indicate that T44Bf-mediated antiproliferative effects are associated with a reversible chronic mitotic arrest caused by defects in chromosome alignment, followed by induced programmed cell death. Furthermore, T44Bf selectively induces apoptosis in leukemia cell lines when compared to normal peripheral blood mononuclear cells. The underlying mechanism of action involves the activation of the mitochondria signaling pathway, with loss of mitochondrial membrane potential and sustained phosphorylation of anti-apoptotic protein Bcl-xL as well as increased Bcl-2 (enhanced phosphorylated fraction) and pro-apoptotic protein Bad levels. In addition, ERK signaling pathway activation was found to be a requisite for T44Bf apoptotic activity. Our findings further describe a novel activity for a benzophenone thiosemicarbazone and propose T44Bf as a promising anti-mitotic prototype to develop chemotherapeutic agents to treat acute leukemia malignancies.

Anticancer properties of extracts from Opuntia humifusa against human cervical carcinoma cells

In this study, we found that the total polyphenol and ascorbic acid levels in the fruit of Opuntia humifusa are higher than those in other parts of the plant. We further hypothesized that antioxidants in O. humifusa might affect the growth or survival of cancer cells. Hexane extracts of seeds and ethyl acetate extracts of fruits and stems significantly suppressed the proliferation of HeLa cervical carcinoma cells, but did not affect the proliferation of normal human BJ fibroblasts. Additionally, the extracts of O. humifusa induced G1 phase arrest in HeLa cells. The O. humifusa extracts reduced the levels of G1 phase-associated cyclin D1, cyclin-dependent kinase 4 (Cdk4), and phosphorylated retinoblastoma proteins. Moreover, p21(WAF1/Cip1) and p53 expression significantly increased after treatment. We examined the effects of ethyl acetate extracts of O. humifusa fruit (OHF) on HeLa cells xenograft tumor growth. OHF treatment significantly reduced tumor volume and this decrease was correlated with decreased Cdk4 and cyclin D1 expression. Furthermore, flavonoids, trans Taxifolin, and dihydrokaempferol, were isolated from OHF. Thus, this extract may be a promising candidate for treating human cervical carcinoma.

Apoptotic effect of cordycepin combined with cisplatin and/or paclitaxel on MA-10 mouse Leydig tumor cells

Background

Chemotherapy is not limited to a single treatment, and the evidence demonstrates that different drug combinations can have positive results in patients. In this study, we sought to determine whether cordycepin combined with cisplatin and/or paclitaxel would have an additive effective on inducing apoptosis in mouse Leydig tumor cells, and the mechanisms were also briefly examined.

Methods

The additive effects of cordycepin combined with cisplatin and/or paclitaxel on apoptosis in MA-10 cells were investigated by monitoring changes in morphological characteristics and examining cell viability, flow cytometry assays, and Western blot analyses.

Results

Combination of cordycepin plus cisplatin and/or paclitaxel for 12 and 24 hours induced apoptotic features in MA-10 cells. The MTT assay showed that the combination treatment reduced the viability of MA-10 cells in a dose-dependent manner, with additive effects. Cell cycle analysis showed that combination treatment significantly increased subG1 phase cell numbers in MA-10 cells, indicating apoptosis. Moreover, cordycepin plus cisplatin and/or paclitaxel significantly induced cleavage of caspase-8, caspase-9, caspase-3, and poly ADP-ribose polymerase, and phosphorylation of c-Jun NH2-terminal kinase, extracellular signal-regulated kinase, p38, and p53 proteins in MA-10 cells.

Conclusion

Cordycepin plus cisplatin and/or paclitaxel can have an additive effect on apoptosis in MA-10 cells, with activation of caspase, mitogen-activated protein kinase, and p53 signal pathways.

Hesperetin Induces Apoptosis in Breast Carcinoma by Triggering Accumulation of ROS and Activation of ASK1/JNK Pathway

Hesperetin, a flavanone glycoside predominantly found in citrus fruits, exhibits a wide array of biological properties. In the present study hesperetin exhibited a significant cytotoxic effect in human breast carcinoma MCF-7 cells in a concentration- and time-dependent manner without affecting normal (HMEC) as well as immortalized normal mammary epithelial cells (MCF-10A). The cytotoxic effect of hesperetin was due to the induction of apoptosis as evident from the phosphatidyl-serine externalization, DNA fragmentation, caspase-7 activation, and PARP cleavage. Apoptosis was associated with caspase-9 activation, mitochondrial membrane potential loss, release of cytochrome c, and increase in Bax:Bcl-2 ratio. Pre-treatment with caspase-9 specific inhibitor (Z-LEHD-fmk) markedly attenuated apoptosis suggesting an involvement of intrinsic mitochondrial apoptotic cascade. Further, DCFDA flow-cytometric analysis revealed triggering of ROS in a time-dependent manner. Pre-treatment with ROS scavenger N-acetylcysteine (NAC) and glutathione markedly abrogated hesperetin-mediated apoptosis whereas carbonyl cyanide m-chlorophenylhydrazone (CCCP) pretreatment along with DHR123-based flow-cytometry indicated the generation of cytosolic ROS. Profiling of MAPKs revealed activation of JNK upon hesperetin treatment which was abrogated upon NAC pre-treatment. Additionally, inhibition of JNK by SP600125 significantly reversed hesperetin-mediated apoptosis. The activation of JNK was associated with the activation of ASK1. Silencing of ASK1 resulted in significant attenuation of JNK activation as well as reversed the hesperetin-mediated apoptosis suggesting that hesperetin-mediated apoptosis of MCF-7 cells involves accumulation of ROS and activation of ASK1/JNK pathway. In addition, hesperetin also induced apoptosis in triple negative breast cancer MDA-MB-231 cells via intrinsic pathway via activation of caspase -9 and -3 and increase in Bax:Bcl-2 ratio.

Modulatory role of resveratrol on cytotoxic activity of cisplatin, sensitization and modification of cisplatin resistance in colorectal cancer cells

Colorectal cancer (CRC) is a leading cause of cancer-associated mortality worldwide. Cisplatin (CIS) is one of the most active cytotoxic agents in current use and it has proven efficacy against various human malignancies. However, its clinical usefulness has been restricted by detrimental side effects, including nephrotoxicity and myelosuppression. The aim of the present study was to attempt to decrease the required dose of CIS, in order to minimize its side effects, and increase its capability to arrest, delay or reverse carcinogenesis. In addition, the present study aimed to ameliorate CIS-resistance in CRC cells, using the natural compound resveratrol (RSVL). RSVL (3,4', 5-trihydroxy-trans-stilbene) is a naturally occurring polyphenol present in the roots of white hellebore (Veratrum grandiflorum O. Loes) and extracted from >70 other plant species. RSVL can exert antioxidant and anti-inflammatory activities, and it has been shown to be active in the regulation of numerous cellular events associated with carcinogenesis. The present study evaluated the effects of RSVL on sensitization of both parent and CIS-resistant HCT-116 CRC cells to the action of cisplatin. The CIS was administered at a dose of 5 and 20 µg/ml, and CIS cytotoxicity, apoptosis, cell cycle and cisplatin cellular uptake were examined in the presence and absence of RSVL (15 µg/ml). RSVL treatment showed anti-proliferative effects and enhanced the cytotoxic effects of cis against the growth of both parent and CIS-resistant HCT-116 CRC cells, with a half maximal inhibitory concentration of 4.20 µg/ml and 4.72 µg/ml respectively. RSVL also induced a significant increase in the early apoptosis fraction and enhanced the subsequent apoptotic effects of CIS. The cellular uptake of CIS was significantly increased in the presence of RSVL, as compared with CIS treatment alone, and RSVL treatment sensitized the CIS-resistant HCT-116 cells. In conclusion, RSVL treatment increased the cytotoxic activity of CIS against the growth of both parent and CIS-resistant HCT-116 CRC cells.

A novel quantitative model of cell cycle progression based on cyclin-dependent kinases activity and population balances

Cell cycle regulates proliferative cell capacity under normal or pathologic conditions, and in general it governs all in vivo/in vitro cell growth and proliferation processes. Mathematical simulation by means of reliable and predictive models represents an important tool to interpret experiment results, to facilitate the definition of the optimal operating conditions for in vitro cultivation, or to predict the effect of a specific drug in normal/pathologic mammalian cells. Along these lines, a novel model of cell cycle progression is proposed in this work. Specifically, it is based on a population balance (PB) approach that allows one to quantitatively describe cell cycle progression through the different phases experienced by each cell of the entire population during its own life. The transition between two consecutive cell cycle phases is simulated by taking advantage of the biochemical kinetic model developed by Gérard and Goldbeter (2009) which involves cyclin-dependent kinases (CDKs) whose regulation is achieved through a variety of mechanisms that include association with cyclins and protein inhibitors, phosphorylation-dephosphorylation, and cyclin synthesis or degradation. This biochemical model properly describes the entire cell cycle of mammalian cells by maintaining a sufficient level of detail useful to identify check point for transition and to estimate phase duration required by PB. Specific examples are discussed to illustrate the ability of the proposed model to simulate the effect of drugs for in vitro trials of interest in oncology, regenerative medicine and tissue engineering.

Abieslactone induces cell cycle arrest and apoptosis in human hepatocellular carcinomas through the mitochondrial pathway and the generation of reactive oxygen species

Abieslactone is a triterpenoid lactone isolated from Abies plants. Previous studies have demonstrated that its derivative abiesenonic acid methyl ester possesses anti-tumor-promoting activity in vitro and in vivo. In the present study, cell viability assay demonstrated that abieslactone had selective cytotoxicity against human hepatoma cell lines. Immunostaining experiments revealed that abieslactone induced HepG2 and SMMC7721 cell apoptosis. Flow cytometry and western blot analysis showed that the apoptosis was associated with cell cycle arrest during the G₁ phase, up-regulation of p53 and p21, and down-regulation of CDK2 and cyclin D1. Furthermore, our results revealed that induction of apoptosis through a mitochondrial pathway led to upregulation of Bax, down-regulation of Bcl-2, mitochondrial release of cytochrome c, reduction of mitochondrial membrane potential (MMP), and activation of caspase cascades (Casp-9 and -3). Activation of caspase cascades also resulted in the cleavage of PARP fragment. Involvement of the caspase apoptosis pathway was confirmed using caspase inhibitor Z-VAD-FMK pretreatment. Recent studies have shown that ROS is upstream of Akt signal in mitochondria-mediated hepatoma cell apoptosis. Our results showed that the accumulation of ROS was detected in HepG2 cells when treated with abieslactone, and ROS scavenger partly blocked the effects of abieslactone-induced HepG2 cell death. In addition, inactivation of total and phosphorylated Akt activities was found to be involved in abieslactone-induced HepG2 cell apoptosis. Therefore, our findings suggested that abieslactone induced G₁ cell cycle arrest and caspase-dependent apoptosis via the mitochondrial pathway and the ROS/Akt pathway in HepG2 cells.

Anti-proliferative of physcion 8-O-β-glucopyranoside isolated from Rumex japonicus Houtt. on A549 cell lines via inducing apoptosis and cell cycle arrest

Background

Lung cancers are leading causes of cancer death, and Rumex japonicus has been traditionally used in folk medicine as anti-microorganic, anti-inflammatory and anti-tumor agents. This study was designed to investigate the anti-proliferative activity of physcion 8-O-β-glucopyranoside (PG) isolated from Rumex japonicus Houtt. on A549 cell lines.

Methods

In our present study, PG was isolated and identified from the ethanol extracts of R. japonicus. MTT method was used to evaluate the anti-proliferative activity of PG on A549 cell lines, and cell cycle distribution assay, apoptosis assay, and western blot analysis in vitro were used to explore the possible mechanisms.

Results

From the results of our present study, cell viability was obviously inhibited by PG, in a dose- and time-dependent manner. Our results also suggested that the anti-proliferative effect of PG was related to cell cycle arrest at the G2/M phase through repression of cdc2 and Cyclin B1 protein expression. In addition, the results of apoptosis assay and western blot analysis indicated that the anti-proliferative activity could be related to apoptosis via up-regulating the expressions of Bax, caspase-3 and caspase-7, and down-regulating the expressions of Bcl-2.

Conclusions

In conclusion, the PG has significant anti-proliferative activity on A549 cell lines, and the possible mechanism was related to cell cycle arrest at the G2/M phase, and apoptosis via the regulations of Bax, Bcl-2, and caspase-3 and caspase-7.

Sparstolonin B, a novel plant derived compound, arrests cell cycle and induces apoptosis in N-myc amplified and N-myc nonamplified neuroblastoma cells

Neuroblastoma is one of the most common solid tumors and accounts for ∼15% of all the cancer related deaths in the children. Despite the standard therapy for advanced disease including chemotherapy, surgery, and radiation, the mortality rate remains high for these patients. Hence, novel therapeutic agents are desperately needed. Here we examined the anticancer activity of a novel plant-derived compound, sparstolonin B (SsnB; 8,5′-dihydroxy-4-phenyl-5,2′-oxidoisocoumarin) using neuroblastoma cell lines of different genetics. SsnB was recently isolated from an aquatic Chinese herb, Sparganium stoloniferum, and tubers of this herb have been used in traditional Chinese medicine for the treatment of several inflammatory diseases and cancers. Our cell viability and morphological analysis indicated that SsnB at 10 µM concentration significantly inhibited the growth of both N-myc amplified (SK-N-BE(2), NGP, and IMR-32 cells) and N-myc nonamplified (SH-SY5Y and SKNF-1 cells) neuroblastoma cells. The flow cytometric analyses suggested that SsnB arrests the cell cycle progression at G2-M phase in all neuroblastoma cell lines tested. Exposure of SsnB inhibited the compact spheroid formation and reduced the tumorigenicity of SH-SY5Y cells and SK-N-BE(2) cells in in vitro 3-D cell culture assays (anchorage-independent colony formation assay and hanging drop assay). SsnB lowers the cellular level of glutathione (GSH), increases generation of reactive oxygen species and activates the cleavage of caspase-3 whereas co-incubation of a GSH precursor, N-acetylcysteine, along with SsnB attenuates the inhibitory effects of SsnB and increases the neuroblastoma cell viability. Our results for the first time demonstrate that SsnB possesses anticancer activity indicating that SsnB-induced reactive oxygen species generation promotes apoptotic cell death in neuroblastoma cells of different genetic background. Thus these data suggest that SsnB can be a promising drug candidate in neuroblastoma therapy.

Phase I dose-escalation study of AZD7762, a checkpoint kinase inhibitor, in combination with gemcitabine in US patients with advanced solid tumors

PURPOSE

AZD7762 is a Chk1 kinase inhibitor which increases sensitivity to DNA-damaging agents, including gemcitabine. We evaluated the safety of AZD7762 monotherapy and with gemcitabine in advanced solid tumor patients.

EXPERIMENTAL DESIGN

In this Phase I study, patients received intravenous AZD7762 on days 1 and 8 of a 14-day run-in cycle (cycle 0; AZD7762 monotherapy), followed by AZD7762 plus gemcitabine 750-1,000 mg/m(2) on days 1 and 8, every 21 days, in ascending AZD7762 doses (cycle 1; combination therapy).

RESULTS

Forty-two patients received AZD7762 6 mg (n = 9), 9 mg (n = 3), 14 mg (n = 6), 21 mg (n = 3), 30 mg (n = 7), 32 mg (n = 6), and 40 mg (n = 8), in combination with gemcitabine. Common adverse events (AEs) were fatigue [41 % (17/42) patients], neutropenia/leukopenia [36 % (15/42) patients], anemia/Hb decrease [29 % (12/42) patients] and nausea, pyrexia and alanine aminotransferase/aspartate aminotransferase increase [26 % (11/42) patients each]. Grade ≥3 AEs occurred in 19 and 52 % of patients in cycles 0 and 1, respectively. Cardiac dose-limiting toxicities occurred in two patients (both AZD7762 monotherapy): grade 3 troponin I increase (32 mg) and grade 3 myocardial ischemia with chest pain, electrocardiogram changes, decreased left ventricular ejection fraction, and increased troponin I (40 mg). AZD7762 exposure increased linearly. Gemcitabine did not affect AZD7762 pharmacokinetics. Two non-small-cell lung cancer patients achieved partial tumor responses (AZD7762 6 mg/gemcitabine 750 mg/m(2) and AZD7762 9 mg cohort).

CONCLUSIONS

The maximum-tolerated dose of AZD7762 in combination with gemcitabine 1,000 mg/m(2) was 30 mg. Although development of AZD7762 is not going forward owing to unpredictable cardiac toxicity, Chk1 remains an important therapeutic target.

Modulation of cyclins, p53 and mitogen-activated protein kinases signaling in breast cancer cell lines by 4-(3,4,5-trimethoxyphenoxy)benzoic acid

Despite the advances in cancer therapy and early detection, breast cancer remains a leading cause of cancer-related deaths among females worldwide. The aim of the current study was to investigate the antitumor activity of a novel compound, 4-(3,4,5-trimethoxyphenoxy)benzoic acid (TMPBA) and its mechanism of action, in breast cancer. Results indicated the relatively high sensitivity of human breast cancer cell-7 and MDA-468 cells towards TMPBA with IC₅₀ values of 5.9 and 7.9 μM, respectively compared to hepatocarcinoma cell line Huh-7, hepatocarcinoma cell line HepG2, and cervical cancer cell line Hela cells. Mechanistically, TMPBA induced apoptotic cell death in MCF-7 cells as indicated by 4′,6-diamidino-2-phenylindole (DAPI) nuclear staining, cell cycle analysis and the activation of caspase-3. Western blot analysis revealed the ability of TMPBA to target pathways mediated by mitogen-activated protein (MAP) kinases, 5′ adenosine monophosphate-activated protein kinase (AMPK), and p53, of which the concerted action underlined its antitumor efficacy. In addition, TMPBA induced alteration of cyclin proteins’ expression and consequently modulated the cell cycle. Taken together, the current study underscores evidence that TMPBA induces apoptosis in breast cancer cells via the modulation of cyclins and p53 expression as well as the modulation of AMPK and mitogen-activated protein kinases (MAPK) signaling. These findings support TMPBA’s clinical promise as a potential candidate for breast cancer therapy.

Ligand modulation of a dinuclear platinum compound leads to mechanistic differences in cell cycle progression and arrest

Despite similar structures and DNA binding profiles, two recently synthesized dinuclear platinum compounds are shown to elicit highly divergent effects on cell cycle progression. In colorectal HCT116 cells, BBR3610 shows a classical G2/M arrest with initial accumulation in S phase, but the derivative compound BBR3610-DACH, formed by introduction of the 1,2-diaminocyclohexane (DACH) as carrier ligand, results in severe G1/S as well as G2/M phase arrest, with nearly complete S phase depletion. The origin of this unique effect was studied. Cellular interstrand crosslinking as assayed by comet analysis was similar for both compounds, confirming previous in vitro results obtained on plasmid DNA. Immunoblotting revealed a stabilization of p53 and concomitant transient increases in p21 and p27 proteins after treatment with BBR3610-DACH. Cell viability assays and cytometric analysis of p53 and p21 null cells indicated that BBR3610-DACH-induced cell cycle arrest was p21-dependent and partially p53-dependent. However, an increase in the levels of cyclin E was observed with steady state levels of CDK2 and Cdc25A, suggesting that the G1 block occurs downstream of CDK/cyclin complex formation. The G2/M block was corroborated with decreased levels of cyclin A and cyclin B1. Surprisingly, BBR3610-DACH-induced G1 block was independent of ATM and ATR. Finally, both compounds induced apoptosis, with BBR3610-DACH showing a robust PARP-1 cleavage that was not associated with caspase-3/7 cleavage. In summary, BBR3610-DACH is a DNA binding platinum agent with unique inhibitory effects on cell cycle progression that could be further developed as a chemotherapeutic agent complementary to cisplatin and oxaliplatin.

Isoalantolactone inhibits UM-SCC-10A cell growth via cell cycle arrest and apoptosis induction

Isoalantolactone is a sesquiterpene lactone compound isolated from the roots of Inula helenium L. Previous studies have demonstrated that isoalantolactone possesses antifungal, anti-bacterial, anti-helminthic and anti-proliferative properties in a variety of cells, but there are no studies concerning its effects on head and neck squamous cell carcinoma (HNSCC). In the present study, an MTT assay demonstrated that isoalantolactone has anti-proliferative activity against the HNSCC cell line (UM-SCC-10A). Immunostaining identified that this compound induced UM-SCC-10A cell apoptosis but not necrosis. To explain the molecular mechanisms underlying its effects, flow cytometry and western blot analysis showed that the apoptosis was associated with cell cycle arrest during the G1 phase, up-regulation of p53 and p21, and down-regulation of cyclin D. Furthermore, our results revealed that induction of apoptosis through a mitochondrial pathway led to up-regulation of pro-apoptotic protein expression (Bax), down-regulation of anti-apoptotic protein expression (Bcl-2), mitochondrial release of cytochrome c (Cyto c), reduction of mitochondrial membrane potential (MMP) and activation of caspase-3 (Casp-3). Involvement of the caspase apoptosis pathway was confirmed using caspase inhibitor Z-VAD-FMK pretreatment. Together, our findings suggest that isoalantolactone induced caspase-dependent apoptosis via a mitochondrial pathway and was associated with cell cycle arrest in the G1 phase in UM-SCC-10A cells. Therefore, isoalantolactone may become a potential drug for treating HNSCC.

Inhibition of LDH-A by oxamate induces G2/M arrest, apoptosis and increases radiosensitivity in nasopharyngeal carcinoma cells

An elevated rate of glucose consumption and the dependency on aerobic glycolysis for ATP generation have long been observed in cancer cells, a phenomenon known as the Warburg effect. the altered energy metabolism in cancer cells provides an attractive opportunity for developing novel cancer therapeutic strategies. Lactate dehydrogenase (LDH), which catalyzes the transformation of pyruvate to lactate, plays a vital role in the process of glycolysis. It has been reported that the level of LDH-A expression is increased both in head and neck cancer cells and in the blood serum of nasopharyngeal carcinoma (NPC) patients, and is associated with poor prognosis. However, the effect of LDH-A inhibition on NPC cells remains unknown. Here, in the present study, we found that oxamate, a classical inhibitor of LDH-A, suppressed cell proliferation in a dose- and time-dependent manner both in CNE-1 and CNE-2 cells, two NPC cancer cell lines. LDH inhibition by oxamate induced G2/M cell cycle arrest via downregulation of the CDK1/cyclin B1 pathway and promoted apoptosis through enhancement of mitochondrial ROS generation. N-acetylcysteine, a specific scavenger of ROS, significantly blocked the growth inhibition effect induced by oxamate. We also identified that oxamate increased sensitivity to ionizing radiation in the two NPC cancer cell lines. Furthermore, we verified similar results in tumor xenograft models. collectively, these results suggest that LDH-A may serve as a promising therapeutic target for NPC treatment.

3-Bromo-1-hydroxy-9,10-anthraquinone (BHAQ) inhibits growth and migration of the human breast cancer cell lines MCF-7 and MDA-MB231

Breast cancer is becoming more prominent in women today. As of now, there are no effective treatments in treating metastatic breast cancer. We have tested the cytotoxic and anti-migration effects of BHAQ, a synthesized anthraquinone, on two breast cancer cell lines, MCF-7 and MDA-MB231. Anthraquinones are an interesting class of molecules that display a wide spectrum of biological applications, including anticancer properties. Cellular inhibition was tested through a MTT assay, double acridine orange/propidium iodide staining and FACS cell cycle analysis. Inhibition of migration was tested by the wound healing method, and migration through a Boyden chamber. BHAQ was cytotoxic towards both cell lines in a dose dependent and possibly cell-dependent manner. Additionally, BHAQ also inhibited the migration of the highly metastatic MDA-MB231 cell line.

Selective inhibition of p300 HAT blocks cell cycle progression, induces cellular senescence, and inhibits the DNA damage response in melanoma cells

Epigenetic events, including covalent post-translational modifications of histones, have been demonstrated to have critical roles in tumor development and progression. The transcriptional coactivator p300/CBP possesses both histone acetyltransferase (HAT) activity and scaffolding properties that directly influence the transcriptional activation of targeted genes. We have used a potent and specific inhibitor of p300/CBP HAT activity, C646, in order to evaluate the functional contributions of p300/CBP HAT to tumor development and progression. Here we report that C646 inhibits the growth of human melanoma and other tumor cells and promotes cellular senescence. Global assessment of the p300 HAT transcriptome in human melanoma identified functional roles in promoting cell cycle progression, chromatin assembly, and activation of DNA repair pathways through direct transcriptional regulatory mechanisms. In addition, C646 is shown to promote sensitivity to DNA damaging agents, leading to the enhanced apoptosis of melanoma cells after combination treatment with cisplatin. Together, our data suggest that p300 HAT activity mediates critical growth regulatory pathways in tumor cells and may serve as a potential therapeutic target for melanoma and other malignancies by promoting cellular responses to DNA damaging agents that are currently ineffective against specific cancers.

Antileukemic potential of PEGylated gold nanoparticle conjugated with protein toxin (NKCT1) isolated from Indian cobra (Naja kaouthia) venom

Limited efficacy of current first-line treatment for leukemia calls attention for further development of efficient strategies. Recently, much attention has been given to nanoparticle-based drug delivery systems loaded with dual drugs to improve current disease therapies by overcoming toxicity. In the present study, we document to explore an approach to conjugate gold nanoparticles (GNPs) with protein toxin (NKCT1), a protein toxin from the Indian cobra (Naja kaouthia) venom, and to establish its antileukemic activity. GNP was prepared by NaBH₄ reduction method. UV–vis spectroscopy of GNP showed the absorbance at 530 nm for plasma resonance. Dynamic light scattering (DLS) size of GNPs was 2–8 nm and the GNP-NKCT1 was 68–122 nm. CD spectra of GNP-NKCT1 showed change in percentage of β-turn as compared with NKCT1. GNP-NKCT1 significantly inhibited leukemic cell growth in dose- and time-dependent manner by two- to threefold more than NKCT1. For human leukemic lymphoma cell line and human myelogenous leukemic cell line, the IC50 dose was found to be 1.2 and 0.75 μg/ml, respectively, observed by trypan blue exclusion method and tetrazolium bromide reduction assay. Flow cytometric analysis showed appreciable number of both cell lines in early and late apoptotic stages and arrested cell cycle in the G1 phase by GNP-NKCT1. Resilient power of leukemic cell line after wound healing and migration or invasive power of the cell line was significantly low in GNP-NKCT1-treated plate than the control plate. These analyses reveal that GNP-NKCT1 possesses significant and selective anticancer activity, likely by inducing programmed cell death through mitochondrial and/or lysosomal pathway.

α-Santalol, a skin cancer chemopreventive agent with potential to target various pathways involved in photocarcinogenesis

This study is designed to investigate the chemopreventive effect and molecular mechanisms of α-santalol on UVB-induced skin tumor development in SKH-1 hairless mouse, a widely used model for human photocarcinogenesis. A dose of UVB radiation (30 mJ cm(-2) day(-1)) that is in the range of human sunlight exposure was used for the initiation and promotion of tumor. Topical treatment of mice with α-santalol (10%, wt/vol in acetone) caused reduction in tumor incidence, multiplicity and volume. In our study, the anticarcinogenic action of α-santalol against UVB-induced photocarcinogenesis was found to be associated with inhibition of inflammation and epidermal cell proliferation, cell cycle arrest and induction of apoptosis. α-Santalol pretreatment strongly inhibited UVB-induced epidermal hyperplasia and thickness of the epidermis, expression of proliferation and inflammation markers proliferating cell nuclear antigen (PCNA), Ki-67 and cyclooxygenase 2 (Cox-2). Significant decrease in the expression of cyclins A, B1, D1 and D2 and cyclin-dependent kinases (Cdk)s Cdk1 (Cdc2), Cdk2, Cdk4 and Cdk6 and an upregulated expression of cyclin-dependent kinase (CDK) inhibitor Cip1/p21 were found in α-santalol pretreated group. Furthermore, an elevated level of cleaved caspase 3 and cleaved poly (ADP-ribose) polymerase (PARP) were observed in α-santalol-treated group. Our data suggested that α-santalol is a safer and promising skin cancer chemopreventive agent with potential to target various pathways involved in photocarcinogenesis.

Antineoplastic effects of α-santalol on estrogen receptor-positive and estrogen receptor-negative breast cancer cells through cell cycle arrest at G2/M phase and induction of apoptosis

Anticancer efficacy and the mechanism of action of α-santalol, a terpenoid isolated from sandalwood oil, were investigated in human breast cancer cells by using p53 wild-type MCF-7 cells as a model for estrogen receptor (ER)-positive and p53 mutated MDA-MB-231 cells as a model for ER-negative breast cancer. α-Santalol inhibited cell viability and proliferation in a concentration and time-dependent manner in both cells regardless of their ER and/or p53 status. However, α-santalol produced relatively less toxic effect on normal breast epithelial cell line, MCF-10A. It induced G2/M cell cycle arrest and apoptosis in both MCF-7 and MDA-MB-231 cells. Cell cycle arrest induced by α-santalol was associated with changes in the protein levels of BRCA1, Chk1, G2/M regulatory cyclins, Cyclin dependent kinases (CDKs), Cell division cycle 25B (Cdc25B), Cdc25C and Ser-216 phosphorylation of Cdc25C. An up-regulated expression of CDK inhibitor p21 along with suppressed expression of mutated p53 was observed in MDA-MB-231 cells treated with α-santalol. On the contrary, α-santalol did not increase the expression of wild-type p53 and p21 in MCF-7 cells. In addition, α-santalol induced extrinsic and intrinsic pathways of apoptosis in both cells with activation of caspase-8 and caspase-9. It led to the activation of the executioner caspase-6 and caspase-7 in α-santalol-treated MCF-7 cells and caspase-3 and caspase-6 in MDA-MB-231 cells along with strong cleavage of poly(ADP-ribose) polymerase (PARP) in both cells. Taken together, this study for the first time identified strong anti-neoplastic effects of α-santalol against both ER-positive and ER-negative breast cancer cells.

MAPK signaling in cisplatin-induced death: predominant role of ERK1 over ERK2 in human hepatocellular carcinoma cells

Hepatocellular carcinoma treatment by arterial infusion of cis-diamminedichloroplatinum-II (cisplatin) exhibits certain therapeutic efficacy. However, optimizations are required and the mechanisms underlying cisplatin proapoptotic effect remain unclear. The mitogen-activated protein kinase (MAPK) pathway plays a key role in cell response to cisplatin and the functional specificity of the isoform MAPK/ERK kinase 1 and 2 (MEK1/2) and ERK1/2 could influence this response. The individual contribution of each kinase on cisplatin-induced death was thus analyzed after a transient or stable specific inhibition by RNA interference in the human hepatocellular carcinoma cells Huh-7 or in knockout mice. We demonstrated here that ERK1 played a predominant role over ERK2 in cisplatin-induced death, whereas MEK1 and MEK2 acted in a redundant manner. Indeed, at clinically relevant concentrations of cisplatin, ERK1 silencing alone was sufficient to protect cells from cisplatin-induced death both in vitro, in Huh-7 cells and ERK1(-/-) hepatocytes, and in vivo, in ERK1-deficient mice. Moreover, we showed that ERK1 activity correlated with the induction level of the proapoptotic BH3-only protein Noxa, a critical mediator of cisplatin toxicity. On the contrary, ERK2 inhibition upregulated ERK1 activity, favored Noxa induction and sensitized hepatocarcinoma cells to cisplatin. Our results point to a crucial role of ERK1 in cisplatin-induced proapoptotic signal and lead us to propose that ERK2-specific targeting could improve the efficacy of cisplatin therapy by increasing ERK1 prodeath functions.

An aqueous extract of Fagonia cretica induces DNA damage, cell cycle arrest and apoptosis in breast cancer cells via FOXO3a and p53 expression

BACKGROUND

Plants have proved to be an important source of anti-cancer drugs. Here we have investigated the cytotoxic action of an aqueous extract of Fagonia cretica, used widely as a herbal tea-based treatment for breast cancer.

METHODOLOGY/PRINCIPAL FINDINGS

Using flow cytometric analysis of cells labeled with cyclin A, annexin V and propidium iodide, we describe a time and dose-dependent arrest of the cell cycle in G0/G1 phase of the cell cycle and apoptosis following extract treatment in MCF-7 (WT-p53) and MDA-MB-231 (mutant-p53) human breast cancer cell lines with a markedly reduced effect on primary human mammary epithelial cells. Analysis of p53 protein expression and of its downstream transcription targets, p21 and BAX, revealed a p53 associated growth arrest within 5 hours of extract treatment and apoptosis within 24 hours. DNA double strand breaks measured as γ-H2AX were detected early in both MCF-7 and MDA-MB-231 cells. However, loss of cell viability was only partly due to a p53-driven response; as MDA-MB-231 and p53-knockdown MCF-7 cells both underwent cell cycle arrest and death following extract treatment. p53-independent growth arrest and cytotoxicity following DNA damage has been previously ascribed to FOXO3a expression. Here, in MCF-7 and MDA-MB-231 cells, FOXO3a expression was increased significantly within 3 hours of extract treatment and FOXO3 siRNA reduced the extract-induced loss of cell viability in both cell lines.

CONCLUSIONS/SIGNIFICANCE

Our results demonstrate for the first time that an aqueous extract of Fagonia cretica can induce cell cycle arrest and apoptosis via p53-dependent and independent mechanisms, with activation of the DNA damage response. We also show that FOXO3a is required for activity in the absence of p53. Our findings indicate that Fagonia cretica aqueous extract contains potential anti-cancer agents acting either singly or in combination against breast cancer cell proliferation via DNA damage-induced FOXO3a and p53 expression.

Mechanisms of Cisplatin-Induced Apoptosis and of Cisplatin Sensitivity: Potential of BIN1 to Act as a Potent Predictor of Cisplatin Sensitivity in Gastric Cancer Treatment

Cisplatin is the most important and efficacious chemotherapeutic agent for the treatment of advanced gastric cancer. Cisplatin forms inter- and intrastrand crosslinked DNA adducts and its cytotoxicity is mediated by propagation of DNA damage recognition signals to downstream pathways involving ATR, p53, p73, and mitogen-activated protein kinases, ultimately resulting in apoptosis. Cisplatin resistance arises through a multifactorial mechanism involving reduced drug uptake, increased drug inactivation, increased DNA damage repair, and inhibition of transmission of DNA damage recognition signals to the apoptotic pathway. In addition, a new mechanism has recently been revealed, in which the oncoprotein c-Myc suppresses bridging integrator 1 (BIN1), thereby releasing poly(ADP-ribose)polymerase 1, which results in increased DNA repair activity and allows cancer cells to acquire cisplatin resistance. The present paper focuses on the molecular mechanisms of cisplatin-induced apoptosis and of cisplatin resistance, in particular on the involvement of BIN1 in the maintenance of cisplatin sensitivity.

Role of a DNA damage checkpoint pathway in ionizing radiation-induced glioblastoma cell migration and invasion

Ionizing radiation (IR) induces a DNA damage response that includes activation of cell cycle checkpoints, leading to cell cycle arrest. In addition, IR enhances cell invasiveness of glioblastoma cells, among other tumor cell types. Using RNA interference, we found that the protein kinase MRK, previously implicated in the DNA damage response to IR, also inhibits IR-induced cell migration and invasion of glioblastoma cells. We showed that MRK activation by IR requires the checkpoint protein Nbs1 and that Nbs1 is also required for IR-stimulated migration. In addition, we show that MRK acts upstream of Chk2 and that Chk2 is also required for IR-stimulated migration and invasion. Thus, we have identified Nbs1, MRK, and Chk2 as elements of a novel signaling pathway that mediates IR-stimulated cell migration and invasion. Interestingly, we found that inhibition of cell cycle progression, either with the CDK1/2 inhibitor CGP74514A or by downregulation of the CDC25A protein phosphatase, restores IR-induced migration and invasion in cells depleted of MRK or Chk2. These data indicate that cell cycle progression, at least in the context of IR, exerts a negative control on the invasive properties of glioblastoma cells and that checkpoint proteins mediate IR-induced invasive behavior by controlling cell cycle arrest.

7 Methyl indole ethyl isothiocyanate causes ROS mediated apoptosis and cell cycle arrest in endometrial cancer cells

OBJECTIVE

Chemotherapy options for advanced endometrial cancer are limited and newer therapeutic agents are urgently needed. This study describes the therapeutic potential of 7 Methyl-indole ethyl isothiocyanate (7Me-IEITC) in endometrial cancer cell lines.

METHODS

7Me-IEITC was synthesized in our laboratory. The cell viability of 7Me-IEITC treated ECC-1 and KLE endometrial cancer cell was determined by MTS assay. Morphology and apoptosis were further confirmed by DAPI-staining and TUNEL assay. The measurement of reactive oxygen species (ROS), mitochondrial transmembrane depolarization potential (ΔΨm) and cell cycle phase was determined by FACS analysis. Expression of proteins involved in apoptosis, survival and cell-cycle progression was analyzed by Western blotting.

RESULTS

7Me-IEITC reduced the viability of the ECC-1 and KLE cancer cell-lines (IC(50)~2.5-10 μM) in a dose dependent fashion. 7Me-IEITC treatment caused mitochondrial transmembrane potential reduction, elevated the production of ROS, leading to activation of apoptosis in endometrial cancer KLE and ECC-1 cells. 7Me-IEITC treatment activated Bad, suppressed Bcl2 phosphorylation followed by PARP-1 deactivation and caspase 3 and 7 activation. 7Me-IEITC treatment arrested the progression of KLE cells in S-phase and caused CDC25 and cyclin-D1 downregulation. Pre-treatment with ascorbic acid abrogated 7Me-IEITC induced apoptosis in ECC-1 and KLE cells, suggesting that 7Me-IEITC mediated cytotoxicity is primarily through ROS production.

CONCLUSION

7Me-IEITC demonstrated promising cytotoxic effects in endometrial cancer cell line model.

DNA damage response and repair: insights into strategies for radiation sensitization of gliomas

The incorporation of radiotherapy into multimodality treatment plans has led to significant improvements in glioma patient survival. However, local recurrence from glioma resistance to ionizing radiation remains a therapeutic challenge. The tumoricidal effect of radiation therapy is largely attributed to the induction of dsDNA breaks (DSBs). In the past decade, there have been tremendous strides in understanding the molecular mechanisms underlying DSB repair. The identification of gene products required for DSB repair has provided novel therapeutic targets. Recent studies revealed that many US FDA-approved cancer agents inhibit DSB repair by interacting with repair proteins. This article will aim to provide discussion of DSB repair mechanisms to provide molecular targets for radiation sensitization of gliomas and a discussion of FDA-approved cancer therapies that modulate DSB repair to highlight opportunities for combination therapy with radiotherapy for glioma therapy.

Targeting the S and G2 checkpoint to treat cancer

Cell survival following DNA damage depends on activating checkpoints to arrest proliferation. Most cancer cells have dysregulated G1 checkpoints making them dependent on their S and G2 checkpoints, which are activated by ATR/Chk1 signalling. Thus, inhibiting ATR or Chk1 should selectively sensitise cancer cells to DNA damage. Genetic inactivation of ATR and Chk1 abrogates cell cycle arrest and enhances cytotoxicity following exposure to DNA-damaging agents. Similar effects were seen with small-molecule Chk1 inhibitors in preclinical studies, and clinical trial data are starting to emerge. Recently, potent ATR inhibitors have been identified that also sensitise cancer cells in vitro. ATR and Chk1 inhibitors might also cause 'synthetic lethality' in tumour cells defective in defined DNA repair pathways.

Design, synthesis and biological evaluation of new naphtalene diimides bearing isothiocyanate functionality

The synthesis and the biological activities of new derivatives 1-3, characterized by the isothiocyanate (ITC) functionalities coming from sulforaphane (SFN), a well-known anticancer natural product, were reported. The most interesting compound of the series was 2. It was chemically characterized by two ITC functionalities mounted on the 1,4,5,8-naphthalentetracarboxylic diimide (NDI) scaffold through two polymethylene chains, each constituted by three carbon units. It demonstrated an IC(50) value in the submicromolar range, more potent than SFN, displaying also the ability to trigger apoptotic induction in the same range by eliciting both extrinsic and intrinsic apoptotic pathways. Finally, it was observed that 2 inhibited the cell growth by blocking the cell cycle in G1 phase.

Cutting edge: Chk1 directs senescence and mitotic catastrophe in recovery from G₂ checkpoint arrest

Besides the well-understood DNA damage response via establishment of G₂ checkpoint arrest, novel studies focus on the recovery from arrest by checkpoint override to monitor cell cycle re-entry. The aim of this study was to investigate the role of Chk1 in the recovery from G₂ checkpoint arrest in HCT116 (human colorectal cancer) wt, p53^–/– and p21^–/– cell lines following H₂O₂ treatment. Firstly, DNA damage caused G₂ checkpoint activation via Chk1. Secondly, overriding G₂ checkpoint led to (i) mitotic slippage, cell cycle re-entry in G₁ and subsequent G₁ arrest associated with senescence or (ii) premature mitotic entry in the absence of p53/p21^WAF1 causing mitotic catastrophe. We revealed subtle differences in the initial Chk1-involved G₂ arrest with respect to p53/p21^WAF1: absence of either protein led to late G₂ arrest instead of the classic G₂ arrest during checkpoint initiation, and this impacted the release back into the cell cycle. Thus, G₂ arrest correlated with downstream senescence, but late G₂ arrest led to mitotic catastrophe, although both cell cycle re-entries were linked to upstream Chk1 signalling. Chk1 knockdown deciphered that Chk1 defines long-term DNA damage responses causing cell cycle re-entry. We propose that recovery from oxidative DNA damage-induced G₂ arrest requires Chk1. It works as cutting edge and navigates cells to senescence or mitotic catastrophe. The decision, however, seems to depend on p53/p21^WAF1. The general relevance of Chk1 as an important determinant of recovery from G₂ checkpoint arrest was verified in HT29 colorectal cancer cells.

Description of the cytotoxic effect of a novel drug Abietyl-Isothiocyanate on endometrial cancer cell lines

The objective of the present study was to determine the in-vitro effect of Abietyl-Isothiocyanate (ABITC), a representative of a new class of anti-cancer drugs, on endometrial cancer (EC) cell lines. ABITC at concentrations ≥1 μM displayed dose-dependent and selective cytotoxicity to EC cell lines (ECC-1, AN3CA, RL95-2) in comparison to other cancer cell lines. After treatment with ABITC, ECC-1 unlike control cells displayed hallmark features of apoptosis including chromatin condensation and nuclear fragmentation. At concentrations below the IC50, ABITC exerted anti-proliferative effects by blocking cell-cycle progression through G0/G1 and S-phase. In addition, cells attempted to counteract drug treatment by pro-survival signaling such as deactivation of JNK/SAPK and p38 MAPK and activation of AKT and ErK1/2. ABITC also altered EGF-receptor phosphorylation. At a concentration of 5 μM ABITC generated an excess amount of reactive oxygen species (ROS) and displayed pro-apoptotic signaling such as activation of caspase-8, JNK-SAPK and deactivation of PARP-1. Co-treatment with an antioxidant blocked the drug effects by reducing ROS generation, cytotoxicity and pro-apoptotic signaling. In summary, novel isothiocyanate ABITC is an anti-proliferative and selectively cytotoxic drug to EC cells in-vitro. Key mechanisms during cell death are predominantly correlated to excess generation of ROS. We suggest the further development of ABITC as a potential therapeutic by studying the drug efficacy in EC in-vivo models.