Docetaxel-induced apoptosis in melanoma cells is dependent on activation of caspase-2

The Role of Caspases in Melanoma Pathogenesis

Melanoma (malignant melanoma, MM) is an aggressive malignant skin cancer with an increasing incidence rate. The complete pathogenesis of MM in not clear. Due to DNA damage, mutations, dysregulation of growth factors, inactivation of tumor suppressor genes, and activation of oncogenes, excessive uncontrolled growth of abnormal melanocytes occurs in melanomas. Caspases are a group of proteolytic enzymes that participate in several processes important in regulating mechanisms at the cellular level. They play a role in cell homeostasis and programmed cell death (apoptosis) and in the regulation of non-apoptotic cell death processes. Dysregulation of caspase activation plays a role in the etiology of cancers, including melanoma. Caspases can initiate and execute apoptosis and are involved in regulating cell death and controlling tumor growth. These enzymes also inhibit tumor growth by cleaving and inactivating proteins that are involved in cell proliferation and angiogenesis. Moreover, caspases are involved in the activation of immune processes through the processing and presentation of tumor antigens, which facilitates recognition of the tumor by the immune system. The role of caspases in melanoma is complex, and they may inhibit melanoma growth and progression. This work aims to review the current knowledge of the role of individual caspases in melanoma pathogenesis.

Apoptosis, a Metabolic "Head-to-Head" between Tumor and T Cells: Implications for Immunotherapy

Induction of apoptosis represents a promising therapeutic approach to drive tumor cells to death. However, this poses challenges due to the intricate nature of cancer biology and the mechanisms employed by cancer cells to survive and escape immune surveillance. Furthermore, molecules released from apoptotic cells and phagocytes in the tumor microenvironment (TME) can facilitate cancer progression and immune evasion. Apoptosis is also a pivotal mechanism in modulating the strength and duration of anti-tumor T-cell responses. Combined strategies including molecular targeting of apoptosis, promoting immunogenic cell death, modulating immunosuppressive cells, and affecting energy pathways can potentially overcome resistance and enhance therapeutic outcomes. Thus, an effective approach for targeting apoptosis within the TME should delicately balance the selective induction of apoptosis in tumor cells, while safeguarding survival, metabolic changes, and functionality of T cells targeting crucial molecular pathways involved in T-cell apoptosis regulation. Enhancing the persistence and effectiveness of T cells may bolster a more resilient and enduring anti-tumor immune response, ultimately advancing therapeutic outcomes in cancer treatment. This review delves into the pivotal topics of this multifaceted issue and suggests drugs and druggable targets for possible combined therapies.

Preparation, Optimization, and In-Vitro Evaluation of Brusatol- and Docetaxel-Loaded Nanoparticles for the Treatment of Prostate Cancer

Challenges to docetaxel use in prostate cancer treatment include several resistance mechanisms as well as toxicity. To overcome these challenges and to improve the therapeutic efficacy in heterogeneous prostate cancer, the use of multiple agents that can destroy different subpopulations of the tumor is required. Brusatol, a multitarget inhibitor, has been shown to exhibit potent anticancer activity and play an important role in drug response and chemoresistance. Thus, the combination of brusatol and docetaxel in a nanoparticle platform for the treatment of prostate cancer is expected to produce synergistic effects. In this study, we reported the development of polymeric nanoparticles for the delivery of brusatol and docetaxel in the treatment of prostate cancer. The one-factor-at-a-time method was used to screen for formulation and process variables that impacted particle size. Subsequently, factors that had modifiable effects on particle size were evaluated using a 24 full factorial statistical experimental design followed by the optimization of drug loading. The optimization of blank nanoparticles gave a formulation with a mean size of 169.1 nm ± 4.8 nm, in agreement with the predicted size of 168.333 nm. Transmission electron microscopy showed smooth spherical nanoparticles. The drug release profile showed that the encapsulated drugs were released over 24 h. Combination index data showed a synergistic interaction between the drugs. Cell cycle analysis and the evaluation of caspase activity showed differences in PC-3 and LNCaP prostate cancer cell responses to the agents. Additionally, immunoblots showed differences in survivin expression in LNCaP cells after treatment with the different agents and formulations for 24 h and 72 h. Therefore, the nanoparticles are potentially suitable for the treatment of advanced prostate cancer.

Gene Regulations upon Hydrogel-Mediated Drug Delivery Systems in Skin Cancers-An Overview

The incidence of skin cancer has increased dramatically in recent years, particularly in Caucasian populations. Specifically, the metastatic melanoma is one of the most aggressive cancers and is responsible for more than 80% of skin cancer deaths around the globe. Though there are many treatment techniques, and drugs have been used to cure this belligerent skin cancer, the side effects and reduced bioavailability of drug in the targeted area makes it difficult to eradicate. In addition, cellular metabolic pathways are controlled by the skin cancer driver genes, and mutations in these genes promote tumor progression. Consequently, the MAPK (RAS-RAF-MEK-ERK pathway), WNT and PI3K signaling pathways are found to be important molecular regulators in melanoma development. Even though hydrogels have turned out to be a promising drug delivery system in skin cancer treatment, the regulations at the molecular level have not been reported. Thus, we aimed to decipher the molecular pathways of hydrogel drug delivery systems for skin cancer in this review. Special attention has been paid to the hydrogel systems that deliver drugs to regulate MAPK, PI3K-AKT-mTOR, JAK-STAT and cGAS-STING pathways. These signaling pathways can be molecular drivers of skin cancers and possible potential targets for the further research on treatment of skin cancers.

Role of JNK activation in paclitaxel-induced apoptosis in human head and neck squamous cell carcinoma

It has been reported that paclitaxel activates cell cycle arrest and increases caspase protein expression to induce apoptosis in head and neck squamous cell carcinoma (HNSCC) cell lines. However, the potential signaling pathway regulating this apoptotic phenomenon remains unclear. The present study used OEC-M1 cells to investigate the underlying molecular mechanism of paclitaxel-induced apoptosis. Following treatment with paclitaxel, cell viability was assessed via the MTT assay. Necrosis, apoptosis, cell cycle and mitochondrial membrane potential (∆Ψm) were analyzed via flow cytometric analyses, respectively. Western blot analysis was performed to detect the expression levels of proteins associated with the MAPK and caspase signaling pathways. The results demonstrated that low-dose paclitaxel (50 nM) induced apoptosis but not necrosis in HNSCC cells. In addition, paclitaxel activated the c-Jun N-terminal kinase (JNK), but not extracellular signal-regulated kinase or p38 mitogen-activated protein kinase. The paclitaxel-activated JNK contributed to paclitaxel-induced apoptosis, activation of caspase-3, -6, -7, -8 and -9, and reduction of ∆Ψm. In addition, caspase-8 and -9 inhibitors, respectively, significantly decreased paclitaxel-induced apoptosis. Notably, Bid was truncated following treatment with paclitaxel. Taken together, the results of the present study suggest that paclitaxel-activated JNK is required for caspase activation and loss of ∆Ψm, which results in apoptosis of HNSCC cells. These results may provide mechanistic basis for designing more effective paclitaxel-combining regimens to treat HNSCC.

Redox imbalance induced by docetaxel in the neuroblastoma SH-SY5Y cells: a study of docetaxel-induced neuronal damage

Objectives

In cancer survivors, chemotherapy-associated adverse neurological effects are described as side effects in non-targeted tissue. We investigated the role of redox-imbalance in neuronal damage by a relative low dose of Docetaxel (DTX).

Methods

The neuroblastoma cells (SH-SY5Y cells) were exposed to DTX at a dose of 1.25 nM for 6 h. Antioxidant defenses (i.e. ascorbic acid, glutathione, and catalase) and lipid oxidation products (i.e. F₂-isoprostanes) were evaluated. To investigate cell ultrastructure and tubulin localisation, transmission electron microscopy (TEM) and immunofluorescence techniques were applied.

Results

In the SH-SY5Y cells, DTX induced a significant reduction of total glutathione (P < 0.001) and ascorbic acid (P < 0.05), and an increase in both total F₂-Isoprostanes (P < 0.05) and catalase activity (P < 0.05), as compared to untreated cells. Additionally, TEM showed a significant increase in cells with apoptotic characteristics. Immunolocalisation of tubulin showed a compromised cytoskeletal organisation.

Discussion

The investigated sublethal dose of DTX, to which non-targeted cells may be exposed throughout the duration of chemotherapy treatment, induces a redox imbalance resulting in a specific modulation of the antioxidant response. This study provides new insights into DTX-induced cellular mechanisms useful for evaluating whether the concomitant use of antioxidants associated with chemotherapy mitigates chemotherapy side effects in cancer survivors.

Dolabellane and Clerodane Diterpenoids from the Twigs and Leaves of Casearia kurzii

A pair of enantiomeric 15-nordolabellane diterpenoids, (-)- and (+)-caseadolabellols A (1a and 1b), three dolabellane diterpenoids, caseadolabellols B-D (2-4), two dolastane diterpenoids, caseadolastols A and B (5 and 6), 10 clerodane diterpenoids, caseakurzins A-J (7-16), and nine known diterpenoids (17-25) were isolated from the twigs and leaves of Casearia kurzii. The structures of the new compounds were established on the basis of extensive spectroscopic data, and those of compounds 1a, 1b, and 2 were verified by single-crystal X-ray crystallographic analysis. The enantiomers 1a and 1b were separated by chiral-phase HPLC. The absolute configurations were determined by experimental and calculated ECD data, the modified Mosher's method, or literature comparison. Compounds 1a and 5 showed significant quinone reductase-inducing activity in Hepa 1c1c7 cells, while 1b showed moderate activity. Molecular docking studies showed that 1a had greater binding affinity with Nrf2 protein (5FNQ) than 1b. The cytotoxic activity of compounds 1a, 1b, 2-12, 15, and 16 was evaluated, among which compounds 8 and 16 exhibited significant inhibitory activity against the A549 cell line. Compounds 8 and 16 induced the A549 cells to arrest at G2/M and S phases, respectively, and both compounds induced apoptosis in A549 cells.

Microtubule-targeting agents and their impact on cancer treatment

Microtubule-targeting agents (MTAs) constitute a diverse group of chemical compounds that bind to microtubules and affect their properties and function. Disruption of microtubules induces various cellular responses often leading to cell cycle arrest or cell death, the most common effect of MTAs. MTAs have found a plethora of practical applications in weed control, as fungicides and antiparasitics, and particularly in cancer treatment. Here we summarize the current knowledge of MTAs, the mechanisms of action and their role in cancer treatment. We further outline the potential use of MTAs in anti-metastatic therapy based on inhibition of cancer cell migration and invasiveness. The two main problems associated with cancer therapy by MTAs are high systemic toxicity and development of resistance. Toxic side effects of MTAs can be, at least partly, eliminated by conjugation of the drugs with various carriers. Moreover, some of the novel MTAs overcome the resistance mediated by both multidrug resistance transporters as well as overexpression of specific β-tubulin types. In anti-metastatic therapy, MTAs should be combined with other drugs to target all modes of cancer cell invasion.

Docetaxel Combined with Thymoquinone Induces Apoptosis in Prostate Cancer Cells via Inhibition of the PI3K/AKT Signaling Pathway

Toxicity and the development of resistance by cancer cells are impediments for docetaxel (DTX), a primary drug for treating prostate cancer (PCa). Since the combination of DTX with natural compounds can increase its effectiveness by reducing its toxic concentrations, we evaluated a combination of thymoquinone (TQ) with DTX and determined its cytotoxicity against PCa cells (DU145 and C4-2B). This combination, in a concentration-dependent manner, resulted in synergistic cytotoxicity and apoptosis in comparison to either DTX or TQ alone. In addition, inhibition of cell survival pathways by PI3K/AKT inhibitors conferred sensitivity of DU145 and C4-2B cells to the combination as compared to the individual drugs. Moreover, the combined drugs (DTX+TQ) with inhibitors of PI3K/AKT increased the expression of pro-apoptotic markers (BAX and BID) along with caspase-3, PARP and decreased expression of the anti-apoptotic marker, BCL-XL. These data show that, for PCa cells, the cytotoxic effect of the DTX and TQ combination correlates with a block of the PI3K/AKT signaling pathway. These findings indicate that the combination of DTX and TQ, by blocking of the PI3K/AKT pathway, will improve the survival rate and quality of life of PCa patients.

Inhibition of Caspase-2 Translation by the mRNA Binding Protein HuR: A Novel Path of Therapy Resistance in Colon Carcinoma Cells?

An increased expression and cytoplasmic abundance of the ubiquitous RNA binding protein human antigen R (HuR) is critically implicated in the dysregulated control of post- transcriptional gene expression during colorectal cancer development and is frequently associated with a high grade of malignancy and therapy resistance. Regardless of the fact that HuR elicits a broad cell survival program by increasing the stability of mRNAs coding for prominent anti-apoptotic factors, recent data suggest that HuR is critically involved in the regulation of translation, particularly, in the internal ribosome entry site (IRES) controlled translation of cell death regulatory proteins. Accordingly, data from human colon carcinoma cells revealed that HuR maintains constitutively reduced protein and activity levels of caspase-2 through negative interference with IRES-mediated translation. This review covers recent advances in the understanding of mechanisms underlying HuR's modulatory activity on IRES-triggered translation. With respect to the unique regulatory features of caspase-2 and its multiple roles (e.g., in DNA-damage-induced apoptosis, cell cycle regulation and maintenance of genomic stability), the pathophysiological consequences of negative caspase-2 regulation by HuR and its impact on therapy resistance of colorectal cancers will be discussed in detail. The negative HuR-caspase-2 axis may offer a novel target for tumor sensitizing therapies.

Frankincense essential oil suppresses melanoma cancer through down regulation of Bcl-2/Bax cascade signaling and ameliorates heptotoxicity via phase I and II drug metabolizing enzymes

Melanoma is a deadly form of malignancy and according to the World Health Organization 132,000 new cases of melanoma are diagnosed worldwide each year. Surgical resection and chemo/drug treatments opted for early and late stage of melanoma respectively, however detrimental post surgical and chemotherapy consequences are inevitable. Noticeably melanoma drug treatments are associated with liver injuries such as hepatitis and cholestasis which are very common. Alleviation of these clinical manifestations with better treatment options would enhance prognosis status and patients survival. Natural products which induce cytotoxicity with minimum side effects are of interest to achieve high therapeutic efficiency. In this study we investigated anti-melanoma and hepatoprotective activities of frankincense essential oil (FEO) in both in vitro and in vivo models. Pretreatment with FEO induce a significant (p < 0.05) dose-dependent reduction in the cell viability of mouse (B16-F10) and human melanoma (FM94) but not in the normal human epithelial melanocytes (HNEM). Immunoblot analysis showed that FEO induces down regulation of Bcl-2 and up regulation of BAX in B16-F10 cells whereas in FM94 cells FEO induced dose-dependent cleavage of caspase 3, caspase 9 and PARP. Furthermore, FEO (10 μg/ml) treatment down regulated MCL1 in a time-dependent manner in FM94 cells. In vivo toxicity analysis reveals that weekly single dose of FEO (1200 mg/kg body weight) did not elicit detrimental effect on body weight during four weeks of experimental period. Histology of tissue sections also indicated that there were no observable histopathologic differences in the brain, heart, liver, and kidney compare to control groups. FEO (300 and 600 mg/kg body weight) treatments significantly reduced the tumor burden in C57BL/6 mice melanoma model. Acetaminophen (750 mg/kg body weight) was used to induce hepatic injury in Swiss albino mice. Pre treatment with FEO (250 and 500 mg/kg body weight) for seven days retained hematology (complete blood count), biochemical parameters (AST, ALT, ALK, total bilirubin, total protein, glucose, albumin/globulin ratio, cholesterol and triglyceride), and the level of phase I and II drug metabolizing enzymes (cytochrome P450, cytochromeb5, glutathione-S-transferase) which were obstructed by the administration of acetaminophen. Further liver histology showed that FEO treatments reversed the damages (central vein dilation, hemorrhage, and nuclei condensation) caused by acetaminophen. In conclusion, FEO elicited marked anti-melanoma in both in vitro and in vivo with a significant heptoprotection.

A novel spheroid-based co-culture model mimics loss of keratinocyte differentiation, melanoma cell invasion, and drug-induced selection of ABCB5-expressing cells

Background

Different 3D-cell culture approaches with varying degrees of complexity have been developed to serve as melanoma models for drug testing or mechanistic studies. While these 3D-culture initiatives are already often superior to classical 2D approaches, they are either composed of only melanoma cells or they are so complex that the behavior of individual cell types is hard to understand, and often they are difficult to establish and expensive.

Methods

This study used low-attachment based generation of spheroids composed of up to three cell types. Characterization of cells and spheroids involved cryosectioning, immunofluorescence, FACS, and quantitative analyses. Statistical evaluation used one-way ANOVA with post-hoc Tukey test or Student’s t-test.

Results

The tri-culture model allowed to track cellular behavior in a cell-type specific manner and recapitulated different characteristics of early melanoma stages. Cells arranged into a collagen-IV rich fibroblast core, a ring of keratinocytes, and groups of highly proliferating melanoma cells on the outside. Regularly, some melanoma cells were also found to invade the fibroblast core. In the absence of melanoma cells, the keratinocyte ring stratified into central basal-like and peripheral, more differentiated cells. Conversely, keratinocyte differentiation was clearly reduced upon addition of melanoma cells. Treatment with the cytostatic drug, docetaxel, restored keratinocyte differentiation and induced apoptosis of external melanoma cells. Remaining intact external melanoma cells showed a significantly increased amount of ABCB5-immunoreactivity.

Conclusions

In the present work, a novel, simple spheroid-based melanoma tri-culture model composed of fibroblasts, keratinocytes, and melanoma cells was described. This model mimicked features observed in early melanoma stages, including loss of keratinocyte differentiation, melanoma cell invasion, and drug-induced increase of ABCB5 expression in external melanoma cells.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5606-4) contains supplementary material, which is available to authorized users.

Docetaxel-Loaded Hyaluronic Acid-Cathepsin B-Cleavable-Peptide-Gold Nanoparticles for the Treatment of Cancer

Gold nanoparticles are commonly used for medical applications such as drug delivery and as therapeutic and diagnostic materials because of their unique properties. In this study, we prepared docetaxel (DTX)-loaded hyaluronic acid-cleavable-peptide-gold nanoparticles for the treatment of cancer by selectively delivering DTX into the tumor and, thus, enhancing the therapeutic effect of DTX; further, we determined synergistic effects of the nanoparticles using laser treatment. The DTX-loaded hyaluronic acid-cleavable-peptide-gold nanoparticles prepared in this study had an average size of 75 nm and negative surface charge. The nanoparticles revealed greater cytotoxicity and higher tumor suppression efficacy in tumor models than free DTX under near-infrared laser irradiation. Therefore, the nanoparticle formulation prepared in this study could be utilized for targeted drug delivery and in combination with other cancer therapies.

Poly(ADP-ribose) polymerase-3 overexpression is associated with poor prognosis in patients with breast cancer following chemotherapy

Double strand breaks induced by genotoxic agents, if inappropriately repaired, will cause cell death or induce cancer. Poly(ADP-ribose) polymerase-3 (PARP-3) serves a role in double strand break repair, and may be involved in tumorigenesis. To the best of our knowledge, the role of PARP-3 in breast cancer has not yet been examined. In the present study, the expression of PARP-3 was investigated in 493 breast cancer samples and 54 tumor-adjacent control samples using tissue-microarray-based immunohistochemistry. PARP-3 expression was higher in breast cancer samples compared with control samples. PARP-3 overexpression was significantly associated with histological grade II–III (P=0.012). In addition, PARP-3 overexpression was significantly associated with shorter disease-free survival (DFS; P=0.027) time and exhibited a tendency toward shorter overall survival (OS; P=0.183) time in patients with breast cancer compared with patients with lower PARP-3 expression, particularly in BRCA1-positive patients (P=0.004 for disease-free survival and P=0.095 for OS). Multivariate Cox regression analysis indicated that PARP-3 was an independent prognostic factor in patients with breast cancer. Furthermore, it was revealed that PARP-3 overexpression was associated with shorter survival time in patients with cyclophosphamide/doxorubicin or epirubicin/5-fluorouracil (CAF/CEF) chemotherapy compared with low PARP-3 expression, but not in patients with CAF/CEF + docetaxel chemotherapy. The present study suggested that PARP-3 may be used as a biomarker for predicting the clinical outcome of patients receiving chemotherapy, and targeting PARP-3 may be a potential therapeutic strategy for the treatment of breast cancer.

Inhibition of IRES-dependent translation of caspase-2 by HuR confers chemotherapeutic drug resistance in colon carcinoma cells

HuR plays an important role in tumor cell survival mainly through posttranscriptional upregulation of prominent anti-apoptotic genes. In addition, HuR can inhibit the translation of pro-apoptotic factors as we could previously report for caspase-2. Here, we investigated the mechanisms of caspase-2 suppression by HuR and its contribution to chemotherapeutic drug resistance of colon carcinoma cells. In accordance with the significant drug-induced increase in cytoplasmic HuR abundance, doxorubicin and paclitaxel increased the interaction of cytoplasmic HuR with the 5ʹuntranslated region (5ʹUTR) of caspase-2 as shown by RNA pull down assay. Experiments with bicistronic reporter genes furthermore indicate the presence of an internal ribosome entry site (IRES) within the caspase-2-5ʹUTR. Luciferase activity was suppressed either by chemotherapeutic drugs or ectopic expression of HuR. IRES-driven luciferase activity was significantly increased upon siRNA-mediated knockdown of HuR implicating an inhibitory effect of HuR on caspase-2 translation which is further reinforced by chemotherapeutic drugs. Comparison of RNA-binding affinities of recombinant HuR to two fragments of the caspase-2-5ʹUTR by EMSA revealed a critical HuR-binding site residing between nucleotides 111 and 241 of caspase-2-5ʹUTR. Mapping of critical RNA binding domains within HuR revealed that a fusion of RNA recognition motif 2 (RRM2) plus the hinge region confers a full caspase-2-5ʹUTR-binding. Functionally, knockdown of HuR significantly increased the sensitivity of colon cancer cells to drug-induced apoptosis. Importantly, the apoptosis sensitizing effects by HuR knockdown were rescued after silencing of caspase-2. The negative caspase-2 regulation by HuR offers a novel therapeutic target for sensitizing colon carcinoma cells to drug-induced apoptosis.

Triphenylphosphine-docetaxel conjugate-incorporated albumin nanoparticles for cancer treatment

Aim: The objective of this study was to develop a mitochondria-targeted anticancer drug, docetaxel (DTX), for chemotherapy. Materials & methods: The DTX was conjugated to 4-carboxybutyl triphenylphosphonium (TPP) to enhance mitochondrial targeting, and the TPP–DTX conjugate was further loaded into folate-cholesteryl albumin (FA-chol-BSA) nanoparticles (NPs) to improve its biocompatibility. Results & conclusion: In vitro studies showed that TPP–DTX and its NP primarily accumulated in the mitochondria; generated high reactive oxygen species, leading to mitochondrial disruption and cell apoptosis; and had a higher cytotoxicity against cancer cells. In vivo antitumor studies indicated that the NP significantly suppressed tumor growth compared with free drugs in xenograft tumor-bearing mice. Our results demonstrated that TPP–DTX@FA-chol-BSA NPs could be a promising mitochondria-targeted anticancer prodrug for chemotherapy.

microRNA-149 targets caspase-2 in glioma progression

Malignant gliomas are the most common form of intrinsic primary brain tumors worldwide. Alterations in microRNAs play a role in highly invasive malignant glioma, but detail mechanism still unknown. In this study, the role and mechanism of microRNA-149 (miR-149) in glioma are investigated. We show that miR-149 is expressed at substantially higher levels in glioma than in normal tissues. Stable overexpression of miR-149 augments potent prosurvival activity, as evidenced by promotion of cell viability, inhibition of apoptosis, and induced xenografted tumor growth in vivo. We further show that Caspase-2 is identified as a functional target of miR-149 and expression of caspase-2 is inversely associated with miR-149 in vitro. In addition, miR-149 promotes tumor survival in the U87-MG and A172 cell lines and it targets caspase-2 via inactivation of the p53 and p21 pathways. There results support a special role for miR-149 by targeting Caspase-2 to impact on p53 signaling pathway. We speculate that miR-149 has distinct biological functions in p53 wild type cells and p53 mutation cells, and the mechanisms involved remain to be explored in future. Our study suggests that targeting miR-149 may be a novel therapy strategy for treating p53 wild type glioma tumors in humans.

Opa-interacting protein 5 modulates docetaxel-induced cell death via regulation of mitophagy in gastric cancer

Damage to mitochondria induces mitophagy, a cellular process that is gaining interest for its therapeutic relevance to a variety of human diseases. However, the mechanism underlying mitochondrial depolarization and clearance in mitophagy remains poorly understood. We previously reported that mitochondria-induced cell death was caused by knockdown of Neisseria gonorrhoeae opacity-associated-interacting protein 5 in gastric cancer. In this study, we show that Neisseria gonorrhoeae opacity-associated-interacting protein 5 loss and gain of function modulates mitophagy induced by treatment with docetaxel, a chemotherapy drug for gastric cancer. The activation of mitophagy by Neisseria gonorrhoeae opacity-associated-interacting protein 5 overexpression promoted cell survival, preventing docetaxel-induced mitochondrial clearance. Conversely, short interfering RNA-mediated knockdown of Neisseria gonorrhoeae opacity-associated-interacting protein 5 accelerated docetaxel-induced apoptosis while increasing mitochondrial depolarization, reactive oxygen species, and endoplasmic reticulum stress and decreasing adenosine triphosphate production. We also found that the mitochondrial outer membrane proteins mitofusin 2 and phosphatase and tensin homolog-induced putative kinase 1 colocalized with Neisseria gonorrhoeae opacity-associated-interacting protein 5 in mitochondria and that mitofusin 2 knockdown altered Neisseria gonorrhoeae opacity-associated-interacting protein 5 expression. These findings indicate that Neisseria gonorrhoeae opacity-associated-interacting protein 5 modulates docetaxel-induced mitophagic cell death and therefore suggest that this protein comprises a potential therapeutic target for gastric cancer treatment.

Role of the HTLV-1 viral factors in the induction of apoptosis

Adult T-cell leukemia (ATL) and HTLV-1-associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP) are the two main diseases that are caused by the HTLV-1 virus. One of the features of HTLV-1 infection is its resistance against programmed cell death, which maintains the survival of cells to oncogenic transformation and underlies the viruses' therapeutic resistance. Two main genes by which the virus develops cancer are Tax and HBZ; playing an essential role in angiogenesis in regulating viral transcription and modulating multiple host factors as well as apoptosis pathways. Here we have reviewed by prior research how the apoptosis pathways are suppressed by the Tax and HBZ and new drugs which have been designed to deal with this suppression.

Lipoxin A4 selectively programs the profile of M2 tumor-associated macrophages which favour control of tumor progression

In tumor microenvironments, the macrophage population is heterogeneous, but some macrophages can acquire tumor-promoting characteristics. These tumor-associated macrophages (TAM) exhibit an M2-like profile, with deficient production of NO and ROS, characteristics of pro-inflammatory M1 cytotoxic macrophages. Lipoxins (LX) and 15-epi-lipoxins are lipid mediators which can induce certain features of M2 macrophages in mononuclear cells, but their effects on TAM remain to be elucidated. This study tested the hypothesis that ATL-1, a synthetic analogue of 15-epi-lipoxin A₄ , could modulate TAM activity profile. We show that human macrophages (MΦ) differentiated into TAM-like cells after incubation with conditioned medium from MV3, a human melanoma lineage cell. Contrasting with the effects observed in other M2 subsets and M1 profile macrophages, ATL-1 selectively decreased M2 surface markers in TAM, suggesting unique behavior of this particular M2 subset. Importantly, these results were replicated by the natural lipoxins LXA₄ and the aspirin induced 15-epi-LXA₄ (ATL). In parallel, ATL-1 stimulated TAM to produce NO by increasing the iNOS/arginase ratio and activated NADPH oxidase, triggering ROS production. These alterations in TAM profile induced by ATL-1 led to loss of the anti-apoptotic effects of TAM on melanoma cells and increased their cytotoxic properties. Finally, ATL-1 was found to inhibit tumor progression in a murine model in vivo, which was accompanied by alterations in TAM profile and diminished angiogenesis. Together, the results show an unexpected effect of lipoxin, which induces in TAM a change from an M2- to an M1-like profile, thereby triggering tumor cell apoptosis and down-modulating the tumor progression.

FoxM1 inhibition enhances chemosensitivity of docetaxel-resistant A549 cells to docetaxel via activation of JNK/mitochondrial pathway

Docetaxel is recommended as a second-line chemotherapy agent for the non-small-cell lung cancer (NSCLC); however, drug resistance greatly limits its efficiency. Forkhead box M1 (FoxM1), an oncogenic transcription factor, is believed to be involved in the chemoresistance of various human cancers; whereas the association of FoxM1 with acquired docetaxel-resistance in NSCLC remains unclear. In the present study, we investigated the involvement of FoxM1 in the docetaxel-resistant human lung adenocarcinoma A549 cells (A549/DTX). Our results showed that FoxM1 expression was significantly increased in the A549/DTX cells compared with that in the parental A549 cells. FoxM1 siRNA silencing promoted the cytotoxic and pro-apoptotic effect of docetaxel in A549/DTX cells, which was possibly mediated through inducing the activation of c-Jun N-terminal kinases/mitochondrial signaling pathway. Our results suggest a critical role of FoxM1 in docetaxel-resistance of the A549 cells and form the basis for the development of combined therapy of docetaxel and FoxM1 depletion in treating NSCLC.

Cytotoxic Rocaglate Derivatives from Leaves of Aglaia perviridis

Rocaglates are a series of structurally complex secondary metabolites with considerable cytotoxicity that have been isolated from plants of the Aglaia genus (Meliaceae). A new rocaglate (aglapervirisin A, 1) and its eight new biosynthetic precursors of rocaglate (aglapervirisins B-J, 2-9) together with five known compounds, were isolated from the leaves of Aglaia perviridis. Their structures were elucidated based on a joint effort of spectroscopic methods [IR, UV, MS, ECD, 1D- and 2D-NMR, HRESIMS], chemical conversion and single-crystal X-ray diffraction. Among these isolates, three (1, 10-11) were silvestrols, a rare subtype rocaglates, exhibiting notable cytotoxicity against four human tumor cell lines, with IC50 values between 8.0 and 15.0 nM. Aglapervirisin A (1) induces cell cycle arrest at the G2/M-phase boundary at concentration 10 nM accompanied by reductions in the expression levels of Cdc2 and Cdc25C in HepG2 cells after 72h co-incubation, and further induces the apoptosis of HepG2 cells at concentrations over 160 nM.

Inhibition of mitogen-activated protein kinase signaling pathway sensitizes breast cancer cells to endoplasmic reticulum stress-induced apoptosis

Accumulation of unfolded proteins in the endoplasmic reticulum (ER) induces ER stress which is observed in many human diseases, including breast cancer. Cellular adaptation to ER stress is mediated by the unfolded protein response (UPR), which aims at restoring ER homeostasis. Higher levels of GRP78 expression indicates constitutive activation of the UPR in breast cancer leading to breast cancer cells that are relatively resistant to ER stress-induced apoptosis. Tunicamycin (TM), an ER stress inducer, constitutively activates the mitogen-activated protein kinase (MAPK)/extracellular signal regulated kinase (ERK), and (MEK)/ERK pathway which plays a role in upregulation of GRP78 by ER stress in that inhibition of MEK by U0126 reduces the levels of GRP78 and blocks its upregulation by TM. Inhibition of the MEK/ERK pathway by U0126 sensitizes breast cancer cells to TM-induced apoptosis. Inhibition of GRP78 by siRNA knockdown enhances TM- and U0126-induced apoptosis in breast cancer cells. This sensitization of breast cancer cells to TM-induced apoptosis by inhibition of MEK/ERK and GRP78 is caspase-dependent, at least in part, by activation of caspase-4. These results seem to indicate that GRP78 has potential as a chemotherapeutical target and have important implications for new treatment strategies in breast cancer by combination with agents that induce ER stress with inhibitors of the MEK/ERK pathway.

Anti-cancer properties of a sesquiterpene lactone-bearing fraction from Artemisia khorassanica

BACKGROUND

Artemisia species are important medicinal plants throughout the world. The present in vitro study, using a sesquiterpene lactone-bearing fraction prepared from Artemisia khorassanica (SLAK), sought to investigate anti-cancer properties of this plant and elucidate potential underlying mechanisms for the effects.

MATERIALS AND METHODS

Anti-cancer potential was evaluated by toxicity against human melanoma and fibroblast cell lines. To explore the involved pathways, pattern of any cell death was determined using annexin-V/PI staining and also the expression of Bax and cytochrome c was investigated by Western blotting.

RESULTS

The results showed that SLAK selectively caused a concentration-related inhibition of proliferation of melanoma cells that was associated with remarkable increase in early events and over-expression of both Bax and cytochrome c.

CONCLUSIONS

The current experiment indicates that Artemisia may have anti-cancer activity. We anticipate that the ingredients may be employed as therapeutic candidates for melanoma.

Silencing of TGM2 reverses epithelial to mesenchymal transition and modulates the chemosensitivity of breast cancer to docetaxel

Epithelial to mesenchymal transition (EMT) plays a critical role in drug resistance. The aim of the present study was to further elucidate its role by examining the effect of tissue transglutaminase (TG2) on EMT and drug resistance in breast cancer. An antisense lentiviral (LV) short hairpin (sh)RNA construct specific to the TG2 gene (TGM2) was designed, synthesized and stably transfected into MDA-MB-231 cells to silence TGM2 by RNA interference (RNAi). The transfected cells expressed low levels of TG2 and constituted the RNAi (TGM2-shRNA) group. A control (NC) group was also established by transfecting MDA-MB-231 cells with scrambled shRNA. The expression levels of TG2, E-cadherin, vimentin and B-cell lymphoma (Bcl)-2 in the cells were examined via western blotting. The transfected MDA-MB-231 cells were divided into four groups, two of which were treated with doxetaxel (TXT): NC, RNAi, TXT and RNAi + TXT groups,. Cell proliferation was analyzed by MTT assay and cell apoptosis was detected by flow cytometry. An in vivo assay was also conducted, in which MDA-MB-231 cells transfected with scrambled shRNA or TGM2-shRNA were subcutaneously implanted into nude mice. After 2 weeks, TXT or vehicle was intraperitoneally administered at a dose of 10 mg/kg on day 1 of every week and tumor growth was monitored. Following the silencing of TGM2 in the MDA-MB-231 cells, the cells showed changes in morphology, indicating that an increased expression of TG2 was associated with a mesenchymal morphology. Transfection of the cells with TGM2-shRNA affected the expression of TG2, E-cadherin, vimentin and Bcl-2. In the MTT assay, the proliferation of MDA-MB-231 cells was significantly inhibited in the RNAi group compared with the control group (P<0.05), and the inhibitory effect increased in a time-dependent manner. Following treatment with TXT for 48 h, apoptosis was significantly promoted in the RNAi + TXT group compared with that in the other groups (P<0.05). Measurement of the tumors in the nude mice indicated that the combination of RNAi and TXT brought about a stronger antitumor effect than either treatment alone. These results suggest that the downregulation of TG2 reversed EMT and modulated the chemosensitivity of breast cancer to TXT. TG2 may be an important predictive and prognostic factor for the treatment efficacy of chemotherapy in patients with breast cancer.

Regulation of BAX/BCL2 gene expression in breast cancer cells by docetaxel-loaded human serum albumin nanoparticles

Today, using nanoparticle-based drug delivery systems has expanded to avoid anticancer side effects. Taxanes are important chemotherapeutic agents in the treatment of metastatic breast cancer. In this study, docetaxel (DTX)-loaded human serum albumin (HSA) nanoparticles (NPs) were prepared and characterized. Drug toxicity of the nanoparticles was measured by MTT assay with different drug concentrations (0.01, 0.1, 0.5, 1 and 5 μM) at different incubation times (24, 48 and 72 h). Expression of BAX/BCL2 mRNA levels was determined by real-time PCR. The size of NPs prepared and used in our study was about 147 nm with surface charge of -29.6 mV. Results obtained from MTT assay showed that 0.5 μM of free drug had 50 % toxicity on MCF-7 cells after 48-h incubation. Real-time PCR results showed an increase in expression of BAX and no change for BCL2. In conclusion, a significant overexpression of BAX gene and changes in BAX/BCL2 ratio were observed for DTX-loaded HSA nanoparticles compared with free DTX and may provide a potential therapy to inhibit anticancer drug resistance.

Results of a Phase II Study to Evaluate the Efficacy of Docetaxel and Carboplatin in Metastatic Malignant Melanoma Patients Who Failed First-Line Therapy Containing Dacarbazine

PURPOSE

There is no standard second-line regimen for malignant melanoma patients with disease progression after first-line chemotherapy, and platinum-alkylating agents combined with paclitaxel have shown modest efficacy.

MATERIALS AND METHODS

We conducted a phase II, open-label, single-arm study to test the efficacy of docetaxel combined with carboplatin for malignant melanoma patients who failed previous treatment with dacarbazine. Intravenous docetaxel (35 mg/m(2) on days 1 and 8 of each cycle) and carboplatin (area under the curve 3 on days 1 and 8 of each cycle) was administered every 21 days. Primary end point was objective response rate (ORR).

RESULTS

Thirty patients were enrolled in the study, and the median follow-up duration was 19.8 months. Among 25 per-protocol patients, there were three responders (1 with complete response and 2 with partial response) and 17 stable disease patients (ORR, 12.0%). Among the per-protocol population, the median progression-free survival (PFS) was 4.3 months and the median overall survival (OS) was 9.6 months. Uveal melanoma patients (n=9) showed the best prognosis compared to other subtypes (median PFS, 7.6 months; OS, 9.9 months). The most common grade 3 or 4 adverse event was neutropenia (n=15, 50.0%).

CONCLUSION

Docetaxel combined with carboplatin showed association with an acceptable safety profile and overall efficacy for patients with malignant melanoma who had progressed on chemotherapy containing dacarbazine.

The role of individual caspases in cell death induction by taxanes in breast cancer cells

Background

In previous study we showed that caspase-2 plays the role of an apical caspase in cell death induction by taxanes in breast cancer cells. This study deals with the role of other caspases. We tested breast cancer cell lines SK-BR-3 (functional caspase-3) and MCF-7 (nonfunctional caspase-3).

Methods and results

Using western blot analysis we demonstrated the activation of initiator caspase-8 and -9 as well as executioner caspase-6 and -7 in both tested cell lines after application of taxanes (paclitaxel, SB-T-1216) at death-inducing concentrations. Caspase-3 activation was also found in SK-BR-3 cells. Employing specific siRNAs after taxane application, suppression of caspase-3 expression significantly increased the number of surviving SK-BR-3 cells. Inhibition of caspase-7 expression also increased the number of surviving SK-BR-3 and MCF-7 cells. On the other hand, suppression of caspase-8 and caspase-9 expression had no significant effect on cell survival. However, caspase-9 seemed to be involved in the activation of caspase-3 and caspase-7. Caspase-3 and caspase-7 appeared to activate mutually. Furthermore, we observed a significant decrease in mitochondrial membrane potential (flow cytometric analysis) and cytochrome c release (confocal microscopy, western blot after cell fractionation) from mitochondria in SK-BR-3 cells. No such changes were observed in MCF-7 cells after taxane treatment.

Conclusion

We conclude that the activation of apical caspase-2 results in the activation of caspase-3 and -7 without the involvement of mitochondria. Caspase-9 can be activated directly via caspase-2 or alternatively after cytochrome c release from mitochondria. Subsequently, caspase-9 activation can also lead to caspase-3 and -7 activations. Caspase-3 and caspase-7 activate mutually. It seems that there is also a parallel pathway involving mitochondria that can cooperate in taxane-induced cell death in breast cancer cells.

Diterpenoids from the Chinese liverwort Heteroscyphus tener and their antiproliferative effects

Four new ent-labdane diterpenoids, heteroscyphins A-D (1-4), and four known diterpenoids (5-8) were isolated from the Chinese liverwort Heteroscyphus tener (Steph.) Schiffn. The absolute configuration of compound 1 was defined by single-crystal X-ray diffraction using Cu Kα radiation. Cytotoxicity tests revealed that compounds 3 and 5 exhibited modest activity against seven cancer cell lines. Compound 5 showed inhibitory effects on prostate cancer (PCa) cell proliferation but with less inhibition on non-neoplastic prostate epithelial cells. Compound 5 markedly caused cell growth arrest at the G0/G1 phase and induced cellular apoptosis through ROS-mediated DNA damage in PCa cells.

5-Fluorouracil-induced apoptosis in colorectal cancer cells is caspase-9-dependent and mediated by activation of protein kinase C-δ

Elucidation of the molecular mechanisms by which 5-fluorouracil (5-FU) induces apoptosis is required in order to understand the resistance of colorectal cancer (CRC) cells to 5-FU. In the current study, 5-FU-induced apoptosis was assessed using the propidium iodide method. Involvement of protein kinase C (PKC) was assessed by evaluating the extent of their activation in CRC, following treatment with 5-FU, using biochemical inhibitors and western blot analysis. The results revealed that 5-FU induces varying degrees of apoptosis in CRC cells; HCT116 cells were identified to be the most sensitive cells and SW480 were the least sensitive. In addition, 5-FU-induced apoptosis was caspase-dependent as it appeared to be initiated by caspase-9. Furthermore, PKCɛ was marginally expressed in CRC cells and no changes were observed in the levels of cleavage or phosphorylation following treatment with 5-FU. The treatment of HCT116 cells with 5-FU increased the expression, phosphorylation and cleavage of PKCδ. The inhibition of PKCδ was found to significantly inhibit 5-FU-induced apoptosis. These results indicated that 5-FU induces apoptosis in CRC by the activation of PKCδ and caspase-9. In addition, the levels of PKCδ activation may determine the sensitivity of CRC to 5-FU.

DOC-MEK: a double-blind randomized phase II trial of docetaxel with or without selumetinib in wild-type BRAF advanced melanoma

BACKGROUND

Treatment options for wild-type BRAF melanoma patients remain limited. Selumetinib, a MEK 1/2 inhibitor, suppresses pERK levels independent of BRAF and NRAS mutation status, and combination with docetaxel has demonstrated synergy in xenograft models. The aim of this study was to assess the efficacy and safety of selumetinib plus docetaxel as first-line treatment in patients with wild-type BRAF advanced melanoma.

PATIENTS AND METHODS

In this double-blind multicentre phase II trial patients with wild-type BRAF melanoma were randomized (1:1) to docetaxel with selumetinib or placebo. Docetaxel 75 mg/m(2) was administered intravenously every 3 weeks up to six cycles. Selumetinib 75 mg or placebo was given orally twice daily until disease progression or unacceptable toxicity. The primary end point was progression-free survival (PFS). Tumour NRAS mutation status was analysed retrospectively and correlated with treatment outcomes.

RESULTS

Eighty-three patients were randomized to docetaxel plus selumetinib (n = 41) or docetaxel plus placebo (n = 42). The PFS hazard ratio (HR) (selumetinib:placebo) was 0.75 [90% confidence interval (CI) 0.50-1.14; P = 0.130], with a median PFS of 4.23 months (90% CI 3.63-6.90) for docetaxel plus selumetinib and 3.93 months (90% CI 2.07-4.16) for docetaxel alone. There was no significant difference in overall survival. The objective response rate was 32% with selumetinib versus 14% with placebo (P = 0.059). In a retrospective subset analysis, NRAS mutation status did not affect significantly upon clinical outcomes in either arm. The combination of docetaxel and selumetinib could be administered effectively to patients with metastatic melanoma, although the combination was less well tolerated than docetaxel alone.

CONCLUSIONS

The combination of docetaxel with selumetinib showed no significant improvement in PFS compared with docetaxel alone, although more patients showed a response to combination therapy. We found no evidence to support using tumour NRAS mutation as a basis for selecting patients for combined MEK inhibitor and chemotherapy.

CLINICAL TRIAL

DOC-MEK (EudraCT no: 2009-018153-23).

Analysis of the minimal specificity of caspase-2 and identification of Ac-VDTTD-AFC as a caspase-2-selective peptide substrate

Caspase-2 is an evolutionarily conserved but enigmatic protease whose biological role remains poorly understood. To date, research into the functions of caspase-2 has been hampered by an absence of reagents that can distinguish its activity from that of the downstream apoptotic caspase, caspase-3. Identification of protein substrates of caspase-2 that are efficiently cleaved within cells may also provide clues to the role of this protease. We used a yeast-based transcriptional reporter system to define the minimal substrate specificity of caspase-2. The resulting profile enabled the identification of candidate novel caspase-2 substrates. Caspase-2 cleaved one of these proteins, the cancer-associated transcription factor Runx1, although with relatively low efficiency. A fluorogenic peptide was derived from the sequence most efficiently cleaved in the context of the transcriptional reporter. This peptide, Ac-VDTTD-AFC, was efficiently cleaved by purified caspase-2 and auto-activating caspase-2 in mammalian cells, and exhibited better selectivity for caspase-2 relative to caspase-3 than reagents that are currently available. We suggest that this reagent, used in parallel with the traditional caspase-3 substrate Ac-DEVD-AFC, will enable researchers to monitor caspase-2 activity in cell lysates and may assist in the determination of stimuli that activate caspase-2 in vivo.

Novel antimitotic activity of 2-hydroxy-4-methoxy-2',3'-benzochalcone (HymnPro) through the inhibition of tubulin polymerization

The natural chalcones and their derivatives exhibit many biological activities, such as anti-inflammatory and antitumoral. However, the precise mechanisms of action of benzochalcone derivatives are currently unknown. Here, a set of benzochalcones was synthesized, and the molecular mechanisms underlying inhibition of tumor growth were investigated. Colony-forming assays revealed that among tested compounds, 2-hydroxy-4-methoxy-2',3'-benzochalcone (HymnPro) most effectively inhibited the clonogenicity of Capan-1 human pancreatic cancer cells. HymnPro inhibited cell proliferation in several human solid tumor cell lines and suppressed xenografted tumor growth in nude mice. Mechanistically, HymnPro induced cell cycle arrest at the G2/M phase, followed by an increase in apoptotic cell death. These events were associated with the inhibition of tubulin polymerization through binding of HymnPro to tubulin, leading to the formation of abnormal mono- or multipolar mitotic microtubule structures accompanied by spherical arrangement of multinucleated chromosomes. Furthermore, HymnPro activated caspase-2, caspase-9, caspase-3, and caspase-7 and increased the cleavage of poly(ADP-ribose) polymerase (PARP). HymnPro increased the phosphorylation of JNK1/2, Erk1/2, and p38 kinase. Pretreatment with SP600125, U0126, or SB600125 abrogated HymnPro-induced activation of caspases-3 and caspase-7 and the cleavage of PARP, suggesting that MAPK signalings are involved in HymnPro-induced apoptosis. It was concluded that a novel HymnPro compound exerts antitumor activity by disrupting microtubule assembly, which leads to mitotic arrest and sequential activation of the caspase pathway, resulting in apoptosis.

Elevated prx1 provides resistance to docetaxel, but is not associated with predictive significance in lung cancer

BACKGROUND

This study was conducted in order to elucidate the effects of docetaxel on the growth of peroxiredoxin 1 (Prx1) knockdown A549 xenograft tumors and further tested the role of Prx1 as a predictor for how a patient would respond to docetaxel treatment.

METHODS

Effects of docetaxel on the growth of scrambled- and shPrx1-infected A549 xenograft tumors in nude mice were measured. Moreover, immunohistochemical expression of Prx1 was evaluated in paraffin-embedded tissues from 24 non-small cell lung cancer patients who had received docetaxel-cisplatin regimens as a first-line treatment.

RESULTS

Docetaxel treatment in Prx1 knockdown xenograft tumor resulted in reduced tumors growth compared with other groups. Prx1 knockdown increased the production of cleaved caspases-8 and -9 in the control itself compared to scramble tumors. Moreover, docetaxel treatment in Prx1 knockdown tissue led to an increased protein band. Phosphorylated Akt was found in Prx1 scramble tissues. Phosphorylated FOXO1 was detected in the docetaxel treatment group. On the other hand, Prx1 knockdown completely suppressed the Akt-FOXO1 axis. The median progression-free survival (PFS) of patients with low Prx1 expression was 7 months (95% confidence interval [CI], 6.0-7.7), whereas the median progression-free survival of patients with high Prx1 expression was 4 months (95% CI, 4.0-5.0). However, high Prx1 expression was not associated with decreased PFS (p=0.114).

CONCLUSION

Our findings suggest that elevated Prx1 provides resistance to docetaxel treatment through suppression of FOXO1-induced apoptosis in A549 xenograft tumors, but may not be related with the predictive significance for response to docetaxel treatment.

Riccardin D induces cell death by activation of apoptosis and autophagy in osteosarcoma cells

Macrocyclic bisbibenzyls, characteristic components derived from liverworts, have various biological activities. Riccardin D (RD), a liverwort-derived naturally occurring macrocyclic bisbibenzyl, has been found to exert anticancer effects in multiple cancer cell types through apoptosis induction. However, the underlying mechanisms of such effects remain undefined. In addition, whether RD induces other forms of cell death such as autophagy is unknown. In this study, we found that the arrest of RD-caused U2OS (p53 wild) and Saos-2 (p53 null) cells in G1 phase was associated with the induction of p53 and p21(WAF1) in U2OS cells. RD-mediated cell cycle arrest was accompanied with apoptosis promotion as indicated by changes in nuclear morphology and expression of apoptosis-related proteins. Further studies revealed that the antiproliferation of RD was unaffected in the presence of p53 inhibitor but was partially reversed by a pan-inhibitor of caspases, suggesting that p53 was not required in RD-mediated apoptosis and that caspase-independent mechanisms were involved in RD-mediated cell death. Except for apoptosis, RD-induced autophagy occurred as evidenced by the accumulation of microtubule-associated protein-1 light chain-3B-II, formation of AVOs, punctate dots, and increased autophagic flux. Pharmacological blockade of autophagy activation markedly attenuated RD-mediated cell death. RD-induced cell death was significantly restored by the combination of autophagy and caspase inhibitors in osteosarcoma cells. Overall, our study revealed RD-induced caspase-dependent apoptosis and autophagy in cancer cells, as well as highlighted the importance of continued investigation on the use of RD as a potential anticancer candidate.

Caspase-2 is involved in cell death induction by taxanes in breast cancer cells

BACKGROUND

We studied the role of caspase-2 in apoptosis induction by taxanes (paclitaxel, novel taxane SB-T-1216) in breast cancer cells using SK-BR-3 (nonfunctional p53, functional caspase-3) and MCF-7 (functional p53, nonfunctional caspase-3) cell lines.

RESULTS

Both taxanes induced apoptosis in SK-BR-3 as well as MCF-7 cells. Caspase-2 activity in SK-BR-3 cells increased approximately 15-fold within 48 h after the application of both taxanes at the death-inducing concentration (100 nM). In MCF-7 cells, caspase-2 activity increased approximately 11-fold within 60 h after the application of taxanes (300 nM). Caspase-2 activation was confirmed by decreasing levels of procaspase-2, increasing levels of cleaved caspase-2 and the cleavage of caspase-2 substrate golgin-160. The inhibition of caspase-2 expression using siRNA increased the number of surviving cells more than 2-fold in MCF-7 cells, and at least 4-fold in SK-BR-3 cells, 96 h after the application of death-inducing concentration of taxanes. The inhibition of caspase-2 expression also resulted in decreased cleavage of initiator caspases (caspase-8, caspase-9) as well as executioner caspases (caspase-3, caspase-7) in both cell lines after the application of taxanes. In control cells, caspase-2 seemed to be mainly localized in the nucleus. After the application of taxanes, it was released from the nucleus to the cytosol, due to the long-term disintegration of the nuclear envelope, in both cell lines. Taxane application led to some formation of PIDDosome complex in both cell lines within 24 h after the application. After taxane application, p21WAF1/CIP1 expression was only induced in MCF-7 cells with functional p53. However, taxane application did not result in a significant increase of PIDD expression in either SK-BR-3 or MCF-7 cells. The inhibition of RAIDD expression using siRNA did not affect the number of surviving SK-BR-3 and MCF-7 cells after taxane application at all.

CONCLUSION

Caspase-2 is required, at least partially, for apoptosis induction by taxanes in tested breast cancer cells. We suggest that caspase-2 plays the role of an apical caspase in these cells. Caspase-2 seems to be activated via other mechanism than PIDDosome formation. It follows the release of caspase-2 from the nucleus to the cytosol.

Prx1 modulates the chemosensitivity of lung cancer to docetaxel through suppression of FOXO1-induced apoptosis

The expression levels of Prx1 are frequently elevated in several human cancers, including lung cancer and may confer increased resistance to treatment. In this study, we investigated the role of Prx1 in docetaxel-induced apoptosis in A549 lung cancer cells. To test whether Prx1 knockdown affected the sensitivity of A549 cells to docetaxel treatment, we generated short hairpin RNA (shRNA) constructs targeting Prx1 and analyzed the effect of Prx1 knockdown on growth and apoptosis. Tumor growth was evaluated in scrambled shRNA- or shPrx1-infected A549 cell tumors receiving docetaxel treatment. In addition, mechanistic information was gathered by western blot analysis from cell lysates of scrambled- and shPrx1-infected A549 cells pretreated with or without LY294002 and subsequently treated with docetaxel. We found that Prx1 knockdown resulted in enhanced docetaxel-induced cytotoxicity in a dose-dependent manner. In vivo, the growth rate of shPrx1-infected A549 tumors was significantly reduced compared to that of scrambled shRNA-infected A549 tumors. Prx1 knockdown also augmented the inhibitory effects of docetaxel on tumor growth. Prx1 knockdown increased the apoptotic potential through activation of the caspase cascade and suppressed docetaxel-induced phosphorylation of Akt and its substrate forkhead box O1 (FOXO1). Moreover, treatment with the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 reduced the phosphorylation of FOXO1 and increased the cytotoxicity of docetaxel in A549 cells. Our findings suggest that Prx1 may modulate the chemosensitivity of lung cancer to docetaxel through suppression of FOXO1-induced apoptosis.

The association of taxane resistance genes with the clinical course of ovarian carcinoma

Taxane and platinum-based chemotherapy regimens are standard treatment for advanced ovarian carcinoma. Expression levels of putative markers of taxane resistance in carcinoma tissues and paired peritoneal samples (n=55) and in 16 samples of ovaries without signs of carcinoma were compared with clinical data and the patients' time to progression. KIF14, PRC1, CIT and ABCC1 genes were significantly overexpressed in carcinomas when compared with normal ovarian tissues, while ABCB1 and CASP9 expression was decreased. Associations of protein expression of the proliferation marker Ki-67 with KIF14, PRC1, ABCB1 and CASP2 were found. Lastly, it was discovered that ABCB1 and CASP2 levels associated with FIGO stage and that the CIT level associated with the time to progression of ovarian carcinoma patients (P<0.0001). In conclusion, ABCB1, CASP2, KIF14, PRC1 and CIT genes seem to associate with surrogate markers of ovarian carcinoma progression and CIT gene associates with therapy outcome.

Discovery and evaluation of novel inhibitors of mycobacterium protein tyrosine phosphatase B from the 6-Hydroxy-benzofuran-5-carboxylic acid scaffold

Mycobacterium tuberculosis (Mtb) protein tyrosine phosphatase B (mPTPB) is a virulence factor secreted by the pathogen and mediates mycobacterial survival in macrophages by targeting host cell immune responses. Consequently, mPTPB represents an exciting new target to combat tuberculosis (TB) infection. We describe a medicinal chemistry oriented approach that transforms a benzofuran salicylic acid scaffold into a highly potent (IC(50) = 38 nM) and selective mPTPB inhibitor (>50 fold against a large panel of PTPs). Importantly, the inhibitor is capable of reversing the altered host immune responses induced by the bacterial phosphatase and restoring the macrophage's full capacity to secrete IL-6 and undergo apoptosis in response to interferon-γ stimulation, validating the concept that chemical inhibition of mPTPB may be therapeutically useful for novel TB treatment. The study further demonstrates that bicyclic salicylic acid pharmacophores can be used to deliver PTP inhibitors with high potency, selectivity, and cellular efficacy.

Synthesis and biological evaluation of 2-substituted-4-(3',4',5'-trimethoxyphenyl)-5-aryl thiazoles as anticancer agents

Antitumor agents that bind to tubulin and disrupt microtubule dynamics have attracted considerable attention in the last few years. To extend our knowledge of the thiazole ring as a suitable mimic for the cis-olefin present in combretastatin A-4, we fixed the 3,4,5-trimethoxyphenyl at the C4-position of the thiazole core. We found that the substituents at the C2- and C5-positions had a profound effect on antiproliferative activity. Comparing compounds with the same substituents at the C5-position of the thiazole ring, the moiety at the C2-position influenced antiproliferative activities, with the order of potency being NHCH(3) > Me >> N(CH(3))(2). The N-methylamino substituent significantly improved antiproliferative activity on MCF-7 cells with respect to C2-amino counterparts. Increasing steric bulk at the C2-position from N-methylamino to N,N-dimethylamino caused a 1-2 log decrease in activity. The 2-N-methylamino thiazole derivatives 3b, 3d and 3e were the most active compounds as antiproliferative agents, with IC(50) values from low micromolar to single digit nanomolar, and, in addition, they are also active on multidrug-resistant cell lines over-expressing P-glycoprotein. Antiproliferative activity was probably caused by the compounds binding to the colchicines site of tubulin polymerization and disrupting microtubule dynamics. Moreover, the most active compound 3e induced apoptosis through the activation of caspase-2, -3 and -8, but 3e did not cause mitochondrial depolarization.

Aqueous Extract of Solanum nigrum Leaf Activates Autophagic Cell Death and Enhances Docetaxel-Induced Cytotoxicity in Human Endometrial Carcinoma Cells

Chemotherapy is the main approach in dealing with advanced and recurrent endometrial cancer. An effective complementary ingredient can be helpful in improving the clinical outcome. Aqueous extract of Solanum nigrum leaf (AE-SN) is a principal ingredient for treating cancer patients in traditional Chinese medicinal practice but lacks sufficient evidence to verify its tumor suppression efficacy. This study evaluated the antitumor effects of AE-SN and also assessed the synergistic effects of AE-SN with docetaxel On the human endometrial cancer cell lines, HEC1A, HEC1B, and KLE. The activation of apoptotic markers, caspase-3 and poly-ADP-ribose polymerase, and autophagic marker, microtubule-associated protein 1 light chain 3 A/B, wAS determined to clarify the cell death pathways responsible for AE-SN induced tumor cell death. Results indicated that AE-SN-treatment has significant cytotoxicity on the tested endometrial cancer cells with accumulation of LC3 A/B II and demonstrated a synergistic effect of AE-SN and docetaxel in HEC1A and HEC1B cells, but not KLE cells. In conclusion, AE-SN treatment was effective in suppressing endometrial cancer cells via the autophagic pathway and was also capable of enhancing the cytotoxicity of docetaxel in human endometrial cancer cells. Our results provide meaningful evidence for integrative cancer therapy in the future.

Novel hydrophilic docetaxel (CQMU-0519) analogue inhibits proliferation and induces apoptosis in human A549 lung, SKVO3 ovarian and MCF7 breast carcinoma cell lines

OBJECTIVE

Objectives of this investigation were not merely to perform a comparative study with original docetaxel, but to define anti-proliferative and apoptotic effects of novel hydrophilic docetaxel (CQMU-0519) analogue on A549 lung, SKVO3 ovary and MCF7 breast carcinoma cell lines.

MATERIALS AND METHODS

The materials for the study consist of a completely new docetaxel analogue (CQMU-0519), synthesized by the Department of Pharmacology, Chongqing Medical University, China, which is completely soluble in water. 50 nm of drug concentration was utilized on all three cell lines where cell population growth was assessed using cell culture kit-8 and flow cytometry analysis, whereas apoptotic pathways were unveiled by use of annexin-V FITC, apoptosis DNA ladder, caspases-3, 6, 8 and 9; in the meanwhile, regulation of Bcl-2 family members was analysed by western blotting.

RESULT

The novel docetaxel analogue (CQMU-0519) suppressed cell proliferation in all three cell lines, inhibition of cell proliferation and cell cycle arrest being more evident in G(2) /M phase. Also, in both lung and ovarian cell lines, apoptotic levels were higher as measured by the various tests performed, and downregulation of Bcl-2 and Bcl-xL with increased expressions of Bad and Bax indicated the intrinsic pathway for apoptosis. Nevertheless, it was found that MCF7 cells, although also manifesting high levels of apoptosis, used the extrinsic pathway instead. Hence, it was shown that novel docetaxel analogue (CQMU-0519) may have some prospective use in future clinical trials.

CONCLUSIONS

Novel hydrophilic docetaxel analogue (CQMU-0519) inhibited cell proliferation and enhanced the intrinsic apoptotic pathway in lung and ovarian carcinoma cells, whereas it used the extrinsic one in breast adenocarcinoma cells.

Molecular mechanism implicated in Pemetrexed-induced apoptosis in human melanoma cells

Background

Metastatic melanoma is a lethal skin cancer and its incidence is rising every year. It represents a challenge for oncologist, as the current treatment options are non-curative in the majority of cases; therefore, the effort to find and/or develop novel compounds is mandatory. Pemetrexed (Alimta®, MTA) is a multitarget antifolate that inhibits folate-dependent enzymes: thymidylate synthase, dihydrofolate reductase and glycinamide ribonucleotide formyltransferase, required for de novo synthesis of nucleotides for DNA replication. It is currently used in the treatment of mesothelioma and non-small cell lung cancer (NSCLC), and has shown clinical activity in other tumors such as breast, colorectal, bladder, cervical, gastric and pancreatic cancer. However, its effect in human melanoma has not been studied yet.

Results

In the current work we studied the effect of MTA on four human melanoma cell lines A375, Hs294T, HT144 and MeWo and in two NSCLC cell lines H1299 and Calu-3. We have found that MTA induces DNA damage, S-phase cell cycle arrest, and caspase- dependent and –independent apoptosis. We show that an increment of the intracellular reactive oxygen species (ROS) and p53 is required for MTA-induced cytotoxicity by utilizing N-Acetyl-L-Cysteine (NAC) to blockage of ROS and p53-defective H1299 NSCLC cell line. Pretreatment of melanoma cells with NAC significantly decreased the DNA damage, p53 up-regulation and cytotoxic effect of MTA. MTA was able to induce p53 expression leading to up-regulation of p53-dependent genes Mcl-1 and PIDD, followed by a postranscriptional regulation of Mcl-1 improving apoptosis.

Conclusions

We found that MTA induced DNA damage and mitochondrial-mediated apoptosis in human melanoma cells in vitro and that the associated apoptosis was both caspase-dependent and –independent and p53-mediated. Our data suggest that MTA may be of therapeutic relevance for the future treatment of human malignant melanoma.

Camptothecin induces p53-dependent and -independent apoptogenic signaling in melanoma cells

Various DNA-targeting agents may initiate p53-dependent as well as p53-independent response and subsequent apoptosis via alternative cellular systems which include for instance p73, caspase-2 or Bcl-2 family proteins. The scope of involvement of individual molecules in this process and the mechanisms governing their potential interplay are still not entirely understood, in particular in highly aggressive cancers such as in malignant melanoma. In this work we investigated the role and involvement of both p53-dependent and -independent mechanisms in selected melanoma cell lines with differing status of p53 using a model DNA topoisomerase I inhibitor camptothecin (CPT). Here we report that CPT induced in Bowes melanoma cells apoptosis which is essentially p53 and mitochondria-dependent but with some involvement of caspase-2 and p73. Conversely, in mutant p53 melanoma cells overall levels of CPT-induced apoptosis are significantly lower, with p73 and caspase-2 signaling playing important roles. In addition, in these cells the expression of micro RNAs family 34 (miR-34) were low compared to wild-type p53 cells. The ectopic expression of wild type p53 than restored apoptotic response of cells to CPT despite the fact that the expression of miR-34 and miR-155 were not influenced. These results suggest that CPT induces multivariate cellular stress responses including activation of DNA-damage response-p53 pathway as well as p53-independent signaling and their mutual crosstalk play the decisive role in the efficient triggering of apoptosis in melanoma cells.