Broad targeting of resistance to apoptosis in cancer

Overcoming resistance to mitochondrial apoptosis by BZML-induced mitotic catastrophe is enhanced by inhibition of autophagy in A549/Taxol cells

OBJECTIVES

Our previous in vitro study showed that 5-(3, 4, 5-trimethoxybenzoyl)-4-methyl-2-(p-tolyl) imidazol (BZML) is a novel colchicine binding site inhibitor with potent anti-cancer activity against apoptosis resistance in A549/Taxol cells through mitotic catastrophe (MC). However, the mechanisms underlying apoptosis resistance in A549/Taxol cells remain unknown. To clarify these mechanisms, in the present study, we investigated the molecular mechanisms of apoptosis and autophagy, which are closely associated with MC in BZML-treated A549 and A549/Taxol cells.

METHODS

Xenograft NSCLC models induced by A549 and A549/Taxol cells were used to evaluate the efficacy of BZML in vivo. The activation of the mitochondrial apoptotic pathway was assessed using JC-1 staining, Annexin V-FITC/PI double-staining, a caspase-9 fluorescence metric assay kit and western blot. The different functional forms of autophagy were distinguished by determining the impact of autophagy inhibition on drug sensitivity.

RESULTS

Our data showed that BZML also exhibited desirable anti-cancer activity against drug-resistant NSCLC in vivo. Moreover, BZML caused ROS generation and MMP loss followed by the release of cytochrome c from mitochondria to cytosol in both A549 and A549/Taxol cells. However, the ROS-mediated apoptotic pathway involving the mitochondria that is induced by BZML was only fully activated in A549 cells but not in A549/Taxol cells. Importantly, we found that autophagy acted as a non-protective type of autophagy during BZML-induced apoptosis in A549 cells, whereas it acted as a type of cytoprotective autophagy against BZML-induced MC in A549/Taxol cells.

CONCLUSIONS

Our data suggest that the anti-apoptosis property of A549/Taxol cells originates from a defect in activation of the mitochondrial apoptotic pathway, and autophagy inhibitors can potentiate BZML-induced MC to overcome resistance to mitochondrial apoptosis.

A bibenzyl from Dendrobium ellipsophyllum induces apoptosis in human lung cancer cells

Failure of current chemotherapeutic drugs leads to the recurrence of tumor pathology and mortality in lung cancer patients. This study aimed to evaluate the anticancer activity and related mechanisms of 4,5,4'-trihydroxy-3,3'-dimethoxybibenzyl (TDB), a bibenzyl extracted from Dendrobium ellipsophyllum Tang and Wang, in human lung cancer cells. Cytotoxicity of TDB (0-300 µM) in different types of human lung cancer cells (H460, H292 and H23) and human dermal papilla cells (DPCs) was evaluated via MTT viability assay. Selective anticancer activity of TDB against human lung cancer cells was demonstrated with a high IC₅₀ (approximately > 300 µM) in DPCs, while IC₅₀ in human lung cancer H460, H292 and H23 cells was approximately 100 ± 5.18, 100 ± 8.73 and 188.89 ± 8.30 µM, respectively. After treatment with 50 µM of TDB for 24 h, flow cytometry analysis revealed the significant increase of early and late apoptosis with absence of necrosis cell death in human lung cancer cells. The up-regulation of p53, a tumor-suppressor protein, was elucidated in human lung cancer cells treated with 10-50 µM of TDB. Alteration to down-stream signaling of p53 including activation of pro-apoptosis protein (Bcl-2-associated X protein; Bax), reduction of anti-apoptosis (B cell lymphoma 2; Bcl-2 and myeloid cell leukemia 1; Mcl-1) and suppression on protein kinase B (Akt) survival pathway were notified in TDB-treated lung cancer cells. The information obtained from this study strengthens the potential development of TDB as an anticancer compound with a favorable human safety profile and high efficacy.

Necroptosis in tumorigenesis, activation of anti-tumor immunity, and cancer therapy

While the mechanisms underlying apoptosis and autophagy have been well characterized over recent decades, another regulated cell death event, necroptosis, remains poorly understood. Elucidating the signaling networks involved in the regulation of necroptosis may allow this form of regulated cell death to be exploited for diagnosis and treatment of cancer, and will contribute to the understanding of the complex tumor microenvironment. In this review, we have summarized the mechanisms and regulation of necroptosis, the converging and diverging features of necroptosis in tumorigenesis, activation of anti-tumor immunity, and cancer therapy, as well as attempts to exploit this newly gained knowledge to provide therapeutics for cancer.

Identification of mTOR as a primary resistance factor of the IAP antagonist AT406 in hepatocellular carcinoma cells

Dysregulation of inhibitor of apoptosis (IAP) proteins (IAPs) in hepatocellular carcinoma (HCC) is often associated with poor prognosis. Here we showed that AT406, an IAP antagonist, was cytotoxic and pro-apoptotic to both established (HepG2, SMMC-7721 lines) and primary HCC cells. Activation of mTOR could be a key resistance factor of AT406 in HCC cells. mTOR inhibition (by OSI-027), kinase-dead mutation or knockdown remarkably enhanced AT406-induced lethality in HCC cells. Reversely, forced-activation of mTOR by adding SC79 or exogenous expressing a constitutively active S6K1 (T389E) attenuated AT406-induced cytotoxicity against HCC cells. We showed that AT406 induced degradation of IAPs (cIAP-1 and XIAP), but didn't affect another anti-apoptosis protein Mcl-1. Co-treatment of OSI-027 caused simultaneous Mcl-1 downregulation to overcome AT406's resistance. Significantly, shRNA knockdown of Mcl-1 remarkably facilitated AT406-induced apoptosis in HCC cells. In vivo, AT406 oral administration suppressed HepG2 tumor growth in nude mice. Its activity was potentiated with co-administration of OSI-027. We conclude that mTOR could be a key resistance factor of AT406 in HCC cells.

Reduced expression of FILIP1L, a novel WNT pathway inhibitor, is associated with poor survival, progression and chemoresistance in ovarian cancer

Filamin A interacting protein 1-like (FILIP1L) is an inhibitor of the canonical WNT pathway. WNT/β-catenin signaling and its downstream pathway, epithelial-to-mesenchymal transition (EMT), play a key role in ovarian cancer metastasis and chemoresistance. To study the clinical implications of FILIP1L in regulating the WNT/β-catenin pathway, the expression of FILIP1L, β-catenin, SNAIL and SLUG was analyzed by immunohistochemistry on tissue microarrays of 369 ovarian samples ranging from normal to metastatic. In addition, the results were validated in mouse model and in vitro cell culture. In the present study, we demonstrated that FILIP1L expression was inversely correlated with poor prognosis, stage and chemoresistance in ovarian cancer. Notably, low FILIP1L expression was independent negative prognostic factor with respect to overall and disease-free survival. FILIP1L inhibited peritoneal metastases in orthotopic mouse model. FILIP1L knockdown induced chemoresistance in ovarian cancer cells and this phenotype was rescued by simultaneous knockdown of FILIP1L and SLUG, an EMT activator. We also demonstrated that FILIP1L regulates β-catenin degradation. FILIP1L co-localizes with phospho-β-catenin and increases phospho-β-catenin at the centrosomes, destined for proteosomal degradation. Finally, we showed that FILIP1L regulates EMT. Overall, these findings suggest that FILIP1L promotes β-catenin degradation and suppresses EMT, thereby inhibiting metastases and chemoresistance. Our study provides the first clinical relevance of FILIP1L in human cancer, and suggests that FILIP1L may be a novel prognostic marker for chemotherapy in ovarian cancer patients. Further, the modulation of FILIP1L expression may have the potential to be a target for cancer therapy.

Paraptosis-Inducing Nanomedicine Overcomes Cancer Drug Resistance for a Potent Cancer Therapy

Most chemotherapeutic drugs and their nanomedicine formulations exert anticancer activity by inducing cancer cell apoptosis. However, cancer cells inherently have and acquire many antiapoptosis mechanisms, causing cancer drug resistance and poor prognoses in patients. Herein, a potent paraptosis-inducing nanomedicine is reported that causes quick nonapoptotic death of cancer cells, overcoming apoptosis-based resistance and effectively inhibiting drug-resistant tumor growth. The nanomedicine is composed of micelles made from an amphiphilic 8-hydroxyquinoline (HQ)-conjugate block copolymer with polyethylene glycol. Cu²⁺ can catalyze the hydrolysis of the HQ conjugation linker and liberate HQ, and these molecules can form the complex Cu(HQ)₂ , a strong proteasome inhibitor effective at inducing cell paraptosis. In vivo, the Cu²⁺ -responsive HQ-releasing micelles respond to elevated tumor Cu²⁺ levels or externally administered Cu²⁺ and effectively inhibit the growth of human breast adenocarcinoma doxorubicin-resistant (MCF-7/ADR) tumors. Compared with other nanomedicines that overcome drug resistance via delivering several agents or even siRNA, this paraptosis-inducing nanomedicine provides a simple but potent approach to overcoming cancer drug resistance.

Non-apoptotic cell death in malignant tumor cells and natural compounds

Traditional cancer therapy is mainly targeting on enhancing cell apoptosis, however, it is well established that many cancer cells are chemo-resistant and defective in apoptosis induction. Therefore, it may have important therapeutic implications to exploit some novel natural compounds based on non-apoptotic programmed cell death. Currently, accumulating evidence shows that the compounds from nature source can induce non-apoptotic programmed cell death in cancer cells, and therefore these natural compounds have gained a great promise for the future anticancer therapeutics. In this review, we will concentrate our efforts on the latest developments regarding major forms of non-apoptotic programmed cell death--autophagic cell death, necroptosis, ferroptosis, pyroptosis, glutamoptosis and exosome-associated cell death. Our increased understanding of the role of natural compounds in regulating non-apoptotic programmed cell death will hopefully provide prospective strategies for cancer therapy.

Curcumin and Melanoma: From Chemistry to Medicine

Melanoma is the most deadly form of skin cancer, with about 48,000 deaths each year worldwide. Growing evidence suggests that individual nutrients or dietary patterns might have important roles in the prevention of melanoma. Considering that melanoma is a potentially life-threatening cancer, novel protective and adjuvant treatments are needed to improve its prognosis. Curcumin is a bioactive substance extracted from rhizome of Curcuma longa L. Its global market is expected to grow in the next few years, especially in the pharmaceutical industry, due to its numerous physiological and pharmacological properties. For this review, we collected the available data on the protective and therapeutic role of curcumin against melanoma. We also discuss the chemistry, dietary sources, bioavailability, and metabolism of curcumin, and the mechanisms of action of its potential anticancer effects at the molecular level. Current challenges and future directions for research are also critically discussed.

Molecular mechanisms and clinical implications of miRNAs in drug resistance of esophageal cancer

With the increasing incidence of esophageal cancer, drug resistance is becoming a major obstacle to successful cancer therapy since chemotherapy is regarded as a curative approach to inhibit cancer cell proliferation. Despite the great progress in anticancer treatment achieved during the last decades, the mechanisms of multidrug resistance have not been completely elucidated. Recently, accumulating studies and pre-clinical reports highlighted the role of miRNAs in the drug resistance of esophageal cancer. Areas covered: In this review, we mainly summarized the current advances of miRNAs in esophageal cancer and the mechanisms underlying drug resistance. We also reviewed the potential role of miRNAs as biomarkers for predicting drug response and prognosis. Finally, we envisaged the future orientation and challenges in translating the existing knowledge of drug resistance related miRNAs into clinical applications. Expert commentary: Based on the current knowledge of certain miRNAs, we believe that miRNAs would be helpful to overcome the drug resistance and provide personalized treatment for patients with esophageal cancer. The aims of this study were to provide a comprehensive summary on the emerging role of miRNAs in the drug resistance of esophageal cancer and attract broad attention of more researchers on this field.

Clonality in context: hematopoietic clones in their marrow environment

Clonal hematopoiesis occurs normally, especially with aging, and in the setting of disease, not only in myeloid cancers but in bone marrow failure as well. In cancer, malignant clones are characterized by recurrent somatic mutations in specific sets of genes, but the direct relationship of such mutations to leukemogenesis, when they occur in cells of an apparently healthy older individual or after recovery from immune aplastic anemia, is uncertain. Here we emphasize a view of clonal evolution that stresses natural selection over deterministic ontogeny, and we stress the selective role of the environment of the marrow and organism. Clonal hematopoieses after chemotherapy, in marrow failure, and with aging serve as models. We caution against the overinterpretation of clinical results of genomic testing in the absence of a better understanding of clonal selection and evolution.

Recent Advances in Comprehending the Signaling Pathways Involved in the Progression of Breast Cancer

This review describes recent advances in the comprehension of signaling pathways involved in breast cancer progression. Calcium sensing receptor (CaSR), caveolae signaling, signaling referred to hypoxia-inducing factors and disturbances in the apoptotic machinery are related to more general biological mechanisms and are considered first. The others refer to signaling pathways of more specific biological mechanisms, namely the heparin/heparin-sulfate interactome, over-expression of miRNA-378a-5p, restriction of luminal and basal epithelial cells, fatty-acid synthesis, molecular pathways related to epithelial to mesenchimal transition (EMT), HER-2/neu gene amplification and protein expression, and the expression of other members of the epithelial growth factor receptor family. This progress in basic research is fundamental to foster the ongoing efforts that use the new genotyping technologies, and aim at defining new prognostic and predictive biomarkers for a better personalized management of breast cancer disease.

Downregulation of Survivin Gene Expression Affects Ionizing Radiation Resistance of Human T98 Glioma Cells

Survivin is a tumor-associated gene, which has been detected in a wide variety of human tumors. Previous research has shown that Survivin can affect hepatoma carcinoma cell radiosensitivity. However, little is known about the role of Survivin in ionizing radiation resistance in glioma cells. In this study, we aimed to identify the effects of Survivin on ionizing radiation resistance in glioma cell line T98. Our results showed that downregulation of Survivin gene expression and ionizing irradiation could both inhibit T98 cell proliferation by assays in vitro including CCK-8 and immunohistochemistry. The inhibitory effect of downregulation of Survivin combined with irradiation was the most significant compared with other groups. Results of Western blotting and flow cytometric analysis also showed that downregulation of Survivin combined with the irradiation group achieved the highest apoptosis rate. Experimental results in vivo by intracranial implanting into nude mice were consistent with those in vitro. These findings indicated that ionizing radiation resistance of human T98 glioma cells can be inhibited effectively after Survivin gene silencing.

ProSelection: A Novel Algorithm to Select Proper Protein Structure Subsets for in Silico Target Identification and Drug Discovery Research

Molecular docking is widely applied to computer-aided drug design and has become relatively mature in the recent decades. Application of docking in modeling varies from single lead compound optimization to large-scale virtual screening. The performance of molecular docking is highly dependent on the protein structures selected. It is especially challenging for large-scale target prediction research when multiple structures are available for a single target. Therefore, we have established ProSelection, a docking preferred-protein selection algorithm, in order to generate the proper structure subset(s). By the ProSelection algorithm, protein structures of "weak selectors" are filtered out whereas structures of "strong selectors" are kept. Specifically, the structure which has a good statistical performance of distinguishing active ligands from inactive ligands is defined as a strong selector. In this study, 249 protein structures of 14 autophagy-related targets are investigated. Surflex-dock was used as the docking engine to distinguish active and inactive compounds against these protein structures. Both t test and Mann-Whitney U test were used to distinguish the strong from the weak selectors based on the normality of the docking score distribution. The suggested docking score threshold for active ligands (SDA) was generated for each strong selector structure according to the receiver operating characteristic (ROC) curve. The performance of ProSelection was further validated by predicting the potential off-targets of 43 U.S. Federal Drug Administration approved small molecule antineoplastic drugs. Overall, ProSelection will accelerate the computational work in protein structure selection and could be a useful tool for molecular docking, target prediction, and protein-chemical database establishment research.

YAP transcriptionally regulates COX-2 expression and GCCSysm-4 (G-4), a dual YAP/COX-2 inhibitor, overcomes drug resistance in colorectal cancer

BACKGROUND

Chemotherapy resistance remains a major challenge in cancer treatment. COX-2 (cyclooxygenase 2) is involved in drug resistance and poor prognosis of many neoplastic diseases or cancers. However, investigations identifying new modulators of COX-2 pathway and searching for new chemicals targeting these valid resistant biomarkers are still greatly needed.

METHODS

HCT15, HCT-116, HT-29, COLO205, FHC, IMCE, SW480 cell lines were used to detect the expression of YAP and COX-2. Site-directed mutagenesis, luciferase reporter analysis and ChIP assay were used to test whether YAP activated COX-2 transcription through interaction with TEAD binding sites in the promoter of COX-2. Cell line models exhibiting overexpression or knockdown of some genes were generated using transfection agents. Coimmunoprecipitation was used to detect protein mutual interaction. mRNA and protein levels were measured by qRT-PCR and western blot respectively.

RESULTS

Here, we reported that both YAP and COX-2 were overexpressed in colorectal cancer cells. YAP increased COX-2 expression at the level of transcription requiring intact TEAD binding sites in the COX-2 promoter. YAP conferred drug resistance through COX-2 and its related effectors such as MCL, MDR, Survivin. GCCSysm-4 (G-4), a YAP and COX-2 inhibitor, effectively inhibited both YAP and COX-2 activation, induced apoptosis and decreased viability in Taxol-resistant cells. Inhibition of YAP and COX-2 acted synergistically and more efficiently reduced the resistance of CRC cells than either of them alone.

CONCLUSIONS

Our data provide new mechanisms that YAP is a new upstream regulator of COX-2 pathway and plays an important role in conferring resistance in CRC cells. G-4, targeting YAP-COX-2, may be a novel valuable strategy to combat resistance in CRC.

t-BuOOH induces ferroptosis in human and murine cell lines

Reactive oxygen species (ROS)-induced apoptosis has been extensively studied. Increasing evidence suggests that ROS, for instance, induced by hydrogen peroxide (H₂O₂), might also trigger regulated necrotic cell death pathways. Almost nothing is known about the cell death pathways triggered by tertiary-butyl hydroperoxide (t-BuOOH), a widely used inducer of oxidative stress. The lipid peroxidation products induced by t-BuOOH are involved in the pathophysiology of many diseases, such as cancer, cardiovascular diseases, or diabetes. In this study, we exposed murine fibroblasts (NIH3T3) or human keratinocytes (HaCaT) to t-BuOOH (50 or 200 μM, respectively) which induced a rapid necrotic cell death. Well-established regulators of cell death, i.e., p53, poly(ADP)ribose polymerase-1 (PARP-1), the stress kinases p38 and c-Jun N-terminal-kinases 1/2 (JNK1/2), or receptor-interacting serine/threonine protein kinase 1 (RIPK1) and 3 (RIPK3), were not required for t-BuOOH-mediated cell death. Using the selective inhibitors ferrostatin-1 (1 μM) and liproxstatin-1 (1 μM), we identified ferroptosis, a recently discovered cell death mechanism dependent on iron and lipid peroxidation, as the main cell death pathway. Accordingly, t-BuOOH exposure resulted in a ferrostatin-1- and liproxstatin-1-sensitive increase in lipid peroxidation and cytosolic ROS. Ferroptosis was executed independently from other t-BuOOH-mediated cellular damages, i.e., loss of mitochondrial membrane potential, DNA double-strand breaks, or replication block. H₂O₂ did not cause ferroptosis at equitoxic concentrations (300 μM) and induced a (1) lower and (2) ferrostatin-1- or liproxstatin-1-insensitive increase in lipid peroxidation. We identify that t-BuOOH and H₂O₂ produce a different pattern of lipid peroxidation, thereby leading to different cell death pathways and present t-BuOOH as a novel inducer of ferroptosis.

Anoikis and EMT: Lethal "Liaisons" during Cancer Progression

Anoikis is a unique mode of apoptotic cell death that occurs consequentially to insufficient cell-matrix interactions. Resistance to anoikis is a critical contributor to tumor invasion and metastasis. The phenomenon is regulated by integrins, which upon engagement with components of the extracellular matrix (ECM) form adhesion complexes and the actin cytoskeleton drives the formation of cell protrusions used to adhere to ECM, directing cell migration. The epithelial-mesenchymal transition (EMT) confers stem cell properties and leads to acquisition of a migratory and invasive phenotype by causing adherens junction breakdown and circumventing anoikis in the tumor microenvironment. The investigation of drug discovery platforms for apoptosis-driven therapeutics identified several novel agents with antitumor action via reversing resistance to anoikis, inhibiting survival pathways and impacting the EMT landscape in human cancer. In this review, we discuss current evidence on the contribution of the anoikis phenomenon functionally linked to EMT to cancer metastasis and the therapeutic value of antitumor drugs that selectively reverse anoikis resistance and/or EMT to impair tumor progression toward the development/optimization of apoptosis-driven therapeutic targeting of metastatic disease.

Amarogentin Induces Apoptosis of Liver Cancer Cells via Upregulation of p53 and Downregulation of Human Telomerase Reverse Transcriptase in Mice

BACKGROUND AND OBJECTIVE

Amarogentin has been reported to have a preventive effect on liver cancer via inducing cancer cell apoptosis. We attempted to elucidate the roles of p53-associated apoptosis pathways in the chemopreventive mechanism of amarogentin. The findings of this study will facilitate the development of a novel supplementary strategy for the treatment of liver cancer.

MATERIALS AND METHODS

The purity of amarogentin was assessed by high-performance liquid chromatography. The inhibitory ratios of the liver cell lines were determined using a Cell Counting Kit-8 following treatment with a gradient concentration of amarogentin. Cell apoptosis was detected by flow cytometry using annexin V-fluorescein isothiocyanate/propidium iodide kits. The gene and protein expression of p53-associated molecules, such as Akt, human telomerase reverse transcriptase, RelA, and p38, was detected by real-time quantitative polymerase chain reaction, Western blotting, and immunohistochemical staining in liver cancer cells and mouse tumor tissues after treatment with amarogentin.

RESULTS

The inhibitory effect of amarogentin on cell proliferation was more obvious in liver cancer cells, and amarogentin was more likely to induce the apoptosis of liver cancer cells than that of normal liver cells. The gene and protein expression levels of Akt, RelA, and human telomerase reverse transcriptase were markedly higher in the control group than in the preventive group and treatment groups. Only the expression of human telomerase reverse transcriptase was downregulated, accompanied by the upregulation of p53.

CONCLUSION

The results of our study suggest that amarogentin promotes apoptosis of liver cancer cells by the upregulation of p53 and downregulation of human telomerase reverse transcriptase and prevents the malignant transformation of these cells.

miR-338-3p confers 5-fluorouracil resistance in p53 mutant colon cancer cells by targeting the mammalian target of rapamycin

Evidence demonstrate that p53 mutations and microRNAs (miRs) are important components of 5-FU resistance in colorectal cancer (CRC). miR-338-3p has been reported associated with cancer prognosis. However whether or not it influences chemotherapy sensitivity and the underlying mechanisms have not been elucidated. Here, three types of human colon cancer cell lines, HT29 (mutant p53), HCT116 (wild-type p53), and HCT116 p53^-/- (deficient p53), were treated with 5-FU. We showed that expression of miR-338-3p was correlated with apoptosis and 5-FU resistance in colon cancer cells. Ectopic expression of miR-338-3p conferred resistance to 5-FU in HCT116 cells. Further experiments indicated that miR-338-3p mediated 5-FU resistance through down-regulation of mTOR expression. Moreover, inhibition of miR-338-3p in HT29 and HCT116 p53^-/- cells increased their sensitivity to 5-FU treatment. Furthermore, we detected autophagy changes in our experiment because mTOR was known prominently regulating autophagy and the competition between autophagy and apoptosis in response to 5-FU was a mechanism influencing 5-FU sensitivity. Our results reveal a critical and novel role of miR-338-3p in the correlation of 5-FU resistance with p53 status. Moreover, the miR-338-3p inhibitor has the potential to overcome 5-FU resistance in p53 mutant colon cancer cells.

Molecular mechanisms for tumour resistance to chemotherapy

Chemotherapy is one of the prevailing methods used to treat malignant tumours, but the outcome and prognosis of tumour patients are not optimistic. Cancer cells gradually generate resistance to almost all chemotherapeutic drugs via a variety of distinct mechanisms and pathways. Chemotherapeutic resistance, either intrinsic or acquired, is caused and sustained by reduced drug accumulation and increased drug export, alterations in drug targets and signalling transduction molecules, increased repair of drug-induced DNA damage, and evasion of apoptosis. In order to better understand the mechanisms of chemoresistance, this review highlights our current knowledge of the role of altered drug metabolism and transport and deregulation of apoptosis and autophagy in the development of tumour chemoresistance. Reduced intracellular activation of prodrugs (e.g. thiotepa and tegafur) or enhanced drug inactivation by Phase I and II enzymes contributes to the development of chemoresistance. Both primary and acquired resistance can be caused by alterations in the transport of anticancer drugs which is mediated by a variety of drug transporters such as P-glycoprotein (P-gp), multidrug resistance associated proteins, and breast cancer resistance protein. Presently there is a line of evidence indicating that deregulation of programmed cell death including apoptosis and autophagy is also an important mechanism for tumour resistance to anticancer drugs. Reversal of chemoresistance is likely via pharmacological and biological approaches. Further studies are warranted to grasp the full picture of how each type of cancer cells develop resistance to anticancer drugs and to identify novel strategies to overcome it.

In vitro polyphenol effects on apoptosis: An update of literature data

Polyphenols are secondary plant metabolites which have been studied extensively for their health-promoting properties, and which could also exert pharmacological activities ranging from anti-inflammatory effects, to cytotoxic activity against cancer cells. The main mechanism for programmed cell death is represented by apoptosis, and its dysregulation is involved in the etiopathology of cancer. As such, substances able to induce apoptosis in cancer cells could be used as new anticancer agents. The aim of this paper is to review literature data on the apoptotic effects of polyphenols and the molecular mechanisms through which they induce these effects in cancer cells. In addition, a brief summary of the new delivery forms used to increase the bioavailability, and clinical impact of polyphenols is provided. The studies reported show that many polyphenol rich plant extracts, originating from food and herbal medicine, as well as isolated polyphenols administered individually or in combination, can regulate cell apoptosis primarily through intrinsic and extrinsic mechanisms of action in in vitro conditions. Due to these promising results, the use of polyphenols in the treatment of cancer should therefore be deeply investigated. In particular, because of the low number of clinical trials, further studies are required to evaluate the anticancer activity of polyphenols in in vivo conditions.

NOX2-Mediated TFEB Activation and Vacuolization Regulate Lysosome-Associated Cell Death Induced by Gypenoside L, a Saponin Isolated from Gynostemma pentaphyllum

Downregulation of apoptotic signal pathway and activation of protective autophagy mainly contribute to the chemoresistance of tumor cells. Therefore, exploring efficient chemotherapeutic agents or isolating novel natural products that can trigger nonapoptotic and nonautophagic cell death such as lysosome-associated death is emergently required. We have recently extracted a saponin, gypenoside L (Gyp-L), from Gynostemma pentaphyllum and showed that Gyp-L was able to induce nonapoptotic cell death of esophageal cancer cells associated with lysosome swelling. However, contributions of vacuolization and lysosome to cell death remain unclear. Herein, we reveal a critical role for NADPH oxidase NOX2-mediated vacuolization and transcription factor EB (TFEB) activation in lysosome-associated cell death. We found that Gyp-L initially induced the abnormal enlarged and alkalized vacuoles, which were derived from lipid rafts dependent endocytosis. Besides, NOX2 was activated to promote vacuolization and mTORC1-independent TFEB-mediated lysosome biogenesis. Finally, raising lysosome pH could enhance Gyp-L induced cell death. These findings suggest a protective role of NOX2-TFEB-mediated lysosome biogenesis in cancer drug resistance and the tight interaction between lipid rafts and vacuolization. In addition, Gyp-L can be utilized as an alternative option to overcome drug-resistance though inducing lysosome associated cell death.

A Systematic Review of the Immune-Regulating and Anticancer Activities of Pseudolaric Acid B

Cortex pseudolaricis, the root bark of Pseudolarix kaempferi Gord, has been used to treat tinea and other skin diseases for the antimicrobial activities in Traditional Chinese Medicine (TCM). Pseudolaric acid B (PAB) has been identified as the major component responsible for the action of C. pseudolaricis. Recently, PAB has been demonstrated to be used as novel treatments for cancer, immune disorders, inflammatory diseases, and immunosuppression. However, the mechanisms through which PAB exerts its properties are not understood well, and little attention in the literature has been given to review its pharmacological activities before. In this review, we performed a systematic summary of the literature with respect to the anticancer, immunosuppressive and anti-inflammatory properties of PAB and its derivatives. Currently available data suggest that PAB is a promising immunosuppressive and anti-inflammatory agent candidate and should be explored further in cancer treatment and prevention.

Novel indolyl-chalcone derivatives inhibit A549 lung cancer cell growth through activating Nrf-2/HO-1 and inducing apoptosis in vitro and in vivo

Increasing evidence indicates that Nrf-2, named the nuclear factor-erythroid 2-related factor, may perform anticancer function. In this study, a series of novel substituted phenyl- (3-methyl-1H-indol-2-yl)-prop-2-en-1-one (indolyl-chalcone) derivatives were synthesized and their effects on Nrf-2 activity were observed. We found that compounds 3a-3d and 6c elevated Nrf-2 activity. Then we evaluated their anticancer activities in vitro and in vivo by utilizing human lung cancer cell line A549. The in vitro results showed that among the compounds, 3d performed effectively anti-growth activity by inducing A549 lung cancer cell apoptosis and activating Nrf-2/HO-1 (heme oxygenase-1) pathway. In vivo, we proved that compound 3d inhibited the tumor growth effectively through inducing cell apoptosis without affecting CAM normal angiogenesis. These data suggest that our discovery of a novel Nrf-2 activator compound 3d would provide a new point of human lung cancer treatment.

Assessing the anticancer effects associated with food products and/or nutraceuticals using in vitro and in vivo preclinical development-related pharmacological tests

This review is part of a special issue entitled "Role of dietary pattern, foods, nutrients and nutraceuticals in supporting cancer prevention and treatment" and describes a pharmacological strategy to determine the potential contribution of food-related components as anticancer agents against established cancer. Therefore, this review does not relate to chemoprevention, which is analysed in several other reviews in the current special issue, but rather focuses on the following: i) the biological events that currently represent barriers against the treatment of certain types of cancers, primarily metastatic cancers; ii) the in vitro and in vivo pharmacological pre-clinical tests that can be used to analyse the potential anticancer effects of food-related components; and iii) several examples of food-related components with anticancer effects. This review does not represent a catalogue-based listing of food-related components with more or less anticancer activity. By contrast, this review proposes an original pharmacological strategy that researchers can use to analyse the potential anticancer activity of any food-related component-e.g., by considering the crucial characteristics of cancer biological aggressiveness. This review also highlights that cancer patients undergoing chemotherapy should restrict the use of "food complements" without supervision by a medical nutritionist. By contrast, an equilibrated diet that includes the food-related components listed herein would be beneficial for cancer patients who are not undergoing chemotherapy.

Marine Terpenoid Diacylguanidines: Structure, Synthesis, and Biological Evaluation of Naturally Occurring Actinofide and Synthetic Analogues

A new diacylguanidine, actinofide (1), has been isolated from the marine mollusk Actinocyclus papillatus. The structure, exhibiting a guanidine moiety acylated by two terpenoid acid units, has been established by spectroscopic methods and secured by synthesis. Following this, a series of structural analogues have been synthesized using the same procedure. All of the compounds have been evaluated in vitro for the growth inhibitory activity against a variety of cancer cell lines.

Antioxidant polyphenols in cancer treatment: Friend, foe or foil?

Cancer prevention can be probably obtained with easier, faster and less financial strains by pursuing educational programs aimed to induce changes in lifestyle, starting from dietary habits. In the past decades, observational and case-control studies tried to establish a functional relationship between cancer mortality and morbidity and diet. The field becomes even more intricate when scientists investigated which dietary components are responsible for the putative, protective effects of fruits and vegetables against cancer. A relevant part of the literature focused on the positive role of "antioxidant" compounds in foods, including polyphenols. The present review critically evaluate clinical and pre-clinical studies based on polyphenol administration, which contributed to support the concept, deeply rooted in the general population, that antioxidant polyphenols can fight cancer. The controversial and contradictory issues related to the pros and cons on the use of polyphenols against cancer reflect the confounding assumption that cancer treatment and cancer prevention may overlap. We conclude that a clear cut must be done between these two concepts and that the experimental approaches to investigate one or the other should be significantly different, starting from adequate and specifically selected cellular models.

Assessing the Racial and Ethnic Disparities in Breast Cancer Mortality in the United States

Breast cancer is the second leading cause of cancer related deaths among women aged 40-55 in the United States and currently affects more than one in ten women worldwide. It is also one of the most diagnosed cancers in women both in wealthy and poor countries. Fortunately, the mortality rate from breast cancer has decreased in recent years due to increased emphasis on early detection and more effective treatments in White population. Although the mortality rates have declined in some ethnic populations, the overall cancer incidence among African American and Hispanic populations has continued to grow. The goal of the present review article was to highlight similarities and differences in breast cancer morbidity and mortality rates primarily among African American women compared to White women in the United States. To reach our goal, we conducted a search of articles in journals with a primary focus on minority health, and authors who had published articles on racial/ethnic disparity related to breast cancer patients. A systematic search of original research was conducted using MEDLINE, PUBMED and Google Scholar databases. We found that racial/ethnic disparities in breast cancer may be attributed to a large number of clinical and non-clinical risk factors including lack of medical coverage, barriers to early detection and screening, more advanced stage of disease at diagnosis among minorities, and unequal access to improvements in cancer treatment. Many African American women have frequent unknown or unstaged breast cancers than White women. These risk factors may explain the differences in breast cancer treatment and survival rate between African American women and White women. New strategies and approaches are needed to promote breast cancer prevention, improve survival rate, reduce breast cancer mortality, and ultimately improve the health outcomes of racial/ethnic minorities.

Cyclooxygenase-2 Induction by Amino Acid Deprivation Requires p38 Mitogen-Activated Protein Kinase in Human Glioma Cells

Glioblastomas (GBMs) are malignant brain tumors that can outstrip nutrient supplies due to rapid growth. Cyclooxygenase-2 (COX-2) has been linked to GBMs and may contribute to their aggressive phenotypes. Amino acid starvation results in COX-2 mRNA and protein induction in multiple human glioma cell lines in a process requiring p38 mitogen-activated protein kinase (p38-MAPK) and the Sp1 transcription factor. Increased vascular endothelial growth factor expression results from starvation-dependent COX-2 induction. These data suggest that COX-2 induction with amino acid deprivation may be a part of the adaptation of glioma cells to these conditions, and potentially alter cellular response to anti-neoplastic therapy.

Morusin induces apoptosis by regulating expression of Bax and Survivin in human breast cancer cells

Morusin which has been isolated from the root bark of Morus alba L. (Moraceae) has previously demonstrated anticancer activity in various types of cancer cells such as hepatocellular carcinoma, glioma and prostate cancer. However, the effect of morusin on breast cancer cells remains unclear. In the present study, the potential of morusin as an anti-cancer agent in breast cancer was investigated. The results of the present study revealed that the treatment of morusin induced cell death in various human breast cancer cell lines, but exhibited little effect on normal human breast epithelial cells. In Annexin V-propidium iodide double staining assays, morusin significantly increased apoptosis in a dose-dependent manner in human breast cancer cells. The apoptosis marker proteins cleaved caspase 3 and 9 were consistently upregulated following treatment of cells with morusin in a time- and dose-dependent manner. Furthermore, morusin was demonstrated to modulate the expression of the anti-apoptotic protein Survivin and pro-apoptotic protein B-cell lymphoma 2-associated-x protein (Bax) in human breast cancer cells. These results indicate that morusin induces apoptosis by suppressing Survivin and inducing Bax proteins, suggesting that morusin is a potentially effective therapeutic agent for the treatment of patients with breast cancer.

Antiproliferative effects of ruthenium-based nucleolipidic nanoaggregates in human models of breast cancer in vitro: insights into their mode of action

Looking for new metal-based anticancer treatments, in recent years many ruthenium complexes have been proposed as effective and safe potential drugs. In this context we have recently developed a novel approach for the in vivo delivery of Ru(III) complexes, preparing stable ruthenium-based nucleolipidic nanoaggregates endowed with significant antiproliferative activity. Herein we describe the cellular response to our ruthenium-containing formulations in selected models of human breast cancer. By in vitro bioscreens in the context of preclinical studies, we have focused on their ability to inhibit breast cancer cell proliferation by the activation of the intrinsic apoptotic pathway, possibly via mitochondrial perturbations involving Bcl-2 family members and predisposing to programmed cell death. In addition, the most efficient ruthenium-containing cationic nanoaggregates we have hitherto developed are able to elicit both extrinsic and intrinsic apoptosis, as well as autophagy. To limit chemoresistance and counteract uncontrolled proliferation, multiple cell death pathways activation by metal-based chemotherapeutics is a challenging, yet very promising strategy for targeted therapy development in aggressive cancer diseases, such as triple-negative breast cancer with limited treatment options. These outcomes provide valuable, original knowledge on ruthenium-based candidate drugs and new insights for future optimized cancer treatment protocols.

Melatonin and IL-25 modulate apoptosis and angiogenesis mediators in metastatic (CF-41) and non-metastatic (CMT-U229) canine mammary tumour cells

BACKGROUND

Melatonin has oncostatic actions and IL-25 is active in inflammatory processes that induce apoptosis in tumor cells AIM: The aim of this study was to evaluate melatonin and IL-25 in metastatic (CF-41) and non-metastatic (CMT-U229) canine mammary tumor cells cultured as monolayers and tridimensional structures.

MATERIALS AND METHODS

The cells were treated with melatonin, IL-25 and IL-17B silencing gene and performed cell viability, gene and protein expression of caspase-3 and VEGFA (Vascular endothelial growth factor A) and an apoptosis membrane protein array.

RESULTS

Treatment with 1 mM of melatonin reduced cell viability of both tumor cell lines, all treatments alone and combined significantly increased caspase-3 cleaved and proteins involved in the apoptotic pathway and reduced pro-angiogenic VEGFA, confirming the effectiveness of these potential promising treatments.

CONCLUSION

This is the first study evaluating the potential use of these strategies in CF-41 and CMT-U229 cell lines and together encourages subsequent in vitro and in vivo studies for further exploration of clinical applications.

Melatonin treatment induces apoptosis through regulating the nuclear factor-κB and mitogen-activated protein kinase signaling pathways in human gastric cancer SGC7901 cells

Melatonin, which is synthesized by the pineal gland and released into the blood, exhibits antitumor properties. However, the mechanisms underlying these effects, particularly in stomach cancer, remain unknown. In the present study, the effect of melatonin on the nuclear factor (NF)-κB signaling pathway and the mitogen-activated protein kinase signaling pathway, involving p38 and c-Jun-N-terminal kinase (JNK), were investigated in SGC7901 gastric cancer cells. In addition, the effect of melatonin on the survival, migration and apoptosis of these cells was investigated in vitro in order to evaluate the use of melatonin for the treatment of gastric cancer. The results of the present study revealed that melatonin decreased the viability and migration of SGC7901 cells. Furthermore, melatonin induced apoptosis. Melatonin was identified to elevate the expression levels of phosphorylated (p)-p38 and p-JNK protein, and decrease the expression level of nucleic p-p65. These results suggest that the protein levels of p65, p38 and JNK are associated with the survival of SGC7901 cells following treatment with melatonin. The optimal concentration of melatonin was demonstrated to be 2 mM, which significantly induced apoptosis following a 24 h treatment period. These findings suggest that conflicting growth signals in cells may inhibit the efficacy of melatonin in the treatment of gastric cancer. Therefore, adjunct therapy would be required to improve the efficacy of melatonin in the treatment of cancer.

Regulation of cytotoxicity and apoptosis-associated pathways contributes to the enhancement of efficacy of cisplatin by baicalein adjuvant in human A549 lung cancer cells

Scutellaria baicalensis (SB; Chinese name, huangqin) is widely used in Chinese medicine as a traditional adjuvant in the chemotherapy of lung and liver cancer. Baicalein is one of the bioactive flavonoid components isolated from the root of SB. The present study aimed to observe the effect of baicalein, in combination with platin-based systemic chemotherapy (cisplatin), on cytotoxicity and apoptosis of human A549 lung cancer cells. The cell cultures were treated with baicalein, cisplatin, or a combination of the two. Cell viability and cytotoxicity was assayed by XTT, and cell apoptosis was measured by flow cytometry. The apoptosis-associated proteins were detected by western blot analysis. The cytokines in the culture supernatant were detected by ELISA. The present study revealed that cisplatin and the baicalein-cisplatin combination inhibited viability and promoted cytotoxicity of A549 cells. Cisplatin, baicalein and baicalein-cisplatin combination treatments were effective in the promotion of apoptosis of A549 cells. Baicalein and baicalein-cisplatin combination treatments also inhibited B cell lymphoma-2 (Bcl-2) and increased Bcl-2-associated X protein (Bax) expression. Additionally, cisplatin, baicalein and the baicalein-cisplatin combination promoted caspase-3 expression. Furthermore, the baicalein-cisplatin combination suppressed the secretion of interleukin-6, and baicalein and the combination of baicalein cisplatin decreased the secretion of tumor necrosis factor-α of A549 cells. The present study concluded that baicalein combined with cisplatin induced cytotoxicity and apoptosis of A549 cells, and such activity may be associated with the regulation of Bcl-2, Bax and caspase-3, indicating a promising alternative method for lung cancer.

Complex refractive index of normal and malignant human colorectal tissue in the visible and near-infrared

A multi-wavelength prism coupling refractometer is utilized to measure the angular reflectance of freshly excised human intestinal tissue specimens. Based on reflectance data, the real and imaginary part of the refractive index is calculated via Fresnel analysis for three visible (blue, green, red) and two near-infrared (963 nm and 1551 nm) wavelengths. Averaged values of the complex refractive index and corresponding Cauchy dispersion fits are given for the mucosa, submucosa and serosa layers of the colorectal wall at the normal state. The refractive constants of tumorous and normal mucosa are then cross-compared for the indicative cases of one patient diagnosed with a benign polyp and three patients diagnosed with adenocarcinomas of different phenotype. Significant index contrast exists between the normal and diseased states, indicating the potential use of refractive index as a marker of colorectal dysplasia.

Natural Compounds As Modulators of Non-apoptotic Cell Death in Cancer Cells

Cell death is an innate capability of cells to be removed from microenvironment, if and when they are damaged by multiple stresses. Cell death is often regulated by multiple molecular pathways and mechanism, including apoptosis, autophagy, and necroptosis. The molecular network underlying these processes is often intertwined and one pathway can dynamically shift to another one acquiring certain protein components, in particular upon treatment with various drugs. The strategy to treat human cancer ultimately relies on the ability of anticancer therapeutics to induce tumor-specific cell death, while leaving normal adjacent cells undamaged. However, tumor cells often develop the resistance to the drug-induced cell death, thus representing a great challenge for the anticancer approaches. Numerous compounds originated from the natural sources and biopharmaceutical industries are applied today in clinics showing advantageous results. However, some exhibit serious toxic side effects. Thus, novel effective therapeutic approaches in treating cancers are continued to be developed. Natural compounds with anticancer activity have gained a great interest among researchers and clinicians alike since they have shown more favorable safety and efficacy then the synthetic marketed drugs. Numerous studies in vitro and in vivo have found that several natural compounds display promising anticancer potentials. This review underlines certain information regarding the role of natural compounds from plants, microorganisms and sea life forms, which are able to induce non-apoptotic cell death in tumor cells, namely autophagy and necroptosis.

Resveratrol reverses Doxorubicin resistance by inhibiting epithelial-mesenchymal transition (EMT) through modulating PTEN/Akt signaling pathway in gastric cancer

BACKGROUND

Gastric cancer is one of the major causes of cancer-related mortality worldwide. Most of patients presenting with inoperable gastric cancers rely on systemic chemotherapy for prolongation of survival. Doxorubicin (DOX) is one of the important agents against gastric cancer. Acquired DOX-resistance severely impedes the chemotherapeutic effect, invariably leading to poor prognosis. Resveratrol (RES) as a kind of phytoalexin has demonstrated anti-tumor functions in breast cancer and myeloid leukemia, but its function and mechanism are still unknown in gastric cancer treatment.

METHODS

CCK8 assay was used to detect the cytotoxicity of DOX and RES to gastric cancer cells. DOX-resistant subclone cell line (SGC7901/DOX) was derived from SGC7901 cells exposed to stepwise increasing concentrations of DOX treatment. We measured the migratory capabilities of SGC7901/DOX cells by Cell scratch test and Transwell assay. SGC7901/DOX cells were treated with DOX, RES, neither or both. Then we analyzed cell survival by CCK8 assay, colony formation by Colony-forming assay, cell apoptosis by Annexin-V-FITC and PI dual staining assay and cell migration by Cell scratch test and Transwell assay. Western blotting was conducted to detect the protein expressions of PTEN/Akt signaling pathway and EMT-related markers. Immunofluorescence was performed to confirm the EMT-related markers expressions. The xenograft model was used to assess the effect of DOX and RES in vivo. The key molecules associated with proliferation, apoptosis and EMT were evaluated by immunohistochemistry in tumor specimens.

RESULTS

SGC7901/DOX cells acquired drug resistance and enhancive migratory capability. RES enabled SGC7901/DOX cells to regain DOX sensitivity, mitigated the aggressive biological features, promoted cell apoptosis in vitro and inhibited tumor growth in vivo. Mechanistic studies revealed that SGC7901/DOX cells underwent epithelial-mesenchymal transition (EMT) which was induced by Akt activation, and through activating PTEN, RES inhibited the Akt pathway, and then achieved the reversion of EMT.

CONCLUSION

RES serves as a novel solution to reverse the DOX-resistance of gastric cancer via preventing EMT by modulating PTEN/Akt signaling pathway. DOX-RES combined treatment provides a promising future for gastric cancer patients to postpone drug resistance and prolong survival.

Targeting CD146 in combination with vorinostat for the treatment of ovarian cancer cells

Drug resistance is the predominant cause of mortality in late-stage patients with ovarian cancer. Histone deacetylase inhibitors (HDACis) have emerged as a novel type of second line drug with high specificity for tumor cells, including ovarian cancer cells. However, HDACis usually exhibit relatively low potencies when used as a single agent. The majority of current clinical trials are combination strategies. These strategies are more empirical than mechanism-based applications. Previously, it was reported that the adhesion molecule cluster of differentiation 146 (CD146) is significantly induced in HDACi-treated tumor cells. The present study additionally confirmed that the induction of CD146 is a common phenomenon in vorinostat-treated ovarian cancer cells. AA98, an anti-CD146 monoclonal antibody (mAb), was used to target CD146 function. Synergistic antitumoral effects between AA98 and vorinostat were examined in vitro and in vivo. The potential effect of combined AA98 and vorinostat treatment on the protein kinase B (Akt) pathway was determined by western blotting. The present study found that targeting of CD146 substantially enhanced vorinostat-induced killing via the suppression of activation of Akt pathways in ovarian cancer cells. AA98 in combination with vorinostat significantly inhibited cell proliferation and increased apoptosis. In vivo, AA98 synergized with vorinostat to inhibit tumor growth and prolong survival in ovarian cancer. These data suggest that an undesired induction of CD146 may serve as a protective response to offset the antitumor efficacy of vorinostat. By contrast, targeting CD146 in combination with vorinostat may be exploited as a novel strategy to more effectively kill ovarian cancer cells.

Proteomics Analysis of Ovarian Cancer Cell Lines and Tissues Reveals Drug Resistance-associated Proteins

BACKGROUND

Carboplatin and paclitaxel form the cornerstone of chemotherapy for epithelial ovarian cancer, however, drug resistance to these agents continues to present challenges. Despite extensive research, the mechanisms underlying this resistance remain unclear.

MATERIALS AND METHODS

A 2D-gel proteomics method was used to analyze protein expression levels of three human ovarian cancer cell lines and five biopsy samples. Representative proteins identified were validated via western immunoblotting. Ingenuity pathway analysis revealed metabolomic pathway changes.

RESULTS

A total of 189 proteins were identified with restricted criteria. Combined treatment targeting the proteasome-ubiquitin pathway resulted in re-sensitisation of drug-resistant cells. In addition, examination of five surgical biopsies of ovarian tissues revealed α-enolase (ENOA), elongation factor Tu, mitochondrial (EFTU), glyceraldehyde-3-phosphate dehydrogenase (G3P), stress-70 protein, mitochondrial (GRP75), apolipoprotein A-1 (APOA1), peroxiredoxin (PRDX2) and annexin A (ANXA) as candidate biomarkers of drug-resistant disease.

CONCLUSION

Proteomics combined with pathway analysis provided information for an effective combined treatment approach overcoming drug resistance. Analysis of cell lines and tissues revealed potential prognostic biomarkers for ovarian cancer.

Differentiating responses of lung cancer cell lines to Doxorubicin exposure: in vitro Raman micro spectroscopy, oxidative stress and bcl-2 protein expression

The potential of Raman micro spectroscopy as an in vitro, non-invasive tool for clinical applications has been demonstrated in recent years, specifically for cancer research. To further illustrate its potential as a high content and label free technique, it is important to show its capability to elucidate drug mechanisms of action and cellular resistances. In this study, cytotoxicity assays were employed to establish the toxicity profiles for 24 hr exposure of lung cancer cell lines, A549 and Calu-1, to the commercially available drug, doxorubicin (DOX). Raman spectroscopy, coupled with Confocal Laser Scanning Microscopy and Flow Cytometry, was used to track the DOX mechanism of action, at a subcellular level, and to study the mechanisms of cellular resistance to DOX. Biomarkers related to the drug mechanism of action and cellular resistance to apoptosis, namely reactive oxygen species (ROS) and bcl-2 protein expression, respectively, were also measured and correlated to Raman spectral profiles. Calu-1 cells are shown to exhibit spectroscopic signatures of both direct DNA damage due to intercalation in the nucleus and indirect damage due to oxidative stress in the cytoplasm, whereas the A549 cell line only exhibits signatures of the former mechanism of action. PCA of nucleolar, nuclear and cytoplasmic regions of A549 and Calu-1 with corresponding loadings of PC1 and PC2.

Attenuated JNK signaling in multidrug-resistant leukemic cells. Dual role of MAPK in cell survival

Having found previously that leukemic cells with multidrug resistant (MDR) phenotype, but not their sensitive counterparts, exhibit collateral sensitivity to cold stress in a P-gp-dependent manner, our aim was to study the signaling pathways involved in this phenomenon in sensitive (L1210) and resistant cells (L1210R and CBMC-6). It was observed that the acquisition of MDR phenotype by leukemic cells or their transfection with the extrussion pump, P-gp, modifies the activation profile and regulation of Mitogen-Activated Protein Kinases (MAPK) in cells exposed to low temperatures. More specifically, cold stress provoked the activation of c-Jun N-terminal kinase (JNK) in sensitive cells, while attenuated JNK signaling was observed in MDR cells. This effect was also observed, although with less intensity, in P-gp-transfected cells. Using pharmacological inhibitors to determine the role of MAPK in leukemic cell survival in physiological conditions or under cold stress, a dual temperature-dependent role was observed for JNK in MDR cell survival. At 37°C JNK is necessary for the survival of parental, resistant and P-gp-transfected cells; however, the use of inhibitors of either extracellular signal-regulated protein kinase (ERK) or JNK significantly counteracts cold-induced death of resistant and P-gp-transfected cells, supporting a role for ERK and JNK in cold-stress induced cell death. Finally, a connectivity model concerning MAPK is proposed, summarizing how cold stress and MDR-1 might trigger apoptosis in resistant cell lines. These findings on MDR cells may assist in the design of specific therapeutic strategies to complement current chemotherapy.

Plasma Amyloid-Beta Levels in Patients with Different Types of Cancer

Several epidemiological investigations indicate that cancer survivors have a lower risk for Alzheimer's disease (AD) and vice versa. However, the associations between plasma amyloid-beta (Aβ) levels with cancer remain largely unknown. In this case-control study, 110 cancer patients, 70 AD patients, and 70 age- and gender-matched normal controls were recruited. The cancer types include esophagus cancer, colorectal cancer, hepatic cancer, and lung cancer, all of which were reported to be associated with a lower risk for AD. Plasma levels of Aβ40, Aβ42, common pro-inflammatory cytokines, IL-1β, IL-6, TNF-α, IFN-γ, anti-inflammatory IL-4, chemokines, and cytokines MCP-1 were measured with enzyme-linked immunosorbent assay (ELISA) kits. Plasma levels of Aβ40 and Aβ42 in all cancer patients were higher than that in normal controls. More specifically, hepatic cancer patients exhibited significantly higher plasma Aβ levels. No significant difference in plasma Aβ levels was found between chemotherapy and no chemotherapy subgroups. Plasma Aβ levels were not significantly correlated with pro-inflammatory cytokines, anti-inflammatory, chemokines, and cytokines. Peripheral Aβ levels increased in cancer patients, especially in patients with hepatic cancer, independent of chemotherapy and inflammation. Further verification is required for the association between plasma Aβ and cancer.

Targeting EZH2 regulates tumor growth and apoptosis through modulating mitochondria dependent cell-death pathway in HNSCC

EZH2 is a negative prognostic factor and is overexpressed or activated in most human cancers including head and neck squamous cell carcinoma (HNSCC). Analysis of The Cancer Genome Atlas (TCGA) HNSCC data indicated that EZH2 over-expression was associated with high tumor grade and conferred poor prognosis. EZH2 inhibition triggered cell apoptosis, cell cycle arrest and decreased cell growth in vitro. MICU1 (mitochondrial calcium uptake1) was shown to be down regulated when EZH2 expression was inhibited in HNSCC. When the EZH2 and MICU1 were inhibited, HNSCC cells became susceptible to cell cycle arrest and apoptosis. Mitochondrial membrane potential and cytosolic Ca²⁺ concentration analysis suggested that EZH2 and MICU1 were required to maintain mitochondrial membrane potential stability. A xenograft tumor model was used to confirm that EZH2 depletion inhibited HNSCC cell growth and induced tumor cell apoptosis. In summary, EZH2 is a potential anti-tumor target in HNSCC.

Lentivirus-mediated downregulation of MAT2B inhibits cell proliferation and induces apoptosis in melanoma

Malignant melanoma is the most lethal of skin cancers and its pathogenesis is complex and heterogeneous. The efficacy of conventional therapeutic regimens for melanoma remains limited. Thus, it is important to explore novel effective therapeutic targets in the treatment of melanoma. The MAT2B gene encodes for the regulatory subunit of methionine adenosyltransferase (MAT). Recent studies have suggested that MAT2B may have functional roles other than modulating catalytic activity of MAT. In order to identify the roles of MAT2B in the tumorigenesis of malignant melanoma, we compared MAT2B expression profile in melanoma tissues with that in benign nevus samples. We employed lentivirus-mediated RNAi to downregulate the expression of MAT2B in malignant melanoma cell lines (A375 and Mel-RM), and investigated the effects of MAT2B on cell growth, colony-formation ability and apoptosis in vitro, as well as tumor growth of a xenograft model in vivo. The expression levels of BCL2 and XAF1 proteins, which were closely related to tumor cell apoptosis, were analyzed by western blot analysis. Our data showed that MAT2B was elevated in both primary and metastatic melanoma tissues compared with benign nevus samples. Lentivirus-mediated downregulation of MAT2B suppressed cell growth, colony formation and induced apoptosis in A375 and Mel-RM cell lines in vitro, affected protein expression of BCL2 and XAF1, extended the transplanted tumor growth in vivo. These results indicated that MAT2B was critical in the proliferation of melanoma cells and tumorigenicity. It may be considered as a potential anti-melanoma therapeutic target.

Retinal regeneration mechanisms linked to multiple cancer molecules: A therapeutic conundrum

Over the last decade, a large number of research articles have been published demonstrating regeneration and/or neuroprotection of retinal ganglion cells following manipulation of specific genetic and molecular targets. Interestingly, of the targets that have been identified to promote repair following visual system damage, many are genes known to be mutated in different types of cancer. This review explores recent literature on the potential for modulating cancer genes as a therapeutic strategy for visual system repair and looks at the potential clinical challenges associated with implementing this type of therapy. We also discuss signalling mechanisms that have been implicated in cancer and consider how similar mechanisms may improve axonal regeneration in the optic nerve.

A journey beyond apoptosis: new enigma of controlling metastasis by pro-apoptotic Par-4

Prostate apoptotic response 4 (Par-4) is coined as a therapeutic protein since owing to its diverse physiologically relevant properties, especially in the cancer perspective. Albeit, Par-4 expression is not restricted to any specific tissue/organ, apart from cell death promotion (due to challenging threats), the other biological role of Par-4 is convincingly emerging. In the recent years, several laboratories have intended to dissect the signaling or mechanisms involved in Par-4 activation to augment apoptosis cascades but new developments in Par-4 research have widened its therapeutic potential. One of these important avenues is the prevention of metastasis by pro-apoptotic Par-4. In this review, we will focus on the therapeutic perspective of Par-4 with a special reference to its (Par-4) virgin prospect of devastating metastasis control.