Cancer-type-specific crosstalk between autophagy, necroptosis and apoptosis as a pharmacological target

Cyclovirobuxine D Exerts Anticancer Effects by Suppressing the EGFR-FAK-AKT/ERK1/2-Slug Signaling Pathway in Human Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC), the sixth most common malignancy worldwide, is characterized by a dismal prognosis due to high recurrence and metastasis rates. Thus, the need for the development of novel chemotherapeutic drugs is urgent. Cyclovirobuxine D (CVB-D), a steroidal alkaloid extracted from Buxus microphylla that has been extensively used to relieve the symptoms of cardiovascular diseases, has shown promising antineoplastic effects in recent studies. However, the therapeutic effects and underlying mechanisms of CVB-D on HCC remain largely unelucidated. This study experimentally indicated that CVB-D can repress HCC cell proliferation by arresting the cell cycle in G2 phase and can facilitate apoptosis. In addition, the migratory and invasive capabilities of HCC cells were noticeably attenuated by a nonlethal dose of CVB-D, and this attenuation was correlated with the inhibition of epithelial-mesenchymal transition (EMT). Moreover, in vivo, CVB-D displayed excellent anticancer effects in HCC tumor-bearing nude mice. Regarding the molecular mechanisms of CVB-D activity, decreased Slug expression was determined to be associated with the aforementioned anti-HCC functions of this extract, which might be regulated by epidermal growth factor receptor (EGFR) through the focal adhesion kinase (FAK)-associated PI3K/AKT and MEK/ERK1/2 signaling pathways. Collectively, our results revealed the suppressive effects of CVB-D on progressive behaviors of HCC, including proliferation, migration, invasion, and EMT, in addition to its outstanding proapoptotic effects, which were correlated with the inhibition of the EGFR-FAK-AKT/ERK1/2-Slug signaling pathway. These discoveries provide an experimental and theoretical foundation for the use of CVB-D as a promising candidate for HCC therapy.

Inhibiting lysine 353 oxidation of GRP78 by a hypochlorous probe targeting endoplasmic reticulum promotes autophagy in cancer cells

The level of hypochlorous acid (HOCl) in cancer cells is higher than that in non-cancer cells. HOCl is an essential signal for the regulation of cell fate and works mainly through the protein post-translational modifications in cancer cells. However, the mechanism of HOCl regulating autophagy has not been clarified. Here we reported that a HOCl probe named ZBM-H targeted endoplasmic reticulum and induced an intact autophagy flux in lung cancer cells. Furthermore, ZBM-H promoted the binding of GRP78 to AMPK and increased the phosphorylation of AMPK in a dose- and time-dependent manner. GRP78 knockdown inhibited ZBM-H-induced AMPK phosphorylation and ZBM-H-stimulated autophagy. In addition, mass spectrometry combined with point mutation experiments revealed that ZBM-H increased GRP78 activity by inhibiting HOCl-induced lysine 353 oxidation of GRP78. Following ZBM-H treatment in vitro and in vivo, cell growth was significantly inhibited while apoptosis was induced. Nevertheless, exogenous HOCl partially reversed ZBM-H-inhibited cell growth and ZBM-H-induced GRP78 activation. In brief, we found that an endoplasmic reticulum-targeted HOCl probe named ZBM-H, acting through attenuating HOCl-induced GRP78 oxidation, inhibited tumor cell survival by promoting autophagy and apoptosis. Overall, these data demonstrated a novel mechanism of hypochlorous acid regulating autophagy by promoting the oxidation modification of GRP78.

Anticancer Ruthenium(III) Complexes and Ru(III)-Containing Nanoformulations: An Update on the Mechanism of Action and Biological Activity

The great advances in the studies on metal complexes for the treatment of different cancer forms, starting from the pioneering works on platinum derivatives, have fostered an increasingly growing interest in their properties and biomedical applications. Among the various metal-containing drugs investigated thus far, ruthenium(III) complexes have emerged for their selective cytotoxic activity in vitro and promising anticancer properties in vivo, also leading to a few candidates in advanced clinical trials. Aiming at addressing the solubility, stability and cellular uptake issues of low molecular weight Ru(III)-based compounds, some research groups have proposed the development of suitable drug delivery systems (e.g., taking advantage of nanoparticles, liposomes, etc.) able to enhance their activity compared to the naked drugs. This review highlights the unique role of Ru(III) complexes in the current panorama of anticancer agents, with particular emphasis on Ru-containing nanoformulations based on the incorporation of the Ru(III) complexes into suitable nanocarriers in order to enhance their bioavailability and pharmacokinetic properties. Preclinical evaluation of these nanoaggregates is discussed with a special focus on the investigation of their mechanism of action at a molecular level, highlighting their pharmacological potential in tumour disease models and value for biomedical applications.

Ginsenoside Compound K Induces Ros-Mediated Apoptosis and Autophagic Inhibition in Human Neuroblastoma Cells In Vitro and In Vivo

Autophagy can result in cellular adaptation, as well as cell survival or cell death. Modulation of autophagy is increasingly regarded as a promising cancer therapeutic approach. Ginsenoside compound K (CK), an active metabolite of ginsenosides isolated from Panax ginseng C.A. Meyer, has been identified to inhibit growth of cancer cell lines. However, the molecular mechanisms of CK effects on autophagy and neuroblastoma cell death have not yet been investigated. In the present study, CK inhibited neuroblastoma cell proliferation in vitro and in vivo. Treatment by CK also induced the accumulation of sub-G1 population, and caspase-dependent apoptosis in neuroblastoma cells. In addition, CK promotes autophagosome accumulation by inducing early-stage autophagy but inhibits autophagic flux by blocking of autophagosome and lysosome fusion, the step of late-stage autophagy. This effect of CK appears to be mediated through the induction of intracellular reactive oxygen species (ROS) and mitochondria membrane potential loss. Moreover, chloroquine, an autophagy flux inhibitor, further promoted CK-induced apoptosis, mitochondrial ROS induction, and mitochondria damage. Interestingly, those promoted phenomena were rescued by co-treatment with a ROS scavenging agent and an autophagy inducer. Taken together, our findings suggest that ginsenoside CK induced ROS-mediated apoptosis and autophagic flux inhibition, and the combination of CK with chloroquine, a pharmacological inhibitor of autophagy, may be a novel therapeutic potential for the treatment of neuroblastoma.

Inhibition of the hedgehog pathway for the treatment of cancer using Itraconazole

Itraconazole (ITZ) is an anti-fungal drug that has been used in clinical practice for nearly 35 years. Recently, numerous experiments have shown that ITZ possesses anti-cancer properties. The Hedgehog (Hh) pathway plays a pivotal role in fundamental processes, including embryogenesis, structure, morphology and proliferation in various species. This pathway is typically silent in adult cells, and inappropriate activity is linked to various tumor types. The most important mechanism of ITZ in the treatment of cancer is inhibition of the Hh pathway through the inhibition of smoothened receptors (SMO), glioma-associated oncogene homologs (GLI), and their downstream targets. In this review, we discuss the mechanisms of ITZ in the treatment of cancer through inhibition of the Hh pathway, which includes anti-inflammation, prevention of tumor growth, induction of cell cycle arrest, induction of apoptosis and autophagy, prevention of angiogenesis, and drug resistance. We also discuss the clinical use of ITZ in many types of cancers. We hope this review will provide more information to support future studies on ITZ in the treatment of various cancers.

Unlike reactivity of mono- and binuclear imine-copper(II) complexes toward melanoma cells via a tyrosinase-dependent mechanism

The cytotoxicity of a dinuclear imine-copper (II) complex 2, and its analogous mononuclear complex 1, toward different melanoma cells, particularly human SKMEL-05 and SKMEL-147, was investigated. Complex 2, a tyrosinase mimic, showed much higher activity in comparison to complex 1, and its reactivity was verified to be remarkably activated by UVB-light, while the mononuclear compound showed a small or negligible effect. Further, a significant dependence on the melanin content in the tumor cells, both from intrinsic pigmentation or stimulated by irradiation, was observed in the case of complex 2. Similar tests with keratinocytes and melanocytes indicated a much lower sensitivity to both copper (II) complexes, even after exposition to UV light. Clonogenic assays attested that the fractions of melanoma cells survival were much lower under treatment with complex 2 compared to complex 1, both with or without previous irradiation of the cells. The process also involves generation of reactive oxygen species (ROS), as verified by EPR spectroscopy, and by using fluorescence indicators. Autophagic assays indicated a remarkable formation of cytoplasmic vacuoles in melanomas treated with complex 2, while this effect was not observed in similar treatment with complex 1. Monitoring of specific protein LC3 corroborated the simultaneous occurrence of autophagy. A balance interplay between different modes of cell death, apoptosis and autophagy, occurs when melanomas were treated with the dinuclear complex 2, in contrast to the mononuclear complex 1. These results pointed out to different mechanisms of action of such complexes, depending on its nuclearity.

The AMPK-Parkin axis negatively regulates necroptosis and tumorigenesis by inhibiting the necrosome

The receptor-interacting protein 1 (RIPK1)/RIPK3 kinases play important roles in necroptosis that is closely linked to inflammatory response. Although the activation of necroptosis is well characterized, how necroptosis is tuned down is largely unknown. Here, we found that Parkin (also known as PARK2), an E3 ubiquitin ligase implicated in Parkinson’s disease and a tumor suppressor, regulates necroptosis and inflammation by regulating necrosome formation. Parkin prevents the formation of the RIPK1-RIPK3 complex by promoting polyubiquitination of RIPK3. Parkin is phosphorylated and activated by the cellular energy sensor AMP-activated protein kinase (AMPK). Parkin-deficiency potentiates the RIPK1-RIPK3 interaction, RIPK3 phosphorylation, and necroptosis. Importantly, Parkin deficiency enhances inflammation and inflammation-associated tumorigenesis. These findings demonstrate that the AMPK-Parkin axis negatively regulates necroptosis via inhibiting the RIPK1-RIPK3 complex formation and this regulation may serve as an important mechanism to fine-tune necroptosis and inflammation.

Bufadienolides induce apoptosis and autophagy by inhibiting the AKT signaling pathway in melanoma A‑375 cells

The purpose of the present study was to investigate the effect of bufadienolides on the A‑375 melanoma cell line, and to delineate the underlying mechanism. A Cell Counting Kit‑8 assay was used to determine the viability of the cells, and flow cytometry was used to evaluate apoptosis. Western blot analysis was used to evaluate the expression levels of proteins involved in the AKT pathway that are associated with apoptosis and autophagy. The results demonstrated that bufadienolides reduced the viability of A‑375 cells in a dose‑ and a time‑dependent manner. Following treatment with bufadienolides, A‑375 cells exhibited clear properties that were characteristic of apoptosis and autophagy. The expression levels of the pro‑apoptotic proteins Bax and p53 were upregulated, whereas those of the anti‑apoptotic proteins, Bcl‑2 and caspase‑3 were downregulated. In addition, the level of a protein known to be associated with autophagy, microtubule‑associated proteins 1A/1B light chain 3‑II, was increased, whereas that of p62 protein was reduced. Finally, the AKT signaling pathway was blocked in the bufadienolide‑treated A‑375 cells. In conclusion, these results revealed that bufadienolides effectively induced apoptosis and autophagy in A‑375 cells via the AKT pathway, and therefore may be one of the candidate targets for the future development of targeted drugs to treat melanoma.

Shikonin derivatives for cancer prevention and therapy

Phytochemicals gained considerable interest during the past years as source to develop new treatment options for chemoprevention and cancer therapy. Motivated by the fact that a majority of established anticancer drugs are derived in one way or another from natural resources, we focused on shikonin, a naphthoquinone with high potentials to be further developed as preventive or therapeutic drug to fight cancer. Shikonin is the major chemical component of Lithospermum erythrorhizon (Purple Cromwell) roots. Traditionally, the root extract has been applied to cure dermatitis, burns, and wounds. Over the past three decades, the anti-inflammatory and anticancer effects of root extracts, isolated shikonin as well as semi-synthetic and synthetic derivatives and nanoformulations have been described. In vitro and in vivo experiments were conducted to understand the effect of shikonin at cellular and molecular levels. Preliminary clinical trials indicate the potential of shikonin for translation into clinical oncology. Shikonin exerts additive and synergistic interactions in combination with established chemotherapeutics, immunotherapeutic approaches, radiotherapy and other treatment modalities, which further underscores the potential of this phytochemical to be integrated into standard treatment regimens.

The role of necroptosis in cancer biology and therapy

Apoptosis resistance is to a large extent a major obstacle leading to chemotherapy failure during cancer treatment. Bypassing the apoptotic pathway to induce cancer cell death is considered to be a promising approach to overcoming this problem. Necroptosis is a regulated necrotic cell death modality in a caspase-independent fashion and is mainly mediated by Receptor-Interacting Protein 1 (RIP1), RIP3, and Mixed Lineage Kinase Domain-Like (MLKL). Necroptosis serves as an alternative mode of programmed cell death overcoming apoptosis resistance and may trigger and amplify antitumor immunity in cancer therapy.The role of necroptosis in cancer is complicated. The expression of key regulators of the necroptotic pathway is generally downregulated in cancer cells, suggesting that cancer cells may also evade necroptosis to survive; however, in certain types of cancer, the expression level of key mediators is elevated. Necroptosis can elicit strong adaptive immune responses that may defend against tumor progression; however, the recruited inflammatory response may also promote tumorigenesis and cancer metastasis, and necroptosis may generate an immunosuppressive tumor microenvironment. Necroptosis also reportedly promotes oncogenesis and cancer metastasis despite evidence demonstrating its antimetastatic role in cancer. In addition, necroptotic microenvironments can direct lineage commitment to determine cancer subtype development in liver cancer. A plethora of compounds and drugs targeting necroptosis exhibit potential antitumor efficacy, but their clinical feasibility must be validated.Better knowledge of the necroptotic pathway mechanism and its physiological and pathological functions is urgently required to solve the remaining mysteries surrounding the role of necroptosis in cancer. In this review, we briefly introduce the molecular mechanism and characteristics of necroptosis, the interplay between necroptosis and other cell death mechanisms, crosstalk of necroptosis and metabolic signaling and detection methods. We also summarize the intricate role of necroptosis in tumor progression, cancer metastasis, prognosis of cancer patients, cancer immunity regulation, cancer subtype determination and cancer therapeutics.

Exploring cellular uptake, accumulation and mechanism of action of a cationic Ru-based nanosystem in human preclinical models of breast cancer

According to WHO, breast cancer incidence is increasing so that the search for novel chemotherapeutic options is nowadays an essential requirement to fight neoplasm subtypes. By exploring new effective metal-based chemotherapeutic strategies, many ruthenium complexes have been recently proposed as antitumour drugs, showing ability to impact on diverse cellular targets. In the framework of different molecular pathways leading to cell death in human models of breast cancer, here we demonstrate autophagy involvement behind the antiproliferative action of a ruthenium(III)-complex incorporated into a cationic nanosystem (HoThyRu/DOTAP), proved to be hitherto one of the most effective within the suite of nucleolipidic formulations we have developed for the in vivo transport of anticancer ruthenium(III)-based drugs. Indeed, evidences are implicating autophagy in both cancer development and therapy, and anticancer interventions endowed with the ability to trigger this biological response are currently considered attractive oncotherapeutic approaches. Moreover, crosstalk between apoptosis and autophagy, regulated by finely tuned metallo-chemotherapeutics, may provide novel opportunities for future improvement of cancer treatment. Following this line, our in vitro and in vivo preclinical investigations suggest that an original strategy based on suitable formulations of ruthenium(III)-complexes, inducing sustained cell death, could open new opportunities for breast cancer treatment, including the highly aggressive triple-negative subtype.

Sodium butyrate induces autophagic apoptosis of nasopharyngeal carcinoma cells by inhibiting AKT/mTOR signaling

Previously, we confirmed the anti-tumor effects of sodium butyrate (NaBu) in nasopharyngeal carcinoma (NPC). However, its molecular mechanisms have not be fully elucidated. In this study, we studied the effects of NaBu on autophagy and explored the relation between NaBu associated autophagy and apoptosis in NPC cells. EGFP-LC3 plasmids were introduced into NPC cells to observed the effects of NaBu on autophagy flux with or without chloroquine (CQ) addition. Autophagy markers were also detected by Western blot. Under NaBu treatment, autophagy and apoptosis markers were detected simultaneously at different time. Then, to explore the roles of autophagy in NaBu induced apoptosis, the effects of autophagy inhibition, via specific inhibitor treatment or key gene knockdown, were analyzed. At last, the upstream signaling and its roles in NaBu induced autophagy and apoptosis were also analyzed. Increased LC3 dots and LC3-II accumulation indicated that NaBu can promote autophagy flux in NPC cells. LC3-II accumulation was earlier than cleaved PARP increment suggesting autophagy activation is prior to apoptosis activation, which was validated by flow cytometry mediated apoptosis analysis. Moreover, autophagy inhibition, achieved by 3-MA treatment or BECN1 knockdown, can antagonize NaBu induced apoptosis reflecting by re-deregulated cPARP and apoptotic rates. Furthermore, NaBu treatment inhibited the AKT/mTOR axis indicated by deregulated p-AKT(S473) and p-mTOR(S2448) and ectopic AKT expression both suppressed NaBu induced autophagy and apoptosis. At last, Western blot showed that HDAC6 dependent EGFR deregulation may account for the NaBu associated AKT/mTOR inhibition. NaBu can induce autophagic apoptosis via suppressing AKT/mTOR axis in NPC cells. Our results suggest that combination of autophagy inhibitors and deacetylase inhibitors may not be recommended in NPC clinical treatment.

Capsaicin induces apoptosis and autophagy in human melanoma cells

Melanoma is the most lethal type of skin cancer; rapid metastasis and resistance to conventional radio- and chemotherapy make melanoma the most aggressive type of skin cancer. In addition, there is a high recurrence rate within 1 year among patients with melanoma following traditional treatment by chemotherapy or immunotherapy, and these treatment options are only useful in advanced stages. As the efficiency of treatment options for melanoma is not ideal, the present study aimed to confirm that capsaicin has inhibitory effects on the human melanoma A375 and C8161 cell lines in vitro. Capsaicin, the active component of peppers, has been reported to possess substantial anticarcinogenic and antimutagenic activities. Additionally, capsaicin exhibits an inhibitory effect on tumor growth in numerous malignant cell lines. In the present study, flow cytometry, fluorescent puncta detection and western blotting were performed. The experimental results indicated that capsaicin activated apoptosis, and that apoptosis induction was associated with poly(ADP-ribose) polymerase (PARP) cleavage and activation of caspase-3. Additionally, the formation of autophagosomes and accumulation of microtubule-associated proteins 1A/1B light chain 3B-II and beclin 1 suggested that capsaicin induced autophagy in human melanoma cells. Furthermore, inhibiting capsaicin-induced autophagy promoted the activation of cleaved caspase-3 and PARP proteins, which are associated with apoptosis. In addition, inhibition of autophagy using 3-MA enhanced capsaicin-induced cell death, indicating that capsaicin-induced autophagy is a pro-survival process in cells. In conclusion, the results of the present study revealed that capsaicin induced cell apoptosis and autophagy in human melanoma cells and capsaicin may be considered as a novel candidate drug for melanoma treatment.

Redox biology of regulated cell death in cancer: A focus on necroptosis and ferroptosis

Redox changes and generation of reactive oxygen species (ROS) are part of normal cell metabolism. While low ROS levels are implicated in cellular signaling pathways necessary for survival, higher levels play major roles in cancer development as well as cell death signaling and execution. A role for redox changes in apoptosis has been long established; however, several new modalities of regulated cell death have been brought to light, for which the importance of ROS production as well as ROS source and targets are being actively investigated. In this review, we summarize recent findings on the role of ROS and redox changes in the activation and execution of two major forms of regulated cell death, necroptosis and ferroptosis. We also discuss the potential of using modulators of these two forms of cell death to exacerbate ROS as a promising anticancer therapy.

Ginsenoside Rg5 induces apoptosis and autophagy via the inhibition of the PI3K/Akt pathway against breast cancer in a mouse model

Breast cancer is the most frequently diagnosed cancer and has become the main cause of cancer-related death among women worldwide. Traditional chemotherapy for breast cancer has serious side effects for patients, such as the first-line drug docetaxel. Ginsenoside Rg5, a rare ginsenoside and the main ingredient extracted from fine black ginseng, has been proved to have anti-breast cancer efficacy in vitro. Here, the in vivo anti-breast cancer efficacy, side effects and potential molecular mechanisms of Rg5 were investigated on a BALB/c nude mouse model of human breast cancer. The tumor growth inhibition rate of high dose Rg5 (20 mg kg-1) was 71.4 ± 9.4%, similar to that of the positive control docetaxel (72.0 ± 9.1%). Compared to docetaxel, Rg5 showed fewer side effects in the treatment of breast cancer. Treatment with Rg5 induced apoptosis and autophagy in breast cancer tissues. Rg5 was proved to induce caspase-dependent apoptosis via the activation of the extrinsic death receptor and intrinsic mitochondrial signaling pathways. The autophagy induction was related to the formation of an autophagosome and accumulation of LC3BII, P62 and critical Atg proteins. Further studies showed that Rg5 in a dose-dependent manner induced apoptosis and autophagy through the inhibition of the PI3K/Akt signaling pathway as indicated by the reduced phosphorylation level of PI3K and Akt. Taken together, Rg5 could be a novel and promising clinical antitumor drug targeting breast cancer.

Scandenolone from Cudrania tricuspidata fruit extract suppresses the viability of breast cancer cells (MCF-7) in vitro and in vivo

Scandenolone, an isoflavone, has shown anti-cancer potential. In this study, we extracted scandenolone from Cudrania tricuspidata fruit and evaluated its anti-breast cancer effects as well as toxicity in cell and animal models. In cell model, scandenolone suppressed the breast cancer MCF-7 cells viability, ceased mitotic cell cycle, decreased mitochondrial membrane potential, up-regulated cleaved caspase-3 and promoted the phosphorylation of p53. Additionally, this isoflavone promoted cell apoptosis and induced a sustained activation of the phosphorylation of p38 and ERK, but not JNK and Akt. The effects were further verified in a human MCF-7 breast cancer xenograft model, where scandenolone efficiently suppressed the cancer growth and increased apoptotic cells in tumor tissue. However scandenolone has also shown certain toxicity to normal hepatocytes and breast epithelial cells. It could be concluded that scandenolone suppressed the growth of breast cancer cells, but its toxicity towards normal cells might limit its potential clinical use.

miR-506 contributes to malignancy of cutaneous squamous cell carcinoma via targeting of P65 and LAMC1

Previous research has shown that microRNA 506 (miR-506) functions as an essential modulator in the development of many biological reactions, including multiple cancers. However, its involvement in cutaneous squamous cell carcinoma (CSCC) has been rarely reported. In the present work, we investigated the molecular mechanism and function of miR-506 in the regulation of CSCC cell viability and metastasis (migration and invasion). We observed that miR-506 expression was upregulated in both CSCC tissues and cell lines, and that decreased miR-506 expression led to repressed tumorigenesis in CSCC cells. Furthermore, flow cytometry revealed that the depletion of miR-506 resulted in decreased proliferation and increased apoptotic levels in CSCC cells. Meanwhile, it was found that miR-506 decreased CSCC cell migration and invasion in vitro. The dual-luciferase reporter assay also revealed that miR-506 targets the 3'-UTRs of p65 and Laminin C1 (LAMC1) for silencing. Silencing of p65 expression counteracted the pro-apoptotic influence of miR-506 depletion in CSCC cells, while inhibition of LAMC1 expression restored the migration and invasion properties of the CSCC cells. Therefore, the results provide evidence for the need to probe the biological and molecular mechanisms behind the development and progression of CSCC and may lead to novel treatment CSCC strategies.

Natural modulators of the hallmarks of immunogenic cell death

Natural compounds act as immunoadjuvants as their therapeutic effects trigger cancer stress response and release of damage-associated molecular patterns (DAMPs). These reactions occur through an increase in the immunogenicity of cancer cells that undergo stress followed by immunogenic cell death (ICD). These processes result in a chemotherapeutic response with a potent immune-mediating reaction. Natural compounds that induce ICD may function as an interesting approach in converting cancer into its own vaccine. However, multiple parameters determine whether a compound can act as an ICD inducer, including the nature of the inducer, the premortem stress pathways, the cell death pathways, the intrinsic antigenicity of the cell, and the potency and availability of an immune cell response. Thus, the identification of hallmarks of ICD is important in determining the prognostic biomarkers for new therapeutic approaches and combination treatments.

Targeting Cancer with Phytochemicals via Their Fine Tuning of the Cell Survival Signaling Pathways

The role of phytochemicals as potential prodrugs or therapeutic substances against tumors has come in the spotlight in the very recent years, thanks to the huge mass of encouraging and promising results of the in vitro activity of many phenolic compounds from plant raw extracts against many cancer cell lines. Little but important evidence can be retrieved from the clinical and nutritional scientific literature, where flavonoids are investigated as major pro-apoptotic and anti-metastatic compounds. However, the actual role of these compounds in cancer is still far to be fully elucidated. Many of these phytochemicals act in a pleiotropic and poorly specific manner, but, more importantly, they are able to tune the reactive oxygen species (ROS) signaling to activate a survival or a pro-autophagic and pro-apoptosis mechanism, depending on the oxidative stress-responsive endowment of the targeted cell. This review will try to focus on this issue.

SIRT6 overexpression induces apoptosis of nasopharyngeal carcinoma by inhibiting NF-κB signaling

BACKGROUND

Previous reports show that SIRT6 serves as a critical modulator of the development of multiple malignancies as well as other disorders. However, its role in nasopharyngeal carcinoma (NPC) is unknown. Thus, we elucidated the effects of SIRT6 on the survival of NPC cells, and modulation of cell death.

METHODS

We found that expression of SIRT6 is downregulated in ten human NPC specimens as well as in the human NPC cell lines, 5-8 F and CNE1, as compared with that in healthy tissues and normal nasopharyngeal NP69 cells. The MTT assay and colony formation assay revealed that upregulation of SIRT6 impaired the proliferation, as well as the survival of 5-8 F and CNE1 cells. The TUNEL assay, annexin V-FITC/propidium iodide, and flow cytometry were performed to detect apoptosis. The results revealed that the expression of SIRT6 resulted in increased apoptosis.

RESULTS

Western blotting results showed that SIRT6 overexpression decreased anti-apoptotic Bcl-2 levels, whereas it promoted an increase in pro-apoptotic Bax and cleaved caspase-3 levels. Moreover, NF-κB levels were markedly reduced in cells expressing SIRT6, whereas they were increased in cells transfected with shRNA-SIRT6. Recovery of NF-κB expression was found to counter the suppressive influence of SIRT6 on NPC cell survival, whereas, NF-κB knockdown increased apoptosis of NPC cells.

CONCLUSION

Thus, the findings of our study offer insight into the biological and molecular mechanisms underlying the development of NPC and may lead to the development of new and innovative strategies for the treatment of NPC.

Nimbolide, a neem limonoid inhibits cytoprotective autophagy to activate apoptosis via modulation of the PI3K/Akt/GSK-3β signalling pathway in oral cancer

Of late, nimbolide, a limonoid from the neem tree (Azadirachta indica) has gained increasing research attention owing to its potent antiproliferative and apoptosis-inducing effects. The present study was designed to investigate the effect of nimbolide on autophagy and the time point at which the phosphorylation status of GSK-3β and PI3K dictate the choice between autophagy and apoptosis in SCC131 and SCC4 oral cancer cells. Additionally, we analysed changes in the expression of proteins involved in autophagy and apoptosis after therapeutic intervention with nimbolide in a hamster model of oral oncogenesis. Furthermore, we also demonstrate changes in the expression of key genes involved in apoptosis and autophagy during the stepwise evolution of hamster and human OSCCs. Nimbolide-induced stereotypical changes in oral cancer cells characteristic of both apoptosis and autophagy. Time-course experiments revealed that nimbolide induces autophagy as an early event and then switches over to apoptosis. Nimbolide negatively regulates PI3K/Akt signalling with consequent increase in p-GSK-3βTyr216, the active form of GSK-3β that inhibits autophagy. Downregulation of HOTAIR, a competing endogenous RNA that sponges miR-126 may be a major contributor to the inactivation of PI3K/Akt/GSK3 signalling by nimbolide. Analysis of key markers of apoptosis and autophagy as well as p-AktSer473 during sequential progression of hamster and human OSCC revealed a gradual evolution to a pro-autophagic and antiapoptotic phenotype that could confer a survival advantage to tumors. In summary, the results of the present study provide insights into the molecular mechanisms by which nimbolide augments apoptosis by overcoming the shielding effects of cytoprotective autophagy through modulation of the phosphorylation status of Akt and GSK-3β as well as the ncRNAs miR-126 and HOTAIR. Development of phytochemicals such as nimbolide that target the complex interaction between proteins and ncRNAs that regulate the autophagy/apoptosis flux is of paramount importance in cancer prevention and therapeutics.

Chemical modulation of autophagy as an adjunct to chemotherapy in childhood and adolescent brain tumors

Brain tumors are the leading cause of cancer-related death in children and are the most challenging childhood cancer in relation to diagnosis, treatment, and outcome. One potential novel strategy to improve outcomes in cancer involves the manipulation of autophagy, a fundamental process in all cells. In cancer, autophagy can be thought of as having a "Janus"-like duality. On one face, especially in the early phases of cancer formation, autophagy can act as a cellular housekeeper to eliminate damaged organelles and recycle macromolecules, thus acting as tumor suppressor. On the other face, at later stages of tumor progression, autophagy can function as a pro-survival pathway in response to metabolic stresses such as nutrient depravation, hypoxia and indeed to chemotherapy itself, and can support cell growth by supplying much needed energy. In the context of chemotherapy, autophagy may, in some cases, mediate resistance to treatment. We present an overview of the relevance of autophagy in central nervous system tumors including how its chemical modulation can serve as a useful adjunct to chemotherapy, and use this knowledge to consider how targeting of autophagy may be relevant in pediatric brain tumors.

Mechanism of HN‑3 cell apoptosis induced by carboplatin: Combination of mitochondrial pathway associated with Ca2+ and the nucleus pathways

Laryngeal carcinomas have been recognized as a serious health threat worldwide. In the present study, the mechanism of apoptosis in HN-3 cells induced by carboplatin (CBCDA), a widely used anti-cancer drug, was investigated. The pro-apoptotic effect of CBCDA in HN-3 cells was demonstrated to be time- and dose-dependent. Therefore, the stages of apoptosis were investigated in chronological order. The results demonstrated that excessive generation of cytosolic Ca²⁺ in HN-3 cells was initially triggered when cells were exposed to CBCDA, followed by the appearance of mitochondrial depolarization and oxidative stress, leading to the release of apoptosis-inducing factor. At later stages, expression of caspase-8 was increased due to the apoptotic signals originating from CBCDA-induced DNA damage, as well as caspase-9 and poly ADP ribose polymerase (PARP) expression upregulation. Glutathione decreased the available CBDCA concentration, decreased apoptosis and alleviating oxidative stress, thus reducing the actual effective concentration. Mechanistic research may benefit the rational design of more efficient therapeutic strategies as well as development of novel platinum-based agents.

Oxidative stress-modulating drugs have preferential anticancer effects - involving the regulation of apoptosis, DNA damage, endoplasmic reticulum stress, autophagy, metabolism, and migration

To achieve preferential effects against cancer cells but less damage to normal cells is one of the main challenges of cancer research. In this review, we explore the roles and relationships of oxidative stress-mediated apoptosis, DNA damage, ER stress, autophagy, metabolism, and migration of ROS-modulating anticancer drugs. Understanding preferential anticancer effects in more detail will improve chemotherapeutic approaches that are based on ROS-modulating drugs in cancer treatments.

Induction of Apoptosis in Human Papillary-Thyroid-Carcinoma BCPAP Cells by Diallyl Trisulfide through Activation of the MAPK Signaling Pathway

This study aimed to elucidate the potential effects of diallyl trisulfide (DATS) on human papillary-thyroid-carcinoma BCPAP cells and its underlying mechanisms. DATS is an organosulfur compound derived from garlic. In this study, we demonstrated that compared with the solvent control, DATS treatment at concentrations of 5, 10, and 20 μΜ decreased cell survival rates of BCPAP cells to 84.51 ± 2.67, 57.16 ± 1.18, and 41.22 ± 1.19% respectively. DATS also caused cell-cycle arrest at G0/G1 phase, and the proportion of cells arrested in G0/G1 phase rose from 68.8 ± 8.38 to 80.4 ± 8.38%, which eventually resulted in cell apoptosis through a mitochondrial apoptotic pathway in BCPAP cells. Further evidence showed that DATS activated ERK, JNK, and p38, members of the MAPK family. Moreover, ERK and JNK inhibitors partially reversed apoptosis in BCPAP cells induced by DATS treatment. Taken together, our results demonstrated that DATS exerted an apoptosis-inducing effect on papillary-thyroid-cancer cells via activation of the MAPK signaling pathway, which shed light on a prospective therapeutic target for thyroid-cancer treatment.

Expression and genetic polymorphism of necroptosis related protein RIPK1 is correlated with severe hepatic ischemia-reperfusion injury and prognosis after hepatectomy in hepatocellular carcinoma patients

OBJECTIVES

The goal of our study was to assess the prognostic impact of the necroptosis relative protein RIPK1 genetic polymorphism in ischemia-reperfusion injury and survival after hepatectomy in hepatocellular carcinoma (HCC) patients.

METHODS

In this study, expression of RIPK1 and its genetic polymorphism(rs2272990) were examined in plasma of 44 HCC patients. All these patients were undergoing partial hepatectomy. The prognostic values of RIPK1 genetic polymorphism for tumor development and survival, and ischemia-reperfusion injury after hepatectomy were further determined.

RESULTS

Plasma RIPK1 expressions were significantly increased in HCC patients, compared to the healthy control group. Totally 19 patients have the GA + AA genotype in the RIPK1 rs2272990 SNP site and 25 have GG genotype. There were no statistically significant intergroup differences observed in age, gender, AFP value, HBV positive, tumor size or cirrhosis. GG genotype had positive correlation with TNM classification (p= 0.033) and lymphatic metastasis (p= 0.027) and was significantly associated with severe hepatic ischemia-reperfusion injury and decreased survival rate after hepatectomy.

CONCLUSION

In conclusion, the RIPK1 polymorphism is an indicator of hepatic injury and a novel prognostic biomarker for tumor development and survival of HCC recipients after hepatectomy.

Non-immunosuppressive triazole-based small molecule induces anticancer activity against human hormone-refractory prostate cancers: the role in inhibition of PI3K/AKT/mTOR and c-Myc signaling pathways

A series of triazole-based small molecules that mimic FTY720-mediated anticancer activity but minimize its immunosuppressive effect have been produced. SPS-7 is the most effective derivative displaying higher activity than FTY720 in anti-proliferation against human hormone-refractory prostate cancer (HRPC). It induced G1 arrest of cell cycle and subsequent apoptosis in thymidine block-mediated synchronization model. The data were supported by a decrease of cyclin D1 expression, a dramatic increase of p21 expression and an associated decrease in RB phosphorylation. c-Myc overexpression replenished protein levels of cyclin D1 indicating that c-Myc was responsible for cell cycle regulation. PI3K/Akt/mTOR signaling pathways through p70S6K- and 4EBP1-mediated translational regulation are critical to cell proliferation and survival. SPS-7 significantly inhibited this translational pathway. Overexpression of Myr-Akt (constitutively active Akt) completely abolished SPS-7-induced inhibitory effect on mTOR/p70S6K/4EBP1 signaling and c-Myc protein expression, suggesting that PI3K/Akt serves as a key upstream regulator. SPS-7 also demonstrated substantial anti-tumor efficacy in an in vivo xenograft study using PC-3 mouse model. Notably, FTY720 but not SPS-7 induced a significant immunosuppressive effect as evidenced by depletion of marginal zone B cells, down-regulation of sphingosine-1-phosphate receptors and a decrease in peripheral blood lymphocytes. In conclusion, the data suggest that SPS-7 is not an immunosuppressant while induces anticancer effect against HRPC through inhibition of Akt/mTOR/p70S6K pathwaysthat down-regulate protein levels of both c-Myc and cyclin D1, leading to G1 arrest of cell cycle and subsequent apoptosis. The data also indicate the potential of SPS-7 since PI3K/Akt signalingis responsive for the genomic alterations in prostate cancer.

MSP-4, an Antimicrobial Peptide, Induces Apoptosis via Activation of Extrinsic Fas/FasL- and Intrinsic Mitochondria-Mediated Pathways in One Osteosarcoma Cell Line

Osteosarcoma (OS) is a common malignant bone cancer. The relatively high density of a person's bone structure means low permeability for drugs, and so finding drugs that can be more effective is important and should not be delayed. MSPs are marine antimicrobial peptides (AMP) and natural compounds extracted from Nile tilapia (Oreochromis niloticus). MSP-4 is a part of the AMPs series, with the advantage of having a molecular weight of about 2.7-kDa and anticancer effects, although the responsible anticancer mechanism is not very clear. The goal of this study is to determine the workings of the mechanism associated with apoptosis resulting from MSP-4 in osteosarcoma MG63 cells. The study showed that MSP-4 significantly induced apoptosis in MG63 cells, with Western blot indicating that MSP-4 induced this apoptosis through an intrinsic pathway and an extrinsic pathway. Thus, a pretreatment system with a particular inhibitor of Z-IETD-FMK (caspase-8 inhibitor) and Z-LEHD-FMK (caspase-9 inhibitor) significantly attenuated the cleavage of caspase-3 and prevented apoptosis. These observations indicate that low concentrations of MSP-4 can help induce the apoptosis of MG63 through a Fas/FasL- and mitochondria-mediated pathway and suggest a potentially innovative alternative to the treatment of human osteosarcoma.

TNFR/TNF-α signaling pathway regulates apoptosis of alveolar macrophages in coal workers' pneumoconiosis

We explored the role of TNFR/TNF-α signalingin apoptosis among alveolar macrophages (AM) and its relevance to the development of coal workers' pneumoconiosis (CWP). Purified alveolar macrophages (AMs) were prepared from bronchoalveolar lavage fluid harvested from 366 CWP patients and 120 healthy subjects enrolled inthe study. The purified AMs were then divided into control, SOD, anti-TNFR, TNFR and NFkB inhibitor groups and analyzed for apoptosis usingflow cytometry (sub-diploid peak) and western blotting (Bcl-2, Caspase-3 and Caspase-8 expression). We found thatAM apoptosis washigher amongCWP patients than thehealthycontrols. Expression ofBcl-2, Caspase-3 and Caspase-8 was higher inAMs from CWP patientsthan in those from the controlsand correlated with increased AM apoptosis. Univariate and multivariate analyses suggested that CWP grade, initial exposure time, exposure time inyears, and CWP onset agewereall associated with altered levels of Bcl-2, Caspase-3 and Caspase-8. Inhibition of TNFR/TNF-α signaling usinganti-TNFR antibody, SOD or NFkB inhibitionreduced AM apoptosisand decreased Bcl-2, Caspase-3 and Caspase-8 expression. These data suggestinhibition of a TNFR/TNF-α signaling pathway is a potentiallyeffective means ofalleviating CWP by inhibiting AM apoptosis.

Quantitative assessment of cell fate decision between autophagy and apoptosis

Autophagy and apoptosis are cellular processes that regulate cell survival and death, the former by eliminating dysfunctional components in the cell, the latter by programmed cell death. Stress signals can induce either process, and it is unclear how cells 'assess' cellular damage and make a 'life' or 'death' decision upon activating autophagy or apoptosis. A computational model of coupled apoptosis and autophagy is built here to analyze the underlying signaling and regulatory network dynamics. The model explains the experimentally observed differential deployment of autophagy and apoptosis in response to various stress signals. Autophagic response dominates at low-to-moderate stress; whereas the response shifts from autophagy (graded activation) to apoptosis (switch-like activation) with increasing stress intensity. The model reveals that cytoplasmic Ca²⁺ acts as a rheostat that fine-tunes autophagic and apoptotic responses. A G-protein signaling-mediated feedback loop maintains cytoplasmic Ca²⁺ level, which in turn governs autophagic response through an AMP-activated protein kinase (AMPK)-mediated feedforward loop. Ca²⁺/calmodulin-dependent kinase kinase β (CaMKKβ) emerges as a determinant of the competing roles of cytoplasmic Ca²⁺ in autophagy regulation. The study demonstrates that the proposed model can be advantageously used for interrogating cell regulation events and developing pharmacological strategies for modulating cell decisions.

Inhibition of autophagy potentiates anticancer property of 20(S)-ginsenoside Rh2 by promoting mitochondria-dependent apoptosis in human acute lymphoblastic leukaemia cells

Acute lymphoblastic leukaemia (ALL) is the most prevalent childhood malignancy. Although most children with ALL are cured, there is still a group of patients for which therapy fails owing to severe toxicities and drug resistance. Ginsenoside Rh2 (GRh2), a major bioactive component isolated from Panax ginseng, has been shown to have a therapeutic effect on some tumors. However, the molecular mechanisms of cell death induced by 20(S)-GRh2 in ALL cells remains unclear. In this study, we showed that 20(S)-GRh2 inhibited the cell growth and induced mitochondria-dependent apoptosis and autophagy. But it has no cytotoxic effect on human normal blood cells. Furthermore, autophagy plays a protective role in 20(S)-GRh2-induced apoptosis in ALL cell lines and human primary ALL cells. We demonstrated that either genetic or pharmacologic inhibition of autophagy could be more effective in reducing viability and enhancing 20(S)-GRh2-induced toxicity than 20(S)-GRh2 treatment alone. In addition, inhibition of autophagy could aggravate mitochondrial ROS generation and mitochondrial damage, and then accelerate mitochondria-dependent apoptosis. Taken together, these results suggest that inhibition of autophagy can sensitize ALL cells towards 20(S)-GRh2. The appropriate inhibition of autophagy could provide a powerful strategy to increase the potency of 20(S)-GRh2 as a novel anticancer agent for ALL therapy.

A novel multikinase inhibitor R8 exhibits potent inhibition on cancer cells through both apoptosis and autophagic cell death

Chemotherapy is an important treatment for cancer patients, especially for those with unresectable lesions. Targeted therapy of cancer by specific inhibition of aberrant tyrosine kinase activities in cancer cells with chemically synthesized tyrosine kinase inhibitors (TKIs), shows better responses while less side effects than traditional chemotherapeutic drugs. It is common that cancer cells often exhibit deregulation of several tyrosine kinases simultaneously, multikinase TKIs (MKIs) therefore have greater advantages over single-target TKIs. Currently more MKIs are under developing for better efficacy for different types of cancer. In the present work, we evaluated the in vitro therapeutic potential of a novel MKI, namely R8, with comparison to the clinically available MKI Sunitinib. Results showed that R8 has stronger inhibition on six different types of cancer cell lines with lower IC₅₀ than Sunitinib does. Cell cycle analysis showed that R8 induced significant G0/G1 arrest phase of lung cancer A549 and NCI-H226 cells. The inhibition was also confirmed by colony formation and migration assays in both lung cancer cell lines in a dose-dependent manner. R8 could significantly inhibit the phosphorylation of multiple receptor tyrosine kinases (RTKs) included PDGFRβ, VEGFR2, EGFR and C-Kit, leading to the down-regulation of PI3K-Akt-mTOR signaling. Further analysis revealed that R8 treatment induced more significant apoptosis than Sunitinib did, which might be the consequence of the autophagic cell death. In conclusion, this work suggested R8 to be a promising novel anticancer MKI, and provided the basis for further in vivo investigation on its potential in treatment of lung cancer.

Mitochondrial dysfunction is responsible for fatty acid synthase inhibition-induced apoptosis in breast cancer cells by PdpaMn

Targeting cellular metabolism is becoming a hallmark to overcome drug resistance in breast cancer treatment. Activation of fatty acid synthase (FASN) has been shown to promote breast cancer cell growth. However, there is no concrete report underlying the mechanism associated with mitochondrial dysfunction in relation to fatty acid synthase inhibition-induced apoptosis in breast cancer cells. The current study is aimed at exploring the effect of the novel manganese (Mn) complex, labeled as PdpaMn, on lipid metabolism and mitochondrial function in breast cancer cells. Herein, we observed that PdpaMn displayed strong cytotoxicity on breast cancer cell lines and selectively targeted the tumor without affecting the normal organs or cells in vivo. We also observed that PdpaMn could bind to TE domain of FASN and decrease the activity and the level of expression of FASN, which is an indication that FASN could serve as a target of PdpaMn. In addition, we demonstrated that PdpaMn increased intrinsic apoptosis in breast cancer cells relayed by a suppressed the level of expression of FASN, followed by the release of mitochondrial cytochrome c and the activation of caspases-9. Instigated by the above observations, we hypothesized that PdpaMn-induced apoptosis events are dependent on mitochondrial dysfunction. Indeed, we found that mitochondrial membrane potential (MMP) collapse, mitochondrial oxygen consumption reduction and adenosine triphosphate (ATP) release were deeply repressed. Furthermore, our results showed that PdpaMn significantly increased the reactive oxygen species (ROS) production, and the protection conferred by the free radical scavenger N-acetyl-cysteine (NAC) indicates that PdpaMn-induced apoptosis through an oxidative stress-associated mechanism. More so, the above results have demonstrated that mitochondrial dysfunction participated in FASN inhibition-induce apoptosis in breast cancer cells by PdpaMn. Therefore, PdpaMn may be considered as a good candidate for anti-breast cancer therapeutic option.

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.

Selective cytotoxicity of vanadium complexes on human pancreatic ductal adenocarcinoma cell line by inducing necroptosis, apoptosis and mitotic catastrophe process

The pancreatic cancer is the fourth leading cause of cancer-related death and characterized by one of the lowest five-year survival rate. The current therapeutic options are demonstrating minimal effectiveness, therefore studies on new potential anticancer compounds, with non-significant side effects are highly desirable. Recently, it was demonstrated that vanadium compounds, in particular organic derivatives, exhibit anticancer properties against different type of tumor as well as favorable biodistribution from a pancreatic cancer treatment perspective. In this research, we showed selective cytotoxic effect of vanadium complexes, containing phenanthroline and quinoline as an organic ligands, against human pancreatic ductal adenocarcinoma cell line (PANC-1), compared to non-tumor human immortalized pancreas duct epithelial cells (hTERT-HPNE). Results exhibited that vanadium complexes inhibited autophagy process in selective cytotoxic concentration as well as caused the cell cycle arrest in G2/M phase associated with mitotic catastrophe and increased level of reactive oxygen species (ROS). Moreover, in higher concentration, vanadium derivatives induced a mix type of cell death in PANC-1 cells, including apoptotic and necroptotic process. Our investigation emphasizes the anticancer potential of vanadium complexes by indicating their selective cytotoxic activity, through different process posed by alternative type of cell deaths to apoptosis-resistant cancer cells. Further studies supporting the therapeutic potential of vanadium in pancreatic cancer treatment is highly recommended.

The autophagic inhibition oral squamous cell carcinoma cancer growth of 16-hydroxy-cleroda-3,14-dine-15,16-olide

16-hydroxycleroda-3, 13-dine-15, 16-olide (HCD) isolated from Polyalthia longifolia possesses numerous biological activities. Previous studies have reported that HCD can block phosphorylation activity of cancer cells to inhibit tumor cell growth, but the anti-tumor activity in oral squamous cell carcinoma is unrevealed. This study investigates the inhibiting effect of HCD on human OSCC cell growth; thereby, developing a new oral cancer drug. In in vitro cultured human OSCC cells (OECM1 and SAS) were employed to test the inhibitory growth of HCD via cell cytotoxic effect using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, Western blotting, and further determining of the inhibitory efficacy of tumor growth by a xenograft tumor on BALB/c male nude mice (in vivo test). Under various concentrations of HCD and time course treatments were shown to effectively cause cell death and cell-cycle arrest in OECM1 and SAS cells, which was confirmed via a clinical drug (cisplatin) as a positive control. In addition, HCD induced the autophagic cell death in OECM1 and SAS cells by LC3-mediated LC3-I/LC3-II/p62 pathway at the in vitro level. An in vivo assay indicated that HCD could treat oral cancer by deferring tumor growth. These findings provide a favorable assessment for further elucidating the role of HCD that targets autophagic cell death pathways as a potential agent for cancer therapy.

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.

An Isoquinolin-1(2H)-Imine Derivative Induces Cell Death via Generation of Reactive Oxygen Species and Activation of JNK in Human A549 Cancer Cells

Compound 11-benzoyl-10-chloro-7,9-difluoro-6-imino-2,3,4,6-tetrahydro-1H-pyrimido[1,2-b]isoquinoline-8-carbonitrile (HC6h) is a novel polyhalo 1,3-diazaheterocycle fused isoquinolin-1(2H)-imines derivative, which displays good anticancer activity and low toxicity in vivo. However, the underlying anticancer mechanisms have not previously been identified. The proliferation of A549 was assessed by MTT assay. The reactive oxygen species (ROS) level was assessed in A549 with a H₂ DCFDA probe. Mitochondrial membrane potential was measured using the JC-1 staining. Apoptosis were measured by annexin-V/PI assay and autophagy by acridine orange staining and GFP-LC3 fluorescence assay. The expression of autophagic and apoptotic proteins was determined by Western blot. The compound HC6h increased accumulation of vesicles, acridine orange-stained cells and LC3-II in A549 cells. Inhibition of compound HC6h-induced autophagy by bafilomycin A1 increased apoptosis. Compound HC6h enhanced activation of caspase-3, caspase-9 and PARP cleavage in A549 cells. Compound HC6h leads to the rapid generation of intracellular ROS. Moreover, compound HC6h induced phosphorylation of JNK and was conferred by the increased ROS levels. Furthermore, down-regulation of JNK attenuated autophagic and apoptotic effect in response to HC6h. The induction of ROS upon HC6h treatment leads to the activation of JNK that mediates autophagy and apoptosis in human A549 cancer cells. J. Cell. Biochem. 118: 4394-4403, 2017. © 2017 Wiley Periodicals, Inc.

Role of Methylation in the Regulation of Apoptosis Genes APAF1, DAPK1, and BCL2 in Breast Cancer

Changes in the levels of expression of proapoptotic genes APAF1 and DAPK1 and antiapoptotic gene BCL2 were studied by real time PCR in specimens of tumors and histologically intact tissue from 28 patients with breast cancer. The expression of APAF1 and DAPK1 was below the normal in the majority of tumor samples (p<0.05), while the level of BCL2 mRNA more often surpassed the normal (p<0.1). Study of the same sample of specimens by methylspecific PCR showed predominance of APAF1 and DAPK1 hypermethylation (p<0.05 and p<0.1, respectively) and more frequent hypomethylation of BCL2. A significant correlation between changes in the levels of expression and methylation (r=0.40-0.49; p<0.05) was detected for all three genes (APAF1, DAPK1, and BCL2). The results suggest that methylation play an important role in the regulation of these apoptosis system genes in breast cancer.

Staurosporine suppresses survival of HepG2 cancer cells through Omi/HtrA2-mediated inhibition of PI3K/Akt signaling pathway

Staurosporine, which is an inhibitor of a broad spectrum of protein kinases, has shown cytotoxicity on several human cancer cells. However, the underlying mechanism is not well understood. In this study, we examined whether and how this compound has an inhibitory action on phosphatidylinositol 3-kinase (PI3K)/Akt pathway in vitro using HepG2 human hepatocellular carcinoma cell line. Cell viability and apoptosis were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and terminal deoxyribonucleotidyl transferase–mediated dUTP-digoxigenin nick end labeling (TUNEL) assay, respectively. Glutathione S-transferase (GST) pull-down assay and co-immunoprecipitation were performed to detect protein–protein interactions. Small interfering RNA (siRNA) was used to silence the expression of targeted protein. We found that staurosporine significantly decreased cell viability and increased cell apoptosis in a concentration- and time-dependent manner in HepG2 cancer cells, along with the decreased expressions of PDK1 protein and Akt phosphorylation. Staurosporine was also found to enhance Omi/HtrA2 release from mitochondria. Furthermore, Omi/HtrA2 directly bound to PDK1. Pharmacological and genetic inhibition of Omi/HtrA2 restored protein levels of PDK1 and protected HepG2 cancer cells from staurosporine-induced cell death. In addition, staurosporine was found to activate autophagy. However, inhibition of autophagy exacerbated cell death under concomitant treatment with staurosporine. Taken together, our results indicate that staurosporine induced cytotoxicity response by inhibiting PI3K/Akt signaling pathway through Omi/HtrA2-mediated PDK1 degradation, and the process provides a novel mechanism by which staurosporine produces its therapeutic effects.

Necroptosis: Modules and molecular switches with therapeutic implications

Among the various programmed cell death (PCD) pathways, "Necroptosis" has gained much importance as a novel paradigm of cell death. This pathway has emerged as a backup mechanism when physiologically conserved PCD (apoptosis) is non-functional either genetically or pathogenically. The expanding spectrum of necroptosis from physiological development to diverse patho-physiological disorders, including xenobiotics-mediated toxicity has now grabbed the attention worldwide. The efficient role of necroptosis regulators in disease development and management are under constant examination. In fact, few regulators (e.g. MLKL) have already paved their way towards clinical trials and others are in queue. In this review, emphasis has been paid to the various contributing factors and molecular switches that can regulate necroptosis. Here we linked the overview of current knowledge of this enigmatic signaling with magnitude of therapeutics that may underpin the opportunities for novel therapeutic approaches to suppress the pathogenesis of necroptosis-driven disorders.

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.

Gastrointestinal stromal tumors (GIST): Facing cell death between autophagy and apoptosis

Autophagy and apoptosis are 2 fundamental biological mechanisms that may cooperate or be antagonistic, although both are involved in deciding the fate of cells in physiological or pathological conditions. These 2 mechanisms coexist simultaneously in cells and share common upstream signals and stimuli. Autophagy and apoptosis play pivotal roles in cancer development. Autophagy plays a key function in maintaining tumor cell survival by providing energy during unfavorable metabolic conditions through its recycling mechanism, and supporting the high energy requirement for metabolism and growth. This review focuses on gastrointestinal stromal tumors and cell death through autophagy and apoptosis, taking into account the involvement of both of these processes in tumor development and growth and as mechanisms of drug resistance. We also focus on the crosstalk between autophagy and apoptosis as an emerging field with major implications for the development of novel therapeutic options.

The Detection Techniques for Autophagy-Associated Cell Death-Related Genes and Proteins: Gene Expression Assay and Immunohistochemistry

Autophagy is important in cellular homeostasis for the cell survival mechanism. Deficiency or excess of autophagy is generally related to some of diseases such as cancer and neurodegeneration. Although autophagy is a cell survival mechanism, it can mediate programmed cell death in several conditions. Autophagy-related genes (ATGs) regulate the autophagy and also control the crosstalk with autophagy-associated cell death and apoptosis in some condition. Various methods have been used to detect the marker genes and the proteins involved in these processes. Quantitative real-time PCR (qRT-PCR) method for monitoring the expression of genes involved in autophagy or autophagic cell death is often preferred because of its sensitivity, high efficiency potential, accurate quantification, and high-grade potential automation. The detection of the markers for autophagy-related process by immunohistochemistry in paraffin sections of various patient tissues has become a reliable method for monitoring autophagy. Here, we introduce protocols for detecting autophagy and autophagy-associated cell death in HeLa cells by using gene expression assays qRT-PCR, and also in paraffin-embedded tissue section from human biopsy material by using immunohistochemistry.

ΔN-Bcl-xL, a therapeutic target for neuroprotection

The B-cell lymphoma-extra large (Bcl-xL) is a mitochondrial anti-apoptotic protein that plays a role in neuroprotection. However, during excitotoxic stimulation, Bcl-xL undergoes caspase-dependent cleavage and produces a fragmented form, ΔN-Bcl-xL. Accumulation of ΔN-Bcl-xL is associated with mitochondrial dysfunction and neuronal death. Therefore, strategies to inhibit the activity or formation of ΔN-Bcl-xL protect the brain against excitotoxic injuries. Our team found that the pharmacological inhibitor ABT-737 exerts dose dependent effects in primary neurons. When primary hippocampal neurons were treated with 1 μM ABT-737, glutamate-mediated mitochondrial damage and neuronal death were exacerbated, whereas 10 nM ABT-737, a 100-fold lower concentration, protected mitochondrial function and enhanced neuronal viability against glutamate toxicity. In addition, we suggested acute vs. prolonged formation of ΔN-Bcl-xL may have different effects on mitochondrial or neuronal functions. Unlike acute production of ΔN-Bcl-xL by glutamate, overexpression of ΔN-Bcl-xL did not cause drastic changes in neuronal viability. We predicted that neurons undergo adaptation and may activate altered metabolism to compensate for ΔN-Bcl-xL-mediated mitochondrial dysfunction. Although the detailed mechanism of ABT-mediated neurotoxicity neuroprotection is still unclear, our study shows that the mitochondrial membrane protein ΔN-Bcl-xL is a central target for interventions.