Brefeldin A reduces anchorage-independent survival, cancer stem cell potential and migration of MDA-MB-231 human breast cancer cells

Golgi dispersal in cancer stem cells promotes chemoresistance of colorectal cancer via the Golgi stress response

Chemotherapy is a crucial treatment for colorectal tumors. However, its efficacy is restricted by chemoresistance. Recently, Golgi dispersal has been suggested to be a potential response to chemotherapy, particularly to drugs that induce DNA damage. However, the underlying mechanisms by which Golgi dispersal enhances the capacity to resist DNA-damaging agents remain unclear. Here, we demonstrated that DNA-damaging agents triggered Golgi dispersal in colorectal cancer (CRC), and cancer stem cells (CSCs) possessed a greater degree of Golgi dispersal compared with differentiated cancer cells (non-CSCs). We further revealed that Golgi dispersal conferred resistance against the lethal effects of DNA-damaging agents. Momentously, Golgi dispersal activated the Golgi stress response via the PKCα/GSK3α/TFE3 axis, resulting in enhanced protein and vesicle trafficking, which facilitated drug efflux through ABCG2. Identification of Golgi dispersal indicated an unexpected pathway regulating chemoresistance in CRC.

Protein homeostasis maintained by HOOK1 levels promotes the tumorigenic and stemness properties of ovarian cancer cells through reticulum stress and autophagy

BACKGROUND

Ovarian cancer has a high mortality rate mainly due to its resistance to currently used therapies. This resistance has been associated with the presence of cancer stem cells (CSCs), interactions with the microenvironment, and intratumoral heterogeneity. Therefore, the search for new therapeutic targets, particularly those targeting CSCs, is important for improving patient prognosis. HOOK1 has been found to be transcriptionally altered in a substantial percentage of ovarian tumors, but its role in tumor initiation and development is still not fully understood.

METHODS

The downregulation of HOOK1 was performed in ovarian cancer cell lines using CRISPR/Cas9 technology, followed by growth in vitro and in vivo assays. Subsequently, migration (Boyden chamber), cell death (Western-Blot and flow cytometry) and stemness properties (clonal heterogeneity analysis, tumorspheres assay and flow cytometry) of the downregulated cell lines were analysed. To gain insights into the specific mechanisms of action of HOOK1 in ovarian cancer, a proteomic analysis was performed, followed by Western-blot and cytotoxicity assays to confirm the results found within the mass spectrometry. Immunofluorescence staining, Western-blotting and flow cytometry were also employed to finish uncovering the role of HOOK1 in ovarian cancer.

RESULTS

In this study, we observed that reducing the levels of HOOK1 in ovarian cancer cells reduced in vitro growth and migration and prevented tumor formation in vivo. Furthermore, HOOK1 reduction led to a decrease in stem-like capabilities in these cells, which, however, did not seem related to the expression of genes traditionally associated with this phenotype. A proteome study, along with other analysis, showed that the downregulation of HOOK1 also induced an increase in endoplasmic reticulum stress levels in these cells. Finally, the decrease in stem-like properties observed in cells with downregulated HOOK1 could be explained by an increase in cell death in the CSC population within the culture due to endoplasmic reticulum stress by the unfolded protein response.

CONCLUSION

HOOK1 contributes to maintaining the tumorigenic and stemness properties of ovarian cancer cells by preserving protein homeostasis and could be considered an alternative therapeutic target, especially in combination with inducers of endoplasmic reticulum or proteotoxic stress such as proteasome inhibitors.

Predicting drug response through tumor deconvolution by cancer cell lines

Large-scale cancer drug sensitivity data have become available for a collection of cancer cell lines, but only limited drug response data from patients are available. Bridging the gap in pharmacogenomics knowledge between in vitro and in vivo datasets remains challenging. In this study, we trained a deep learning model, Scaden-CA, for deconvoluting tumor data into proportions of cancer-type-specific cell lines. Then, we developed a drug response prediction method using the deconvoluted proportions and the drug sensitivity data from cell lines. The Scaden-CA model showed excellent performance in terms of concordance correlation coefficients (>0.9 for model testing) and the correctly deconvoluted rate (>70% across most cancers) for model validation using Cancer Cell Line Encyclopedia (CCLE) bulk RNA data. We applied the model to tumors in The Cancer Genome Atlas (TCGA) dataset and examined associations between predicted cell viability and mutation status or gene expression levels to understand underlying mechanisms of potential value for drug repurposing.

Salinomycin disturbs Golgi function and specifically affects cells in epithelial-to-mesenchymal transition

Epithelial-to-mesenchymal transition (EMT) gives rise to cells with properties similar to cancer stem cells (CSCs). Targeting the EMT program to selectively eliminate CSCs is a promising way to improve cancer therapy. Salinomycin (Sal), a K+/H+ ionophore, was identified as highly selective towards CSC-like cells, but its mechanism of action and selectivity remains elusive. Here, we show that Sal, similar to monensin and nigericin, disturbs the function of the Golgi. Sal alters the expression of Golgi-related genes and leads to marked changes in Golgi morphology, particularly in cells that have undergone EMT. Moreover, Golgi-disturbing agents severely affect post-translational modifications of proteins, including protein processing, glycosylation and secretion. We discover that the alterations induced by Golgi-disturbing agents specifically affect the viability of EMT cells. Collectively, our work reveals a novel vulnerability related to the EMT, suggesting an important role for the Golgi in the EMT and that targeting the Golgi could represent a novel therapeutic approach against CSCs.

Emerging roles of endoplasmic reticulum stress in the cellular plasticity of cancer cells

Cellular plasticity is a well-known dynamic feature of tumor cells that endows tumors with heterogeneity and therapeutic resistance and alters their invasion-metastasis progression, stemness, and drug sensitivity, thereby posing a major challenge to cancer therapy. It is becoming increasingly clear that endoplasmic reticulum (ER) stress is a hallmark of cancer. The dysregulated expression of ER stress sensors and the activation of downstream signaling pathways play a role in the regulation of tumor progression and cellular response to various challenges. Moreover, mounting evidence implicates ER stress in the regulation of cancer cell plasticity, including epithelial-mesenchymal plasticity, drug resistance phenotype, cancer stem cell phenotype, and vasculogenic mimicry phenotype plasticity. ER stress influences several malignant characteristics of tumor cells, including epithelial-to-mesenchymal transition (EMT), stem cell maintenance, angiogenic function, and tumor cell sensitivity to targeted therapy. The emerging links between ER stress and cancer cell plasticity that are implicated in tumor progression and chemoresistance are discussed in this review, which may aid in formulating strategies to target ER stress and cancer cell plasticity in anticancer treatments.

Novel Thieno [2,3-b]pyridine Anticancer Compound Lowers Cancer Stem Cell Fraction Inducing Shift of Lipid to Glucose Metabolism

Due to the role of cancer stem cells (CSCs) in tumor resistance and glycosphingolipid (GSL) involvement in tumor pathogenesis, we investigated the effect of a newly synthesized compound (3-amino-N-(3-chloro-2-methylphenyl)-5-oxo-5,6,7,8-tetrahydrothieno[2,3-b]quinoline-2-carboxamide 1 on the percentage of CSCs and the expression of six GSLs on CSCs and non-CSCs on breast cancer cell lines (MDA-MB-231 and MCF-7). We also investigated the effect of 1 on the metabolic profile of these cell lines. The MTT assay was used for cytotoxicity determination. Apoptosis and expression of GSLs were assessed by flow cytometry. A GC–MS-coupled system was used for the separation and identification of metabolites. Compound 1 was cytotoxic for both cell lines, and the majority of cells died by treatment-induced apoptosis. The percentage of CSCs was significantly lower in the MDA-MB-231 cell line. Treatment with 1 caused a decrease of CSC IV⁶Neu₅Ac-nLc₄Cer+ MDA-MB-231 cells. In the MCF-7 cell line, the percentage of GalNAc-GM1b+ CSCs was increased, while the expression of Gg₃Cer was decreased in both CSC and non-CSC. Twenty-one metabolites were identified by metabolic profiling. The major impact of the treatment was in glycolysis/gluconeogenesis, pyruvate and inositol metabolism. Compound 1 exhibited higher potency in MBA-MB-231 cells, and it deserves further examination.

Natural Products as a Promising Therapeutic Strategy to Target Cancer Stem Cells

Cancer is still a deadly disease, and its treatment desperately needs to be managed in a very sophisticated way through fast-developing novel strategies. Most of the cancer cases eventually develop into recurrencies, for which cancer stem cells (CSCs) are thought to be responsible. They are considered as a subpopulation of all cancer cells of tumor tissue with aberrant regulation of self-renewal, unbalanced proliferation, and cell death properties. Moreover, CSCs show a serious degree of resistance to chemotherapy or radiotherapy and immune surveillance as well. Therefore, new classes of drugs are rushing into the market each year, which makes the cost of therapy increase dramatically. Natural products are also becoming a new research area as a diverse chemical library to suppress CSCs. Some of the products even show promise in this regard. So, the near future could witness the introduction of natural products as a source of new chemotherapy modalities, which may result in the development of novel anticancer drugs. They could also be a reasonably-priced alternative to highly expensive current treatments. Nowadays, considering the effects of natural compounds on targeting surface markers, signaling pathways, apoptosis, and escape from immunosurveillance have been a highly intriguing area in preclinical and clinical research. In this review, we present scientific advances regarding their potential use in the inhibition of CSCs and the mechanisms by which they kill the CSCs.

Brefeldin A Induces Apoptosis, Inhibits BCR-ABL Activation, and Triggers BCR-ABL Degradation in Chronic Myeloid Leukemia K562 Cells

BACKGROUND

Chronic myeloid leukemia (CML) is a myeloproliferative disease caused by BCR-ABL oncoprotein. Tyrosine kinase inhibitors have been developed to inhibit the activity of BCR-ABL; however, drug resistance and side effect occur in clinic application. Therefore, it is urgent to find novel drugs for CML treatment. Under the guidance of cytotoxic activity, crude extracts of 55 fungal strains from the medicinal mangrove Acanthus ilicifolius were evaluated, and one potent cytotoxic natural compound, brefeldin A (BFA), was discovered from Penicillium sp. (HS-N-29).

OBJECTIVE

This study was aimed to determine the cytotoxic activity of BFA and the effect on the activation and expression of BCR-ABL in K562 cells.

METHOD

We evaluated cytotoxic activity by MTT assay and soft agar clone assay and apoptosis and cell cycle distribution by Muse cell analyzer. The protein level of BCR-ABL and signaling molecules were detected by western blotting, and the mRNA level of BCR-ABL was determined by RT-PCR.

RESULTS

BFA inhibited cell proliferation, induced G2/M cell cycle arrest, and stimulated cell apoptosis in K562 cells. Importantly, for the first time, we revealed that BFA inhibited the activation of BCR-ABL and consequently inhibited the activation of its downstream signaling molecules in K562 cells. Moreover, we found that BFA degraded BCR-ABL without affecting its transcription in K562 cells, and BFA-induced BCR-ABL degradation was related to caspase activation while not to autophagy or ubiquitinated proteasome degradation pathway.

CONCLUSION

Our present results indicate that BFA acts as a dual functional inhibitor and degrader of BCR-ABL, and BFA is a potential compound for chemotherapeutics to overcome CML.

Natural products: A lead for drug discovery and development

Natural products are used since ancient times in folklore for the treatment of various ailments. Plant-derived products have been recognized for many years as a source of therapeutic agents and structural diversity. A literature survey has been carried out to determine the utility of natural molecules and their modified analogs or derivatives as pharmacological active entities. This review presents a study on the importance of natural products in terms of drug discovery and development. It describes how the natural components can be utilized after small modifications in new perspectives. Various new modifications in structure offer a unique opportunity to establish a new molecular entity with better pharmacological potential. It was concluded that in this current era, new attempts are taken to utilize the compounds derived from natural sources as novel drug candidates, with a focus to find and discover new effective molecules that were referred to as "new entities of natural product drug discovery."

ER-to-Golgi Transport in HeLa Cells Displays High Resilience to Ca2+ and Energy Stresses

One third of all human proteins are either transmembrane or soluble secretory proteins that first target the endoplasmic reticulum (ER). These proteins subsequently leave the ER and enter the Golgi apparatus via ER-Golgi intermediate vesicular structures. Live-cell imaging of cargos fused to fluorescent proteins (FPs) enables the high-resolution visualization and characterization of secretory transport processes. Here, we performed fluorescence time-lapse imaging to assess the Ca2+ and energy dependency of ER-to-Golgi transport in living HeLa cells, a cancer cell model which has been well investigated. Our data revealed that ER-to-Golgi transport remained highly efficient in the absence of ATP-generating substrates, despite clear reductions in cytosolic and mitochondrial ATP levels under these energy stress conditions. However, cell treatment with 2-deoxy-D-glucose (2-DG), which severely diminished subcellular ATP levels, abolished ER-to-Golgi transport. Interestingly, while 2-DG elevated cytosolic Ca2+ levels and reduced long-distance movements of glycosylphosphatidylinositol (GPI)-positive vesicles, robust short-term ER Ca2+ mobilizations, which strongly affected the motility of these vesicles, did not considerably impair ER-to-Golgi transport. In summary, we highlight that ER-to-Golgi transport in HeLa cells remains functional despite high energy and Ca2+ stress levels.

Artichoke Polyphenols Sensitize Human Breast Cancer Cells to Chemotherapeutic Drugs via a ROS-Mediated Downregulation of Flap Endonuclease 1

Combined treatment of several natural polyphenols and chemotherapeutic agents is more effective comparing to the drug alone in inhibiting cancer cell growth. Polyphenolic artichoke extracts (AEs) have been shown to have anticancer properties by triggering apoptosis or reactive oxygen species- (ROS-) mediated senescence when used at high or low doses, respectively. Our aim was to explore the chemosensitizing potential of AEs in order to enhance the efficacy of conventional chemotherapy in breast cancer cells. We employed breast cancer cell lines to assess the potential synergistic effect of a combined treatment of AEs/paclitaxel (PTX) or AEs/adriamycin (ADR) and to determine the underlying mechanisms correlated to this potential therapeutic approach. Our data shows that AEs/PTX reduced cell proliferation by increasing DNA damage response (DDR) mediated by Flap endonuclease 1 (FEN1) downregulation that results into enhanced breast cancer cell sensitivity to chemotherapeutic drugs. We demonstrated that ROS/Nrf2 and p-ERK pathways are two molecular mechanisms involved in the synergistic effect of AEs plus PTX treatment. To highlight the role of ROS herein, we report that the addition of antioxidant N-acetylcysteine (NAC) significantly decreased the antiproliferative effect of the combined treatment. A combined therapy could be able to reduce the dose of chemotherapeutic drugs, minimizing toxicity and side effects. Our results suggest the use of artichoke polyphenols as ROS-mediated sensitizers of chemotherapy paving the way for innovative and promising natural compound-based therapeutic strategies in oncology.

PSMD4 regulates the malignancy of esophageal cancer cells by suppressing endoplasmic reticulum stress

Proteasome 26S subunit non-ATPase 4 (PSMD4) is an important proteasome ubiquitin receptor and plays a key role in endoplasmic reticulum stress (ERS). However, the study of PSMD4 in esophageal cancer (EC) is relatively rare. Here, we found that the expression of PSMD4 was markedly enhanced in EC tissues and cell lines. The cell counting kit-8 (CCK-8) assay showed that overexpression of PSMD4 significantly enhanced Eca109 cell viability, while inhibition of PSMD4 reduced Eca109 cell viability. Knockdown of PSMD4 induced Eca109 cell apoptosis and cell cycle arrest. More importantly, knockdown of PSMD4 significantly enhanced the expression of glucose regulated protein 78, activating transcription factor 6, and p-protein kinase R-like ER kinase, indicating an enhanced ERS response in esophageal cancer cells. Compared with the control cells, brefeldin A significantly inhibited the expression of PSMD4 and increased the expression of p53-upregulated modulator of apoptosis. However, such effects were largely reversed after overexpressing PSMD4 in Eca109 cells, suggesting that silencing PSMD4 could enhance ERS-induced cell apoptosis. In summary, upregulation of PSMD4 promoted the progression of esophageal cancer mainly by reducing ERS-induced cell apoptosis.

Brefeldin A impairs porcine oocyte meiotic maturation via interruption of organelle dynamics

Brefeldin A (BFA) is a lactone antibiotic synthesized from palmitic acid by several fungi that could block anterograde transport of proteins from endoplasmic reticulum to Golgi apparatus by reversible disruption of the Golgi complex. Previous investigations have shown that BFA induces the apoptosis of cancer cells in mitosis and impairs asymmetric spindle positioning in meiosis. Here, we document that exposure to BFA in porcine oocytes compromises the meiotic maturation via disrupting both nuclear and cytoplasmic maturation. We found that BFA exposure collapsed the cytoskeleton assembly by showing the aberrant spindle organization with misaligned chromosomes and defective actin dynamics. Furthermore, the distribution of both mitochondria and cortical granules (CGs), two important indexes of cytoplasmic maturation of oocytes, was disturbed following BFA exposure. We finally validated that the localization of ovastacin, a component of CGs that is essential for the postfertilization removal of sperm-binding sites in the zona pellucida, was also perturbed in BFA-exposed oocytes, which might weaken their fertilization capacity. Collectively, these findings indicate that Golgi-mediated protein transport is indispensable for the porcine oocyte meiotic maturation.

The Role of the ER-Induced UPR Pathway and the Efficacy of Its Inhibitors and Inducers in the Inhibition of Tumor Progression

Cancer is the second most frequent cause of death worldwide. It is considered to be one of the most dangerous diseases, and there is still no effective treatment for many types of cancer. Since cancerous cells have a high proliferation rate, it is pivotal for their proper functioning to have the well-functioning protein machinery. Correct protein processing and folding are crucial to maintain tumor homeostasis. Endoplasmic reticulum (ER) stress is one of the leading factors that cause disturbances in these processes. It is induced by impaired function of the ER and accumulation of unfolded proteins. Induction of ER stress affects many molecular pathways that cause the unfolded protein response (UPR). This is the way in which cells can adapt to the new conditions, but when ER stress cannot be resolved, the UPR induces cell death. The molecular mechanisms of this double-edged sword process are involved in the transition of the UPR either in a cell protection mechanism or in apoptosis. However, this process remains poorly understood but seems to be crucial in the treatment of many diseases that are related to ER stress. Hence, understanding the ER stress response, especially in the aspect of pathological consequences of UPR, has the potential to allow us to develop novel therapies and new diagnostic and prognostic markers for cancer.

Brefeldin A inhibits colorectal cancer growth by triggering Bip/Akt-regulated autophagy

Colorectal cancer (CRC) is one of the most prevalent neoplastic diseases worldwide, and effective treatment remains a challenge. Here, we found that the macrolide antibiotic brefeldin A (BFA) exhibits considerable antitumor activity both in vitro and in vivo. Induction of complete autophagic flux is characterized as a key event in BFA-induced CRC suppression. Mechanistically, BFA provokes endoplasmic reticulum stress-mediated binding immunoglobulin protein (Bip) expression, leading to increased Bip/Akt interaction and resultant decreased Akt phosphorylation, thereby activating autophagy. Autophagy inhibition or Bip suppression relieves BFA-induced cell death, suggesting a key role for Bip-regulated autophagy in the antitumor properties of BFA. Moreover, BFA acts synergistically with paclitaxel or 5-fluorouracil in CRC suppression. Collectively, our study provides an important molecular basis for BFA-induced autophagy and suggests that the antibiotic BFA could be repositioned as a potential anticancer drug for CRC treatment.-Zhou, L., Gao, W., Wang, K., Huang, Z., Zhang, L., Zhang, Z., Zhou, J., Nice, E. C., Huang, C. Brefeldin A inhibits colorectal cancer growth by triggering Bip/Akt-regulated autophagy.

Glioma Cell Secretion: A Driver of Tumor Progression and a Potential Therapeutic Target

Cellular secretion is an important mediator of cancer progression. Secreted molecules in glioma are key components of complex autocrine and paracrine pathways that mediate multiple oncogenic pathologies. In this review, we describe tumor cell secretion in high-grade glioma and highlight potential novel therapeutic opportunities. Cancer Res; 78(21); 6031-9. ©2018 AACR.

Anti-Cancer Natural Products and Their Bioactive Compounds Inducing ER Stress-Mediated Apoptosis: A Review

Cancer is the second biggest cause of death worldwide. Despite a number of studies being conducted, the effective mechanism for treating cancer has not yet been fully understood. The tumor-microenvironment such as hypoxia, low nutrients could disturb function of endoplasmic reticulum (ER) to maintain cellular homeostasis, ultimately leading to the accumulation of unfolded proteins in ER, so-called ER stress. The ER stress has a close relation with cancer. ER stress initiates unfolded protein response (UPR) to re-establish ER homeostasis as an adaptive pathway in cancer. However, persistent ER stress triggers the apoptotic pathway. Therefore, blocking the adaptive pathway of ER stress or facilitating the apoptotic pathway could be an anti-cancer strategy. Recently, natural products and their derivatives have been reported to have anti-cancer effects via ER stress. Here, we address mechanisms of ER stress-mediated apoptosis and highlight strategies for cancer therapy by utilizing ER stress. Furthermore, we summarize anti-cancer activity of the natural products via ER stress in six major types of cancers globally (lung, breast, colorectal, gastric, prostate and liver cancer). This review deepens the understanding of ER stress mechanisms in major cancers as well as the suppressive impact of natural products against cancers via ER stress.

Mcl-1 targeting could be an intriguing perspective to cure cancer

The Bcl-2 family, which plays important roles in controlling cancer development, is divided into antiapoptotic and proapoptotic members. The change in the balance between these members governs the life and death of the cells. Mcl-1 is an antiapoptotic member of this family and its distribution in normal and cancerous tissues strongly differs from that of Bcl-2. In human cancers, where upregulation of antiapoptotic proteins is common, Mcl-1 expression is regulated independent of Bcl-2 and its inhibition promotes senescence, a major barrier to tumorigenesis. Cancer chemotherapy determines various kinds of responses, such as senescence and autophagy; however, the ideal response to chemotherapy is apoptosis. Mcl-1 is a potent oncogene that is regulated at the transcriptional, posttranscriptional, and posttranslational levels. Mcl-1 is a short-lived protein that, in the NH2 terminal region, contains sites for posttranslational regulation that can lead to proteasomal degradation. The USP9X Mcl-1 deubiquitinase regulates Mcl-1 and the levels of these two proteins are strongly correlated. Mcl-1 has three splicing variants (the antiapoptotic protein Mcl-1L and the proapoptotic proteins Mcl-1S and Mcl-1ES), each contributing toward apoptosis regulation. In cancers responsible for the most deaths in the world, the presence of Mcl-1 is associated with malignant cell growth and evasion of apoptosis. Mcl-1 is also one of the key regulators of cancer stem cells' self-renewal that contributes to tumor survival. A great number of indirect and selective Mcl-1 inhibitors have been produced and some of these have shown efficacy in several clinical trials. Thus, therapeutic manipulation of Mcl-1 can be a useful strategy to combat cancer.

NEDD9 stimulated MMP9 secretion is required for invadopodia formation in oral squamous cell carcinoma

Neural precursor cell expressed developmentally downregulated 9 (NEDD9) is a component of the metastatic signatures of melanoma, breast cancer, glioblastoma, lung cancer and head and neck squamous cell carcinoma (HNSCC). Here we tested the efficacy of NEDD9's domains in stimulating matrix metalloproteinase (MMP) secretion and invadopodia formation in cells stably expressing various NEDD9 mutants. Replacement of the 13 YxxP motif substrate domain (SD) tyrosines and the C-terminal Y629 with phenylalanines (F14NEDD9) eliminated tyrosine phosphorylation, MMP9 secretion and loss of invadopodia formation. Mutation of the N-terminal SH3 domain Y12 to glutamic acid (Y12ENEDD9) or phenylalanine (Y12FNEDD9) reduced MMP9 secretion and inhibited invadopodia formation. SH3 domain deletion (∆SH3NEDD9) resulted in the loss of MMP9 secretion and a lack of invadopodia formation. The SH3–SD domain (SSNEDD9) construct exhibited tyrosine phosphorylation and stimulated MMP9 secretion, as did ∆CTNEDD9 which lacked the C-terminus (∆C-terminal; ∆CT). E13NEDD9 expression blocked MMP9 secretion and invadopodia formation. MICAL1 (molecule interacting with Cas-L1) silencing with a short hairpin RNA reduced MMP9 secretion, vimentin and E-cadherin levels while increasing N-cadherin and Rab6 levels, consistent with reduced invasive behavior. These findings indicate that NEDD9 SD phosphorylation and SH3 domain interactions are necessary for increasing MMP9 secretion and invadopodia formation.

Lx2-32c inhibits the formation of mammosphere from MDA-MB-231 cells and induces apoptosis involving in down-regulating FoxM1

Cancer stem cells (CSCs) are a subset of cancer cells which have self-renewal ability and exist in various tumors. Inhibition of CSCs self-renewal is considered as a new method for tumor therapy. A novel semi-synthetic taxane analogue, Lx2-32c, could overcome drug resistance in various cancer cell lines. In this study, it was found that Lx2-32c inhibited the proliferation and mammosphere formation of MDA-MB-231-derived cancer stem cell-like cells (MCSCLCs) and induced apoptosis, as well as down-regulated the expression of FoxM1 and CD44 in MCSCLCs. Simultaneously, it was proved that Lx2-32c combined with thiostreption, a FoxM1 inhibitor inhibited proliferation and mammosphere formation of MCSCLCs and induced apoptosis to a more extent than Lx2-32c alone; thiostreption could also enhance the effect of Lx2-32c of reduction of the expression of FoxM1 and CD44. All of these results indicated that Lx2-32c is a novel semi-synthetic taxane analogue which inhibits the self-renewal of MCSCLCs cells and induces apoptosis involving in down-regulating FoxM1.

Functional disruption of the Golgi apparatus protein ARF1 sensitizes MDA-MB-231 breast cancer cells to the antitumor drugs Actinomycin D and Vinblastine through ERK and AKT signaling

Increasing evidence indicates that the Golgi apparatus plays active roles in cancer, but a comprehensive understanding of its functions in the oncogenic transformation has not yet emerged. At the same time, the Golgi is becoming well recognized as a hub that integrates its functions of protein and lipid biosynthesis to signal transduction for cell proliferation and migration in cancer cells. Nevertheless, the active function of the Golgi apparatus in cancer cells has not been fully evaluated as a target for combined treatment. Here, we analyzed the effect of perturbing the Golgi apparatus on the sensitivity of the MDA-MB-231 breast cancer cell line to the drugs Actinomycin D and Vinblastine. We disrupted the function of ARF1, a protein necessary for the homeostasis of the Golgi apparatus. We found that the expression of the ARF1-Q71L mutant increased the sensitivity of MDA-MB-231 cells to both Actinomycin D and Vinblastine, resulting in decreased cell proliferation and cell migration, as well as in increased apoptosis. Likewise, the combined treatment of cells with Actinomycin D or Vinblastine and Brefeldin A or Golgicide A, two disrupting agents of the ARF1 function, resulted in similar effects on cell proliferation, cell migration and apoptosis. Interestingly, each combined treatment had distinct effects on ERK1/2 and AKT signaling, as indicated by the decreased levels of either phospho-ERK1/2 or phospho-AKT. Our results suggest that disruption of Golgi function could be used as a strategy for the sensitization of cancer cells to chemotherapy.

DEPTOR suppresses the progression of esophageal squamous cell carcinoma and predicts poor prognosis

As a naturally occurring inhibitor of mTOR, accumulated evidence has suggested that DEPTOR plays a pivotal role in suppressing the progression of human malignances. However, the function of DEPTOR in the development of esophageal squamous cell carcinoma (ESCC) is still unclear. Here we report that the expression of DEPTOR is significantly reduced in tumor tissues derived from human patients with ESCC, and the downregulation of DEPTOR predicts a poor prognosis of ESCC patients. In addition, we found that the expression of DEPTOR negatively regulates the tumorigenic activities of ESCC cell lines (KYSE150, KYSE510 and KYSE190). Furthermore, ectopic DEPTOR expression caused a significant suppression of the cellular proliferation, migration and invasion of KYSE150 cells, which has the lowest expression level of DEPTOR in the three cell lines. Meanwhile, CRISPR/Cas9 mediated knockout of DEPTOR in KYSE-510 cells significantly promoted cellular proliferation, migration and invasion. In addition, in vivo assays further revealed that tumor growth was significantly inhibited in xenografts with ectopic DEPTOR expression as compared to untreated KYSE150 cells, and was markedly enhanced in DEPTOR knockout KYSE-510 cells. Biochemical studies revealed that overexpression of DEPTOR led to the suppression of AKT/mTOR pathway as evidenced by reduced phosphorylation of AKT, mTOR and downstream SGK1, indicating DEPTOR might control the progression of ESCC through AKT/mTOR signaling pathway. Thus, these findings, for the first time, demonstrated that DEPTOR inhibits the tumorigenesis of ESCC cells and might serve as a potential therapeutic target or prognostic marker for human patients with ESCC.

The use of natural products to target cancer stem cells

The cancer stem cell hypothesis has been used to explain many cancer complications resulting in poor patient outcomes including induced drug resistance, metastases to distant organs, and tumor recurrence. While the validity of the cancer stem cell model continues to be the cause of much scientific debate, a number of putative cancer stem cell markers have been identified making studies concerning the targeting of cancer stem cells possible. In this review, a number of identifying properties of cancer stem cells have been outlined including properties contributing to the drug resistance and metastatic potential commonly observed in supposed cancer stem cells. Due to cancer stem cells' numerous survival mechanisms, the diversity of cancer stem cell markers between cancer types and tissues, and the prevalence of cancer stem cell markers among healthy stem and somatic cells, it is likely that currently utilized treatments will continue to fail to eradicate cancer stem cells. The successful treatment of cancer stem cells will rely upon the development of anti-neoplastic drugs capable of influencing many cellular mechanisms simultaneously in order to prevent the survival of this evasive subpopulation. Natural compounds represent a historically rich source of novel, biologically active compounds which are able to interact with a large number of cellular targets while limiting the painful side-effects commonly associated with cancer treatment. A brief review of select natural products that have been demonstrated to diminish the clinically devastating properties of cancer stem cells or to induce cancer stem cell death is also presented.

The Fungal Metabolite Brefeldin A Inhibits Dvl2-Plk1-Dependent Primary Cilium Disassembly

The primary cilium is a non-motile microtubule-based organelle that protrudes from the surface of most human cells and works as a cellular antenna to accept extracellular signals. Primary cilia assemble from the basal body during the resting stage (G0 phase) and simultaneously disassemble with cell cycle re-entry. Defective control of assembly or disassembly causes diverse human diseases including ciliopathy and cancer. To identify the effective compounds for studying primary cilium disassembly, we have screened 297 natural compounds and identified 18 and 17 primary cilium assembly and disassembly inhibitors, respectively. Among them, the application of KY-0120, identified as Brefeldin A, disturbed Dvl2-Plk1-mediated cilium disassembly via repression of the interaction of CK1ɛ-Dvl2 and the expression of Plk1 mRNA. Therefore, our study may suggest useful compounds for studying the cellular mechanism of primary cilium disassembly to prevent ciliopathy and cancer.

Brefeldin A enhances docetaxel-induced growth inhibition and apoptosis in prostate cancer cells in monolayer and 3D cultures

Docetaxel is a commonly used chemotherapeutic drug for patients with late stage prostate cancer. However, serious side effect and drug resistance limit its clinical success. Brefeldin A is a 16-membered macrolide antibiotic from mangrove-derived Fungus Aspergillus sp. (9Hu), which exhibited potent cytotoxicity against human cancer cells. In the present study, we determined the effect of brefeldin A on docetaxel-induced growth inhibition and apoptosis in human prostate cancer PC-3 cells. Brefeldin A in combination with docetaxel inhibited the growth of PC-3 cells in monolayer and in three dimensional cultures. The combination also potently stimulated apoptosis in PC-3 cells as determined by propidium iodide staining and morphological assessment. Mechanistic studies showed that growth inhibition and apoptosis in PC-3 cells treated with brefeldin A and docetaxel were associated with decrease in the level of Bcl-2. The present study indicates that combined brefeldin A with docetaxel may represent a novel approach for improving the efficacy of docetaxel, and Bcl-2 may serve as a target for brefeldin A to enhance the effects of docetaxel chemotherapy.

HLA-E inhibitor enhances the killing of neuroblastoma stem cells by co-cultured dendritic cells and cytokine-induced killer cells loaded with membrane-based microparticles

Neuroblastoma stem cells (NSCs) can cause drug resistance and tumor recurrence. This study aimed to enhance the lytic effect of dendritic cells (DCs) co-cultured with cytokine-induced killer (CIK) cells. NSCs were obtained by suspension culture, and DC-CIK cells were loaded with extracted NSC membrane-based microparticles (MMPs) before evaluating the lytic effect of DC-CIK cells on NSCs. After inhibiting the function or expression of human leukocyte antigen-E (HLA-E) in NSCs by anti-HLA-E monoclonal antibody or siRNA, the DC-CIK cell lytic effect on NSCs was re-assessed. NSC nestin expression was high, but glial fibrillary acid protein expression and class IIIβ-tubulin-1 expression were low. Moreover, NSCs exhibited strong tumorigenic ability in nude mice. Loading DCs with NSC-derived MMPs induced the differentiation of DCs and CIK cells and enhanced the killing of NSCs by DC-CIK cells. Inhibiting the function or expression of HLA-E in NSCs further enhanced the cytolytic capability of DC-CIK cells loaded with NSC-derived MMPs. HLA-E inhibitor can enhance the killing of NSC by DC-CIK cells loaded with NSC-derived MMPs.

GOLPH3 drives cell migration by promoting Golgi reorientation and directional trafficking to the leading edge

The GOLPH3 oncogene functions in Golgi trafficking. GOLPH3 promotes cell migration, which is important in cancer. GOLPH3, by linking the Golgi to F-actin, promotes both Golgi reorientation and forward trafficking, which together drive trafficking to the leading edge. These findings provide insight into how GOLPH3 drives cell migration.

The mechanism of directional cell migration remains an important problem, with relevance to cancer invasion and metastasis. GOLPH3 is a common oncogenic driver of human cancers, and is the first oncogene that functions at the Golgi in trafficking to the plasma membrane. Overexpression of GOLPH3 is reported to drive enhanced cell migration. Here we show that the phosphatidylinositol-4-phosphate/GOLPH3/myosin 18A/F-actin pathway that is critical for Golgi–to–plasma membrane trafficking is necessary and limiting for directional cell migration. By linking the Golgi to the actin cytoskeleton, GOLPH3 promotes reorientation of the Golgi toward the leading edge. GOLPH3 also promotes reorientation of lysosomes (but not other organelles) toward the leading edge. However, lysosome function is dispensable for migration and the GOLPH3 dependence of lysosome movement is indirect, via GOLPH3’s effect on the Golgi. By driving reorientation of the Golgi to the leading edge and driving forward trafficking, particularly to the leading edge, overexpression of GOLPH3 drives trafficking to the leading edge of the cell, which is functionally important for directional cell migration. Our identification of a novel pathway for Golgi reorientation controlled by GOLPH3 provides new insight into the mechanism of directional cell migration with important implications for understanding GOLPH3’s role in cancer.

Inhibitory effect of trans-ferulic acid on proliferation and migration of human lung cancer cells accompanied with increased endogenous reactive oxygen species and β-catenin instability

Background

Trans-ferulic (FA) acid exhibits antioxidant effects in vitro. However, the underlying mechanism of trans-FA activity in cellular physiology, especially cancer physiology, remains largely unknown. This study investigated the cellular physiological effects of trans-FA on the H1299 human lung cancer cell line.

Methods

The 2,2-diphenyl-1-picrylhydrazyl assay was used to determine free radical scavenging capability. Assessment of intracellular reactive oxygen species (ROS) was evaluated using oxidized 2ʹ,7ʹ-dichlorofluorescin diacetate and dihydroethidium staining. Trypan blue exclusion, colony formation, and anchorage-independent growth assays were used to determine cellular proliferation. Annexin V staining assay was used to assess cellular apoptosis by flow cytometry. Wound healing and Boyden’s well assays were used to detect the migration and invasion of cells. Gelatin zymography was used to detect matrix metalloproteinase (MMP-2 and MMP-9) activity. Western blotting was used to detect expression levels of various signaling pathway proteins.

Results

DPPH assay results indicated that trans-FA exerted potent antioxidant effects. However, trans-FA increased intracellular ROS levels, including hydrogen peroxide and superoxide anion, in H1299 cells. Trans-FA treatment inhibited cellular proliferation and induced moderate apoptotic cell death at the highest concentration used (0.6 mM). Furthermore, trans-FA moderately inhibited the migration of H1299 cells at the concentrations of 0.3 and 0.6 mM and attenuated MMP-2 and MMP-9 activity. Trans-FA caused the phosphorylation of β-catenin, resulting in proteasomal degradation of β-catenin. Conversely, trans-FA treatment increased the expression of pro-apoptotic factor Bax and decreased the expression of pro-survival factor survivin.

Conclusion

Various concentrations (0.06–0.6 mM) of trans-FA exert both anti-proliferation and anti-migration effects in the human lung cancer cell line H1299.

Electronic supplementary material

The online version of this article (doi:10.1186/s13020-016-0116-7) contains supplementary material, which is available to authorized users.

Are salty liquid food flavorings in vitro antitumor substances?

The objective of this study was to evaluate the antiproliferative, cytotoxic and genotoxic potential of salty liquid synthetic flavorings of Butter, Cheddar Cheese and Onion. The antiproliferative potential (2.9-1500 µg/mL) was assessed by MTT assay after 72h using the human tumor lines SF-295 (glioblastoma), OVCAR-8 (ovarian), HCT-116 (colon) and HL-60 (promyelocytic leukemia) and primary cultures of murine Sarcoma 180 (S180) and peripheral blood mononuclear cells (PBMC). Allium cepa bulbs were exposed to growing respective doses (1 mL and 2 mL). Only Butter and Cheddar flavorings revealed cytotoxic activity on cancer cells, with IC50 values ranging from 125.4 µg/mL (Cheddar - HCT-116) to 402.6 µg/mL (Butter - OVCAR-8). Butter flavoring was the most cytotoxic on PBMC (136.3 µg/mL) and increased cell division rate in relation to the mitotic index but did not cause cellular aberrations. Onion and Cheddar flavorings reduced the mitotic index after 24h and 48h exposure, but only Onion flavoring resulted in cellular aberrations and mitotic spindle abnormalities, such as anaphase and telophase bridges, micronucleated cells, conchicine-metaphases and amplifications. So, Butter, Onion and/or Cheddar flavorings caused significant changes in the division of meristematic cells of A. cepa and presented cytotoxic action even on decontrolled proliferating human tumor cells.

Anticancer drugs for the modulation of endoplasmic reticulum stress and oxidative stress

Prior research has demonstrated how the endoplasmic reticulum (ER) functions as a multifunctional organelle and as a well-orchestrated protein-folding unit. It consists of sensors which detect stress-induced unfolded/misfolded proteins and it is the place where protein folding is catalyzed with chaperones. During this folding process, an immaculate disulfide bond formation requires an oxidized environment provided by the ER. Protein folding and the generation of reactive oxygen species (ROS) as a protein oxidative byproduct in ER are crosslinked. An ER stress-induced response also mediates the expression of the apoptosis-associated gene C/EBP-homologous protein (CHOP) and death receptor 5 (DR5). ER stress induces the upregulation of tumor necrosis factor-related apoptosis inducing ligand (TRAIL) receptor and opening new horizons for therapeutic research. These findings can be used to maximize TRAIL-induced apoptosis in xenografted mice. This review summarizes the current understanding of the interplay between ER stress and ROS. We also discuss how damage-associated molecular patterns (DAMPs) function as modulators of immunogenic cell death and how natural products and drugs have shown potential in regulating ER stress and ROS in different cancer cell lines. Drugs as inducers and inhibitors of ROS modulation may respectively exert inducible and inhibitory effects on ER stress and unfolded protein response (UPR). Reconceptualization of the molecular crosstalk among ROS modulating effectors, ER stress, and DAMPs will lead to advances in anticancer therapy.

The small GTPase ADP-Ribosylation Factor 1 mediates the sensitivity of triple negative breast cancer cells to EGFR tyrosine kinase inhibitors

The clinical use of EGFR-targeted therapy, in triple negative breast cancer patients, has been limited by the development of resistance to these drugs. Although activated signaling molecules contribute to this process, the molecular mechanisms remain relatively unknown. We have previously reported that the small GTPase ADP-Ribosylation Factor 1 (ARF1) is highly expressed in invasive breast cancer cells and acts as a molecular switch to activate EGF-mediated responses. In this study, we aimed at defining whether the high expression of ARF1 limits sensitivity of these tumor cells to EGFR inhibitors, such as gefitinib. Here, we show that the knock down of ARF1 expression or activity decreased the dose and latency time required by tyrosine kinase inhibitors to induce cell death. This may be explained by the observation that the depletion of ARF1 suppressed gefitinib-mediated activation of key mediators of survival such as ERK1/2, AKT and Src, while enhancing cascades leading to apoptosis such as the p38MAPK and JNK pathways, modifying the Bax/Bcl2 ratio and cytochrome c release. In addition, inhibiting ARF1 expression and activation also results in an increase in gefitinib-mediated EGFR internalization and degradation further limiting the ability of this receptor to promote its effects. Interestingly, we observed that gefitinib treatment resulted in the enhanced activation of ARF1 by promoting its recruitment to the receptor AXL, an important mediator of EGFR inhibition suggesting that ARF1 may promote its pro-survival effects by coupling to alternative mitogenic receptors in conditions where the EGFR is inhibited. Together our results uncover a new role for ARF1 in mediating the sensitivity to EGFR inhibition and thus suggest that limiting the activation of this GTPase could improve the therapeutic efficacy of EGFR inhibitors.

Existing drugs and their application in drug discovery targeting cancer stem cells

Despite standard cancer therapies such as chemotherapy and targeted therapy have shown some efficacies, the cancer in many cases eventually relapses and metastasizes upon stopping the treatment. There is a small subpopulation of cancer cells within tumor, with specific characters similar to those found in stem cells. This group of cancer cells is known as tumor-initiating or cancer stem cells (CSCs), which have an ability to self-renew and give rise to cancer cell progeny. CSCs are related with drug resistance, metastasis and relapse of cancer, hence emerging as a crucial drug target for eliminating cancer. Rapid advancement of CSC biology has enabled researchers to isolate and culture CSCs in vitro, making the cells amenable to high-throughput drug screening. Recently, drug repositioning, which utilizes existing drugs to develop potential new indications, has been gaining popularity as an alternative approach for the drug discovery. As existing drugs have favorable bioavailability and safety profiles, drug repositioning is now actively exploited for prompt development of therapeutics for many serious diseases, such as cancer. In this review, we will introduce latest examples of attempted drug repositioning targeting CSCs and discuss potential use of the repositioned drugs for cancer therapy.