Toxicarioside O induces protective autophagy in a sirtuin-1-dependent manner in colorectal cancer cells

A review on the impact of TRAIL on cancer signaling and targeting via phytochemicals for possible cancer therapy

Anticancer therapies have been the continual pursuit of this age. Cancer has been ravaging all across the globe breathing not just threats but demonstrating them. Remedies for cancer have been frantically sought after. Few have worked out, yet till date, the available cancer therapies have not delivered a holistic solution. In a world where the search for therapies is levitating towards natural remedies, solutions based on phytochemicals are highly prospective attractions. A lot has been achieved with inputs from plant resources, providing numerous natural remedies. In the current review, we intensely survey the progress achieved in the treatment of cancer through phytochemicals-based programmed cell death of cancer cells. More specifically, we have further reviewed and discussed the role of phytochemicals in activating apoptosis via Tumor Necrosis Factor-Alpha-Related Apoptosis-Inducing Ligand (TRAIL), which is a cell protein that can attach to certain molecules in cancer cells, killing cancer cells. The objective of this review is to enlist the various phytochemicals that are available for specifically contributing towards triggering the TRAIL cell protein-mediated cancer therapy and to point out the research gaps that require future research motivation. This is the first review of this kind in this research direction.

SIRT1 enhances oxaliplatin resistance in colorectal cancer through microRNA-20b-3p/DEPDC1 axis

Oxaliplatin (L-OHP) is a standard treatment drug for colorectal cancer (CRC), but acquired drug resistance limits the outcome of patients. We investigated the involvement of sirtuin 1 (SIRT1) in L-OHP resistance in the setting of CRC via microRNA-20b-3p/DEP domain containing 1 (miR-20b-3p/DEPDC1) axis. CRC tissues that were resistant or sensitive to L-OHP were harvested, in which SIRT1, miR-20b-3p, and DEPDC1 levels were tested. L-OHP-resistant-resistant CRC cells were transfected, subsequently, cellular proliferation, invasion, migration, and apoptosis were tested, and tumor resistance to L-OHP was observed. The binding of SIRT1 to miR-20b-3p promoter and the targeting relationship between miR-20b-3p and DEPDC1 were verified. An aberrant elevation in SIRT1 expression was seen in L-OHP-resistant CRC tissues and cells. Knockdown of SIRT1 sensitized CRC cells and xenografted CRC tumors to L-OHP. SIRT1 bound with miR-20b-3p promoter to regulate DEPDC1. Reducing miR-20b-3p or raising DEPDC1 levels weakened the effect of SIRT1 knockdown on L-OHP-resistant-CRC cells. SIRT1 enhances L-OHP resistance in CRC by mediating miR-20b-3p/DEPDC1 axis.

YAP activation attenuates toxicarioside G‑induced lethal autophagy arrest in SW480 colorectal cancer cells

Toxicarioside G (TCG), a natural product isolated from Calotropis gigantea, has been found to exhibit potent anticancer effects. The present study aimed to investigate the effect of TCG on the SW480 colorectal cancer cell line and the role of autophagy and Yes1 associated transcriptional regulator (YAP) in the TCG-mediated inhibition of cell proliferation and viability. Cell proliferation was detected using MTT, BrdU, colony formation and LDH release assays, while apoptosis was analyzed using flow cytometry and western blot analyses. Immunofluorescence and western blot analysis was used to determine TCG-induced autophagy and YAP activation. Pharmacological inhibition and siRNA was used to investigate the role of autophagy and YAP in TCG-mediated cell growth inhibition. The results revealed that TCG inhibited SW480 cell proliferation and viability, independent of apoptosis, and also induced autophagy. It was further demonstrated that TCG blocks autophagic flux, resulting in autophagy arrest in the SW480 cell line. The inhibition of autophagy restored the TCG-mediated inhibition of cell proliferation and viability, suggesting that TCG may induce lethal autophagy arrest in the SW480 cell line. Furthermore, TCG induced YAP activation in the SW480 cell line. Inhibition of YAP activity enhanced the TCG-mediated inhibition of cell proliferation and viability, suggesting that YAP may play a protective role in the TCG-induced effects. In conclusion, the findings of the present study indicated that TCG may induce lethal autophagy arrest and activate YAP, which serves a protective role in the SW480 cell line. These results suggested that the combined targeting of TCG and YAP may represent a promising strategy for TCG-mediated anticancer therapy.

Anticarin β Inhibits Human Glioma Progression by Suppressing Cancer Stemness via STAT3

Glioma is the most common form of malignant brain cancer. It is very difficult to cure malignant glioma because of the presence of glioma stem cells, which are a barrier to cure, have high tumorigenesis, associated with drug resistance, and responsible for relapse by regulating stemness genes. In this study, our results demonstrated that anticarin β, a natural compound from Antiaris toxicaria, can effectively and selectively suppress proliferation and cause apoptosis in glioma cells, which has an IC₅₀ that is 100 times lower than that in mouse normal neural stem cells. Importantly, cell sphere formation assay and real time-quantitative analysis reveal that anticarin β inhibits cancer stemness by modulating related stemness gene expression. Additionally, anticarin β induces DNA damage to regulate the oncogene expression of signal transducer and activator of transcription 3 (STAT3), Akt, mitogen-activated protein kinases (MAPKs), and eventually leading to apoptosis. Furthermore, anticarin β effectively inhibits glioma growth and prolongs the lifts pan of tumor-bearing mice without systemic toxicity in the orthotopic xenograft mice model. These results suggest that anticarin β is a promising candidate inhibitor for malignant glioma.

Preclinical Drug Discovery in Colorectal Cancer: A Focus on Natural Compounds

BACKGROUND

Colorectal cancer (CRC) is considered one of the most predominant and deadly cancer globally. Nowadays, the main clinical management for this cancer includes chemotherapy and surgery; however, these treatments result in the occurrence of drug resistance and severe side effects, and thus it is a crucial requirement to discover an alternative and potential therapy for CRC treatment. Numerous therapeutic cancers were initially recognized from natural metabolites utilized in traditional medicine, and several recent types of research have shown that many natural products own potential effects against CRC and may assist the action of chemotherapy for the treatment of CRC. It has been indicated that most patients are well tolerated by natural compounds without showing any toxicity signs even at high doses. Conventional chemotherapeutics interaction with natural medicinal compounds presents a new feature in cancer exploration and treatment. Most of the natural compounds overwhelm malignant cell propagation by apoptosis initiation of CRC cells and arresting of the cell cycle (especially at G, S, and G2/M phase) that result in inhibition of tumor growth.

OBJECTIVE

This mini-review aimed to focus on natural compounds (alkaloids, flavonoids, polysaccharides, polyphenols, terpenoids, lactones, quinones, etc.) that were identified to have anti- CRC activity in vitro on CRC cell lines and/or in vivo experiments on animal models.

CONCLUSION

Most of the studied active natural compounds possess anti-CRC activity via different mechanisms and pathways in vitro and in vivo that might be used as assistance by clinicians to support chemotherapy therapeutic strategy and treatment doses for cancer patients.

Phytochemicals as a Complement to Cancer Chemotherapy: Pharmacological Modulation of the Autophagy-Apoptosis Pathway

Bioactive plant derived compounds are important for a wide range of therapeutic applications, and some display promising anticancer properties. Further evidence suggests that phytochemicals modulate autophagy and apoptosis, the two crucial cellular pathways involved in the underlying pathobiology of cancer development and regulation. Pharmacological targeting of autophagy and apoptosis signaling using phytochemicals therefore offers a promising strategy that is complementary to conventional cancer chemotherapy. In this review, we sought to highlight the molecular basis of the autophagic-apoptotic pathway to understand its implication in the pathobiology of cancer, and explore this fundamental cellular process as a druggable anticancer target. We also aimed to present recent advances and address the limitations faced in the therapeutic development of phytochemical-based anticancer drugs.

Toxicarioside O Inhibits Cell Proliferation and Epithelial-Mesenchymal Transition by Downregulation of Trop2 in Lung Cancer Cells

Toxicarioside O (TCO), a natural product derived from Antiaris toxicaria, has been identified to be a promising anticancer agent. In this study, we aimed to investigate the effect of TCO on the proliferation and epithelial-mesenchymal transition (EMT) of lung cancer cells and its molecular mechanisms. Here, we indicated that TCO inhibits the proliferation of lung cancer cells both in vitro and in vivo. Our results demonstrated that TCO induces apoptosis in lung cancer cells. Moreover, we found that TCO suppresses EMT program and inhibits cell migration in vitro. Mechanistically, TCO decreases the expression of trophoblast cell surface antigen 2 (Trop2), resulting in inhibition of the PI3K/Akt pathway and EMT program. Overexpression of Trop2 rescues TCO-induced inhibition of cell proliferation and EMT. Our findings demonstrate that TCO markedly inhibits cell proliferation and EMT in lung cancer cells and provides guidance for its drug development.

Sirtuins' control of autophagy and mitophagy in cancer

Mammalian cells use a specialized and complex machinery for the removal of altered proteins or dysfunctional organelles. Such machinery is part of a mechanism called autophagy. Moreover, when autophagy is specifically employed for the removal of dysfunctional mitochondria, it is called mitophagy. Autophagy and mitophagy have important physiological implications and roles associated with cellular differentiation, resistance to stresses such as starvation, metabolic control and adaptation to the changing microenvironment. Unfortunately, transformed cancer cells often exploit autophagy and mitophagy for sustaining their metabolic reprogramming and growth to a point that autophagy and mitophagy are recognized as promising targets for ongoing and future antitumoral therapies. Sirtuins are NAD+ dependent deacylases with a fundamental role in sensing and modulating cellular response to external stresses such as nutrients availability and therefore involved in aging, oxidative stress control, inflammation, differentiation and cancer. It is clear, therefore, that autophagy, mitophagy and sirtuins share many common aspects to a point that, recently, sirtuins have been linked to the control of autophagy and mitophagy. In the context of cancer, such a control is obtained by modulating transcription of autophagy and mitophagy genes, by post translational modification of proteins belonging to the autophagy and mitophagy machinery, by controlling ROS production or major metabolic pathways such as Krebs cycle or glutamine metabolism. The present review details current knowledge on the role of sirtuins, autophagy and mitophagy in cancer to then proceed to discuss how sirtuins can control autophagy and mitophagy in cancer cells. Finally, we discuss sirtuins role in the context of tumor progression and metastasis indicating glutamine metabolism as an example of how a concerted activation and/or inhibition of sirtuins in cancer cells can control autophagy and mitophagy by impinging on the metabolism of this fundamental amino acid.

Repurposing Ziyuglycoside II Against Colorectal Cancer via Orchestrating Apoptosis and Autophagy

Effective chemotherapy drugs for colorectal cancer remain a challenge. In this research, Ziyuglycoside II (Ziyu II), exhibits considerable antitumor activity against CRC cells both in vitro and in vivo. The results showed that Ziyu II induced apoptosis through the accumulation of reactive oxygen species (ROS), which was necessary for Ziyu II to inhibit colorectal cancer cells. Intriguingly, The treatment of Ziyu II triggered complete autophagic flux in CRC cells. Inhibition of autophagy partially reversed Ziyu II-induced growth inhibition, demonstrating a cytotoxic role of autophagy in response to Ziyu II-treated. Mechanism indicated that Ziyu II-induced autophagy by inhibiting Akt/mTOR pathway. Akt reactivation partially reduced Ziyu II-induced LC3-II turnover and LC3 puncta accumulation. Especially, Ziyu II improves the sensitivity of 5-fluorouracil which is the first-line chemotherapy drug in colorectal cancer cells. This research provides novel insight into the molecular mechanism of Ziyu II’s anti-proliferation, including apoptosis and autophagy, and lays a foundation for the potential application of Ziyu II in clinical CRC treatment.

AMPK/mTOR/ULK1 Axis-Mediated Pathway Participates in Apoptosis and Autophagy Induction by Oridonin in Colon Cancer DLD-1 Cells

BACKGROUND

Oridonin has been demonstrated to exert strong antitumor activities in various types of human cancers. Our previous study established that oridonin induced the apoptosis of and exerted an inhibitory effect on colon cancer cells in vitro and in vivo. However, the mechanisms behind the antitumor effects of oridonin on colorectal cancer are not clearly known. This study explored whether autophagy was involved in antitumorigenesis effects caused by the usage of oridonin in colon cancer and examined whether the AMPK/mTOR/ULK1 signaling pathway was involved in this process.

METHODS

Cell viability was determined using CCK-8 assay. The distribution of cell apoptosis was evaluated using flow cytometry. RT-PCR and Western blotting analysis were conducted to identify the key target genes and proteins involved in the AMPK/mTOR cascade. AMPK siRNA was used to disturb AMPK expression. A DLD-1 cell orthotopic transplantation tumor model was established to explore the anti-cancer effects in vivo.

RESULTS

Oridonin exhibited a suppressive effect on DLD-1 cells in a concentration- and time-dependent manner. Additionally, in a dose-dependent manner, oridonin induced cell apoptosis via inducing the protein expression levels of cleaved caspase-3, cleaved PARP and stimulated autophagy by increasing protein expression levels of Becin1, LC3-II, decreasing protein expression levels of LC3-I, p62, which were respectively attenuated and elevated by autophagy inhibitor 3-MA. Furthermore, oridonin upregulated the expression level of p-AMPK and downregulated the expression levels of p-mTOR, p-ULK1 in the DLD-1 cells in a dose-dependent manner. Moreover, knockdown of AMPK by a specific siRNA reversed the expression levels of proteins involved in the AMPK/mTOR pathway, autophagy and apoptosis. In addition, outcomes from the in vivo experiments also showed that oridonin treatment significantly repressed tumorigenic growth of DLD-1 cells without any side effects, which was accompanied by the upregulation of p-AMPK, LC3-II, active caspase-3 protein expression levels and the downregulation of p-mTOR and p-ULK1 protein expression levels.

CONCLUSION

This study demonstrated that oridonin induced apoptosis and autophagy of colon cancer DLD-1 cells via regulating the AMPK/mTOR/ULK1 pathway, which indicated that oridonin may be used as a novel therapeutic intervention for patients with colorectal cancer.

Decyl caffeic acid inhibits the proliferation of colorectal cancer cells in an autophagy-dependent manner in vitro and in vivo

The treatment of human colorectal cancer (CRC) cells through suppressing the abnormal survival signaling pathways has recently become a significant area of focus. In this study, our results demonstrated that decyl caffeic acid (DC), one of the novel caffeic acid derivatives, remarkedly suppressed the growth of CRC cells both in vitro and in vivo. The inhibitory effects of DC on CRC cells were investigated in an in vitro cell model and in vivo using a xenograft mouse model. CRC cells were treated with DC at various dosages (0, 10, 20 and 40 μM), and cell survival, the apoptotic index and the autophagy level were measured using an MTT assay and flow cytometry analysis, respectively. The signaling cascades in CRC were examined by Western blot assay. The anti-cancer effects of DC on tumor growth were examined by using CRC HCT-116 cells implanted in an animal model. Our results indicated that DC differentially suppressed the growth of CRC HT-29 and HCT-116 cells through an enhancement of cell-cycle arrest at the S phase. DC inhibited the expression of cell-cycle regulators, which include cyclin E and cyclin A proteins. The molecular mechanisms of action were correlated to the blockade of the STAT3 and Akt signaling cascades. Strikingly, a high dosage of DC prompted a self-protection action through inducing cell-dependent autophagy in HCT-116 cells. Suppression of autophagy induced cell death in the treatment of DC in HCT-116 cells. DC seemed to inhibit cell proliferation of CRC differentially, and the therapeutic advantage appeared to be autophagy dependent. Moreover, consumption of DC blocked the tumor growth of colorectal adenocarcinoma in an experimental animal model. In conclusion, our results suggested that DC could act as a therapeutic agent through the significant suppression of tumor growth of human CRC cells.

Arctigenin suppresses cell proliferation via autophagy inhibition in hepatocellular carcinoma cells

Autophagy is a catabolic process that degrades dysfunctional proteins and organelles and plays critical roles in cancer development. Our preliminary screening identified that extracts of the fruits of Arctium lappa and the fruits of Forsythia suspensa notably suppressed the proliferation of hepatocellular carcinoma HepG2 cells and downregulated the autophagy. In this study, we explored the effect of arctigenin (ARG), a bioactive lignan in both extracts, on cell proliferation and autophagy-related proteins in HepG2 cells. ARG inhibited the proliferation of HepG2 cells. Analysis of autophagy-related proteins demonstrated that ARG might block the autophagy that leads to sequestosome 1/p62 (p62) accumulation. The stage of inhibition in autophagy by ARG differed from those by the autophagy inhibitors 3-methyladenine (3-MA) or chloroquine (CQ). ARG could also inhibit starvation-induced autophagy. Further analysis of apoptosis-related proteins indicated that ARG did not affect caspase-3 activation and PARP cleavage, suggesting that the antiproliferative effect of ARG can occur independently of apoptosis. In summary, our study showed that ARG suppresses cell proliferation and inhibits autophagy, and might lead to the development of agents for autophagy research and cancer chemoprevention.

Up-regulation of DRAM2 promotes tolerance of bladder transitional cell carcinoma to gemcitabine

INTRODUCTION

Bladder transitional cell carcinoma (BTCC) is one of the most prevalent human malignant diseases. Gemcitabine is commonly applied in the treatment of BTCC while acquired gemcitabine resistance has caused a severe impediment to recovery. This study aimed to investigate the function of DRAM2 in regulating gemcitabine resistance of BTCC.

MATERIAL AND METHODS

GSE77883 was introduced to screen out the differentially expressed autophagy-related genes in T24 cells and gemcitabine-resistant T24-GEM cells. After establishing T24-GEM cells ourselves, aberrant expression of DRAM2 was detected by qRT-PCR and Western blot. After stably manipulating the expression of DRAM2 in T24 and T24-GEM cells, the changes of cell biological functions under gemcitabine treatment were compared, including cell viability, apoptosis and autophagy, using colony formation, flow cytometry and electron microscopy respectively.

RESULTS

DRAM2 was up-regulated in gemcitabine-resistant T24-GEM cells. Silencing of DRAM2 in T24-GEM cells inhibited the cell autophagy induced by treatment with gemcitabine and contributed to attenuated gemcitabine resistance. Also, overexpression of DRAM2 in T24 cells enhanced the autophagy, strengthened the chemoresistance and decreased the cell apoptosis rate under the treatment with gemcitabine.

CONCLUSIONS

Our data suggested that downregulation of DRAM2 rescued the sensitivity of T24-GEM cells to gemcitabine, providing an appropriate therapeutic target for BTCC treatment.

Autophagy and its potent modulators from phytochemicals in cancer treatment

Autophagy is a ubiquitous catabolic process by which damaged or harmful intracellular components are delivered to the lysosomes for self-digestion and recycling. It is critical in cancer treatment. Therapy-induced autophagy predominantly acts as a pro-survival mechanism, but progressive autophagy can lead to non-apoptotic cell death, also known as autophagic cell death. Plants or herbs contain various natural compounds that are widely used in the treatment of many types of malignancies. Emerging evidence indicates that phytochemicals targeting the autophagic pathway are promising agents for cancer treatment. However, these compounds play different roles in autophagy. In this review, we discussed the role of autophagy in cancer development and therapy, and focussed on elucidating the anti-cancer activities of autophagic modulators, especially phytochemicals. Notably, we described a novel premise that the dynamic role of phytochemicals should be evaluated in regulation of autophagy in cancer.

Autophagy plays a protective role against apoptosis induced by toxicarioside N via the Akt/mTOR pathway in human gastric cancer SGC-7901 cells

Toxicarioside N (Tox N), a natural product extract from Antiaris toxicaria, has been reported to induce apoptosis in human gastric cancer cells. However, the mechanism and actual role of autophagy in Tox N-induced apoptosis of human gastric cancer cells remains poorly understood. In the current study, we demonstrated that Tox N could induce autophagy by inhibiting the Akt/mTOR signaling pathway in SGC-7901 cells. Moreover, we found that the inhibition of autophagy by 3-methyladenine, an autophagy inhibitor, enhanced Tox N-induced apoptotic cell death. However, the stimulation of autophagy by rapamycin, an autophagy activator, remarkably suppressed Tox N-induced apoptosis, suggesting that autophagy plays a protective role in Tox N-induced apoptosis. Thus, the results from this study suggested that Tox N combination with an autophagy inhibitor might be a promising strategy to enhance the anticancer activity of Tox N for the treatment of human gastric cancer.

PINK1/Parkin-mediated mitophagy was activated against 1,4-Benzoquinone-induced apoptosis in HL-60 cells

Hematotoxicity of benzene is derived mainly from its active metabolite, 1,4-Benzoquinone (1,4-BQ), which induces cell apoptosis and mitochondrial damage. Damaged mitochondria are degraded through a specialized autophagy pathway, called mitophagy, which is driven by PINK1/Parkin signaling. However, whether mitophagy is involved in 1,4-BQ-induced toxicity remains unclear. This study was designed to investigate whether PINK1/Parkin-mediated mitophagy is activated in 1,4-BQ-treated HL-60 cells, and the roles mitophagy plays in 1,4-BQ-induced apoptosis. Our results demonstrated that 1,4-BQ induced autophagy in HL-60 cells, characterized by increased LC3-II/LC3-I ratio and Beclin1 expression, as well as decreased expression of p62. We confirmed the presence of mitophagosomes using electron microscopy, and found that 1,4-BQ-induced autophagy was blocked by pretreatment with the mitophagy inhibitor Cyclosporine A (CsA). In addition, we found that 1,4-BQ induced mitochondrial stress through decreased mitochondrial membrane potential (MMP) and increasedproduction of reactive oxygen species (ROS). We also confirmed that 1,4-BQ-induced mitophagy was mediated by the PINK1/Parkin pathway, illustrated by increased expression of PINK1 and Parkin mRNA and protein. Finally, we examined 1,4-BQ-induced apoptosis with or without CsA, which demonstrated that apoptosis increased after mitophagy inhibition, suggesting that mitophagy has a protective effect in this context. In conclusion, this study demonstrates that the activated PINK1/Parkin-mediated mitophagy exerts a significantly protective effect against 1,4-BQ-induced apoptosis in HL-60 cells.