Targeting apoptosis as an approach for gastrointestinal cancer therapy. Drug Resist Updat. 2009;12:55-64. [PMID: 19278896 DOI: 10.1016/j.drup.2009.02.002]

Different Roles of Apoptosis and Autophagy in the Development of Human Colorectal Cancer

Colorectal cancer (CRC) remains a major life-threatening malignancy, despite numerous therapeutic and screening attempts. Apoptosis and autophagy are two processes that share common signaling pathways, are linked by functional relationships and have similar protein components. During the development of cancer, the two processes can trigger simultaneously in the same cell, causing, in some cases, an inhibition of autophagy by apoptosis or apoptosis by autophagy. Malignant cells that have accumulated genetic alterations can take advantage of any alterations in the apoptotic process and as a result, progress easily in the cancerous transformation. Autophagy often plays a suppressive role during the initial stages of carcinogenicity, while in the later stages of cancer development it can play a promoting role. It is extremely important to determine the regulation of this duality of autophagy in the development of CRC and to identify the molecules involved, as well as the signals and the mechanisms behind it. All the reported experimental results indicate that, while the antagonistic effects of autophagy and apoptosis occur in an adverse environment characterized by deprivation of oxygen and nutrients, leading to the formation and development of CRC, the effects of promotion and collaboration usually involve an auxiliary role of autophagy compared to apoptosis. In this review, we elucidate the different roles of autophagy and apoptosis in human CRC development.

Vitamin D3 actions on astrocyte cells: A target for therapeutic strategy in Parkinson's disease?

Parkinson's disease (PD) is a neurodegenerative disease characterized by the loss of dopaminergic cells in the substantia nigra pars compacta. PD patients' brains show neuroinflammation, oxidative stress, and mitochondrial dysfunction. The present study aims to evaluate the neuroprotective activity of VD3 on astrocytes after their exposure to rotenone (ROT) a natural pesticide known to exhibit neurotoxic potential via the inhibition of mitochondrial complex I. Cell viability parameters were evaluated by the MTT test and staining with 7-AAD in cultures of astrocytes treated and untreated with VD3 (0.1, 0.5, and 1.0 ng/mL) and/or ROT (10 µg/mL or 5 µg/mL), and the cytoplasmic production of ROS and the cell death profile were measured by flow cytometry. Glutathione accumulation and ultrastructural changes were evaluated and immunocytochemistry assays for NF-kB and Nrf2 were also carried out. The results showed that VD3 improved the viability of cells previously treated with VD3 and then exposed to ROT, reducing the occurrence of necrotic and apoptotic events. Furthermore, cells exposed to ROT showed increased production of ROS, which decreased significantly with previous treatment with VD3. Importantly, the decrease by ROT in the mitochondrial transmembrane potential was significantly prevented after treating cells with VD3, especially at a concentration of 1 ng/mL. Therefore, treatment with VD3 protected astrocytes from damage caused by ROT, decreasing oxidative stress, decreasing NF-kB and Nrf2 expressions, and improving mitochondrial function. However, further investigation is needed regarding the participation and mechanism of action of VD3 in this cellular model of PD focusing on the crosstalk between Nrf2 and NF-kB.

1α,25-Dihydroxyvitamin D3 (VD3) Shows a Neuroprotective Action Against Rotenone Toxicity on PC12 Cells: An In Vitro Model of Parkinson's Disease

Parkinson's disease (PD) is characterized by dopaminergic cell loss in the substantia nigra, and PD brains show neuroinflammation, oxidative stress, and mitochondrial dysfunction. The study evaluated the neuroprotective activity of 1α,25-dihydroxy vitamin D3 (VD3), on the rotenone (ROT)-induced cytotoxicity in PC12 cells. The viability parameters were assessed by the MTT and flow cytometry, on cells treated or not with VD3 and/or ROT. Besides, ROS production, cell death, mitochondrial transmembrane potential, reduced GSH, superoxide accumulation, molecular docking (TH and Keap1-Nrf2), and TH, Nrf2, NF-kB, and VD3 receptor protein contents by western blot were evaluated. VD3 was shown to improve the viability of ROT-exposed cells. Cells exposed to ROT showed increased production of ROS and superoxide, which decreased after VD3. ROT decrease in the mitochondrial transmembrane potential was prevented, after VD3 treatment and, VD3 was shown to interact with tyrosine hydroxylase (TH) and Nrf2. While ROT decreased TH, Nrf2, and NF-kB expressions, these effects were reversed by VD3. In addition, VD3 also increased VD3 receptor protein contents and values went back to those of controls after ROT exposure. VD3 protects PC12 cells against ROT damage, by decreasing oxidative stress and improving mitochondrial function. One target seems to be the TH molecule and possibly an indirect Nrf2 activation could also justify its neuroprotective actions on this PC12 cell model of PD.

Effects and Mechanisms of Curcumin for the Prevention and Management of Cancers: An Updated Review

Cancer is the leading cause of death in the world. Curcumin is the main ingredient in turmeric (Curcuma longa L.), and is widely used in the food industry. It shows anticancer properties on different types of cancers, and the underlying mechanisms of action include inhibiting cell proliferation, suppressing invasion and migration, promoting cell apoptosis, inducing autophagy, decreasing cancer stemness, increasing reactive oxygen species production, reducing inflammation, triggering ferroptosis, regulating gut microbiota, and adjuvant therapy. In addition, the anticancer action of curcumin is demonstrated in clinical trials. Moreover, the poor water solubility and low bioavailability of curcumin can be improved by a variety of nanotechnologies, which will promote its clinical effects. Furthermore, although curcumin shows some adverse effects, such as diarrhea and nausea, it is generally safe and tolerable. This paper is an updated review of the prevention and management of cancers by curcumin with a special attention to its mechanisms of action.

iPCD: A Comprehensive Data Resource of Regulatory Proteins in Programmed Cell Death

Programmed cell death (PCD) is an essential biological process involved in many human pathologies. According to the continuous discovery of new PCD forms, a large number of proteins have been found to regulate PCD. Notably, post-translational modifications play critical roles in PCD process and the rapid advances in proteomics have facilitated the discovery of new PCD proteins. However, an integrative resource has yet to be established for maintaining these regulatory proteins. Here, we briefly summarize the mainstream PCD forms, as well as the current progress in the development of public databases to collect, curate and annotate PCD proteins. Further, we developed a comprehensive database, with integrated annotations for programmed cell death (iPCD), which contained 1,091,014 regulatory proteins involved in 30 PCD forms across 562 eukaryotic species. From the scientific literature, we manually collected 6493 experimentally identified PCD proteins, and an orthologous search was then conducted to computationally identify more potential PCD proteins. Additionally, we provided an in-depth annotation of PCD proteins in eight model organisms, by integrating the knowledge from 102 additional resources that covered 16 aspects, including post-translational modification, protein expression/proteomics, genetic variation and mutation, functional annotation, structural annotation, physicochemical property, functional domain, disease-associated information, protein–protein interaction, drug–target relation, orthologous information, biological pathway, transcriptional regulator, mRNA expression, subcellular localization and DNA and RNA element. With a data volume of 125 GB, we anticipate that iPCD can serve as a highly useful resource for further analysis of PCD in eukaryotes.

Immunomodulation by Gut Microbiome on Gastrointestinal Cancers: Focusing on Colorectal Cancer

Simple Summary

A symbiotic relationship with the host gut microbiome influences the immune system’s development, functions, and activities. In the mucosa, the gut microbiome mediates several immune activities such as the induction of naïve T-cells differentiation, production of cytokines, and myeloid cells activation. The gut-immune interaction and GI cancer development were investigated more recently. Understanding the interaction’s underlying mechanism provides insight to use them as potential anti-cancer targets. Even though multiple reports support the role of gut-immune interactions in targeting cancer-related pathways such as inflammation, apoptosis, and cellular proliferation, efforts are required to assess their interaction and impact on current treatment options.

Abstract

Gastrointestinal cancer (GI) is a global health disease with a huge burden on a patient’s physical and psychological aspects of life and on health care providers. It is associated with multiple disease related challenges which can alter the patient’s quality of life and well-being. GI cancer development is influenced by multiple factors such as diet, infection, environment, and genetics. Although activating immune pathways and components during cancer is critical for the host’s survival, cancerous cells can target those pathways to escape and survive. As the gut microbiome influences the development and function of the immune system, research is conducted to investigate the gut microbiome–immune interactions, the underlying mechanisms, and how they reduce the risk of GI cancer. This review addresses and summarizes the current knowledge on the major immune cells and gut microbiome interactions. Additionally, it highlights the underlying mechanisms of immune dysregulation caused by gut microbiota on four major cancerous pathways, inflammation, cellular proliferation, apoptosis, and metastasis. Overall, gut-immune interactions might be a key to understanding GI cancer development, but further research is needed for more detailed clarification.

The Emerging Role of Ferroptosis in Sepsis

Ferroptosis is a novel form of cell death characterized by the iron-dependent accumulation of lipid peroxides and is different from other types of cell death. The mechanisms of ferroptosis are discussed in the review, including System Xc-, Glutathione Peroxidase 4 pathway, Ferroptosis Suppressor Protein 1 and Dihydroorotate Dehydrogenase pathway. Ferroptosis is associated with the occurrence of various diseases, including sepsis. Research in recent years has displayed that ferroptosis is involved in sepsis occurrence and development. Iron chelators can inhibit the development of sepsis and improve the survival rate of septic mice. The ferroptotic cells can release damage-associated molecular patterns and lipid peroxidation, which further mediate inflammatory responses. Ferroptosis inhibitors can resist sepsis-induced multiple organ dysfunction and inflammation. Finally, we reviewed ferroptosis, an iron-dependent form of cell death that is different from other types of cell death in biochemistry, morphology, and major regulatory mechanisms, which is involved in multiple organ injuries caused by sepsis. Exploring the relationship between sepsis and ferroptosis may yield new treatment targets for sepsis.

BRAF-activated WT1 contributes to cancer growth and regulates autophagy and apoptosis in papillary thyroid carcinoma

Background

Papillary thyroid carcinoma (PTC) is one of most prevalent malignant endocrine neoplasms, and it is associated with a high frequency of BRAF gene mutations, which lead to lymphatic metastasis and distant metastasis that promote tumor progression. The molecular mechanism of PTC and the role of BRAF mutation in PTC progression and development need to be further elucidated.

Methods

In this study, a comprehensive bioinformatics analysis was performed to identify the differentially expressed genes and signaling pathways in thyroid cancer patients carrying mutant BRAF. Then, we confirmed the prognostic role of WT1 in thyroid cancer patients. Immunohistochemistry was performed to measure the expression profile of WT1 in PTC tissue. Lentivirus shWT1 was transfected into BRAFV600E (mutant) PTC cells to stably inhibit WT1 expression. CCK-8, EdU, immunofluorescence, colony formation, cell migration, cell wound healing, apoptosis and autophagy assays were performed to assess the biological functions of WT1 in BRAFV600E PTC cells. RNA sequencing, immunohistochemistry and immunoblotting were performed to explore the molecular mechanism of WT1 in BRAFV600E PTC cells.

Results

The results confirmed that “epithelial cell proliferation”, “apoptosis” and “selective autophagy” were closely associated with this BRAF mutant in these thyroid cancer patients. Knocking down BRAF-activated WT1 effectively inhibited the proliferation and migration of BRAFV600E PTC cells. Silencing WT1 significantly inhibited autophagy and promoted the apoptosis of BRAFV600E PTC cells. Mechanistic investigations showed that silencing WT1 expression remarkably suppressed the AKT/mTOR and ERK/P65 signaling pathways in BRAFV600E PTC cells.

Conclusion

All these results indicate that WT1 is a promising prognostic biomarker and facilitates PTC progression and development of cells carrying the BRAFV600E mutation.

A Novel Anticancer Stem Cell Compound Derived from Pleuromutilin Induced Necroptosis of Melanoma Cells

Necroptosis has been recently confirmed as a non-apoptotic form of programmed cell death. Discovery of novel chemical entities, capable of inducing necroptosis of cancer cells, is likely to act as an alternative strategy for dealing with drug resistance clinically. In this study, the identification of a novel Pleuromutilin derivative (compound 38) is presented, capable of significantly increasing the cellular level of ROS and inducing melanoma cancer cell death via necroptosis. Furthermore, compound 38 noticeably ablated various cancer stem cells and inhibited the growth of melanoma cancer cells both in vitro and in vivo. Moreover, 38 exhibited low toxicity in animal models and excellent PK properties, which is currently being verified as a potential anticancer drug candidate.

Podophyllotoxin Induces ROS-Mediated Apoptosis and Cell Cycle Arrest in Human Colorectal Cancer Cells via p38 MAPK Signaling

Podophyllotoxin (PT), a lignan compound from the roots and rhizomes of Podophyllum peltatum, has diverse pharmacological activities including anticancer effect in several types of cancer. The molecular mechanism of the anticancer effects of PT on colorectal cancer cells has not been reported yet. In this study, we sought to evaluate the anticancer effect of PT on human colorectal cancer HCT116 cells and identify the detailed molecular mechanism. PT inhibited the growth of cells and colony formation in a concentration-dependent manner and induced apoptosis as determined by the annexin V/7-aminoactinomycin D double staining assay. PT-induced apoptosis was accompanied by cell cycle arrest in the G2/M phase and an increase in the generation of reactive oxygen species (ROS). The effects of PT on the induction of ROS and apoptosis were prevented by pretreatment with N-acetyl-L-cysteine (NAC), indicating that an increase in ROS generation mediates the apoptosis of HCT116 cells induced by PT. Furthermore, Western blot analysis showed that PT upregulated the level of phospho (p)-p38 mitogen-activated protein kinase (MAPK). The treatment of SB203580, a p38 inhibitor, strongly prevented the apoptosis induced by PT, suggesting that PT-induced apoptosis involved the p38 MAPK signaling pathway. In addition, PT induced the loss of mitochondrial membrane potential and multi-caspase activation. The results suggested that PT induced cell cycle arrest in the G2/M phase and apoptosis through the p38 MAPK signaling pathway by upregulating ROS in HCT116 cells.

Enzymatic Metabolism of Flavonoids by Gut Microbiota and Its Impact on Gastrointestinal Cancer

Gastrointestinal (GI) cancer is a prevalent global health disease with a massive burden on health care providers. Internal and external factors such as obesity, smoking, diet (red meat), low socioeconomic status and infection with Helicobacter pylori are the critical risk factors of GI cancers. Flavonoids are natural phenolic compounds found abundantly in fruits and vegetables. Upon ingestion, 90% of flavonoids consumed require further enzymatic metabolism by the gut microbiome to enhance their bioavailability and absorption. Several epidemiological studies reported that consumption of flavonoids and their enzymatic conversion by gut microbes is strongly associated with the reduced risk of GI cancer development. This review summarizes the current knowledge on the enzymatic conversion of flavonoids by the human gut microbiome. It also addresses the underlying anti-GI cancer effects on metabolic pathways such as apoptosis and cellular proliferation. Overall, metabolites produced from flavonoid's enzymatic conversion illustrate anti-GI cancer effects, but the mechanisms of action need further clarification.

Progress in the study of D-α-tocopherol polyethylene glycol 1000 succinate (TPGS) reversing multidrug resistance

Currently, multidrug resistance (MDR) is one of the major reasons for failure in clinical cancer chemotherapy. Overexpression of the ATP binding cassette (ABC) transporter P-glycoprotein (P-gp), which significantly increases the efflux of anticancer drugs from tumor cells, enhances MDR. In the past few decades, four generations of P-gp inhibitors have appeared. However, they are limited in clinical application due to their severe toxic side effects. As a P-gp inhibitor and carrier for loading chemotherapy agents, TPGS has received increasing attention due to its advantages and unique properties of reversing MDR. TPGS is an amphipathic agent that increases the solubility of most chemotherapy drugs and decreases severe side effects. In addition, TPGS is an excellent carrier with P-gp-inhibiting ability. In this review, we summarize the latest articles on TPGS-based nanodelivery systems to prevent MDR.

The Role and Clinical Implications of the Retinoblastoma (RB)-E2F Pathway in Gastric Cancer

Gastric cancer is the most common malignant tumor in the digestive tract, with very high morbidity and mortality in developing countries. The pathogenesis of gastric cancer is a complex biological process mediated by abnormal regulation of proto-oncogenes and tumor suppressor genes. Although there have been some in-depth studies on gastric cancer at the molecular level, the specific mechanism has not been fully elucidated. RB family proteins (including RB, p130, and p107) are involved in cell cycle regulation, a process that largely depends on members of the E2F gene family that encode transcriptional activators and repressors. In gastric cancer, inactivation of the RB-E2F pathway serves as a core transcriptional mechanism that drives cell cycle progression, and is regulated by cyclins, cyclin-dependent kinases, cyclin-dependent kinase inhibitors, p53, Helicobacter pylori and some other upstream molecules. The E2F proteins are encoded by eight genes (i.e. E2F1 to E2F8), each of which may play a specific role in gastric cancer. Interestingly, a single E2F such as E2F1 can activate or repress transcription, and enhance or inhibit cell proliferation, depending on the cell environment. Thus, the function of the E2F transcription factor family is very complex and needs further exploration. Importantly, the presence of H. pylori in stomach mucosa may affect the RB and p53 tumor suppressor systems, thereby promoting the occurrence of gastric cancer. This review aims to summarize recent research progress on important roles of the complex RB-E2F signaling network in the development and effective treatment of gastric cancer.

Guaiazulene Triggers ROS-Induced Apoptosis and Protective Autophagy in Non-small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) is one of the most frequent cancers worldwide, yet effective treatment remains a clinical challenge. Guaiazulene (GYZ), a cosmetic color additive, has previously been characterized as a potential antitumor agent due to observed anticancer effects. However, the efficacy of GYZ in the treatment of NSCLC and the involved molecular mechanisms remain largely unknown. Here, we indicated a role for GYZ in the suppression of NSCLC both in vitro and in vivo via triggering reactive oxygen species (ROS)-induced apoptosis. Concomitantly, GYZ induced complete autophagic flux in NSCLC cells via inhibiting the Akt/mTOR signaling pathway, which displayed cytoprotective effect against GYZ-induced growth suppression. Accompanied with autophagy inhibition obviously enhanced the effects of GYZ. Notably, GYZ acts synergistically with paclitaxel in the suppression of NSCLC in vitro. Together, our results for the first time reported that GYZ suppressed the proliferation of NSCLC and suggested a potential strategy for inhibiting NSCLC growth by combinational use of GYZ and autophagy inhibitors.

The quinazoline derivative, 04NB-03, induces cell cycle arrest and apoptosis in hepatocellular carcinoma cells in a reactive oxygen species-dependent manner

Hepatocellular carcinoma (HCC) is one of the most deadly malignancies worldwide. However, current therapeutic drugs for HCC are far from satisfactory. Thus, the development of new drugs is urgently needed. In this study, we identified a novel quinazoline derivative, 04NB-03, with potent anti-HCC activities both in vitro and in vivo. 04NB-03 effectively suppressed the viability and proliferation of HCC cells. It induced both cell cycle arrest at the G2/M phase and apoptosis in concentration- and time-dependent manners. Moreover, 04NB-03 treatment significantly reduced xenograft tumor growth without notable toxic effects. Mechanistically, 04NB-03 induced endogenous reactive oxygen species (ROS) accumulation in concentration- and time-dependent manners. Scavenging the ROS reversed 04NB-03-induced cell cycle arrest and apoptosis. Taken together, these results indicate that the quinazoline derivative, 04NB-03, inhibits the growth of HCC cells through the induction of cell cycle arrest and apoptosis in an ROS-dependent manner. 04NB-03 is, therefore, a potential small molecule candidate for the development of antitumor drugs targeting HCC.

Anti-Tumor Drug Discovery Based on Natural Product β-Elemene: Anti-Tumor Mechanisms and Structural Modification

Natural products are important sources for drug discovery, especially anti-tumor drugs. β-Elemene, the prominent active ingredient extract from the rhizome of Curcuma wenyujin, is a representative natural product with broad anti-tumor activities. The main molecular mechanism of β-elemene is to inhibit tumor growth and proliferation, induce apoptosis, inhibit tumor cell invasion and metastasis, enhance the sensitivity of chemoradiotherapy, regulate the immune system, and reverse multidrug resistance (MDR). Elemene oral emulsion and elemene injection were approved by the China Food and Drug Administration (CFDA) for the treatment of various cancers and bone metastasis in 1994. However, the lipophilicity and low bioavailability limit its application. To discover better β-elemene-derived anti-tumor drugs with satisfying drug-like properties, researchers have modified its structure under the premise of not damaging the basic scaffold structure. In this review, we comprehensively discuss and summarize the potential anti-tumor mechanisms and the progress of structural modifications of β-elemene.

Enhanced Photothermal-Photodynamic Therapy by Indocyanine Green and Curcumin-Loaded Layered MoS2 Hollow Spheres via Inhibition of P-Glycoprotein

PURPOSE

P-glycoprotein (P-gp), which is highly expressed in liver cancer cells, is one of the obstacles for the treatment of cancer. In this study, we have prepared and characterized a kind of novel ICG&Cur@MoS2 (ICG and Cur represent indocyanine green and curcumin, respectively) nanoplatform, which can achieve photothermal-photodynamic therapy and inhibit the P-gp effectively and safely.

METHODS

In this work, plenty of studies including drug release, acute toxicity, Western blot, real-time PCR, cell viability, therapeutic experiment in vivo, immunofluorescence and so on were conducted to test the antitumor potential of ICG&Cur@MoS2 and the inhibitory effect of curcumin on P-gp.

RESULTS

The ICG&Cur@MoS2 NPs exhibit an excellent photothermal effect and relatively low toxicity. Cell viability in the ICG&Cur@MoS2 + NIR group was significantly lower than that in ICG@MoS2 + NIR group (75.3% vs 81.2%, 59.0% vs 64.4%, 20.3% vs 27.5%, and 15.4% vs 22.3%) at the concentration of ICG at 0.5, 5, 25, 50 μg/mL (P<0.05 at each concentration). Western blot, Q-PCR, and immunofluorescence assay indicate ICG&Cur@MoS2 NPs can inhibit the P-gp effectively and safely. In vivo, the tumors in the ICG@MoS2 + NIR group are significantly smaller than those in the MoS2 + NIR group (95.0 vs 420.9 mm3, p<0.05).

CONCLUSION

In conclusion, we have successfully synthesized ICG&Cur@MoS2 nanoparticles which can not only achieve PTT-PDT but also inhibit P-gp effectively. Our findings indicate that the PTT-PDT exhibits great potential in the treatment of hepatocellular carcinoma. Meanwhile, ICG&Cur@MoS2 can effectively inhibit the expression of P-gp, which will enhance the PDT effect.

MOF Regulates TNK2 Transcription Expression to Promote Cell Proliferation in Thyroid Cancer

MOF is a well-known histone acetyltransferase to catalyze acetylation of histone H4 lysine 16 (K16), and it is relevant to diverse biological processes, such as gene transcription, cell cycle, early embryonic development and tumorigenesis. Here, we identify MOF as an oncogene in most thyroid cancer. It is found that expression level of MOF was significantly upregulated in most thyroid cancer tissue samples and cell lines. MOF-deficient in both BHP-10-3 and TT2609 cell lines inhibited cell proliferation by blocking the cell cycle in G1 phase and enhanced cell apoptosis. Mechanistically, MOF bound the TNK2 promoter to activate TNK2 transcription. Furthermore, the expression level of TNK2 was decreased with the histone acetyltransferase inhibitor. Besides, MOF promoted proliferation of thyroid cancer cells through increased phosphorylation of AKT, thus activating the PI3K/AKT pathway. Ultimately, our findings indicated that MOF played an oncogene role in development and progression of thyroid cancer and may be a potential novel target for the treatment of thyroid cancer.

Molecular Bases of Mechanisms Accounting for Drug Resistance in Gastric Adenocarcinoma

Gastric adenocarcinoma (GAC) is the most common histological type of gastric cancer, the fifth according to the frequency and the third among the deadliest cancers. GAC high mortality is due to a combination of factors, such as silent evolution, late clinical presentation, underlying genetic heterogeneity, and effective mechanisms of chemoresistance (MOCs) that make the available antitumor drugs scarcely useful. MOCs include reduced drug uptake (MOC-1a), enhanced drug efflux (MOC-1b), low proportion of active agents in tumor cells due to impaired pro-drug activation or active drug inactivation (MOC-2), changes in molecular targets sensitive to anticancer drugs (MOC-3), enhanced ability of cancer cells to repair drug-induced DNA damage (MOC-4), decreased function of pro-apoptotic factors versus up-regulation of anti-apoptotic genes (MOC-5), changes in tumor cell microenvironment altering the response to anticancer agents (MOC-6), and phenotypic transformations, including epithelial-mesenchymal transition (EMT) and the appearance of stemness characteristics (MOC-7). This review summarizes updated information regarding the molecular bases accounting for these mechanisms and their impact on the lack of clinical response to the pharmacological treatment currently used in GAC. This knowledge is required to identify novel biomarkers to predict treatment failure and druggable targets, and to develop sensitizing strategies to overcome drug refractoriness in GAC.

PD-L1 Under Regulation of miR-429 Influences the Sensitivity of Gastric Cancer Cells to TRAIL by Binding of EGFR

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has received extensive attention as a cancer therapeutic due to its high propensity for tumor targeting with minimal toxicity to healthy tissue. Gastric cancer (GCa) cells show high levels of TRAIL resistance. Epidermal growth factor receptor (EGFR) antagonizes TRAIL-induced apoptosis, but the mechanisms of these effects remain unclear. Our past research confirmed TRAIL-resistant (BGC823 and SGC7901) and TRAIL-sensitive cells (HGC27 and MKN45). miR-429 associated with TRAIL sensitivity was screened using microRNA arrays. The transfection of mimics and inhibitors confirmed that miR-429 negatively correlated with GCa TRAIL resistance. The target gene of miR-429 was identified as PD-L1, which positively correlated with TRAIL resistance through gene silencing and recovery experiments. Using co-immunoprecipitation (co-IP) and proximity ligation assay, we demonstrated that the pro-survival effects of PD-L1 are mediated through the binding and activation of EGFR. Cell viability experiments demonstrated that PD-L1 is key to the maintenance of cell viability in TRAIL-treated cells. This indicated that PD-L1 binds to and participates in EGFR activation through miR-429 regulation to antagonize TRAIL-induced apoptosis. This provides a new theoretical basis for the combination of the EGFR monoclonal antibodies including cetuximab, PD-L1 inhibitors, and human recombinant TRAIL in gastric cancer therapy and can filter patients who are currently sensitive to TRAIL treatment.

Sur-X, a novel peptide, kills colorectal cancer cells by targeting survivin-XIAP complex

Background

Survivin and XIAP are two important members of the inhibitor of apoptosis protein family and have been considered as potential targets for cancer treatment due to their overexpression in large variety of cancers including colorectal cancer. It has been reported that survivin and XIAP can synergistically inhibit apoptosis by forming survivin-XIAP complex. In this study, we aimed to design a peptide that targets the survivin-XIAP complex and elucidate its anticancer mechanisms in colorectal cancer cells.

Methods

We designed and synthetized Sur-X, the peptide targeting survivin-XIAP complex. The anticancer effects of Sur-X were evaluated both in vitro and in vivo. The underlying molecular mechanisms were also investigated.

Results

Sur-X exhibited potent inhibitory effects on four colorectal cancer cell lines HCT116, HCT15, RKO and HT29, but not on human peritoneal mesothelial cell line HMrSV5. Mechanistically, Sur-X induced Caspase 9-dependent intrinsic apoptosis in colorectal cancer cells by disrupting the survivin-XIAP complex and subsequently destabilizing survivin and XIAP. Interestingly, we found that Sur-X can also promote necroptosis. It was demonstrated that Sur-X destroyed the interaction between XIAP and TAB1 in the XIAP-TAB1-TAK1 complex, leading to the instability of TAK1, an endogenous necroptosis inhibitor. Subsequently, the accelerated degradation of TAK1 attenuated its inhibition on necroptosis in colorectal cancer cells. Moreover, knockdown of TAK1 restored the sensitivity of TAB1-overexpressing colorectal cancer cells to Sur-X-induced necroptosis. The in vivo pro-apoptotic effect of Sur-X was confirmed by the enhanced TUNEL staining and the decreased expression of survivin and XIAP in tumor tissues from xenograft mouse models. In addition, extensive necrosis and weaker MLKL expression in xenografts provided evidence for the in vivo pro-necroptotic effect of Sur-X.

Conclusions

Peptide Sur-X exhibits strong pro-apoptotic and pro-necroptotic effects in colorectal cancer cells and has a high clinical translation potential in the treatment of colorectal cancer.

A thiazole-derived oridonin analogue exhibits antitumor activity by directly and allosterically inhibiting STAT3

Constitutive activation of signal transducer and activator of transcription 3 (STAT3) occurs in ∼70% of human cancers, and STAT3 is regarded as one of the most promising targets for cancer therapy. However, specific direct STAT3 inhibitors remain to be developed. Oridonin is an ent-kaurane plant-derived diterpenoid with anti-cancer and anti-inflammatory activities. Here, using an array of cell-based and biochemical approaches, including cell proliferation and apoptosis assays, pulldown and reporter gene assays, site-directed mutagenesis, and molecular dynamics analyses, we report that a thiazole-derived oridonin analogue, CYD0618, potently and directly inhibits STAT3. We found that CYD0618 covalently binds to Cys-542 in STAT3 and suppresses its activity through an allosteric effect, effectively reducing STAT3 dimerization and nuclear translocation, as well as decreasing expression of STAT3-targeted oncogenes. Remarkably, CYD0618 not only strongly inhibited growth of multiple cancer cell lines that harbor constitutive STAT3 activation, but it also suppressed in vivo tumor growth via STAT3 inhibition. Taken together, our findings suggest Cys-542 as a druggable site for selectively inhibiting STAT3 and indicate that CYD0618 represents a promising lead compound for developing therapeutic agents against STAT3-driven diseases.

Exosome-mediated transfer of CLIC1 contributes to the vincristine-resistance in gastric cancer

Our previous study shows that high Chloride intracellular channel 1 (CLIC1) expression can efficiently enhance invasion and migration of gastric cancer (GC) cells in vitro. Growing evidences have found that exosomes are involved in chemotherapy resistance in several cancers including GC. We aimed to evaluate the effect of the exosome-mediated transfer of CLIC1 in the vincristine-resistance of GC. The effect of exosome-mediated transfer of CLIC1 on the development of resistance to vincristine in GC cell line SGC-7901 and the potential underlying mechanisms were investigated by Cell Counting Kit-8 (CCK8), RT-PCR, and Western blotting. Exosomes were isolated from cell supernatants by differential ultracentrifugation. Comparing with SGC-7901, the expression level of CLIC1 is higher in vincristine‑resistant cell line SGC-7901/VCR (P < 0.05). After silencing the expression of CLIC1 by RNA interference, the half inhibition concentration (IC50) to vincristine decreased significantly in SGC-7901/VCR, and the expression of CLIC1 decreased significantly in exosomes from SGC-7901/VCR. After 48 h co-culturing with exosomes from SGC-7901/VCR, the IC50 to vincristine in SGC-7901 increased significantly, and the expression of CLIC1, P-gp, and Bcl-2 were significantly up-regulated. CLIC1 was closely associated with the resistance to vincristine in GC, and exosome-mediated transfer of CLIC1 could induce the development of resistance to vincristine in vitro. The possible mechanism was related to up-regulated P-gp and Bcl-2. However, in vivo study was needed to confirm the results in future.

Hydrogen Gas in Cancer Treatment

Gas signaling molecules (GSMs), composed of oxygen, carbon monoxide, nitric oxide, hydrogen sulfide, etc., play critical roles in regulating signal transduction and cellular homeostasis. Interestingly, through various administrations, these molecules also exhibit potential in cancer treatment. Recently, hydrogen gas (formula: H₂) emerges as another GSM which possesses multiple bioactivities, including anti-inflammation, anti-reactive oxygen species, and anti-cancer. Growing evidence has shown that hydrogen gas can either alleviate the side effects caused by conventional chemotherapeutics, or suppress the growth of cancer cells and xenograft tumor, suggesting its broad potent application in clinical therapy. In the current review, we summarize these studies and discuss the underlying mechanisms. The application of hydrogen gas in cancer treatment is still in its nascent stage, further mechanistic study and the development of portable instruments are warranted.

Discovery of cancer cell proliferation inhibitors from Salviae miltiorrhizae radix et rhizoma by a trace peak enrichment approach

Salviae miltiorrhizae radix et rhizoma is a traditional herbal medicine with anti-cancer activities. In this work, a trace peak enrichment approach combined with a cell proliferation assay was applied for screening cancer cell proliferation inhibitors from the extract of S. miltiorrhiza. A set of 123 peak fractions were prepared, and by comprehensive screening, 21 tanshinones were screened out as cancer cell proliferation inhibitors and their structures were tentatively identified by liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry analysis. The inhibitory activities of nine available screened tanshinones were validated, with their IC₅₀ values ranging from 0.63 to 28.40 μM, indicating their activities strongly inhibit the proliferation of cancer cells. This study presents tanshinones that are potential cancer cell proliferation inhibitors and may explain the anti-cancer activity of S. miltiorrhiza.

FBXL7 Upregulation Predicts a Poor Prognosis and Associates with a Possible Mechanism for Paclitaxel Resistance in Ovarian Cancer

Paclitaxel (PTX) is a common regimen used to treat patients with ovarian cancer. Although approximately 60% of ovarian cancer patients exhibit a pathologic complete response (pCR), approximately 40% of patients appear to be insensitive to PTX adjuvant therapy. Thus, identifying a useful biomarker to predict pCR would be of great help to ovarian cancer patients who decide to receive PTX treatment. We found that FBXL7 was downregulated in OVSAHO (PTX-sensitive) but upregulated in KURAMOCHI (PTX-resistant) cells after PTX treatment at cytotoxic concentrations. Moreover, our data showed that the fold change of FBXL7 expression post-treatment with PTX was causally correlated with the 50% inhibitory concentrations (IC₅₀) of PTX in a panel of ovarian cancer cell lines. In assessments of progression-free survival probability, high levels of FBXL7 transcript strongly predicted a poor prognosis and unfavorable response to PTX-based chemotherapy in patients with ovarian cancer. The knockdown of FBXL7 predominantly enhanced the cytotoxic effectiveness of PTX on the PTX-resistant KURAMOCHI cells. FBXL7 may be a useful biomarker for predicting complete pathologic response in ovarian cancer patients who decide to receive post-operative PTX therapy.

1,3-dimethyl-6-nitroacridine derivatives induce apoptosis in human breast cancer cells by targeting DNA

The acridine derivatives can interact with the double-stranded DNA, which is regarded as the biological target of the anticancer drugs in cancer treatment. We designed and synthesized a new series of 1,3-dimethyl-6-nitroacridine derivatives as potential DNA-targeted anticancer agents. These compounds could partially intercalate into the calf thymus DNA, differing from the parent acridine. The results showed that the substitutions of the acridine ring had great effect on DNA binding affinity. The binding constants determined by UV-vis spectroscopy were found to be 10⁵ M^-1 grade. Anticancer activity of these compounds was screened using MTT assay. Most compounds inhibited 50% cancer cell growth at concentration below 30 μM, the results were consistent with the DNA binding ability. Compounds 1 and 6 were found to have more effective cytotoxicity, especially in human breast cancer cell lines. To investigate the action mechanism, we studied cell apoptosis, morphological changes, and cell cycle distribution in MCF-7 and MDA-MB-231 cells. Compounds 1 and 6 caused MCF-7 and MDA-MB-231 cells death due to apoptosis, and induced cell apoptosis in a dose-dependent manner. They also had significant effect on cell cycle progression and arrested cell cycle at G2/M phase. The results demonstrated that compounds 1 and 6 are promising candidates for cancer treatment.

MicroRNA-128 contributes to the progression of gastric carcinoma through GAREM-mediated MAPK signaling activation

Gastric carcinoma (GC) represents the most common malignant cancer and the second leading cause of cancer death worldwide. However, the molecular mechanisms and biological progression of GC remain unknown. In this study, we found that miR-128 is a critical tumor suppressor that is downregulated in GC patients and GC cells and that GAREM is a direct downstream target of miR-128. Overexpression of miR-128 in HGC-27 and MKN-45 cells resulted in suppressed cell growth and promoted cell apoptosis through a GAREM-dependent mechanism. Moreover, the precise mechanisms underlying the antitumor effect of miR-128 in GC are at least partially due to suppressing activation of the MAPK signaling pathway, induced by suppressing GAREM expression. This study is the first to demonstrate that the miR-128-GAREM-MAPK signaling pathway forms a critical feedback loop and mediates GC development, and these findings might demonstrate a potential therapeutic strategy for GC.

2-aryl benzimidazole conjugate induced apoptosis in human breast cancer MCF-7 cells through caspase independent pathway

Apoptosis is a representative form of programmed cell death, which has been assumed to be critical for cancer prevention. Thus, any agent that can induce apoptosis may be useful for cancer treatment and apoptosis induction is arguably the most potent defense against cancer promotion. In our previous studies, 2-aryl benzimidazole conjugates were synthesized and evaluated for their antiproliferative activity and one of the new molecule (2f) was considered as a potential lead. This lead molecule showed significant antiproliferative activity against human breast cancer cell line, MCF-7. The results of the present study revealed that this compound arrested the cell cycle at G2/M phase. Topoisomerase II inhibition assay and Western blot analysis suggested that this compound effectively inhibits topoisomerase II activity which leads to apoptotic cell death. Apoptosis induction in MCF-7 cells was further confirmed by loss of mitochondrial membrane potential (∆Ψm), release of cytochrome c from mitochondria, an increase in the level of apoptosis inducing factor (AIF), generation of reactive oxygen species (ROS), up regulation of proapoptotic protein Bax and down regulation of anti apoptotic protein Bcl-2. Apoptosis assay using Annexin V-FITC assay also suggested that this compound induced cell death by apoptosis. However, compound 2f induced apoptosis could not be reversed by Z-VAD-FMK (a pan-caspase inhibitor) demonstrated that the 2f induced apoptosis was caspase independent. Further, 2f treatment did not activate caspase-7 and caspase-9 activity, suggesting that this compound induced apoptosis in breast cancer cells via a caspase independent pathway. Most importantly, this compound was less toxic towards non-tumorigenic breast epithelial cells, MCF-10A. Furthermore, docking studies also support the potentiality of this molecule to bind to the DNA topoisomerase II.

c-FLIP is a target of the E3 ligase deltex1 in gastric cancer

The ubiquitin E3 ligase DELTEX1 (DTX1) is specifically downregulated in gastric cancer tissues, and expression of DTX1 is linked to better prognoses and survival in gastric cancer. Cellular FLICE inhibitory protein (c-FLIP) is known for its pivotal role in the resistance of cancer cells to death receptor-induced cell death. Here, we show that DTX1 is an E3 ligase for c-FLIP in gastric cancer cells. DTX1 promoted c-FLIP downregulation. Overexpression of DTX1 sensitized gastric cancer cells to TRAIL-induced apoptosis, whereas DTX1-knockdown attenuated apoptosis induction. DTX1 binds c-FLIP_L and directs it into the endosome-lysosomal pathway for proteasome-independent degradation. Moreover, induction of DTX1 in AGS cells by geldanamycin conferred susceptibility of those cells to TRAIL-induced apoptosis. Our results reveal a tumor-suppressive role for DTX1 and suggest a new approach to increasing TRAIL efficacy by raising DTX1 levels in gastric cancer therapy. DTX1 also enhanced c-FLIP degradation and FasL-induced and TRAIL-induced apoptosis in T cells, suggesting that DTX1 constitutes one of the physiological mechanisms regulating c-FLIP stability.

Anti-tumor bioactivities of curcumin on mice loaded with gastric carcinoma

Curcumin, a derivative from the dried rhizome of curcuma longa, has been proven to possess anti-tumor effects. However, the detailed molecular mechanisms have not been fully elucidated. In this study, we aimed to explore the anti-tumor mechanisms of curcumin in treating gastric cancer. BALB/C mice grafted with a mouse gastric adenocarcinoma cell line (MFC) were used as the experimental model. Mice received different doses of curcumin after grafting. Tumor size was measured and tumor weight was determined after tumor inoculation. TUNEL assay and flow cytometric analysis were applied to evaluate the apoptosis of the cancer cells. Serum cytokines IFN-γ, TNF-α, granzyme B and perforin were detected by ELISA assay. The anti-tumor effect was determined using cytotoxic T-lymphocyte (CTL) assays and in vivo tumor prevention tests. The expression of DEC1, HIF-1α, STAT3 and VEGF in tumor tissues was examined by immunostaining and analyzed using an Image J analysis system. Compared with controls, tumor growth (size and weight) was significantly inhibited by curcumin treatment (P < 0.05). The apoptotic index in gastric cancer cells was significantly increased in the curcumin treatment group. Splenocyte cells from mice treated with curcumin exhibited higher cytolytic effects on MFC cancer cells than those from mice treated with saline (P < 0.01). The expression of DEC1, HIF-1α, STAT3 and VEGF in tumor tissues was down-regulated after curcumin treatment. Our results indicate that curcumin inhibits the proliferation of gastric carcinoma by inducing the apoptosis of tumor cells, activating immune cells to secrete a large amount of cytokines, and down-regulating the DEC1, HIF-1α, VEGF and STAT3 signal transduction pathways.

Protein profiling of alpha-fetoprotein producing gastric adenocarcinoma

Alpha-fetoprotein (AFP) producing gastric adenocarcinoma is considered as a rare subtype of gastric adenocarcinoma. Compared with AFP non-producing gastric adenocarcinoma, our study and other previous studies showed that AFP producing gastric adenocarcinoma is more aggressive and prone to liver metastasis. Using the Protein Pathway Array, 11 of out of 286 proteins tested were found to be differentially expressed between AFP producing (n=32) and AFP non-producing (n=45) gastric adenocarcinoma tissues. In addition, the high level expression of XIAP and IGF-Irβ in gastric adenocarcinoma tissues was independent factors for poor prognosis in AFP producing gastric adenocarcinoma patients. A risk model based on the XIAP and IGF-Irβ expression levels can separate AFP producing gastric adenocarcinoma patients into 2 subgroups and each subgroup had a distinct set of signaling pathways involved. In conclusion, AFP producing gastric adenocarcinoma is a heterogeneous cancer with different clinical outcomes, biological behaviors and underlying molecular alterations.

Cytotoxicity and apoptotic cell death induced by Vitis vinifera peel and seed extracts in A431 skin cancer cells

Vitis vinifera. L is one of the most widely consumed fruits in the world and are rich in antioxidant abundant polyphenols. The present study was carried out to assess the antiproliferative and apoptotic effects of Vitis vinifera peel and seed extracts in an in vitro model using human epidermoid carcinoma A431 cell lines. Vitis vinifera peel and seed extracts were incubated with A431 cells to evaluate the antiproliferative, apoptotic effects and the morphological apoptotic changes induced by the extracts. Mitochondrial membrane potential was also measured after incubating the cells with extracts. At the inhibitory concentration (IC₅₀), grape seed extract (111.11 µg/mL) and grape peel extract (319.14 µg/mL) were incubated for 24 h with A431 cells. Vitis vinifera peel and seed extracts were able to impart cytotoxic effects, induced apoptosis and apoptotic morphological changes in A431 cells significantly (p < 0.01) and this effect is associated with the interference with mitochondrial membrane potential. This reduction in mitochondrial membrane potential probably initiated the apoptotic cascade in the extracts treated cells. Vitis vinifera peel and seed phytochemicals can selectively target cancer cells and the phytochemicals that are occluded can serve as potential anticancer agents providing better efficacy in killing cancer cells.

An Ursolic Acid Derived Small Molecule Triggers Cancer Cell Death through Hyperstimulation of Macropinocytosis

Macropinocytosis is a transient endocytosis that internalizes extracellular fluid and particles into vacuoles. Recent studies suggest that hyperstimulation of macropinocytosis can induce a novel nonapoptotic cell death, methuosis. In this report, we describe the identification of an ursolic acid derived small molecule (compound 17), which induces cancer cell death through hyperstimulation of macropinocytosis. 17 causes the accumulation of vacuoles derived from macropinosomes based on transmission electron microscopy, time-lapse microscopy, and labeling with extracellular fluid phase tracers. The vacuoles induced by 17 separate from other cytoplasmic compartments but acquire some characteristics of late endosomes and lysosomes. Inhibiting hyperstimulation of macropinocytosis with the specific inhibitor amiloride blocks cell death, implicating that 17 leads to cell death via macropinocytosis, which is coincident with methuosis. Our results uncovered a novel cell death pathway involved in the activity of 17, which may provide a basis for further development of natural-product-derived scaffolds for drugs that trigger cancer cell death by methuosis.

Aurora kinase A regulates Survivin stability through targeting FBXL7 in gastric cancer drug resistance and prognosis

Aurora kinase A (AURKA) has been implicated in the regulation of cell cycle progression, mitosis and a key number of oncogenic signaling pathways in various malignancies. However, little is known about its role in gastric cancer prognosis and genotoxic resistance. Here we found that AURKA was highly overexpressed in gastric cancer and inversely correlated with disease prognosis. Overexpression of AURKA exacerbated gastric cancer drug resistance through upregulating the expression of the anti-apoptotic protein Survivin. Conversely, we demonstrated that AURKA depletion caused a decrease in Survivin protein levels by increasing its ubiquitylation and degradation. Mass spectrometric analysis revealed that upon AURKA depletion, Survivin bound to the FBXL7 E3 ubiquitin ligase, which induced ubiquitin-proteasome degradation of Survivin. In addition, we showed that AURKA regulated FBXL7 both at the levels of transcription and translation. Moreover, proteomic analysis of nuclear AURKA-interacting proteins identified Forkhead box protein P1 (FOXP1). We next showed that AURKA was required for FBXL7 transcription and that AURKA negatively regulated FOXP1-mediated FBXL7 expression. The physiological relevance of the regulation of Survivin by AURKA through the FOXP1–FBXL7 axis was further underscored by the significant positive correlations between AURKA and Survivin expression in gastric cancer patient samples. Moreover, the AURKA depletion or kinase inhibition-induced apoptotic cell death could be reversed by Survivin ectopic overexpression, further supporting that AURKA regulated Survivin to enhance drug resistance. In agreement, inhibition of AURKA synergistically enhanced the cytotoxic effect of DNA-damaging agents in cancer cells by suppressing Survivin expression. Taken together, our data suggest that AURKA restricts Survivin ubiquitylation and degradation in gastric cancer to promote drug resistance and hence the AURKA–Survivin axis can be targeted to promote the efficacy of DNA-damaging agents in gastric cancer.

Cordycepin induces apoptosis in SGC‑7901 cells through mitochondrial extrinsic phosphorylation of PI3K/Akt by generating ROS

Medicinal plants are affluent sources of several effectual natural drugs. Among them cordycepin which is extracted from Cordyceps militaris is a hopeful chemotherapy agent due to its extensive anti-inflammatory, anti-proliferative, antioxidant, and antitumor characteristics. This study investigated the efficacy of cordycepin in the context of human gastric cancer SGC‑7901 and searched for the cell death procedure. Cordycepin incorporates mitochondrial-mediated apoptosis in SGC‑7901 cells with the help of regulating mitochondrial extrinsic pathways by inhibition of A3AR and drive activation of DR3, which promote the activation of PI3K/Akt protein expression as well as collapse of mitochondrial membrane potential (MMP). In addition, phosphorylation of PI3K/Akt and DNA damage by cordycepin induced the production of reactive oxygen species (ROS), and mediates SGC‑7901 cell cycle cessation at S phase. Collectively, this study suggests that cordycepin might be effective as a modern chemotherapy drug for gastric cancer.

MiR-106a: Promising biomarker for cancer

MicroRNAs (miRNAs), which are characterized by highly conserved and small non-coding RNAs, have been a hot spot regarding biological processes such as cellular proliferation, apoptosis and metabolism as well as cellular differentiation, signal transduction and carcinogenesis. MiRNA-106a (miR-106a), a member of the miR-17 family, has been validated to be aberrantly regulated in the diversity of tumors. The purpose of this review is supposed to deliver an intricate overview of miR-106a, including its role in cell proliferation, apoptosis, cell cycle, invasion and metastasis, involvement in drug resistance as well as its interactions with the target proteins and signaling pathways involved.

Potential Diagnostic, Prognostic and Therapeutic Targets of MicroRNAs in Human Gastric Cancer

Human gastric cancer (GC) is characterized by a high incidence and mortality rate, largely because it is normally not identified until a relatively advanced stage owing to a lack of early diagnostic biomarkers. Gastroscopy with biopsy is the routine method for screening, and gastrectomy is the major therapeutic strategy for GC. However, in more than 30% of GC surgical patients, cancer has progressed too far for effective medical resection. Thus, useful biomarkers for early screening or detection of GC are essential for improving patients’ survival rate. MicroRNAs (miRNAs) play an important role in tumorigenesis. They contribute to gastric carcinogenesis by altering the expression of oncogenes and tumor suppressors. Because of their stability in tissues, serum/plasma and other body fluids, miRNAs have been suggested as novel tumor biomarkers with suitable clinical potential. Recently, aberrantly expressed miRNAs have been identified and tested for clinical application in the management of GC. Aberrant miRNA expression profiles determined with miRNA microarrays, quantitative reverse transcription-polymerase chain reaction and next-generation sequencing approaches could be used to establish sample specificity and to identify tumor type. Here, we provide an up-to-date summary of tissue-based GC-associated miRNAs, describing their involvement and that of their downstream targets in tumorigenic and biological processes. We examine correlations among significant clinical parameters and prognostic indicators, and discuss recurrence monitoring and therapeutic options in GC. We also review plasma/serum-based, GC-associated, circulating miRNAs and their clinical applications, focusing especially on early diagnosis. By providing insights into the mechanisms of miRNA-related tumor progression, this review will hopefully aid in the identification of novel potential therapeutic targets.

Hwang-Heuk-San induces apoptosis in HCT116 human colorectal cancer cells through the ROS-mediated activation of caspases and the inactivation of the PI3K/Akt signaling pathway

Hwang-Heuk-San (HHS) is a polyherbal formulation that has been used in traditional Korean medicine for hundreds of years to treat gastrointestinal malignancy. However, to date, the mechanisms responsible for the anticancer effects remain unclear. In the present study, we investigated the anticancer effects of HHS using HCT116 human colorectal cancer (CRC) cells. Our results showed that HHS treatment significantly reduced cell survival and increased apoptotic cell death in a concentration-dependent manner. The treatment of HCT116 cells with HHS also significantly elevated the accumulation of reactive oxygen species (ROS), which was followed by the attenuation of the mitochondrial membrane potential through the upregulation of Bax and the downregulation of Bcl-2, which was accompanied by the release of cytochrome c to the cytosol. In addition, HHS treatment caused the truncation of Bid and activated the caspases (caspase-8, -9 and -3), which was associated with the induction of the Fas ligand, the death receptors (DRs), DR4 and DR5, downregulation of the inhibitors of protein expression in the apoptosis protein family, and the degradation of poly(ADP-ribose)-polymerase. However, a pan-caspase inhibitor reversed the HHS-induced apoptosis and growth suppression, indicating that HHS induces apoptosis though a caspase-dependent intrinsic and extrinsic apoptotic pathway in HCT116 cells. Moreover, HHS treatment inhibited the activation of phosphatidylinositol-3-kinase (PI3K)/Akt signaling, and a pharmacological inhibitor of PI3K significantly potentiated the apoptotic effects of HHS when employed in combination in HCT116 cells. Furthermore, the blocking of ROS generation by antioxidant N-acetyl cysteine attenuated the HHS-induced release of cytochrome c, caspase activation and PI3K/Akt inactivation, thereby preventing HHS-induced apoptosis and reduction in cell viability. These findings suggest that HHS-induced ROS generation is required for caspase-dependent apoptotic cell death involving inhibition of the PI3K/Akt signaling pathway in HCT116 cells. Overall, our findings suggest that HHS may be an effective treatment for CRC cancer, and further studies are required to identify the active compounds in HHS.

Promoter hypermethylation and downregulation of the FAS gene may be involved in colorectal carcinogenesis

Aberrant DNA methylation has been investigated in carcinogenesis and as biomarker for the early detection of colorectal cancer (CRC). The present study aimed to define the methylation status in the regulatory elements of two proapoptotic genes, Fas cell surface death receptor (FAS) and BCL2-associated X protein (BAX). DNA methylation analysis was performed in tumor and adjacent normal tissue using HpaII/MspI restriction digestion and methylation-specific polymerase chain reaction (PCR). The results observed downregulation of the FAS and BAX genes in the CRC tissues compared with the adjacent normal samples. Furthermore, demethylation using 5-aza-2'-deoxycytidine treatment followed by reverse-transcription quantitative PCR were performed on the HT-29 cell line to measure BAX and FAS mRNA expression following demethylation. The 5-aza-2'-deoxycytidine treatment resulted in significant FAS gene upregulation in the HT-29 cell line, but no significant difference in BAX expression. Furthermore, analysis of CpG islands in the FAS gene promoter revealed that the FAS promoter was significantly hypermethylated in 53.3% of tumor tissues compared with adjacent normal samples. Taken together, the results indicate that decreased expression of the FAS gene due to hypermethylation of its promoter may lead to apoptotic resistance, and acts as an important step during colorectal carcinogenesis.

3-β-Εrythrodiol isolated from Conyza canadensis inhibits MKN‑45 human gastric cancer cell proliferation by inducing apoptosis, cell cycle arrest, DNA fragmentation, ROS generation and reduces tumor weight and volume in mouse xenograft model

The objective of the present study was to investigate the in vitro and in vivo anticancer and apoptotic effects of 3-β-erythrodiol, a plant-derived triterpene against MKN-45 human gastric cancer cells. In addition, effects on cellular morphology, cell cycle phase distribution, DNA fragmentation, and ROS generation were also elucidated in the current research work. Cytotoxic activity of 3-β-erythrodiol was demonstrated by MTT cell viability and LDH assay. Cellular morphological study was carried out using phase contrast, fluorescence and scanning electron microscopy. Cell cycle analysis was evaluated by flow cytometry and gel electrophoresis was used to evaluate DNA fragmentation pattern. The results of the present study revealed that 3-β-erythrodiol induced dose-dependent as well as time-dependent anticancer effects in MKN-45 gastric cancer cells. Cellular morphological changes in MKN-45 cells as indicated by fluorescence and scanning electron microscopy were induced by 3-β-erythrodiol. This triterpene induced both early and late apoptotic features in these cancer cells. 3-β-Erythrodiol treatment led to sub-G1 cell cycle arrest with a corresponding decrease in S-phase cells and an increase in G2/M phase cells. DNA fragments were evident in gel electrophoresis experiment following 3-β-erythrodiol treatment. It was observed that 0.50 and 1.0 µg/g 3-β-erythrodiol injection reduced the tumor weight from 1.4 g in PBS-treated group (control) to 0.61 and 0.22 g, respectively. Similarly, 0.50 and 1.0 µg/g 3-β-erythrodiol injection reduced the tumor volume from 1.5 cm3 in PBS-treated group (control) to 0.91 and 0.31 cm3, respectively. The present investigation indicates that 3-β-erythrodiol exerts anti-proliferative effects in human gastric cancer by inducing early and late apoptosis, cell cycle arrest, and ROS generation. It also decreased the tumor volume and tumor weight in male Balb/c nude mice.