Beclin 1 expression is an independent prognostic factor for gastric carcinomas

MicroRNAs as the critical regulators of autophagy-mediated cisplatin response in tumor cells

Chemotherapy is one of the most common therapeutic methods in advanced and metastatic tumors. Cisplatin (CDDP) is considered as one of the main first-line chemotherapy drugs in solid tumors. However, there is a high rate of CDDP resistance in cancer patients. Multi-drug resistance (MDR) as one of the main therapeutic challenges in cancer patients is associated with various cellular processes such as drug efflux, DNA repair, and autophagy. Autophagy is a cellular mechanism that protects the tumor cells toward the chemotherapeutic drugs. Therefore, autophagy regulatory factors can increase or decrease the chemotherapy response in tumor cells. MicroRNAs (miRNAs) have a pivotal role in regulation of autophagy in normal and tumor cells. Therefore, in the present review, we discussed the role of miRNAs in CDDP response through the regulation of autophagy. It has been reported that miRNAs mainly increased the CDDP sensitivity in tumor cells by inhibition of autophagy. PI3K/AKT signaling pathway and autophagy-related genes (ATGs) were the main targets of miRNAs in the regulation of autophagy-mediated CDDP response in tumor cells. This review can be an effective step to introduce the miRNAs as efficient therapeutic options to increase autophagy-mediated CDDP sensitivity in tumor cells.

Neuroprotective Effects of Long-Term Metformin Preconditioning on Rats with Ischemic Brain Injuries

INTRODUCTION

This study is to analyze the neuroprotective effects of long-term metformin (Met) preconditioning on rats with ischemic brain injuries and the related mechanisms.

METHODS

Twenty-five Sprague-Dawley rats were randomly divided into 5 groups: sham group, middle cerebral artery occlusion (MCAO) group, normal saline + MCAO group, pre- Met + MCAO group, and 3-MA + Met + MCAO group. Pathological changes of brain were observed by hematoxylin-eosin staining. Neurobehavior scores were calculated. Infarct area was assessed by 2,3,5-triphenyltetrazolium chloride staining. Apoptosis of neurons was detected by TdT-mediated dUTP Nick-End Labeling (TUNEL). Western blot tested the expression of LC3 (microtubule-associated protein 1 light chain 3), Beclin-1, adenosine 5'-monophosphate ([AMP]-activated protein kinase [AMPK]), and p-AMPK in hippocampal CA1 region.

RESULTS

Compared with the sham group, the MCAO group induced severe pathological changes in the brain. The neurobehavior scores and infarct area in the brain were increased in the MCAO group than in the sham group. The apoptosis level in the MCAO group was also higher than in the sham group. However, after pretreatment with Met, the pathological changes in the brain were attenuated. Compared with the MCAO group, the pre-Met + MCAO group also had decreased neurobehavior scores and infarct area in the brain. Additionally, the apoptosis level in the pre-Met + MCAO group was lower than in the MCAO group. Moreover, the MCAO group had increased levels of LC3 and Beclin-1 than in the sham group. In the pre-Met + MCAO group, their levels were decreased than in the MCAO group. The p-AMPK level in the pre-Met + MCAO group was also increased than in the MCAO group, suggesting activation of p-AMPK by Met.

CONCLUSION

Long-term Met pretreatment has neuroprotective effect on ischemic brain injury, which may be related to the regulation of autophagy-related protein expression and apoptosis.

The Roles of Beclin 1 Expression in Gastric Cancer: A Marker for Carcinogenesis, Aggressive Behaviors and Favorable Prognosis, and a Target of Gene Therapy

Beclin 1 is encoded by Becn1, and plays a role in tumorigenesis, neurodegeneration, apoptosis and autophagy. Here, the aggressive phenotypes and relevant proteins were examined after Beclin 1 expression was altered in gastric cancer cells. We also observed the effects of Beclin 1 on gastric carcinogenesis using Becn1 knockout mice. Finally, clinicopathological significances of Beclin 1 expression were analyzed using meta- and bioinformatics analyses. Becn1 overexpression was found to inhibit proliferation, glucose metabolism, migration and invasion of gastric cancer cells, whereas its knockdown caused the opposite effects. Beclin 1 suppressed the tumor growth by decreasing proliferation and increasing apoptosis. The heterozygous abrogation of Becn1 in gastric pit, parietal and chief cells could not cause any epithelial lesion. Beclin 1-mediated chemoresistance was closely linked to the autophagy, Bax underexpression, and the overexpression of Bcl-2, LRP1, MDR1, and ING5. Bioinformatics analysis showed higher Becn1 mRNA expression in intestinal- than diffuse-type carcinomas (P<0.05), and in male than female gastric cancer patients (P<0.05). Becn1 hyperexpression was positively associated with both overall and progression-free survival rates of the cancer patients (P<0.05). Meta-analysis showed that down-regulated Beclin 1 expression in gastric cancer was positively with lymph node metastasis, TNM staging, dedifferentiation and poor prognosis (P<0.05). Becn1-related signal pathways in gastric cancer included prostate, lung, renal, colorectal, endometrial and thyroid cancers, glioma, and leukemia, the metabolism of amino acid, lipid and sugar, and some signal pathways of insulin, MAPK, TRL, VEGF, JAK-STAT, chemokine, p53, lysosome, peroxidome and ubiquitin-mediated protein degradation (P<0.05). These suggested that Beclin 1 might be considered as a potential marker of gastric carcinogenesis, aggressiveness and prognostic prediction, and as a target of gene therapy in gastric cancer.

Acid-induced autophagy protects human gastric cancer cells from apoptosis by activating Erk1/2 pathway

Background

Acidic microenvironments exist widely in tumors. However, the specific mechanism of cancer cell survival under an acidic microenvironment remains unknown. This study aims to investigate whether acid can induce autophagy and examine the mechanism of autophagy in gastric cancer cells.

Methods

Human gastric adenocarcinoma (AGS) cells were cultured in media with different pH values in vitro and then subjected to autophagy detection under different conditions. To determine the effect of an acidic microenvironment on autophagy, we employed real-time quantitative polymerase chain reaction (PCR), Western blot, mRFP-GFP-LC3 immunofluorescence, and transmission electron microscopy (TEM) to detect the expression of various autophagy indicators. We also performed cell counting kit 8 (CCK8) and cell invasion and migration assays to examine cell viability and invasion, respectively.

Results

We found that the protein expression of autophagy markers such as LC3II/I and Beclin1 was higher in AGS cells treated with an acidic microenvironment than in control cells. The protein expression level of P62 was obviously decreased in acid-treated cells compared to that in control cells. Furthermore, the expression of Erk1/2 pathway markers, including p-Erk1/2, was also increased in response to acidic pH. Dense LC3 puncta were observed in cells cultured under acidic conditions, whereas untreated cells exhibited diffuse and weak LC3 puncta; an increased autophagy flux could also be observed. The presence of autophagosomes was observed by TEM in AGS cells subjected to low pH. Additionally, autophagy was inhibited by the autophagy inhibitor Bafilomycin A1 (Baf) and apoptosis was obviously increased. Moreover, cells exposed to an acidic microenvironment displayed facilitated growth compared with that in control cells.

Conclusions

Taken together, these results indicate that the acidic microenvironment promotes AGS cell growth by upregulating autophagy through the Erk1/2 pathway, which acts as a survival adaptation.

Glutathione S-transferases P1 protects breast cancer cell from adriamycin-induced cell death through promoting autophagy

Glutathione S-transferases P1 (GSTP1) is a phase II detoxifying enzyme and increased expression of GSTP1 has been linked with acquired resistance to anti-cancer drugs. However, most anticancer drugs are not good substrates for GSTP1, suggesting that the contribution of GSTP1 to drug resistances might not be dependent on its capacity to detoxify chemicals or drugs. In the current study, we found a novel mechanism by which GSTP1 protects human breast cancer cells from adriamycin (ADR)-induced cell death and contributes to the drug resistance. GSTP1 protein level is very low in human breast cancer cell line MCF-7 but is high in ADR-resistant MCF-7/ADR cells. Under ADR treatment, MCF-7/ADR cells showed a higher autophagy level than MCF-7 cells. Overexpression of GSTP1 in MCF-7 cells by using the DNA transfection vector enhanced autophagy and down-regulation of GSTP1 through RNA interference in MCF-7/ADR cells decreased autophagy. When autophagy was prevented, GSTP1-induced ADR resistance reduced. We found that GSTP1 enhanced autophagy level in MCF-7 cells through interacting with p110α subunit of phosphatidylinositol-3-kinase (PI3K) and then inhibited PI3K/protein kinase B (AKT)/mechanistic target of rapamycin (mTOR) activity. Proline123, leucine160, and glutamine163, which located in C terminal of GSTP1, are essential for GSTP1 to interact with p110α, and the following autophagy and drug resistance regulation. Taken together, our findings demonstrate that high level of GSTP1 maintains resistance of breast cancer cells to ADR through promoting autophagy. These new molecular insights provide an important contribution to our better understanding the effect of GSTP1 on the resistance of tumors to chemotherapy.

Autophagy and its role in gastric cancer

Autophagy, which is tightly regulated by a series of autophagy-related genes (ATGs), is a vital intracellular homeostatic process through which defective proteins and organelles are degraded and recycled under starvation, hypoxia or other specific cellular stress conditions. For both normal cells and tumour cells, autophagy not only sustains cell survival but can also promote cell death. Autophagy-related signalling pathways include mTOR-dependent pathways, such as the AMPK/mTOR and PI3K/Akt/mTOR pathways, and non-mTOR dependent pathways, such as the P53 pathway. Additionally, autophagy plays a dual role in gastric carcinoma (GC), including a tumour-suppressor role and a tumour-promoter role. Long-term Helicobacter pylori infection can impair autophagy, which may eventually promote tumourigenesis of the gastric mucosa. Moreover, Beclin1, LC3 and P62/SQSTM1 are regarded as autophagy-related markers with GC prognostic value. Autophagy inhibitors and autophagy inducers show promise for GC treatment. This review describes research progress regarding autophagy and its significant role in gastric cancer.

BECN1-knockout impairs tumor growth, migration and invasion by suppressing the cell cycle and partially suppressing the epithelial-mesenchymal transition of human triple-negative breast cancer cells

Beclin1 (BECN1), which directly interacts with B‑cell lymphoma 2, serves an important role in autophagy and is involved in the tumorigenesis of various types of cancer. However, the definite role of BECN1 in breast cancer remains controversial. Bi-allelic knockout of Becn1 in a mouse model leads to an embryonic lethal phenotype, which hampers further investigation. To generate cell lines with knockout of BECN1, the CRISPR/Cas9 technique was used to disrupt BECN1 in human triple-negative breast cancer (TNBC) MDA‑MB‑231 cells. To the best of our knowledge, the present study was the first to successfully disrupt BECN1 in MDA‑MB‑231 cells and to screen three stable monoclonal BECN1‑knockout cell lines, suggesting that BECN1‑knockout is not lethal in TNBC cells. Functional analysis revealed that complete loss of BECN1 suppressed MDA‑MB‑231 proliferation and colony formation via inducing G0/G1 cell cycle arrest, not apoptosis, in vitro. On the other hand, BECN1‑knockout inhibited the migratory and invasive ability of MDA‑MB‑231 cells by partially reversing signals of epithelial-mesenchymal transition. Finally, analysis of publicly available gene expression datasets revealed increased expression of BECN1 in TNBC samples. Taken together, the results of the present study identified BECN1 as an oncogene, providing a novel potential target for the treatment of TNBC.

Autophagy Inhibition in Pancreatic Adenocarcinoma

Although some progress has been made in recent years with the development of more effective chemotherapy regimens, new treatment approaches are needed to improve outcomes for patients with pancreatic adenocarcinoma. The cellular process of autophagy, a cell survival mechanism that allows cancer cells to survive the hazardous conditions of the tumor microenvironment and treatment, has emerged as a viable target in pancreatic cancer. We review the mechanism of autophagy, its role in pancreatic carcinogenesis, the preclinical and clinical evidence supporting targeting autophagy in patients with pancreatic adenocarcinoma, and areas of future investigation that hold promise for improving this treatment approach.

Mild hyperthermia enhances sensitivity of gastric cancer cells to chemotherapy through reactive oxygen species-induced autophagic death

Mild hyperthermia enhances anti-cancer effects of chemotherapy, but the precise biochemical mechanisms involved are not clear. This study was carried out to investigate whether mild hyperthermia sensitizes gastric cancer cells to chemotherapy through reactive oxygen species-induced autophagic death. In total, 20 BABL/c mice of MKN-45 human gastric cancer tumor model were divided into hyperthermia + chemotherapy group, hyperthermia group, chemotherapy group, N-acetyl-L-cysteine group, and mock group. Reactive oxygen species production and expression of autophagy-related genes Beclin1, LC3B, and mammalian target of rapamycin were determined. The relationships between tumor growth regression, expression of autophagy-related genes, and reactive oxygen species production were evaluated. Tumor size and wet weight of hyperthermia + chemotherapy group was significantly decreased relative to values from hyperthermia group, chemotherapy group, N-acetyl-L-cysteine group, and mock group ( F = 6.92, p < 0.01 and F = 5.36, p < 0.01, respectively). Reactive oxygen species production was significantly higher in hyperthermia + chemotherapy group than in hyperthermia, chemotherapy, and mock groups. The expression levels of Beclin1 and LC3B were significantly higher, while those of mammalian target of rapamycin were significantly lower in hyperthermia + chemotherapy group than in hyperthermia, chemotherapy, and mock groups. Tumor growth regression was consistent with changes in reactive oxygen species production and expression of autophagy-related genes. N-acetyl-L-cysteine inhibited changes in the expression of the autophagy-related genes and also suppressed reactive oxygen species production and tumor growth. Hyperthermia + chemotherapy increase expression of autophagy-related genes Beclin1 and LC3B, decrease expression of mammalian target of rapamycin, and concomitantly increase reactive oxygen species generation. These results strongly indicate that mild hyperthermia enhances sensitivity of gastric cancer cells to chemotherapy through reactive oxygen species-induced autophagic death.

Prognostic significance of autophagy-related proteins expression in resected human gastric adenocarcinoma

Gastric adenocarcinoma (GC) is one of the most common malignancies in the world and one of the most frequent causes of cancer-related death. Autophagy is a highly regulated catabolic pathway responsible for the degradation of long-lived proteins and damaged intracellular organelles. However, the mechanism and guiding significance of autophagy in the development and progression of GC have remained to be elucidated. This study aimed to explore the clinicopathological significances and prognostic values of autophagy-related proteins AMBRA1 and Beclin-1 in GC. Quantum dots based immunofluorescence histochemistry (QDs-IHC) was performed to observe the expression of AMBRA1 and Beclin-1 proteins in the tissue microarrays including 163 specimens of GC and 20 noncancerous gastric tissues. Simultaneously, AMBRA1 and Beclin-1 proteins were detected by Western blotting in the 10 fresh GC and corresponding normal gastric tissues. The results showed that the expression levels of both AMBRA1 and Beclin-1 proteins were higher in GC tissues than in noncancerous gastric tissues by QDs-IHC and Western blotting (P<0.05). High AMBRA1 expression was detected in 90 of 163 (55.2%) GCs and high Beclin-1 expression was detected in 83 of 163 (50.9%) GCs. High AMBRA1 expression was closely related to depth of invasion, and lymph nodes metastasis (P<0.05). High expression of Beclin-1 protein was correlated with tumor grade (P<0.05). Positive correlation was observed between AMBRA1 and Beclin-1. Survival analysis indicated the high expression of AMBRA1 and Beclin- 1 was an independent factor in predicting poor overall survival (OS) of GC patients. These findings suggest the high expression of AMBRA1 and Beclin-1 proteins is significantly correlated with GC progression. High AMBRA1 and Beclin-1 expression heralds worse outcome of GC patients, suggesting a novel candidate prognostic marker and a therapeutic target for GC.

Functional role of autophagy in gastric cancer

Autophagy is a highly regulated catabolic pathway responsible for the degradation of long-lived proteins and damaged intracellular organelles. Perturbations in autophagy are found in gastric cancer. In host gastric cells, autophagy can be induced by Helicobacter pylori (or H. pylori) infection, which is associated with the oncogenesis of gastric cancer. In gastric cancer cells, autophagy has both pro-survival and pro-death functions in determining cell fate. Besides, autophagy modulates gastric cancer metastasis by affecting a wide range of pathological events, including extracellular matrix (ECM) degradation, epithelial-to-mesenchymal transition (EMT), tumor angiogenesis, and tumor microenvironment. In addition, some of the autophagy-related proteins, such as Beclin 1, microtubule-associated protein 1 light chain 3 (MAP1-LC3), and p62/sequestosome 1 (SQSTM1) have certain prognostic values for gastric cancer. In this article, we review the recent studies regarding the functional role of autophagy in gastric cancer.

MicroRNA-495 Inhibits Gastric Cancer Cell Migration and Invasion Possibly via Targeting High Mobility Group AT-Hook 2 (HMGA2)

Background

Gastric cancer is one of the most common malignancies, and has a high mortality rate. miR-495 acts as a suppressor in some cancers and HMGA2 (high mobility group AT-hook 2) is a facilitator for cell growth and epithelial-mesenchymal transition (EMT), but little is known about their effect in gastric cancer. This study aimed to investigate the role and mechanism of miR-495 in gastric cancer.

Material/Methods

miR-495 levels were quantitatively analyzed in gastric cancer tissue and GES-1, SGC-7901, BGC-823, and HGC-27 cell lines by qRT-PCR. Levels of miR-495 and HMGA2 were altered by cell transfection, after which cell migration and invasion were examined by Transwell and E-cadherin (CDH1); vimentin (VIM), and alpha smooth muscle actin (ACTA2) were detected by qRT-PCR and Western blotting. The interaction between miR-495 and HMGA2 was verified by dual-luciferase reporter assay.

Results

miR-495 was significantly downregulated in cancer tissue and cell lines (p<0.05). Its overexpression inhibited cell migration and invasion, elevated CDH1, and inhibited VIM and ACTA2 levels in BGC-823 and HGC-27 cells. miR-495 directly inhibited HMGA2, which was upregulated in gastric cancer tissue, and promoted cell migration and invasion, inhibited CDH1, and elevated VIM and ACTA2.

Conclusions

miR-495 acts as a tumor suppressor in gastric cancer by inhibiting cell migration and invasion, which may be associated with its direct inhibition on HMGA2. These results suggest a promising therapeutic strategy for gastric cancer treatment.

The Prognostic Role of SIRT1-Autophagy Axis in Gastric Cancer

Aim. Sirtuin 1 (SIRT1) can induce autophagy through deacetylation of Beclin-1 and other autophagy mediators. However, the relationship between SIRT1 and autophagy in GC has not been defined. Therefore, the aim of this study was to confirm the prognostic value of SIRT1 and Beclin-1 and their relationship in GC patients. Methods. Transmission electron microscopy (TEM) was performed to examine the autophagy in GC patients. Immunohistochemistry was used to examine the expression of SIRT1, Beclin-1 in GC, and adjacent nonneoplastic mucosa. Results. In 7 out of 8 GC patients' samples examined by TEM, more autophagic vesicles were observed in GC tissues compared to adjacent nonneoplastic mucosa tissue. A positive correlation between SIRT1 and Beclin-1 expression was observed. Furthermore, Beclin-1 or SIRT1 expression alone or their combined expression were significantly correlated with advanced clinicopathological parameters. High Beclin-1 and SIRT1 expression alone and their combined high expression predicted shorter overall survival and relapse-free survival. Both high Beclin-1 and SIRT1 expressions were independent prognostic factors for poor survival of GC. Conclusions. Based on our results we can conclude that SIRT1 and Beclin-1 expression alone or in combination can be used as prognostic indicator and may represent new therapeutic targets in GC.

Low expression of MAP1LC3B, associated with low Beclin-1, predicts lymph node metastasis and poor prognosis of gastric cancer

Since the roles of autophagy in gastric cancer remain unclear, we aim to investigate the expression of autophagy-related proteins MAP1LC3B and Beclin-1 in human gastric cancer and discuss their clinical significance and correlation with prognosis of patients with gastric cancer. A total of 160 consecutive patients with gastric cancer who had undergone gastrectomy were enrolled in this study. The expressions of MAP1LC3B and Beclin-1 were assessed by immunohistochemistry. The protein expression rates were analyzed with χ ² and Fisher's exact tests. Survival analysis (overall survival (OS) and relapse-free survival (RFS)) was determined using the Kaplan-Meier method and Cox's proportional hazard regression model. Both the expressions of MAP1LC3B and Beclin-1 were lower in gastric cancer tissues than adjacent normal tissues (57 vs. 82 %, p = 0.007; 72 vs. 88 %, p = 0.046, respectively). Relativity analysis indicated MAP1LC3B expression was positively correlated with Beclin-1 expression (r = 0.424, p < 0.001). Both the MAP1LC3B-high-expression patients and Beclin-1-high-expression patients have longer OS time and RFS time than MAP1LC3B-low-expression patients and Beclin-1-low-expression patients (MAP1LC3B: both p < 0.001; Beclin-1: p = 0.014, p = 0.015, respectively). High simultaneous MAP1LC3B and Beclin-1 expressions were associated with longer OS and RFS compared with low simultaneous MAP1LC3B and Beclin-1 expressions (56.77 vs. 24.42 months, p < 0.001; 53.56 vs. 22.33 months, p < 0.001, respectively). Multivariate survival analysis showed both MAP1LC3B and Beclin-1 were independent prognostic factors for OS time (p = 0.016, p = 0.041, respectively). However, MAP1LC3B (p = 0.022) was an independent prognostic factor for RFS. Moreover, low expressions of MAP1LC3B and Beclin-1 were significantly associated with lymph node metastasis (p = 0.007, p = 0.030, respectively). The loss of MAP1LC3B, correlated with loss of Beclin-1, was observed in gastric cancer and correlated with poor prognosis and lymph node metastasis of gastric cancer patients.

The different roles of selective autophagic protein degradation in mammalian cells

Autophagy is an intracellular pathway for bulk protein degradation and the removal of damaged organelles by lysosomes. Autophagy was previously thought to be unselective; however, studies have increasingly confirmed that autophagy-mediated protein degradation is highly regulated. Abnormal autophagic protein degradation has been associated with multiple human diseases such as cancer, neurological disability and cardiovascular disease; therefore, further elucidation of protein degradation by autophagy may be beneficial for protein-based clinical therapies. Macroautophagy and chaperone-mediated autophagy (CMA) can both participate in selective protein degradation in mammalian cells, but the process is quite different in each case. Here, we summarize the various types of macroautophagy and CMA involved in determining protein degradation. For this summary, we divide the autophagic protein degradation pathways into four categories: the post-translational modification dependent and independent CMA pathways and the ubiquitin dependent and independent macroautophagy pathways, and describe how some non-canonical pathways and modifications such as phosphorylation, acetylation and arginylation can influence protein degradation by the autophagy lysosome system (ALS). Finally, we comment on why autophagy can serve as either diagnostics or therapeutic targets in different human diseases.

Decreased expression of Beclin‑1 is significantly associated with a poor prognosis in oral tongue squamous cell carcinoma

The autophagy-related gene Beclin-1 is critical in the regulation of tumourigenesis and progression, but its role in oral tongue squamous cell carcinoma (OTSCC) has not yet been reported. This study aimed to investigate Beclin-1 expression and its significance in OTSCC. Beclin-1 expression was assessed by reverse transcription-quantitative polymerase chain reaction or western blot analysis in 14 OTSCC tissues and matched adjacent noncancerous tissues as well as in 5 OTSCC cell lines and a normal tongue epithelial cell line. Beclin-1 protein expression was examined by immunohistochemistry in 133 OTSCC specimens, and the correlation between Beclin-1 expression and clinicopathological features was investigated. Furthermore, MTT and colony formation assays were performed to investigate the effect of Beclin-1 on the proliferation and clonogenicity of OTSCC cells. It was demonstrated that Beclin-1 expression was significantly decreased in the majority of the 14 OTSCC tissues and the 5 OTSCC cell lines relative to the matched non-cancerous tissues and the normal tongue epithelial cell line, respectively. Immunohistochemistry analysis revealed that decreased Beclin-1 expression was significantly correlated with poor differentiation, lymph node metastasis, advanced clinical tumour-node-metastasis stage, and a poor prognosis in patients with OTSCC. The in vitro assays indicated that the overexpression of Beclin-1 significantly inhibits the proliferation and clonogenicity of OTSCC cells. These results demonstrate that Beclin-1 acts as a tumour suppressor in the development or progression of OTSCC and that Beclin-1 may represent a novel prognostic marker for patients with OTSCC.

The Role of Autophagy in Hepatocellular Carcinoma

Autophagy is a catabolic process involved in cellular homeostasis under basal and stressed conditions. Autophagy is crucial for normal liver physiology and the pathogenesis of liver diseases. During the last decade, the function of autophagy in hepatocellular carcinoma (HCC) has been evaluated extensively. Currently, autophagy is thought to play a dual role in HCC, i.e., autophagy is involved in tumorigenesis and tumor suppression. Recent investigations of autophagy have suggested that autophagy biomarkers can facilitate HCC prognosis and the establishment of therapeutic approaches. In this review, we briefly summarize the current understanding of autophagy and discuss recent evidence for its role in HCC.

Expression of Beclin Family Proteins Is Associated with Tumor Progression in Oral Cancer

Background

Beclin 1 and Beclin 2 are autophagy-related proteins that show similar amino acid sequences and domain structures. Beclin 1 established the first connection between autophagy and cancer. However, the role of Beclin 2 in cancer is unclear. The aims of this study were to analyze Beclin 1 and Beclin 2 expressions in oral cancer tissues and in cell lines, and to evaluate their possible roles in cancer progression.

Methods

We investigated Beclin 1 and Beclin 2 expressions by immunohistochemistry in 195 cases of oral cancer. The prognostic roles of Beclin 1 and Beclin 2 were analyzed statistically. In vitro, overexpression and knockdown of Beclin proteins were performed on an oral cancer cell line, SAS. The immunofluorescence and autophagy flux assays confirmed that Beclin proteins were involved in autophagy. The impacts of Beclin 1 and Beclin 2 on autophagy and tumor growth were evaluated by conversion of LC3-I to LC3-II and by clonogenic assays, respectively.

Results

Oral cancer tissues exhibited aberrant expressions of Beclin 1 and Beclin 2. The cytoplasmic Beclin 1 and Beclin 2 expressions were unrelated in oral cancer tissues. In survival analyses, high cytoplasmic Beclin 1 expression was associated with low disease specific survival, and negative nuclear Beclin 1 expression was associated with high recurrent free survival. Patients with either high or low cytoplasmic Beclin 2 expression had significantly lower overall survival and disease specific survival rates than those with moderate expression. In oral cancer cells, overexpression of either Beclin 1 or Beclin 2 led to autophagy activation and increased clonogenic survival; knockdown of Beclin 2 impaired autophagy and increased clonogenic survival.

Conclusions

Our results indicated that distinct patterns of Beclin 1 and Beclin 2 were associated with aggressive clinical outcomes. Beclin 1 overexpression, as well as Beclin 2 overexpression and depletion, contributed to tumor growth. These findings suggest Beclin proteins are associated with tumorigenesis.

Autophagy in Helicobacter pylori Infection and Related Gastric Cancer

BACKGROUND

Autophagy, a degradation pathway in which cytoplasmic content is engulfed and degraded by lysosomal hydrolases, plays a pivotal role in infection and inflammation. Given that defects in autophagy lead to increased susceptibility to infection, we investigated the role of autophagy in Helicobacter pylori-related gastric cancer (GC).

MATERIALS AND METHODS

Gene expression of 84 molecules was examined through quantitative real-time PCR in gastric epithelial cells (AGS) and macrophages (THP-1) upon exposure to H. pylori GC026 (GC) and 26695 (gastritis). Further, ATG16L1 rs2241880, IRGM rs13361189, and IRGM rs4958847, polymorphisms that have been investigated in relation to H. pylori infection or GC in Caucasians, were detected by MALDI-TOF mass spectrometry in 304 ethnic Chinese (86 noncardia GC cases/218 functional dyspepsia controls).

RESULTS

Gene expression analyses showed twenty-eight molecules involved in vesicle nucleation, elongation, and maturation to be significantly down-regulated in H. pylori GC026-challenged AGS cells. Further, core autophagy proteins and autophagy regulators were differentially expressed in H. pylori-challenged THP-1-derived macrophages. Analyses of the selected polymorphisms showed that ATG16L1 rs2241880 increased the risk of GC (OR: 2.38, 95% CI: 1.34-4.24) and H. pylori infection (OR: 1.49, 95% CI: 1.02-2.16) while IRGM rs4958847 decreased GC risk (OR: 0.26, 95% CI: 0.09-0.74) in ethnic Chinese, these effect sizes being especially strong in H. pylori-infected individuals (ATG16L1 rs2241880 and IRGM rs13361189).

CONCLUSIONS

Our findings indicate that highly virulent H. pylori strains markedly modulate autophagy in the host cell. Further, for the first time, autophagy polymorphisms were associated with GC in Chinese, a high GC-risk population.

MicroRNA-19a mediates gastric carcinoma cell proliferation through the activation of nuclear factor-κB

In gastric carcinoma, the nuclear factor-κB (NF-κB) signaling pathway is highly active, and the constitutive activation of NF-κB prompts malignant cell proliferation. MicroRNAs are considered to be important mediators in the regulation of the NF-κB signaling pathway. The present study predominantly focussed on the effects of microRNA (miR)-19a on NF-κB activation. Reverse transcription-quantitative polymerase chain reaction was used to quantify the relative levels of miR-19a in gastric carcinoma cells. MTT assays were used to determine the effect of miR-19a on cellular proliferation. To detect the activation of NF-κB, western blotting was performed to measure the protein levels of NF-κB and the products of its downstream target genes. To define the target genes, luciferase reporter assays were used. miR-19a was found to be markedly upregulated in gastric carcinoma cells. The overexpression of miR-19a resulted in proliferation and enhanced migratory capabilities of the MGC-803 gastric carcinoma cell line. The results of the western blot analysis demonstrated that the protein levels of p65 increased when the MGC-803 cells were transfected with miR-19a mimics. In addition, the downstream target genes of miR-19a, including intercellular adhesion molecule, vascular cell adhesion molecule and monocyte chemoattractant protein-1, were upregulated. The results of the luciferase assay indicated that IκB-α was the target gene of miR-19a. Therefore, the results of the present study suggested that miR-19a enhances malignant gastric cell proliferation by constitutively activating the NF-κB signaling pathway.

SIRT1 is a regulator of autophagy: Implications in gastric cancer progression and treatment

Silent mating type information regulation 1 (SIRT1) is implicated in tumorigenesis through its effect on autophagy. In gastric cancer (GC), SIRT1 is a marker for prognosis and is involved in cell invasion, proliferation, epithelial-mesenchymal transition (EMT) and drug resistance. Autophagy can function as a cell-survival mechanism or lead to cell death during the genesis and treatment of GC. This functionality is determined by factors including the stage of the tumor, cellular context and stress levels. Interestingly, SIRT1 can regulate autophagy through the deacetylation of autophagy-related genes (ATGs) and mediators of autophagy. Taken together, these findings support the need for continued research efforts to understand the mechanisms mediating the development of gastric cancer and unveil new strategies to eradicate this disease.

Unc-51 like kinase 1 (ULK1) in silico analysis for biomarker identification: a vital component of autophagy

Autophagy is a degradation pathway involving lysosomal machinery for degradation of damaged organelles like the endoplasmic reticulum and mitochondria into their building blocks to maintain homeostasis within the cell. ULK1, a serine/threonine kinase, is conserved across species, from yeasts to mammals, and plays a central role in autophagy pathway. It receives signals from upstream modulators such as TIP60, mTOR and AMPK and relays them to its downstream substrates like Ambra1 and ZIP kinase. The activity of this complex is regulated through protein-protein interactions and post-translational modifications. Applying in silico analysis we identified (i) conserved patterns of ULK1 that showed its evolutionary relationship between the species which were closely related in a family compared to others. (ii) A total of 23 TFBS distributed throughout ULK1 and nuclear factor (erythroid-derived) 2 (NFE2) is of utmost significance because of its high importance rate. NEF2 has already been shown experimentally to play a role in the autophagy pathway. Most of these were of zinc coordinating class and we suggest that this information could be utilized to modulate this pathway by modifying interactions of these TFs with ULK1. (iii) CATTT haplotype was prominently found with frequency 0.774 in the studied population and nsSNPs which could have harmful effect on ULK1 protein and these could further be tested. (iv) A total of 83 phosphorylation sites were identified; 26 are already known and 57 are new that include one at tyrosine residue which could further be studied for its involvement in ULK1 regulation and hence autophagy. Furthermore, 4 palmitoylation sites at positions 426, 927, 1003 and 1049 were also found which could further be studied for protein-protein interactions as well as in trafficking.

Autophagy in thyroid cancer: present knowledge and future perspectives

Thyroid cancer is the most common endocrine malignancy. Despite having a good prognosis in the majority of cases, when the tumor is dedifferentiated it does no longer respond to conventional treatment with radioactive iodine, the prognosis worsens significantly. Treatment options for advanced, dedifferentiated disease are limited and do not cure the disease. Autophagy, a process of self-digestion in which damaged molecules or organelles are degraded and recycled, has emerged as an important player in the pathogenesis of different diseases, including cancer. The role of autophagy in thyroid cancer pathogenesis is not yet elucidated. However, the available data indicate that autophagy is involved in several steps of thyroid tumor initiation and progression as well as in therapy resistance and therefore could be exploited for therapeutic applications. The present review summarizes the most recent data on the role of autophagy in the pathogenesis of thyroid cancer and we will provide a perspective on how this process can be targeted for potential therapeutic approaches and could be further explored in the context of multimodality treatment in cancer and personalized medicine.

Alternative messenger RNA splicing of autophagic gene Beclin 1 in human B-cell acute lymphoblastic leukemia cells

Beclin 1 is a key factor for initiation and regulation of autophagy, which is a cellular catabolic process involved in tumorigenesis. To investigate the role of alternative splicing of Beclin1 in the regulation of autophagy in leukemia cells, Beclin1 mRNA from 6 different types of cell lines and peripheral blood mononuclear cells from 2 healthy volunteers was reversely transcribed, subcloned, and screened for alternative splicing. New transcript variants were analyzed by DNA sequencing. A transcript variant of Beclin 1 gene carrying a deletion of exon 11, which encoded a C-terminal truncation of Beclin 1 isoform, was found. The alternative isoform was assessed by bioinformatics, immunoblotting and subcellular localization. The results showed that this variable transcript is generated by alternative 3' splicing, and its translational product displayed a reduced activity in induction of autophagy by starvation, indicating that the spliced isoform might function as a dominant negative modulator of autophagy. Our findings suggest that the alternative splicing of Beclin 1 might play important roles in leukemogenesis regulated by autophagy.

Noncoding RNA blockade of autophagy is therapeutic in medullary thyroid cancer

Micro-RNAs are dysregulated in medullary thyroid carcinoma (MTC) and preliminary studies have shown that miRNAs may enact a therapeutic effect through changes in autophagic flux. Our aim was to study the in vitro effect of miR-9-3p on MTC cell viability, autophagy and to investigate the mRNA autophagy gene profile of sporadic versus hereditary MTC. The therapeutic role of miR-9-3p was investigated in vitro using human MTC cell lines (TT and MZ-CRC-1 cells), cell viability assays, and functional mechanism studies with a focus on cell cycle, apoptosis, and autophagy. Post-miR-9-3p transfection mRNA profiling of cell lines was performed using a customized, quantitative RT-PCR gene array card. This card was also run on clinical tumor samples (sporadic: n = 6; hereditary: n = 6) and correlated with clinical data. Mir-9-3p transfection resulted in reduced in vitro cell viability; an effect mediated through autophagy inhibition. This was accompanied by evidence of G2 arrest in the TT cell line and increased apoptosis in both cell lines. Atg5 was validated as a predicted miR-9-3p mRNA target in TT cells. Post-miR-9-3p transfection array studies showed a significant global decline in autophagy gene expression (most notably in PIK3C3, mTOR, and LAMP-1). Autophagy gene mRNAs were generally overexpressed in sporadic (vs. hereditary MTC) and Beclin-1 overexpression was shown to correlate with residual disease. Autophagy is a tumor cell survival mechanism in MTC that when disabled, is of therapeutic advantage. Beclin-1 expression may be a useful prognostic biomarker of aggressive disease.

Autophagy is related to the hedgehog signaling pathway in human gastric adenocarcinoma: prognostic significance of Beclin-1 and Gli2 expression in human gastric adenocarcinoma

Beclin-1 induces autophagy, which is known to be involved in many physiopathological processes such as cell development, aging, stress response, immune response and cancer. Several studies showed that Beclin-1 expression is associated with several prognostic factors of gastric carcinomas. Recently, the connection between autophagy and the hedgehog (HH) signaling pathway has been studied. Here, we investigated the relationship between the autophagy and hedgehog (HH) signaling pathways in gastric adenocarcinoma. We evaluated Beclin-1 and Gli2 expression in 108 gastric adenocarcinoma tissues via immunohistochemical analysis, using a tissue microarray, in relation to survival and other prognostic factors. Our results show that increased Beclin-1 expression is correlated with favorable clinicopathological variables including histologic grade, tumor size, primary tumor (T) stage, lymph node metastasis, lymphatic invasion, neural invasion, and tumor recurrence. Furthermore, increased Gli-2 expression was correlated with several favorable clinicopathological variables including primary tumor (T) stage, lymphatic invasion, and tumor recurrence. Increased Beclin-1 expression was significantly correlated with increased Gli2. Univariate analyses for disease-free survival and overall survival revealed that the higher Beclin-1 and Gli2 expression group had a more favorable prognosis compared with the lower Beclin-1 and Gli2 expression group. Our results suggest that progressively increased Beclin-1 and Gli2 expression contributes to the inhibition of tumor growth and metastasis in gastric adenocarcinoma and Beclin-1 acts as a tumor suppressor by regulating the HH signaling pathway through Gli2 expression in gastric adenocarcinoma.

Beclin 1 expression is closely linked to colorectal carcinogenesis and distant metastasis of colorectal carcinoma

Beclin 1 participates in development, autophagy, differentiation, anti- apoptosis, neurodegeneration, tumorigenesis and cancer progression. The roles of Beclin 1 in colorectal carcinogenesis and its subsequent progression are still unclear. Here, the mRNA and protein expression of Beclin 1 were determined in colorectal carcinoma and matched mucosa by Reverse transcriptase-polymerase chain reaction and Western blot. Immunohistochemistry and in situ hybridization (ISH) were performed on tissue microarryer with colorectal carcinoma, adenoma and mucosa. The expression of Beclin 1 mRNA and protein was found to be higher in colorectal carcinoma than matched mucosa by real-time PCR and Western blot (p < 0.05). According to the ISH data, Beclin 1 expression was lower in colorectal non-neoplastic mucosa (NNM) than adenoma and carcinoma (p < 0.05). Immunohistochemically, primary carcinoma showed stronger Beclin 1 expression than NNM and metastatic carcinoma in the liver (p < 0.05). Beclin 1 protein expression was negatively related to liver and distant metastasis (p < 0.05), but not correlated with age, sex, depth of invasion, lymphatic or venous invasion, lymph node metastasis, tumor-node-metastasis (TNM) staging, differentiation or serum carcinoembryonic antigen (CEA) concentration (p > 0.05). Survival analysis indicated that Beclin 1 expression was not linked to favorable prognosis of the patients with colorectal carcinoma (p > 0.05). Cox's model indicated that depth of invasion and distant metastasis were independent prognostic factors for colorectal carcinomas (p < 0.05). It was suggested that Beclin 1 expression is closely linked to colorectal carcinogenesis and distant metastasis of colorectal carcinoma.

Xenophagy in Helicobacter pylori- and Epstein-Barr virus-induced gastric cancer

Helicobacter pylori and Epstein-Barr virus (EBV) account for roughly 80% and 10%, respectively, of gastric carcinomas worldwide. Autophagy is an evolutionarily conserved and intricately regulated cellular process that involves the sequestration of cytoplasmic proteins and organelles into double-membrane autophagosomes that eventually fuse with lysosomes for degradation of the engulfed content. Emerging evidence indicates that xenophagy, a form of selective autophagy, plays a crucial role in the pathogenesis of H. pylori- and EBV-induced gastric cancer. Xenophagy specifically recognizes intracellular H. pylori and EBV and physically targets these pathogens to the autophagosomal-lysosomal pathway for degradation. In this connection, H. pylori or EBV-induced dysregulation of autophagy may be causally linked to gastric tumourigenesis and therefore can be exploited as therapeutic targets. This review will discuss how H. pylori and EBV infection activate autophagy and how these pathogens evade recognition and degradation by the autophagic pathway. Elucidating the molecular aspects of H. pylori- and EBV-induced autophagy will help us better understand the pathogenesis of gastric cancer and promote the development of autophagy modulators as antimicrobial agents.

The prognostic value of autophagy-related markers beclin-1 and microtubule-associated protein light chain 3B in cancers: a systematic review and meta-analysis

Use of the autophagy-related markers beclin-1 (BECN1) and microtubule-associated protein light chain 3B (LC3B) as prognostic markers has been extensively investigated in various kinds of cancers. However, their prognostic roles are still controversial and not firmly validated. We systematically reviewed the evidence from various studies concerning the relationship between BECN1 and LC3B expression in cancers and overall survival (OS)/disease-free survival (DFS) to elucidate this issue. PubMed, Embase, Cochrane Library, and China National Knowledge Infrastructure (CNKI) were searched in July 2013 (then updated in April 2014) to identify eligible cohort studies that reported associations between BECN1 or LC3B expression and OS/DFS in cancer patients. Combined hazard ratios (HRs) with 95 % confidence intervals (95 % CIs) were pooled using fixed-effects or random-effects models according to heterogeneity in different groups. A total of 23 studies in distinct cancers were eligible for systematic review and meta-analysis. Our pooled results identified that a high expression of BECN1 is associated with favorable OS in gastric cancer (HR = 0.49, 95 % CI = 0.34-0.72) and lymphoma (HR = 0.25, 95 % CI = 0.11-0.57), whereas a high expression of LC3B predicts adverse OS in breast cancer (HR = 1.98, 95 % CI = 1.25-3.13). This systematic review and meta-analysis indicated that the autophagy-related marker BECN1 might be a predictive factor of favorable prognosis in gastric cancer, breast cancer, and lymphoma and LC3B might predict unfavorable prognosis of breast cancer. Nevertheless, due to the limited number and retrospective design of the original studies, more powerful prospective cohorts are required to verify these conclusions.

The autophagy-related marker LC3 can predict prognosis in human hepatocellular carcinoma

Background

Defects of autophagy and endoplasmic reticulum (ER) stress are related to many diseases and tumors. However, only a few studies have examined hepatocellular carcinoma (HCC) as related to these processes. Therefore, in this study, we investigated the expression and extent of autophagy and ER stress-related markers in HCC and their influence on clinical characteristics and prognosis for each protein.

Methodology

The expression of autophagy-related markers (LC3 and Beclin-1) and ER stress-related markers (GRP78 and CHOP) was analyzed by immunohistochemistry on tissues from completely resected specimens of 190 HCC patients. Their influence on clinicopathologic features and prognosis were evaluated using the chi-square test and Kaplan-Meier analysis. Correlations of each protein were determined by Spearman's correlation analysis.

Principal Findings

LC3 expression was not correlated with TNM, BCLC stage, or Edmonson-Steiner grading, whereas it was correlated with longer overall survival (OS) (p = 0.039) and tended to be related with longer time to recurrence (TTR) (p=0.068) although it did not show statistical significance. Multivariate analysis indicated that LC3 expression was a significantly independent prognostic factor of OS (HR, 0.42; 95% CI, 0.22-0.80; p-value=0.009) and TTR (HR, 0.54; 95% CI, 0.33–0.90; p=0.017). Expression of LC3 in advanced stages of TNM (III) (p=0.045) and Edmonson-Steiner Grades (III and IV) (p=0.043) was correlated with longer survival, but not in the early stages. A positive correlation was not observed between the expression of autophagy-related markers and ER stress-related markers.

Conclusion

Our results suggest that the expression and extent of LC3 might be a strong prognostic factor of HCC, especially in patients with surgical resection.

The role of beclin-1 expression in patients with gastric cancer: a meta-analysis

Beclin-1 has been identified as a reliable biomarker in monitoring the prognosis for tumors. We carried out a meta-analysis focusing on the relationship between beclin-1 and the clinical characteristics of patients with gastric cancer. We identified articles in MEDLINE, PubMed, Embase, ISI Web of Science, and Chinese National Knowledge Infrastructure databases by using the following strategy: ("beclin 1" or "beclin-1" or "ATG6") and ("gastric cancer" or "stomach cancer"). We conducted a final analysis of 1,254 patients from seven studies. The pooled odds ratio (OR) indicated a significant association between beclin-1 expression and the differentiation of gastric cancer (pooled OR = 0.23; 95 % confidence interval (CI) = 0.07-0.73) or tumor-node-metastasis staging of gastric cancer (pooled OR = 0.62; 95 % CI = 0.48-0.79). Beclin-1 expression was different in intestinal- and diffuse-type gastric cancer (pooled OR = 0.55; 95 % CI = 0.39-0.77). No association between beclin-1 and tumor size (pooled OR = 0.73; 95 % CI = 0.45-1.17) or lymph node metastasis (pooled OR = 0.59; 95 % CI = 0.17-1.99) was observed.