The significance of autophagy in colorectal cancer pathogenesis and implications for therapy

p21 as a Predictor and Prognostic Indicator of Clinical Outcome in Rectal Cancer Patients

The cell cycle plays a key and complex role in the development of human cancers. p21 is a potent cyclin-dependent kinase inhibitor (CDKI) involved in the promotion of cell cycle arrest and the regulation of cellular senescence. Altered p21 expression in rectal cancer cells may affect tumor cells' behavior and resistance to neoadjuvant and adjuvant therapy. Our study aimed to ascertain the relationship between the differential expression of p21 in rectal cancer and patient survival outcomes. Using tissue microarrays, 266 rectal cancer specimens were immunohistochemically stained for p21. The expression patterns were scored separately in cancer cells retrieved from the center and the periphery of the tumor; compared with clinicopathological data, tumor regression grade (TRG), disease-free, and overall survival. Negative p21 expression in tumor periphery cells was significantly associated with longer overall survival upon the univariate (p = 0.001) and multivariable analysis (p = 0.003, HR = 2.068). Negative p21 expression in tumor periphery cells was also associated with longer disease-free survival in the multivariable analysis (p = 0.040, HR = 1.769). Longer overall survival times also correlated with lower tumor grades (p= 0.011), the absence of vascular and perineural invasion (p = 0.001; p < 0.005), the absence of metastases (p < 0.005), and adjuvant treatment (p = 0.009). p21 expression is a potential predictive and prognostic biomarker for clinical outcomes in rectal cancer patients. Negative p21 expression in tumor periphery cells demonstrated significant association with longer overall survival and disease-free survival. Larger prospective studies are warranted to investigate the ability of p21 to identify rectal cancer patients who will benefit from neoadjuvant and adjuvant therapy.

Natural Compounds Targeting the Autophagy Pathway in the Treatment of Colorectal Cancer

Autophagy is a highly conserved intracellular degradation pathway by which misfolded proteins or damaged organelles are delivered in a double-membrane vacuolar vesicle and finally degraded by lysosomes. The risk of colorectal cancer (CRC) is high, and there is growing evidence that autophagy plays a critical role in regulating the initiation and metastasis of CRC; however, whether autophagy promotes or suppresses tumor progression is still controversial. Many natural compounds have been reported to exert anticancer effects or enhance current clinical therapies by modulating autophagy. Here, we discuss recent advancements in the molecular mechanisms of autophagy in regulating CRC. We also highlight the research on natural compounds that are particularly promising autophagy modulators for CRC treatment with clinical evidence. Overall, this review illustrates the importance of autophagy in CRC and provides perspectives for these natural autophagy regulators as new therapeutic candidates for CRC drug development.

Moxidectin induces autophagy arrest in colorectal cancer

Colorectal cancer (CRC) is a cancer with a high morbidity and mortality worldwide. Hence, developing new therapeutic drugs for CRC is very important. Moxidectin (MOX) has shown good anti-glioblastoma effect both in vitro and in vivo. This study aimed to elucidate the anti-CRC effect of MOX and its potential mechanism by investigating the influence of MOX on the viability, apoptosis, necrosis and autophagy of colorectal cancer cells (HCT15 and SW620) and its underlying mechanisms. It was found that MOX can induce autophagy arrest, promote autophagy initiation, inhibit autophagic flux and cell proliferation, simultaneously PI3K-Akt-mTOR signaling pathway and microtubule acetylation. Furthermore, MOX suppressed the growth of xenograft tumors, which was consistent with the in vitro results.

Nuclear Beclin 1 Destabilizes Retinoblastoma Protein to Promote Cell Cycle Progression and Colorectal Cancer Growth

Simple Summary

The role of autophagy core-protein Beclin 1 in colorectal cancer (CRC) development remains controversial. Here, we show that nuclear Beclin 1 is up-regulated in CRC with a negative correlation to RB protein expression. Silencing of BECN1 up-regulates RB expression resulting in cell cycle G1 arrest and inhibition of xenograft tumor growth independent of p53. Ablation of BECN1 facilitates MDM2–MDMX complex formation to promote MDMX polyubiquitination and degradation, consequently leading to RB protein stabilization. These results reveal that nuclear Beclin 1 can promote CRC growth through modulation of RB protein stability and imply that nuclear Beclin 1 may be a prognostic indicator in human colorectal cancer.

Abstract

Autophagy is elevated in colorectal cancer (CRC) and is generally associated with poor prognosis. However, the role of autophagy core-protein Beclin 1 remains controversial in CRC development. Here, we show that the expression of nuclear Beclin 1 protein is upregulated in CRC with a negative correlation to retinoblastoma (RB) protein expression. Silencing of BECN1 upregulates RB resulting in cell cycle G1 arrest and growth inhibition of CRC cells independent of p53. Furthermore, ablation of BECN1 inhibits xenograft tumor growth through elevated RB expression and reduced autophagy, while simultaneous silencing of RB1 restores tumor growth but has little effect on autophagy. Mechanistically, knockdown of BECN1 promotes the complex formation of MDM2 and MDMX, resulting in MDM2-dependent MDMX instability and RB stabilization. Our results demonstrate that nuclear Beclin 1 can promote cell cycle progression through modulation of the MDM2/X-RB pathway and suggest that Beclin 1 promotes CRC development by facilitating both cell cycle progression and autophagy.

AGXT2L1 is downregulated in carcinomas of the digestive system

Alanine-glyoxylate aminotransferase 2-like 1 (AGXT2L1) is a modulator of phospholipid metabolism, and its role in tumor biology is obscure. Previously, significant downregulation of AGXT2L1 has been observed in hepatocellular carcinoma. The aim of the present study was to investigate AGXT2L1 expression and its association with the clinical characteristics of common carcinomas of the digestive system. In the present study, the expression levels of AGXT2L1 were detected by immunohistochemical staining in colorectal cancer (CRC), gastric cancer and pancreatic cancer tissues. The associations between AGXT2L1 expression and clinicopathological features were analyzed using public gene expression datasets. Small interfering RNA was transfected into SW480 and HCT116 cells to explore the role of AGXT2L1 in CRC cells. AGXT2L1 expression was significantly decreased in cancerous tissues compared with in normal tissues, and low AGXT2L1 expression was associated with an unfavorable prognosis in patients. Furthermore, it was revealed that AGXT2L1 may regulate phosphatidylinositol and phosphatidylserine metabolism in cancerous tissues, and that decreased AGXT2L1 expression could induce autophagy in CRC cells. Overall, the present study provides a basis for further understanding of the role of AGXT2L1 and its association with autophagy in cancer.

Prognostic and predictive value of an autophagy-related signature for early relapse in stages I-III colon cancer

We postulated that expression differences of autophagy-related genes are instrumental in stratifying the risk of early relapse after surgery and evaluating the prognosis of patients with stages I-III colon cancer. Therefore, propensity score matching analysis was performed between patients in early relapse group and long-term survival group from GSE39582 test series and internal validation series. Using Cox regression model, a nine-autophagy-related signature (CAPN2, ATG16L2, TP63, SIRT1, RPS6KB1, PEX3, ATG5, UVRAG, NAF1) was established to classify patients into those at high risk of early relapse (high-risk group), and those at low risk of early relapse (low-risk group). Relapse-free survival (RFS) was significantly different between the two groups in test [hazard ratio (HR): 2.019, 95% confidence interval (CI): 1.362-2.992, P < 0.001], internal validation (HR: 2.464, 95% CI: 1.196-5.079, P < 0.001) and another two external validation series (GSE14333-HR: 2.250, 95% CI: 1.227-4.126, P = 0.007; GSE33113-HR: 5.552, 95% CI: 2.098-14.693, P < 0.001). Then, based on RFS, we developed a nomogram, integrating the nine-autophagy-related classifier and four clinicopathological risk factors to evaluate prognosis of stages I-III colon cancer patients. Time-dependent receiver operating curve at 2 years showed that the integrated signature (area under curve = 0.758) had better prognostic accuracy than American Joint Committee on Cancer TNM stage (area under curve = 0.620). In conclusion, we identified and built a nine-autophagy-related signature, a credible approach to early relapse prediction in stages I-III colon cancer patients, which can assist physicians in devising more efficient therapeutic strategies.

MiR-153-5p promotes sensibility of colorectal cancer cells to oxaliplatin via targeting Bcl-2-mediated autophagy pathway

Oxaliplatin (L-OHP) is one of the effective chemotherapeutic drugs for colorectal cancer (CRC). Further investigation into the molecular mechanism of chemoresistance could improve outcomes for patients with colorectal cancer. Recently, microRNAs have been reported as a key in drug resistance of tumors. In this study, we aimed to investigate the effects of miR-153-5p in L-OHP-resistant CRC cells, and its underlying mechanism. Downregulation of miR-153-5p was observed in CRC cells, while upregulation of miR-153-5p enhances the chemosensitivity of CRC/L-OHP cells. The autophagy of CRC/L-OHP cells was markedly increased after exposure to L-OHP but abolished by the upregulation of miR-153-5p. Dual-luciferase reporter assays validated that Bcl-2 was a direct target of miR-153-5p. In conclusion, our data suggested that miR-153-5p was a mediator of cisplatin resistance in colorectal cancer by affecting Bcl-2-mediated autophagy, indicating a new therapeutic target for CRC treatment.

An Integrated Nomogram Combining Clinical Factors and Microtubule-Associated Protein 1 Light Chain 3B Expression to Predict Postoperative Prognosis in Patients with Intrahepatic Cholangiocarcinoma

Purpose

Microtubule-associated protein 1 light chain 3B (LC3B) serves as a key component of autophagy, which is associated with the progression of carcinoma. Yet, it is still unclear whether LC3B is also an independent risk factor for intrahepatic cholangiocarcinoma (ICC). We aim to explore the predictive value of LC3B on prognosis of ICC, and to establish a novel and available nomogram to predict relapse-free survival (RFS) and overall survival (OS) for these patients after curative-intent hepatectomy.

Materials and Methods

From August 2004 to March 2017, 105 ICC patients were eligibly enrolled in the Third Affiliated Hospital of Sun Yat-sen University. Preoperative clinical information of enrolled patients was collected. Expression LC3B in the ICC specimen was detected by immunohistochemistry.

Results

The 5-year RFS and OS in this cohort were 15.7% and 29.6%, respectively. On multivariate Cox regression analysis, independent risk factors for 5-year OS were cancer antigen 125, microvascular invasion, LC3B expression and lymph node metastasis. Except for the above 4 factors, neutrophil/lymphocyte ratio and tumor differentiation were independent factors for 5-year RFS. The area under the curve of nomograms for OS and RFS were 0.820 and 0.747, respectively.

Conclusion

The nomograms based on LC3B can be considered as effective models to predict postoperative survival for ICC patients.

Photodynamic Therapy Activity of New Porphyrin-Xylan-Coated Silica Nanoparticles in Human Colorectal Cancer

Photodynamic therapy (PDT) using porphyrins has been approved for treatment of several solid tumors due to the generation of cytotoxic reactive oxygen species (ROS). However, low physiological solubility and lack of selectivity towards tumor sites are the main limitations of their clinical use. Nanoparticles are able to spontaneously accumulate in solid tumors through an enhanced permeability and retention (EPR) effect due to leaky vasculature, poor lymphatic drainage, and increased vessel permeability. Herein, we proved the added value of nanoparticle vectorization on anticancer efficacy and tumor-targeting by 5-(4-hydroxyphenyl)-10,15,20-triphenylporphyrin (TPPOH). Using 80 nm silica nanoparticles (SNPs) coated with xylan-TPPOH conjugate (TPPOH-X), we first showed very significant phototoxic effects of TPPOH-X SNPs mediated by post-PDT ROS generation and stronger cell uptake in human colorectal cancer cell lines compared to free TPPOH. Additionally, we demonstrated apoptotic cell death induced by TPPOH-X SNPs-PDT and the interest of autophagy inhibition to increase anticancer efficacy. Finally, we highlighted in vivo, without toxicity, elevated anticancer efficacy of TPPOH-X SNPs through improvement of tumor-targeting compared to a free TPPOH protocol. Our work demonstrated for the first time the strong anticancer efficacy of TPPOH in vitro and in vivo and the merit of SNPs vectorization.

Adenine Inhibits the Growth of Colon Cancer Cells via AMP-Activated Protein Kinase Mediated Autophagy

Background

Adenine is involved in a variety of cell biological processes and has been explored for pharmacological uses. Its therapeutic use for managing cancer is of great interest. In the present study, we investigated the anticancer effects of adenine and the underlying mechanism in colon cancer cells.

Methods

Cell viability was measured using the MTT assay. Levels of phosphorylation and protein expression were determined using western blotting. qPCR was carried out to determine the changes in mRNA expression of genes of interest.

Results

Adenine significantly inhibited the viability of colon cancer cells, HT29 and Caco-2 cells, in a dose-dependent manner. Adenine induced significant apoptosis in HT29 cells, whereas Caco-2 cells exhibited less apoptotic responses. The data showed that adenine activated AMP-activated protein kinase (AMPK) signaling contributing to autophagic cell death through mTOR in both colon cancer cell lines.

Conclusions

Our findings suggest that adenine inhibits the growth of colon cancer cells. Anticancer activity of adenine in colon cancer cells is attributable to the activation of apoptotic signaling and in turn the AMPK/mTOR pathway. Adenine represents a natural compound with anticancer potency.

Long non coding RNA UCA1 contributes to the autophagy and survival of colorectal cancer cells via sponging miR-185-5p to up-regulate the WISP2/β-catenin pathway

The estimated number of new cases of colorectal cancer (CRC) will increase to 140 250 in 2018 worldwide. The long non-coding RNA (lncRNA) urothelial carcinoma-associated 1 (UCA1) has recently been shown to be dysregulated in CRC, which plays an important role in the progression of CRC. However, the biological role and the underling mechanism of UCA1 in the carcinogenesis of CRC remain unclear. Herein, we found that UCA1 was aberrantly upregulated in two CRC cell lines (SW620 and HT29) compared to colorectal cell CCD-18Co. UCA1 knockdown inhibited the apoptosis, growth and autophagy of CRC cell lines in vitro. Furthermore, UCA1 could act as an endogenous sponge by directly interacting with miR-185-5p and downregulation miR-185-5p expression. In addition, UCA1 could reverse the inhibitory effect of miR-185-5p on the growth and autophagy of CRC cells, which might be involved in the derepression of member 1 (WNT1)-inducible signaling pathway protein 2 (WISP2, a target gene of miR-185-5p) expression and the activation of the WISP2/β-catenin signaling pathway. In vivo, the present study elucidates a novel UCA1-miR-185-5p-WISP2-Wnt/β-catenin axis in CRC, which may help us to understand the pathogenesis and the feasibility of lncRNA-directed diagnosis and therapy of CRC.

The estimated number of new cases of colorectal cancer (CRC) will increase to 140 250 in 2018 worldwide.

Selected Aspects of Chemoresistance Mechanisms in Colorectal Carcinoma-A Focus on Epithelial-to-Mesenchymal Transition, Autophagy, and Apoptosis

Chemoresistance has been found in all malignant tumors including colorectal carcinoma (CRC). Nowadays chemoresistance is understood as a major reason for therapy failure, with consequent tumor growth and spreading leading ultimately to the patient's premature death. The chemotherapy-related resistance of malignant colonocytes may be manifested in diverse mechanisms that may exist both prior to the onset of the therapy or after it. The ultimate function of this chemoresistance is to ensure the survival of malignant cells through continuing adaptation within an organism, therefore, the nature and spectrum of cell-survival strategies in CRC represent a highly significant target of scientific inquiry. Among these survival strategies employed by CRC cells, three unique but significantly linked phenomena stand out-epithelial-to-mesenchymal transition (EMT), autophagy, and cell death. In this mini-review, current knowledge concerning all three mechanisms including their emergence, timeline, regulation, and mutual relationships will be presented and discussed.

CD44v6 engages in colorectal cancer progression

CD44 is a transmembrane glycoprotein. When the CD44 gene is expressed, its pre-messenger RNA (mRNA) can be alternatively spliced into mature mRNAs that encode several CD44 isoforms. The mRNA assembles with ten standard exons, and the sixth variant exon encodes CD44v6, which engages in a variety of biological processes, including cell growth, apoptosis, migration, and angiogenesis. Mechanistically, CD44v6 interacts with hyaluronic acid (HA) or osteopontin, or it acts as a coreceptor for various cytokines, such as epidermal growth factor, vascular endothelial growth factor, hepatocyte growth factor, and C-X-C motif chemokine 12. In this context, the receptor tyrosine kinase or G protein-coupled receptor-associated signaling pathways, including mitogen-activated protein kinase/extracellular-signal-regulated kinase and phosphoinositide-3-kinase/Akt, are activated. Using these actions, homeostasis or regeneration can be facilitated among normal tissues. However, overexpression of the mature mRNA encoding CD44v6 can induce cancer progression. For example, CD44v6 assists colorectal cancer stem cells in colonization, invasion, and metastasis. Overexpression of CD44v6 predicts poor prognosis in patients with colorectal cancer, as patients with a large number of CD44v6-positive cells in their tumors are generally diagnosed at late stages. Thus, the clinical significance of CD44v6 in colorectal cancer deserves consideration. Preclinical results have indicated satisfactory efficacies of anti-CD44 therapy among several cancers, including prostate cancer, pancreatic cancer, and gastric cancer. Moreover, clinical trials aiming to evaluate the pharmacokinetics, pharmacodynamics, efficacy, and toxicity of a commercialized anti-CD44 monoclonal antibody developed by Roche (RO5429083) have been conducted among patients with CD44-expressing malignant tumors, and a clinical trial focusing on the dose escalation of this antibody is ongoing. Thus, we are hopeful that anti-CD44 therapy will be applied in the treatment of colorectal cancer in the future.

Long noncoding RNA UCA1 targets miR-582-5p and contributes to the progression and drug resistance of bladder cancer cells through ATG7-mediated autophagy inhibition

BACKGROUND

Rently, the incidence of bladder cancer has been on the rise. Accumulating researches have been conducted to clarify the molecular mechanisms and potential therapeutic targets of bladder cancer. The present study aims to explore the regulatory mechanism of the urothelial carcinoma-associated 1 (UCA1)-miR-582-5p-ATG7 axis in bladder cancer.

METHODS

Quantitative real-time polymerase chain reaction was used to detect mRNA level. Relative protein expression was detected by western blot. wound healing assay and transwell were used to determine migration and invasion of cells. in addtion, luciferase reporter assay and immunohistochemistry were performed.

RESULTS

UCA1 expression was upregulated in bladder cancer tissues and cells, while the depletion of UCA1 by shRNA resulted in the suppression of cell proliferation, invasion, migration, and drug resistance. Further studies demonstrated that UCA1 could directly interact with miR-582-5p, and that there was an inverse correlation between miR-582-5p and UCA1. In addition, we found that ATG7 is a target of miR-582-5p and can be downregulated by either miR-582-5p overexpression or UCA1 knockdown. In particular, the autophagy is reduced when UCA1 shRNA is introduced. Moreover, the in vivo experiment further demonstrated the contribution of UCA1 in bladder cancer including tumor growth, invasion, and migration, and UCA1 knockdown can inhibit the aforementioned activities.

CONCLUSION

These results provided evidence for a novel UCA1 interaction regulatory network in bladder cancer, that is, UCA1-miR-582-5p-ATG7-autophagy axis. Our study provides a new insight into the treatment of bladder cancer.

Differences in LC3B expression and prognostic implications in oropharyngeal and oral cavity squamous cell carcinoma patients

Background

This study examined the prognostic significance of microtubule-associated protein light chain 3B (LC3B) expression in oropharyngeal and oral cavity squamous cell carcinoma (SCC). The prognostic significance of LC3B expression in relation to human papillomavirus (HPV) status in oropharyngeal SCC was also examined.

Methods

Tissue microarrays (TMAs) were constructed from formalin-fixed, paraffin-embedded oropharyngeal (n = 47) and oral cavity (n = 95) SCC tissue blocks from patients with long-term recurrence and overall survival data (median = 47 months). LC3B expression on tumour was assessed by immunohistochemistry and evaluated for associations with clinicopathological variables. LC3B expression was stratified into high and low expression cohorts using ROC curves with Manhattan distance minimisation, followed by Kaplan–Meier and multivariable survival analyses. Interaction terms between HPV status and LC3B expression in oropharyngeal SCC patients were also examined by joint-effects and stratified analyses.

Results

Kaplan–Meier survival and univariate analyses revealed that high LC3B expression was correlated with poor overall survival in oropharyngeal SCC patients (p = 0.007 and HR = 3.18, 95% CI 1.31–7.71, p = 0.01 respectively). High LC3B expression was also an independent prognostic factor for poor overall survival in oropharyngeal SCC patients (HR = 4.02, 95% CI 1.38–11.47, p = 0.011). In contrast, in oral cavity SCC, only disease-free survival remained statistically significant after univariate analysis (HR = 2.36, 95% CI 1.19–4.67, p = 0.014), although Kaplan-Meier survival analysis showed that high LC3B expression correlated with poor overall and disease-free survival (p = 0.046 and 0.011 respectively). Furthermore, oropharyngeal SCC patients with HPV-negative/high LC3B expression were correlated with poor overall survival in both joint-effects and stratified presentations (p = 0.024 and 0.032 respectively).

Conclusions

High LC3B expression correlates with poor prognosis in oropharyngeal and oral cavity SCC, which highlights the importance of autophagy in these malignancies. High LC3B expression appears to be an independent prognostic marker for oropharyngeal SCC but not for oral cavity SCC patients. The difference in the prognostic significance of LC3B between oropharyngeal and oral cavity SCCs further supports the biological differences between these malignancies. The possibility that oropharyngeal SCC patients with negative HPV status and high LC3B expression were at particular risk of a poor outcome warrants further investigation in prospective studies with larger numbers.

RNF216 contributes to proliferation and migration of colorectal cancer via suppressing BECN1-dependent autophagy

Originally identified as an E3 ligase regulating toll-like receptor (TLR) signaling, ring finger protein 216 (RNF216) also plays an essential role in autophagy, which is fundamental to cellular homeostasis. Autophagy dysfunction leads to an array of pathological events, including tumor formation. In this study, we found that RNF216 was upregulated in human colorectal cancer (CRC) tissues and cell lines, and was associated with progression of CRC. RNF216 promoted CRC cell proliferation and migration in vitro and in vivo, largely by enhancing proteasomal degradation of BECN1, a key autophagy regulator and tumor suppressor. RNF216 restricted CRC cell autophagy through BECN1 inhibition under nutritional starvation conditions. RNF216 knockdown increased the autophagy, limiting CRC cell proliferation and migration. Moreover, BECN1 knockdown or autophagy inhibition restored proliferation and migration of RNF216-knockdown CRC cells. Collectively, our results suggested that RNF216 promoted CRC cell proliferation and migration by negatively regulating BECN1-dependent autophagy. This makes RNF216 as a potential biomarker and novel therapeutic target for inhibiting CRC development and progression.

Gypenoside L inhibits autophagic flux and induces cell death in human esophageal cancer cells through endoplasm reticulum stress-mediated Ca2+ release

Esophageal cancer is one of the leading cause of cancer mortality in the world. Due to the increased drug and radiation tolerance, it is urgent to develop novel anticancer agent that triggers nonapoptotic cell death to compensate for apoptosis resistance. In this study, we show that treatment with gypenoside L (Gyp-L), a saponin isolated from Gynostemma pentaphyllum, induced nonapoptotic, lysosome-associated cell death in human esophageal cancer cells. Gyp-L-induced cell death was associated with lysosomal swelling and autophagic flux inhibition. Mechanistic investigations revealed that through increasing the levels of intracellular reactive oxygen species (ROS), Gyp-L triggered protein ubiquitination and endoplasm reticulum (ER) stress response, leading to Ca2+ release from ER inositol trisphosphate receptor (IP3R)-operated stores and finally cell death. Interestingly, there existed a reciprocal positive-regulatory loop between Ca2+ release and ER stress in response to Gyp-L. In addition, protein synthesis was critical for Gyp-L-mediated ER stress and cell death. Taken together, this work suggested a novel therapeutic option by Gyp-L through the induction of an unconventional ROS-ER-Ca2+-mediated cell death in human esophageal cancer.

Phospholipid scramblase 1 as a critical node at the crossroad between autophagy and apoptosis in mantle cell lymphoma

Mantle cell lymphoma (MCL) is an aggressive haematological malignancy in which the response to therapy can be limited by aberrantly activated molecular and cellular pathways, among which autophagy was recently listed. Our study shows that the 9-cis-retinoic acid (RA)/Interferon(IFN)-α combination induces protective autophagy in MCL cell lines and primary cultures reducing the extent of drug-induced apoptosis. The treatment significantly up-regulates phospholipid scramblase 1 (PLSCR1), a protein which bi-directionally flips lipids across membranes. In particular, RA/IFN-α combination concomitantly increases PLSCR1 transcription and controls PLSCR1 protein levels via lysosomal degradation. Herein we describe a new function for PLSCR1 as negative regulator of autophagy. Indeed, PLSCR1 overexpression reduced MCL cell susceptibility to autophagy induced by RA/IFN-α, serum deprivation or mTOR pharmacological inhibition. Moreover, PLSCR1 can bind the ATG12/ATG5 complex preventing ATG16L1 recruitment and its full activation, as indicated by co-immunoprecipitation experiments. The combination of doxorubicin or bortezomib with RA/IFN-α strengthened PLSCR1 up-regulation and enhanced apoptosis, as a likely consequence of the blockade of RA/IFN-α-induced autophagy. Immunohistochemical analysis of 32 MCL biopsies revealed heterogeneous expression of PLSCR1 and suggests its possible implication in the response to anticancer therapies, especially to drugs promoting protective autophagy.

Beclin 1 and LC3 as predictive biomarkers for metastatic colorectal carcinoma

Autophagy is a highly conserved self-destructive process that disassembles dysfunctional or unnecessary cellular components. It plays an important role in cancer metastasis, which is of particular interest considering metastatic disease is the major cause of colorectal carcinoma (CRC) related mortality. Here, we investigated the immunohistochemical expression of autophagy-related protein Beclin 1 and Microtubule-associated protein 1A/1B-light chain 3 (LC3) within surgical CRC specimens, first in a training cohort (205 patients), then in an inner validation cohort (160 patients) and an independent cohort (161 patients). The expressions of Beclin 1 and LC3 were lower in metastatic CRC compared with non-metastatic CRC. Furthermore, we developed an autophagy-based classifier for metastatic prediction. This classifier, including Beclin 1, LC3 and carcinoembryonic antigen (CEA) level, resulted in 82.9% sensitivity and 89.8% specificity for metastatic detection in the training cohort. In the independent cohort, it achieved 77.9% sensitivity and 90.3% specificity in predicting the metastasis of CRC. These results suggested that low expression of Beclin 1 and LC3 contributed to a more aggressive cancer cell phenotype, and our autophagy-based classifier was a reliable tool for metastatic prediction in CRC.

RANK Ligand Modulation of Autophagy in Oral Squamous Cell Carcinoma Tumor Cells

Autophagy is a cellular process to recycle nutrients and has been implicated in cancer treatment. Oral squamous cell carcinoma (OSCC) is the most common oral cancer which ranks 3% of cancers in men and 2% in women. In this study, immunohistochemical staining of OSCC tumor specimens from human subjects and an athymic mouse model demonstrated high levels of autophagy markers LC3-II and ATG5 expression. Further, we identified high levels LC3-II expression in OSCC tumor cell lines (SCC-1, SCC-12, and SCC-14a) compared to normal human epithelial (RWPE-1) cells. OSCC cells express high levels of RANK ligand (RANKL); however, a functional role in autophagy is unknown. Interestingly, RANKL stimulation significantly increased autophagosome-related gene expressions such as LC3, ATG5, BECN1, and PI3KC3 mRNA expression in OSCC cells. Further, Western blot analysis of total cell lysates demonstrated a dose-dependent increase in LC3-II and ATG5 expression in RANKL-stimulated cells. In addition, RANKL increased expression of LC3-I and LC3-II, essential for autophagosome formation. Confocal microscopy analysis of LC3-II and localization with lysosome further confirms autophagosome formation in response to RANKL treatment in OSCC cells. Collectively, our results indicate a novel function of RANKL to induce autophagosome formation, and could be a potential therapeutic target to control OSCC tumor progression.

Social isolation induces autophagy in the mouse mammary gland: link to increased mammary cancer risk

Social isolation is a strong predictor of early all-cause mortality and consistently increases breast cancer risk in both women and animal models. Because social isolation increases body weight, we compared its effects to those caused by a consumption of obesity-inducing diet (OID) in C57BL/6 mice. Social isolation and OID impaired insulin and glucose sensitivity. In socially isolated, OID-fed mice (I-OID), insulin resistance was linked to reduced Pparg expression and increased neuropeptide Y levels, but in group-housed OID fed mice (G-OID), it was linked to increased leptin and reduced adiponectin levels, indicating that the pathways leading to insulin resistance are different. Carcinogen-induced mammary tumorigenesis was significantly higher in I-OID mice than in the other groups, but cancer risk was also increased in socially isolated, control diet-fed mice (I-C) and G-OID mice compared with that in controls. Unfolded protein response (UPR) signaling (GRP78; IRE1) was upregulated in the mammary glands of OID-fed mice, but not in control diet-fed, socially isolated I-C mice. In contrast, expression of BECLIN1, ATG7 and LC3II were increased, and p62 was downregulated by social isolation, indicating increased autophagy. In the mammary glands of socially isolated mice, but not in G-OID mice, mRNA expressions of p53 and the p53-regulated autophagy inducer Dram1 were upregulated, and nuclear p53 staining was strong. Our findings further indicated that autophagy and tumorigenesis were not increased in Atg7(+/-) mice kept in social isolation and fed OID. Thus, social isolation may increase breast cancer risk by inducing autophagy, independent of changes in body weight.

Elevated levels of autophagy-related marker ULK1 and mitochondrion-associated autophagy inhibitor LRPPRC are associated with biochemical progression and overall survival after androgen deprivation therapy in patients with metastatic prostate cancer

AIM

To evaluate the expression levels and prognostic significance of autophagy-related markers, UNC-51-like kinase1 (ULK1), Beclin1, microtubule-associated protein light chain 3 (LC3), autophagy-related gene 5 (ATG5) and mitochondrion-associated autophagy inhibitor, LRPPRC, in patients with metastatic prostate cancer (PCa) after androgen deprivation therapy (ADT).

METHODS

Expressions of ULK1, Beclin1, LC3, ATG5 and LRPPRC were assessed by immunohistochemical examination in 198 patients with metastatic PCa who were receiving ADT (goserelin and bicalutamide).

RESULTS

High expression levels of LRPPRC and ULK1were significantly associated with Gleason score, serum prostate-specific antigen (PSA) levels, PSA levels after ADT and number of metastatic sites. High expression of ULK1 in patients with concomitant high expression of LRPPRC was significantly associated with multiple metastases, shorter biochemical progression (BCP)-free survival and shorter overall survival (OS). ULK1 expression, LRPPRC expression, Gleason score, PSA levels after ADT and number of metastatic sites were independently associated with shorter BCP-free survival and OS on multivariate analysis. Furthermore, two-year BCP rate of patients with ≥3 risk factors was found to be significantly higher as compared with that of patients with ≤1 and 2 risk factors. Three-year OS rate in patients with ≥3 risk factors was significantly lower than that of those with ≤1 and 2 risk factors.

CONCLUSIONS

High expression of ULK1 concomitant with high expression of LRPPRC may serve as useful markers for shorter BCP-free survival and OS in patients with metastatic PCa after ADT.

The epithelial polarity regulator LGALS9/galectin-9 induces fatal frustrated autophagy in KRAS mutant colon carcinoma that depends on elevated basal autophagic flux

Oncogenic mutation of KRAS (Kirsten rat sarcoma viral oncogene homolog) in colorectal cancer (CRC) confers resistance to both chemotherapy and EGFR (epidermal growth factor receptor)-targeted therapy. We uncovered that KRAS mutant (KRAS^mut) CRC is uniquely sensitive to treatment with recombinant LGALS9/Galectin-9 (rLGALS9), a recently established regulator of epithelial polarity. Upon treatment of CRC cells, rLGALS9 rapidly internalizes via early- and late-endosomes and accumulates in the lysosomal compartment. Treatment with rLGALS9 is accompanied by induction of frustrated autophagy in KRAS^mut CRC, but not in CRC with BRAF (B-Raf proto-oncogene, serine/threonine kinase) mutations (BRAF^mut). In KRAS^mut CRC, rLGALS9 acts as a lysosomal inhibitor that inhibits autophagosome-lysosome fusion, leading to autophagosome accumulation, excessive lysosomal swelling and cell death. This antitumor activity of rLGALS9 directly correlates with elevated basal autophagic flux in KRAS^mut cancer cells. Thus, rLGALS9 has potent antitumor activity toward refractory KRAS^mut CRC cells that may be exploitable for therapeutic use.

Autophagy-based survival prognosis in human colorectal carcinoma

The role of autophagy in cancers is controversial. Here we aim to determine the prognostic significance of autophagy in colorectal carcinoma patients, thereby allowing more rational development of therapeutic strategies. Through transmission electron microscopy, our data first demonstrated high frequency of defective mitochondria was strongly associated with poor overall survival in colorectal carcinoma. Next immunohistochemical study showed the expressions of Beclin 1, LC3B and Bcl-xL in both the center of tumor and adjacent noncancerous mucosal region were also correlated with overall survivals. We developed an autophagy signature for prognosis based on these three major autophagic proteins, further analysis suggested it was an independent prognostic biomarker and had its value even within single clinical stage. Combined TNM stage and this signature could significantly improve the accuracy of survival prognosis. To validate these immunohistochemical results, an internal testing cohort and an independent population were also included. Our findings suggest that autophagy plays an important role in the clinical cancer progression. Therefore autophagic proteins may be valuable prognostic biomarkers in the therapy of colorectal carcinoma and possibly other types of cancers.

Upregulation of CD44v6 contributes to acquired chemoresistance via the modulation of autophagy in colon cancer SW480 cells

The CD44 isoform containing variant exon v6 (CD44v6) plays an important role in the progression, metastasis, and prognosis of colorectal cancer (CRC). Recently, it was found that CD44v6 is involved in acquired drug resistance. This study aimed to investigate the molecular mechanism of CD44v6 in the resistance of CRC cells to chemotherapy. A stable CD44v6 overexpression model in SW480 cells was established via lentiviral transduction. The chemosensitivity of cells to 5-fluorouracil (5-FU) and oxaliplatin (L-OHP) was determined by cell counting kit (CCK)-8, lactate dehydrogenase (LDH) release, and colony formation assays. Immunohistochemical staining of CD44v6 was performed in human CRC tissues. The key components in cell apoptosis, drug efflux and metabolism, mismatch repair, autophagy, epithelial-mesenchymal transition (EMT), and the PI3K-Akt and MAPK-Ras-Erk1/2 pathways were assessed using flow cytometry, quantitative real-time polymerase chain reaction (PCR), and western blot assays. The CD44v6 overexpression cells showed a higher viability, a lower LDH release rate, and an increased clonogenicity than the control cells under drug treatment. Moreover, overexpression of CD44v6 resulted in enhanced autophagy flux, EMT, and phosphorylation of Akt and Erk in the presence of drugs. Furthermore, high CD44v6 expression in the primary tumor was closely associated with an early recurrence in CRC patients who underwent curative surgery and adjuvant chemotherapy. In conclusion, overexpression of CD44v6 contributes to chemoresistance in SW480 cells under cytotoxic stress via the modulation of autophagy, EMT, and activation of the PI3K-Akt and MAPK-Ras-Erk pathways.

Pan-Bcl-2 inhibitor Obatoclax is a potent late stage autophagy inhibitor in colorectal cancer cells independent of canonical autophagy signaling

BACKGROUND

Colorectal cancer is the third most common malignancy in humans and novel therapeutic approaches are urgently needed. Autophagy is an evolutionarily highly conserved cellular process by which cells collect unnecessary organelles or misfolded proteins and subsequently degrade them in vesicular structures in order to refuel cells with energy. Dysregulation of the complex autophagy signaling network has been shown to contribute to the onset and progression of cancer in various models. The Bcl-2 family of proteins comprises central regulators of apoptosis signaling and has been linked to processes involved in autophagy. The antiapoptotic members of the Bcl-2 family of proteins have been identified as promising anticancer drug targets and small molecules inhibiting those proteins are in clinical trials.

METHODS

Flow cytometry and colorimetric assays were used to assess cell growth and cell death. Long term 3D cell culture was used to assess autophagy in a tissue mimicking environment in vitro. RNA interference was applied to modulate autophagy signaling. Immunoblotting and q-RT PCR were used to investigate autophagy signaling. Immunohistochemistry and fluorescence microscopy were used to detect autophagosome formation and autophagy flux.

RESULTS

This study demonstrates that autophagy inhibition by obatoclax induces cell death in colorectal cancer (CRC) cells in an autophagy prone environment. Here, we demonstrate that pan-Bcl-2 inhibition by obatoclax causes a striking, late stage inhibition of autophagy in CRC cells. In contrast, ABT-737, a Mcl-1 sparing Bcl-2 inhibitor, failed to interfere with autophagy signaling. Accumulation of p62 as well as Light Chain 3 (LC3) was observed in cells treated with obatoclax. Autophagy inhibition caused by obatoclax is further augmented in stressful conditions such as starvation. Furthermore, our data demonstrate that inhibition of autophagy caused by obatoclax is independent of the essential pro-autophagy proteins Beclin-1, Atg7 and Atg12.

CONCLUSIONS

The objective of this study was to dissect the contribution of Bcl-2 proteins to autophagy in CRC cells and to explore the potential of Bcl-2 inhibitors for autophagy modulation. Collectively, our data argue for a Beclin-1 independent autophagy inhibition by obatoclax. Based on this study, we recommend the concept of autophagy inhibition as therapeutic strategy for CRC.

Photodynamic therapy in colorectal cancer treatment--The state of the art in preclinical research

BACKGROUND

Photodynamic therapy (PDT) is used in many different oncologic fields. Also in gastroenterology, where have been a few attempts to treat both the premalignant lesion and advanced colorectal cancer (CRC). This review aims to give a general overview of preclinical photodynamic studies related to CRC cells and animal studies of photodynamic effects related to CRC treatment to emphasize their potential in study of PDT mechanism, safety and efficiency to translate these results into clinical benefit in CRC treatment.

MATERIALS AND METHOD

Literature on in vitro preclinical photodynamic studies related to CRC cells and animal studies of photodynamic effects related to CRC treatment with the fallowing medical subject headings search terms: colorectal cancer, photodynamic therapy, photosensitizer(s), in vitro, cell culture(s), in vivo, animal experiment(s). The articles were selected by their relevance to the topic.

RESULTS

The majority of preclinical studies concerning possibility of PDT application in colon and rectal cancer is focused on phototoxic action of photosensitizers toward cultured colorectal tumor cells in vitro. The purposes of animal experiments are usually elucidation of mechanisms of observed photodynamic effects in scale of organism, estimation of PDT safety and efficiency and translation of these results into clinical benefit.

CONCLUDING REMARKS

In vitro photodynamic studies and animal experiments can be useful for studies of mechanisms and efficiency of photodynamic method as a start point on PDT clinical research. The primary disadvantage of in vitro experiments is a risk of over-interpretation of their results during extrapolation to the entire CRC.

Gene of the month: PIK3CA

PIK3CA encodes the p110α catalytic subunit of phosphatidylinositol 3-kinase (PI3K) which through its role in the PI3K/Akt pathway is important for the regulation of important cellular functions such as proliferation, metabolism and protein synthesis, angiogenesis and apoptosis. Mutations in PIK3CA are known to be involved in a wide range of human cancers and mutant PIK3CA is thought to act as an oncogene. The specific PIK3CA inhibitor, NVP-BYL719, has displayed promising results in cancer therapy and is currently under clinical trials. Furthermore, PI3K regulates autophagy, a cellular process that recycles proteins and organelles through lysosomal degradation and has recently been recognised as an attractive therapeutic target due to its pro- and anti-cancer properties. Several studies have attempted to investigate the effects of combining the inhibition of both PI3K and autophagy in cancer therapy, and an in vivo model has demonstrated that the combined use of a concomitant PI3K and autophagy inhibitor induced apoptosis in glioma cells.

Screening methods for AMP-activated protein kinase modulators: a patent review

INTRODUCTION

AMP-activated protein kinase (AMPK) functions as a cellular energy gauge that maintains cellular homeostasis and has been suggested to play important roles in tumorigenesis, lifespan and autophagy. Accordingly, AMPK is a potential target of drugs for controlling a growing number of human diseases ranging from metabolic disorders to cancer, highlighting the need for rational and robust screening systems for identifying compounds that modulate AMPK.

AREAS COVERED

The relevant screening methods in the patent and scientific literature were analyzed, and key features of direct AMPK modulators are discussed in the context of their physiological relevance and the three-dimensional structure of the AMPK complex.

EXPERT OPINION

The mechanism of action of modulators is important in designing drugs with enhanced efficacy, specificity and stability. Most patented assay formats for identifying AMPK modulators are based on classical enzyme assays that monitor AMPK activity or changes in AMPK-dependent cellular physiology. However, these systems do not provide information about underlying mechanisms. Two patented assay systems use a specific domain or the three-dimensional structure of AMPK to identify AMPK modulators. The recent identification of two AMPK modulators, A-769662 and C-2 (or its prodrug, C-13), suggests the promise of structure-based assays in discovering more potent and specific modulators of AMPK.