Aquaporin 3 facilitates chemoresistance in gastric cancer cells to cisplatin via autophagy

Aquaporins in colorectal cancer: exploring their role in tumorigenesis, metastasis, and drug response

Aquaporins (AQPs) are small, integral proteins facilitating water transport across plasma cell membranes in response to osmotic gradients. This family has 13 unique members (AQP0-12), which can also transport glycerol, urea, gases, and other salute small molecules. AQPs play a crucial role in the regulation of different cellular processes, including metabolism, migration, immunity, barrier function, and angiogenesis. These proteins are found to aberrantly overexpress in various cancers, including colorectal cancer (CRC). Growing evidence has explored AQPs as a potential diagnostic biomarker and therapeutic target in different cancers. However, there is no comprehensive review compiling the available information on the crucial role of AQPs in the context of colorectal cancer. This review highlights the significance of AQPs as the biomarker and regulator of tumor cells metabolism. In addition, the proliferation, angiogenesis, and metastasis of tumor cells related to AQPs expression as well as function are discussed. Understanding the AQPs prominent role in chemotherapy resistance is of great importance clinically.

Dysregulation of autophagy in gastric carcinoma: Pathways to tumor progression and resistance to therapy

The considerable death rates and lack of symptoms in early stages of gastric cancer (GC) make it a major health problem worldwide. One of the most prominent risk factors is infection with Helicobacter pylori. Many biological processes, including those linked with cell death, are disrupted in GC. The cellular "self-digestion" mechanism necessary for regular balance maintenance, autophagy, is at the center of this disturbance. Misregulation of autophagy, however, plays a role in the development of GC. In this review, we will examine how autophagy interacts with other cell death processes, such as apoptosis and ferroptosis, and how it affects the progression of GC. In addition to wonderful its role in the epithelial-mesenchymal transition, it is engaged in GC metastasis. The role of autophagy in GC in promoting drug resistance stands out. There is growing interest in modulating autophagy for GC treatment, with research focusing on natural compounds, small-molecule inhibitors, and nanoparticles. These approaches could lead to breakthroughs in GC therapy, offering new hope in the fight against this challenging disease.

SCFFBXW5-mediated degradation of AQP3 suppresses autophagic cell death through the PDPK1-AKT-MTOR axis in hepatocellular carcinoma cells

AQP3 (aquaporin 3 (Gill blood group)), a member of the AQP family, is an aquaglyceroporin which transports water, glycerol and small solutes across the plasma membrane. Beyond its role in fluid transport, AQP3 plays a significant role in regulating various aspects of tumor cell behavior, including cell proliferation, migration, and invasion. Nevertheless, the underlying regulatory mechanism of AQP3 in tumors remains unclear. Here, for the first time, we report that AQP3 is a direct target for ubiquitination by the SCFFBXW5 complex. In addition, we revealed that downregulation of FBXW5 significantly induced AQP3 expression to prompt macroautophagic/autophagic cell death in hepatocellular carcinoma (HCC) cells. Mechanistically, AQP3 accumulation induced by FBXW5 knockdown led to the degradation of PDPK1/PDK1 in a lysosomal-dependent manner, thus inactivating the AKT-MTOR pathway and inducing autophagic death in HCC. Taken together, our findings revealed a previously undiscovered regulatory mechanism through which FBXW5 degraded AQP3 to suppress autophagic cell death via the PDPK1-AKT-MTOR axis in HCC cells.Abbreviation: BafA1: bafilomycin A1; CQ: chloroquine; CRL: CUL-Ring E3 ubiquitin ligases; FBXW5: F-box and WD repeat domain containing 5; HCC: hepatocellular carcinoma; HSPA8/HSC70: heat shock protein family A (Hsp70) member 8; 3-MA: 3-methyladenine; PDPK1/PDK1: 3-phosphoinositide dependent protein kinase 1; RBX1/ROC1: ring-box 1; SKP1: S-phase kinase associated protein 1; SCF: SKP1-CUL1-F-box protein.

Autophagy induced by Helicobacter Pylori infection can lead to gastric cancer dormancy, metastasis, and recurrence: new insights

According to the findings of recent research, Helicobacter Pylori (H. pylori) infection is not only the primary cause of gastric cancer (GC), but it is also linked to the spread and invasion of GC through a number of processes and factors that contribute to virulence. In this study, we discussed that H. pylori infection can increase autophagy in GC tumor cells, leading to poor prognosis in such patients. Until now, the main concerns have been focused on H. pylori's role in GC development. According to our hypothesis, however, H. pylori infection may also lead to GC dormancy, metastasis, and recurrence by stimulating autophagy. Therefore, understanding how H. pylori possess these processes through its virulence factors and various microRNAs can open new windows for providing new prevention and/or therapeutic approaches to combat GC dormancy, metastasis, and recurrence which can occur in GC patients with H. pylori infection with targeting autophagy and eradicating H. pylori infection.

Targeted therapy for non-small-cell lung cancer: New insights into regulated cell death combined with immunotherapy

Non-small-cell lung cancer (NSCLC), which has a high rate of metastatic spread and drug resistance, is the most common subtype of lung cancer. Therefore, NSCLC patients have a very poor prognosis and a very low chance of survival. Human cancers are closely linked to regulated cell death (RCD), such as apoptosis, autophagy, ferroptosis, pyroptosis, and necroptosis. Currently, small-molecule compounds targeting various types of RCD have shown potential as anticancer treatments. Moreover, RCD appears to be a specific part of the antitumor immune response; hence, the combination of RCD and immunotherapy might increase the inhibitory effect of therapy on tumor growth. In this review, we summarize small-molecule compounds used for the treatment of NSCLC by focusing on RCD and pharmacological systems. In addition, we describe the current research status of an immunotherapy combined with an RCD-based regimen for NSCLC, providing new ideas for targeting RCD pathways in combination with immunotherapy for patients with NSCLC in the future.

Microorganism-regulated autophagy in gastrointestinal cancer

Gastrointestinal cancer has always been one of the most urgent problems to be solved, and it has become a major global health issue. Microorganisms in the gastrointestinal tract regulate normal physiological and pathological processes. Accumulating evidence reveals the role of the imbalance in the microbial community during tumorigenesis. Autophagy is an important intracellular homeostatic process, where defective proteins and organelles are degraded and recycled under stress. Autophagy plays a dual role in tumors as both tumor suppressor and tumor promoter. Many studies have shown that autophagy plays an important role in response to microbial infection. Here, we provide an overview on the regulation of the autophagy signaling pathway by microorganisms in gastrointestinal cancer.

Aquaporin water channels: roles beyond renal water handling

Aquaporin (AQP) water channels are pivotal to renal water handling and therefore in the regulation of body water homeostasis. However, beyond the kidney, AQPs facilitate water reabsorption and secretion in other cells and tissues, including sweat and salivary glands and the gastrointestinal tract. A growing body of evidence has also revealed that AQPs not only facilitate the transport of water but also the transport of several small molecules and gases such as glycerol, H2O2, ions and CO2. Moreover, AQPs are increasingly understood to contribute to various cellular processes, including cellular migration, adhesion and polarity, and to act upstream of several intracellular and intercellular signalling pathways to regulate processes such as cell proliferation, apoptosis and cell invasiveness. Of note, several AQPs are highly expressed in multiple cancers, where their expression can correlate with the spread of cancerous cells to lymph nodes and alter the response of cancers to conventional chemotherapeutics. These data suggest that AQPs have diverse roles in various homeostatic and physiological systems and may be exploited for prognostics and therapeutic interventions.

Targeting mitochondria as a potential therapeutic strategy against chemoresistance in cancer

The importance of mitochondria is not only limited to energy generation but also in several physical and chemical processes critical for cell survival. Mitochondria play an essential role in cellular apoptosis, calcium ion transport and cellular metabolism. Mutation in the nuclear and mitochondrial genes, altered oncogenes/tumor suppressor genes, and deregulated signalling for cell viability are major reasons for cancer progression and chemoresistance. The development of drug resistance in cancer patients is a major challenge in cancer treatment as the resistant cells are often more aggressive. The drug resistant cells of numerous cancer types exhibit the deregulation of mitochondrial function. The increased biogenesis of mitochondria and its dynamic alteration contribute to developing resistance. Further, a small subpopulation of cancer stem cells in the heterogeneous tumor is primarily responsible for chemoresistance and has an attribute of mitochondrial dysfunction. This review highlights the critical role of mitochondrial dysfunction in chemoresistance in cancer cells through the processes of apoptosis, autophagy/mitophagy, and cancer stemness. Mitochondria-targeted therapeutic strategies might help reduce cancer progression and chemoresistance induced by various cancer drugs.

Mitochondrial dysfunction and chromatin changes with autophagy-mediated survival in doxorubicin resistant cancer cell lines

Acquired chemoresistance against doxorubicin remains an obstacle in long-term treatment. The comprehensive molecular mechanism underlying the acquirement of doxorubicin resistance has not been reported. The objective of the present study is to understand the survival strategies and investigate alternate treatments for doxorubicin-resistant cervical and liver cancer cells. In this study, doxorubicin-resistant sublines were established by continuous incremental exposure of the drug to parental cervical and liver cancer cells. The transcriptome data in drug-resistant model revealed downregulated energy production pathways like glycolysis, oxidative phosphorylation, and mTOR signalling. This resulted in slow proliferation and altered mitochondrial changes in doxorubicin-resistant cells. The altered metabolic state of the resistant cells was associated with hypo-acetylation of chromatin. Pre-treatment with HDACi sensitized the drug-resistant cells to doxorubicin by increased drug accumulation in the cells, thereby leading to apoptosis. Additionally, we demonstrated that autophagy gets activated in doxorubicin-resistant cervical and liver cancer cells. Autophagy acts as pro-survival mechanism in resistant cells, as inhibition of autophagy leads to cell death. In conclusion, the data highlights survival ability of resistant cells with mitochondrial dysfunction, altered chromatin state, and pro-survival autophagy. The study proposes targeting chromatin alteration with the combinatorial treatment of HDACi with doxorubicin or survival mechanism through autophagy inhibitor against doxorubicin-resistant cancer phenotype.

Solanine Represses Gastric Cancer Growth by Mediating Autophagy Through AAMDC/MYC/ATF4/Sesn2 Signaling Pathway

Purpose

Solanine is the main component of the plant Solanum, which has been shown to provide growth-limiting activities in a variety of human cancers. However, little is known about its function in gastric cancer (GC).

Methods

We investigated the effect of solanine on GC in vivo and in vitro. The inhibition rate of solanine on the tumor was observed by constructing a subcutaneous tumor in nude mice. Morphological changes were analyzed with H&E staining. The expression of ATF4 was detected by IF analysis. MTT assays, EdU staining, and colony formation assays were used to detect the inhibition rate of solanine on GC cells. Matrigel transwells were used to detect the invasion of GC cells. Cell migration was measured using the wound healing assay. The flow cytometric analysis was used to monitor changes in the cell cycle and cell apoptosis. Western blotting was used to detect major proteins in cells and tumors.

Results

Solanine suppressed gastric tumorigenesis. Solanine also inhibited the proliferation, invasion and mitigation of GC cells, and induced cell cycle arrest and apoptosis in vitro. Moreover, the growth-limiting activities of solanine in gastric cancer were related to the suppression of the AAMDC/MYC/ATF4/Sesn2 pathway-mediated autophagy. Overexpression of AAMDC reversed the inhibitory effect of solanine on autophagy and gastric cancer.

Conclusion

In summary, our findings indicate that solanine confers growth-limiting activities by deactivating the AAMDC-regulated autophagy in gastric cancer.

CircRNA: A new class of targets for gastric cancer drug resistance therapy

Gastric cancer (GC) is one of the most common malignancies worldwide. Patients with advanced GC need palliative care to ensure survival. This includes the use of chemotherapy agents, such as cisplatin, 5-fluorouracil, oxaliplatin, paclitaxel, and pemetrexed, as well as targeted agents. However, the emergence of drug resistance evidence in poor patient outcomes and poor prognosis is a motivation to determine the specific mechanism of drug resistance. Interestingly, circular RNAs (circRNAs) play an important part in the carcinogenesis and progression of GC and are involved in GC drug resistance. This review systematically summarizes the functions and mechanisms of circRNAs underlying GC drug resistance, especially chemoresistance. It also emphasizes that circRNAs can serve as promising targets for improving drug resistance and therapeutic efficacy.

Molecular mechanism of aquaporin 3 (AQP3) regulating by LMP2A and its crosstalk with 4E-BP1 via ERK signaling pathway in EBV-associated gastric cancer

Aquaporin 3(AQP3) is involved in epithelial-mesenchymal transformation of tumor cells and is closely related to the occurrence and development of tumors. However, the regulatory mechanism and function of AQP3 in EBV-associated gastric cancer (EBVaGC) are still poorly understood. This study aims to explore the regulatory effect of EBV on AQP3 and the cross talk of AQP3 with EIF4E-binding proteins 1(4E-BP1) in EBVaGC. The effect of LMP2A on the expression of AQP3 and 4E-BP1 was analyzed using real-time PCR and western blotting. The biological functions of AQP3 and 4E-BP1 in gastric cancer cells were detected by cell biological experiments. In addition, we examined the role of mTOR and ERK signaling pathways in the LMP2A/AQP3/4E-BP1 regulatory axis. We found that LMP2A could down-regulate AQP3 expression by inhibiting the activation of mTOR signaling pathway, and further promote autophagy and migration of gastric cancer cells. AQP3 up-regulated the expression of 4E-BP1 and its phosphorylated protein by activating ERK signaling pathway, thus promoting the autophagy and proliferation of gastric cancer cells. In conclusion, EBV-encoded LMP2A inhibits AQP3 expression, and further participates in cell proliferation, migration and autophagy through the mTOR/AQP3/ERK/4E-BP1 axis.

AQP5 complements LGR5 to determine the fates of gastric cancer stem cells through regulating ULK1 ubiquitination

BACKGROUND

Cancer stem cells (CSCs) are regarded as the "seed cells" for tumorigenesis, metastasis, recurrence and drug resistance. However, specific surface markers of CSCs of different origins have not been documented.

METHODS

Single-cell sequencing was used to analyze the highly expressed genes in cancer stem cells of gastric cancer patients, and it was verified that AQP5 was specifically highly expressed in gastric cancer stem cells (GC-CSCs) in vivo and in vitro. The effect of AQP5-promoting LGR5 on the malignant biological function of GC-CSCs was investigated. The mechanism by which AQP5 affects GC-CSCs was explored through transcriptome sequencing, proteomic detection, mass spectrometry, etc. RESULTS: We report the identification and validation of AQP5 as a potentially specific surface marker of GC-CSCs. AQP5 was significantly upregulated in CSCs isolated from gastric cancer patients and in spheroid cells, and AQP5 was coexpressed with the canonical stem marker LGR5. Biologically, AQP5 promoted the sphere formation, proliferation, migration and invasion of GC cells in vitro and enhanced tumorigenesis in vivo. Furthermore, AQP5 coordinated with LGR5 and synergistically promoted the tumorigenesis of GC-CSCs. At the mechanistic level, AQP5 activated autophagy by inducing the LC3I/LC3II transformation in GC-CSCs, which was crucial for the biological functions of AQP5. Finally, we demonstrated that AQP5 recruited the E3 ligase TRIM21 to the key autophagy protein ULK1 and induced the K63-mediated ubiquitination of ULK1.

CONCLUSIONS

We elucidate a novel surface marker, AQP5, which is specifically expressed by GC-CSCs. Furthermore, our study creates a link between AQP5 and LGR5 and highlights the necessity of targeting both surface markers simultaneously as a promising approach for the treatment of gastric cancer patients.

KLF5-mediated aquaporin 3 activated autophagy to facilitate cisplatin resistance of gastric cancer

BACKGROUND

Resistance to chemotherapeutic drugs limits the control of gastric cancer (GC) development. The study intended to probe into the mechanism of aquaporin 3 (AQP3) on the chemoresistance of GC.

METHODS

Cisplatin (CDDP)-resistant cells were constructed. Parental AGS and HGC-27 cells and their respective CDDP-resistant cells were transfected with AQP3 overexpression plasmid, AQP3 short hairpin RNA (sh-AQP3) and sh-Kruppel-like factor 5 (shKLF5). The expressions of AQP3 and factors related to autophagy (LC3 I, LC3 II, Atg5, Beclin-1, p62)/epithelial-mesenchymal transition (EMT; E-cadherin and snail) were assessed by Western blot and qRT-PCR. Cell counting kit-8 assay was adopted to test cell viability and half maximal inhibitory concentration (IC 50) was determined. Transwell assay was used for the examination of cell migration and invasion. The regulatory relationship of AQP3 and KLF5 was tested by chromatin immunoprecipitation (ChIP) and dual luciferase reporter assays.

RESULTS

AQP3 was highly-expressed in GC cells and its level was even higher in CDDP-resistant GC cells. AQP3 silencing inhibited viability, autophagy and EMT in CDDP-resistant GC cells, while AQP3 overexpression had the opposite effect. KLF5 positively modulated AQP3 in GC cells resistant to CDDP. KLF5 knockdown reversed AQP3-induced autophagy, viability, migration, invasion and EMT in CDDP-resistant GC cells.

CONCLUSION

KLF5-modulated AQP3 activated autophagy to facilitate the resistance of GC to CDDP.

LINC-PINT suppresses cisplatin resistance in gastric cancer by inhibiting autophagy activation via epigenetic silencing of ATG5 by EZH2

Resistance to cisplatin (DDP) is a major obstacle in the clinical treatment of advanced gastric cancer (GC). Long noncoding RNA (lncRNA) play a significant regulatory role in the development and drug resistance of GC. In this study, we reported that the lncRNA LINC-PINT was downregulated in DDP-resistant GC cells. Functional studies showed that LINC-PINT inhibited proliferation and migration of DDP-resistant GC cells in vitro, and overexpression of LINC-PINT could enhance the sensitivity of DDP-resistant GC cells to DDP. Further investigation revealed that LINC-PINT recruited enhancer of zeste homolog 2 (EZH2) to the promotor of ATG5 to inhibit its transcription, leading to the suppression of autophagy and DDP resensitization. Collectively, our results revealed how the LINC-PINT/EZH2/ATG5 axis regulates autophagy and DDP resistance in GC. These data suggest that LINC-PINT may be a potential therapeutic target in GC.

Clinical value and molecular mechanism of AQGPs in different tumors

Aquaglyceroporins (AQGPs), including AQP3, AQP7, AQP9, and AQP10, are transmembrane channels that allow small solutes across biological membranes, such as water, glycerol, H₂O₂, and so on. Increasing evidence suggests that they play critical roles in cancer. Overexpression or knockdown of AQGPs can promote or inhibit cancer cell proliferation, migration, invasion, apoptosis, epithelial-mesenchymal transition and metastasis, and the expression levels of AQGPs are closely linked to the prognosis of cancer patients. Here, we provide a comprehensive and detailed review to discuss the expression patterns of AQGPs in different cancers as well as the relationship between the expression patterns and prognosis. Then, we elaborate the relevance between AQGPs and malignant behaviors in cancer as well as the latent upstream regulators and downstream targets or signaling pathways of AQGPs. Finally, we summarize the potential clinical value in cancer treatment. This review will provide us with new ideas and thoughts for subsequent cancer therapy specifically targeting AQGPs.

Epigenetic regulation of autophagy in gastrointestinal cancers

The development of novel therapeutic approaches is necessary to manage gastrointestinal cancers (GICs). Considering the effective molecular mechanisms involved in tumor growth, the therapeutic response is pivotal in this process. Autophagy is a highly conserved catabolic process that acts as a double-edged sword in tumorigenesis and tumor inhibition in a context-dependent manner. Depending on the stage of malignancy and cellular origin of the tumor, autophagy might result in cancer cell survival or death during the GICs' progression. Moreover, autophagy can prevent the progression of GIC in the early stages but leads to chemoresistance in advanced stages. Therefore, targeting specific arms of autophagy could be a promising strategy in the prevention of chemoresistance and treatment of GIC. It has been revealed that autophagy is a cytoplasmic event that is subject to transcriptional and epigenetic regulation inside the nucleus. The effect of epigenetic regulation (including DNA methylation, histone modification, and expression of non-coding RNAs (ncRNAs) in cellular fate is still not completely understood. Recent findings have indicated that epigenetic alterations can modify several genes and modulators, eventually leading to inhibition or promotion of autophagy in different cancer stages, and mediating chemoresistance or chemosensitivity. The current review focuses on the links between autophagy and epigenetics in GICs and discusses: 1) How autophagy and epigenetics are linked in GICs, by considering different epigenetic mechanisms; 2) how epigenetics may be involved in the alteration of cancer-related phenotypes, including cell proliferation, invasion, and migration; and 3) how epidrugs modulate autophagy in GICs to overcome chemoresistance.

CARM1 promotes gastric cancer progression by regulating TFE3 mediated autophagy enhancement through the cytoplasmic AMPK-mTOR and nuclear AMPK-CARM1-TFE3 signaling pathways

BACKGROUND

The role of CARM1 in tumors is inconsistent. It acts as an oncogene in most cancers but it inhibits the progression of liver and pancreatic cancers. CARM1 has recently been reported to regulate autophagy, but this function is also context-dependent. However, the effect of CARM1 on gastric cancer (GC) has not been studied. We aimed to explore whether CARM1 was involved in the progression of GC by regulating autophagy.

METHODS

The clinical values of CARM1 and autophagy in GC were evaluated by immunohistochemistry and qRT-PCR. Transmission electron microscopy, immunofluorescence and western blotting were employed to identify autophagy. The role of CARM1 in GC was investigated by CCK-8, colony formation and flow cytometry assays in vitro and a xenograft model in vivo. Immunoprecipitation assays were performed to determine the interaction of CARM1 and TFE3.

RESULTS

CARM1 was upregulated in clinical GC tissues and cell lines, and higher CARM1 expression predicted worse prognosis. CARM1 enhanced GC cell proliferation, facilitated G1-S transition and inhibited ER stress-induced apoptosis by regulating autophagy. Importantly, treatment with a CARM1 inhibitor rescued the tumor-promoting effects of CARM1 both in vitro and in vivo. Furthermore, we demonstrated that CARM1 promoted TFE3 nuclear translocation to induce autophagy through the cytoplasmic AMPK-mTOR and nuclear AMPK-CARM1-TFE3 signaling pathways.

CONCLUSION

CARM1 promoted GC cell proliferation, accelerated G1-S transition and reduced ER stress-induced apoptosis by regulating autophagy. Mechanistically, CARM1 triggered autophagy by facilitating TFE3 nuclear translocation through the AMPK-mTOR and AMPK-CARM1-TFE3 signaling pathways.

SP1-Induced Upregulation of lncRNA LINC00659 Promotes Tumour Progression in Gastric Cancer by Regulating miR-370/AQP3 Axis

Growing evidence demonstrates that long noncoding RNAs (lncRNAs) play critical roles in various human tumors. LncRNA LINC00659 (LINC00659) is a newly identified lncRNA and its roles in tumors remain largely unclear. In this study, we elucidated the potential functions and molecular mechanisms of LINC00659 on the biological behaviors of gastric cancer (GC), and also explored its clinical significance. We firstly demonstrated that LINC00659 levels were distinctly up-regulated in both GC specimens and cells using bioinformatics analysis and RT-PCR. The results of ChIP assays and luciferase reporter assays confirmed that upregulation of LINC00659 was activated by SP1 in GC. Clinical assays revealed that higher levels of LINC00659 were associated with TNM stage, lymphatic metastasis, and poorer prognosis. Moreover, LINC00659 was confirmed to be an independent prognostic marker for the patients with GC using multivariate assays. Lost-of-function assays indicated that knockdown of LINC00659 suppressed the proliferation, metastasis, and EMT progress of GC cells in vitro. Mechanistic investigation indicated that LINC00659 served as a competing endogenous RNA (ceRNA) for miR-370, thereby resulting in the upregulation of leading to the depression of its endogenous target gene AQP3. Overall, our present study revealed that the LINC00659/miR-370/AQP3 axis contributes to GC progression, which may provide clues for the exploration of cancer biomarkers and therapeutic targets for GC.

The Implication of Autophagy in Gastric Cancer Progression

Gastric cancer is the fifth most common malignancy and the third leading cause of cancer-related death worldwide. The three entirely variable entities have distinct epidemiology, molecular characteristics, prognosis, and strategies for clinical management. However, many gastric tumors appear to be resistant to current chemotherapeutic agents. Moreover, a significant number of gastric cancer patients, with a lack of optimal treatment strategies, have reduced survival. In recent years, multiple research data have highlighted the importance of autophagy, an essential catabolic process of cytoplasmic component digestion, in cancer. The role of autophagy as a tumor suppressor or tumor promoter mechanism remains controversial. The multistep nature of the autophagy process offers a wide array of targetable points for designing novel chemotherapeutic strategies. The purpose of this review is to summarize the current knowledge regarding the interplay between gastric cancer development and the autophagy process and decipher the role of autophagy in this kind of cancer. A plethora of different agents that direct or indirect target autophagy may be a novel therapeutic approach for gastric cancer patients.

Prognostic Autophagy-Related Genes of Gastric Cancer Patients on Chemotherapy

Background: Chemotherapy resistance based on fluorouracil and cisplatin is one of the most encountered postoperative clinical problems in patients diagnosed with gastric cancer (GC), resulting in poor prognosis. Aim of the Study: This study aimed to combine autophagy-related genes (ARGs) to investigate the susceptibility patients with GC to postoperative chemotherapy. Methods: Based on The Cancer Genome Atlas (TCGA) database, gene expression data for GC patients undergoing chemotherapy were integrated and analyzed. Prognostic genes were screened based on univariate and multivariate analysis regression analysis. Subjects were divided into high-risk and low-risk groups according to the median risk score. Kaplan-Meier method was used to evaluate OS and DFS. The accuracy of the prediction was determined by the subject operating characteristic curve analysis. In addition, stratified analyses based on different clinical variables was performed to assess the correlation between risk scores and clinical variables. Quantitative real-time (qRT) PCR was used to verify the expression of CXCR4 in GC tissues and cell lines. Results: A total of nine ARGs related to the prognosis of chemotherapy patients were screened out. Compared with normal gastric mucosa cell, CXCR4 showed elevated expression in GC and was significantly associated with survival. Based on GEO and TCGA databases, the model accurately predicted DFS and OS after chemotherapy. Conclusion: This study established prognostic markers based on nine genes, predicting that ARGs are related to chemotherapy susceptibility of GC patients, which can provide better individualized treatment regimens for clinical practice.

Alteration and dysfunction of ion channels/transporters in a hypoxic microenvironment results in the development and progression of gastric cancer

BACKGROUND

Gastric cancer (GC) is one of the most common malignant cancers in the world and has only few treatment options and, concomitantly, a poor prognosis. It is generally accepted now that the tumor microenvironment, particularly that under hypoxia, plays an important role in cancer development. Hypoxia can regulate the energy metabolism and malignancy of tumor cells by inducing or altering various important factors, such as oxidative stress, reactive oxygen species (ROS), hypoxia-inducible factors (HIFs), autophagy and acidosis. In addition, altered expression and/or dysfunction of ion channels/transporters (ICTs) have been encountered in a variety of human tumors, including GC, and to play an important role in the processes of tumor cell proliferation, migration, invasion and apoptosis. Increasing evidence indicates that ICTs are at least partly involved in interactions between cancer cells and their hypoxic microenvironment. Here, we provide an overview of the different ICTs that regulate or are regulated by hypoxia in GC.

CONCLUSIONS AND PERSPECTIVES

Hypoxia is one of the major obstacles to cancer therapy. Regulating cellular responses and factors under hypoxia can inhibit GC. Similarly, altering the expression or activity of ICTs, such as the application of ion channel inhibitors, can slow down the growth and/or migration of GC cells. Since targeting the hypoxic microenvironment and/or ICTs may be a promising strategy for the treatment of GC, more attention should be paid to the interplay between ICTs and the development and progression of GC in such a microenvironment.

The Therapeutic Potential of Targeting Autophagy in The Treatment of Cancer

Autophagy is a mechanism by which unwanted cellular components are degraded through a pathway that involves the lysosomes and contributes to several pathological conditions such as cancer. Gastrointestinal cancers affect the digestive organs from the esophagus to the anus and are among the most commonly diagnosed cancers globally. The modulation of autophagy using pharmacologic agents potentially offers a great potential for cancer therapy. In this review, some commonly used compounds, together with their molecular target and the mechanism through which they stimulate or block the autophagy pathway as well as their therapeutic benefit in treating patients with gastrointestinal cancers, are summarized.

Initial assessment of suitability of MCF-7 and HepG2 cancer cell lines for AQP3 research in cancer biology

Cancer cell lines are widely used as in vitro models to elucidate biological processes in cancer, and as a tool to evaluate anticancer agents. In fact, the use of an appropriate cancer cell line in cancer research is crucial for investigating new, potential factors involved in carcinogenesis. One of them is aquaporin-3 (AQP3), which is a small, hydrophobic, integral membrane protein with a predominant role in water and glycerol transport. Recently, altered expression of AQP3 has been reported in many types of cancer. Increasing evidence strongly suggests that AQP3 plays a key role in cancer cell proliferation, migration and invasion. In this study, we performed an insightful characteristic of AQP3 location and its protein expression in MCF-7 human breast adenocarcinoma and HepG2 hepatocellular carcinoma cell lines in the context of cancer biology using immunocytochemistry, immunofluorescence and Western blot analyses. AQP3 was found to be located in the cell membrane and cytoplasm of MCF-7 cells, and in the cytoplasm and nuclear membrane of HepG2 cells. Immunoblotting of proteins derived from both cell lines revealed a clear band with a molecular weight of approx. 30 kDa representing an unglycosylated form of AQP3. However, the expression of this protein was higher in MCF-7 than in HepG2. Concluding, our results clearly indicated variability in both the expression levels and subcellular location of the AQP3 protein in MCF-7 and HepG2 cell lines. This leads to the possibility that the expression patterns and subcellular location of AQP3 in the tested cancer cell lines are tissue-of-origin specific, and may be related to the aggressiveness of cancer cells and their mobility.

MiR-877 suppresses gastric cancer progression by downregulating AQP3

OBJECTIVES

Gastric cancer (GC) is the leading cause of cancer-related deaths worldwide; however, the underlying molecular mechanisms of GC remain unclear. This study investigated the role of the miR-877-AQP3 axis in GC tumorigenesis.

METHODS

The levels of miR-877 expression were measured in GC tissues and cell lines by qRT-PCR. Functional assays were performed to elucidate the role of miR-877 in GC development.

RESULTS

Our results showed that miR-877 levels were lower in GC tissues and cell lines compared with the corresponding controls. Additionally, reduced miR-877 levels were associated with unfavorable prognoses. Increased miR-877 expression suppressed proliferation, invasion, and epithelial-mesenchymal transition, while promoting apoptosis in GC cells. Luciferase reporter assays showed that aquaporin 3 (AQP3) was a direct downstream target of miR-877. Overexpression of AQP3 partially rescued the tumor suppressive effects of miR-877 in GC cells. Moreover, miR-877 was negatively correlated with AQP3 mRNA expression in GC tissues.

CONCLUSIONS

This study demonstrated that miR-877 plays a suppressive role in GC tumorigenesis by regulating AQP3.

Overcoming Chemoresistance: Altering pH of Cellular Compartments by Chloroquine and Hydroxychloroquine

Resistance to the anti-cancer effects of chemotherapeutic agents (chemoresistance) is a major issue for people living with cancer and their providers. A diverse set of cellular and inter-organellar signaling changes have been implicated in chemoresistance, but it is still unclear what processes lead to chemoresistance and effective strategies to overcome chemoresistance are lacking. The anti-malaria drugs, chloroquine (CQ) and its derivative hydroxychloroquine (HCQ) are being used for the treatment of various cancers and CQ and HCQ are used in combination with chemotherapeutic drugs to enhance their anti-cancer effects. The widely accepted anti-cancer effect of CQ and HCQ is their ability to inhibit autophagic flux. As diprotic weak bases, CQ and HCQ preferentially accumulate in acidic organelles and neutralize their luminal pH. In addition, CQ and HCQ acidify the cytosolic and extracellular environments; processes implicated in tumorigenesis and cancer. Thus, the anti-cancer effects of CQ and HCQ extend beyond autophagy inhibition. The present review summarizes effects of CQ, HCQ and proton pump inhibitors on pH of various cellular compartments and discuss potential mechanisms underlying their pH-dependent anti-cancer effects. The mechanisms considered here include their ability to de-acidify lysosomes and inhibit autophagosome lysosome fusion, to de-acidify Golgi apparatus and secretory vesicles thus affecting secretion, and to acidify cytoplasm thus disturbing aerobic metabolism. Further, we review the ability of these agents to prevent chemotherapeutic drugs from accumulating in acidic organelles and altering their cytosolic concentrations.

Aquaporins and diseases pathogenesis: From trivial to undeniable involvements, a disease-based point of view

Aquaporins (AQPs), as transmembrane proteins, were primarily identified as water channels with the ability of regulating the transmission of water, glycerol, urea, and other small-sized molecules. The classic view of AQPs involvement in therapeutic plan restricted them and their regulators into managing only a narrow spectrum of the diseases such as diabetes insipidus and the syndrome of inappropriate ADH secretion. However, further investigations performed, especially in the third millennium, has found that their cooperation in water transmission control can be manipulated to handle other burden-imposing diseases such as cirrhosis, heart failure, Meniere's disease, cancer, bullous pemphigoid, eczema, and Sjögren's syndrome.

Prognostic Value of Autophagy-related Proteins in Human Gastric Cancer

Purpose

Autophagy-related proteins (ATG) play a crucial role in autophagy. Recently, the functions of autophagy in cancer have been gathering attention. However, the prognostic value of ATGs in gastric cancer (GC) has not been explored.

Methods

The Kaplan–Meier plotter (KM plotter) online database was used to examine the value of ATGs gene expression levels in overall survival (OS) prediction in GC patients with different clinical stage, differentiation, gender, HER2 status, and therapeutic strategy. In vitro experiments applied VE-822, an effective GC treatment, to assess cell migration and proliferation in gastric mucosa epithelial cells, and real-time PCR was used to measure alterations of autophagy-related gene expression.

Results

High ATG3, ATG4C, ATG5, and ATG10 mRNA levels were associated with good OS, while increased ATG4B, ATG7, ATG12, ATG16L1, and TECPR1 mRNA levels related to unfavorable OS in patients with GC. ATG12 overexpression had different effects on OS due to high levels of heterogeneity. High ATG12 expression was correlated with good OS in female patients with GC and with bad OS for male patients. Additionally, the increased ATG12 expression was more likely to get a satisfactory OS in patients who underwent surgery alone but was associated with poor OS for patients treated with 5-FU adjuvant. In addition, elevated TECPR1 expression was related to favorable OS for patients with poorly differentiated type, while for patients with moderate differentiation, it was relevant to poor OS. The in vitro experiments showed that berzosertib could significantly inhibit the migration and proliferation of human gastric mucosa epithelial cells, and further real-time PCR assessment of ATG expressions partially coincided with the bioinformation analysis above.

Conclusion

These results indicate that individual ATGs have unique prognostic significance interpreted using Kaplan–Meier plotter analysis and in vitro experiments, and this may help guide clinical therapeutic strategy and promote OS by individualizing therapy for GC patients.

The Role of Autophagy in Gastric Cancer Chemoresistance: Friend or Foe?

Gastric cancer is the third most common cause of cancer-related death worldwide. Drug resistance is the main inevitable and vital factor leading to a low 5-year survival rate for patients with gastric cancer. Autophagy, as a highly conserved homeostatic pathway, is mainly regulated by different proteins and non-coding RNAs (ncRNAs) and plays dual roles in drug resistance of gastric cancer. Thus, targeting key regulatory nodes in the process of autophagy by small molecule inhibitors or activators has become one of the most promising strategies for the treatment of gastric cancer in recent years. In this review, we provide a systematic summary focusing on the relationship between autophagy and chemotherapy resistance in gastric cancer. We comprehensively discuss the roles and molecular mechanisms of multiple proteins and the emerging ncRNAs including miRNAs and lncRNAs in the regulation of autophagy pathways and gastric cancer chemoresistance. We also summarize the regulatory effects of autophagy inhibitor and activators on gastric cancer chemoresistance. Understanding the vital roles of autophagy in gastric cancer chemoresistance will provide novel opportunities to develop promising therapeutic strategies for gastric cancer.

Circular RNA MCTP2 inhibits cisplatin resistance in gastric cancer by miR-99a-5p-mediated induction of MTMR3 expression

Background

Cisplatin (CDDP) is the first-line chemotherapy for gastric cancer (GC). The poor prognosis of GC patients is partially due to the development of CDDP resistance. Circular RNAs (circRNAs) are a subclass of noncoding RNAs that function as microRNA (miRNA) sponges. The role of circRNAs in CDDP resistance in GC has not been evaluated.

Methods

RNA sequencing was used to identify the differentially expressed circRNAs between CDDP-resistant and CDDP-sensitive GC cells. qRT-PCR was used to detect the expression of circMCTP2 in GC tissues. The effects of circMCTP2 on CDDP resistance were investigated in vitro and in vivo. Pull-down assays and luciferase reporter assays were performed to confirm the interactions among circMCTP2, miR-99a-5p, and myotubularin-related protein 3 (MTMR3). The protein expression levels of MTMR3 were detected by western blotting. Autophagy was evaluated by confocal microscopy and transmission electron microscopy (TEM).

Results

CircMCTP2 was downregulated in CDDP-resistant GC cells and tissues compared to CDDP-sensitive GC cells and tissues. A high level of circMCTP2 was found to be a favorable factor for the prognosis of patients with GC. CircMCTP2 inhibited proliferation while promoting apoptosis of CDDP-resistant GC cells in response to CDDP treatment. CircMCTP2 was also found to reduce autophagy in CDDP-resistant GC cells. MiR-99a-5p was verified to be sponged by circMCTP2. Inhibition of miR-99a-5p could sensitize GC cells to CDDP. MTMR3 was confirmed to be a direct target of miR-99a-5p. Knockdown of MTMR3 reversed the effects of circMCTP2 on the proliferation, apoptosis and autophagy of CDDP-resistant GC cells. CircMCTP2 was also confirmed to inhibit CDDP resistance in vivo in a nude mouse xenograft model.

Conclusions

CircMCTP2 sensitizes GC to CDDP through the upregulation of MTMR3 by sponging miR-99a-5p. Overexpression of CircMCTP2 could be a new therapeutic strategy for counteracting CDDP resistance in GC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-020-01758-w.

Circular RNA circ_0026359 Enhances Cisplatin Resistance in Gastric Cancer via Targeting miR-1200/POLD4 Pathway

Human gastric cancer is one of the most common malignant tumors with a poor prognosis. Cisplatin (CDDP) is a well-known first-line chemotherapeutic drug. Acquired resistance retards the clinical application of CDDP in gastric cancer. In this study, circular RNA circ_0026359 was demonstrated to be overexpressed in gastric cancer tissues/cells compared with normal gastric tissues/cells and was overexpressed in CDDP-resistant gastric cancer tissues/cells compared with CDDP-sensitive gastric cancer tissues/cells. High levels of circ_0026359 were associated with low overall survival (OS) and relapse-free survival (RFS) rates in gastric cancer patients. circ_0026359 was examined to promote CDDP resistance in gastric cancer cells. circ_0026359 directly interacted and negatively regulated miR-1200. POLD4 was a direct target of miR-1200. miR-1200/POLD4 pathway mediated the promoting role of circ_0026359 in CDDP resistance of gastric cancer. circ_0026359 could be used as a potential target for CDDP-resistant gastric cancer therapy.

Combined Systematic Review and Transcriptomic Analyses of Mammalian Aquaporin Classes 1 to 10 as Biomarkers and Prognostic Indicators in Diverse Cancers

Aquaporin (AQP) channels enable regulated transport of water and solutes essential for fluid homeostasis, but they are gaining attention as targets for anticancer therapies. Patterns of AQP expression and survival rates for patients were evaluated by systematic review (PubMed and Embase) and transcriptomic analyses of RNAseq data (Human Protein Atlas database). Meta-analyses confirmed predominantly negative associations between AQP protein and RNA expression levels and patient survival times, most notably for AQP1 in lung, breast and prostate cancers; AQP3 in esophageal, liver and breast cancers; and AQP9 in liver cancer. Patterns of AQP expression were clustered for groups of cancers and associated with risk of death. A quantitative transcriptomic analysis of AQP1-10 in human cancer biopsies similarly showed that increased transcript levels of AQPs 1, 3, 5 and 9 were most frequently associated with poor survival. Unexpectedly, increased AQP7 and AQP8 levels were associated with better survival times in glioma, ovarian and endometrial cancers, and increased AQP11 with better survival in colorectal and breast cancers. Although molecular mechanisms of aquaporins in pathology or protection remain to be fully defined, results here support the hypothesis that overexpression of selected classes of AQPs differentially augments cancer progression. Beyond fluid homeostasis, potential roles for AQPs in cancers (suggested from an expanding appreciation of their functions in normal tissues) include cell motility, membrane process extension, transport of signaling molecules, control of proliferation and apoptosis, increased mechanical compliance, and gas exchange. AQP expression also has been linked to differences in sensitivity to chemotherapy treatments, suggesting possible roles as biomarkers for personalized treatments. Development of AQP pharmacological modulators, administered in cancer-specific combinations, might inspire new interventions for controlling malignant carcinomas.

Hypoxia-Induced Aquaporin-3 Changes Hepatocellular Carcinoma Cell Sensitivity to Sorafenib by Activating the PI3K/Akt Signaling Pathway

Purpose

Hypoxia-induced changes are primarily activated in patients with hepatocellular carcinoma (HCC) and long-term sorafenib exposure, thereby reducing the sensitivity to the drug. Aquaporin-3 (AQP3), a member of the aquaporin family, is a hypoxia-induced substance that affects the chemosensitivity of non-hepatocellular tumors. However, its expression and role in the sensitivity of hypoxic HCC cells to sorafenib-induced apoptosis remain unclear. The purpose of this study was to detect changes in AQP3 expression in hypoxic HCC cells and to determine whether these changes alter the sensitivity of these cells to sorafenib.

Materials and Methods

Huh7 and HepG2 hypoxic cell models were established and AQP3 expression was detected using quantitative real-time polymerase chain reaction (qPCR) and Western blotting. Furthermore, the role of AQP3 in cell sensitivity to sorafenib was evaluated via flow cytometry, Western blotting, and a CCK-8 assay.

Results

The results of qPCR and Western blotting showed that AQP3 was overexpressed in the Huh7 and HepG2 hypoxic cell models. Furthermore, AQP3 protein levels were positively correlated with hypoxia-inducible factor-1α (HIF-1α) levels. Compared with cells transfected with lentivirus-GFP (Lv-GFP), hypoxic cells transfected with lentivirus-AQP3 (Lv-AQP3) were less sensitive to sorafenib-induced apoptosis. However, the sensitivity to the drug increased in cells transfected with lentivirus-AQP3RNAi (Lv-AQP3RNAi). Akt and Erk phosphorylation was enhanced in Lv-AQP3-transfected cells. Compared with UO126 (a Mek1/2 inhibitor), LY294002 (a PI3K inhibitor) attenuated the AQP3-induced insensitivity to sorafenib observed in hypoxic cells transfected with Lv-AQP3. Combined with LY294002-treated cells, hypoxic cells transfected with Lv-AQP3RNAi were more sensitive to sorafenib.

Conclusion

The study results show that AQP3 is a potential therapeutic target for improving the sensitivity of hypoxic HCC cells to sorafenib.

Targeting Autophagy Facilitates T Lymphocyte Migration by Inducing the Expression of CXCL10 in Gastric Cancer Cell Lines

Autophagy is a type of cellular catabolic degradation process that occurs in response to nutrient starvation or metabolic stress, and is a valuable resource for highly proliferating cancer cells. Autophagy also facilitates the resistance of cancer cells to antitumor therapies. However, the involvement of autophagy in regulating CXCL10 expression in gastric cancer (GC) cells and T lymphocyte migration remains unclear. In this study, we aimed to investigate the effect of autophagy inhibition on CXCL10 expression and T lymphocyte infiltration in GC and elucidate the underlying mechanism. Analysis of public databases revealed a positive correlation between CXCL10 expression and both prognosis of patients with GC and the expression profile of T lymphocyte markers in the GCs. Chemotaxis and spheroid infiltration assays revealed that CXCL10 induced T lymphocyte migration and infiltration into GC spheroids, an in vitro three-dimensional cell culture model. In addition, in vitro autophagy inhibition in GC cells increased CXCL10 expression under both normal and hypoxic culture conditions. Further investigation on the underlying mechanism showed that in vitro autophagy inhibition suppressed the JNK signaling pathway and further enhanced CXCL10 expression in GC cells. Collectively, our results provide novel insights for understanding the role of autophagy in regulation of intra-tumor immunity.

ERas Enhances Resistance to Cisplatin-Induced Apoptosis by Suppressing Autophagy in Gastric Cancer Cell

Gastric cancer (GC), a common type of malignant cancer, remains the fifth most frequently diagnosed cancer and the third leading cause of cancer-related deaths worldwide. Despite developments in the treatment of GC, the prognosis remains poor. Embryonic stem cell-expressed Ras (ERas), a novel member of the Ras protein family, has recently been identified as an oncogene involved in the tumorigenic growth of embryonic stem cells. A recent study reported that ERas is expressed in most GC cell lines and GC specimens, and it promotes tumorigenicity in GC through induction of the epithelial mesenchymal transition (EMT) and activation of the PI3K/AKT pathway. Here, we found that ERas blocked autophagy flux in BGC-823 and AGS GC cells, which may occur through activation of the AKT/mTOR signaling pathway. Moreover, ERas overexpression suppressed cisplatin-induced apoptosis, and rapamycin treatment significantly attenuated ERas-mediated cisplatin resistance in GC cells. These data suggest that ERas may be a potential therapeutic target to improve the outcomes of GC patients by regulating the autophagy process.

Propofol facilitates cisplatin sensitivity via lncRNA MALAT1/miR-30e/ATG5 axis through suppressing autophagy in gastric cancer

AIMS

Recently, chemoresistance has been recognized as an obstacle in the treatment of gastric cancer (GC). The aim of this study was to investigate the biological functions and underlying mechanisms of propofol in GC chemoresistance.

MAIN METHODS

CCK-8 assay, flow cytometry and immunofluorescent staining were performed to assess the IC₅₀ concentration, cell apoptosis and autophagy activity of cisplatin in both GC chemosensitive cells (SGC7901) and chemoresistant cells (SGC7901/CDDP). The expression pattern of MALAT1 in GC cells was detected by qRT-PCR. The shRNAs and overexpressing plasmids were employed for the loss or gain-of-function. Dual-luciferase reporter assay was subjected to verify the binding relationship between MALAT1 and miR-30e. Besides, ATG5 mRNA and protein levels were determined using qRT-PCR and western blot analysis. Furthermore, GC xenograft mice model was established to validate the in vitro findings.

KEY FINDINGS

Chemoresistant GC cells presented higher IC₅₀ of cisplatin, increased autophagy activity and stronger expression of MALAT1. The application of propofol promoted cell apoptosis and reduced the activity of autophagy through downregulating MALAT1. Silencing of MALAT1 inhibited chemo-induced autophagy, whereas MALAT1 overexpression promoted autophagy in GC cells. Mechanistic researches demonstrated that MALAT1 could bind with miR-30e to regulate ATG5 expression, thus causing the suppression of autophagy. In vivo GC xenograft model treated with both propofol and cisplatin also showed significantly decreased tumor size and weight, which was enhanced by knockdown of MALAT1.

SIGNIFICANCE

Altogether, our study revealed a novel mechanism of propofol of lncRNA MALAT1/miR-30e/ATG5 mediated autophagy-related chemoresistance in GC, casting new lights on the understanding of propofol.

Ubenimex induces autophagy inhibition and EMT suppression to overcome cisplatin resistance in GC cells by perturbing the CD13/EMP3/PI3K/AKT/NF-κB axis

Cisplatin (CDDP)-based chemotherapy is a standard treatment for gastric cancer (GC). However, chemoresistance is a major obstacle for CDDP application. Exploring underlying mechanisms of CDDP resistance development in GC and selecting an effective strategy to overcome CDDP resistance remain a challenge. Here, we demonstrate that a transmembrane ectoenzyme, CD13, endows GC patients with insensitivity to CDDP and predicts an undesirable prognosis in GC patients with CDDP treatment. Similarly, CD13 expression is positively related with CDDP resistance in GC cells. A CD13 inhibitor, Ubenimex, reverses CDDP resistance and renders GC cells sensitivity to CDDP, for which CD13 reduction is essential, and epithelial membrane protein 3 (EMP3) is a putative target downstream of CD13. Furthermore, Ubenimex decreases EMP3 expression by boosting its CpG island hypermethylation for which CD13 down-regulation is required. In addition, EMP3 is a presumptive modifier by which CD13 exerts functions in the phosphoinositol 3-kinase/protein kinase B (PI3K/AKT) pathway. Ubenimex inhibits the activation of the CD13/EMP3/PI3K/AKT/NF-κB pathway to overcome CDDP resistance in GC cells by suppressing autophagy and epithelial-mesenchymal transition (EMT). Therefore, CD13 is a potential indicator of CDDP resistance formation, and Ubenimex may serve as a potent candidate for reversing CDDP resistance in GC.

Molecular Mechanisms Underlying Autophagy-Mediated Treatment Resistance in Cancer

Despite advances in diagnostic tools and therapeutic options, treatment resistance remains a challenge for many cancer patients. Recent studies have found evidence that autophagy, a cellular pathway that delivers cytoplasmic components to lysosomes for degradation and recycling, contributes to treatment resistance in different cancer types. A role for autophagy in resistance to chemotherapies and targeted therapies has been described based largely on associations with various signaling pathways, including MAPK and PI3K/AKT signaling. However, our current understanding of the molecular mechanisms underlying the role of autophagy in facilitating treatment resistance remains limited. Here we provide a comprehensive summary of the evidence linking autophagy to major signaling pathways in the context of treatment resistance and tumor progression, and then highlight recently emerged molecular mechanisms underlying autophagy and the p62/KEAP1/NRF2 and FOXO3A/PUMA axes in chemoresistance.

Aquaporins Involvement in Pancreas Physiology and in Pancreatic Diseases

Aquaporins are a family of transmembrane proteins permeable to water. In mammals, they are subdivided into classical aquaporins that are permeable to water; aquaglyceroporins that are permeable to water, glycerol and urea; peroxiporins that facilitate the diffusion of H2O2 through cell membranes; and so called unorthodox aquaporins. Aquaporins ensure important physiological functions in both exocrine and endocrine pancreas. Indeed, they are involved in pancreatic fluid secretion and insulin secretion. Modification of aquaporin expression and/or subcellular localization may be involved in the pathogenesis of pancreatic insufficiencies, diabetes and pancreatic cancer. Aquaporins may represent useful drug targets for the treatment of pathophysiological conditions affecting pancreatic function, and/or diagnostic/predictive biomarker for pancreatic cancer. This review summarizes the current knowledge related to the involvement of aquaporins in the pancreas physiology and physiopathology.

Protective effects of zingerone on cisplatin-induced nephrotoxicity in female rats

Zingerone (ZO), one of the active components of ginger (Zingiber officinale), is a phenolic alkanone with antioxidant, antiapoptotic, and anti-inflammatory properties. Cisplatin (CP) is a widely used chemotherapeutic drug for solid tumors, but its therapeutic use is limited due to dose-dependent nephrotoxicity. In the present study, we investigated the ameliorative effect of ZO against CP-induced nephrotoxicity. Intraperitoneal administration of single-dose CP (7 mg/kg body weight) on the first day enhanced kidney lipid peroxidation and reduced antioxidant enzyme activities such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione (GSH). CP increased serum urea and creatinine levels and disrupted histological integrity while causing a decrease aquaporin 1 (AQP1) level in the kidney tissues. CP induced inflammatory responses by elevating the levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-33 (IL-33) and nuclear factor kappa B (NF-κB), and activities of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Moreover, it also caused oxidative DNA damage and activation of apoptotic pathway by increasing of 8-hydroxy-2'-deoxyguanosine (8-OHdG), p53, cysteine aspartate-specific protease-3 (caspase-3), and Bcl-2-associated x protein (bax) while decreasing B cell lymphoma-2 (Bcl-2). However, treatment with ZO at a dose of 25 and 50 mg/kg b.wt. for 7 days significantly decreased oxidative stress, apoptosis, inflammation, and histopathological alterations while increased AQP1 levels in the kidney tissue. The results of the current study suggested that ZO as an effective natural product attenuates CP-induced nephrotoxicity.

Adapting and Surviving: Intra and Extra-Cellular Remodeling in Drug-Resistant Gastric Cancer Cells

Despite the significant recent advances in clinical practice, gastric cancer (GC) represents a leading cause of cancer-related deaths in the world. In fact, occurrence of chemo-resistance still remains a daunting hindrance to effectiveness of the current approach to GC therapy. There is accumulating evidence that a plethora of cellular and molecular factors is implicated in drug-induced phenotypical switching of GC cells. Among them, epithelial-mesenchymal transition (EMT), autophagy, drug detoxification, DNA damage response and drug target alterations, have been reported as major determinants. Intriguingly, resistant GC phenotype may be the result of GC cell-induced tumor microenvironment (TME) remodeling, which is currently emerging as a key player in promoting drug resistance and overcoming cytotoxic effects of drugs. In this review, we discuss the possible mechanisms of drug resistance and their involvement in determining current GC therapies failure.

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.

Water transport proteins-aquaporins (AQPs) in cancer biology

As highly conserved ubiquitous proteins, aquaporins (AQPs) play an imperative role in the development and progression of cancer. By trafficking water and other small molecules, AQPs play a vital role in preserving the cellular environment. Due to their critical role in cell stability and integrity, it would make sense that AQPs are involved in cancer progression. When AQPs alter the cellular environment, there may be several downstream effects such as alterations in cellular osmolality, volume, ionic composition, and signaling pathways. Changes in the intracellular levels of certain molecules serving as second messengers are synchronized by AQPs. Thus AQPs regulate numerous downstream effector signaling molecules that promote cancer development and progression. In numerous cancer types, AQP expression has shown a correlation with tumor stage and prognosis. Furthermore, AQPs assist in angiogenic and oxidative stress related damaging processes critical for cancer progression. This indicates that AQP proteins may be a viable therapeutic target or biomarker of cancer prognosis.

DSGOST regulates resistance via activation of autophagy in gastric cancer

Danggui-Sayuk-Ga-Osuyu-Saenggang-Tang (DSGOST in Korean, Danggui-Sini-Jia-Wuzhuyu-Shengian-Tang in Chinese, and Tokishigyakukagoshuyushokyoto (TJ-38) in Japanese), a well-known traditional Korean/Chinese/Japanese medicine, has long been used to treat vascular diseases such as Raynaud’s phenomenon (RP). However, anticancer effect of DSGOST remains elusive. In this study, we checked if DSGOST has an anticancer effect against gastric cancer cells, and investigated the mechanisms underlying DSGOST resistance. Moreover, DSGOST regulates chemoresistance in cisplatin-treated gastric cancer cells. Interestingly, DSGOST treatment induced the accumulation of GFP-LC3 puncta and increased the level of autophagy markers, such as LC3-II, ATG5, and Beclin-1, indicating activated autophagy. Furthermore, DSGOST could activate epithelial-to-mesenchymal transition (EMT) and exosomes via induction of autophagy. DSGOST in combination with TGFβ also induced autophagy and EMT. However, autophagy inhibition induces DSGOST-mediated cell death in gastric cancer cells. In addition, autophagy inhibition blocks the activation of DSGOST-mediated EMT markers including N-cadherin, Snail, Slug, vimentin, β-catenin, p-Smad2, and p-Smad3. Taken together, these findings indicated that prosurvival autophagy was one of the mechanisms involved in the resistance of gastric cancer to DSGOST. Targeting the inhibition of autophagy could be an effective therapeutic approach to overcome resistance to DSGOST in gastric cancer.

Etk Interaction with PFKFB4 Modulates Chemoresistance of Small-cell Lung Cancer by Regulating Autophagy

Purpose: Epithelial and endothelial tyrosine kinase (Etk), also known as bone marrow X kinase (Bmx), was found to be critical in modulating the chemoresistance of small-cell lung cancer (SCLC) in our preliminary study. However, the molecular mechanisms of Etk in SCLC chemoresistance remain poorly understood.Experimental Design: We determined correlation of Etk with autophagy in SCLC. And direct inhibition of autophagy was performed to validate its effect on chemoresistance. Coimmunoprecipitation (co-IP) and GST-pull down experiments were conducted to verify the interaction of Etk and PFKFB4, after a microarray analysis. In vitro and in vivo gain or loss-of-function analyses and evaluation of PFKFB4 expression in SCLC specimens, were done to validate its role in chemoresistance. Ibrutinib was administrated in SCLC cells to verify its synergistic anti-tumor effect with chemotherapy using preclinical models including a PDX model.Results: Downregulation of Etk suppressed autophagy in chemoresistant SCLC cells, and direct inhibition of autophagy sensitized cells to chemotherapy. PFKFB4 (6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 4) was identified as a downstream target of Etk and an Etk-interacting protein, which promoted chemoresistance in SCLC and was associated with poor therapeutic response and prognosis. Furthermore, ibrutinib was found to exhibit a synergistic anti-tumor effect with chemotherapy in targeting Etk.Conclusions: Our results demonstrated for the first time that Etk interacts with PFKFB4 to promote SCLC chemoresistance through regulation of autophagy. Aberrant Etk and PFKFB4 can be predictive factors for the chemotherapy response as well as potential therapeutic targets in SCLC. Clin Cancer Res; 24(4); 950-62. ©2017 AACR.

Modulating lysosomal function through lysosome membrane permeabilization or autophagy suppression restores sensitivity to cisplatin in refractory non-small-cell lung cancer cells

Lung cancer is the leading cause of cancer-related deaths. Most patients develop resistance to platinum within several months of treatment. We investigated whether triggering lysosomal membrane permeabilization (LMP) or suppressing autophagy can restore cisplatin susceptibility in lung cancer with acquired chemoresistance. Cisplatin IC₅₀ in A549Pt (parental) and A549cisR (cisplatin resistant) cells was 13 μM and 47 μM, respectively. Following cisplatin exposure, A549cisR cells failed to elicit an apoptotic response. This was manifested by diminished Annexin–V staining, caspase 3 and 9, BAX and BAK activation in resistant but not in parental cells. Chloroquine preferentially promoted LMP in A549cisR cells, revealed by leakage of FITC-dextran into the cytosol as detected by immunofluorescence microscopy. This was confirmed by increased cytosolic cathepsin D signal on Immunoblot. Cell viability of cisplatin-treated A549cisR cells was decreased when co-treated with chloroquine, corresponding to a combination index below 0.8, suggesting synergism between the two drugs. Notably, chloroquine activated the mitochondrial cell death pathway as indicated by increase in caspase 9 activity. Interestingly, inhibition of lysosomal proteases using E64 conferred cytoprotection against cisplatin and chloroquine co-treatment, suggesting that chloroquine-induced cell death occurred in a cathepsin-mediated mechanism. Likewise, blockage of caspases partially rescued A549cisR cells against the cytotoxicity of cisplatin and chloroquine combination. Cisplatin promoted a dose-dependent autophagic flux induction preferentially in A549cisR cells, as evidenced by a surge in LC3-II/α-tubulin following pre-treatment with E64 and increase in p62 degradation. Compared to untreated cells, cisplatin induced an increase in cyto-ID-loaded autophagosomes in A549cisR cells that was further amplified by chloroquine, pointing toward autophagic flux activation by cisplatin. Interestingly, this effect was less pronounced in A549Pt cells. Blocking autophagy by ATG5 depletion using siRNA markedly enhances susceptibility to cisplatin in A549cisR cells. Taken together, our results underscore the utility of targeting lysosomal function in overcoming acquired cisplatin refractoriness in lung cancer.