Involvement of Actin in Autophagy and Autophagy-Dependent Multidrug Resistance in Cancer

Construction of a prognostic model for autophagy in Wilm's tumor

BACKGROUND

Wilm's tumor (WT) is one of the most common childhood urological tumors, ranking second in the incidence of pediatric abdominal tumors. The development of WT is associated with various factors, and the correlation with autophagy is currently unclear.

PURPOSE

To develop a new prognostic model of autophagy-related genes (ATG) for WT.

METHODS

Using the Therapeutically applicable research to generate effective treatments (TARGET) database to screen for differentially expressed ATGs in WT and normal tissues. ATGs were screened for prognostic relevance to WT using one-way and multifactorial Cox regression analyses and prognostic models were constructed. The risk score was calculated according to the model, and the predictive ability of the constructed model was analyzed using the ROC (receiver operating characteristic) curve to verify the significance of the model for the prognosis of WT.

RESULTS

Sixty-eight differentially expressed ATGs were identified by univariate Cox regression analysis, and two critical prognostic ATGs (CXCR4 and ERBB2) were identified by multivariate Cox regression analysis. Patients were divided into high-risk and low-risk groups according to the differential expression of these two ATGs. Kaplan-Meier (KM) curves showed a significant difference in survival time between the two groups. The critical prognostic ATGs were combined with race, age, and stage in a multifactorial regression analysis, and the final prognostic model was produced as a line graph.

CONCLUSION

The prognostic model of autophagy-related genes composed of the CXCR4 gene and ERBB2 gene has a specific predictive value for the prognosis of WT, and the present study provides a clear basis for future research on biomarkers and therapeutic targets.

Gelsolin inhibits autophagy by regulating actin depolymerization in pancreatic ductal epithelial cells in acute pancreatitis

Gelsolin (GSN) can sever actin filaments associated with autophagy. This study investigated how GSN-regulated actin filaments control autophagy in pancreatic ductal epithelial cells (PDECs) in acute pancreatitis (AP). AP was produced in a rat model and PDECs using caerulein (CAE). Rat pancreatic duct tissue and HPDE6-C7 cells were extracted at 6, 12, 24, and 48 h after CAE treatment. HPDE6-C7 cells in the presence of CAE were treated with cytochalasin B (CB) or silenced for GSN for 24 h. Pancreatic histopathology and serum amylase levels were analyzed. Cellular ultrastructure and autophagy in PDECs were observed by transmission electron microscopy after 24 h of CAE treatment. The expression of GSN and autophagy markers LC3, P62, and LAMP2 was evaluated in PDECs by immunohistochemistry and western blotting. Actin filaments were observed microscopically. Amylase levels were highest at 6 h of AP, and pancreatic tissue damage increased over time. Mitochondrial vacuolization and autophagy were observed in PDECs. CAE increased GSN expression in these cells over time, increased the LC3-II/LC3-I ratio and LAMP2 expression at 24 and 6 h of treatment, respectively, and decreased P62 expression at all time points. CB treatment for 24 h decreased the LC3-II/LC3-I ratio and LAMP2 expression, increased P62 levels, but had no impact on GSN expression in CAE-treated PDECs. CAE induced actin depolymerization, and CB potentiated this effect. GSN silencing increased the LC3-II/LC3-I ratio and LAMP2 expression and reduced actin depolymerization in CAE-treated PDECs. GSN may inhibit autophagosome biogenesis and autophagosome-lysosome fusion by increasing actin depolymerization in PDECs in AP.

Pointed-end processive elongation of actin filaments by Vibrio effectors VopF and VopL

According to the cellular actin dynamics paradigm, filaments grow at their barbed ends and depolymerize predominantly from their pointed ends to form polar structures and do productive work. We show that actin can elongate at the pointed end when assisted by Vibrio VopF/L toxins, which act as processive polymerases. In cells, processively moving VopF/L speckles are inhibited by factors blocking the pointed but not barbed ends. Multispectral single-molecule imaging confirmed that VopF molecules associate with the pointed end, actively promoting its elongation even in the presence of profilin. Consequently, VopF/L can break the actin cytoskeleton's polarity by compromising actin-based cellular processes. Therefore, actin filament design allows processive growth at both ends, which suggests unforeseen possibilities for cellular actin organization, particularly in specialized cells and compartments.

Extracellular Vesicles and Resistance to Anticancer Drugs: A Tumor Skeleton Key for Unhinging Chemotherapies

Although surgical procedures and clinical care allow reaching high success in fighting most tumors, cancer is still a formidable foe. Recurrence and metastatization dampen the patients’ overall survival after the first diagnosis; nevertheless, the large knowledge of the molecular bases drives these aspects. Chemoresistance is tightly linked to these features and is mainly responsible for the failure of cancer eradication, leaving patients without a crucial medical strategy. Many pathways have been elucidated to trigger insensitiveness to drugs, generally associated with the promotion of tumor growth, aggressiveness, and metastatisation. The main mechanisms reported are the expression of transporter proteins, the induction or mutations of oncogenes and transcription factors, the alteration in genomic or mitochondrial DNA, the triggering of autophagy or epithelial-to-mesenchymal transition, the acquisition of a stem phenotype, and the activation of tumor microenvironment cells. Extracellular vesicles (EVs) can directly transfer or epigenetically induce to a target cell the molecular machinery responsible for the acquisition of resistance to drugs. In this review, we resume the main body of knowledge supporting the crucial role of EVs in the context of chemoresistance, with a particular emphasis on the mechanisms related to some of the main drugs used to fight cancer.

The Amyotrophic Lateral Sclerosis M114T PFN1 Mutation Deregulates Alternative Autophagy Pathways and Mitochondrial Homeostasis

Mutations in profilin 1 (PFN1) have been identified in rare familial cases of Amyotrophic Lateral Sclerosis (ALS). PFN1 is involved in multiple pathways that could intervene in ALS pathology. However, the specific pathogenic role of PFN1 mutations in ALS is still not fully understood. We hypothesized that PFN1 could play a role in regulating autophagy pathways and that PFN1 mutations could disrupt this function. We used patient cells (lymphoblasts) or tissue (post-mortem) carrying PFN1 mutations (M114T and E117G), and designed experimental models expressing wild-type or mutant PFN1 (cell lines and novel PFN1 mice established by lentiviral transgenesis) to study the effects of PFN1 mutations on autophagic pathway markers. We observed no accumulation of PFN1 in the spinal cord of one E117G mutation carrier. Moreover, in patient lymphoblasts and transfected cell lines, the M114T mutant PFN1 protein was unstable and deregulated the RAB9-mediated alternative autophagy pathway involved in the clearance of damaged mitochondria. In vivo, motor neurons expressing M114T mutant PFN1 showed mitochondrial abnormalities. Our results demonstrate that the M114T PFN1 mutation is more deleterious than the E117G variant in patient cells and experimental models and suggest a role for the RAB9-dependent autophagic pathway in ALS.

Autophagy based cellular physiological strategies target oncogenic progression

Evidence accumulated from past findings indicates that defective proteostasis may contribute to risk factors for cancer generation. Irregular assembly of abnormal proteins catalyzes the disturbance of cellular proteostasis and induces the ability of abnormal cellular proliferation. The autophagy mechanism plays a key role in the regular clearance of abnormal/poor lipids, proteins, and various cellular organelles. The results of functional and effective autophagy deliver normal cellular homeostasis, which establishes supportive metabolism and avoids unexpected tumorigenesis events. Still, the precise molecular mechanism of autophagy in tumor suppression has not been clear. How autophagy triggers selective or nonselective bulk degradation to dissipate tumor promotion under stress conditions is not clear. Under proteotoxic insults to knockdown the drive of tumorigenesis, it is critical for us to figure out the detailed molecular functions of autophagy in human cancers. The current article summarizes autophagy-based theragnostic strategies targeting various phases of tumorigenesis and suggests the preventive roles of autophagy against tumor progression. A better understanding of various molecular partners of autophagic flux will improve and innovate therapeutic approaches based on autophagic-susceptible effects against cellular oncogenic transformation.

The Role of TRPM2 in Endothelial Function and Dysfunction

The transient receptor potential (TRP) melastatin-like subfamily member 2 (TRPM2) is a non-selective calcium-permeable cation channel. It is expressed by many mammalian tissues, including bone marrow, spleen, lungs, heart, liver, neutrophils, and endothelial cells. The best-known mechanism of TRPM2 activation is related to the binding of ADP-ribose to the nudix-box sequence motif (NUDT9-H) in the C-terminal domain of the channel. In cells, the production of ADP-ribose is a result of increased oxidative stress. In the context of endothelial function, TRPM2-dependent calcium influx seems to be particularly interesting as it participates in the regulation of barrier function, cell death, cell migration, and angiogenesis. Any impairments of these functions may result in endothelial dysfunction observed in such conditions as atherosclerosis or hypertension. Thus, TRPM2 seems to be an attractive therapeutic target for the conditions connected with the increased production of reactive oxygen species. However, before the application of TRPM2 inhibitors will be possible, some issues need to be resolved. The main issues are the lack of specificity, poor membrane permeabilization, and low stability in in vivo conditions. The article aims to summarize the latest findings on a role of TRPM2 in endothelial cells. We also show some future perspectives for the application of TRPM2 inhibitors in cardiovascular system diseases.

FV-429 induces autophagy blockage and lysosome-dependent cell death of T-cell malignancies via lysosomal dysregulation

It is widely accepted that lysosomes are essential for cell homeostasis, and autophagy plays an important role in tumor development. Here, we found FV-429, a synthetic flavonoid compound, inhibited autophagy flux, promoted autophagosomes accumulation, and inhibited lysosomal degradation in T-cell malignancies. These effects were likely to be achieved by lysosomal dysregulation. The destructive effects of FV-429 on lysosomes resulted in blockage of lysosome-associated membrane fusion, lysosomal membrane permeabilization (LMP), and cathepsin-mediated caspase-independent cell death (CICD). Moreover, we initially investigated the effects of autophagy inhibition by FV-429 on the therapeutic efficacy of chemotherapy and found that FV-429 sensitized cancer cells to chemotherapy agents. Our findings suggest that FV-429 could be a potential novel autophagy inhibitor with notable antitumor efficacy as a single agent.

Traditional Uyghur medicine Quercus infectoria galls water extract triggers apoptosis and autophagic cell death in colorectal cancer cells

Background

The water extract of Quercuse infectoria galls (QIG) is the active ingredient of Uyghur medicine Xipayi Kui Jie’an (KJA) which has promising therapeutic effects on Ulcerative Colitis (UC) as an alternative medicine. Considering the relationship between UC and the development of colorectal cancer (CRC), the present work aims to explore the direct anti-CRC activity of QIG extract.

Methods

CCK8 assay and flow cytometry were used to detect cytotoxicity and apoptosis. Transmission electron microscopy (TEM), flow cytometry, laser confocal and western blotting were performed to examine autophagy. We also adopted Reactive Oxygen Assay kit, as well as transwell and wound healing tests to study the underlying mechanism of QIG against CRC cells.

Results

First, we found that QIG extract could suppress the viability of CRC cells and trigger caspases-dependent apoptosis. Subsequently, we proved for the first time that QIG extract also triggered autophagic cell death in CRC cells, which together with apoptosis contributed to the cytotoxic effect on CRC cells. Further investigation revealed that QIG-induced cytotoxicity associated with intracellular ROS accumulation which could suppress the AKT/mTOR signaling pathway, and then induce autophagy and inhibit cell growth. Besides, Erk signaling pathway was also involved in the process of autophagic cell death. Moreover, QIG extract also influenced EMT process and inhibited CRC cell migration.

Conclusion

Altogether, this study provides a basis for the utilization of QIG as an alternative medicine for CRC prevention and treatment.

The Synthetic Flavonoid Derivative GL-V9 Induces Apoptosis and Autophagy in Cutaneous Squamous Cell Carcinoma via Suppressing AKT-Regulated HK2 and mTOR Signals

Cutaneous squamous-cell carcinoma (cSCC) is one of most common type of non-black skin cancer. The malignancy degree and the death risk of cSCC patients are significantly higher than basal cell carcinoma patients. GL-V9 is a synthesized flavonoid derived from natural active ingredient wogonin and shows potent growth inhibitory effects in liver and breast cancer cells. In this study, we investigated the anti-cSCC effect and the underlying mechanism of GL-V9. The results showed that GL-V9 induced both apoptosis and autophagy in human cSCC cell line A431 cells, and prevented the growth progression of chemical induced primary skin cancer in mice. Metabolomics assay showed that GL-V9 potentially affected mitochondrial function, inhibiting glucose metabolism and Warburg effect. Further mechanism studies demonstrated that AKT played important roles in the anti-cSCC effect of GL-V9. On one hand, GL-V9 suppressed AKT-modulated mitochondrial localization of HK2 and promoted the protein degradation of HK2, resulting in cell apoptosis and glycolytic inhibition. On the other hand, GL-V9 induced autophagy via inhibiting Akt/mTOR pathway. Interestingly, though the autophagy induced by GL-V9 potentially antagonized its effect of apoptosis induction, the anti-cSCC effect of GL-V9 was not diluted. All above, our studies suggest that GL-V9 is a potent candidate for cSCC treatment.

Autophagy: New Insights into Its Roles in Cancer Progression and Drug Resistance

Autophagy is a mechanism of lysosomal proteolysis that is utilized to degrade damaged organelles, proteins, and other cellular components. Although key studies demonstrate that autophagy functions as a mechanism of tumor suppression via the degradation of defective pre-malignant cells, autophagy can also be used as a mechanism to break down cellular components under stress conditions to generate the required metabolic materials for cell survival. Autophagy has emerged as an important mediator of resistance to radiation, chemotherapy, and targeted agents. This series of articles highlight the role of autophagy in cancer progression and drug resistance and underscores the need for new and more effective agents that target this process.

Development and validation of a survival model for thyroid carcinoma based on autophagy-associated genes

Abnormalities in autophagy-related genes (ARGs) are closely related to the occurrence and development of thyroid carcinoma (THCA). However, the effect of ARGs on the prognosis of THCA remains unclear. Here, by analyzing data from TCGA, 26 differentially expressed ARGs were screened. Cox regression and Lasso regression were utilized to analyze the prognosis of the training group, and a risk model was constructed. Our results show that low-risk patients had better overall survival (OS) than high-risk patients, and the area under the ROC curve in the training and testing groups was significant (3-year AUC, 0.735 vs 0.796; 5-year AUC, 0.821 vs 0.804). In addition, a comprehensive analysis of the 5 identified ARGs demonstrated that most of them were related to OS in THCA patients, and two of them (CX3CL1 and CDKN2A) were differentially expressed in THCA and normal thyroid tissues at the protein level. GSEA suggested that the inactivation of the cell defense system and the activation of some classical tumor signaling pathways are important driving forces for the progression of THCA. This study demonstrated that the 5 ARGs in the survival model are promising multidimensional biomarkers for the diagnosis, prognosis, and treatment of THCA.

[Inhibitory effect of ketogenic diet on neuroblastoma in BALB/c-nu mouse models]

OBJECTIVE

To investigate the inhibitory effect of ketogenic diet (KD) on growth of neuroblastoma in mice.

METHODS

BALB/c-nu mouse models bearing neuroblastoma xenografts were established by subcutaneous injection of human neuroblastoma cell line (SH-SY5Y). When the tumor volume reached 250 mm3, the mice were randomized into SD group with standard diet and PBS treatment, KD group with ketogenic diet and PBS treatment, and CP+KD group with ketogenic diet and cyclophosphamide (60 mg·kg^-1·day^-1) treatment, n=8. The tumor volume, body weight, blood glucose, ketone body (β-Hydroxybutyrate) levels, and hepatic steatosis in the mice were assessed. The expressions of caspase-3 and caspase-8 were detected by Western blotting, and Ki67 expresison was detected using immunohistochemistry (IHC). Transmission electron microscopy (TEM) was employed for the autophagosomes, and the autophagic protein Beclin1, LC3A/B and P62 were detected by IHC and Western blotting.

RESULTS

On day 28 post tumor cell injection, the mice in KD and CP+KD groups could prolong the overall survival rates than that in SD group (P < 0.001). On day 22 post the injection, the tumor volume in KD group was smaller than that in SD group (P < 0.05); on 16, 19, and 22 day post the injection, the tumor volume in CP+KD group was smaller than that in SD group (P < 0.01). The mice in SD group showed greater body weight on day 19 and higher blood glucose level on day 13 post the injection than those in the other two groups (P < 0.05). Blood ketone level and hepatic steatosis score were higher and glucose ketone index (GKI) was lower in KD and CP+KD groups than those in SD group (all P < 0.05). The expressions of Ki67 and apoptotic proteins were detected in the tumor tissues of all groups. TEM revealed more autophagosomes in the tumor tissues of KD group than that of SD group. P62 expression was lowered (P < 0.01) and Beclin1 and LC3A/B expressions were up-regulated in the tumor tissues of KD group (P < 0.05), which is consisitent with IHC.

CONCLUSIONS

KD has a strong anti-tumor effect in the xenograft mouse model possibly by regulating cell autophagy.

[Inhibitory effect of ketogenic diet on neuroblastoma in BALB/c-nu mouse models]

OBJECTIVE

To investigate the inhibitory effect of ketogenic diet (KD) on growth of neuroblastoma in mice.

METHODS

BALB/c-nu mouse models bearing neuroblastoma xenografts were established by subcutaneous injection of human neuroblastoma cell line (SH-SY5Y). When the tumor volume reached 250 mm3, the mice were randomized into SD group with standard diet and PBS treatment, KD group with ketogenic diet and PBS treatment, and CP+KD group with ketogenic diet and cyclophosphamide (60 mg·kg^-1·day^-1) treatment, n=8. The tumor volume, body weight, blood glucose, ketone body (β-Hydroxybutyrate) levels, and hepatic steatosis in the mice were assessed. The expressions of caspase-3 and caspase-8 were detected by Western blotting, and Ki67 expresison was detected using immunohistochemistry (IHC). Transmission electron microscopy (TEM) was employed for the autophagosomes, and the autophagic protein Beclin1, LC3A/B and P62 were detected by IHC and Western blotting.

RESULTS

On day 28 post tumor cell injection, the mice in KD and CP+KD groups could prolong the overall survival rates than that in SD group (P < 0.001). On day 22 post the injection, the tumor volume in KD group was smaller than that in SD group (P < 0.05); on 16, 19, and 22 day post the injection, the tumor volume in CP+KD group was smaller than that in SD group (P < 0.01). The mice in SD group showed greater body weight on day 19 and higher blood glucose level on day 13 post the injection than those in the other two groups (P < 0.05). Blood ketone level and hepatic steatosis score were higher and glucose ketone index (GKI) was lower in KD and CP+KD groups than those in SD group (all P < 0.05). The expressions of Ki67 and apoptotic proteins were detected in the tumor tissues of all groups. TEM revealed more autophagosomes in the tumor tissues of KD group than that of SD group. P62 expression was lowered (P < 0.01) and Beclin1 and LC3A/B expressions were up-regulated in the tumor tissues of KD group (P < 0.05), which is consisitent with IHC.

CONCLUSIONS

KD has a strong anti-tumor effect in the xenograft mouse model possibly by regulating cell autophagy.