Autophagy proteins regulate cell engulfment mechanisms that participate in cancer

Perfluorooctane sulfonate (PFOS) and its selected analogs induce various cell death types in peripheral blood mononuclear cells

The perfluoalkyl substance (PFASs) perfluorooctane sulfonate (PFOS) has been widely used in industry. However, PFOS is a persistent organic pollutant and has been gradually replaced by its short-chain analogs, perfluorohexane sulfonate (PFHxS) and perfluorobutane sulfonate (PFBS). PFASs are extremely persistent and are very frequently detected among the general population. The aim of the study was to determine the effect of selected PFASs on peripheral blood mononuclear cells (PBMCs) and the mechanisms of their action. PBMCs were exposed to PFOS, PFBS and PFHxS at concentrations ranging from 0.02 to 400 μM for 24 h, they were then tested for viability, apoptosis (changes in cytosolic calcium ions level and caspase-3, -8 and -9 activation), ferroptosis (changes in chelatable iron ions level and lipid peroxidation), and autophagy (LC3-II and Raptor level assay). PFOS exposure decreased cell viability, increased calcium ion level and caspase-8 activation; it also enhanced lipid peroxidation and increased the intracellular pool of chelatable iron ions as well as LC3-II protein content. In contrast, short-chain PFBS and PFHxS induced significant changes in the markers of apoptosis but had no substantial impact on ferroptosis or autophagy markers over a wide range of concentrations. Our results indicate that only PFOS demonstrated pro-ferroptotic and pro-autophagic potential but observed changes occurred at relatively high exposure. A short-chain substitute (PFBS) exhibited strong pro-apoptotic potential at concentrations related to occupational exposure. While the short-chain PFASs strongly affected the mitochondrial pathway of apoptosis, apoptosis itself was only induced by PFBS via the intrinsic and extrinsic pathways. It seems that the length of the carbon chain in PFASs appears to determine the cell death mechanisms activated in human PBMCs following exposure. Our findings provide a new insight into the immune toxicity mechanism induced by these compounds.

Cell death classification: A new insight based on molecular mechanisms

Cells tend to disintegrate themselves or are forced to undergo such destructive processes in critical circumstances. This complex cellular function necessitates various mechanisms and molecular pathways in order to be executed. The very nature of cell death is essentially important and vital for maintaining homeostasis, thus any type of disturbing occurrence might lead to different sorts of diseases and dysfunctions. Cell death has various modalities and yet, every now and then, a new type of this elegant procedure gets to be discovered. The diversity of cell death compels the need for a universal organizing system in order to facilitate further studies, therapeutic strategies and the invention of new methods of research. Considering all that, we attempted to review most of the known cell death mechanisms and sort them all into one arranging system that operates under a simple but subtle decision-making (If \ Else) order as a sorting algorithm, in which it decides to place and sort an input data (a type of cell death) into its proper set, then a subset and finally a group of cell death. By proposing this algorithm, the authors hope it may solve the problems regarding newer and/or undiscovered types of cell death and facilitate research and therapeutic applications of cell death.

Modulation of the immunity and inflammation by autophagy

Autophagy, a highly conserved cellular self-degradation pathway, has emerged with novel roles in the realms of immunity and inflammation. Genome-wide association studies have unveiled a correlation between genetic variations in autophagy-related genes and heightened susceptibility to autoimmune and inflammatory diseases. Subsequently, substantial progress has been made in unraveling the intricate involvement of autophagy in immunity and inflammation through functional studies. The autophagy pathway plays a crucial role in both innate and adaptive immunity, encompassing various key functions such as pathogen clearance, antigen processing and presentation, cytokine production, and lymphocyte differentiation and survival. Recent research has identified novel approaches in which the autophagy pathway and its associated proteins modulate the immune response, including noncanonical autophagy. This review provides an overview of the latest advancements in understanding the regulation of immunity and inflammation through autophagy. It summarizes the genetic associations between variants in autophagy-related genes and a range of autoimmune and inflammatory diseases, while also examining studies utilizing transgenic animal models to uncover the in vivo functions of autophagy. Furthermore, the review delves into the mechanisms by which autophagy dysregulation contributes to the development of three common autoimmune and inflammatory diseases and highlights the potential for autophagy-targeted therapies.

JI017 Induces Cell Autophagy and Apoptosis via Elevated Levels of Reactive Oxygen Species in Human Lung Cancer Cells

Lung cancer is one of the most common malignant tumors and a leading cause of cancer-related death in the worldwide. Various anticancer drugs, such as cisplatin and pemetrexed, have been developed for lung cancer treatment but due their drug resistance and side effects, novel treatments need to be developed. In this study, the efficacy of the natural drug JI017, which is known to have few side effects, was tested in lung cancer cells. JI017 inhibited A549, H460, and H1299 cell proliferation. JI017 induced apoptosis, regulated apoptotic molecules, and inhibited colony formation. Additionally, JI017 increased intracellular ROS generation. JI017 downregulated PI3K, AKT, and mTOR expression. JI017 increased the cytosolic accumulation of LC3. We found that JI017 promoted apoptosis through ROS-induced autophagy. Additionally, the xenograft tumor size was smaller in JI017-treated mice. We found that JI017 treatment increased MDA concentrations, decreased Ki-67 protein levels, and increased cleaved caspase-3 and LC3 levels in vivo. JI017 decreased cell proliferation and increased apoptosis by inducing autophagy signaling in H460 and H1299 lung cancer cells. Targeting JI017 and autophagy signaling could be useful in lung cancer treatment.

Autophagy in the retinal pigment epithelium: a new vision and future challenges

The retinal pigment epithelium (RPE) is a highly specialized monolayer of polarized, pigmented epithelial cells that resides between the vessels of the choriocapillaris and the neural retina. The RPE is essential for the maintenance and survival of overlying light-sensitive photoreceptors, as it participates in the formation of the outer blood-retinal barrier, phagocytosis, degradation of photoreceptor outer segment (POS) tips, maintenance of the retinoid cycle, and protection against light and oxidative stress. Autophagy is an evolutionarily conserved 'self-eating' process, designed to maintain cellular homeostasis. The daily autophagy demands in the RPE require precise gene regulation for the digestion and recycling of intracellular and POS components in lysosomes in response to light and stress conditions. In this review, we discuss selective autophagy and focus on the recent advances in our understanding of the mechanism of cell clearance in the RPE for visual function. Understanding how this catabolic process is regulated by both transcriptional and post-transcriptional mechanisms in the RPE will promote the recognition of pathological pathways in genetic disease and shed light on potential therapeutic strategies to treat visual impairments in patients with retinal disorders associated with lysosomal dysfunction.

Pitfalls in methods to study colocalization of nanoparticles in mouse macrophage lysosomes

Background

In the field of nanoscience there is an increasing interest to follow dynamics of nanoparticles (NP) in cells with an emphasis on endo-lysosomal pathways and long-term NP fate. During our research on this topic, we encountered several pitfalls, which can bias the experimental outcome. We address some of these pitfalls and suggest possible solutions. The accuracy of fluorescence microscopy methods has an important role in obtaining insights into NP interactions with lysosomes at the single cell level including quantification of NP uptake in a specific cell type.

Methods

Here we use J774A.1 cells as a model for professional phagocytes. We expose them to fluorescently-labelled amorphous silica NP with different sizes and quantify the colocalization of fluorescently-labelled NP with lysosomes over time. We focus on confocal laser scanning microscopy (CLSM) to obtain 3D spatial information and follow live cell imaging to study NP colocalization with lysosomes.

Results

We evaluate different experimental parameters that can bias the colocalization coefficients (i.e., Pearson’s and Manders’), such as the interference of phenol red in the cell culture medium with the fluorescence intensity and image post-processing (effect of spatial resolution, optical slice thickness, pixel saturation and bit depth). Additionally, we determine the correlation coefficients for NP entering the lysosomes under four different experimental set-ups. First, we found out that not only Pearson’s, but also Manders’ correlation coefficient should be considered in lysosome-NP colocalization studies; second, there is a difference in NP colocalization when using NP of different sizes and fluorescence dyes and last, the correlation coefficients might change depending on live-cell and fixed-cell imaging set-up.

Conclusions

The results summarize detailed steps and recommendations for the experimental design, staining, sample preparation and imaging to improve the reproducibility of colocalization studies between the NP and lysosomes.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01670-9.

Hernandezine induces autophagic cell death in human pancreatic cancer cells via activation of the ROS/AMPK signaling pathway

Hernandezine (Her) is a bisbenzylisoquinoline alkaloid extracted from the traditional Chinese herbal medicine Thalictrum glandulosissimum. Evidence shows that Her is a natural agonist of adenosine monophosphate (AMP)-activated protein kinase (AMPK) and induces apoptosis and autophagy in tumor cells. In this study, we investigated the role of autophagy in Her-induced cell death in human pancreatic cancer cell lines. We showed that Her dose-dependently suppressed cell proliferation, promoted autophagy and induced autophagic death in pancreatic ductal adenocarcinoma (PDAC) cell lines Capan-1 and SW1990. The IC50 values of Her in inhibition of Capan-1 and SW1990 cells were 47.7 μM and 40.1 μM, respectively. Immunoblotting showed that Her (1−40 μM) promoted the conversion of LC3-I to LC3-II, and Her exerted concentration-dependent and time-dependent effects on autophagy activation in PDAC cells. In transmission electron microscopy and fluorescence image analysis, we found that autophagic vacuoles were significantly increased in Her-treated cells. Knockdown of ATG5, a key gene in the autophagy pathway, alleviated the activation of autophagy by Her. These results demonstrated that Her induced autophagy in PDAC cells. Intensely activated autophagy could promote cell death. The autophagy inhibitors, BafA1 and HCQ significantly inhibited Her-induced cell death, implying that Her induced autophagic cell death in PDAC cells. Moreover, we showed that Her activated autophagy by increasing the phosphorylation of AMPK and decreasing the phosphorylation of mTOR/p70S6K. Knockdown of AMPKα relieves the autophagic cell death induced by Her. Furthermore, Her concentration-dependently enhanced reactive oxygen species (ROS) generation in PDAC cells. Antioxidants could reduce the phosphorylation of AMPK and suppress autophagic cell death induced by Her. Our study provides evidence for the development of Her as a therapeutic agent for the treatment of pancreatic cancer.

Correlation of AIF-1 Expression with Immune and Clinical Features in 1270 Glioma Samples

AIF-1 gene is surrounded by the genes involved in the inflammatory response and located in the major histocompatibility complex (MHC) class III genomic region. It has been found that microglial cells expressed the AIF-1 gene during all stages of mice brain development. However, the role of AIF-1 remains unclear in glioma. A total of 1270 glioma patients from three independent data sets were enrolled in the study. TIMER platform was used for comprehensive molecular characterization of tumor immune infiltrates. Sangerbox was used to analyze AIF-1 RNA sequencing expression data of tumors and normal samples, and to evaluate the association between AIF-1 expression and 29 sub-populations of immune cells. The R language 3.63 was used to identify differentially expressed genes for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. Kaplan-Meier survival analysis and univariate/multivariate Cox analysis were used to examine survival distributions. We found that AIF-1 gene was prominently up-regulated, especially in brain glioma including LGG and GBM. A strong correlation was observed between AIF-1 expression and the majority of immune cells, particularly in macrophage, myeloid-derived suppressor cells. Moreover, AIF-1 expression was correlated with immune infiltration level. We found that AIF-1 expression was strongly correlated with the specific immune and prognostic cell markers of monocytes, microglia and macrophages, M1 macrophages, and M2 macrophages after normalization through tumor purity in TCGA-LGG and TCGA-GBM. Higher expression level of AIF-1 was found to be significantly correlated with poor prognosis. GO analysis and KEGG pathways indicated that AIF-1 could affect glioma-related immune activities. Our study suggests that AIF-1 can be treated as a prognostic biomarker for glioma patients. AIF-1 was involved in pro-tumor processes and the regulation of immune status and correlates with poor prognosis.

Hypoxia enhances basal autophagy of epithelial-derived ameloblastoma cells

Ameloblastoma is a locally aggressive odontogenic tumor. Etiopathogenesis and locally aggressive growth properties of ameloblastoma can be attributed to a hypoxic microenvironment conducive to tumor cell survival. Epithelial-derived follicular ameloblastoma cells (EP-AMCs) display enhanced basal autophagy, but the interplay of hypoxia and autophagy in EP-AMCs survival and ameloblastoma recurrence is unclear. We evaluated differential expression of autophagic markers in primary and recurrent ameloblastomas and hypothesized that hypoxia-induced autophagy supports EP-AMC survival. Primary and recurrent ameloblastomas were comparatively assessed for expression levels of pan-cytokeratin, Vimentin, and autophagic markers SQSTM1/p62, LC3, and pS6. EP-AMCs compared with human odontoma-derived cells (HODCs) were subjected to severe hypoxia to determine the interplay of hypoxia and autophagic process in posthypoxia survival. Pan-cytokeratin and SQSTM1/p62 were expressed by both primary and recurrent ameloblastoma epithelial cells while the ameloblastoma connective tissues displayed weak reactivity to vimentin. Under hypoxia, EP-AMC expression levels of hypoxia-inducible factor (HIF)-1α, p62, and LC3 were increased while pS6 was decreased posthypoxia. The combined decrease in pS6 and enhanced LC3 in EP-AMCs under hypoxia indicate that EP-AMCs re-establish basal autophagy under hypoxia. Taken together, these suggest a possible role of LC3-associated phagocytosis (LAP) in ameloblastoma cell survival.

Prognostic Value of a Stemness Index-Associated Signature in Primary Lower-Grade Glioma

Objective

As a prevalent and infiltrative cancer type of the central nervous system, the prognosis of lower-grade glioma (LGG) in adults is highly heterogeneous. Recent evidence has demonstrated the prognostic value of the mRNA expression-based stemness index (mRNAsi) in LGG. Our aim was to develop a stemness index-based signature (SI-signature) for risk stratification and survival prediction.

Methods

Differentially expressed genes (DEGs) between LGG in the Cancer Genome Atlas (TCGA) and normal brain tissue samples from the Genotype-Tissue Expression (GTEx) project were screened out, and the weighted gene correlation network analysis (WGCNA) was employed to identify the mRNAsi-related gene sets. Meanwhile, the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed for the functional annotation of the key genes. ESTIMATE was used to calculate tumor purity for acquiring the correct mRNAsi. Differences in overall survival (OS) between the high and low mRNAsi (corrected mRNAsi) groups were compared using the Kaplan Meier analysis. By combining the Lasso regression with univariate and multivariate Cox regression, the SI-signature was constructed and validated using the Chinese Glioma Genome Atlas (CGGA).

Results

There was a significant difference in OS between the high and low mRNAsi groups, which was also observed in the two corrected mRNAsi groups. Based on threshold limits, 86 DEGs were most significantly associated with mRNAsi via WGCNA. Seven genes (ADAP2, ALOX5AP, APOBEC3C, FCGRT, GNG5, LRRC25, and SP100) were selected to establish a risk signature for primary LGG. The ROC curves showed a fair performance in survival prediction in both the TCGA and the CGGA validation cohorts. Univariate and multivariate Cox regression revealed that the risk group was an independent prognostic factor in primary LGG. The nomogram was developed based on clinical parameters integrated with the risk signature, and its accuracy for predicting 3- and 5-years survival was assessed by the concordance index, the area under the curve of the time-dependent receiver operating characteristics curve, and calibration curves.

Conclusion

The SI-signature with seven genes could serve as an independent predictor, and suggests the importance of stemness features in risk stratification and survival prediction in primary LGG.

LncRNA SNHG1 contributes to sorafenib resistance by activating the Akt pathway and is positively regulated by miR-21 in hepatocellular carcinoma cells

Background

Acquired resistance to sorafenib greatly limits its therapeutic efficiency in the treatment of hepatocellular carcinoma (HCC). Increasing evidence indicates that long noncoding RNAs (lncRNAs) play important roles in the resistance to anti-cancer drugs. The present study aims to explore the involvement of lncRNA SNHG1 (small nucleolar RNA host gene 1) in sorafenib resistance and how SNHG1 is associated with overexpressed microRNA-21 (miR-21) and the activated Akt pathway, which have been demonstrated to mediate this resistance in HCC cells.

Methods

Sorafenib-resistant HCC (SR-HCC) cells were generated and their sorafenib-resistant properties were confirmed by cell viability and apoptosis assays. Potential lncRNAs were screened by using multiple bioinformatics analyses and databases. The expression of genes and proteins was detected by qRT-PCR, Western blot and in situ hybridization. Gene silencing was achieved by specific siRNA or lncRNA Smart Silencer. The effects of anti-SNHG1 were evaluated in vitro and in experimental animals by using quantitative measures of cell proliferation, apoptosis and autophagy. The binding sites of miR-21 and SNHG1 were predicted by using the RNAhybrid algorithm and their interaction was verified by luciferase assays.

Results

The Akt pathway was highly activated by overexpressed miR-21 in SR-HCC cells compared with parental HCC cells. Among ten screened candidates, SNHG1 showed the largest folds of alteration between SR-HCC and parental cells and between vehicle- and sorafenib-treated cells. Overexpressed SNHG1 contributes to sorafenib resistance by activating the Akt pathway via regulating SLC3A2. Depletion of SNHG1 enhanced the efficacy of sorafenib to induce apoptosis and autophagy of SR-HCC cells by inhibiting the activation of Akt pathway. Sorafenib induced translocation of miR-21 to the nucleus, where it promoted the expression of SNHG1, resulting in upregulation of SLC3A2, leading to the activation of Akt pathway. In contrast, SNHG1 was shown to have little effect on the expression of miR-21, which downregulated the expression of PTEN, leading to the activation of the Akt pathway independently of SNHG1.

Conclusions

The present study has demonstrated that lncRNA SNHG1 contributes to sorafenib resistance by activating the Akt pathway and its nuclear expression is promoted by miR-21, whose nuclear translocation is induced by sorafenib. These results indicate that SNHG1 may represent a potentially valuable target for overcoming sorafenib resistance for HCC.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1177-0) contains supplementary material, which is available to authorized users.

Decreased autophagy was implicated in the decreased apoptosis during decidualization in early pregnant mice

Folate deficiency is a major risk factor of birth defects. Mechanistic studies on folate deficiency resulting in birth defects have mainly focused on fetal development. There have been few studies on folate deficiency from the point of view of the mother's uterus. In our previous study, we demonstrated that folate deficiency inhibits apoptosis of decidual cells, thereby restraining decidualization of the endometrium and impairing pregnancy. In this study, we further investigated the potential mechanism by which folate deficiency decreases endometrial apoptosis during decidualization. To investigate whether endometrium autophagy was inhibited under folate deficiency during decidualization, we performed real-time PCR for endometrial LC3 and P62 on day 6 (D6) to D8 of pregnancy in mice, and both were significantly changed compared to non-folate-deficient mice. Western blots showed that LC3-II and P62 were also changed in folate-deficient mice. Compared with control mice, a few punctuate LC3-II structures were detected in the folate deficiency group by immunofluorescence. Transmission electron micrographs of decidual cells on D8 showed that there were no evident autophagosomes in the folate deficiency group. In addition, apoptosis-related protein analysis by western blotting, TUNEL staining and flow cytometry showed that decreased endometrial apoptosis on D8 of pregnancy under folate deficiency was reversed after treatment with rapamycin, an autophagy inducer. ROS measurement showed that the endometrium ROS level was reduced by folate deficiency and that rapamycin reversed this effect on day 8 of pregnancy. All the results suggest that inhibiting endometrial autophagy may be implicated in the decreased endometrial apoptosis under folate deficiency during decidualization.

LC3-Associated Phagocytosis in Myeloid Cells Promotes Tumor Immune Tolerance

Targeting autophagy in cancer cells and in the tumor microenvironment are current goals of cancer therapy. However, components of canonical autophagy play roles in other biological processes, adding complexity to this goal. One such alternative function of autophagy proteins is LC3-associated phagocytosis (LAP), which functions in phagosome maturation and subsequent signaling events. Here, we show that impairment of LAP in the myeloid compartment, rather than canonical autophagy, induces control of tumor growth by tumor-associated macrophages (TAM) upon phagocytosis of dying tumor cells. Single-cell RNA sequencing (RNA-seq) analysis revealed that defects in LAP induce pro-inflammatory gene expression and trigger STING-mediated type I interferon responses in TAM. We found that the anti-tumor effects of LAP impairment require tumor-infiltrating T cells, dependent upon STING and the type I interferon response. Therefore, autophagy proteins in the myeloid cells of the tumor microenvironment contribute to immune suppression of T lymphocytes by effecting LAP.

Life, death and autophagy

Autophagy influences cell survival through maintenance of cell bioenergetics and clearance of protein aggregates and damaged organelles. Several lines of evidence indicate that autophagy is a multifaceted regulator of cell death, but controversy exists over whether autophagy alone can drive cell death under physiologically relevant circumstances. Here, we review the role of autophagy in cell death and examine how autophagy interfaces with other forms of cell death including apoptosis and necrosis.

An artificial lncRNA targeting multiple miRNAs overcomes sorafenib resistance in hepatocellular carcinoma cells

Sorafenib resistance remains a major obstacle for the effective treatment of hepatocellular carcinoma (HCC), and a number of miRNAs contribute to this resistance. However, the regulatory networks of miRNAs are very complex, thus inhibiting a single miRNA may sequentially activate other compensatory pathways. In the present study, we generated an artificial long non-coding RNA (AlncRNA), which simultaneously targets multiple miRNAs including miR-21, miR-153, miR-216a, miR-217, miR-494 and miR-10a-5p. These miRNAs have been shown to be upregulated in sorafenib-resistant cells and participate in the mechanisms underlying sorafenib resistance. The AlncRNA contains tandem sequences of 6 copies of the complementary binding sequences to the target miRNAs and is expressed by an adenoviral vector (Ad5-AlncRNA). Infection of Ad5-AlncRNA into sorafenib-resistant HCC cells blocked the function of miRNAs, and sequentially inhibited the downregulation of PTEN and activation of AKT. Ad5-AlncRNA significantly inhibited proliferation and induced apoptosis of sorafenib-resistant cells and enhanced the effects of sorafenib in vitro and in animal models. Inhibition of autophagy decreased the sensitivity of sorafenib-resistant cells to Ad5-AlncRNA, while its induction had the opposite effect. These results indicate that targeting multiple miRNAs by the artificial lncRNA could be a potential promising strategy for overcoming sorafenib resistance in the treatment of HCC.

Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018

Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field.

Fluorenyl-Loaded Quatsome Nanostructured Fluorescent Probes

Delivery of hydrophobic materials in biological systems, for example, contrast agents or drugs, is an obdurate challenge, severely restricting the use of materials with otherwise advantageous properties. The synthesis and characterization of a highly stable and water-soluble nanovesicle, referred to as a quatsome (QS, vesicle prepared from cholesterol and amphiphilic quaternary amines), that allowed the nanostructuration of a nonwater soluble fluorene-based probe are reported. Photophysical properties of fluorenyl-quatsome nanovesicles were investigated via ultraviolet-visible absorption and fluorescence spectroscopy in various solvents. Colloidal stability and morphology of the nanostructured fluorescent probes were studied via cryogenic transmission electronic microscopy, revealing a "patchy" quatsome vascular morphology. As an example of the utility of these fluorescent nanoprobes, examination of cellular distribution was evaluated in HCT 116 (an epithelial colorectal carcinoma cell line) and COS-7 (an African green monkey kidney cell line) cell lines, demonstrating the selective localization of C-QS and M-QS vesicles in lysosomes with high Pearson's colocalization coefficient, where C-QS and M-QS refer to quatsomes prepared with hexadecyltrimethylammonium bromide or tetradecyldimethylbenzylammonium chloride, respectively. Further experiments demonstrated their use in time-dependent lysosomal tracking.

The Role of Autophagy in Cancer

Autophagy is a highly conserved and regulated process that targets proteins and damaged organelles for lysosomal degradation to maintain cell metabolism, genomic integrity, and cell survival. The role of autophagy in cancer is dynamic and depends, in part, on tumor type and stage. Although autophagy constrains tumor initiation in normal tissue, some tumors rely on autophagy for tumor promotion and maintenance. Studies in genetically engineered mouse models support the idea that autophagy can constrain tumor initiation by regulating DNA damage and oxidative stress. In established tumors, autophagy can also be required for tumor maintenance, allowing tumors to survive environmental stress and providing intermediates for cell metabolism. Autophagy can also be induced in response to chemotherapeutics, acting as a drug-resistance mechanism. Therefore, targeting autophagy is an attractive cancer therapeutic option currently undergoing validation in clinical trials.

Beta 1-integrin-c-Met cooperation reveals an inside-in survival signalling on autophagy-related endomembranes

Receptor tyrosine kinases (RTKs) and integrins cooperate to stimulate cell migration and tumour metastasis. Here we report that an integrin influences signalling of an RTK, c-Met, from inside the cell, to promote anchorage-independent cell survival. Thus, c-Met and β1-integrin co-internalize and become progressively recruited on LC3B-positive 'autophagy-related endomembranes' (ARE). In cells growing in suspension, β1-integrin promotes sustained c-Met-dependent ERK1/2 phosphorylation on ARE. This signalling is dependent on ATG5 and Beclin1 but not on ATG13, suggesting ARE belong to a non-canonical autophagy pathway. This β1-integrin-dependent c-Met-sustained signalling on ARE supports anchorage-independent cell survival and growth, tumorigenesis, invasion and lung colonization in vivo. RTK-integrin cooperation has been assumed to occur at the plasma membrane requiring integrin 'inside-out' or 'outside-in' signalling. Our results report a novel mode of integrin-RTK cooperation, which we term 'inside-in signalling'. Targeting integrin signalling in addition to adhesion may have relevance for cancer therapy.

Lysosomal targeting with stable and sensitive fluorescent probes (Superior LysoProbes): applications for lysosome labeling and tracking during apoptosis

Intracellular pH plays an important role in the response to cancer invasion. We have designed and synthesized a series of new fluorescent probes (Superior LysoProbes) with the capacity to label acidic organelles and monitor lysosomal pH. Unlike commercially available fluorescent dyes, Superior LysoProbes are lysosome-specific and are highly stable. The use of Superior LysoProbes facilitates the direct visualization of the lysosomal response to lobaplatin elicited in human chloangiocarcinoma (CCA) RBE cells, using confocal laser scanning microscopy. Additionally, we have characterized the role of lysosomes in autophagy, the correlation between lysosome function and microtubule strength, and the alteration of lysosomal morphology during apoptosis. Our findings indicate that Superior LysoProbes offer numerous advantages over previous reagents to examine the intracellular activities of lysosomes.

Highly stable and sensitive fluorescent probes (LysoProbes) for lysosomal labeling and tracking

We report the design, synthesis and application of several new fluorescent probes (LysoProbes I-VI) that facilitate lysosomal pH monitoring and characterization of lysosome-dependent apoptosis. LysoProbes are superior to commercially available lysosome markers since the fluorescent signals are both stable and highly selective, and they will aid in characterization of lysosome morphology and trafficking. We predict that labeling of cancer cells and solid tumor tissues with LysoProbes will provide an important new tool for monitoring the role of lysosome trafficking in cancer invasion and metastasis.

Autophagy in cellular transformation, survival and communication with the tumor microenvironment

Autophagy describes several metabolic pathways, by which cytoplasmic constituents are imported into lysosomes for degradation. These pathways and in particular macroautophagy play an important role during oncogenesis by apparently inhibiting cellular transformation initially, but then ensuring tumor cell survival in established cancers. Furthermore, the conditioning of the tumor microenvironment, including the cross-talk with the immune system, is influenced by autophagy. These multiple facets of autophagy regulation in tumors will be discussed in the series of review articles of this issue of Seminars in Cancer Biology. A comprehensive understanding of this pathway in oncology is needed to efficiently apply autophagy regulating tumor therapies, which are already in use.