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Supplementary Table 3. Gene set enrichment analysis (GSEA) for RNA sequencing studies of MCF7 and MDA-MB-468 breast cancer cell lines expressing either a non-silencing (NS) shRNA or an ATG7 (A7) shRNA.

Supplementary Table 2. Significant genes with Q value < 0.01 in the MDA-MB-468 cell line.

Supplementary Table 1. Significant genes with Q value < 0.01 in the MCF7 cell line.

Supplementary Figures 1-3. Supplementary Figure 1. MCF7 and MDA-MB-468 cells were transduced with lentiviruses containing shRNAs for ATG7 or BECN1. Supplementary Figure 2. Principal Component Analysis of RNA sequencing data in autophagy-dependent (MDA-MB-468) and independent (MCF7) breast cancer cell lines. Supplementary Figure 3. Autophagy-regulated IL6 secretion increases mammosphere formation in the MCF7 breast cancer cell line.

PDF file - 1806K, Supplementary Figure S1. Hierarchical clustering of breast cancer cell lines transduced with an autophagy-focused shRNA library produced two main clusters. Supplementary Figure S2. ATG5, ATG7 and BECN1 shRNAs decreased protein levels in all cell lines tested. Supplementary Figure S3. Autophagy inhibition induces cell death in some cell lines but not others. MCF7, MDAMB231 and MDAMB468 cells were transduced with a lentivirus expressing shRNAs against ATG7 or BECN1, plated and evaluated for cell death with propidium iodide (red) staining after 48 h. Supplementary Figure S4. Triple negative cell lines have constitutively activated JAK/STAT pathway and autophagy regulates their STAT3 phosphorylation status.

MOV file - 3729K, MDAMB231 cells were transduced with a Non-silencing shRNA and imaged for 48h.

MOV file - 3141K, MCF7 cells were transduced with a Non-silencing shRNA and imaged for 48h.

PDF file - 117K, Supplementary table 1. Changes in shRNAs included in the autophagy library per cell line. Cells were transduced with a shRNA library containing autophagy-focused shRNAs. After transduction, the first sample (Post-transduction, PT) was collected. Growth sample (G) was collected after 15 days in culture. Both samples were done in quintuplicate. Table shows comparison of PT versus G samples. shRNAs were considered to be up (Sign Tag = U), or down-regulated (Sign Tag = D) in the growth sample when ANOVA p-value < 0.05 and fold change absolute value > 2.

MOV file - 2644K, MDAMB231 cells were transduced with an ATG7 shRNA and imaged for 48h.

MOV file - 2592K, MDAMB468 cells were transduced with an ATG7 shRNA and imaged for 48h.

MOV file - 2566K, MCF7 cells were transduced with an ATG7 shRNA and imaged for 48h.

Triple negative breast cancer (TNBC) is the breast cancer subtype with the worst prognosis and still lacks a targeted therapy. In this study, we found increased ERK phosphorylation in TNBC cell lines and an important role for ERK in sustaining the migration of TNBC cells. Although ROS have been suggested to have an important role in sustaining MAPK signaling, antioxidant treatment increased ERK phosphorylation, probably suggesting increased invasive potential. Interestingly, treatment with PD0325901 (PD), a MEK inhibitor, decreased ROS levels in TNBC cells and decreased mitochondrial fragmentation in the MDAMB231 cell line. Our data supports an important role for MEK/ERK in TNBC, sustaining cellular migration, regulating mitochondrial dynamics and ROS production in this breast cancer subtype.

Breast cancer is the most frequent type of cancer in women in the world. In Mexico, since 2006, this disease has become the leading cancer-related cause of death in women. It is estimated that incidence and mortality will continue to rise due to population aging, to changes in reproductive patterns, to a higher prevalence of risk factors and to limited access to medical care, resulting in delayed early diagnosis and timely treatment. The latter factors are the ones to improve in developing countries to decrease the high incidence and mortality associated with this disease. Recently, there is a great interest regarding breast cancer heterogeneity, and it is anticipated that the application of new technologies will improve our comprehension of this disease and will be reflected in a benefit for patients in the short term. Here, we review updated information on molecular diagnosis and therapeutics, as well as recent highlights in the biology of breast cancer.A nivel mundial, el cáncer de mama es el tipo de cáncer más frecuente en la mujer. En México, a partir del año 2006, esta enfermedad se ha convertido en la primera causa de muerte por cáncer en las mujeres. Se estima que la incidencia y mortalidad seguirán aumentando debido al envejecimiento poblacional, a los cambios en los patrones reproductivos, a una mayor prevalencia de los factores de riesgo y a los problemas para el acceso inmediato a la atención médica, teniendo como consecuencia retrasos para el diagnóstico temprano y el tratamiento oportuno. Estos últimos parecen ser los factores más importantes por mejorar en los países en desarrollo para tratar de disminuir la alta incidencia y mortalidad asociadas a la enfermedad. En años recientes, se ha generado un gran interés sobre la heterogeneidad del cáncer de mama y se anticipa que la aplicación de nuevas tecnologías pueda mejorar nuestra comprensión de cada uno de los subtipos de la enfermedad y lograr así un beneficio para las pacientes a corto plazo. Esta revisión pretende recopilar información actualizada sobre los avances en diagnósticos moleculares y terapéuticos, así como en la comprensión de la biología de la enfermedad.

Background Dysregulation of glycogene expression in cancer can lead to aberrant glycan expression, which can promote tumorigenesis. Cervical cancer (CC) displays an increased expression of glycogenes involved in sialylation and sialylated glycans. Here, we show a comprehensive analysis of glycogene expression in CC to identify glycogene expression signatures and the possible glycosylation pathways altered. Methods First, we performed a microarray expression assay to compare glycogene expression changes between normal and cervical cancer tissues. Second, we used 401 glycogenes to analyze glycogene expression in adenocarcinoma and squamous carcinoma from RNA-seq data at the cBioPortal for Cancer Genomics. Results The analysis of the microarray expression assay indicated that CC displayed an increase in glycogenes related to GPI-anchored biosynthesis and a decrease in genes associated with chondroitin and dermatan sulfate with respect to normal tissue. Also, the glycogene analysis of CC samples by the RNA-seq showed that the glycogenes involved in the chondroitin and dermatan sulfate pathway were downregulated. Interestingly the adenocarcinoma tumors displayed a unique glycogene expression signature compared to squamous cancer that shows heterogeneous glycogene expression divided into six types. Squamous carcinoma type 5 (SCC-5) showed increased expression of genes implicated in keratan and heparan sulfate synthesis, glycosaminoglycan degradation, ganglio, and globo glycosphingolipid synthesis was related to poorly differentiated tumors and poor survival. Squamous carcinoma type 6 (SCC-6) displayed an increased expression of genes involved in chondroitin/dermatan sulfate synthesis and lacto and neolacto glycosphingolipid synthesis and was associated with nonkeratinizing squamous cancer and good survival. In summary, our study showed that CC tumors are not a uniform entity, and their glycome signatures could be related to different clinicopathological characteristics.

Cancer is one of the major causes of death in the world and its global burden is expected to continue increasing. In several types of cancers, reactive oxygen species (ROS) have been extensively linked to carcinogenesis and cancer progression. However, studies have reported conflicting evidence regarding the role of ROS in cancer, mostly dependent on the cancer type or the step of the tumorigenic process. We review recent studies describing diverse aspects of the interplay of ROS with cancer in the different stages of cancer progression, with a special focus on their role in carcinogenesis, their importance for cancer cell signaling and their relationship to the most prevalent cancer risk factors.

Breast cancer (BC) is the leading cause of cancer-related death in women in the world. Since tumor cells employ autophagy as a survival pathway, it has been proposed that autophagy inhibition could be beneficial for cancer treatment. There are several onging clinical trials where autophagy is being inhibited (using chloroquine, CQ or hydroxychloroquine, HCQ) along with chemotherapy with promising results. However, there is also in vitro evidence in which autophagy inhibition can induce epithelial to mesenchymal transition (EMT) in cancer cells, indicating that, at least in some cases, this strategy could be detrimental for cancer patients. In this study, we found that the genetic inhibition of autophagy primed cells for EMT by inducing a decrease in E-cadherin protein levels, while CQ treatment decreased E-cadherin levels, induced morphological changes related to EMT, increased EMT-related transcription factor (EMT-TF) expression and migration in estrogen receptor positive (ER +) BC cell lines. Importantly, CQ treatment increased intracellular reactive oxygen species (ROS) which induced the secretion of macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine related to malignancy. Both ROS production and MIF secretion were responsible for the mesenchymal morphology and increased migratory capacity induced by CQ. Our results indicate that CQ treatment increased malignancy by inducing ROS production, MIF secretion and EMT and suggest that autophagy inhibition in ER + BC patients might have detrimental effects. Our data indicates that a careful selection of patients should be performed in order to determine who will benefit the most from autophagy inhibition with available pharmacological agents for the treatment of breast cancer.

Estrogens demonstrate biological activity in numerous organ systems, including the immune system, and exert their effects through estrogen receptors (ER) of two types: intracellular ERα and ERβ that activate transcriptional factors and membrane G protein-coupled ER GPER. The latter is capable to mediate fast activation of cytosolic signaling pathways, influencing transcriptional events in response to estrogens. Tamoxifen (TAM), widely used in chemotherapy of ERα-positive breast cancer, is considered as an ERα antagonist and GPER agonist. TAM was shown to possess “off-target” cytotoxicity, not related to ER in various tumor types. The present work was designed to study biological effects of TAM on the glucocorticoid (GC)-resistant cell line Jurkat, derived from acute lymphoblastic leukemia of T lineage (T-ALL). We have shown that T-ALL cell lines, in contrast to healthy T cells, express only GPER, but not ERα or ERβ. TAM compromised mitochondrial function and reduced the viability and proliferation of Jurkat cells. Additionally, TAM induced autophagy in a GPER-dependent manner. Gene expression profiling revealed the up-regulation of autophagy-related gene ATG5. Interestingly, TAM sensitized Jurkat cells to dexamethasone (DEX) treatment, which may be related to its capacity to cause autophagy. We suggest that TAM-based adjuvant therapy may represent a novel strategy in T-ALL patients handling.

Background Aberrant glycosylation is a characteristic of tumour cells. The expression of certain glycan structures has been associated with poor prognosis. In cervical carcinoma, changes in the expression levels of some glycogenes have been associated with lymph invasion. Human papillomavirus (HPV) infection is one of the most important factors underlying the development of cervical cancer. The HPV oncoproteins E6 and E7 have been implicated in cervical carcinogenesis and can modify the host gene expression profile. The roles of these oncoproteins in glycosylation changes have not been previously reported. Methods To determine the effect of the E6 and E7 oncoproteins on glycogene expression we partially silenced the E6 and E7 oncogenes in HeLa cells, we performed a microarray expression assay to identify altered glycogenes and quantified the mRNA levels of glycogenes by RT-qPCR. A protein-protein interaction network was constructed to identify potentially altered glycosylation pathways. Results The microarray analysis showed 9 glycogenes that were upregulated and 7 glycogenes that were downregulated in HeLa shE6/E7 cells. Some of these genes participate in glycosylation related to Notch proteins and O-glycans antigens. Conclusions Our results support that E6 and E7 oncoproteins could modify glycogene expression the products of which participate in the synthesis of structures implicated in proliferation, adhesion and apoptosis.

Aedes aegypti and Aedes albopictus mosquitoes are responsible for dengue virus (DENV) transmission in tropical and subtropical areas worldwide, where an estimated 3 billion people live at risk of DENV exposure. DENV-infected individuals show symptoms ranging from sub-clinical or mild to hemorrhagic fever. Infected mosquitoes do not show detectable signs of disease, even though the virus maintains a lifelong persistent infection. The interactions between viruses and host mitochondria are crucial for virus replication and pathogenicity. DENV infection in vertebrate cells modulates mitochondrial function and dynamics to facilitate viral proliferation. Here, we describe that DENV also regulates mitochondrial function and morphology in infected C6/36 mosquito cells (derived from Aedes albopictus). Our results showed that DENV infection increased ROS (reactive oxygen species) production, modulated mitochondrial transmembrane potential and induced changes in mitochondrial respiration. Furthermore, we offer the first evidence that DENV causes translocation of mitofusins to mitochondria in the C6/36 mosquito cell line. Another protein Drp-1 (Dynamin-related protein 1) did not localize to mitochondria in DENV-infected cells. This observation therefore ruled out the possibility that the abovementioned alterations in mitochondrial function are associated with mitochondrial fission. In summary, this report provides some key insights into the virus–mitochondria crosstalk in DENV infected mosquito cells.

Autophagy can function as a survival mechanism for cancer cells and therefore, its inhibition is currently being explored as a therapy for different cancer types. For breast cancer, triple negative breast cancer (TNBC) is the subtype most sensitive to the inhibition of autophagy; but its inhibition has also been shown to promote ROS-dependent secretion of macrophage migration inhibitory factor (MIF), a pro-tumorigenic cytokine. In this work, we explore the role of MIF in breast cancer, the mechanism by which autophagy inhibition promotes MIF secretion and its effects on neighboring cancer cell signaling and macrophage polarization. We analyzed MIF mRNA expression levels in tumors from breast cancer patients from different subtypes and found that Luminal B, HER2 and Basal subtypes, which are associated to high proliferation, displayed high MIF levels. However, MIF expression had no prognostic relevance in any breast cancer subtype. In addition, we found that autophagy inhibition in 66cl4 TNBC cells increased intracellular Reactive Oxygen Species (ROS) levels, which increased MIF expression and secretion. MIF secreted from 66cl4 TNBC cells induced the activation of MIF-regulated pathways in syngeneic cell lines, increasing Akt phosphorylation in 4T1 cells and ERK phosphorylation in 67NR cells. Regarding MIF/ chemokine receptors, higher levels of CD74 and CXCR2 were found in TNBC tumor cell lines when compared to non-tumorigenic cells and CXCR7 was elevated in the highly metastatic 4T1 cell line. Finally, secreted MIF from autophagy deficient 66cl4 cells induced macrophage polarization towards the M1 subtype. Together, our results indicate an important role for the inhibition of autophagy in the regulation of ROS-mediated MIF gene expression and secretion, with paracrine effects on cancer cell signaling and pro-inflammatory repercussions in macrophage M1 polarization. This data should be considered when considering the inhibition of autophagy as a therapy for different types of cancer.

The aim of our work is to evaluate potential undesirable effects of autophagy inhibition in breast cancer subtypes which are not sensitive to the inhibition of autophagy. Worldwide, BC is the most frequent cancer in women. Despite recent advances in diagnosis, molecular stratification and targeted therapy, BC is still the leading cause of cancer-related death in women. Thus, it is a public health issue that must be attended. In cancer, autophagy has a pro-tumorigenic role that helps tumor cells survive metabolic stress and growth factor deprivation, hypoxia, maintain tumor initiating cells, confer therapy resistance and modulate epithelial mesenchymal transition (EMT). Because tumor cells benefit from autophagy, it has been proposed that autophagy inhibition could be beneficial for cancer treatment. Nowadays, there are clinical trials where autophagy is being inhibited with promising results that encourage this approach. However, in these clinical trials, cancer types are not been stratified and autophagy is being inhibited in many solid tumor types. In this regard, there is also in vitro evidence in which autophagy inhibition in some cancer types induces EMT, which in the clinic could be detrimental for patients. This highlights the urgency for stratifying patients that will benefit the most from autophagy inhibition. In this work, autophagy inhibition in MCF7 ER+ cell line increased secretion, inflammation and EMT related pathways suggesting induction of malignancy. Autophagy inhibition induced changes in cell morphology in ER+ breast cancer cell lines (MCF7 and T47D) when evaluated by aspect ratio estimation changing from a cobblestone -like epithelial morphology to a fibroblast-like morphology. No changes in cell morphology were found in MCF10A and MDAMB231 cell lines. Changes in morphology were accompanied by a decrease in E-cadherin protein levels suggesting induction of EMT. Our results suggest that CQ treatment in ER+ BC cells could induce a malignant process related to EMT. Thus, ER+ BC patients may not benefit from autophagy inhibition. Nowadays, there are clinical trials where autophagy is being inhibited and no subtype stratification is being done, so we encourage to stratify patients to determine who will be benefited the most from autophagy inhibition and who will not. Citation Format: Guadalupe Rojas, Nidia Pazos, Paola Maycotte. Effect of autophagy inhibition on epithelial mesenchymal transition in breast cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2836.

Autophagy is an intracellular recycling process active in eukaryotic cells which involves the formation of an autophagosome that delivers cytoplasmic components to the lysosome for degradation. This process occurs at low rates under basal conditions, but it can be induced by diverse stress conditions such as starvation, hypoxia or metabolic disorders. Autophagic flux can also be enhanced in response to hormones, including leptin. Leptin is considered a pro-tumorigenic protein whose circulating levels have been related to a bad prognosis in obese breast cancer patients. It has been recently demonstrated that leptin can induce autophagy in cancer cell lines from different tissues, suggesting that autophagy could modulate the pro-tumorigenic effects associated with leptin. In this study, the role of autophagy in leptin-induced proliferation, migration, apoptosis and ERK phosphorylation in breast cancer cell lines was evaluated. Methods: MCF7 estrogen receptor positive and MDA-MB-231 triple negative breast cancer cell lines were used. MCF7 and MDA-MB-231 cell lines were stimulated with 400 and 50 ng/ml of leptin, respectively. Autophagy was assessed by LC3-II and p62 protein levels by western blot, and autophagosome formation by fluorescence microscopy. Proliferation and migration were assessed by real-time microscopy in an IncuCyte analyzer; and cell death was evaluated by fluorescence analysis of caspase activity. Changes in ERK phosphorylation were measure by western blot. Results: Leptin increased autophagy in MCF7 cells but not in triple negative MDA-MB-231 cells. In MCF7 cells, autophagy inhibition reduced leptin-induced cell proliferation, changes associated to a mesenchymal morphology, cell migration, and ERK activation. In MDA-MB-231 cells, autophagy inhibition reduced proliferation and increased apoptosis independently of leptin treatment. In both cell lines, leptin-induced migration and ERK phosphorylation were reduced by the inhibition of autophagy. Conclusion: Autophagy was important for increased cancer cell migration induced by leptin and for the maintenance of ERK phosphorylation. Our data suggest a potential use for the inhibition of autophagy in breast cancer associated with obesity. Citation Format: Alin García Miranda, Karen A. Solano Alcalá, José B. Montes Alvarado, Julio Reyes Leyva, Paola Maycotte, Eduardo Castañeda Saucedo. Autophagy mediates leptin induced migration and erk activation in breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1940.

Neurodegenerative diseases are a group of heterogeneous diseases characterized by a gradual, progressive and selective decrease in nervous system functions. The etiology of these pathologies remains unknown; however, mitochondrial function has been proposed as a common factor that could be involved in the establishment of these diseases, owing to the high energy requirement neurons have in order to carry out their physiological functions. Mitochondria are extremely dynamic organelles that can change their morphology and function in response to different physiological stimuli and, for this reason, mitochondrial dynamics have started being studied as one of cell survival main regulators. This event comprises different processes, such as the generation of new mitochondria and their elimination when they are no longer functional, as well as mitochondrial fusion and fission processes and the traffic of these organelles within the cellular environment. All these processes are highly regulated, and their main purpose is optimal functionality of mitochondria and cellular homeostasis.Las enfermedades neurodegenerativas son un grupo heterogéneo caracterizado por la disminución gradual, progresiva y selectiva de las funciones del sistema nervioso. La etiología de estas patologías aún se desconoce, sin embargo, se ha propuesto que la función mitocondrial pudiese estar participando en el establecimiento de estas enfermedades, debido al alto requerimiento energético que tienen las neuronas para realizar sus funciones fisiológicas. La mitocondria es un organelo dinámico que puede cambiar su morfología y función en respuesta a diferentes estímulos fisiológicos, por ello se ha empezado a estudiar a la dinámica mitocondrial como uno de los principales reguladores de la supervivencia celular. Este evento comprende diferentes procesos como la generación de nuevas mitocondrias y su eliminación cuando ya no son funcionales, así como los procesos de fusión y fisión mitocondrial y el tráfico de estos organelos en el entorno celular. Todos estos procesos son altamente regulados y tienen como finalidad la óptima funcionalidad de la mitocondria y la homeostasis celular.

Autophagy is a protein and organelle degradation pathway important for the maintenance of cytoplasmic homeostasis and for providing nutrients for survival in response to stress conditions. Recently, autophagy has been shown to be important for the secretion of diverse proteins involved in inflammation, intercellular signaling, and cancer progression. The role of autophagy in cancer depends on the stage of tumorigenesis, serving a tumor-suppressor role before transformation and a tumor-survival function once a tumor is established. We review recent evidence demonstrating the complexity of autophagy regulation during cancer, considering the interaction of autophagy with protein secretion pathways. Autophagy manipulation during cancer treatment is likely to affect protein secretion andinter-cellular signaling either to the neighboring cancer cells or to the antitumoral immune response. This will be an important consideration during cancer therapy since several clinical trials are trying to manipulate autophagy in combination with chemotherapy for the treatment of diverse types of cancers.

The autophagy pathway has been recognized as a mechanism of survival and therapy resistance in cancer, yet the extent of autophagy’s function in metastatic progression is still unclear. Therefore, we used murine models of metastatic cancer to investigate the effect of autophagy modulation on metastasis development. Pharmacologic and genetic autophagy inhibition were able to impede cell proliferation in culture, but did not impact the development of experimentally induced 4T1 and B16-F10 metastases. Similarly, autophagy inhibition by adjuvant chloroquine (CQ) treatment did not delay metastasis in an orthotopic 4T1, tumor-resection model. However, neoadjuvant CQ treatment or genetic autophagy inhibition resulted in delayed metastasis development, whereas stimulation of autophagy by trehalose hastened development. Cisplatin was also administered either as a single agent or in combination with CQ. The combination of cisplatin and CQ was antagonistic. The effects of autophagy modulation on metastasis did not appear to be due to alterations in the intrinsic metastatic capability of the cells, as modulating autophagy had no impact on migration, invasion, or anchorage-independent growth in vitro. To explore the possibility of autophagy’s influence on the metastatic microenvironment, bone marrow–derived cells (BMDCs), which mediate the establishment of the premetastatic niche, were measured in the lung and in circulation. Trehalose-treated mice had significantly more BMDCs than either vehicle- or CQ-treated mice. Autophagy inhibition may be most useful as a treatment to impede early metastatic development. However, modulating autophagy may also alter the efficacy of platinum-based therapies, requiring caution when considering combination therapies.

Breast cancer is the main cause of cancer-related death in women in the world. Because autophagy is a known survival pathway for cancer cells, its inhibition is currently being explored in clinical trials for treating several types of malignancies. In breast cancer, autophagy has been shown to be necessary for the survival of cancer cells from the triple negative subtype (TNBC), which has the worst prognosis among breast cancers and currently has limited therapeutic options. Autophagy has also been involved in the regulation of protein secretion and, of importance for this work, the inhibition of autophagy is known to promote the secretion of proinflammatory cytokines from distinct cell types. We found that the inhibition of autophagy in TNBC cell lines induced the secretion of the macrophage migration inhibitory factor (MIF), a pro-tumorigenic cytokine involved in breast cancer invasion and immunomodulation. MIF secretion was dependent on an increase in reactive oxygen species (ROS) induced by the inhibition of autophagy. Importantly, MIF secreted from autophagy-deficient cells increased the migration of cells not treated with autophagy inhibitors, indicating that autophagy inhibition in cancer cells promoted malignancy in neighboring cells through the release of secreted factors, and that a combinatorial approach should be evaluated for cancer therapy.

Plants from the Bursera genus are widely distributed in the tropical dry forests of Mexico. In traditional medicine, extracts from different species of Bursera have been used for a wide range of biological activities, including the treatment of cancer-related symptoms. Compounds present in the Bursera genus include lignans, flavonoids, steroids, short-chain aliphatic alkanes, acetates, alcohols, ketones, and terpenoids. In some instances, secondary metabolites of these classes of compounds may induce cytotoxicity, and therefore we sought to investigate the effects of B. copallifera leaf extracts in breast cancer cell lines to evaluate their potential therapeutic value for the treatment of breast cancer, one of the most prevalent types of cancer in women worldwide. Two B. copallifera leaf extracts exerted cytotoxic effects on both the MCF7 and MDA-MB-231 breast cancer cell line models. The cytotoxic effect was more evident in the MDA-MB-231 triple negative cell line inhibiting also the migration of these cells. We identified hydroxycinnamic acid and flavonol derivatives as major phenolic components of the extracts. Our results strongly suggest a potential use of the Bursera leaf extracts rich in phenolic compounds, their individual phenolic compounds, or their combinations for the treatment of breast cancer.

Autophagy is a mechanism by which cells degrade cellular material to provide nutrients and energy for survival during stress. The autophagy is thought to be a critical process for cancer stem cell (CSC) or tumor-initiating cell maintenance but the mechanisms by which autophagy supports survival of CSCs remain poorly understood. In this study, inhibition of autophagy by knockdown of ATG7 or BECN1 modified the CD44+/CD24low/− population in breast cancer cells by regulating CD24 and IL6 secretion. In a breast cancer cell line that is independent of autophagy for survival, autophagy inhibition increased IL6 secretion to the media. On the other hand, in an autophagy-dependent cell line, autophagy inhibition decreased IL6 secretion, cell survival, and mammosphere formation. In these cells, IL6 treatment or conditioned media from autophagy-competent cells rescued the deficiency in mammosphere formation induced by autophagy inhibition. These results reveal that autophagy regulates breast CSC maintenance in autophagy-dependent breast cancer cells by modulating IL6 secretion implicating autophagy as a potential therapeutic target in breast cancer. Implications: Modulation of autophagy in breast cancer has different and even opposite effects, indicating the need for a selection strategy when trying to manipulate autophagy in the context of cancer therapy. Mol Cancer Res; 13(4); 651–8. ©2015 AACR.

Chloroquine (CQ) is an antimalarial drug and late-stage inhibitor of autophagy currently FDA-approved for use in the treatment of rheumatoid arthritis and other autoimmune diseases. Based primarily on its ability to inhibit autophagy, CQ and its derivative, hydroxychloroquine, are currently being investigated as primary or adjuvant therapy in multiple clinical trials for cancer treatment. Oncogenic RAS has previously been shown to regulate autophagic flux, and cancers with high incidence of RAS mutations, such as pancreatic cancer, have been described in the literature as being particularly susceptible to CQ treatment, leading to the hypothesis that oncogenic RAS makes cancer cells dependent on autophagy. This autophagy "addiction" suggests that the mutation status of RAS in tumors could identify patients who would be more likely to benefit from CQ therapy. Here we show that RAS mutation status itself is unlikely to be beneficial in such a patient selection because oncogenic RAS does not always promote autophagy addiction. Moreover, oncogenic RAS can have opposite effects on both autophagic flux and CQ sensitivity in different cells. Finally, for any given cell type, the positive or negative effect of oncogenic RAS on autophagy does not necessarily predict whether RAS will promote or inhibit CQ-mediated toxicity. Thus, although our results confirm that different tumor cell lines display marked differences in how they respond to autophagy inhibition, these differences can occur irrespective of RAS mutation status and, in different contexts, can either promote or reduce chloroquine sensitivity of tumor cells.

Autophagy is a protein and organelle degradation pathway that is involved in diverse diseases, including cancer. Recent evidence suggests that autophagy is a cell survival mechanism in tumor cells and that its inhibition, especially in combination with other therapy, could be beneficial but it remains unclear if all cancer cells behave the same way when autophagy is inhibited. We inhibited autophagy in a panel of breast cancer cell lines and found that some of them are dependent on autophagy for survival even in nutrient rich conditions without any additional stress, whereas others need autophagy only when stressed. Survival under unstressed conditions is due to cell type–specific autophagy regulation of STAT3 activity and this phenotype is enriched in triple-negative cell lines. This autophagy-dependency affects response to therapy because autophagy inhibition reduced tumor growth in vivo in autophagy-dependent but not in autophagy-independent breast tumors, whereas combination treatment with autophagy inhibitors and other agent was preferentially synergistic in autophagy-dependent cells. These results imply that autophagy-dependence represents a tumor cell–specific characteristic where autophagy inhibition will be more effective. Moreover, our results suggest that autophagy inhibition might be a potential therapeutic strategy for triple-negative breast cancers, which currently lack an effective targeted treatment. Cancer Res; 74(9); 2579–90. ©2014 AACR.

The manipulation of autophagy for cancer therapy has gained recent interest in clinical settings. Although inhibition of autophagy is currently being used in clinical trials for the treatment of several malignancies, autophagy has been shown to have diverse implications for normal cell homeostasis, cancer cell survival, and signaling to cells in the tumor microenvironment. Among these implications and of relevance for cancer therapy, the autophagic process is known to be involved in the regulation of protein secretion, in tumor cell immunogenicity, and in the regulation of epithelial-to-mesenchymal transition (EMT), a critical step in the process of cancer cell invasion. In this work, we have reviewed recent evidence linking autophagy to the regulation of EMT in cancer and normal epithelial cells, and have discussed important implications for the manipulation of autophagy during cancer therapy.