Mitochondria of highly metastatic breast cancer cell line MDA-MB-231 exhibits increased autophagic properties

Context-dependent roles for ubiquitous mitochondrial creatine kinase CKMT1 in breast cancer progression

Metabolic reprogramming is a hallmark of cancer, enabling cancer cells to rapidly proliferate, invade, and metastasize. We show that creatine levels in metastatic breast cancer cell lines and secondary metastatic tumors are driven by the ubiquitous mitochondrial creatine kinase (CKMT1). We discover that, while CKMT1 is highly expressed in primary tumors and promotes cell viability, it is downregulated in metastasis. We further show that CKMT1 downregulation, as seen in breast cancer metastasis, drives up mitochondrial reactive oxygen species (ROS) levels. CKMT1 downregulation contributes to the migratory and invasive potential of cells by ROS-induced upregulation of adhesion and degradative factors, which can be reversed by antioxidant treatment. Our study thus reconciles conflicting evidence about the roles of metabolites in the creatine metabolic pathway in breast cancer progression and reveals that tight, context-dependent regulation of CKMT1 expression facilitates cell viability, cell migration, and cell invasion, which are hallmarks of metastatic spread.

A Low Dose Combination of Withaferin A and Caffeic Acid Phenethyl Ester Possesses Anti-Metastatic Potential In Vitro: Molecular Targets and Mechanisms

Simple Summary

Cancer therapy suffers from its high cost and high rate of adverse effects and relapse of the disease. Hence, the new (preferably natural), economic and safer therapeutic as well preventive measures have been on demand and have been subject of priority research. We have, earlier, demonstrated anticancer activity in the extracts of Ashwagandha leaves and propolis. A combination of Wi-A (an active anticancer ingredient in Ashwagandha extract) and CAPE (an active anticancer ingredient in propolis) was earlier shown to offer higher and cancer cell-selective cytotoxicity. In the present study, we report an anti-metastasis activity in the low dose combination of Wi-A and CAPE along with its mechanism of action and propose its use in cancer metastasis treatment.

Abstract

Withaferin A (Wi-A) and Caffeic Acid Phenethyl Ester (CAPE) are the bioactive ingredients of Ashwagandha (Withania somnifera) and propolis, respectively. Both of these natural compounds have been shown to possess anticancer activity. In the present study, we recruited a low dose of each of these compounds and developed a combination that exhibited remarkably potent anti-migratory and anti-angiogenic activities. Extensive molecular analyses including a cDNA array and expression analyses of the specific gene targets demonstrated that such activities are mediated through their effect on cell adhesion/tight junction proteins (Claudins, E-cadherin), inhibition of canonical Wnt/β-catenin signaling pathways and the consequent downregulation of EMT-signaling proteins (Vimentin, MMPs, VEGF and VEGFR) that play a critical role in cancer metastasis. The data supported that this novel combination of Wi-A and CAPE (Wi-ACAPE, containing 0.5 µM of Wi-A and 10 µM of CAPE) may be recruited for the treatment of metastatic and aggressive cancers and, hence, warrant further evaluation by recruiting a variety of experimental and clinical metastatic models.

Mitochondria-related core genes and TF-miRNA-hub mrDEGs network in breast cancer

Background: Mitochondria-nuclear cross-talk and mitochondrial retrograde regulation are involved in the genesis and development of breast cancer (BC). Therefore, mitochondria can be regarded as a promising target for BC therapeutic strategies. The present study aimed to construct regulatory network and seek the potential biomarkers of BC diagnosis and prognosis as well as the molecular therapeutic targets from the perspective of mitochondrial dysfunction. Methods: The microarray data of mitochondria-related encoding genes in BC cell lines were downloaded from GEO including GSE128610 and GSE72319. GSE128610 was treated as test set and validation sets consisted of GSE72319 and TCGA tissue samples, intending to identify mitochondria-related differentially expressed genes (mrDEGs). We performed enrichment analysis, PPI network, hub mrDEGs and overall survival analysis and constructed transcription factor (TF)-miRNA-hub mrDEGs network. Results: A total of 23 up-regulated and 71 down-regulated mrDEGs were identified and validated in BC cell lines and tissues. Enrichment analyses indicated that mrDEGs were associated with several cancer-related biological processes. Moreover, 9 hub mrDEGs were identified and validated in BC cell lines and tissues. Finally, 5 hub coregulated mrDEGs, 21 miRNAs and 117 TFs were used to construct TF-miRNA-hub mrDEGs network. MYC associated zinc finger protein (MAZ), heparin binding growth factor (HDGF) and Sp2 transcription factor (SP2) regulated 3 hub mrDEGs. Hsa-mir-21-5p, hsa-mir-1-3p, hsa-mir-218-5p, hsa-mir-26a-5p and hsa-mir-335-5p regulated 2 hub mrDEGs. Overall survival analysis suggested that the up-regulation of fibronectin 1 (FN1), as well as the down-regulation of discoidin domain receptor tyrosine kinase 2 (DDR2) correlated with unfavorable prognosis in BC. Conclusion: TF-miRNA-hub mrDEGs had instruction significance for the exploration of BC etiology. The hub mrDEGs such as FN1 and DDR2 were likely to regulate mitochondrial function and be novel biomarkers for BC diagnosis and prognosis as well as the therapeutic targets.

Human-specific GAPDH qRT-PCR is an accurate and sensitive method of xenograft metastasis quantification

Metastasis is the primary cause of cancer-related mortality. Experimental models that accurately reflect changes in metastatic burden are essential tools for developing treatments and to gain a better understanding of disease. Murine xenograft tumor models mimic the human scenario and provide a platform for metastasis analyses. An ex vivo quantitative method, gaining favor for its ease and accuracy, is quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR); however, it is currently unclear how well this method correlates with gold-standard histological analysis, and its use has required detection of overexpressed exogenous genes. We have introduced a variation of the qRT-PCR method: human-specific glyceraldehyde 3-phosphate dehydrogenase (GAPDH) qRT-PCR, which allows quantification of metastasis in xenograft models without the requirement of overexpressed exogenous genes. This makes the method easily amenable to many xenograft models without alteration of the cancer cells. We determined that the method is able to detect a few human cells within abundant mouse lung tissue. Further, the human-specific GAPDH qRT-PCR is more sensitive and correlates with histological analysis in terms of determining relative metastatic burden, suggesting that human-specific GAPDH qRT-PCR could be used as a primary method for quantification of disseminated human cells in murine xenograft models.

Insulin-Induced Gene 2 Expression Is Associated with Breast Cancer Metastasis

Insulin-induced gene 2 (INSIG2) functions as a blocker of cholesterol biosynthesis and has been shown to be involved in colon and pancreatic cancer pathogenesis. Cholesterol is a risk factor for breast cancer pathophysiology; however, the underlying mechanisms are not well-defined. Hence, our goal was to determine the role of INISG2 in breast cancer. INSIG2 mRNA and protein expression was correlated to metastatic potential of breast cancer cell lines. Knockdown of INSIG2 inhibited epithelial-to-mesenchymal transition. Conversely, overexpression of INSIG2 induced epithelial-to-mesenchymal transition. Knockdown of INSIG2 did not affect cell proliferation but resulted in altered metabolism in vitro and attenuated experimental metastasis in vivo. Analysis of breast cancer tissue microarrays revealed significantly higher INSIG2 protein expression in breast cancer tissues. INSIG2 protein expression was correlated to hormone receptor status, with significantly higher expression in patients with triple-negative and human epidermal growth factor receptor 2 molecular subtypes of invasive breast cancer. Analysis of The Cancer Genome Atlas, however, revealed significantly lower INSIG2 mRNA expression in triple-negative breast cancer patients. Higher INSIG2 mRNA expression was correlated to poor survival probability. Asian patients with high INSIG2 mRNA expression had significantly lower survival probability compared with Asian patients with low/medium INSIG2 mRNA expression. These results reveal a yet undefined role of INSIG2 in breast cancer, potentially more relevant for breast cancer patients in Asia.

Inhibitory effect of melatonin on hypoxia-induced vasculogenic mimicry via suppressing epithelial-mesenchymal transition (EMT) in breast cancer stem cells

Vasculogenic mimicry (VM) play an important role in breast cancer metastasis and anti- angiogenic drugs resistance. Hypoxia, the epithelial-mesenchymal transition (EMT), and cancer stem cells (CSCs) are known as essential factors for VM formation. Also, melatonin is an amino acid-derived hormone with many anti-tumor effects. Despite the antitumor effects of melatonin, its effect on VM formation in breast cancer has not been considered yet, so we investigated the effect of melatonin on VM formation through EMT process under hypoxia conditions in breast CSCs. The CSCs percentage and VM formation were determined in MCF-7 and MDA-MB-231, respectively. Also, analysis of HIF-1α expression under hypoxia in MDA-MB-231 and MCF-7 cell lines was performed using Western blot. The effect of melatonin on the VM formation, invasion, and migration was also investigated. Moreover, the effect of melatonin on the expression EMT markers was evaluated. CD44⁺ CD24^-phenotype as CSCs marker in MDA-MB-231 cell line, was 80.8%, while it was 11.1% in MCF-7 cell line. HIF-1α expression was up-regulated in the VM-positive breast cancer cell line MDA-MB-231, and consequently, affected the expression of the EMT markers E-cadherin, vimentin, snail, and MMP9. Melatonin had significant effect on EMT and formations of VM in breast CSCs. Melatonin could prevent the formation of VM by affecting the important molecules involved in the formation of VM structures and the EMT. Moreover, our data clearly showed that, melatonin represents molecule with significant anti-cancer activities that may potentially optimize the management of breast cancer through the overcoming drug resistance in anti-angiogenic drugs.

Breast Cancer Subtypes Present a Differential Production of Reactive Oxygen Species (ROS) and Susceptibility to Antioxidant Treatment

Due to their crucial role in cell metabolism and homeostasis, alterations in mitochondrial biology and function have been related to the progression of diverse diseases including cancer. One of the consequences associated to mitochondrial dysfunction is the production of reactive oxygen species (ROS). ROS are known to have a controversial role during cancer initiation and progression and although several studies have tried to manipulate intracellular ROS levels using antioxidants or pro-oxidation conditions, it is not yet clear how to target oxidation for cancer therapy. In this study, we found differences in mitochondrial morphology in breast cancer cells when compared to a non-tumorigenic cell line and differences in mitochondrial function among breast cancer subtypes when exploring gene-expression data from the TCGA tumor dataset. Interestingly, we found increased ROS levels in triple negative breast cancer (TNBC) cell lines and a dependency on ROS for survival since antioxidant treatment induced cell death in TNBC cells but not in an estrogen receptor positive (ER+) cell line. Moreover, we identified the mitochondria as the main source of ROS in TNBC cell lines. Our results indicate a potential use for ROS as a target for therapy in the TNBC subtype which currently has the worst prognosis among all breast cancers and remains as the only breast cancer subtype which lacks a targeted therapy.

Morphometric analysis of a triple negative breast cancer cell line in hydrogel and monolayer culture environments

Triple negative breast cancer (TNBC) is a belligerent carcinoma that is unresponsive to targeted receptor therapies. Development of new treatment strategies would benefit from an expanded repertoire of in vitro cell culture systems, such as those that support tridimensional growth in the presence of hydrogel scaffolds. To this end, we established protocols for maintenance of the TNBC cell line HCC70 in monolayer culture and in a commercially available basement membrane matrix hydrogel. We evaluated the general morphology of cells grown in both conditions with light microscopy, and examined their subcellular organization using transmission electron microscopy (TEM). Phase contrast and confocal microscopy showed the prevalence of irregularly shaped flattened cells in monolayer cultures, while cells maintained in hydrogel organized into multi-layered spheroids. A quantitative ultrastructural analysis comparing cells from the two culture conditions revealed that cells that formed spheroids comprised a greater number of mitochondria, autophagic vacuoles and intercellular junctions than their monolayer counterparts, within the equivalent area of sampled tissue. These observations suggest that triple negative breast cancer cells in culture can alter their organelle content, as well as their morphology, in response to their microenvironment. Methods presented here may be useful for those who intend to image cell cultures with TEM, and for investigators who seek to implement diverse in vitro models in the search for therapeutic molecular targets for TNBC.

Breast cancer-associated mitochondrial DNA haplogroup promotes neoplastic growth via ROS-mediated AKT activation

In the last decade, mitochondrial DNA (mtDNA) haplogroups have been associated with the occurrence of breast cancer. However, the underlying mechanism is not known. Combining a case-control study with a large cohort of women from Southern China with breast cancer and functional analyses with trans-mitochondrial technology, we demonstrate that the D5 haplogroup is associated with an increased risk of breast cancer [odds ratio (OR) = 2.789; 95% confidence interval (CI) [1.318, 5.901]; p = 0.007]. Furthermore, mitochondrial respiration, mitochondrial ATP content and membrane potential, were lower in both bone osteosarcoma and breast cancer cell models of cytoplasmic hybrids (cybrids) containing the mtDNA D5 haplogroup than in those with non-D5 haplogroups. Using in vitro and in vivo tumorigenicity assays, we found that cells with the D5 haplogroup were more susceptible to tumorigenesis compared to cells with non-D5 haplogroups. Mechanistically, the D5 haplogroup may promote tumorigenesis at least partially through activation of the v-AKT murine thymoma viral oncogene (AKT) via phosphorylation of threonine 308, which is mediated by increased reactive oxygen species generation in D5 cybrids. Our findings demonstrate that there is decreased mitochondrial function in cells with the D5 haplogroup compared to cells with non-D5 haplogroups, which may be associated with increased neoplastic growth in breast cancer.

Curcumin-loaded nanoliposomes linked to homing peptides for integrin targeting and neuropilin-1-mediated internalization

CONTEXT

Curcumin, a naturally occurring polyphenol, has been extensively studied for its broad-spectrum anticancer effects. The potential benefits are, however, limited due to its poor water solubility and rapid degradation which result in low bioavailability on administration.

OBJECTIVES

This study encapsulates curcumin in nanoliposomes including an integrin-homing peptide combined with a C end R neuropilin-1 targeting motif for targeted delivery and receptor-mediated internalization, respectively.

MATERIALS AND METHODS

The linear GHHNGR (Glycine-Histidine-Histidine-Asparagine-Glycine-Arginine) was synthesized through F-moc chemistry on 2-chlorotrityl chloride resin and conjugated to oleic acid. The lipoyl-peptide units were then co-assembled with lecithin and 0-75 mole % Tween-80 into liposomes. Curcumin was passively entrapped using a film hydration technique and its degradation profile was examined within seven consecutive days. The cytotoxic effects of the curcumin-loaded liposomes were studied on MCF-7 and MDA-MB-468, during 24 h exposure in MTT assay.

RESULTS

The maximum curcumin entrapment (15.5% W/W) and minimum degradation (< 23%) were obtained in a pH switch loading method from 5.7 to 8, in nanoliposomes (< 50 nm) containing oleyl-peptide, lecithin and Tween-80 (1:1:0.75 mole ratio). The oleyl-peptide did not prove any haemolytic activity (< 1.5%) up to 10-fold of its experimental concentration. The curcumin-loaded liposomes displayed significant reduction in the viabilities of MCF-7 (IC₅₀ 3.8 μM) and MDA-MB-468 (IC₅₀ 5.4 μM).

DISCUSSION AND CONCLUSION

This study indicated potential advantages of the peptide-conjugated liposomes in drug transport to the cancer cells. This feature might be an outcome of probable interactions between the targeted nanoliposomes with the integrin and neuropilin-1 receptors.

Application of surface enhanced Raman spectroscopy as a diagnostic system for hypersialylated metastatic cancers

Early diagnosis of metastatic cancers could greatly limit the number of cancer-associated deaths. Aberrant surface expression of sialic acid (hypersialylation) on tumors correlating with metastatic incidence and its involvement in tumorigenesis and progression is widely reported; hence detection of hypersialylated tumors may be an effective strategy to identify metastatic cancers. We herein report on the application of phenylboronic acid-installed PEGylated gold nanoparticles coupled with Toluidine blue O (T/BA-GNPs) as SERS probes to target surface sialic acid (N-acetylneuraminic acid, Neu5Ac). Strong SERS signals from metastatic cancer cell lines (breast cancer; MDA-MB231 and colon cancer; Colon-26) were observed, contrary to non-metastatic MCF-7 cells (breast cancer). The detected SERS signals from various cancer cell lines correlated with their reported metastatic potential, implying that our T/BA-GNP based SERS system was capable of distinguishing the metastaticity of cells based on the surface Neu5Ac density. T/BA-GNP based SERS system could also significantly differentiate between hypersialylated tumor tissues and healthy tissues with high SERS signal to noise ratio, due to plasmon coupling between the specifically aggregated functionalized GNPs. Furthermore, we also confirmed reduction in SERS signals from MDA-MB231 surface upon treatment with our original reactive oxygen species (ROS)-scavenging polymeric micelle, nitroxide-radical containing nanoparticles (RNPs). The ROS-mediated abrogation of sialylation by impairing the activation of NF-κB-sialyltransferase signaling cascade upon RNP treatment was confirmed by expression studies and the T/BA-GNPs based SERS system. The aforementioned findings thus, establish T/BA-GNPs based SERS as a potential cytodiagnostic system to detect hypersialylated metastatic tumors and RNPs as anti-metastatic cancer drug candidates.

Bifunctional Luminomagnetic Rare-Earth Nanorods for High-Contrast Bioimaging Nanoprobes

Nanoparticles exhibiting both magnetic and luminescent properties are need of the hour for many biological applications. A single compound exhibiting this combination of properties is uncommon. Herein, we report a strategy to synthesize a bifunctional luminomagnetic Gd2-xEuxO3 (x = 0.05 to 0.5) nanorod, with a diameter of ~20 nm and length in ~0.6 μm, using hydrothermal method. Gd2O3:Eu(3+) nanorods have been characterized by studying its structural, optical and magnetic properties. The advantage offered by photoluminescent imaging with Gd2O3:Eu(3+) nanorods is that this ultrafine nanorod material exhibits hypersensitive intense red emission (610 nm) with good brightness (quantum yield more than 90%), which is an essential parameter for high-contrast bioimaging, especially for overcoming auto fluorescent background. The utility of luminomagnetic nanorods for biological applications in high-contrast cell imaging capability and cell toxicity to image two human breast cancer cell lines T47D and MDA-MB-231 are also evaluated. Additionally, to understand the significance of shape of the nanostructure, the photoluminescence and paramagnetic characteristic of Gd2O3:Eu(3+) nanorods were compared with the spherical nanoparticles of Gd2O3:Eu(3+).

MicroRNA-Responsive Drug Release System for Selective Fluorescence Imaging and Photodynamic Therapy In Vivo

Photodynamic therapy (PDT) is a noninvasive strategy to treat diseases by light-triggered activation of a photosensitizer (PS). One aim of the recent researches on PDT is to overcome the limitation of conventional PDT by improving selective activation of PS on targeted region. Here, a microRNA (miRNA)-responsive drug activation system is developed which focuses on the role of endogenous miRNA as an internal cancer specific stimulus for initiating drug release in cancer treatment. The present system consists of PS chlorin e6 (Ce6) conjugated to peptide nucleic acid (PNA) having complementary sequence to cancer specific miRNA and dextran coated reduced graphene oxide nanocolloid (Dex-RGON). In the presence of oncogenic miR-21 in cancer cells, Ce6-PNA drug gets hybridized with miR-21, resulting in the release of Ce6-PNA from Dex-RGON and subsequent recovery of Ce6 fluorescence and activation of Ce6 as a photosensitizer under near IR irradiation. It is demonstrated that the Ce6-PNA/Dex-RGON complex shows sequence-specific fluorescence in response to miR-21 and selective cytotoxic effect for tumor growth inhibition. The present study will pave a new way for utilizing PDT in cancer treatment with tightly regulated activation of a photosensitizer by oncogenic miRNA as an internal stimulus to reduce potential risk associated with conventional PDT.

Biomarker-specific conjugated nanopolyplexes for the active coloring of stem-like cancer cells

Stem-like cancer cells possess intrinsic features and their CD44 regulate redox balance in cancer cells to survive under stress conditions. Thus, we have fabricated biomarker-specific conjugated polyplexes using CD44-targetable hyaluronic acid and redox-sensible polyaniline based on a nanoemulsion method. For the most sensitive recognition of the cellular redox at a single nanoparticle scale, a nano-scattering spectrum imaging analyzer system was introduced. The conjugated polyplexes showed a specific targeting ability toward CD44-expressing cancer cells as well as a dramatic change in its color, which depended on the redox potential in the light-scattered images. Therefore, these polyaniline-based conjugated polyplexes as well as analytical processes that include light-scattering imaging and measurements of scattering spectra, clearly establish a systematic method for the detection and monitoring of cancer microenvironments.

Phemindole, a Synthetic Di-indole Derivative Maneuvers the Store Operated Calcium Entry (SOCE) to Induce Potent Anti-Carcinogenic Activity in Human Triple Negative Breast Cancer Cells

Triple-negative breast cancer (TNBC), is a specific subtype of epithelial breast tumors that are immuno-histochemically negative for the protein expression of the estrogen receptor (ER), the progesterone receptor (PR) and lack over expression/gene amplification of HER2. This subtype of breast cancers is highly metastatic, shows poor prognosis and hence represents an important clinical challenge to researchers worldwide. Thus alternative approaches of drug development for TNBC have gained utmost importance in the present times. Dietary indole and its derivatives have gained prominence as anti-cancer agents and new therapeutic approaches are being developed to target them against TNBC. But a major drawback with 3, 3′di Indolyl methane (DIM) is their poor bioavailability and high effective concentration against TNBC. However, the Aryl methyl ring substituted analogs of DIM display interesting anti-cancer activity in breast cancer cells. In the current study we report the synthesis of a novel synthetic aryl methyl ring substituted analog of DIM, named as Phemindole as an effective anti-tumor agent against TNBC cells. Furthermore, we enumerated that Phemindole caused reactive oxygen species mediated mitochondrial-dependent apoptosis in MDAMB-231 cells. Furthermore, Phemindole mediated Store Operated Calcium Entry (SOCE) retardation favored inactivation of STIM1 and henceforth activated ER stress to induce apoptosis in TNBC cells. Simultaneously, Phemindole was also found to restrict the in vitro cell migration through its anti mitotic property and pFAK regulation. Studies extended to ex ovo and in vivo mice models further validated the efficacy of Phemindole. Thus our results cumulatively propose Phemindole as a new chemotherapeutic regime which might be effective to target the deadly aspects of the TNBC.

CDCP1 cleavage is necessary for homodimerization-induced migration of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly aggressive and metastatic form of breast cancer that lacks the estrogen, progesterone and HER2 receptors and is resistant to targeted and hormone therapies. TNBCs express high levels of the transmembrane glycoprotein, complement C1r/C1s, Uegf, Bmp1 (CUB)-domain containing protein 1 (CDCP1), which has been correlated with the aggressiveness and poor prognosis of multiple carcinomas. Full-length CDCP1 (flCDCP1) can be proteolytically cleaved, resulting in a cleaved membrane-bound isoform (cCDCP1). CDCP1 is phosphorylated by Src family kinases in its full-length and cleaved states, which is important for its pro-metastatic signaling. We observed that cCDCP1, compared with flCDCP1, induced a dramatic increase in phosphorylation of the migration-associated proteins: PKCδ, ERK1/2 and p38 mitogen-activated protein kinase in HEK 293T. In addition, only cCDCP1 induced migration of HEK 293T cells and rescued migration of the TNBC cell lines expressing short hairpin RNA against CDCP1. Importantly, we found that only cCDCP1 is capable of dimerization, which can be blocked by expression of the extracellular portion of cCDCP1 (ECC), indicating that dimerization occurs through CDCP1's ectodomain. We found that ECC inhibited phosphorylation of PKCδ and migration of TNBC cells in two-dimensional culture. Furthermore, ECC decreased cell invasiveness, inhibited proliferation and stimulated apoptosis of TNBC cells in three-dimensional culture, indicating that the cCDCP1 dimer is an important contributor to TNBC aggressiveness. These studies have important implications for the development of a therapeutic to block CDCP1 activity and TNBC metastasis.

Mitochondrial DNA variants can mediate methylation status of inflammation, angiogenesis and signaling genes

Mitochondrial (mt) DNA can be classified into haplogroups representing different geographic and/or racial origins of populations. The H haplogroup is protective against age-related macular degeneration (AMD), while the J haplogroup is high risk for AMD. In the present study, we performed comparison analyses of human retinal cell cybrids, which possess identical nuclei, but mtDNA from subjects with either the H or J haplogroups, and demonstrate differences in total global methylation, and expression patterns for two genes related to acetylation and five genes related to methylation. Analyses revealed that untreated-H and -J cybrids have different expression levels for nuclear genes (CFH, EFEMP1, VEGFA and NFkB2). However, expression levels for these genes become equivalent after treatment with a methylation inhibitor, 5-aza-2'-deoxycytidine. Moreover, sequencing of the entire mtDNA suggests that differences in epigenetic status found in cybrids are likely due to single nucleotide polymorphisms (SNPs) within the haplogroup profiles rather than rare variants or private SNPs. In conclusion, our findings indicate that mtDNA variants can mediate methylation profiles and transcription for inflammation, angiogenesis and various signaling pathways, which are important in several common diseases.

Casein kinase 2 prevents mesenchymal transformation by maintaining Foxc2 in the cytoplasm

Nuclear Foxc2 is a transcriptional regulator of mesenchymal transformation during developmental epithelial-mesenchymal transition (EMT) and has been associated with EMT in malignant epithelia. Our laboratory has shown that in normal epithelial cells Foxc2 is maintained in the cytoplasm where it promotes an epithelial phenotype. The Foxc2 amino terminus has a consensus casein kinase 2 (CK2) phosphorylation site at serine 124, and we now show that CK2 associates with Foxc2 and phosphorylates this site in vitro. Knockdown or inhibition of the CK2α/α' kinase subunit in epithelial cells causes de novo accumulation of Foxc2 in the nucleus. Mutation of serine 124 to leucine promotes constitutive nuclear localization of Foxc2 and expression of mesenchymal genes, whereas an S124D phosphomimetic leads to constitutive cytoplasmic localization and epithelial maintenance. In malignant breast cancer cells, the CK2β regulatory subunit is downregulated and FOXC2 is found in the nucleus, correlating with an increase in α-smooth muscle actin (SMA) expression. Restoration of CK2β expression in these cells results in cytoplasmic localization of Foxc2, decreased α-SMA expression and reduced cell migration and invasion. In contrast, knockdown of CK2β in normal breast epithelial cells leads to FOXC2 nuclear localization, decreased E-cadherin expression, increased α-SMA and vimentin expression, and enhanced cell migration and invasion. Based on these findings, we propose that Foxc2 is functionally maintained in the cytoplasm of normal epithelial cells by CK2α/α'-mediated phosphorylation at serine 124, which is dependent on proper targeting of the holoenzyme via the CK2β regulatory subunit.

Mitochondria directly donate their membrane to form autophagosomes during a novel mechanism of parkin-associated mitophagy

Background

Autophagy (macroautophagy), a cellular process of “self-eating”, segregates damaged/aged organelles into vesicles, fuses with lysosomes, and enables recycling of the digested materials. The precise origin(s) of the autophagosome membrane is unclear and remains a critical but unanswered question. Endoplasmic reticulum, mitochondria, Golgi complex, and the plasma membrane have been proposed as the source of autophagosomal membranes.

Findings

Using electron microscopy, immunogold labeling techniques, confocal microscopy, and flow cytometry we show that mitochondria can directly donate their membrane material to form autophagosomes. We expand upon earlier studies to show that mitochondria donate their membranes to form autophagosomes during basal and drug-induced autophagy. Moreover, electron microscopy and immunogold labeling studies show the first physical evidence of mitochondria forming continuous structures with LC3-labeled autophagosomes. The mitochondria forming these structures also stain positive for parkin, indicating that these mitochondrial-formed autophagosomes represent a novel mechanism of parkin-associated mitophagy.

Conclusions

With the on-going debate regarding autophagosomal membrane origin, this report demonstrates that mitochondria can donate membrane materials to form autophagosomes. These structures may also represent a novel form of mitophagy where the mitochondria contribute to the formation of autophagosomes. This novel form of parkin-associated mitophagy may be a more efficient bio-energetic process compared with de novo biosynthesis of a new membrane, particularly if the membrane is obtained, at least partly, from the organelle being targeted for later degradation in the mature autolysosome.

IBP-mediated suppression of autophagy promotes growth and metastasis of breast cancer cells via activating mTORC2/Akt/FOXO3a signaling pathway

Interferon regulatory factor-4 binding protein (IBP) is a novel upstream activator of Rho GTPases. Our previous studies have shown that ectopic expression of IBP was correlated with malignant behaviors of human breast cancer cells, and invasive human breast cancer had high expression of IBP that promoted the proliferation of these cells. However, it remains unknown whether autophagy inhibition contributes to IBP-mediated tumorigenesis. In this study, we for the first time, reported that upregulation of IBP expression significantly suppressed the autophagy of breast cancer cells, and downregulation of IBP expression markedly induced autophagy of these cells. Further investigation revealed that IBP effectively counteracted autophagy by directly activating mammalian target of rapamycin complex 2 (mTORC2) and upregulating phosphorylation of Akt on ser473 and FOXO3a on Thr32. Moreover, IBP-mediated suppression of autophagy was dependent on mTORC2/Akt/FOXO3a signaling pathway. Finally, our results demonstrated that IBP-mediated breast cancer cell growth in vitro and in vivo was strongly correlated with suppression of mTORC2-dependent autophagy. These findings suggest that the anti-autophagic property of IBP has an important role in IBP-mediated tumorigenesis, and IBP may serve as an attractive target for treatment of breast cancer.

Aberrant expression of Beclin-1 and LC3 correlates with poor prognosis of human hypopharyngeal squamous cell carcinoma

Background

Beclin-1, a key regulator of autophagy. Microtubule-associated protein 1 light chain 3 (LC3), is involved in autophagsome formation during autophagy. The autophagic genes beclin-1 and LC3 paly an important role in the development and progression of tumor. This study was designed to investigate the expression of beclin-1 and LC3 and to clarify their clinical significance in hypopharyngeal squamous cell carcinoma (HSCC).

Methods

Eighty-two surgical hypopharyngeal squamous cell carcinoma specimens and fifty-four adjacent non-cancerous mucosal epithelial tissues were obtained. Beclin-1 and LC3-II expression was examined by immunohistochemistry, real-time RT-PCR and Western blotting assays. Correlations with patient clinical characteristics and overall survival were evaluated.

Results

Beclin-1 was positively expressed in 42.7% (35/82) of HSCC specimens (adjacent non-cancerous tissues, 79.6%, 43/54; P<0.0001). Furthermore, 41.5% (34/82) of HSCC specimens exhibited high LC3 immunoreactivity (adjacent non-cancerous tissues, 74.1%, 40/54; P=0.0002). Beclin-1 and LC3-II mRNA transcript levels were significantly lower in HSCCs than in paired non-cancerous tissues (P<0.0001, P=0.0001, respectively). Similarly, western blotting assays showed that beclin-1 and LC3-II were markedly decreased in HSCCs (P=0.02, P=0.004, respectively). A positive correlation was observed between the mRNA transcript levels of beclin-1 and LC3-II in HSCCs (r=0.51, P<0.0001; 95%CI: 0.273 to 0.689). Beclin-1 and LC3 expression were significantly correlated with T categories, differentiation and lymph node metastasis. Negative beclin-1 immuoreactivity and low LC3 expression were associated with poorer overall survival in HSCC patients (P<0.0001, P=0.0145, respectively). Multivariate analysis revealed that beclin-1 was an independent prognositic factor for overall survival.

Conclusion

Beclin-1 and LC3-II are downregulated in HSCCs and their aberrant expression correlates with poor prognosis of HSCCs.

Crosstalk from non-cancerous mitochondria can inhibit tumor properties of metastatic cells by suppressing oncogenic pathways

Mitochondrial-nucleus cross talks and mitochondrial retrograde regulation can play a significant role in cellular properties. Transmitochondrial cybrid systems (cybrids) are an excellent tool to study specific effects of altered mitochondria under a defined nuclear background. The majority of the studies using the cybrid model focused on the significance of specific mitochondrial DNA variations in mitochondrial function or tumor properties. However, most of these variants are benign polymorphisms without known functional significance. From an objective of rectifying mitochondrial defects in cancer cells and to establish mitochondria as a potential anticancer drug target, understanding the role of functional mitochondria in reversing oncogenic properties under a cancer nuclear background is very important. Here we analyzed the potential reversal of oncogenic properties of a highly metastatic cell line with the introduction of non-cancerous mitochondria. Cybrids were established by fusing the mitochondria DNA depleted 143B TK- ρ0 cells from an aggressive osteosarcoma cell line with mitochondria from benign breast epithelial cell line MCF10A, moderately metastatic breast cancer cell line MDA-MB-468 and 143B cells. In spite of the uniform cancerous nuclear background, as observed with the mitochondria donor cells, cybrids with benign mitochondria showed high mitochondrial functional properties including increased ATP synthesis, oxygen consumption and respiratory chain activities compared to cybrids with cancerous mitochondria. Interestingly, benign mitochondria could reverse different oncogenic characteristics of 143B TK^- cell including cell proliferation, viability under hypoxic condition, anti-apoptotic properties, resistance to anti-cancer drug, invasion, and colony formation in soft agar, and in vivo tumor growth in nude mice. Microarray analysis suggested that several oncogenic pathways observed in cybrids with cancer mitochondria are inhibited in cybrids with non-cancerous mitochondria. These results suggest the critical oncogenic regulation by mitochondrial-nuclear cross talk and highlights rectifying mitochondrial functional properties as a promising target in cancer therapy.

Targeting proteomics to investigate metastasis-associated mitochondrial proteins

Mitochondria are essential organelles in eukaryotic cells and are responsible for regulating energy metabolism, ROS production, and cell survival. Recently, various cellular pathogeneses, including tumorigenesis and metastasis, have been reported to be associated with mitochondrial homeostasis. Consequently, exploiting the correlation between dysfunctional mitochondria and tumor progression has been implicated in the understanding of tumorigenesis, tumor metastasis, and chemoresistance, along with novel strategies to develop cancer therapeutics. To comprehensively understand the role of the mitochondria in cancer metastasis, it is necessary to resolve thousands of mitochondrial proteins and their post-translational modifications with high-throughput global assessments. We introduce mitochondrial proteomic strategies in this review and a discussion on their recent findings related to cancer metastasis. Additionally, the mitochondrial respiratory chain is believed to be a major site for ROS production, and elevated ROS is likely a key source to trigger dysfunctional mitochondria and impaired mitochondrial metabolism that subsequently contribute to the development of cancer progression. Equipment-based metabolomic analysis now allows the monitoring of disease progression and diagnosis. These newly emerging techniques, including proteomics, redox-proteomics, and metabolomics, are described in this review.

Rapid cytotoxicity of antimicrobial peptide tempoprin-1CEa in breast cancer cells through membrane destruction and intracellular calcium mechanism

Temporin-1CEa is an antimicrobial peptide isolated from the skin secretions of the Chinese brown frog (Rana chensinensis). We have previously reported the rapid and broad-spectrum anticancer activity of temporin-1CEa in vitro. However, the detailed mechanisms for temporin-1CEa-induced cancer cell death are still weakly understood. In the present study, the mechanisms of temporin-1CEa-induced rapid cytotoxicity on two human breast cancer cell lines, MDA-MB-231 and MCF-7, were investigated. The MTT assay and the LDH leakage assay indicated that one-hour of incubation with temporin-1CEa led to cytotoxicity in a dose-dependent manner. The morphological observation using electronic microscopes suggested that one-hour exposure of temporin-1CEa resulted in profound morphological changes in both MDA-MB-231 and MCF-7 cells. The membrane-disrupting property of temporin-1CEa was further characterized by induction of cell-surface exposure of phosphatidylserine, elevation of plasma membrane permeability and rapid depolarization of transmembrane potential. Moreover, temporin-1CEa evoked intracellular calcium ion and reactive oxygen species (ROS) elevations as well as collapse of mitochondrial membrane potential (Δφm). In summary, the present study indicates that temporin-1CEa triggers rapid cell death in breast cancer cells. This rapid cytotoxic activity might be mediated by both membrane destruction and intracellular calcium mechanism.

Autophagy in stem cells

Autophagy is a highly conserved cellular process by which cytoplasmic components are sequestered in autophagosomes and delivered to lysosomes for degradation. As a major intracellular degradation and recycling pathway, autophagy is crucial for maintaining cellular homeostasis as well as remodeling during normal development, and dysfunctions in autophagy have been associated with a variety of pathologies including cancer, inflammatory bowel disease and neurodegenerative disease. Stem cells are unique in their ability to self-renew and differentiate into various cells in the body, which are important in development, tissue renewal and a range of disease processes. Therefore, it is predicted that autophagy would be crucial for the quality control mechanisms and maintenance of cellular homeostasis in various stem cells given their relatively long life in the organisms. In contrast to the extensive body of knowledge available for somatic cells, the role of autophagy in the maintenance and function of stem cells is only beginning to be revealed as a result of recent studies. Here we provide a comprehensive review of the current understanding of the mechanisms and regulation of autophagy in embryonic stem cells, several tissue stem cells (particularly hematopoietic stem cells), as well as a number of cancer stem cells. We discuss how recent studies of different knockout mice models have defined the roles of various autophagy genes and related pathways in the regulation of the maintenance, expansion and differentiation of various stem cells. We also highlight the many unanswered questions that will help to drive further research at the intersection of autophagy and stem cell biology in the near future.

Mitochondrial complex I activity and NAD+/NADH balance regulate breast cancer progression

Despite advances in clinical therapy, metastasis remains the leading cause of death in breast cancer patients. Mutations in mitochondrial DNA, including those affecting complex I and oxidative phosphorylation, are found in breast tumors and could facilitate metastasis. This study identifies mitochondrial complex I as critical for defining an aggressive phenotype in breast cancer cells. Specific enhancement of mitochondrial complex I activity inhibited tumor growth and metastasis through regulation of the tumor cell NAD+/NADH redox balance, mTORC1 activity, and autophagy. Conversely, nonlethal reduction of NAD+ levels by interfering with nicotinamide phosphoribosyltransferase expression rendered tumor cells more aggressive and increased metastasis. The results translate into a new therapeutic strategy: enhancement of the NAD+/NADH balance through treatment with NAD+ precursors inhibited metastasis in xenograft models, increased animal survival, and strongly interfered with oncogene-driven breast cancer progression in the MMTV-PyMT mouse model. Thus, aberration in mitochondrial complex I NADH dehydrogenase activity can profoundly enhance the aggressiveness of human breast cancer cells, while therapeutic normalization of the NAD+/NADH balance can inhibit metastasis and prevent disease progression.

Highly luminescent-paramagnetic nanophosphor probes for in vitro high-contrast imaging of human breast cancer cells

Highly luminescent-paramagnetic nanophosphors have a seminal role in biotechnology and biomedical research due to their potential applications in biolabeling, bioimaging, and drug delivery. Herein, the synthesis of high-quality, ultrafine, europium-doped yttrium oxide nanophosphors (Y(1.9)O(3):Eu(0.1)(3+)) using a modified sol-gel technique is reported and in vitro fluorescence imaging studies are demonstrated in human breast cancer cells. These highly luminescent nanophosphors with an average particle size of ≈6 nm provide high-contrast optical imaging and decreased light scattering. In vitro cellular uptake is shown by fluorescence microscopy, which visualizes the characteristic intense hypersensitive red emission of Eu(3+) peaking at 610 nm ((5)D(0)-(7)F(2)) upon 246 nm UV light excitation. No apparent cytotoxicity is observed. Subsequently, time-resolved emission spectroscopy and SQUID magnetometry measurements demonstrate a photoluminescence decay time in milliseconds and paramagnetic behavior, which assure applications of the nanophosphors in biomedical studies.

Mitochondrial dynamics is affected by 17β-estradiol in the MCF-7 breast cancer cell line. Effects on fusion and fission related genes

Mitochondrial dynamics, specifically fusion and fission processes, maintain mitochondria integrity and function, yet at this time, effect of estrogens on fusion and fission in breast cancer cell lines has not been studied. The aim of this study was to characterize the effect of 17β-estradiol on fusion and fission-related genes, as well as on mitochondria proliferation and function. We used MCF-7 breast cancer cell line, which is estrogen sensitive (estrogen receptor positive). Cells were grown in Dulbecco's modified Eagle medium charcoal-stripped fetal bovine serum and treated with 1nM of 17β-estradiol and with/without 100nM of ICI 182,780, a drug that caused rapid degradation of estrogen receptor. mRNA levels of fusion (mfn1, mfn2, opa1) and fission-related genes (drp1 and fis1) were examined by RT-PCR, cardiolipin content by N-acridyl-orange fluorescence and oxidative phosphorylation protein levels, as well as, the major fusion and fission related protein levels, by Western blot. mRNA expression of fusion-related genes increased after 17β-estradiol-treatment for 4h; however fis1 fission-related gene expression decreased. All these effects were not found in cells pre-treated with ICI 182,780, save for the changes in mfn-1, conferring them the effects of 17β-estradiol to estrogen receptor. The changes in protein levels were less prominent, but in the same way, than in mRNA levels, showing an increase in Mfn1 and Mfn2, as well as in Drp1, but there was no change in Fis1 protein levels. Mitochondrial biogenesis was also affected by 17β-estradiol, showing an increase in mtDNA but with no change in N-acridyl-orange fluorescence. On the whole, our results suggest an imbalance in the fusion/fission ratio, with a high fusion by 17β-estradiol-estrogen receptor action, which can affect to mitochondrial biogenesis, concretely in mitochondria proliferation. According to this information, 17β-estradiol would modify mitochondrial dynamics, biogenesis and metabolism, and thus compromise the normal development and function of mitochondria in cancer affected tissues.

Glucose-regulated protein 78 controls cross-talk between apoptosis and autophagy to determine antiestrogen responsiveness

While more than 70% of breast cancers express estrogen receptor-α (ER+), endocrine therapies targeting these receptors often fail. The molecular mechanisms that underlie treatment resistance remain unclear. We investigated the potential role of glucose-regulated protein 78 (GRP78) in mediating estrogen resistance. Human breast tumors showed increased GRP78 expression when compared with normal breast tissues. However, GRP78 expression was reduced in ER+ breast tumors compared with HER2-amplifed or triple-negative breast tumors. ER+ antiestrogen-resistant cells and ER+ tumors with an acquired resistant antiestrogen phenotype were both shown to overexpress GRP78, which was not observed in cases of de novo resistance. Knockdown of GRP78 restored antiestrogen sensitivity in resistant cells, and overexpression of GRP78 promoted resistance in sensitive cells. Mechanistically, GRP78 integrated multiple cellular signaling pathways to inhibit apoptosis and stimulate prosurvival autophagy, which was dependent on TSC2/AMPK-mediated mTOR inhibition but not on beclin-1. Inhibition of autophagy prevented GRP78-mediated endocrine resistance, whereas caspase inhibition abrogated the resensitization that resulted from GRP78 loss. Simultaneous knockdown of GRP78 and beclin-1 synergistically restored antiestrogen sensitivity in resistant cells. Together, our findings reveal a novel role for GRP78 in the integration of cellular signaling pathways including the unfolded protein response, apoptosis, and autophagy to determine cell fate in response to antiestrogen therapy.

Novel Insights into the Interplay between Apoptosis and Autophagy

For several decades, apoptosis has taken center stage as the principal mechanism of programmed cell death (type I cell death) in mammalian tissues. Autophagic cell death (type II) is characterized by the massive accumulation of autophagic vacuoles in the cytoplasm of cells. The autophagic process is activated as an adaptive response to a variety of extracellular and intracellular stresses, including nutrient deprivation, hormonal or therapeutic treatment, pathogenic infection, aggregated and misfolded proteins, and damaged organelles. Increasing evidence indicates that autophagy is associated with a number of pathological processes, including cancer. The regulation of autophagy in cancer cells is complex since it can enhance cancer cell survival in response to certain stresses, while it can also act to suppress the initiation of cancer growth. This paper focused on recent advances regarding autophagy in cancer and the techniques currently available to manipulate autophagy.

Autophagy and endocrine resistance in breast cancer

The American Cancer Society estimates that over 200,000 new breast cancer cases are diagnosed annually in the USA alone. Of these cases, the majority are invasive breast cancers and almost 70% are estrogen receptor-α positive. Therapies targeting the estrogen receptor-α are widely applied and include selective estrogen receptor modulators such as tamoxifen, a selective estrogen receptor downregulator such as Fulvestrant (Faslodex; FAS, ICI 182,780), or one of the third-generation aromatase inhibitors including letrozole or anastrozole. While these treatments reduce breast cancer mortality, many estrogen receptor-α-positive tumors eventually recur, highlighting the clinical significance of endocrine therapy resistance. The signaling leading to endocrine therapy resistance is poorly understood; however, preclinical studies have established an important role for autophagy in the acquired resistance phenotype. Autophagy is a cellular degradation process initiated in response to stress or nutrient deprivation, which attempts to restore metabolic homeostasis through the catabolic lysis of aggregated proteins, unfolded/misfolded proteins or damaged subcellular organelles. The duality of autophagy, which can be either pro-survival or pro-death, is well known. However, in the context of endocrine therapy resistance in breast cancer, the inhibition of autophagy can potentiate resensitization of previously antiestrogen resistant breast cancer cells. In this article, we discuss the complex and occasionally contradictory roles of autophagy in cancer and in resistance to endocrine therapies in breast cancer.

[Experience in the management of children with diabetes mellitus]

Aerobic glycolysis, also referred to as the Warburg effect, has been regarded as the dominant metabolic phenotype in cancer cells for a long time. More recently, it has been shown that mitochondria in most tumors are not defective in their ability to carry out oxidative phosphorylation (OXPHOS). Instead, in highly aggressive cancer cells, mitochondrial energy pathways are reprogrammed to meet the challenges of high energy demand, better utilization of available fuels and macromolecular synthesis for rapid cell division and migration. Mitochondrial energy reprogramming is also involved in the regulation of oncogenic pathways via mitochondria-to-nucleus retrograde signaling and post-translational modification of oncoproteins. In addition, neoplastic mitochondria can engage in crosstalk with the tumor microenvironment. For example, signals from cancer-associated fibroblasts can drive tumor mitochondria to utilize OXPHOS, a process known as the reverse Warburg effect. Emerging evidence shows that cancer cells can acquire a hybrid glycolysis/OXPHOS phenotype in which both glycolysis and OXPHOS can be utilized for energy production and biomass synthesis. The hybrid glycolysis/OXPHOS phenotype facilitates metabolic plasticity of cancer cells and may be specifically associated with metastasis and therapy-resistance. Moreover, cancer cells can switch their metabolism phenotypes in response to external stimuli for better survival. Taking into account the metabolic heterogeneity and plasticity of cancer cells, therapies targeting cancer metabolic dependency in principle can be made more effective.