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Overcoming multidrug resistance via photodestruction of ABCG2-rich extracellular vesicles sequestering photosensitive chemotherapeutics.

ABSTRACT: Multidrug resistance (MDR) remains a dominant impediment to curative cancer chemotherapy. Efflux transporters of the ATP-binding cassette (ABC) superfamily including ABCG2, ABCB1 and ABCC1 mediate MDR to multiple structurally and functionally distinct antitumor agents. Recently we identified a novel mechanism of MDR in which ABCG2-rich extracellular vesicles (EVs) form in between attached neighbor breast cancer cells and highly concentrate various chemotherapeutics in an ABCG2-dependent manner, thereby sequestering them away from their intracellular targets. Hence, development of novel strategies to overcome MDR modalities is a major goal of cancer research. Towards this end, we here developed a novel approach to selectively target and kill MDR cancer cells. We show that illumination of EVs that accumulated photosensitive cytotoxic drugs including imidazoacridinones (IAs) and topotecan resulted in intravesicular formation of reactive oxygen species (ROS) and severe damage to the EVs membrane that is shared by EVs-forming cells, thereby leading to tumor cell lysis and the overcoming of MDR. Furthermore, consistent with the weak base nature of IAs, MDR cells that are devoid of EVs but contained an increased number of lysosomes, highly accumulated IAs in lysosomes and upon photosensitization were efficiently killed via ROS-dependent lysosomal rupture. Combining targeted lysis of IAs-loaded EVs and lysosomes elicited a synergistic cytotoxic effect resulting in MDR reversal. In contrast, topotecan, a bona fide transport substrate of ABCG2, accumulated exclusively in EVs of MDR cells but was neither detected in lysosomes of normal breast epithelial cells nor in non-MDR breast cancer cells. This exclusive accumulation in EVs enhanced the selectivity of the cytotoxic effect exerted by photodynamic therapy to MDR cells without harming normal cells. Moreover, lysosomal alkalinization with bafilomycin A1 abrogated lysosomal accumulation of IAs, consequently preventing lysosomal photodestruction of normal breast epithelial cells. Thus, MDR modalities including ABCG2-dependent drug sequestration within EVs can be rationally converted to a pharmacologically lethal Trojan horse to selectively eradicate MDR cancer cells.

SUBMITTER: Goler-Baron V

PROVIDER: S-EPMC3329466 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Overcoming multidrug resistance via photodestruction of ABCG2-rich extracellular vesicles sequestering photosensitive chemotherapeutics.

Goler-Baron Vicky V Assaraf Yehuda G YG

PloS one 20120418 4

Multidrug resistance (MDR) remains a dominant impediment to curative cancer chemotherapy. Efflux transporters of the ATP-binding cassette (ABC) superfamily including ABCG2, ABCB1 and ABCC1 mediate MDR to multiple structurally and functionally distinct antitumor agents. Recently we identified a novel mechanism of MDR in which ABCG2-rich extracellular vesicles (EVs) form in between attached neighbor breast cancer cells and highly concentrate various chemotherapeutics in an ABCG2-dependent manner, ...[more]

PMID: 22530032

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Project description:Multidrug resistance (MDR) is a major impediment to curative cancer chemotherapy. The ATP-Binding Cassette transporters ABCG2, ABCB1 and ABCC2 form a unique defense network against multiple structurally and functionally distinct chemotherapeutics, thereby resulting in MDR. Thus, deciphering novel mechanisms of MDR and their overcoming is a major goal of cancer research. Recently we have shown that overexpression of ABCG2 in the membrane of novel extracellular vesicles (EVs) in breast cancer cells results in mitoxantrone resistance due to its dramatic sequestration in EVs. However, nothing is known about EVs structure, biogenesis and their ability to concentrate multiple antitumor agents. To this end, we here found that EVs are structural and functional homologues of bile canaliculi, are apically localized, sealed structures reinforced by an actin-based cytoskeleton and secluded from the extracellular milieu by the tight junction proteins occludin and ZO-1. Apart from ABCG2, ABCB1 and ABCC2 were also selectively targeted to the membrane of EVs. Moreover, Ezrin-Radixin-Moesin protein complex selectively localized to the border of the EVs membrane, suggesting a key role for the tethering of MDR pumps to the actin cytoskeleton. The ability of EVs to concentrate and sequester different antitumor drugs was also explored. Taking advantage of the endogenous fluorescence of anticancer drugs, we found that EVs-forming breast cancer cells display high level resistance to topotecan, imidazoacridinones and methotrexate via efficient intravesicular drug concentration hence sequestering them away from their cellular targets. Thus, we identified a new modality of anticancer drug compartmentalization and resistance in which multiple chemotherapeutics are actively pumped from the cytoplasm and highly concentrated within the lumen of EVs via a network of MDR transporters differentially targeted to the EVs membrane. We propose a composite model for the structure and function of MDR pump-rich EVs in cancer cells and their ability to confer multiple anticancer drug resistance.

Project description:Most cancer-related deaths are caused by distant metastases, which are tumour cells that have escaped from a primary tumour and passed into the bloodstream to colonize a new organ. In this context, communication between tumour and stromal cells is essential. Indeed, tumor cells interact with cells in the tumor microenvironment and are able to modify them to their advantage. Both extracellular vesicles (EVs) and exosomes are heterogeneous populations of small vesicles present in the tumor microenvironment and in body fluids that have recently emerged as powerful mediators involved in this communication and their transport in fluids. Tumor cells release large quantities of exosomes containing tumor markers, which can then spread to distant locations. The exosomes are of endosomal origin. They are composed of proteins, lipids, RNA and DNA, and they circulate in the bloodstream. They can be internalized by specific distant cells and thus deliver a functional message. It has recently been shown that tumor exosomes containing pro-metastatic factors form pre-metastatic niches, before the tumor cells actually arrive, while determining the metastatic organotropism of tumors. These properties are now opening up new avenues of research in tumor biomarkers. In recent years, several studies have highlighted different markers contained specifically in exosomes derived from cancer cells. Consequently, exosomes are considered as potential reservoirs of tumor biomarkers that could be clinically useful for the non-invasive diagnosis of cancer, with the advantage of being performed by liquid biopsy. The study of microRNA (miRNA) is of particular interest. Indeed, miRNAs are small non-coding RNAs (between 21 and 25 nucleotides) involved in the regulation of gene expression and which are frequently deregulated in cancer. Several studies underline that the variation of free miRNAs in the blood is correlated with the progression of the disease, particularly in colon cancer. However, the stability of free miRNAs is controversial. Therefore, exosomes represent a very advantageous means of transporting miRNAs in the blood, as they are able to protect miRNAs from degradation by RNAase. The hypothesis of the project is that circulating exosomes derived from tumours contain markers including specific miRNAs that could be used as biomarkers of early prognosis (survival and progression), easily measured in blood samples from patients with colon cancer. But other molecules contained in exosomes could also be of interest.

Dataset Information

Overcoming multidrug resistance via photodestruction of ABCG2-rich extracellular vesicles sequestering photosensitive chemotherapeutics.

Publications

Overcoming multidrug resistance via photodestruction of ABCG2-rich extracellular vesicles sequestering photosensitive chemotherapeutics.

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