Mitochondria Transfer by Platelet-Derived Microparticles Regulates Breast Cancer Bioenergetic States and Malignant Features.

An increasing number of studies show that platelets as well as platelet-derived microparticles (PMP) play significant roles in cancer malignancy and disease progression. Particularly, PMPs have the capacity to interact and internalize within target cells resulting in the transfer of their bioactive cargo, which can modulate the signaling and activation processes of recipient cells. We recently identified a new subpopulation of these vesicles (termed mitoMPs), which contain functional mitochondria. Given the predominant role of mitochondria in cancer cell metabolism and disease progression, we set out to investigate the impact of mitoMPs on breast cancer metabolic reprograming and phenotypic processes leading to malignancy. Interestingly, we observed that recipient cell permeability to PMP internalization varied among the breast cancer cell types evaluated in our study. Specifically, cells permissive to mitoMPs acquire mitochondrial-dependent functions, which stimulate increased cellular oxygen consumption rates and intracellular ATP levels. In addition, cancer cells co-incubated with PMPs display enhanced malignant features in terms of migration and invasion. Most importantly, the cancer aggressive processes and notable metabolic plasticity induced by PMPs were highly dependent on the functional status of the mitoMP-packaged mitochondria. These findings characterize a new mechanism by which breast cancer cells acquire foreign mitochondria resulting in the gain of metabolic processes and malignant features. A better understanding of these mechanisms may provide therapeutic opportunities through PMP blockade to deprive cancer cells from resources vital in disease progression. IMPLICATIONS: We show that the transfer of foreign mitochondria by microparticles modulates recipient cancer cell metabolic plasticity, leading to greater malignant processes.

Molecular characterization of the anticancer properties associated with bee venom and its components in glioblastoma multiforme.

Glioblastoma multiforme (GBM) is a frequent form of malignant glioma. Strategic therapeutic approaches to treat this type of brain tumor currently involves a combination of surgery, radiotherapy and chemotherapy. Nevertheless, survival of GBM patients remains in the 12-15 months range following diagnosis. Development of novel therapeutic approaches for this malignancy is therefore of utmost importance. Interestingly, bee venom and its components have shown promising anti-cancer activities in various types of cancer even though information pertaining to GBMs have been limited. The current work was thus undertaken to better characterize the anti-cancer properties of bee venom and its components in Hs683, T98G and U373 human glioma cells. MTT-based cell viability assays revealed IC50 values of 7.12, 15.35 and 7.60 µg/mL for cell lines Hs683, T98G and U373 treated with bee venom, respectively. Furthermore, melittin treatment of these cell lines resulted in IC50 values of 7.77, 31.53 and 12.34 µg/mL, respectively. Cell viability assessment by flow cytometry analysis confirmed signs of late apoptosis and necrosis after only 1 h of treatment with either bee venom or melittin in all three cell lines. Immunoblotting-based quantification of apoptotic markers demonstrated increased expression of Bak and Bax, while Caspsase-3 levels were significantly lower when compared to control cells. Quantification by qRT-PCR showed increased expression levels of long non-coding RNAs RP11-838N2.4 and XIST in glioma cells treated with either bee venom or melittin. Overall, this study provides preliminary insight on molecular mechanisms via which bee venom and its main components can impact viability of glioma cells and warrants further investigation of its anticancer potential in gliomas.

Respective contribution of cytosolic phospholipase A2α and secreted phospholipase A2 IIA to inflammation and eicosanoid production in arthritis.

Phospholipase A2s (PLA2) play a key role in generation of eicosanoids. Cytosolic PLA2α (cPLA2α) is constitutively expressed in most cells, whereas IIA secreted PLA2 (sPLA2-IIA) is induced during inflammation and is present at high levels in the synovial fluid of rheumatoid arthritis patients. In mice, both cPLA2α and sPLA2-IIA have been implicated in autoimmune arthritis; however, the respective contribution of these two enzymes to the pathogenesis and production of eicosanoids is unknown. We evaluated the respective role of cPLA2α and sPLA2-IIA with regard to arthritis and eicosanoid profile in an in vivo model of arthritis. While arthritis was most severe in mice expressing both enzymes, it was abolished when both cPLA2α and sPLA2-IIA were lacking. cPLA2α played a dominant role in the severity of arthritis, although sPLA2-IIA sufficed to significantly contribute to the disease. Several eicosanoids were modulated during the course of arthritis and numerous species involved sPLA2-IIA expression. This study confirms the critical role of PLA2s in arthritis and unveils the distinct contribution of cPLA2α and sPLA2-IIA to the eicosanoid profile in arthritis.

Platelet microparticles are internalized in neutrophils via the concerted activity of 12-lipoxygenase and secreted phospholipase A2-IIA.

Platelets are anucleated blood elements highly potent at generating extracellular vesicles (EVs) called microparticles (MPs). Whereas EVs are accepted as an important means of intercellular communication, the mechanisms underlying platelet MP internalization in recipient cells are poorly understood. Our lipidomic analyses identified 12(S)-hydroxyeicosatetranoic acid [12(S)-HETE] as the predominant eicosanoid generated by MPs. Mechanistically, 12(S)-HETE is produced through the concerted activity of secreted phospholipase A2 IIA (sPLA2-IIA), present in inflammatory fluids, and platelet-type 12-lipoxygenase (12-LO), expressed by platelet MPs. Platelet MPs convey an elaborate set of transcription factors and nucleic acids, and contain mitochondria. We observed that MPs and their cargo are internalized by activated neutrophils in the endomembrane system via 12(S)-HETE. Platelet MPs are found inside neutrophils isolated from the joints of arthritic patients, and are found in neutrophils only in the presence of sPLA2-IIA and 12-LO in an in vivo model of autoimmune inflammatory arthritis. Using a combination of genetically modified mice, we show that the coordinated action of sPLA2-IIA and 12-LO promotes inflammatory arthritis. These findings identify 12(S)-HETE as a trigger of platelet MP internalization by neutrophils, a mechanism highly relevant to inflammatory processes. Because sPLA2-IIA is induced during inflammation, and 12-LO expression is restricted mainly to platelets, these observations demonstrate that platelet MPs promote their internalization in recipient cells through highly regulated mechanisms.