Taylor, J, Azimi, I, Monteith, G & Bebawy, M 2020, 'Ca2+ mediates extracellular vesicle biogenesis through alternate pathways in malignancy.', Journal of extracellular vesicles, vol. 9, no. 1.View/Download from: Publisher's site
Extracellular vesicles (EVs) are small extracellular membrane vesicles that serve as important intercellular signalling intermediaries in both malignant and non-malignant cells. For EVs formed by the plasma membrane, their biogenesis is characterized by an increase in intracellular calcium followed by successive membrane and cytoskeletal changes. EV production is significantly higher in malignant cells relative to non-malignant cells and previous work suggests this is dependent on increased calcium mobilization and activity of calpain. However, differences in calcium-signalling pathways in the context of malignant and non-malignant EV biogenesis remain unexplored. Here, we demonstrate vesiculation is greater in malignant MCF-7 cells relative to non-malignant hCMEC-D3 cells, increases in free cytosolic Ca2+ via endoplasmic reticulum (ER) Ca2+ store depletion with thapsigargin increases EV biogenesis in both cell types, and vesicular induction is abolished by the intracellular Ca2+ chelator BAPTA-AM. Store-operated calcium entry (SOCE) plays an essential role in the maintenance of EV biogenesis after store depletion. These findings contribute to furthering our understanding of extracellular vesicle biogenesis. Furthermore, since EVs are key mediators in the intercellular transfer of deleterious cancer traits such as cancer multidrug resistance (MDR), understanding the molecular mechanisms governing their biogenesis in cancer is the crucial first step in finding novel therapeutic targets that circumvent EV-mediated MDR.
Microvesicles (MV) are emerging as important mediators of intercellular communication. While MVs are important signaling vectors for many physiological processes, they are also implicated in cancer pathology and progression. Cellular activation is perhaps the most widely reported initiator of MV biogenesis, however, the precise mechanism remains undefined. Uncovering the proteins involved in regulating MV biogenesis is of interest given their role in the dissemination of deleterious cancer traits. MVs shed from drug-resistant cancer cells transfer multidrug resistance (MDR) proteins to drug-sensitive cells and confer the MDR phenotype in a matter of hours. MDR is attributed to the overexpression of ABC transporters, primarily P-glycoprotein and MRP1. Their expression and functionality is dependent on a number of proteins. In particular, FERM domain proteins have been implicated in supporting the functionality of efflux transporters in drug-resistant cells and in recipient cells during intercellular transfer by vesicles. Herein, the most recent research on the proteins involved in MV biogenesis and in the dissemination of MV-mediated MDR are discussed. Attention is drawn to unanswered questions in the literature that may prove to be of benefit in ongoing efforts to improve clinical response to chemotherapy and circumventing MDR.
Chellappan, DK, Ng, ZY, Wong, J-Y, Hsu, A, Wark, P, Hansbro, N, Taylor, J, Panneerselvam, J, Madheswaran, T, Gupta, G, Bebawy, M, Hansbro, PM & Dua, K 2018, 'Immunological axis of curcumin-loaded vesicular drug delivery systems.', Future medicinal chemistry, vol. 10, no. 8, pp. 839-844.View/Download from: Publisher's site
Several vesicular systems loaded with curcumin have found their way in the therapeutic applications of several diseases, primarily acting through their immunological pathways. Such systems use particles at a nanoscale range, bringing about their intended use through a range of complex mechanisms. Apart from delivering drug substances into target tissues, these vesicular systems also effectively overcome problems like insolubility and unequal drug distribution. Several mechanisms are explored lately by different workers, and interest over vesicular curcumin has been renewed in the past decade. This commentary discusses several immunological targets in which curcumin is employed in a vesicular form.
Taylor, J, Jaiswal, R & Bebawy, M 2017, 'Calcium-calpain Dependent Pathways Regulate Vesiculation in Malignant Breast Cells.', Current Cancer Drug Targets, vol. 17, no. 5, pp. 486-494.View/Download from: Publisher's site
Multidrug resistance in cancer (MDR) occurs when tumours become cross-resistant to a range of different anticancer agents. One mechanism by which MDR can be acquired is through cell to cell communication pathways. Membrane-derived microparticles (MPs) are emerging as important signaling molecules in this process. MPs are released from most eukaryotic cells and transfer functional proteins and nucleic acids to recipient cells conferring deleterious traits within the cancer cell population including MDR, metastasis, and angiogenesis. MP formation is known to be dependent on calpain, an intracellular cysteine protease which acts to cleave the cytoskeleton underlying the plasma membrane, resulting in cellular surface blebbing. This study examines differences in vesiculation between malignant and non-malignant cells using high-resolution Atomic Force Microscopy (AFM). We demonstrate that malignant MCF-7 and MCF-7/Dx cells have an intrinsically higher degree of vesiculation at rest when compared to non-malignant human brain endothelial cells (HBEC) and human mammary epithelial cells (MBE-F).. Cellular activation with the calcium ionophore A23187 resulted in an increase in vesiculation in all cell types. We show that calpain-mediated MP biogenesis is the dominant pathway at rest in malignant cells as vesiculation was shown to be inhibited with calpain inhibitor II (ALLM). These results suggest that differences in the biogenic pathways exist in malignant and non-malignant cells and have important implications in defining novel strategies to selectively targeting malignant cells for the circumvention of deleterious traits acquired through intercellular exchange of extracellular vesicles.