The sustained growth, invasion, and metastasis of cancer cells depend upon bidirectional cell-cell communication within complex tissue environments. Such communication predominantly involves the secretion of soluble factors by cancer cells and/or stromal cells within the tumour microenvironment (TME), although these cell types have also been shown to export membrane-encapsulated particles containing regulatory molecules that contribute to cell-cell communication. These particles are known as extracellular vesicles (EVs) and include species of exosomes and shed microvesicles. EVs carry molecules such as oncoproteins and oncopeptides, RNA species (for example, microRNAs, mRNAs, and long non-coding RNAs), lipids, and DNA fragments from donor to recipient cells, initiating profound phenotypic changes in the TME. Emerging evidence suggests that EVs have crucial roles in cancer development, including pre-metastatic niche formation and metastasis. Cancer cells are now recognized to secrete more EVs than their nonmalignant counterparts, and these particles can be isolated from bodily fluids. Thus, EVs have strong potential as blood-based or urine-based biomarkers for the diagnosis, prognostication, and surveillance of cancer. In this Review, we discuss the biophysical properties and physiological functions of EVs, particularly their pro-metastatic effects, and highlight the utility of EVs for the development of cancer diagnostics and therapeutics.

Extracellular vesicles in cancer - implications for future improvements in cancer care.

Lysosomes are ubiquitous membrane-bound intracellular organelles with an acidic interior. They are central for degradation and recycling of macromolecules delivered by endocytosis, phagocytosis, and autophagy. In contrast to the rather simplified view of lysosomes as waste bags, nowadays lysosomes are recognized as advanced organelles involved in many cellular processes and are considered crucial regulators of cell homeostasis. The function of lysosomes is critically dependent on soluble lysosomal hydrolases (e.g. cathepsins) as well as lysosomal membrane proteins (e.g. lysosome-associated membrane proteins). This review focuses on lysosomal involvement in digestion of intra- and extracellular material, plasma membrane repair, cholesterol homeostasis, and cell death. Regulation of lysosomal biogenesis and function via the transcription factor EB (TFEB) will also be discussed. In addition, lysosomal contribution to diseases, including lysosomal storage disorders, neurodegenerative disorders, cancer, and cardiovascular diseases, is presented.

/pdf/the-lysosome-from-waste-bag-to-potential-therapeutic-target-2zxxln3iio.pdf

The lysosome: from waste bag to potential therapeutic target

Macrophage M1/M2 polarization.

Exciting new discoveries have transformed the view of the lysosome from a static organelle dedicated to the disposal and recycling of cellular waste to a highly dynamic structure that mediates the adaptation of cell metabolism to environmental cues. Lysosome-mediated signalling pathways and transcription programmes are able to sense the status of cellular metabolism and control the switch between anabolism and catabolism by regulating lysosomal biogenesis and autophagy. The lysosome also extensively communicates with other cellular structures by exchanging content and information and by establishing membrane contact sites. It is now clear that lysosome positioning is a dynamically regulated process and a crucial determinant of lysosomal function. Finally, growing evidence indicates that the role of lysosomal dysfunction in human diseases goes beyond rare inherited diseases, such as lysosomal storage disorders, to include common neurodegenerative and metabolic diseases, as well as cancer. Together, these discoveries highlight the lysosome as a regulatory hub for cellular and organismal homeostasis, and an attractive therapeutic target for a broad variety of disease conditions.

Lysosomes as dynamic regulators of cell and organismal homeostasis

An accumulation of unfolded or misfolded proteins in the endoplasmic reticulum (ER) leads to stress conditions. To mitigate such circumstances, stressed cells activate a homeostatic intracellular signaling network cumulatively called the unfolded protein response (UPR), which orchestrates the recuperation of ER function. Macroautophagy (hereafter autophagy), an intracellular lysosome-mediated bulk degradation pathway for recycling and eliminating wornout proteins, protein aggregates, and damaged organelles, has also emerged as an essential protective mechanism during ER stress. These 2 systems are dynamically interconnected, and recent investigations have revealed that ER stress can either stimulate or inhibit autophagy. However, the stress-associated molecular cues that control the changeover switch between induction and inhibition of autophagy are largely obscure. This review summarizes the crosstalk between ER stress and autophagy and their signaling networks mainly in mammalian-based systems. Additionally, we highlight current knowledge on selective autophagy and its connection to ER stress.

https://www.tandfonline.com/doi/pdf/10.1080/15548627.2015.1091141

ER stress: Autophagy induction, inhibition and selection.

https://www.jidonline.org/article/S0022-202X(15)34410-9/pdf

Redox-Dependent Translocation of p53 to Mitochondria or Nucleus in Human Melanocytes after UVA- and UVB-Induced Apoptosis

Ultraviolet (UV) irradiation induces skin pigmentation, which relies on the intercellular crosstalk of melanin between melanocytes to keratinocytes. However, studying the separate effects of UVA and UVB irradiation reveals differences in cellular response. Herein, we show an immediate shedding of extracellular vesicles (EVs) from the plasma membrane when exposing human melanocytes to UVA, but not UVB. The EV-shedding is preceded by UVA-induced plasma membrane damage, which is rapidly repaired by Ca2+-dependent lysosomal exocytosis. Using co-cultures of melanocytes and keratinocytes, we show that EVs are preferably endocytosed by keratinocytes. Importantly, EV-formation is prevented by the inhibition of exocytosis and increased lysosomal pH but is not affected by actin and microtubule inhibitors. Melanosome transfer from melanocytes to keratinocytes is equally stimulated by UVA and UVB and depends on a functional cytoskeleton. In conclusion, we show a novel cell response after UVA irradiation, resulting in transfer of lysosome-derived EVs from melanocytes to keratinocytes.

/pdf/extracellular-vesicles-are-transferred-from-melanocytes-to-23h0rjs7hl.pdf

Extracellular vesicles are transferred from melanocytes to keratinocytes after UVA irradiation

Fibroblast activation protein-α (FAP-α) promotes tumor growth and cell invasiveness through extracellular matrix degradation. How ultraviolet radiation (UVR), the major risk factor for malignant melanoma, influences the expression of FAP-α is unknown. We examined the effect of UVR on FAP-α expression in melanocytes, keratinocytes and fibroblasts from the skin and in melanoma cells. UVR induces upregulation of FAP-α in fibroblasts, melanocytes and primary melanoma cells (PM) whereas keratinocytes and metastatic melanoma cells remained FAP-α negative. UVA and UVB stimulated FAP-α- driven migration and invasion in fibroblasts, melanocytes and PM. In co-culture systems UVR of melanocytes, PM and cells from regional metastases upregulated FAP- α in fibroblasts but only supernatants from non-irradiated PM were able to induce FAP-α in fibroblasts. Further, UV-radiated melanocytes and PM significantly increased FAP- α expression in fibroblasts through secretory crosstalk via Wnt5a, PDGF-BB and TGF- β1. Moreover, UV radiated melanocytes and PM increased collagen I invasion and migration of fibroblasts. The FAP- α/ DPPIV inhibitor Gly-ProP(OPh)2 significantly decreased this response implicating FAP- α/DPPIV as an important protein complex in cell migration and invasion. These experiments suggest a functional association between UVR and FAP- α expression in fibroblasts, melanocytes and melanoma cells implicating that UVR of malignant melanoma converts fibro- blasts into FAP- α expressing and ECM degrading fibroblasts thus facilitating invasion and migration. The secretory crosstalk between melanoma and tumor surrounding fibroblasts is mediated via PDGF-BB, TGF-β1 and Wnt5a and these factors should be evaluated as targets to reduce FAP- α activity and prevent early melanoma dissemination.

/pdf/ultraviolet-exposure-of-melanoma-cells-induces-fibroblast-v466n2j5hm.pdf

Ultraviolet exposure of melanoma cells induces fibroblast activation protein-α in fibroblasts: Implications for melanoma invasion.

Ultraviolet (UV) irradiation is a major environmental carcinogen involved in the development of skin cancer. To elucidate the initial signaling during UV-induced damage in human keratinocytes, we investigated lysosomal exocytosis and apoptosis induction. UVA, but not UVB, induced plasma membrane damage, which was repaired by Ca2+-dependent lysosomal exocytosis. The lysosomal exocytosis resulted in extracellular release of cathepsin D and acid sphingomyelinase (aSMase). Two hours after UVA irradiation, we detected activation of caspase-8, which was reduced by addition of anti-aSMAse. Furthermore, caspase-8 activation and apoptosis was reduced by prevention of endocytosis and by the use of cathepsin inhibitors. We conclude that lysosomal exocytosis is part of the keratinocyte response to UVA and is followed by cathepsin-dependent activation of caspase-8. The findings have implications for the understanding of UV-induced skin damage and emphasize that UVA and UVB initiate apoptosis through different signaling pathways in keratinocytes.

/pdf/lysosomal-exocytosis-and-caspase-8-mediated-apoptosis-in-uva-105a89irbb.pdf

Petra Wäster

Papers

The lysosome: from waste bag to potential therapeutic target

Redox-Dependent Translocation of p53 to Mitochondria or Nucleus in Human Melanocytes after UVA- and UVB-Induced Apoptosis

Extracellular vesicles are transferred from melanocytes to keratinocytes after UVA irradiation

Ultraviolet exposure of melanoma cells induces fibroblast activation protein-α in fibroblasts: Implications for melanoma invasion.

Lysosomal exocytosis and caspase-8-mediated apoptosis in UVA-irradiated keratinocytes.