Extracellular vesicles (EVs) carry molecules derived from donor cells and are able to alter the properties of recipient cells. They are important players during the genesis and progression of tumors. Uveal melanoma (UM) is the most common primary intraocular tumor in adults and is associated with a high rate of metastasis, primarily to the liver. However, the mechanisms underlying this process are poorly understood. In the present study, we analyzed the oncogenic potential of UM-derived EVs and their protein signature. We isolated and characterized EVs from five UM cell lines and from normal choroidal melanocytes (NCMs). BRCA1-deficient fibroblasts (Fibro-BKO) were exposed to the EVs and analyzed for their growth in vitro and their reprograming potential in vivo following inoculation into NOD-SCID mice. Mass spectrometry of proteins from UM-EVs and NCM-EVs was performed to determine a protein signature that could elucidate potential key players in UM progression. In-depth analyses showed the presence of exosomal markers, and proteins involved in cell-cell and focal adhesion, endocytosis, and PI3K-Akt signaling pathway. Notably, we observed high expression levels of HSP90, HSP70 and integrin V in UM-EVs. Our data bring new evidence on the involvement of UM-EVs in cancer progression and metastasis.

High-grade serous ovarian cancer (HGSOC) is a significant cause of mortality among women worldwide. Traditional treatment consists of platinum-based therapy; however, rapid development of platinum resistance contributes to lower life expectancy, warranting newer therapies to supplement the current platinum-based protocol. Repurposing market-available drugs as cancer therapeutics is a cost- and time-effective way to avail new therapies to drug-resistant patients. The anti-HIV agent nelfinavir (NFV) has shown promising toxicity against various cancers; however, its role against HGSOC is unknown. Here, we studied the effect of NFV against HGSOC cells obtained from patients along disease progression and carrying different sensitivities to platinum. NFV triggered, independently of platinum sensitivity, a dose-dependent reduction in the HGSOC cell number and viability, and a parallel increase in hypo-diploid DNA content. Moreover, a dose-dependent reduction in clonogenic survival of cells escaping the acute toxicity was indicative of long-term residual damage. In addition, dose- and time-dependent phosphorylation of H2AX indicated NFV-mediated DNA damage, which was associated with decreased survival and proliferation signals driven by the AKT and ERK pathways. NFV also mediated a dose-dependent increase in endoplasmic reticulum stress-related molecules associated with long-term inhibition of protein synthesis and concurrent cell death; such events were accompanied by a proapoptotic environment, signaled by increased phospho-eIF2α, ATF4, and CHOP, increased Bax/Bcl-2 ratio, and cleaved executer caspase-7. Finally, we show that NFV potentiates the short-term cell cycle arrest and long-term toxicity caused by the proteasome inhibitor bortezomib. Overall, our in vitro study demonstrates that NFV can therapeutically target HGSOC cells of differential platinum sensitivities via several mechanisms, suggesting its prospective repurposing benefit considering its good safety profile.

Introduction: Extracellular vesicles (EVs) play a crucial role in disseminating cancer to distant organs, communicating with the tumor microenvironment to prepare the metastatic niche, and through horizontal transfer of oncogenic traits to recipient cells. EV parameters influencing cellular uptake include surface proteins, lipid profile, and physicochemical properties such as size and zeta potential. EVs isolated from cells are heterogeneous populations, which hinder the study of single EV variables and their influence on cellular uptake. Moreover, EV isolation is a lengthy and laborious process with an extremely low yield. Liposomes are synthetic vesicles that share properties with EVs, such as the lipid bilayer and the capability to encapsulate relevant biomolecules. In this study, we used a uveal melanoma (UM) model, a highly liver metastatic tumor, to characterize naturally occurring EVs and model them using liposomes. Methods: We utilized liposomes as a model of EVs to study how the size and zeta potential influence cellular internalization. EVs were isolated from primary UM cells (MP41) using ultracentrifugation (UC) and characterized using dynamic light scattering, nanoparticle tracking analysis, as well as electrophoretic mobility for hydrodynamic size, concentration, and zeta potential, respectively. Liposomes mimicking EVs were produced using the periodic disturbance mixer (nanoprecipitation). The lipid composition was DMPC: CHOL: DHP at different ratios and 0.2% molar concentration of SP-DiIC18(3) as labeling reagent. Liposomes were then dialyzed overnight using a membrane size of 12kDa. Cellular uptake was assessed in immortalized human hepatocytes, representing the liver microenvironment. Results: Using surface response methodology (SRM), we created a model to predict size and zeta potential depending on liposome manufacturing conditions. We produced anionic and neutral liposomes with zeta potential ~-30 mV and 0mV, respectively, and with a size of ~150 nm, similar to EVs derived from MP41 cells in order to evaluate the influence of zeta potential in cellular uptake. Our results showed no significant differences at 0 and 6 hours between anionic and neutral EV-like liposomes. By contrast, the uptake of the anionic liposomes was significantly higher at 24 h compared to neutral ones. Moreover, EV-like liposomes were produced 1000x more concentrated than naturally occurring EVs isolated using UC. Conclusion: In this study, we describe a novel approach using synthetic biology to produce EV-like liposomes as a model to study EV cellular uptake and its role in metastasis. Our data demonstrate that liposomes are a feasible tool to study EV variables individually, thereby addressing the high heterogeneity of biological samples, and producing high liposome yield, thereby helping to accelerate research Citation Format: Rubén Rodrigo López Salazar, Chaymaa Zouggari, Thupten Tsering, Prisca Bustamante Alvarez, Ion Stiharu, Catherine Mounier, Vahe Nerguizian, Julia V. Burnier. Cancer cell-derived extracellular vesicle mimicking: A parametric study of the physicochemical characteristics of EVs and their influence on cellular uptake in metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1741.

High-grade serous ovarian cancer (HGSOC) is a significant cause of mortality among women worldwide. Traditional treatment consists of platinum-based therapy; however, the rapid development of platinum resistance contributes to lower life expectancy, warranting newer therapies to supplement the current platinum-based protocol. Repurposing market-available drugs as cancer therapeutics is a cost- and time-effective way to avail new therapies to drug-resistant patients. The anti-HIV agent nelfinavir (NFV) has shown promising toxicity against various cancers; however, its role against HGSOC is unknown. Here, we studied the effect of NFV against HGSOC cells obtained from patients along disease progression and carrying different sensitivities to platinum. NFV triggered, independently of platinum sensitivity, a dose-dependent reduction of HGSOC cell number and viability, and a parallel increase in hypo-diploid DNA content. Moreover, a dose-dependent reduction of clonogenic survival of cells escaping the acute toxicity was indicative of long-term residual damage. Western blot analysis of underlying molecular mechanisms revealed activation by NFV of the three signaling arms of the unfolded protein response (UPR): PERK, IRE1alpha and ATF6 - in a similar manner to the classical endoplasmic reticulum (ER) stressor tunicamycin. NFV-mediated modulation of the UPR was accompanied by the inhibition of global protein synthesis as analyzed through a non-radioactive method by labelling the nascent polypeptides with puromycin. NFV maintained a proapoptotic environment through the UPR, evidenced by a dose- and time-dependent enhanced expression of ATF4, CHOP, increased Bax/Bcl2 ratio, and cleavage of executioner caspase-7. Enhanced gamma-H2AX suggested NFV-mediated induction of DNA damage, which was associated with decreased proliferation signals driven by the AKT and ERK pathways. NFV increased the level of autophagosome-associated protein LC3II in HGSOC cells of varying platinum sensitivities; however, the autophagic flux was not increased during co-treatment with NFV and the lysosomal inhibitor bafilomycin A1, suggesting a likely impairment of the lysosomes by NFV impeding autophagosome clearance. Finally, we show that NFV potentiates the short-term cell cycle arrest and long-term toxicity caused by the proteasome inhibitor bortezomib. Overall, our in vitro study demonstrates that NFV can therapeutically target HGSOC cells of differential platinum sensitivities via several mechanisms, suggesting its prospective repurposing benefit considering its good safety profile. Citation Format: Mahbuba R. Subeha, Alicia A. Goyeneche, Prisca Bustamante, Michael A. Lisio, Julia V. Burnier, Carlos M. Telleria. Nelfinavir induced-cytotoxicity towards high-grade serous ovarian cancer cells involves induction of the unfolded protein response, modulation of protein synthesis, DNA damage, lysosomal impairment, and potentiation of toxicity caused by proteasome inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1839.

Liquid biopsy-based detection of circulating free DNA (cfDNA) is a promising tool to monitor tumor progression and treatment response. cfDNA release is thought to result from a combination of cell death (apoptosis and necrosis), and active cellular secretion. As such, cytotoxic anti-cancer therapies can impact cfDNA kinetics. This makes the interpretation of cfDNA analyses pivotal for its applicability as a biomarker. In this study, we assessed the kinetics and fragmentation of cfDNA in cancer cells of various origins following standard anti-cancer treatments with different cytotoxic effects and mechanisms of action.Human colorectal carcinoma, lung adenocarcinoma, and uveal melanoma cancer cells were subjected to different forms of cytotoxic stress, including induction of apoptosis (tumor necrosis factor (TNF)-related apoptosis-inducing ligand (Apo2L/TRAIL)), cell cycle arrest (Roscovitine, Valproic acid), necrosis (radiotherapy), and senescence. Following treatments, cells were analyzed for their cell cycle progression, level of senescence, and mechanism of cell death (apoptosis vs. necrosis). Heat treatment was used as a control for necrosis-related cell death. Total cfDNA and mutant cfDNA (based on the mutations of each parental cell line) were isolated from cultured media and quantified using the Qubit assay and digital droplet PCR targeting, respectively. Fragment length of the isolated cfDNA was visualized using the Bioanalyzer 2100.Total and mutant cfDNA levels increased during all cytotoxic treatments in a concentration-dependent manner. Notably, cells undergoing apoptosis shed higher levels of cfDNA compared to necrotic and senescent cells. In addition, electropherogram images showed that cytotoxic conditions alter fragment size distribution, with smaller fragments of 1000 bp with necrosis.The kinetics and fragmentation of released cfDNA are influenced by cytotoxic insults. Determining the characteristics of cfDNA can facilitate and improve its use as a clinical biomarker during anti-cancer therapy. Our data pave the way for the establishment of criteria to apply when monitoring cfDNA for cancer management based on the anticancer therapeutic strategy.