Trated in our earlier study (Leca et al, JCI, 2016). More importantly, we demonstrated that PRT99 is physically linked to the ANXA6 complex discovered in our prior study. Then applying PRT99 blocking antibody, we confirmed the implication of PRT99 in EVs uptake by reducing EVs internalization in pancreatic cancer cells plus a consequent lowered migratory Cathepsin H Proteins web capability. Preliminary results suggest that following ANXA6+ EVs uptake by pancreatic cancer cells inside a PRT99-dependent course of action enhances their migratory potential by way of p38 signalling pathway activation. Summary/conclusion: Our benefits deepen the understanding of EVs internalization mode and demonstrate that PRT99 can be a vital element of ANXA6+ EVs uptake by cancer cells and their consequent gain in migratory capability. Limiting or impairing the action of PRT99 gives a brand new window to limit the oncogenic dialogue amongst stromal and cancer cells in pancreatic cancer. Funding: INCa PLBIO13-134, ERC, SIRIC.Thursday, 03 MayPT04.GABARAPL1 is expected for the secretion of pro-angiogenic extracellular vesicles for the duration of hypoxia Tom G.H. Keulers1; Marijke I. Zonneveld1; Sten F.H.M. Libregts2; Marca H. M. Wauben2; Kasper M.A. Rouschop1 Autophagy lab, department of Radiotherapy, Grow – school for Oncology Developmental Biology, Maastricht University, Maastricht, The Netherlands; 2Department of Biochemistry and Cell Biology Faculty of Veterinary Medicine, Utrecht University, Utrecht, The NetherlandsBackground: Hypoxia is a hallmark of strong tumours and is connected with tumour progression and therapy resistance. In response to hypoxia, tumour cells secrete pro-angiogenic factors to induce blood vessel formation and restore oxygen provide for the tumour. Extracellular vesicles (EVs) are emerging as mediators of intercellular communication in the tumour microenvironment and mediate intercellular communication by shuttling biological info for example miRNA’s, mRNA, proteins and development variables to recipient cells. Previously, we demonstrated that the expression of GABARAPL1, a member in the LC3/GABARAP protein household, is induced throughout hypoxia. Now, we demonstrate that GABARAPL1 is needed for secretion of pro-angiogenic EVs through hypoxia. Strategies: Ht29 and U87 doxycycline-inducible GABARAPL1 Zika Virus E proteins Synonyms knockdown cell lines have been exposed to hypoxia (16 h, 0.02 O2). EVs had been isolated by sucrose density gradient isolation and analysed by western blot, qNANO or high-resolution flow cytometry. Angiogenic possible of cells was assessed by tube formation assays. Xenografts were implanted subcutaneously in the lateral flanks of NMRInu/nu mice and tumour size was measured by calliper. Benefits: GABARAPL1 is expressed around the EV surface and can be targeted with antibodies. This results in blockade of pro-angiogenic responses in vitro. Silencing GABARAPL1 with inducible knockdown models perturbs EV secretion and outcomes in decreased tumour development as a result of decreased vascularisation and enhanced necrosis. In addition, targeting GABARAPL1 directly right after tumour irradiation resulted in enhanced tumour regrowth delay. In addition, we demonstrate that GABARAPL1+ EVs are detectable and enhanced in blood of cancer individuals. Summary/conclusion: Here, we reveal that hypoxic tumour cells secrete a distinctive EV subset, marked by GABARAPL1 expression. These EVs handle tumour progression, are targetable and are for that reason interesting to pursue as biomarker and therapeutic target. Funding: This function was financially supported by the Dutch Can.