Fig 2: Survival Analysis. (A) Survival analysis of all PDAC patients with and without peritoneal carcinomatosis (PDAC (PER+) + PDAC (PER-)). p=0.0482, n=27. (B) Survival analysis of only PDAC (PER-) patients without peritoneal carcinomatosis. p=0.1699, n=18. Blue: High expression of exo-ROR1, Black: Low expression of exo-ROR1. (C) Survival analysis according to ROR1 mRNA in tumor tissue. p=0.8414, n=25. Blue: High expression of ROR1 mRNA, Black: Low expression of ROR1 mRNA.

Fig 3: Exo-ROR1 in peritoneal fluid (PF) and plasma and soluble ROR1 in PF. (A) Values of normalized CD9/63/81-APC signal intensity of exo-ROR1 (%) in PF. Non Cancer: n=15, Pancreatitis: n=4, PDAC (PER-): n=18, PDAC (PER+): n=9. *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001. (B) Values of normalized CD9/63/81-APC signal intensity of exo-ROR1 (%) in plasma. Non Cancer: n=11, Pancreatitis: n=4, PDAC (PER-): n=6, PDAC (PER+): n=8. *p<0.05. (C) ELISA: Concentrations of soluble ROR1 (ng/ml) in PF. Non Cancer: n=11, Pancreatitis: n=4, PDAC (PER-): n=16, PDAC (PER+): n=6. **p<0.01.

Fig 4: Western Blots (WB), qPCR and Immunhistochemistry (IHC) of exosomes in PF and lysed tissue. (A) Western Blot with ROR1 and CD81 of isolated exosomes from PF. Both proteins are expressed on the exosomes of all different groups (Non Cancer, Pancreatitis, PDAC (PER-), PDAC (PER+). For uncropped WB refer to Supplementary Figure S2 . (B) Western Blot of lysed tissue from Non Cancer, Pancreatitis, PDAC. ROR1 and also β-Actin as loading control is expressed in all three groups. For uncropped WB refer to Supplementary Figure S2 . (C) qPCR analysis and relative ROR1 expression of pancreatic tissue. ROR1 is expressed on NC, CP and PDAC tissue showing no significant differences between the groups but a slightly higher expression in the PDAC tissue. (D) Immunohistochemistry (IHC) and HE staining of non-cancerous exocrine pancreatic tissue, CP, PDAC and peritoneal metastasis. The exocrine pancreas is ROR1 negative. In the CP tissue ROR1 positive islet cells are shown in the higher magnification (arrows). The fibrotic tissue is negative. In PDAC and the peritoneal metastasis the morphologic tumor cells are ROR1 positive.

Fig 5: Experimental layout. (A) Samples (PF and blood) were collected and several centrifugation steps and two ultracentrifugation steps were performed. Additionally, samples were filtered through a 0.2 µm filter and finally exosomes were collected in 500 µl of PBS. (B) Exosomes were incubated with ROR1 labeled capture antibody beads and following with detection antibodies for the three known exosomal markers CD9, CD63, and CD81. Finally, FACS analysis was performed. Created with BioRender.com.