## 3 Results  
### Screening for Changes in Serum miR's Associated with PDAC Progression in Mice and Patients  
The aim of our study was to determine which circulating miR are associated with PDAC progression in mice as well as in patients. The approach of the miR screening is shown in Figure 1a. The _LSL-Kras_G12D/+; _LSL-Trp53R172H+; P48-Cre_ (KPC) transgenic mice develop metastatic PDAC that recapitulates the human disease [23]. We first investigated the serum miR expression in mice with pancreatic pre-invasive intraepithelial neoplasia (PanIN) lesions (Figure S1a) and mice with metastatic PDAC (Figure S1b) to assess whether serum miR are altered during cancer progression. Expression levels of 154 out of 179 serum miR were detected above threshold and 27 miR were differentially expressed \(\geq\)3-fold between the two mouse groups. KPC mice with metastatic disease had 13 miR miR upregulated and 14 serum miR downstreamregulated compared to age-matched mice with only preinvasive lesions (Table S1). Next, we analyzed paired pre- and post-pancreaticoduodenectomy sera from two patients with resectable PDAC. Our aim was to assess whether the change in serum miR expression after surgery was distinct in patients with different progression free survival (PFS) and compare the results to the murine  
Figure 1: Overview of the serum miR screening in mice and patients to identify miR associated with pancreatic cancer progression. (**a**) Schematic of performed RT-qPCR based miR discovery. Serum miR from two groups of _LSL-Kras_G12D/+; _LSL-Trp53R172H+; P48-Cre_ (KPC) mice with different disease stages were analyzed for association with PDAC progression. Additionally, two patients with resectable PDAC were screened for expression of serum miRś to identify indicators of progression free survival (PFS) after surgical tumor removal. Overlapping differentially expressed miR (DEmiRRs) were selected for validation in an additional cohort of patients. (**b**) List of \(\geq\)3-fold DEmiRRs that are associated with PDAC progression in KPC mice (left circle) and patients (right circle), identified in the miR screening. Upregulation of the miRs in bold red were associated with progressive PDAC in both mice and patients. These miRs were selected for validation. metastases-related miR. We initially profiled 250 miR before and after primary tumor resection in two patients with PFS of 7 or 18 months (Figure 1a). From the 250 miR we could reliably detect 171 serum miR in all four samples, and we compared the changes in miR expression due to tumor resection of the patient with early recurrence to the changes in the patient with late recurrence. As a result of tumor resection, 28 miR were differentially expression between the two patients: 12 miR were upregulated \(\geq\)3-fold in the patient with fast progressive disease, whereas 16 miR were downregulated compared to the patient with late progressive disease (Table S2). Figure 1b provides an overview of the PDAC progression-related serum miR that were identified in our screening. Eight miR (miR-16-5p, miR-451a, miR-93-5p, miR-15a-5p, miR-19a-3p, miR-122-5p, miR-99a-5p, and miR-125b-5p) were altered \(\geq\)3-fold in PDAC progression in mice as well as in patients. The three upregulated miR that are associated with PDAC progression across species (miR-125b-5p, miR-99a-5p, and miR-122-5p, Figure 1b, in red), were reduced \(>\)4 fold after resection in the patient with long PFS, whereas these miR were upregulated after surgery in the patient with early disease recurrence. We selected these three potentially oncogenic miR for validation in 26 additional PDAC patients. Circulating miR-125b-5p and miR-99a-5p Levels after Tumor Resection are Associated with Early Recurrence in PDAC Patients  
We measured the expression levels of miR-122-5p, miR-99a-5p, and miR-125b-5p before and after pancreaticoduodenectomy in the additional PDAC patients. Table 1 provides an overview of the patient characteristics of the total cohort.