Abstract 60: The association between cellular senescence of cancer associated fibroblasts and tumor progression in pancreatic cancer

Background: In recent days, cellular senescence of cancer associated fibroblasts (CAFs) is gaining increased attention, yet incompletely understood the role in the development of malignant diseases. Previous studies reported that Caveolin-1 plays a major role in cellular senescence, and its expression in CAFs. Therefore, we hypothesized that cellular senescence of CAFs introduces the tumor progression in pancreatic cancer (PC). Methods: A total of 159 consecutive patients with PC who underwent curative resection between January 2004 and December 2016 were enrolled. The patients were divided into two groups according to the expression of Caveolin-1 in CAFs, which were analyzed by immunohistochemistry. First, we investigated the relationship between the expression of Caveolin-1 in CAFs and patients' clinicopathological factors including survival outcomes. Second, we established the CAFs-cell lines from the resected tissues of patient with PC. We stocked CAFs-cell line after 6 times passages at least. Third, we controlled the expression of Caveolin-1in CAFs, and underwent coculture of PC cell lines and CAFs-conditioned medium (CM) to evaluate the effect of cellular senescence in CAFs on invasion of PC cell lines. Results: The high level of Caveolin-1 expression group counts of 49 patients (31%), and the low level of Caveolin-1 expression group counts of 110 patients (69%). As for patients' clinicopathological factors, the serum levels of CA19-9 (p=0.0008) and pathological T factor stage (p=0.014), defined by Japan Pancreas Society as the “General Rules for the Study of Pancreatic Cancer” were significantly higher in the high Caveolin-1 expression group than were those of the low expression group. The high Caveolin-1 expression group had significantly worse outcomes in overall (log-rank p = 0.022) and disease-free survivals (log-rank p = 0.011). We established 10 CAFs cell lines from clinical samples, and evaluated Caveolin-1 expressions. We identified the high Caveolin-1 expression CAFs (CAF-4 and 5), and suppressed its expression by transfection of short interfering (si) Caveolin-1 knockdown. We collected CAF-CM from CAF-4 and CAF-5 with siCaveolin-1suppressed the invasive ability of MiaPaCa-2 compared to that with si control (p