The impact of cellular senescence and senescence­associated secretory phenotype in cancer­associated fibroblasts on the malignancy of pancreatic cancer.

Cancer­associated fibroblasts (CAFs) are implicated in the strong malignancy of pancreatic cancer (PC). Various CAF subtypes have different functions, and their heterogeneity likely influence the malignancy of PC. Meanwhile, it is known that senescent cells can create a tumor­promoting microenvironment by inducing a senescence­associated secretory phenotype (SASP). In the present study, the effects of individual differences in CAFs on PC malignancy were investigated with a focus on cellular senescence. First, primary cultures of CAFs from 8 PC patients were generated and co­cultured with PC cell lines. This co­culture assay showed that differences in CAFs induce differences in PC cell proliferation. It was further investigated which clinical factors affected the malignant potential of CAF and it was found that the difference of malignant potential of each CAF was marginally related to the age of original patients. Next, to verify the senescence of CAFs really affected the malignant potential of CAF, PCR array analysis of each CAF sample was performed and it was revealed that expression of genes about cellular senescence and SASP such as tumor protein p53, nuclear factor kappa B subunit 1, and IL6, are related to the malignant potential of CAFs impacting on PC proliferation. Finally, to elucidate the effect of p53­mediated cellular senescence of CAFs on malignant potential of PC, it was examined whether CAFs with the treatment of p53 inhibitor affected PC cell proliferation in co­culture assays. The treatment of CAFs with p53 inhibitor significantly suppressed PC cell proliferation. In addition, a comparison of the concentration of IL­6, a SASP cytokine, in the co­culture supernatant showed a significant decrease in the sample after p53 inhibitor treatment. In conclusion, the present results suggested that proliferation potential of PC may be related to p53­mediated cellular senescence and SASP of CAFs.