SERPINE1 and neoplasm: The main progenitors of CAFs seem to be the local fibroblasts and these fibroblasts obtain MF characteristics by TGF‐β stimulation in the tumour stroma.21, 22 Therefore, to investigate whether PAI‐1 had association with normal fibroblasts obtaining MF characteristics in the tumour microenvironment, we examined whether the α‐SMA expression of MLF and MRC‐5 cell lines after TGF‐β stimulation was limited by PAI‐1 inhibition.