PTEN is a candidate tumour suppressor gene and frequently mutated in multiple cancers, however, not in pancreatic cancer.Recently, it has been demonstrated that PTEN expression is regulated by TGF-b1. Using TGF-b1 transgenic mice (n=7) and wildtype littermates (n=6), as well as pancreatic tissues obtained from organ donors (n=10) and patients with pancreatic cancer (n=10), we assessed the expression of PTEN by means of immunohistochemistry and semiquantitative PCR analysis. In addition, PANC-1 cells were treated with TGF-b1 in vitro and the levels of PTEN mRNA were determined in these cells. In human pancreatic cancers PTEN mRNA levels were significantly decreased (P50.05). In addition, in the pancreas of TGF-b1 transgenic mice the expression of PTEN was significantly reduced (P50.01), as compared to wildtype littermates and incubation of PANC-1 cells with TGF-b1 decreased PTEN mRNA levels after 24 h. Inasmuch as TGF-b1 decreases PTEN expression in human pancreatic cancer cells and human pancreatic cancers overexpress TGF-b1, the reduced expression of PTEN in pancreatic cancer may be mediated by TGF-b1 overexpression. Thus, although PTEN is not mutated in pancreatic cancers, the reduction of its expression may give pancreatic cancer cells an additional growth advantage.