PTEN and neoplasm: The primary results of this study are that (1) a positive correlation between Ni concentration and the incidence of PDAC was found in the PDAC tissue samples; (2) exposure to Ni was toxic to all the PDAC cells and, although Ni-acetate appeared to be most toxic, both NiCl2 and Ni-acetate alter the expression of phospho-AKT, PTEN, and FOXO-1; (3) the oncogenic miR-221, miR-155, and tumour suppressor miR-126 were highly dysregulated in the PDAC cells treated with NiCl2 compared with the control PDAC cells.