Methods for generating pancreatic stem cells from a pancreatic tissue of 24-week old mice by transient overexpression of reprogramming factors combined with Pdx1 selection is described herein. The generated cells were designated as iPaS (induced pancreatic stem) cells and exhibit the same morphology as the pancreatic stem cells previously established from young donors without genetic manipulation and express genetic markers of endoderm and pancreatic progenitors. Transplantation of the iPaS cells into nude mice resulted in no teratoma formation. Moreover, iPaS cells were able to differentiate into insulin-producing cells more efficiently than ES cells. In addition, the technology of transient overexpression of reprogramming factors and tissue-specific selection of the present invention may also be useful for the generation of other tissue-specific stem cells.