depend on the promoter. what promoter are you using?

Not only the beta cells of pancreas produce insulin. But in some critical factor cell like our immune cell, pluripotent stem cells or fetal or adult cell type which produces insulin and also cell like epithelial cells or mesodermal cell or endodermal cell are able to secreting insulin.

you can clone insulin gene into a expression vector driven by ubiquitous promoter, such as EF1-alpha, CMV, etc. and then, insulin can be expressed at any mammalian cells after you transfect your vector into the cells.

Gang Zhang, University of Toronto