Recent studies have demonstrated that adult cells such as pancreatic exocrine cells can be converted to pancreatic beta-cells in a process called cell reprogramming. Enteroendocrine cells and beta-cells share similar pathways of differentiation during embryonic development. Notably, enteroendocrine K cells express many of the key proteins found in beta-cells. Thus, K cells could be reprogrammed to beta-cells under certain conditions. However, there is no clear evidence on whether these cells convert to beta-cells. K cells were selected from STC-1 cells, an enteroendocrine cell line expressing multiple hormones. K cells were found to express many genes of transcription factors crucial for islet development and differentiation except for Nkx6.1 and Neurogenin3. A K cell clone stably expressing Nloc6.1 (Nloc6.1(+)-K cells) was established. Induction of Neurogenia3 expression in Nkx6.1(+)-K cells, by either treatment with a gamma-secretase inhibitor or infection with a recombinant adenovinis expressing Neurogenin3, led to a significant increase in Insulin1 mRNA expression. After infection with the adenovirus expressing Neurogenin3 and reaggregation in suspension culture, about 50% of Nkx6.1(+)-K cells expressed insulin as determined by immunostaining. The intracellular insulin content was increased markedly. Electron microscopy revealed the presence of insulin granules. However, glucose-stimulated insulin secretion was defective, and there was no glucose lowering effect after transplantation of these cells in diabetic mice. In conclusion, we demonstrated that K cells could be reprogrammed partially to beta-cells through the combined expression of Nkx6.1 and Neurogenin3, and reaggregation in suspension culture. (C) 2013 Elsevier Inc. All rights reserved.