Transcription factor expression and hormone production in pancreatic AR42Jcells

AR42J is an exocrine pancreatic cell line that has been reported to differe ntiate towards an endocrine phenotype when stimulated with various growth f actors, such as activin A, hepatocyte growth factor (HGF), betacellulin or glucagon-like peptide 1. In our experiments, AR42J-B13 cells differentiated morphologically in response to the growth factor treatment as reported pre viously. However, they failed to express the insulin gene. We found that th e cells did not express several transcription factors known to be found in the beta-cell, including Nkx6.1, isl-1, Pax4 and Pax6. In addition, the mRN A level for pdx-1 and Nkx2.2 were very low in comparison to the insulinoma cell lines INS-1 and RINm5F. However, some transcription factors typically found in beta-cells and neuroendocrine cells were expressed also in the AR4 2J-B13 cells. These included BETA2/NeuroD, HNF1 alpha, C/EBP beta and IA-1. Unlike the insulinoma cells, AR42J cells expressed the exocrine transcript ion factor p48. In order to induce endocrine differentiation, we transfecte d the AR42J-B13 cells with the full length cDNAs of isl-1, Nkx6.1, Nkx2.2 a nd pdx-1 under the control of the CMV promoter, both separately and in comb inations. The expression of Nkx2.2 led consistently to the appearance of pa ncreatic polypeptide but not insulin, glucagon or somatostatin mRNA. The PP mRNA expression in Nkx2.2 cDNA transfected cells was independent of the gr owth factor treatment used for differentiating AR42J cells. In conclusion, the AR42J-B13 line possesses some features of a pancreatic neuroendocrine c ell. However, we were unable to confirm the capacity of these cells to diff erentiate into insulin-producing cells. Our results indicate that Nkx2.2 pl ays a role in the transcriptional regulation of PP expression. (C) 2000 Els evier Science Ireland Ltd. All rights reserved.