Because of a critical shortage in suitable organs, many patients with terminal liver disease die each year before liver transplantation can be performed. Transplantation of isolated hepatocytes has been proposed for the temporary metabolic support of patients awaiting liver transplantation or spontaneous reversion of their liver disease. A major limitation of this form of therapy is the present inability to isolate an adequate number of transplantable hepatocytes. A highly differentiated cell line, NKNT-3, was generated by retroviral transfer in normal primary adult human hepatocytes of an immortalizing gene that can be subsequently and completely excised by Cre/Lox site-specific recombination. When transplanted into the spleen of rats under transient immunosuppression, reversibly immortalized NKNT-3 cells provided life-saving metabolic support during acute liver failure induced by 90% hepatectomy.

The pancreatic and duodenal homeobox factor-1 (PDX-1), also known as IDX-1/STF-1/IPF1, a homeodomain-containing transcription factor, plays a central role in regulating pancreatic development and insulin gene transcription. Furthermore, even in adults, PDX-1 is associated with islet neogenesis and differentiation of insulin-producing cells from progenitor cells. Here, we report for the first time that PDX-1 protein can permeate cells due to an Antennapedia-like protein transduction domain sequence in its structure and that transduced PDX-1 functions similarly to endogenous PDX-1; it binds to the insulin promoter and activates its expression. PDX-1 protein can also permeate into isolated pancreatic islets, which leads to stimulation of insulin gene expression. Moreover, PDX-1 protein transduced into cultures of pancreatic ducts, thought to be islet progenitor cells, induces insulin gene expression. These data suggest that PDX-1 protein transduction could be a safe and valuable strategy for enhancing insulin gene transcription and for facilitating differentiation of ductal progenitor cells into insulin-producing cells without requiring gene transfer technology.