CLONAL INSULINOMA CELL-LINE THAT STABLY MAINTAINS CORRECT GLUCOSE RESPONSIVENESS

A number of pancreatic beta-tumor cell (beta TC) lines have been deriv ed from insulinomas arising in transgenic mice expressing the SV40 T a ntigen gene under control of the insulin promoter. Some of these lines secrete insulin in response to physiological glucose concentrations. However, this phenotype is unstable. After propagation in culture, the se nonclonal lines become responsive to subphysiological glucose level s and/or manifest reduced insulin release. Here we report the use of s oft-agar cloning to isolate single-cell clones from a beta TC line, wh ich give rise to sublines that maintain correct glucose responsiveness and high insulin production and secretion for >55 passages (over a ye ar) in culture. One of these clonal lines, denoted beta TC6-F7, was ch aracterized in detail. beta TC6-F7 cells expressed high glucokinase an d low hexokinase activity, similarly to normal islets. In addition, th ey expressed mRNA for the GLUT2 glucose transporter isotype and no det ectable GLUT1 mRNA, as is characteristic of normal <beta-cells. These results demonstrate that transformed beta-cells can maintain a highly differentiated phenotype during prolonged propagation in culture, whic h has implications for the development of continuous beta-cell lines f or transplantation therapy of diabetes.