Oncogenic transformation and the reductions of insulin secretion and proliferative calcium dependence during repeated passage of pancreatic islet cells in vitro

Islet cells were isolated from 2 fetal bovine pancreas glands and cultivated in vitro. During the course of repeated passage in vitro, the B-cells in these cultures retained the ability to synthesize insulin, but rapidly lost the ability to secrete it. The cells also became progressively more able to proliferate in calcium-deficient medium which did not support the proliferation of cells from primary cultures. The reductions of insulin secretion and proliferative calcium dependence were accompanied by the acquisition of the ability to produce tumors in nude mice.