Immortalized bovine pancreatic duct cells become tumorigenic after transfection with mutant k-ras

Mutation of the K-ras gene is thought to be an early and important event in pancreatic carcinogenesis. In order to study the role of this molecular al teration in the transition from the normal to the neoplastic pancreatic cel l, bovine pancreatic duct cells were first immortalized by SV40 large T ant igen (Ag) complementary (c)DNA transfection and then transfected with a mut ated K-ras gene. As did primary duct cells, the immortalized duct cells (mo re than 100 passages) expressed cytokeratins, carbonic anhydrase type-II, c ystic fibrosis transmembrane conductance regulator (CFTR), and multidrug re sistance (mdr). They grew as a single layer after transplantation under pla stic domes and formed three-dimensional structures resembling ducts when gr own on Matrigel. Cell growth was stimulated by insulin, epidermal growth fa ctor (EGF), transforming growth factor (TGF)-alpha, but cells did not respo nd to gastrin and CCK-8. They did not form colonies in soft agar nor did th ey form tumors in nude mice. Immortalized cells transfected with mutated K- ras acquired the ability to form tumors after orthotopic injection into the nude mouse pancreas. It is concluded that SV 40 immortalized bovine pancre atic duct cells retain the features of normal duct cells and gain tumorigen icity by transfection with mutated K-ras. This suggests an important role f or K-ras in this pancreatic carcinoma model.