NORMAL RAT INTESTINAL-CELLS IEC-18 - CHARACTERIZATION AND TRANSFECTION WITH IMMORTALIZING ONCOGENES

IEC-18 cells, a cell line derived from the ileum of rat intestine, hav e the characteristics of normal cells since they have a contact inhibi ted cell growth, do not form colonies in soft agar and are not tumorig enic when injected in nude mice. IEC-18 cells were transfected with nu clear oncogenes, c-myc, v-myc and SV40 T antigen in order to obtain im mortal cell lines. Independent clones were isolated and characterized for the growth properties. Expression of v-myc altered the morphology of the cells and shortened the doubling time. A slow growth together w ith a low cloning efficiency was associated with the expression of SV4 0 T antigen. No changes either in growth or in morphology were observe d in c-myc-expressing IEC-18 cells. Expression of these nuclear oncoge nes did not result in the neoplastic transformation of the IEC-18 cell s, since none of the clones lost the anchorage dependence or were able to form tumors in vivo. The c-myc-containing IEC-18 cells were unable to secrete in the growth medium TGF alpha and exposure to TGF beta in hibited the growth rate by 30%. All these observations are consistent with the conclusion that the expression of nuclear oncogenes does not lead to the neoplastic transformation of these cells.