Episome generated C-myc antisense RNA inhibits growth and tumorigenicity of a human neuroendocrine tumor-cell line.

The neuroepithelioma cell line CHP100 expresses low but detectable amounts of N-myc protein together with large amounts of c-myc protein. We have recently demonstrated that antisense inhibition of N-myc expression in CHP100 cells leads to decreased in vitro growth and alterations in cellular morphology without affecting tumorigenicity in nude mice. In this study we report the construction of an episomally replicating vector designed to generate RNA antisense to part of the human c-myc gene. Such a Vector is able to inhibit c-myc expression in cell lines carrying multiple copies of the gene. Inhibition of c-myc expression leads to a decrease of in vitro growth and cloning efficiency and in vivo tumorigenicity of CHP100 cells. Our findings suggest that N-myc and c-myc subserve different functions in regulating the biology of CHP100 cells.