Positive tetracycline control of expression of p15INK4B from an Epstein-Barr autonomous plasmid in a human melanoma cell line

Homozygous deletions in the region of chromosome 9p21 are frequent in human melanoma. Mutations in the p16INK4A cyclin-dependent kinase inhibitor (CDI ) gene at this locus have implicated the product of this gene as a tumor su ppressor. Less attention has been focused on the homologous, closely linked p15INK4B gene. To facilitate study of the phenotypic effects of restoring expression of the latter in aggressive melanoma cells lacking INK4 expressi on, we inserted the cDNA encoding p15INK4B into an autonomously maintained plasmid under positive tetracycline control ('TET ON' system). Similarly re gulated luciferase and herpes thymidine kinase sequences were used as contr ols. We demonstrate that this system enabled efficient, and reasonably unif orm, induction of p15INK4B expression in a human melanoma cell line exposed to the tetracycline derivative, doxycycline, Flow cytometry showed that th is induction resulted in substantial accumulation of cells in the G0/G1 pha se of the cell cycle. This system will facilitate detailed analysis of the cell cycle inhibitory mechanisms of this CDI in human melanoma cells. (C) 2 000 Elsevier Science B.V. All rights reserved.