Valproic acid alters the content and function of the cell-free DNA released by hepatocellular carcinoma (HepG2) cells in vitro.

Background: It has long been believed that cell-free DNA (cfDNA) actively released into circulation can serve as intercellular messengers, and their involvement in processes such as the bystander effect strongly support this. However, this intercellular messaging function of cfDNA may have clinical implications that have not yet been considered.

Methods: CfDNA was isolated from the growth medium of HepG2 cells treated with valproic acid (VPA). This cfDNA was then administered to untreated cells and cellular metabolic activity was measured.

Results: VPA altered the characteristics of cfDNA released by treated HepG2 cells in vitro. When administered to untreated cells, the cfDNA from cells treated with VPA resulted in the dose-dependent induction of glycolytic activity within 36 min of administration, but little to no alterations in oxidative phosphorylation. The glycolytic activity lasted for 4-6 h, whereas changes in subsequent cfDNA release and characteristics were found to remain persistent after two 24 h treatments. Fragmented genomic DNA from VPA-treated cells did not induce the effects observed for cfDNA obtained VPA-treated cells.

Conclusions: It is possible for cfDNA to, under in vitro conditions, transfer pharmaceutically-induced effects to untreated recipient cells. Further investigation regarding this occurrence under in vivo conditions is, therefore, strongly encouraged.

General Significance: The intercellular messaging functions of cfDNA present in donated biological fluids has potential clinical implications that require urgent attention. These implications may, however, also have potential as new forms of treatment that can circumvent pharmacological barriers.