Abstract: OBJECTIVE: Quinocetone induced S phase arrest，caused DNA and chromosome damage in HepG2 cells. Our purpose was to screen and analyse the mechanism of S phase arrest induced by Quinocetone. METHODS： The Agilent whole genome gene expression microarray was used to detect gene expression profile of HepG2 cells treated and untreated with Quinocetone. Futhermore，pathway analysis by Genespring software was carried out based on the differentially expressed genes，real time qPCR was used to verify some dramatically changed genes in DNA replication process. RESULTS：1 750 differentially expressed genes，with 446 genes up-regulated and 1 304 genes down-regulated，were found in HepG2 cells treated with Quinocetone in the total of 41 000 oligonucleotide fragments. Pathway analysis revealed that the differentially expressed genes gathered in functional pathways like cell cycle checkpoint，MAPK signaling pathway，DNA replication and DNA repair，etc. Moreover，the results of real time qPCR focused on the changed DNA replication genes were consistent with cDNA microarray. CONCLUSION：The down- regulation of DNA replication genes caused incomplete DNA synthesis，and the DNA repair after its damage. These two events lead to S phase arrest after Quinocetone treatment. Moreover，the whole genome cDNA microarray analysis provided us much useful information for further research on the mechanism of S phase arrest induced by Quinocetone.

Key words: quinocetone, HepG2 cells, S phase arrest, cDNA microarray