Gene expression response to cisplatin treatment in drug-sensitive and drug-resistant ovarian cancer cells.

The molecular pathways activated in response to acute cisplatin exposure, as well as the mechanisms involved in the long-term development of cisplatin-resistant cancer cells remain unclear. Using whole genome oligonucleotide microarrays, we have examined the kinetics of gene expression changes in a cisplatin-sensitive cell line, A2780, and its cisplatin-resistant derivative, ACRP. Both sensitive and resistant cell lines exhibited a very similar response of p53-inducible genes as early as 16 h after treatment. This p53 response was further increased at the 24-h time point. These experiments identify p53 as the main pathway producing a large-scale transcriptional response after cisplatin treatment in these cells containing wild-type p53. Consistent with a role for the p53 response in cisplatin sensitivity, knockdown of the p53 protein with small interfering RNA led to a twofold decrease in cell survival in the resistant cells. In addition, our analysis also allowed the identification of several genes that are differentially expressed between sensitive and resistant cells. These genes include GJA1 (encoding connexin 43 (Cx43)) and TWIST1, which are highly upregulated in cisplatin-resistant cells. The importance of Cx43 in drug resistance was demonstrated through functional analyses, although paradoxically, inhibition of Cx43 function in high expressing cells led to an increase in drug resistance. The pathways important in cisplatin response, as well as the genes found differentially expressed between cisplatin-resistant and -sensitive cells, may represent targets for therapy aimed at reversing drug resistance.