2D-DIGE analysis of ovarian cancer cell responses to cytotoxic gold compounds

Cytotoxic gold compounds hold today great promise as new pharmacological agents for treatment of human ovarian carcinoma; yet, their mode of action is still largely unknown. To shed light on the underlying molecular mechanisms, we performed 2D-DIGE analysis to identify differential protein expression in a cisplatin-sensitive human ovarian cancer cell line (A2780/S) following treatment with two representative gold(III) complexes that are known to be potent antiproliferative agents, namely AuL12 and Au2Phen. Software analysis using DeCyder was performed and few differentially expressed protein spots were visualized between the three examined settings after 24 h exposure to the cytotoxic compounds, implying that cellular damage at least during the early phases of exposure is quite limited and selective, reflecting the attempts of the cell to repair damage and to survive the insult. The potential of novel proteomic methods to disclose mechanistic details of cytotoxic metallodrugs is herein further highlighted. Different patterns of proteomic changes were highlighted for the two metallodrugs with only a few perturbed protein spots in common. Using MALDI-TOF MS and ESI-Ion trap MS/MS, several differentially expressed proteins were identified. Two of these were validated by western blotting: Ubiquilin-1, responsible for inhibiting degradation of proteins such as p53 and NAP1L1, a candidate marker identified in primary tumors. Ubiquilin-1 resulted over-expressed following both treatments and NAP1L1 was down-expressed in AuL12-treated cells in comparison with control and with Au2Phentreated cells. In conclusion, we performed a comprehensive analysis of proteins regulated by AuL12 and Au2Phen, providing a useful insight into their mechanisms of action.