['Cisplatin (CDDP) is a platinum-based drug that is widely used in cancer chemotherapy, but the development of resistance in tumor cells is a major weakness of these treatments. Several mechanisms have been proposed to explain cisplatin resistance, and disruption of certain cellular pathways could modulate drug sensitivity to cisplatin. A lower level of cross-resistance to cisplatin leads to better outcomes in clinical use.', 'Cross-resistance was assessed using cisplatin resistant lung cancer cell line A549/CDDP. Cell cycle analysis was used to examine the effect of cisplatin on cell signaling pathways regulating G2/M transition in cisplatin resistant cells.', 'A549/CDDP cells exhibited cross-resistance to carboplatin, but not oxaliplatin, which is often found in platinum analogues. Flow cytometry showed that nocodazole treatment caused a G2/M block in both A549/CDDP cells and cisplatin susceptible cells. However, A549/CDDP cells escaped the G2/M block following exposure to cisplatin. Activation of the Cdc2/CyclinB complex is required for transition from G2 to M phase, and the inactive form of phosphorylated Cdc2 is activated by Cdc25C dephosphorylation of Tyr15. In the cisplatin-treated susceptible cells, the levels of phosphorylated Cdc2 and Cdc25C were markedly decreased, leading to a loss of Cdc2 activity and G2/M arrest. In A549/CDDP cells, however, Cdc2 activity was supported by the expression of Cdc2 and Cdc25C after the addition of cisplatin, which resulted in G2/M progression.'] Is cisplatin resistance in human lung cancer cells linked with dysregulation of cell cycle associated proteins?