Revisiting [PtCl2(cis-1,4-DACH)]: an underestimated antitumor drug with potential application to the treatment of oxaliplatin-refractory colorectal cancer

Although the encouraging antitumor activity of [PtCl2(cis-1,4-DACH)] (1; DACH = diaminocyclohexane) was shown in early studies almost 20 years ago, the compound has remained nearly neglected. In contrast, oxaliplatin, containing isomeric 1R,2R-DACH carrier ligand, enjoys worldwide clinic application as a most important therapeutic agent in the treatment of colorectal cancer. By extending the investigation to human chemo-resistant cancer cells, we have demonstrated the real effectiveness of 1 in circumventing cisplatin and oxaliplatin resistance in LoVo colon cancer cells. The uptake of compound 1 by the latter cells was similar to that of sensitive LoVo cells. This is not the case for all other compounds considered in this investigation. Interaction with ds-DNA, investigated by a biosensor assay and by QM/MM geometry optimization of the 1,2-GG intrastrand cross-link, does not show significant differences between 1 and oxaliplatin. However, the DNA adducts of 1 are removed from repair systems with lower efficiency and are more effective in inhibiting DNA and RNA polymerase