Antitumor Activities for Two Pt(II) Complexes of Tropolone and 8-Hydroxyquinoline Derivative

The reactions of cis-Pt(DMSO)₂Cl₂ and tropolone (HL) with 8-hydroxyquinoline (HQ) or 2-methyl-8-hydroxyquinoline (HMQ) gave [Pt(Q)(L)] (1) and [Pt(MQ)(L)] (2), which present mononuclear structures with their Pt(II) ions four-coordinated in square planar geometries. Their in vitro biological properties were evaluated by MTT assay, which showed a remarkable cytotoxic activity on the cancer cell lines. 1 shows higher cytotoxic activities on tumor cells such as T24, HeLa, A549, and NCI-H460 than complex 2 and cisplatin, with IC₅₀ values <16 μM. Among them, an IC₅₀ value of 3.6 ± 0.63 μM was found for complex 1 against T24 cells. It presented a tuning cytotoxic activity by substitution groups on 8-hydroxyquinoline skeleton. In our case, the substitution groups of -H are much superior to -CH₃ against tumor cells. It revealed that both complexes can induce cell apoptosis by decreasing the potential of a mitochondrial membrane, enhancing reactive oxygen species and increasing Ca²⁺ levels of T24 cells. The T24 cell cycle can be arrested at G2 and G1 phases by complexes 1 and 2, respectively, with an upregulation for P21 and P27 expression levels and a down-regulation for cyclin A, CDK1, Cdc25A, and cyclin B expression levels. Furthermore, complex 1 exhibits satisfactory in vivo antitumor activity as revealed by the tumor inhibitory rate and the tumor weight change as well as by the cute toxicity assay and renal pathological examinations, which is close to cisplatin and much better than complex 2. All of these suggest that 1 might be a potential candidate for developing into a safe and effective anticancer agent.