The Anti-Cancer Effect of Strained Photoactivatable Polypyridyl Ruthenium(II) Complexes on Non-Small-Cell Lung Cancer and Triple Negative Breast Cancer Cells

Abstract

Ruthenium complexes have been recently reported as potential chemotherapeutic agents that offer tumor selectivity and low tumor resistance. Photoactivated chemotherapy consists of introducing a ‘prodrug’ that dissociates into toxic molecules upon light activation. The present study investigates the effect of four synthesized photoactivatable ruthenium II complexes on lung cancer (A549) and breast cancer (MDA-MB-231) cells. These compounds are [Ru(bpy)2dmbpy]Cl2 (C1), [Ru(phen)2dmbpy]Cl2 (C2), [Ru(BP)2dmbpy]Cl2 (C3) and [Ru(BPS)2dmbpy]Na2 (C4). Cultured cancer cells were treated with the above complexes for 12 h and then irradiated with blue light for 30 min. Cell viability was then evaluated using WST-1, 72 hours post treatment. The cellular uptake of various complexes at different time points was assessed using LC-MS/MS. Results showed that upon photoactivation, C3 exhibited the highest cytotoxicity (MDA-MB-231, IC50 = 0.73μM; A549, IC50 = 1.26 μM) which correlated with the high cellular uptake. The phototoxicity indices (IC50 dark/IC50 light) of C3 were 6.56 and 4.64 for MDA-MB-230 and A549 respectively. Determination of the octanol-water partition coefficient (log P) of the various complexes revealed that C3 is the most lipophilic which justifies its high cellular uptake and high cytotoxicity. ROS detection by DCFDA staining showed that upon treatment with C3 and C4, MDA-MB-231 produced high ROS levels that could have initiated cell death. Cytotoxicity against mesenchymal stem cells (MSCs) was assessed on the most effective compound C3 which exhibited minimal toxicity on MSCs in dark (IC50=74 μM vs 4.72 and 6.03 in A549 and MDA-MB-231 respectively) but comparable toxicity to cancer cells in light (0.9 μM). Flow cytometry using Annexin/PI staining revealed a significant increase in early and late apoptotic MDA-MB-231 cells upon treatment with C3. Western blot analysis on MDA-MB-231 cells treated with C3 showed a significant increase in BAX/Bcl2 ratio with no significant effect on Pro-caspase-3 expression. In conclusion, C3 was shown to be a potential selective photoactivatable chemotherapeutic complex that induces apoptosis through a caspase-3 independent intrinsic pathway.