Half-Sandwich Ru(p-cymene) Compounds with Diphosphanes: In Vitro and In Vivo Evaluation As Potential Anticancer Metallodrugs

[Abstract] Ruthenium(II) complexes are currently considered attractive alternatives to the widely used platinum-based drugs. We present herein the synthesis and characterization of half-sandwich ruthenium compounds formulated as [Ru(p-cymene)(L)Cl][CF3SO3] (L = 1,1-bis(methylenediphenylphosphano)ethylene, 1; L = 1,1-bis(diphenylphosphano)ethylene, 2), which were characterized by elemental analysis, mass spectrometry, 1H and 31P{1H} NMR, UV–vis and IR spectroscopy, conductivity measurements and cyclic voltammetry. The molecular structures for both complexes were determined by single-crystal X-ray diffraction. Their cytotoxic activity was evaluated using the MTT assay against human tumor cells, namely ovarian (A2780) and breast (MCF7 and MDA-MB-231). Both complexes were active against breast adenocarcinoma cells, with complex 1 exhibiting a quite remarkable cytotoxicity in the submicromolar range. Interestingly, at concentrations equivalent to the IC50 values in the MCF7 cancer cells, complexes 1 and 2 presented lower cytotoxicity in normal human primary fibroblasts. The antiproliferative effects of 1 and 2 in MCF7 cells might be associated with the induction of reactive oxygen species (ROS), leading to a combined cell death mechanism via apoptosis and autophagy. Despite the fact that in vitro a partial intercalation between complexes and DNA was observed, no MCF7 cell cycle delay or arrest was observed, indicating that DNA might not be a direct target. Complexes 1 and 2 both exhibited a moderate to strong interaction with human serum albumin, suggesting that protein targets may be involved in their mode of action. Their acute toxicity was evaluated in the zebrafish model. Complex 1 (the most toxic of the two) exhibited a lethal toxicity LC50 value about 1 order of magnitude higher than any IC50 concentrations found for the cancer cell models used, highlighting its therapeutic relevance as a drug candidate in cancer chemotherapy.UDC authors acknowledge the financial support received from the Xunta de Galicia (Galicia, Spain) under the Grupos de Referencia Competitiva Programme: Project ED431C 2018/39 (Quimolmat Group). Portuguese authors acknowledge the Portuguese Foundation for Science and Technology (FCT - Fundação para a Ciência e a Tecnologia) for funding through projects PEst 2015-2020, UID/Multi/04349/2013, RECI/QEQ-QIN/0189/2012, and UIDB/QUI/00100/2020. This work was supported by the Applied Molecular Biosciences Unit - UCIBIO that is financed by national funds from the FCT/MCTES (UID/Multi/04378/2020). A.I.T. acknowledges the FCT, POPH-Programa Operacional Potencial Humano, and FSE-European Social Fund for the IF2013-Initiative and for project IF/01179/2013, as well as COST Action NECTAR (CA18202, European Cooperation in Science and Technology). R.G.T. thanks the FCT for his Ph.D. Grant (SFRH/BD/135830/2018). O.A.L.-R. acknowledges Project LISBOA-01-0145-FEDER-007660 (Microbiologia Molecular, Estrutural e Celular) funded by FEDER funds through COMPETE2020-Programa Operacional Competitividade e Internacionalização (POCI) and by national funds through FCT, POPH-Programa Operacional Potencial Humano, and FSE (European Social Fund) for the CEEC 2017 Initiative. A. Carvalho is also acknowledged for her contribution to the biological data. A.A.-G. acknowledges the Xunta de Galicia (Galicia, Spain) for funding through a predoctoral fellowship. M.S.-M. acknowledges the Ministry of Science, Innovation and University of Spain for funding through a FPU fellowship. D.P.-P. received a postdoctoral fellowship from the National Council of Science and Technology (CONACYT) of MexicoXunta de Galicia; ED431C 2018/39Portugal. Fundação para a Ciência e a Tecnologia; PEst 2015-2020Portugal. Fundação para a Ciência e a Tecnologia; UID/Multi/04349/2013Portugal. Fundação para a Ciência e a Tecnologia; RECI/QEQ-QIN/0189/2012,Portugal. Fundação para a Ciência e a Tecnologia; UIDB/QUI/00100/2020Portugal. Fundação para a Ciência e a Tecnologia; UID/Multi/04378/2020Portugal. Fundação para a Ciência e a Tecnologia; IF/01179/2013Portugal. Fundação para a Ciência e a Tecnologia; SFRH/BD/135830/2018Portugal. Fundação para a Ciência e a Tecnologia; LISBOA-01-0145-FEDER-00766