Photosubstitution in a trisheteroleptic ruthenium complex inhibits conjunctival melanoma growth in a zebrafish orthotopic xenograft model

• Published in: Chemical science (Cambridge) Vol. 13; no. 23; pp. 6899 - 6919
• Main Authors: Chen, Quanchi, Cuello-Garibo, Jordi-Amat, Bretin, Ludovic, Zhang, Liyan, Ramu, Vadde, Aydar, Yasmin, Batsiun, Yevhen, Bronkhorst, Sharon, Husiev, Yurii, Beztsinna, Nataliia, Chen, Lanpeng, Zhou, Xue-Quan, Schmidt, Claudia, Ott, Ingo, Jager, Martine J, Brouwer, Albert M, Snaar-Jagalska, B. Ewa, Bonnet, Sylvestre
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 15.06.2022; The Royal Society of Chemistry
• Subjects: Anticancer properties; Apoptosis; Biocompatibility; Cancer therapies; Chemistry; Embryos; Fluorescence; In vivo methods and tests; Lesions; Ligands; Light irradiation; Melanoma; Prostate; Ruthenium compounds; Spheroids; Tumors; Xenotransplantation; Zebrafish
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d2sc01646j

In vivo data are rare but essential for establishing the clinical potential of ruthenium-based photoactivated chemotherapy (PACT) compounds, a new family of phototherapeutic drugs that are activated via ligand photosubstitution. Here a novel trisheteroleptic ruthenium complex [Ru(dpp)(bpy)(mtmp)](PF 6 ) 2 ([ 2 ](PF 6 ) 2 , dpp = 4,7-diphenyl-1,10-phenanthroline, bpy = 2,2′-bipyridine, mtmp = 2-methylthiomethylpyridine) was synthesized and its light-activated anticancer properties were validated in cancer cell monolayers, 3D tumor spheroids, and in embryonic zebrafish cancer models. Upon green light irradiation, the non-toxic mtmp ligand is selectively cleaved off, thereby releasing a phototoxic ruthenium-based photoproduct capable notably of binding to nuclear DNA and triggering DNA damage and apoptosis within 24-48 h. In vitro , fifteen minutes of green light irradiation (21 mW cm −2 , 19 J cm −2 , 520 nm) were sufficient to generate high phototherapeutic indexes (PI) for this compound in a range of cancer cell lines including lung (A549), prostate (PC3Pro4), conjunctival melanoma (CRMM1, CRMM2, CM2005.1) and uveal melanoma (OMM1, OMM2.5, Mel270) cancer cell lines. The therapeutic potential of [ 2 ](PF 6 ) 2 was further evaluated in zebrafish embryo ectopic (PC3Pro4) or orthotopic (CRMM1, CRMM2) tumour models. The ectopic model consisted of red fluorescent PC3Pro4-mCherry cells injected intravenously (IV) into zebrafish, that formed perivascular metastatic lesions at the posterior ventral end of caudal hematopoietic tissue (CHT). By contrast, in the orthotopic model, CRMM1- and CRMM2-mCherry cells were injected behind the eye where they developed primary lesions. The maximally-tolerated dose (MTD) of [ 2 ](PF 6 ) 2 was first determined for three different modes of compound administration: (i) incubating the fish in prodrug-containing water (WA); (ii) injecting the prodrug intravenously (IV) into the fish; or (iii) injecting the prodrug retro-orbitally (RO) into the fish. To test the anticancer efficiency of [ 2 ](PF 6 ) 2 , the embryos were treated 24 h after engraftment at the MTD. Optimally, four consecutive PACT treatments were performed on engrafted embryos using 60 min drug-to-light intervals and 90 min green light irradiation (21 mW cm −2 , 114 J cm −2 , 520 nm). Most importantly, this PACT protocol was not toxic to the zebrafish. In the ectopic prostate tumour models, where [ 2 ](PF 6 ) 2 showed the highest photoindex in vitro (PI > 31), the PACT treatment did not significantly diminish the growth of primary lesions, while in both conjunctival melanoma orthotopic tumour models, where [ 2 ](PF 6 ) 2 showed more modest photoindexes (PI ∼ 9), retro-orbitally administered PACT treatment significantly inhibited growth of the engrafted tumors. Overall, this study represents the first demonstration in zebrafish cancer models of the clinical potential of ruthenium-based PACT, here against conjunctival melanoma. A new tris-heteroleptic photoactivated chemotherapy ruthenium complex induces apoptosis upon green light activation in a zebrafish orthothopic conjunctival melanoma xenograft model.