A Rationally Designed Bimetallic Platinum (II)‐Ferrocene Antitumor Agent Induces Non‐Apoptotic Cell Death and Exertsin VivoEfficacy

Abstract

Despite phenomenal clinical success, the efficacy of platinum anticancer drugs is often compromised due to inherent and acquired drug resistant phenotypes in cancers. To circumvent this issue, we designed two heterobimetallic platinum (II)‐ferrocene hybrids that display multi‐pronged anticancer action. In cancer cells, our best compound, 2, platinates DNA, produces reactive oxygen species, and has nucleus, mitochondria, and endoplasmic reticulum as potential targets. The multi‐modal mechanism of action of these hybrid agents lead to non‐apoptotic cell death induction which enables circumventing apoptosis resistance and significant improvement in platinum cross resistance profile. Finally, in addition to describing detail mechanistic insights, we also assessed its stability in plasma and demonstrate anticancer efficacy in an in vivo A2780 xenograft model. Strikingly, compared to oxaliplatin, our compound displays better tolerability, safety profile and efficacy in vivo.

Potent Ruthenium–Ferrocene Bimetallic Antitumor Antiangiogenic Agent That Circumvents Platinum Resistance: From Synthesis and Mechanistic Studies to In Vivo Evaluation in Zebrafish

“…The cellular uptake and intracellular distribution of various Ru compounds were studied previously using confocal microscopy . However, as 1–6 are non-luminescent, the cellular uptake and intracellular distribution ( vide infra ) of these classes of compounds were assessed using ICP–MS. , The accumulation of 1–6 in HeLa cells (10 μM, 4 h) is summarized in Table . The uptake follows the order 4 > 1 > 2 ∼ 6 > 5 > 3 .…”

“…Mitochondrial damage and/or dysfunction leads to impairment of mitochondrial membrane potential (ΔΨ m ). , To this end, a fluorescent ΔΨ m indicator, namely, 5,5,6,6′-tetrachloro-1,1′,3,3′-tetraethyl-imidacarbocyanine iodide (JC-1) dye, in combination with flow cytometry was used to measure ΔΨ m in 1 -treated HeLa cells. In the case of healthy and functional mitochondria with intact ΔΨ m , the JC-1 dye accumulates in mitochondria as aggregates and is emitted in the red channel, whereas in case of unhealthy mitochondria with depleted ΔΨ m , the JC-1 dye accumulates as monomers inside mitochondria and is emitted in the green channel . It should be noted that since all mechanistic studies were performed in HeLa cells using 24 h incubation assays, the concentrations of 1 for the assays were chosen to be 1/4 × IC 50/24h (10 μM) or 1/2 × IC 50/24h (20 μM) or IC 50/24h (40 μM) based on the IC 50/24h value (38 ± 3 μM) obtained using a 24 h MTT assay (Figure S24).…”

“…We note that in contrast to apoptosis resistance which is caused by a specific mechanism (dysfunctional apoptosis signaling), Pt resistance is caused by multiple simultaneously operating mechanisms such as reduced uptake, enhanced efflux, enhanced DNA repair, and down-regulation of apoptotic proteins . Comparing the potency of our cisplatin-like Pt-Fc-1 in wild-type A2780 and its cisplatin resistant mutant A2780Cis human ovarian cancer cells revealed that the Pt-Fc hybrid has significantly lower Pt cross-resistance (resistance factor, RF = 2.8) compared to its monometallic parent drug cisplatin (RF = 9.7) . The purpose of this study is to design the next generation of multi-targeted hybrid anticancer agents with improved antitumor activity and, importantly, no Pt cross-resistance (expected RF ∼ 1).…”

“…15 Comparing the potency of our cisplatin-like Pt-Fc-1 in wild-type A2780 and its cisplatin resistant mutant A2780Cis human ovarian cancer cells revealed that the Pt-Fc hybrid has significantly lower Pt cross-resistance (resistance factor, RF = 2.8) compared to its monometallic parent drug cisplatin (RF = 9.7). 13 The purpose of this study is to design the next generation of multi-targeted hybrid anticancer agents with improved antitumor activity and, importantly, no Pt cross-resistance (expected RF ∼ 1). As discussed above, encouraged by the lack of Pt cross-resistance of Ru(II)−arene compounds, 8,11,12 we envisaged substituting the [(N−N)Pt(II)] moiety in the Pt-Fc hybrids with a Ru(II)−arene moiety and constructing a bimetallic Ru-Fc hybrid 1 (Figure 1b) that is expected to have no Pt crossresistance in cancer cells.…”

“…Reaction of the [(η 6 -arene)RuCl 2 ] 2 dimer with the appropriate 1,3-diketone derivative in a MeOH/dichloromethane (DCM) mixture in the presence of NaOMe provided 1−6 in 80−90% yield. 12,25 All complexes were characterized by 1 H and 13 C NMR spectroscopies (Figures S1−S12) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (Figure S13). The purity of 1−6 was confirmed to be ≥95% by elemental microanalysis (Experimental Section) and analytical high-performance liquid chromatography HPLC (Figure S14).…”