Organometallics, such as copper compounds, are cancer chemotherapeutics used alone or in combination with other drugs. One small group of copper complexes exerts an effective inhibitory action on topoisomerases, which participate in the regulation of DNA topology. Copper complexes inhibitors of topoisomerases 1 and 2 work by different molecular mechanisms, analyzed herein. They allow genesis of DNA breaks after the formation of a ternary complex, or act in a catalytic mode, often display DNA intercalative properties and ROS production, and sometimes display dual effects. These amplified actions have repercussions on the cell cycle checkpoints and death effectors. Copper complexes of topoisomerase inhibitors are analyzed in a broader synthetic view and in the context of cancer cell mutations. Finally, new emerging treatment aspects are depicted to encourage the expansion of this family of highly active anticancer drugs and to expend their use in clinical trials and future cancer therapy.

Cells respond to genotoxic stress through a series of complex protein pathways called DNA damage response (DDR). These monitoring mechanisms ensure the maintenance and the transfer of a correct genome to daughter cells through a selection of DNA repair, cell cycle regulation, and programmed cell death processes. Canonical or non-canonical DDRs are highly organized and controlled to play crucial roles in genome stability and diversity. When altered or mutated, the proteins in these complex networks lead to many diseases that share common features, and to tumor formation. In recent years, technological advances have made it possible to benefit from the principles and mechanisms of DDR to target and eliminate cancer cells. These new types of treatments are adapted to the different types of tumor sensitivity and could benefit from a combination of therapies to ensure maximal efficiency.

Topoisomerases are interesting targets in cancer chemotherapy. Here, we describe the design and synthesis of a novel copper(II) indenoisoquinoline complex, WN198. The new organometallic compound exhibits a cytotoxic effect on five adenocarcinoma cell lines (MCF-7, MDA-MB-231, HeLa, HT-29, and DU-145) with the lowest IC₅₀ (0.37 ± 0.04 μM) for the triple-negative MDA-MB-231 breast cancer cell line. Below 5 µM, WN198 was ineffective on non-tumorigenic epithelial breast MCF-10A cells and Xenopus oocyte G2/M transition or embryonic development. Moreover, cancer cell lines showed autophagy markers including Beclin-1 accumulation and LC3-II formation. The DNA interaction of this new compound was evaluated and the dose-dependent topoisomerase I activity starting at 1 μM was confirmed using in vitro tests and has intercalation properties into DNA shown by melting curves and fluorescence measurements. Molecular modeling showed that the main interaction occurs with the aromatic ring but copper stabilizes the molecule before binding and so can putatively increase the potency as well. In this way, copper-derived indenoisoquinoline topoisomerase I inhibitor WN198 is a promising antitumorigenic agent for the development of future DNA-damaging treatments.

Xenopus oocytes were used as cellular and molecular sentinels to assess the effects of a new class of organometallic compounds called ferrocenyl dihydroquinolines that have been developed as potential anti-cancer agents. One ferrocenyl dihydroquinoline compound exerted deleterious effects on oocyte survival after 48 h of incubation at 100 μM. Two ferrocenyl dihydroquinoline compounds had an inhibitory effect on the resumption of progesterone induced oocyte meiosis, compared to controls without ferrocenyl groups. In these inhibited oocytes, no MPF (Cdk1/cyclin B) activity was detected by western blot analysis as shown by the lack of phosphorylation of histone H3. The dephosphorylation of the inhibitory Y15 residue of Cdk1 occurred but cyclin B was degraded. Moreover, two apoptotic death markers, the active caspase 3 and the phosphorylated histone H2, were detected. Only 7-chloro-1-ferrocenylmethyl-4-(phenylylimino)-1,4-dihydroquinoline (8) did not show any toxicity and allowed the assembly of a histologically normal metaphase II meiotic spindle while inhibiting the proliferation of cancer cell lines with a low IC₅₀, suggesting that this compound appears suitable as an antimitotic agent.

The role of hydrogen sulfide (H₂S) is addressed in Xenopus laevis oocytes. Three enzymes involved in H₂S metabolism, cystathionine β-synthase, cystathionine γ-lyase, and 3-mercaptopyruvate sulfurtransferase, were detected in prophase I and metaphase II-arrested oocytes and drove an acceleration of oocyte meiosis resumption when inhibited. Moreover, meiosis resumption is associated with a significant decrease in endogenous H₂S. On another hand, a dose-dependent inhibition was obtained using the H₂S donor, NaHS (1 and 5 mM). NaHS impaired translation. NaHS did not induce the dissociation of the components of the M-phase promoting factor (MPF), cyclin B and Cdk1, nor directly impacted the MPF activity. However, the M-phase entry induced by microinjection of metaphase II MPF-containing cytoplasm was diminished, suggesting upstream components of the MPF auto-amplification loop were sensitive to H₂S. Superoxide dismutase and catalase hindered the effects of NaHS, and this sensitivity was partially dependent on the production of reactive oxygen species (ROS). In contrast to other species, no apoptosis was promoted. These results suggest a contribution of H₂S signaling in the timing of amphibian oocytes meiosis resumption.

Mécanisme d'action d'un nouveau composé organométallique inhibiteur des topoisomérases I d’adénocarcinomes: Les topoisomérases sont les cibles d'inhibiteurs en chimiothérapie induisant une accumulation de dommages à l'ADN, conduisant à la mort cellulaire. Un nouveau composé d'indénoisoquinoline cuivré a été synthétisé (WN197). Son activité et son mécanisme d'action ont été déterminés sur trois lignées d'adénocarcinomes humains. WN197 est cytotoxique à des concentrations inférieures à 0,5 µM sur les lignées cancéreuses MDA-MB-231 (sein), HeLa (col de l'utérus) et HT-29 (côlon). À ces doses, WN197 inhibe les topoisomérases I. À des doses plus élevées (>1 µM), il inhibe les topoisomérases IIα et IIβ et possède des propriétés intercalantes. Les dommages à l'ADN sont détectés par la présence de γH2AX, et La phosphorylation d'ATM/ATR et des kinases Chk1/2 et l'augmentation des quantités de p53 et p21 démontrent l'activation du DDR dans les trois lignées. WN197 provoque un arrêt des cellules en phase G2 caractérisé par le maintien de Cdk1 inactif dû à l'association de Cdc25C à 14.3.3, et par la forme non-phosphorylée de l'histone H3. Les cellules cancéreuses meurent par autophagie avec une accumulation de Beclin-1, la formation de LC3-II, la dégradation de p62 et la phosphorylation de RAPTOR dans le complexe mTOR. WN197 s'avère cytotoxique sur des cellules H69AR « multi-drug resistant », avec un IC50 inférieur à 0,7 µM, et possède un IC50 supérieur à 1 µM sur une lignée du sein non-tumorigénique, et ne se révèle pas toxique pour des ovocytes de Xénopes et leur développement embryonnaire. En inhibant les topoisomérases I à faible concentration avec une forte efficacité, WN197 est un agent prometteur pour le développement de futures chimiothérapies ciblant l'ADN.