The dual-acting chemotherapeutic agent Alchemix induces cell death independently of ATM and p53

Abstract

Topoisomerase inhibitors are in common use as chemotherapeutic agents although they can display reduced efficacy in chemotherapy-resistant tumours, which have inactivated DNA damage response genes, such as ATM and TP53. Here, we characterize the cellular response to the dual-acting agent, Alchemix (ALX), which is a modified anthraquinone that functions as a topoisomerase inhibitor as well as an alkylating agent. We show that ALX induces a robust DNA damage response at nano-molar concentrations and this is mediated primarily through ATR-and DNA-PK-but not ATM-dependent pathways, despite DNA double strand breaks being generated after prolonged exposure to the drug. Interestingly, exposure of epithelial tumour cell lines to ALX in vitro resulted in potent activation of the G2/M checkpoint, which after a prolonged arrest was bypassed allowing cells to progress into mitosis where they ultimately died by mitotic catastrophe. We also observed effective killing of lymphoid tumour cell lines in vitro following exposure to ALX, although, in contrast, this tended to occur via activation of a p53-independent apoptotic pathway. Lastly, we validate the effectiveness of ALX as a chemotherapeutic agent in vivo by demonstrating its ability to cause a significant reduction in tumour cell growth, irrespective of TP53 status, using a mouse leukaemia xenograft model.Taken together, these data demonstrate that ALX, through its dual action as an alkylating agent and topoisomerase inhibitor, represents a novel anti-cancer agent that could be potentially used clinically to treat refractory or relapsed tumours, particularly those harbouring mutations in DNA damage response genes.

Mitoxantrone and Analogues Bind and Stabilize i-Motif Forming DNA Sequences

“…To see whether it was possible to gain higher specificity for i-motif over double helical DNA, we decided to investigate the stabilisation capabilities of analogue compounds. Previous studies using analogues of mitoxantrone allowed easy access to a mixture of both known and novel structures2627282930. An initial screen of 25 analogues was performed (Fig.…”

Alchemix, p53 and topoisomerase

“…This mechanism of resistance has been associated with other tumour types in addition to ovarian cancer. The ability of Alchemix to cause regression of these tumours in vivo is consistent with its ability to elicit a potent DDR in MSH-depleted cells [ 7 ] or cells over-expressing the MDR1 gene.…”

“…In a recent publication the mode of action of Alchemix has been described in detail [ 7 ]. The drug is capable of inducing a DDR at nanomolar concentrations and this is due to activation of ATR- and DNA-PK-dependent pathways.…”

Perspectives in the development of hybrid bifunctional antitumour agents

“…Due to the incorporation of an alkylating function, the genotoxic stress is expected to be more persistent and less susceptible to repair [11]. The induction of irreparable damage is consistent with the activity of Alchemix against anthracycline-resistant and platinum-resistant ovarian carcinoma models and the induction of cell death via activation of a p53-independent apoptotic pathway [12]. This compound, characterized by intercalating and alkylating properties, preferentially induces the formation of a covalently bound topo IIalpha-drug-DNA ternary complex, but does not stabilize a topo IIbeta-DNA complex.…”