Targeting Topoisomerase II Activity in NSCLC with 9-Aminoacridine Derivatives

Etoposide and other type-II human topoisomerase (TOPOII) poisons are widely used for the treatment of many different cancer types, including non-small cell lung cancer (NSCLC). However, there is a risk for the development of therapy-related secondary leukemia following treatment with these TOPOII poisons. Five to seven years is the typical latency period for the development of secondary leukemia. One of the strategies to overcome this issue is to develop agents that do not act as poisons but still effectively inhibit topoisomerase activity. This has led to the development of acridine-based agents, which are catalytic TOPOII inhibitors, that do not generate DNA strand breaks that can lead to secondary malignancies in in vitro tests.

In this study, we showd antiproliferative activity of a series of acridine-based catalytic inhibitors of TOPOII using four NSCLC cell lines (H460, A549, H2009 and H2030). Cells were treated with four acridine-based compounds for 72 h.

The results indicate that these compounds inhibit NSCLC cell proliferation with half-maximal effective concentration (EC50) ranging from 8.15 to 42.09 μM. Combination therapy with cisplatin resulted in increased potency. Poly (ADP-ribose) polymerase cleavage and Guava Nexin assays confirm that the primary mode of cell death was by apoptosis.

This current work is part of a series of studies for this panel of acridine-based compounds bearing TOPOII-inhibitory activity against different solid tumor types. The acridine-based agents were found to substantially reduce NSCLC cell viability and induce apoptosis. In addition, the acridine-based compounds sensitized cells to cisplatin as measured by cell viability. The results are consistent with prior work on mesothelioma, small-cell lung cancer and pancreatic cancer with this same panel of 9-aminoacridine derivatives. These findings support further development of this type of catalytic TOPOII inhibitor as a novel agent for NSCLC therapy.