Role of reactive oxygen species (ROS) in chemotherapy-induced RNA disruption in tumour cell lines

Abstract

Cancer patients undergoing chemotherapy treatment often suffer from toxic side effects of the drugs used to fight their cancers. Cardiac dysfunction, lung damage, neuropathy and cognitive impairment are just some of the common late effects associated with chemotherapeutic drugs. It is clinically important to have tools that can assess tumour response early in treatment to enhance survival benefit and reduce toxicity in cancer patients. We have observed that a variety of chemotherapy agents can induce ribosomal RNA degradation, also known as RNA disruption within tumour cells. Clinical studies have demonstrated an association between high levels of tumour RNA disruption during chemotherapy with improved disease-free survival and appeared to be more predictive than the standard measure of pathologic complete response (pCR). A company (RNA Diagnostics Inc.) is seeking to bring the RNA disruption assay (RDA) into clinical use as a chemo-response assessment tool. The RDA has the capability to help health care providers identify A) patients not responding to a specific chemotherapy treatment earlier in treatment permitting a change to potentially more effective chemotherapeutics, or B) patients responding well to the current chemotherapeutic treatment who could benefit from dose de-escalation. Numerous chemotherapy drugs have been shown to induce reactive oxygen species (ROS) by disrupting mitochondrial function, or through mitochondria-independent processes. Our general objective is to gain a better mechanistic understanding of the processes that underlie chemotherapy agent-induced RNA disruption. In this study, we assessed a variety of structurally and mechanistically distinct chemotherapy agents for their ability to generate ROS and examined whether this correlates with their capacity to induce RNA disruption in tumour cell lines. We also then assessed whether the addition of an antioxidant agent would allow for inhibition of ROS in the tumour cell lines and whether or not that would reduce the drugs’ ability to induce RNA disruption. In both A2780 and MDA-MB-231 cells, ROS was induced by a variety of chemotherapy agents, including DOX. Once these chemotherapy agents were combined with either NAC or vitamin C antioxidants, these antioxidants reduced RNA disruption most strongly in DOX-treated A2780 cells compared to other chemotherapy agents. However, the inhibition of ROS via scavenging agents appeared to be strongly dependent on 1) the location of which the scavenging agent localizes within the cell; and 2) the different mechanisms involved with each of the chemotherapy agents studied. Collectively, this study has provided a significant and substantial amount of information regarding the mechanisms involved in RNA disruption by multiple chemotherapy agents that can possibly contribute to the development of more specific therapeutics to enhance clinical effectiveness of drugs.