Chronic myeloid leukemia (CML) accounts for approximately 14% of newly diagnosed cases of leukemia in adults [1]. The advent of tyrosine kinase inhibitors (TKIs), such as imatinib, since the 2000s has dramatically improved the clinical outcome of patients with CML [2]. However, resistance to imatinib and second-generation TKIs often makes it challenging to continue long-term therapy [2,3]. Ponatinib, the only approved third-generation TKI for CML treatment, has limited clinical utility due to its toxic effects [4]. Thus, many patients with CML do not benefit from TKI treatment because of drug intolerance or drug resistance [5]. Therefore, there is an urgent clinical need to explore and develop alternative therapeutic drugs or strategies, and identifying potential new drugs that possess novel mechanisms of action for the treatment of CML is the primary priority.

Identifying potential new drugs from natural products is a promising strategy for anticancer drug innovation. Anisomeles indica (L.) Kuntze (Labiatae) (Fang Feng Cao) is a traditional Chinese medicine that has served as an alternative therapy for multiple diseases, including inflammatory diseases and cancer [[6], [7], [8]]. Ovatodiolide is a macrocyclic diterpenoid compound that is extracted from Anisomeles indica (L.) Kuntze (Labiatae) [9]. Ovatodiolide exhibits anti-inflammatory, anti-Helicobacter pylori activity and alleviates gastric ulcers [10,11]. Furthermore, considerable research has focused on exploring its anticancer activity. A number of studies have demonstrated that ovatodiolide exhibits inhibitory activity on many solid tumor cells [6,12,13]. A previous study suggested that ovatodiolide might also inhibit CML cells [14]. However, additional experimental evidence is required to further clarify this effect, and the underlying mechanism remains unknown.

Autophagy is a catabolic mechanism that mediates the recycling and turnover of intracellular constituents in response to cellular stress [15]. Generally, autophagy can be viewed as an adaptive response. However, it also promotes cell death through “autophagic cell death”, or mediates cell death by triggering apoptosis or necrosis. Specifically, in CML, under circumstances following treatment with chemotherapeutic agents, both the beneficial and detrimental role of autophagy have been reported [[16], [17], [18], [19]]. Regarding ovatodiolide, a recent study revealed that it might suppress autophagy in hepatocellular carcinoma [13]. However, its role in the regulation of autophagy is still obscure in CML.

P62 is a stress-related autophagic cargo receptor that functions as a signaling hub and the Nrf2-Keap1 pathway is a major cellular defense mechanism [20,21]. When cells suffer oxidative stress, Nrf2 dissociates from Keap1 and translocates into the nucleus to activate the expression of a battery of antioxidant and anti-inflammatory enzymes [20]. In addition, p62 possesses the capacity to modulate Nrf2 signaling by interacting with Keap1 [20]. Thus, p62 may serve as a link between autophagy and Nrf2 signaling under cellular stress conditions. However, the role of p62-Keap1-Nrf2 signaling in ovatodiolide-treated CML cells has rarely been studied.

The aim of this study was to investigate the anticancer efficacy of ovatodiolide against CML cells and further elucidate the role of ovatodiolide on autophagy and the p62-Keap1-Nrf2 pathway in CML cells.