Colorectal cancer is a common cancer all over the world, and its morbidity and case-fatality rates are growing in China in the past few years (Liao et al., 2023). There are still no therapies available that can efficiently prevent the development and progression of colorectal cancer, although its disease etiology has been fairly well understood (Wang et al., 2019). Various chemotherapeutics have been developed to treat colorectal cancer, but most of them are associated with drug resistance and acute side effects (Zaman et al., 2022). Thus, development of new anti-colorectal cancer treatments is one of the greatest challenges for pharmacologists.

Emerging data have revealed that aberrant activation of Akt, namely protein kinase B (PKB), is implicated in the progression of colorectal cancer (Malkomes et al., 2016). Akt consists of several evolutionarily conserved domains, namely a kinase domain, a lipid-binding N-terminal PH domain and a hydrophobic motif (Brown and Banerji, 2017). When stimulated, Akt (PH domain) can be transferred to cytomembranes by phosphoinositide 3-kinase (PI3K) to trigger a conformational change, which facilitates Akt phosphorylation at Thr308 by 3-phosphoinositide-dependent protein kinase 1 (PDK1). In addition, Akt phosphorylation can also occur at Ser473 by mammalian target of rapamycin complex 2 (mTORC2) (Revathidevi and Munirajan, 2019). Activated Akt regulates diverse intracellular physiological processes, such as apoptosis, mitosis and autophagy, by controlling several downstream molecules such as mammalian target of rapamycin complex 1 (mTORC1) (Glaviano et al., 2023).

Two main types of Akt inhibitors have been reported. One type is ATP-competitive inhibitors, which can occupy the ATP-binding site of Akt, thereby inhibiting kinase activity. Due to ubiquity of ATP-binding sites in many kinases, these inhibitors have weak kinase specificity (Guo et al., 2021). Another type is allosteric inhibitors, which mainly bind to the PH domain or kinase domain. They usually alter the protein conformation of Akt into a “closed” state and prevent Akt phosphorylation by upstream kinases. Because of their high kinase specificity, Akt allosteric inhibitors cause few side effects and have great application prospects (Savill et al., 2022). Recently, several Akt allosteric inhibitors have been found to be able to treat colorectal cancer in preclinical studies. However, testing Akt allosteric inhibitors in clinical trials remains challenging because of limitations associated with efficacy and dose (Weisner et al., 2019). Therefore, much effort is now underway to discover novel Akt allosteric inhibitors for treatment of colorectal cancer.

Licorice (Gan-Cao in Chinese) is a frequently used herbal medicine all over the world for thousands of years, and has been recorded in the pharmacopeias of many countries such as China, United States and Japan (Ding et al., 2022). Chinese Pharmacopoeia demonstrates that licorice is the roots and rhizomes of Glycyrrhiza uralensis Fisch., Glycyrrhiza inflata Bat. and Glycyrrhiza glabra L., and possesses several functions including invigorating spleen, replenishing Qi, clearing heat, removing toxicity and relieving pain (Commission, 2020). Licorice is clinically used to treat various diseases such as cough, hepatitis, cancer and influenza, and modern pharmacological studies prove that licorice has strong anti-inflammatory, antioxidative, anti-tumor, antiviral and antibacterial activities (Yan et al., 2023). In recent years, the anti-tumor effects of licorice are gaining more and more attention especially the cancers in stomach, lung, colon and liver. Licorice mainly contains three types of chemical ingredients namely flavonoid glucosides, triterpenoid saponins and prenylated flavonoids, and it has been reported that prenylated flavonoids play an important role in the anti-tumor activity of licorice (Zhang et al., 2021).

Our previous studies have shown that several prenylated flavonoids from licorice can induce death of colorectal cancer cells through activating autophagy, which contributes to understanding of the anti-tumor mechanism of licorice (Ji et al., 2017; Shao et al., 2022). Given the plentiful prenylated flavonoids in licorice, it is worthy to investigate the anti-colorectal cancer activity and underlying mechanism of other compounds. Wighteone is one of the main prenylated flavonoids in licorice (Fig. 1A) (Song et al., 2017), and its possible effect and target against colorectal cancer have not been investigated. Here, we clarified for the first time that wighteone significantly inhibited growth of SW480 colorectal cancer cells through allosteric inhibition of Akt. Wighteone could interact with both PH and kinase domains of Akt and maintain it in the “closed” conformation. Further mechanistic studies indicated that wighteone-induced Akt inhibition led to cycle arrest, apoptosis and autophagic death of SW480 cells. Moreover, the in vivo anti-colorectal cancer effect and Akt inhibition activity of wighteone were confirmed in the nude mouse xenograft model, suggesting the potential of wighteone as a lead compound for colorectal cancer treatment.