Endomorphin-2

Triple-negative breast cancer (TNBC) exhibits the highest recurrence and mortality rates among breast cancer subtypes. Approximately one million TNBC cases are diagnosed worldwide annually. Current clinical treatments, primarily chemotherapy regimens based on paclitaxel and anthracycline, are associated with high recurrence rates and low overall survival rates. Platinum drugs, introduced for TNBC treatment, demonstrated a positive effect; however, their high-dose administration inevitably results in toxic side effects and drug resistance. Therefore, identifying agents that sensitize patients to platinum-based therapies is critical. Analysis of the TCGA database revealed that AKT1 and autophagy are activated in breast cancer, playing crucial roles in malignant behavior. Further investigation demonstrated that CBP activates the AKT pathway in MDA-MB-231 cells, while its combination with LY294002 or Triciribine (inhibitors of the PI3K/AKT pathway), suppresses cell proliferation. However, this combination also activates autophagy, a protective mechanism. Inhibition of autophagy with CQ or Baf A1 further increased the proliferation-inhibitory effects of CBP in MDA-MB-231 cells. Notably, the sesquiterpene lactone EM-2 extracted from Elephantopus mollis H.B.K., significantly inhibited both the AKT and autophagy pathways in TNBC cells, demonstrating superior cellular inhibitory effects compared with other AKT or autophagy inhibitors combined with CBP. When CBP was combined with EM-2, cell survival decreased by approximately 36 % compared with CBP monotherapy, while the apoptosis rate increased by 22.8 % after 48 h. The combination of CBP and EM2 also produced the greatest tumor shrinkage in vivo. Interestingly, the CBP (3 mg/kg) + EM-2 (6 mg/kg) group achieved the same tumor shrinkage, with only one-fifth the amount of CBP compared with the CBP (16 mg/kg) monotherapy group. In other words, low doses of EM-2 combined with CBP produced the same anti-tumor effects as high-dose CBP alone. These findings provide a novel strategy for the treatment of CBP using dual AKT and autophagy inhibitors, highlighting potential clinical applications.

Enhancing the efficacy of chemotherapy in treating triple-negative breast cancer (TNBC) remains crucial. Understanding the genes involved in cancer progression and targeted therapies may be beneficial for TNBC chemotherapy. Here, bioinformatics analysis revealed that AKT1 and the key gene of homologous recombination (HR), RAD51, were significantly upregulated in breast cancer. Meanwhile, we discovered that epirubicin (Epi) could activate AKT and HR pathways in MDA-MB-231 cells. Pharmacological inhibition of AKT or siAKT could reverse the activation of AKT and HR pathways and sensitize Epi. Hence, we sought natural products that could inhibit both AKT and HR pathways to enhance the sensitivity of Epi and expanded its therapeutic effects in TNBC. 2β-methoxy-2-deethoxyphantomolin (EM2) is a natural sesquiterpene lactone extracted from Elephantopus mollis with strong anticancer activity. We found that EM2 induced apoptosis of MDA-MB-231 cells by inhibiting AKT and HR pathways. Mechanistically, EM2 impaired transcription of AKT, directly bound to RAD51 protein, and facilitated the degradation of AKT and RAD51 in a caspase-dependent manner. Importantly, we determined that EM2 in combination with Epi treatment exhibited a synergistic anti-tumor effect in MDA-MB-231 cells. Moreover, overexpression of AKT could prevent EM2 from sensitizing Epi. The results of MDA-MB-231 xenograft tumor model confirmed that EM2 could reduce the dose of Epi and achieve anti-TNBC effect in vivo without toxicity to mice tissues. Overall, our work indicates EM2 in combination with Epi can greatly expand the therapeutic effect of Epi in TNBC, underscoring targeting AKT and RAD51 as a promising approach for TNBC chemotherapy sensitization.