Background: Noscapine is an opium alkaloid that has recently been shown to potentiate anti-cancer therapeutic effects by inducing apoptosis in various malignant cells without any detectable toxicity. However, the mechanism by which noscapine induces apoptosis in colon cancer cells remains unclear.
Materials and Methods: In this study, we explored the anti-cancer activity of noscapine in 5-fluorouracil (5-FU)-resistant human colon cancer cell lines HT29/5-FU and LoVo/5-FU and investigated the possible underlying mechanism. The apoptosis and mitochondrial morphology of cells were detected by TUNEL assay and transmission electron microscopy (TEM). The mitochondrial membrane potential (MMP) was determined using JC-1. The mitochondrial permeability transition pore (mPTP) opening was detected by the calcein-AM/cobalt assay. The levels of glucose, lactic, and ATP in cells were evaluated by ELISA kits. Relative protein expression levels were detected by Western blot.
Results: We verified that PTEN was involved in noscapine-induced apoptosis in HT29/5-FU and LoVo/5-FU cells. Noscapine greatly increased mitochondrial damage by altering mitochondrial morphology, inducing mitochondrial membrane potential depolarization, and enabling mitochondrial permeability transition pore opening in HT29/5-FU and LoVo/5-FU cells. In addition, noscapine inhibited the Warburg effect by decreasing the levels of glucose, lactic acid, and ATP and inhibiting the protein expression of glucose transporter 1, lactate dehydrogenase-B, hexokinase 2, and pyruvate kinase M2 in HT29/5-FU and LoVo/5-FU cells. However, PTEN interference counteracted the effect of noscapine on mitochondrial damage and the Warburg effect in HT29/5-FU and LoVo/5-FU cells by decreasing the activation of PI3K/mTOR signaling.
Conclusion: These results indicated that noscapine induced the apoptosis of HT29/5-FU and LoVo/5-FU human colon cancer cells by regulating mitochondria damage and the Warburg effect via PTEN, and the process is closely related to the PI3K/mTOR signaling pathway.
Keywords: colon cancer, noscapine, mitochondrial damage, PTEN, PI3K/mTOR