Luteoloside induces G(0)/G(1) arrest and pro-death autophagy through the ROS-mediated AKT/mTOR/p70S6K signalling pathway in human non-small cell lung cancer cell lines.

Autophagy has attracted a great deal of interest in tumour therapy research in recent years. However, the anticancer effect of luteoloside, a naturally occurring flavonoid isolated from the medicinal plant Gentiana macrophylla, on autophagy remains poorly understood in human lung cells. In the present study, we have investigated the anticancer effects of luteoloside on non-small cell lung cancer (NSCLC) cells and demonstrated that luteoloside effectively inhibited cancer cell proliferation, inducing G0/G1 phase arrest associated with reduced expression of CyclinE, CyclinD1 and CDK4; we further found that treatment with luteoloside did not strongly result in apoptotic cell death in NSCLC (A549 and H292) cells. Interestingly, luteoloside induced autophagy in lung cancer cells, which was correlated with the formation of autophagic vacuoles, breakdown of p62, and the overexpression of Beclin-1 and LC3-II, but not in a human bronchial epithelial cell line (BEAS-2B). Notably, pretreatment of cancer cells with 3-MA, an autophagy inhibitor, protected against autophagy and promoted cell viability but not apoptosis. To further clarify whether luteoloside-induced autophagy depended on the PI3K/AKT/mTOR/p70S6K signalling pathway, a major autophagy-suppressive cascade, cells were treated with a combination of AKT inhibitor (LY294002) and mTOR inhibitor (Rap). These results demonstrated that luteoloside induced autophagy in lung cancer cell lines by inhibiting the pathway at p-Akt (Ser473), p-mTOR and p-p70S6K (Thr389). Moreover, we observed that luteoloside-induced cell autophagy was correlated with production of reactive oxygen species (ROS). NAC-mediated protection against ROS clearly implicated ROS in the activation of autophagy and cell death. In addition, the results showed that ROS served as an upstream effector of the PI3K/AKT/mTOR/p70S6K pathway. Taken together, the present study provides new insights into the molecular mechanisms underlying luteoloside-mediated cell death in NSCLC cells and supports luteoloside as a potential anti-cancer agent for targeting NSCLC through the induction of autophagy, inhibition of proliferation and PI3K/AKT/mTOR/p70S6K signalling.

Zhou M ，Shen S ，Zhao X ，Gong X ... -  《-》

Delicaflavone induces autophagic cell death in lung cancer via Akt/mTOR/p70S6K signaling pathway.

Sui Y ，Yao H ，Li S ，Jin L ，Shi P ，Li Z ，Wang G ，Lin S ，Wu Y ，Li Y ，Huang L ，Liu Q ，Lin X ... -  《-》

Polyphyllin VI, a saponin from Trillium tschonoskii Maxim. induces apoptotic and autophagic cell death via the ROS triggered mTOR signaling pathway in non-small cell lung cancer.

Non-small cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancers. Our previous studies have proven that Trillium tschonoskii Maxim. (TTM), a traditional Chinese medicine, possesses potent anti-tumor effect. However, the detailed components and molecular mechanism of TTM in anti-NSCLC are still unknown. In the present experiment, polyphyllin VI (PPVI) was successfully isolated from TTM with guidance of the anti-proliferative effect in A549 cells, and the cell death of PPVI treated A549 and H1299 cells was closely linked with the increased intracellular ROS levels. In addition, PPVI induced apoptosis by promoting the protein expression of Bax/Bcl2, caspase-3 and caspase-9, and activated autophagy by improving LC3 II conversion and GFP-LC3 puncta formation in A549 and H1299 cells. The mechanism study found that the activity of mTOR which regulates cell growth, proliferation and autophagy was significantly suppressed by PPVI. Accordingly, the PI3K/AKT and MEK/ERK pathways positively regulating mTOR were inhibited, and AMPK negatively regulating mTOR was activated. In addition, the downstream of mTOR, ULK1 at Ser 757 which downregulates autophagy was inhibited by PPVI. The apoptotic cell death induced by PPVI was confirmed, and it was significantly suppressed by the overexpression of AKT, ERK and mTOR, and the induced autophagic cell death which was depended on the Atg7 was decreased by the inhibitors, such as LY294002 (LY), Bafilomycin A1 (Baf), Compound C (CC) and SBI-0206965 (SBI). Furthermore, the mTOR signaling pathway was regulated by the increased ROS as the initial signal in A549 and H1299 cells. Finally, the anti-tumor growth activity of PPVI in vivo was validated in A549 bearing athymic nude mice. Taken together, our data have firstly demonstrated that PPVI is the main component in TTM that exerts the anti-proliferative effect by inducing apoptotic and autophagic cell death in NSCLC via the ROS-triggered mTOR signaling pathway, and PPVI may be a promising candidate for the treatment of NSCLC in future.

Teng JF ，Qin DL ，Mei QB ，Qiu WQ ，Pan R ，Xiong R ，Zhao Y ，Law BY ，Wong VK ，Tang Y ，Yu CL ，Zhang F ，Wu JM ，Wu AG ... -  《-》

Piperlongumine induces apoptosis and autophagy in human lung cancer cells through inhibition of PI3K/Akt/mTOR pathway.

Piperlongumine (PL), a natural alkaloid present in the fruit of the Long pepper, is known to exhibit notable anti-cancer effects. Nonetheless, the anti-tumor effect of PL in lung cancer cells still remains unclear. In the present study, we reported the chemotherapeutic effects of PL using in vitro and in vivo models. We showed that PL displayed potent anti-neoplastic activity against lung cancer A549 cells as well as corresponding docetaxel-resistant A549/DTX cells. In addition, we found that PL induced apoptosis in both A549 and A549/DTX cells. PL also induced autophagy in A549/DTX cells. Moreover, autophagy-specific inhibitors (3-methyladenine) or Beclin1 and Atg 5 small interfering RNAs (siRNAs) enhanced PL-induced apoptosis, indicating that PL-mediated autophagy may protect A549/DTX cells from undergoing apoptotic cell death. Furthermore, we observed the inhibition of phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway by PL. Finally, PL inhibited the growth of A549/DTX xenograft tumors, which was associated with inhibition of cell proliferation, induction of apoptosis of tumor cells and decreased expression of p-Akt and p-mTOR in tumor xenograft tissues. In summary, our study demonstrated that PL induced apoptosis and autophagy through modulation of the PI3K/Akt/mTOR pathway in human lung cancer cells. This study may provide a rationale for future clinical application using PL as a chemotherapeutic agent for lung cancer.

Wang F ，Mao Y ，You Q ，Hua D ，Cai D ... -  《INTERNATIONAL JOURNAL OF IMMUNOPATHOLOGY AND PHARMACOLOGY》

Eriocalyxin B, a novel autophagy inducer, exerts anti-tumor activity through the suppression of Akt/mTOR/p70S6K signaling pathway in breast cancer.

Eriocalyxin B (EriB), a natural ent-kaurane diterpenoid presented in the plant Isodon eriocalyx var. laxiflora, has been reported to diminish angiogenesis-dependent breast tumor growth. In the present study, the effects of EriB on human breast cancer and its underlying mechanisms were further investigated. The in vitro anti-breast cancer activity of EriB was determined using MCF-7 and MDA-MB-231 cell lines. MDA-MB-231 xenograft model of human breast cancer was also established to explore the anti-tumor effect in vivo. We found that EriB was able to induce apoptosis accompanied by the activation of autophagy, which was evidenced by the increased accumulation of autophagosomes, acidic vesicular organelles formation, the microtubule-associated protein 1A/1B-light chain 3B-II (LC3B-II) conversion from LC3B-I and p62 degradation. Meanwhile, EriB treatment time-dependently decreased the phosphorylation of Akt, mammalian target of rapamycin (mTOR) and ribosomal protein S6 kinase (p70S6K), leading to the inhibition of Akt/mTOR/p70S6K signaling pathway. Moreover, the blockage of autophagy obviously sensitized EriB-induced cell death, which suggested the cytoprotective function of autophagy in both MCF-7 and MDA-MB-231 cells. Interestingly, the autophagic features and apoptosis induction were prevented by reactive oxygen species (ROS) scavenger N-acetyl-l-cysteine, indicating that ROS played an essential role in the mediation of EriB-induced cell death. Furthermore, in MDA-MB-231 xenograft model, EriB displayed a significant anti-tumor effect via the activation of autophagy and apoptosis in breast tumor cells. Taken together, our findings firstly demonstrated that EriB suppressed breast cancer cells growth both in vitro and in vivo, and thus could be developed as a promising anti-breast tumor agent.

Zhou X ，Yue GG ，Chan AM ，Tsui SK ，Fung KP ，Sun H ，Pu J ，Lau CB ... -  《-》