Tetrandrine triggers an alternative autophagy in DU145 cells

Abstract

Abstract. Tetrandrine (Tet), a potent lysosomal inhibitor, blocks autophagic flux and induces cancer cell death. Previously, the present authors identified the prostate cancer cell line DU145 to exhibit high sensitivity towards Tet in 11 cancer cell lines. In the present study, autophagy in Tet-treated DU145 cells was investigated. Similar to other cell lines, such as PC-3 and 786-O cells, Tet neutralized the acidity of lysosome and blocked autophagy in DU145 cells. However, Tet failed to induce microtubule-associated protein 1 light chain 3 (LC3) conversion in DU145 cells. By contrast, it was observed by transmission electron microscopy that Tet induced an accumulation of autophagosomes in the cytoplasm. These contrasting results indicated that Tet triggered an LC3-independent autophagy in DU145 cells. Alkalizing lysosome with chloroquine enhanced Tet-induced cell death. The results of the present study indicated that detection of autophagy in tumor cells may assist in selecting lysosome inhibitors for chemotherapy treatment in prostate cancer. Introduction Tetrandrine (Tet), a natural product isolated fromStephania tetrandra, has been reported to be an anti-tumor and anti-inflammatory drug (1-8). Previously, the present authors have demonstrated that Tet induces cell death in 11 cancer cell lines (1). Tet directly neutralizes the lysosomal acidity, blocks the autophagic flux in the degradation step and causes energetic impairment, which eventually results in cell death (1). By contrast, Tet also acts as an autophagy agonist by inducing the synthesis of reactive oxygen species (3,4,9-11), indicating that Tet may function as a multi-target drug to regulate autophagy in cancer cells. Regardless of the Tet target, the present authors and other groups have previously consistently observed that Tet increases the number of autophagosomes, levels of microtubule-associated protein 1 light chain 3, type II (LC3-II) and the number of enhanced green fluorescent protein-LC3 puncta in cancer cells (1,3,9). DU145, a commonly used prostate cancer cell line for research, is different from PC-3 and LNCaP cells in terms of autophagy regulation (12). As alternative transcripts of autophagy related 5 (ATG5) lack one or two exons in DU145 cells, and this causes the autophagy pathway to be genetically impaired (12). By contrast, DU145 cells exhibited the highest sensitivity to Tet in all of the 11 cancer cell lines that were previously tested by the authors of the present study (1), implying that impairment in autophagy may increase Tet-induced cell death. In order to investigate the role of autophagy on Tet-induced cell death in DU145 cells, the ultrastructural changes following Tet treatment were observed by transmission electron microscopy (TEM). Notably, Tet treatment triggered an accumulation of autophagosomes in this cell line, indicating that alternative autophagy was involved. Materials and methodsTetrandrine and other reagents. Tet (Santa Cr uz Biotechnology, Inc., Dallas, TX, USA) was dissolved as previously described (1)....

Potent antitumor activity of cepharanthine against triple‑negative breast cancer spheroids compared with tetrandrine

“…TET possesses a notable antitumor activity in numerous types of cancer, including gastric, lung, liver and colorectal cancer, both in vitro and in vivo ( 12 , 13 ). The mechanisms of action of TET are associated with multiple factors, such as modulating molecular signaling pathways ( 14 ), inducing cancer cell apoptosis ( 15 ), promoting cell cycle arrest ( 16 ) and increasing cell autophagy ( 17 ). Although TET has been approved in China for some types of cancer, such as acute myelogenous leukemia and advanced non-small cell lung cancer ( 18 , 19 ), it has not been yet approved in Japan as an antitumor drug for patients with cancer.…”

Fangchinoline Induces Apoptosis, Autophagy and Energetic Impairment in Bladder Cancer

“…Tetrandrine (Tet), a widely investigated compound, exhibits potent anti-tumor effects in lung cancer, prostate cancer, breast cancer and bladder cancer [1][2][3][4][5][6]. In bladder cancer, Tet induces apoptosis and reverses the epithelial-mesenchymal transition [2,6].…”

The Secrets of Alternative Autophagy

“…Atg5-independent autophagy has also been described in cells from fetal brains, livers, and hearts [47], as well as in human epidermis [51]. In addition to normal cells, alternative autophagy has also been reported in various cancer cell lines, including prostate DU145 cancer cells [54,55], erythroleukemia K562 cells [6], adenocarcinoma H1650 cells, and lung carcinoma A549 cells [56].…”

“…It has been reported that no LC3 lipidation occurs during alternative autophagy [39]. Thus, the results based on LC3 conversion should be interpreted with caution [55]. Instead of LC3, Rab9, Syntaxin 7, and p-Ulk1 746 (p-ULK1 747 ) seem to be more appropriate potential markers [48,59].…”