Stemness-Suppressive Effect of Bibenzyl from Dendrobium ellipsophyllum in Human Lung Cancer Stem-Like Cells.

Cancer stem-like cells (CSCs) are key mediators driving tumor initiation, metastasis, therapeutic failure, and subsequent cancer relapse. Thus, targeting CSCs has recently emerged as a potential strategy to improve chemotherapy. In this study, the anticancer activity and stemness-regulating capacity of 4,5,4'-trihydroxy-3,3'-dimethoxybibenzyl (TDB), a bibenzyl extracted from Dendrobium ellipsophyllum, are revealed in CSCs of various human lung cancer cells. Culture with TDB (5-10 µM) strongly abolished tumor-initiating cells in lung cancer H460, H23, and A549 cells in both anchorage-dependent and anchorage-independent colony formation assays. Through the 3D single-spheroid formation model, attenuation of self-renewal capacity was observed in CSC-enriched populations treated with 1-10 µM TDB for 7 days. Flow cytometry analysis confirmed the attenuation of %cell overexpressing CD133, a CSC biomarker, in TDB-treated lung cancer spheroids. TDB at 5-10 µM remarkably suppressed regulatory signals of p-Akt/Akt, p-GSK3ß/GSK3ß, and ß-catenin corresponding to the downregulated mRNA level of stemness transcription factors including Nanog, Oct4, and Sox2. Moreover, the antiapoptosis Bcl-2 and Mcl-1 proteins, which are downstream molecules of Akt signaling, were evidently decreased in CSC-enriched spheroids after culture with TDB (1-10 µM) for 24 h. Interestingly, the diminution of Akt expression by specific siAkt effectively reversed suppressive activity of TDB targeting on the CSC phenotype in human lung cancer cells. These findings provide promising evidence of the inhibitory effect of TDB against lung CSCs via suppression of Akt/GSK3ß/ß-catenin cascade and related proteins, which would facilitate the development of this bibenzyl natural compound as a novel CSC-targeted therapeutic approach for lung cancer treatment.

22-O-(N-Boc-L-glycine) ester of renieramycin M inhibits migratory activity and suppresses epithelial-mesenchymal transition in human lung cancer cells.

The incidence of metastasis stage crucially contributes to high recurrence and mortality rate in lung cancer patients. Unfortunately, no available treatment inhibits migration, a key metastasis process in lung cancer. In this study, the effect of 22-O-(N-Boc-L-glycine) ester of renieramycin M (22-Boc-Gly-RM), a semi-synthetic amino ester derivative of bistetrahydroisoquinolinequinone alkaloid isolated from Xestospongia sp., on migratory behavior of human lung cancer cells was investigated. Following 24 h of treatment, 22-Boc-Gly-RM at non-toxic concentrations (0.5-1 µM) effectively restrained motility of human lung cancer H460 cells assessed through wound healing, transwell migration, and multicellular spheroid models. The capability to invade through matrix component was also repressed in H460 cells cultured with 0.1-1 µM 22-Boc-Gly-RM. The dose-dependent reduction of phalloidin-stained actin stress fibers corresponded with the downregulated Rac1-GTP level presented via western blot analysis in 22-Boc-Gly-RM-treated cells. Treatment with 0.1-1 µM of 22-Boc-Gly-RM obviously caused suppression of p-FAK/p-Akt signal and consequent inhibition of epithelial-to-mesenchymal transition (EMT), which was evidenced with augmented level of E-cadherin and reduction of N-cadherin expression. The alteration of invasion-related proteins in 22-Boc-Gly-RM-treated H460 cells was indicated by the diminution of matrix metalloproteinases (MT1-MMP, MMP-2, MMP-7, and MMP-9), as well as the upregulation of tissue inhibitors of metalloproteinases (TIMP), TIMP2, and TIMP3. Thus, 22-Boc-Gly-RM is a promising candidate for anti-metastasis treatment in lung cancer through inhibition of migratory features associated with suppression on EMT.

Chemosensitizing activity of peptide from Lentinus squarrosulus (Mont.) on cisplatin-induced apoptosis in human lung cancer cells.

The limitations of cisplatin, a standard chemotherapy for lung cancer, have been documented with serious adverse effects and drug resistance. To address the need for novel therapy, this study firstly reveals the potential of peptide from Lentinus squarrosulus (Mont.) as a chemotherapeutic adjuvant for cisplatin treatment. The purified peptide from L. squarrosulus aqueous extracts was obtained after eluting with 0.4 M NaCl through FPLC equipped with anion exchange column. Preincubation for 24 h with 5 µg/mL of the peptide at prior to treatment with 5 µM cisplatin significantly diminished %cell viability in various human lung cancer cells but not in human dermal papilla and proximal renal cells. Flow cytometry indicated the augmentation of cisplatin-induced apoptosis in lung cancer cells pretreated with peptide from L. squarrosulus. Preculture with the peptide dramatically inhibited colony formation in lung cancer cells derived after cisplatin treatment. Strong suppression on integrin-mediated survival was evidenced with the diminution of integrins (ß1, ß3, ß5, α5, αV) and down-stream signals (p-FAK/FAK, p-Src/Src, p-Akt/Akt) consequence with alteration of p53, Bax, Blc-2 and Mcl-1 in cisplatin-treated lung cancer cells preincubated with peptide from L. squarrosulus. These results support the development of L. squarrosulus peptide as a novel combined chemotherapy with cisplatin for lung cancer treatment.