linarin and Glioma

Glioma is the most common form of malignant brain cancer with high mortality rate in human. Therefore, finding effective therapeutic strategy and revealing the underlying molecular mechanism is necessary. Plant-extracted flavonoid glycosides have been suggested to be bioactive compounds with pleiotropic functions, such as anti-cancer, anti-inflammatory, antioxidant and effects. Our study was attempted to explore the anti-cancer role of linarin (acacetin-7-O-β-d-rutinoside) in glioma in vitro and in vivo. Nuclear factor kappa-B (NF-κB) activity is a common phenomenon in various cancers, resulting in abnormal cell proliferation, malignant transformation, or resistance to cell death. P53, an essential tumor suppressor, plays an important role in preventing tumor progression. Our data indicated that linarin suppressed glioma cell proliferation and migration by inducing apoptosis, which was through reducing cell cycle-related signals, including Survivin, p-Rb, and Cyclin D1, while promoting p21, Bax, Caspase-3 and poly (ADP-ribose) polymerase (PARP) activation. Also, we found that linarin-reduced cellular proliferation of glioma was dependent on p53 up-regulation and Nuclear factor kappa-B (NF-κB)/p65-down-regulation, thereby inhibiting glioma cell growth. We further conformed the inhibitory effect of linarin in vivo using xenograft tumor model. Linarin significantly triggered apoptosis as well as the tumor growth in animals, accompanied with p53 increase and p65 decrease. Our data illustrated that linarin could be used as a promising candidate against glioma progression.

Topics: Animals; Apoptosis; Brain Neoplasms; Caspase 3; Cell Line, Tumor; Cell Movement; Cell Proliferation; Glioma; Glycosides; Humans; Male; Mice, Inbred BALB C; Mice, Nude; Signal Transduction; Transcription Factor RelA; Tumor Stem Cell Assay; Tumor Suppressor Protein p53; Up-Regulation

Tumor necrosis factor-related apoptosis-induced ligand (TRAIL) is reported as a promising anti-cancer therapeutic agent. Nevertheless, a variety of cancer cells, including human malignant glioma cells, are resistant to TRAIL treatment, indicating that it is necessary to find effective strategies to overcome the TRAIL resistance. Linarin (LIN), a natural flavonoid compound in Flos Chrysanthemi Indici (FCI), has been exhibited to exert various pharmacological activities, including anti-cancer. Here in our study, we found that non-cytotoxic doses of LIN (5μM) dramatically potentiated TRAIL (80ng/ml)-induced cytotoxicity (52.36±1.58%) and apoptosis (68.50±1.23%) using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and flow cytometry assays, respectively, in human glioma cells of U87MG. Apoptosis was evidenced by enhanced cleavage of Caspase-8/-9/-3 and poly (ADP-ribose) polymerase (PARP), and reduced anti-apoptotic proteins, including B-cell leukemia/lymphoma 2 (Bcl-2), mantle cell lymphoma (Mcl)-1, and Survivin. Moreover, both intrinsic and extrinsic apoptosis pathways were included in apoptosis induced by LIN and TRAIL co-treatment, along with high release of Cyto-c into cytoplasm and enhancement of fas-associated protein with death domain (FADD), death-inducing signaling complex (DISC), death receptor 4 (DR) 4 and DR5, respectively. Reactive oxygen species (ROS) generation, up to 39.86±2.32%, was also highly triggered by TRAIL and LIN combinational treatment, which was accompanied with high phosphorylation of c-Jun-N-terminal kinase (JNK). In vivo, TRAIL and LIN double treatment significantly reduced the tumor growth using xenograft tumor model through inducing apoptosis. We demonstrated that combining LIN with TRAIL treatments might be effective against TRAIL-resistant glioma cells through inducing apoptosis regulated by ROS generation.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Cell Line, Tumor; Chrysanthemum; Flow Cytometry; Glioma; Glycosides; Humans; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Nude; Reactive Oxygen Species; TNF-Related Apoptosis-Inducing Ligand; Xenograft Model Antitumor Assays