Growth inhibition and induction of differentiation by panaxydol in rat C6 glioma cells

Terpenoids, Cannabimimetic Ligands, beyond the Cannabis Plant

Medicinal use of Cannabis sativa L. has an extensive history and it was essential in the discovery of phytocannabinoids, including the Cannabis major psychoactive compound-Δ9-tetrahydrocannabinol (Δ9-THC)-as well as the G-protein-coupled cannabinoid receptors (CBR), named cannabinoid receptor type-1 (CB1R) and cannabinoid receptor type-2 (CB2R), both part of the now known endocannabinoid system (ECS). Cannabinoids is a vast term that defines several compounds that have been characterized in three categories: (i) endogenous, (ii) synthetic, and (iii) phytocannabinoids, and are able to modulate the CBR and ECS. Particularly, phytocannabinoids are natural terpenoids or phenolic compounds derived from Cannabis sativa. However, these terpenoids and phenolic compounds can also be derived from other plants (non-cannabinoids) and still induce cannabinoid-like properties. Cannabimimetic ligands, beyond the Cannabis plant, can act as CBR agonists or antagonists, or ECS enzyme inhibitors, besides being able of playing a role in immune-mediated inflammatory and infectious diseases, neuroinflammatory, neurological, and neurodegenerative diseases, as well as in cancer, and autoimmunity by itself. In this review, we summarize and critically highlight past, present, and future progress on the understanding of the role of cannabinoid-like molecules, mainly terpenes, as prospective therapeutics for different pathological conditions.

Bufalin Induces Apoptosis and Improves the Sensitivity of Human Glioma Stem-Like Cells to Temozolamide

Glioma is the most common malignant tumor of the central nervous system, and it is characterized by high relapse and fatality rates and poor prognosis. Bufalin is one of the main ingredients of Chan-su, a traditional Chinese medicine (TCM) extracted from toad venom. Previous studies revealed that bufalin exerted inhibitory effects on a variety of tumor cells. To demonstrate the inhibitory effect of bufalin on glioma cells and glioma stem-like cells (GSCs) and discuss the underlying mechanism, the proliferation of glioma cells was detected by MTT and colony formation assays following treatment with bufalin. In addition, we investigated whether bufalin inhibits or kills GSCs using flow cytometry, Western blotting, and reverse transcription polymerase chain reaction analysis (RT-PCR). Finally, we investigated whether bufalin could improve the therapeutic effect of temozolomide (TMZ) and discussed the underlying mechanism. Taken together, our data demonstrated that bufalin inhibits glioma cell growth and proliferation, inhibits GSC proliferation, and kills GSCs. Bufalin was found to induce the apoptosis of GSCs by upregulating the expression of the apoptotic proteins cleaved caspase 3 and poly(ADP-ribose) polymerase (PARP) and by downregulating the expression of human telomerase reverse transcriptase, which is a marker of telomerase activity. Bufalin also improved the inhibitory effect of TMZ on GSCs by activating the mitochondrial apoptotic pathway. These results suggest that bufalin damages GSCs, induces apoptosis, and enhances the sensitivity of GSCs to TMZ.

Panaxydol Derived from Panax ginseng Inhibits G1 Cell Cycle Progression in Non-small Cell Lung Cancer via Upregulation of Intracellular Ca2+ Levels

Panaxydol, a polyacetylenic compound derived from Panax ginseng has been reported to suppress the growth of cancer cells. However, the molecular mechanisms underlying cell cycle arrest by this compound in non-small cell lung cancer (NSCLC) are unknown. Our study found that panaxydol treatment induced cell cycle arrest at G₁ phase in NSCLC cells. The cell cycle arrest was accompanied by down-regulation of the protein expression of cyclin-dependent kinase (CDK) 2, CDK4, CDK6, cyclin D₁ and cyclin E, and decrease in the phosphorylation of retinoblastoma (Rb) protein. Furthermore, up-regulation of cyclin-dependent kinase inhibitor (CDKI) p21^CIP1/WAF1 and p27^KIP1 was observed in panaxydol-treated NSCLC cells. In addition, panaxydol also induced accumulation of intracellular Ca²⁺ ([Ca²⁺]_i). (Acetyloxy)methyl 2-({2-[(acetyloxy)methoxy]-2-oxoethyl}[2-(2-{2-[bis({2-[(acetyloxy)methoxy]-2-oxoethyl})amino]phenoxy}ethoxy)phenyl]amino)acetate (BAPTA-AM), the Ca²⁺ chelator, attenuated not only panaxydol-induced accumulation of [Ca²⁺]_i, but also G₁ cell cycle arrest and decrease of CDK6 and cyclin D₁ protein expression level. These results demonstrated that the anti-proliferative effects of panaxydol were caused by cell cycle arrest, which is closely linked to the up-regulation of [Ca²⁺]_i and represents a promising approach for the treatment of lung cancer.

Shikonin Inhibits the Migration and Invasion of Human Glioblastoma Cells by Targeting Phosphorylated β-Catenin and Phosphorylated PI3K/Akt: A Potential Mechanism for the Anti-Glioma Efficacy of a Traditional Chinese Herbal Medicine

Shikonin is an anthraquinone derivative extracted from the root of lithospermum. Shikonin is traditionally used in the treatment of inflammatory and infectious diseases such as hepatitis. Shikonin also inhibits proliferation and induces apoptosis in various tumors. However, the effect of shikonin on gliomas has not been fully elucidated. In the present study, we aimed to investigate the effects of shikonin on the migration and invasion of human glioblastoma cells as well as the underlying mechanisms. U87 and U251 human glioblastoma cells were treated with shikonin at 2.5, 5, and 7.5 μmol/L and cell viability, migration and invasiveness were assessed with CCK8, scratch wound healing, in vitro Transwell migration, and invasion assays. The expression and activity of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) and the expression of phosphorylated β-catenin (p-β-catenin) and phosphorylated PI3K/Akt were also checked. Results showed that shikonin significantly inhibited the cell proliferation, migration, invasion, and expression of MMP-2 and MMP-9 in U87 and U251 cells. The expression of p-β-catenin showed contrary trends in two cell lines. It was significantly inhibited in U87 cells and promoted in U251 cells. Results in this work indicated that shikonin displayed an inhibitory effect on the migration and invasion of glioma cells by inhibiting the expression and activity of MMP-2 and -9. In addition, shikonin also inhibited the expression of p-PI3K and p-Akt to attenuate cell migration and invasion and MMP-2 and MMP-9 expression in both cell lines, which could be reversed by the PI3K/Akt pathway agonist, insulin-like growth factor-1 (IGF-1).

Artemether combined with shRNA interference of vascular cell adhesion molecule-1 significantly inhibited the malignant biological behavior of human glioma cells

Artemether is the derivative extracted from Chinese traditional herb and originally used for malaria. Artemether also has potential therapeutic effects against tumors. Vascular cell adhesion molecule-1 (VCAM-1) is an important cell surface adhesion molecule associated with malignancy of gliomas. In this work, we investigated the role and mechanism of artemether combined with shRNA interference of VCAM-1 (shRNA-VCAM-1) on the migration, invasion and apoptosis of glioma cells. U87 human glioma cells were treated with artemether at various concentrations and shRNA interfering technology was employed to silence the expression of VCAM-1. Cell viability, migration, invasiveness and apoptosis were assessed with MTT, wound healing, Transwell and Annexin V-FITC/PI staining. The expression of matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9) and phosphorylated Akt (p-Akt) was checked by Western blot assay. Results showed that artemether and shRNA-VCAM-1 not only significantly inhibited the migration, invasiveness and expression of MMP-2/9 and p-Akt, but also promoted the apoptosis of U87 cells. Combined treatment of both displayed the maximum inhibitory effects on the malignant biological behavior of glioma cells. Our work revealed the potential therapeutic effects of artemether and antiVCAM-1 in the treatments of gliomas.

Effect of the alcoholic extract of Ashwagandha leaves and its components on proliferation, migration, and differentiation of glioblastoma cells: combinational approach for enhanced differentiation

Ashwagandha (Withania somnifera) is widely used in the Indian traditional system of medicine, Ayurveda. Although it is claimed to have a large variety of health-promoting effects, including therapeutic effects on stress and disease, the mechanisms of action have not yet been determined. In the present study, we aimed to investigate the growth inhibition and differentiation potential of the alcoholic extract of Ashwagandha leaves (i-Extract), its different constituents (Withaferin A, Withanone, Withanolide A) and their combinations on glioma (C6 and YKG1) cell lines. Withaferin A, Withanone, Withanolide A and i-Extract markedly inhibited the proliferation of glioma cells in a dose-dependent manner and changed their morphology toward the astrocytic type. Molecular analysis revealed that the i-Extract and some of its components caused enhanced expression of glial fibrillary acidic protein, change in the immunostaining pattern of mortalin from perinuclear to pancytoplasmic, delay in cell migration, and increased expression of neuronal cell adhesion molecules. The data suggest that the i-Extract and its components have the potential to induce senescence-like growth arrest and differentiation in glioma cells. These assays led us to formulate a unique combination formula of i-Extract components that caused enhanced differentiation of glial cells.

Cyclic AMP-dependent regulation of differentiation of rat C6 glioma cells by panaxydol

OBJECTIVES

Preliminary works have indicated that panaxydol possesses growth inhibition and induces differentiation in rat C6 glioma cells. However, the molecular mechanism underlying this differentiation remains unknown. We sought to investigate the role of cyclic adenosine monophosphate (cAMP) in cellular differentiation induced by panaxydol.

METHODS

C6 cells were treated with panaxydol and various specific inhibitors, and the inhibition of cell growth was assessed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide assay and homotransplantation in nude mice. Astrocytic processes were quantified under a phase-contrasted microscope. Glial fibrillary acidic protein expression and cell migration were carried out by Western blot and scratch-wound test, respectively. In addition, the intracellular cAMP concentration was measured by immunoassay.

RESULTS

Panaxydol induces the elevation of intracellular cAMP concentration in C6 cells. The effects of growth inhibition in vitro and in vivo and induction of differentiation in C6 cells by panaxydol could be inhibited by the cAMP inhibitor, Rp-adenosine 3',5'-cyclic monophosphothioate, but not by protein kinase A or protein kinase C specific inhibitors.

CONCLUSION

These results suggest that the cAMP-dependent pathway may regulate cellular proliferation, migration and differentiation in C6 glioma cells by panaxydol.