Tetrandrine induces apoptosis and triggers a caspase cascade in U2-OS and MG-63 cells through the intrinsic and extrinsic pathways

New emerging targets in osteosarcoma therapy: PTEN and PI3K/Akt crosstalk in carcinogenesis

Osteosarcoma (OS) is a malignant bone carcinoma that affects people in childhood and adulthood. The heterogeneous nature and chromosomal instability represent certain characteristics of OS cells. These cancer cells grow and migrate abnormally, making the prognosis undesirable for patients. Conventional and current treatments fail to completely eradicate tumor cells, so new therapeutics targeting genes may be considered. PI3K/Akt is a regulator of events such as growth, cell death, migration, and differentiation, and its expression changes during cancer progression. PTEN reduces PI3K/Akt expression, and its mutations and depletions have been reported in various tumors. Experimental evidence shows that there is upregulation of PI3K/Akt and downregulation of PTEN in OS. Increasing PTEN expression may suppress PI3K/Akt to minimize tumorigenesis. In addition, PI3K/Akt shows a positive association with growth, metastasis, EMT and metabolism of OS cells and inhibits apoptosis. Importantly, overexpression of PI3K/Akt causes drug resistance and radio-resistance and its level can be modulated by miRNAs, lncRNAs and circRNAs. Silencing PI3K/Akt by compounds and drugs can suppress OS. Here, we review in detail the function of the PTEN/PI3K/Akt in OS, revealing its biological function, function in tumor progression, resistance to therapy, and pharmacological significance.

Anti-Cancer Effect of Chlorophyllin-Assisted Photodynamic Therapy to Induce Apoptosis through Oxidative Stress on Human Cervical Cancer

Photodynamic therapy is an alternative approach to treating tumors that utilizes photochemical reactions between a photosensitizer and laser irradiation for the generation of reactive oxygen species. Currently, natural photosensitive compounds are being promised to replace synthetic photosensitizers used in photodynamic therapy because of their low toxicity, lesser side effects, and high solubility in water. Therefore, the present study investigated the anti-cancer efficacy of chlorophyllin-assisted photodynamic therapy on human cervical cancer by inducing apoptotic response through oxidative stress. The chlorophyllin-assisted photodynamic therapy significantly induced cytotoxicity, and the optimal conditions were determined based on the results, including laser irradiation time, laser power density, and chlorophyllin concentration. In addition, reactive oxygen species generation and Annexin V expression level were detected on the photodynamic reaction-treated HeLa cells under the optimized conditions to evaluate apoptosis using a fluorescence microscope. In the Western blotting analysis, the photodynamic therapy group showed the increased protein expression level of the cleaved caspase 8, caspase 9, Bax, and cytochrome C, and the suppressed protein expression level of Bcl-2, pro-caspase 8, and pro-caspase 9. Moreover, the proposed photodynamic therapy downregulated the phosphorylation of AKT1 in the HeLa cells. Therefore, our results suggest that the chlorophyllin-assisted photodynamic therapy has potential as an antitumor therapy for cervical cancer.

Progress on structural modification of Tetrandrine with wide range of pharmacological activities

Tetrandrine (Tet), derived from the traditional Chinese herb Fangji, is a class of natural alkaloids with the structure of bisbenzylisoquinoline, which has a wide range of physiological activities and significant pharmacfological effects. However, studies and clinical applications have revealed a series of drawbacks such as its poor water solubility, low bioavailability, and the fact that it can be toxic to humans. The results of many researchers have confirmed that chemical structural modifications and nanocarrier delivery can address the limited application of Tet and improve its efficacy. In this paper, we summarize the anti-tumor efficacy and mechanism of action, anti-inflammatory efficacy and mechanism of action, and clinical applications of Tet, and describe the progress of Tet based on chemical structure modification and nanocarrier delivery, aiming to explore more diverse structures to improve the pharmacological activity of Tet and provide ideas to meet clinical needs.

Targeting the two-pore channel 2 in cancer progression and metastasis

The importance of Ca²⁺ signaling, and particularly Ca²⁺ channels, in key events of cancer cell function such as proliferation, metastasis, autophagy and angiogenesis, has recently begun to be appreciated. Of particular note are two-pore channels (TPCs), a group of recently identified Ca²⁺-channels, located within the endolysosomal system. TPC2 has recently emerged as an intracellular ion channel of significant pathophysiological relevance, specifically in cancer, and interest in its role as an anti-cancer drug target has begun to be explored. Herein, an overview of the cancer-related functions of TPC2 and a discussion of its potential as a target for therapeutic intervention, including a summary of clinical trials examining the TPC2 inhibitors, naringenin, tetrandrine, and verapamil for the treatment of various cancers is provided.

Drug resistance-related microRNAs in osteosarcoma: Translating basic evidence into therapeutic strategies

Although the application of multiple chemotherapy brought revolutionary changes to improve overall survival of osteosarcoma patients, the existence of multidrug resistance (MDR) has become a great challenge for successful osteosarcoma treatment in recent decades. Substantial studies have revealed various underlying mechanisms of MDR in cancers. As for osteosarcoma, evidence has highlighted that microRNAs (miRNAs) can mediate in the processes of DNA damage response, apoptosis avoidance, autophagy induction, activation of cancer stem cells, and signal transduction. Besides, these drug resistance‐related miRNAs showed much promise for serving as candidates for predictive biomarkers of poor outcomes and shorter survival time, and therapeutic targets to reverse drug resistance and overcome treatment refractoriness. This review aims to demonstrate the potential molecular mechanisms of miRNAs‐regulated drug resistance in osteosarcoma, and provide insight in translating basic evidence into therapeutic strategies.

Cantharidin Inhibits Anti-Apoptotic Bcl-2 Family Proteins and Induces Apoptosis in Human Osteosarcoma Cell Lines MG-63 and MNNG/HOS via Mitochondria-Dependent Pathway

Background

Cantharidin (CTD) is one of the major active ingredients of blister beetles and has significant antitumor activity in many cancer cell lines. The aim of our study was to evaluate the effect of CTD on the apoptosis of human osteosarcoma cells MG-63 and MNNG/HOS, and to explore the possible molecular mechanism.

Material/Methods

Osteosarcoma cells MG-63 and MNNG/HOS were treated with varying concentrations of CTD. The proliferation inhibition of cells was detected by MTS. Flow cytometry and Hoechst 33258 staining were used to determine cell cycle arrest and apoptosis, and apoptosis-related protein levels were analyzed by Western blotting.

Results

Our current findings suggest that CTD could inhibit the proliferation of these 2 osteosarcoma cells. The cells treated with CTD showed an obvious apoptotic morphology, and CTD promoted cells apoptosis in a dose-dependent manner. In addition, cantharidin-induced apoptosis was accompanied by increased expression of Bax and PARP and decreased expression of Bcl-2, p-Akt, and p-Cdc2.

Conclusions

CTD accelerates the apoptosis of MG-63 and MNNG/HOS cells in a concentration-dependent manner through the mitochondria-dependent pathway, suggesting that use of CTD is a novel approach for the treatment of osteosarcoma.

Tetrandrine suppresses lung cancer growth and induces apoptosis, potentially via the VEGF/HIF-1α/ICAM-1 signaling pathway

The present study investigated the effect of tetrandrine on lung cancer cell growth and apoptosis, and its possible underlying molecular mechanism. A549 human lung cancer cells were incubated with between 2.5 and 10 µM tetrandrine for 12, 24 and 48 h, following which the effect of tetrandrine on cell viability and apoptosis were assessed using an MTT assay and flow cytometry. ELISA and western blotting were used to analyze VEGF activity, and the expression of poly (ADP-ribose) polymerase (PARP), phosphorylated protein kinase B (Akt), Bcl-2-associated X protein (Bax), hypoxia inducible factor (HIF)-1α and inter-cellular adhesion molecule-1 (ICAM-1). Tetrandrine effectively suppressed the growth of and induced apoptosis in A549 lung cancer cells. The expression of PARP, Bax, intercellular adhesion molecule-1 (ICAM-1) and vascular endothelial growth factor (VEGF) was significantly upregulated, and the phosphorylation of Akt and expression of HIF-1α was significantly suppressed in A549 lung cancer cells. Therefore, tetrandrine may suppress cell viability and induce apoptosis via the VEGF/HIF-1α/ICAM-1 signaling pathway.

Paeoniflorin induces G2/M cell cycle arrest and caspase-dependent apoptosis through the upregulation of Bcl-2 X-associated protein and downregulation of B-cell lymphoma 2 in human osteosarcoma cells

Paeoniflorin (PF), extracted from the peony root, has been proved to possess antineoplastic activity in different cancer cell lines. However, it remains unclear whether PF has an antineoplastic effect against osteosarcoma cells. The present study investigated the effects and the specific mechanism of PF on various human osteosarcoma cell lines. Using the multiple methods to detect the activity of PF on HOS and Saos-2 human osteosarcoma cell lines, including an MTS assay, flow cytometry, transmission electron microscopy and western blotting, it was demonstrated that PF induces inhibition of proliferation, G2/M phase cell cycle arrest and apoptosis in the osteosarcoma cell lines in vitro, and activation of cleaved-caspase-3 and cleaved-poly (ADPribose) polymerase in a dose-dependent manner. Furthermore, the pro-apoptotic factors Bcl-2 X-associated protein and BH3 interacting domain death agonist were uregulated, while the anti-apoptotic factors B-cell lymphoma 2 (Bcl-2) and Bcl-2-extra large were downregulated. In conclusion, these results demonstrated that PF has a promising therapeutic potential in for osteosarcoma.

Design and synthesis of novel C14-urea-tetrandrine derivatives with potent anti-cancer activity

Tetrandrine is a dibenzyltetrahydroisoquinoline alkaloid, isolated from traditional Chinese medicinal plant Stephania tetrandra, with anti-tumor activity. Our previous study identified several derivatives of tetrandrine showing better activities than parental compound against human hepatocellular carcinoma cells. To increase diversity and cytotoxic activities of the original compound, a series of novel 14-urea-tetrandrine derivatives were synthesized through structural modification of tetrandrine. These derivaties demonstrated a moderate to strong anti-proliferative activities against human cell lines HEL and K562 (Leukemia), prostate (PC3), breast (MDA-MB-231) and melanoma (WM9). Compound 4g showed strongest cytotoxic effect against PC3 cells with IC₅₀ value of 0.64 μM, which was 12-fold, 31-fold and 26-fold lower than the parental tetrandrine, 5-fluorouracil and cisplatin, respectively. Preliminary structure-activity relationship study indicated that urea subsititution was the key pharmacophore for the enhancement of their antitumor activities. Induction of apoprosis by 4g was associated with the activation of pro-apoptotic protein BAX and inhibition of antiapoptosis proteins survivin as well as Bcl-2. Moreover, activation of caspases led to increase cleavage of PARP, which further accelerates apoptotic cell death. These results reveal that the compound 4g may be used as a potential anticancer drug candidate.

Therapeutic effect of lymphokine-activated killer cells treated with low-dose ionizing radiation on osteosarcoma

The aim of the present study was to investigate the effect of lymphokine-activated killer (LAK) cells, which received low-dose ionizing radiation, on the treatment of osteosarcoma in rats. The cultured UMR-106 cells were inoculated under the anterior chest skin of 24 rats to establish an osteosarcoma model. In addition, the LAK cells from 24 mice were exposed to doses of 0 (control group), 0.65 or 3.25 mGy X-ray radiation. The tritiated thymidine (³H-TdR) release method and Winn assay were performed to determine the antitumor effects of the LAK cells. The proliferation of the mouse LAK cells treated with 3.25 mGy radiation was significantly higher than that for those treated with 0 or 0.65 mGy radiation, which suggested that low-dose ionizing radiation stimulates the proliferation of LAK cells. The tumor-bearing rats were divided into three groups and injected with LAK cells that had already received 0, 0.65 or 3.25 mGy radiation. The mean survival time of the 3.25-mGy group was longer than that of the 0- and 0.65-mGy groups. After 30 days, tumors with weights of ~6.25 and 2.0 g were identified in the rats of the 0- and 0.65-mGy groups, respectively. However, tumor proliferation was not detectable in the rats of the 3.25-mGy radiation group. Therefore, low-dose ionizing radiation effectively kills osteosarcoma cells in rats by stimulating the proliferation and enhancing the cytotoxicity of LAK cells.

Tetrandrine is a potent cell autophagy agonist via activated intracellular reactive oxygen species

Background

Autophagy is an evolutionarily conserved cellular process that involves the lysosomal degradation of proteins and organelles and the recycling of cellular components to ensure cellular survival under external or internal stress. Numerous data has indicated that autophagy can be successfully targeted for the treatment of multiple cancers. We have previously demonstrated that tetrandrine, a bisbenzylisoquinoline alkaloid isolated from the broadly used Chinese medicinal herb Stephaniae tetrandrae, exhibits potent antitumor effects when used either alone or in combination with other drugs.

Results

In the present study, we showed that tetrandrine is a broad-spectrum potent autophagy agonist. Although low-dose tetrandrine treatment does not affect cell viability, it can potently induce autophagy in a variety of cell lines, including cancerous cells and nontumorigenic cells. The autophagy inhibitors 3-methyladenine (3-MA) and chloroquine (CQ), effectively blocked tetrandrine-induced autophagy. Moreover, tetrandrine significantly triggered the induction of mitophagy. The underlying mechanisms are associated with the tetrandrine-induced production of intracellular reactive oxygen species (ROS), which plays a critical role in tetrandrine-induced autophagy.

Conclusions

Here, we report that tetrandrine is a potent cell autophagy agonist and may have a wide range of applications in the fields of antitumor therapy and basic scientific research.