Calcium channel blocker verapamil accelerates gambogic acid-induced cytotoxicity via enhancing proteasome inhibition and ROS generation

Long-circulating gambogic acid-loaded nanodiamond composite nanosystem with inhibition of cell migration for tumor therapy

Herein, ultra dispersed and stably suspended nanodiamonds (NDs) were demonstrated to have a high load capacity, sustained release, and ability to serve as a biocompatible vehicle for delivery anticancer drugs. NDs with size of 50-100 nm exhibited good biocompatibility in normal human liver (L-02) cells. In particular, 50 nm ND not only promoted the noticeable proliferation of the L-02 cells but also can effectively inhibited the migration of human liver carcinoma (HepG2) cells. The gambogic acid-loaded nanodiamond (ND/GA) complex assembled by π-π stacking exhibits ultrasensitive and apparent suppression efficiency on the proliferation of HepG2 cells through high internalization and less efflux compared to free GA. More importantly, the ND/GA system can significantly increase the intracellular reactive oxygen species (ROS) levels in HepG2 cells and thus induce the cell apoptosis. The increase in intracellular ROS levels causes damage to the mitochondrial membrane potential (MMP) and activates cysteinyl aspartate specific proteinase 3 (Caspase-3) and cysteinyl aspartate specific proteinase 9 (Caspase-9), which leads to the occurrence of apoptosis. In vivo experiments also confirmed that the ND/GA complex has a much higher anti-tumor capability than free GA. Thus, the current ND/GA system is promising for cancer therapy.

Nanoscale Features of Gambogic Acid Induced ROS-Dependent Apoptosis in Esophageal Cancer Cells Imaged by Atomic Force Microscopy

Gambogic acid (GA), a kind of polyprenylated xanthone derived from Garcinia hanburyi tree, has showed spectrum anticancer effects both in vitro and in vivo with low toxicity. However, up to now, there is little information about the effects of GA on esophageal cancer. In this study, we aim to test the anticancer effects of GA on esophageal cancer EC9706 cells. We established a nanoscale imaging method based on AFM to evaluate the reactive oxygen species- (ROS-) mediated anticancer effects of GA on esophageal cancer regarding the morphological and ultrastructural changes of esophageal cancer cells. The obtained results demonstrated that GA could inhibit cell proliferation, induce apoptosis, induce cell cycle arrest, and induce mitochondria membrane potential disruption in a ROS-dependent way. And using AFM imaging, we also found that GA could induce the damage of cellular morphology and increase of membrane height distribution and membrane roughness in EC9706 cells, which could be reversed by the removal of GA-induced excessive intracellular ROS. Our results not only demonstrated the anticancer effects of GA on EC9706 cells in ROS-dependent mechanism but also strongly suggested AFM as a powerful tool for the detection of ROS-mediated cancer cell apoptosis on the basis of imaging.

Different Routes of Administration Lead to Different Oxidative Damage and Tissue Disorganization Levels on the Subacute Cadmium Toxicity in the Liver

The toxic effects of cadmium (Cd) on hepatic parameters are widely described in the literature. Experimental models often make use of the intraperitoneal route (i.p.) because it is easier to apply, while in the oral route, Cd poisoning in humans is best represented by allowing the metal to pass through the digestive system and be absorbed into the bloodstream. Thus, this study investigated the Cd exposure impact on the liver, by comparing both i.p. and oral routes, both in single dose, in addition to the oral route in fractional doses. Swiss adult male mice received CdCl₂ 1.5 mg/kg i.p., 30 mg/kg oral single dose, and 4.28 mg/kg oral route in fractional doses for 7 consecutive days. Cd bioaccumulation was observed in all animals exposed to Cd. Hepatic concentrations of Ca and Fe increased only in the fractionated oral route. Liver activities of SOD and CAT increased only by oral single dose. GST decreased in all forms of oral administration, while MDA decreased only in i.p. route. Liver weight and HSI increased in the i.p. route, while organ volume increased in all forms of oral administration, and liver density increased in all animals exposed to Cd. In hepatic histomorphometry, the changes were more evident in oral administration, mainly in exposure to metal in a single dose. Thus, the subacute administration of Cd in different routes of administration leads to different changes in liver poisoning.

Xanthohumol Induces ROS through NADPH Oxidase, Causes Cell Cycle Arrest and Apoptosis

Reactive oxygen species (ROS) are either toxic in excess or essential for redox signalling at the physiological level, which is closely related to the site of generation. Xanthohumol (XN) is an important natural product of hops (Humulus lupulus L.) and was reported to induce ROS in mitochondria. While in the present study, our data indicate that NADPH oxidase (NOX) is another site. In human acute myeloid leukemia HL-60 cells, we first identified that cell proliferation was inhibited by XN without affecting viability, and this could be alleviated by the antioxidant N-acetyl-L-cysteine (NAC); cell cycles were blocked at G1 phase, apoptosis was induced in a dose-dependent manner, and malondialdehyde (MDA) content was upregulated. XN-induced ROS generation was detected by flow cytometry, which can be inhibited by diphenyleneiodonium chloride (DPI, a NOX inhibitor), while not by N^G-methyl-L-arginine acetate (L-NMMA, a nitric oxide synthase inhibitor). The involvement of NOX in XN-induced ROS generation was further evaluated: immunofluorescence assay indicated subunits assembled in the membrane, and gp91^phox knockdown with siRNA decreased XN-induced ROS. Human red blood cells (with NOX, without mitochondria) were further selected as a cell model, and the XN-induced ROS and DPI inhibiting effects were found again. In conclusion, our results indicate that XN exhibits antiproliferation effects through ROS-related mechanisms, and NOX is a source of XN-induced ROS. As NOX-sourced ROS are critical for phagocytosis, our findings may contribute to the anti-infection and anti-inflammatory effect of XN.

Gambogic acid: A shining natural compound to nanomedicine for cancer therapeutics

The United States Food and Drug Administration has permitted number of therapeutic agents for cancer treatment. Most of them are expensive and have some degree of systemic toxicity which makes overbearing in clinical settings. Although advanced research continuously applied in cancer therapeutics, but drug resistance, metastasis, and recurrence remain unanswerable. These accounts to an urgent clinical need to discover natural compounds with precisely safe and highly efficient for the cancer prevention and cancer therapy. Gambogic acid (GA) is the principle bioactive and caged xanthone component, a brownish gamboge resin secreted from the of Garcinia hanburyi tree. This molecule showed a spectrum of biological and clinical benefits against various cancers. In this review, we document distinct biological characteristics of GA as a novel anti-cancer agent. This review also delineates specific molecular mechanism(s) of GA that are involved in anti-cancer, anti-metastasis, anti-angiogenesis, and chemo-/radiation sensitizer activities. Furthermore, recent evidence, development, and implementation of various nanoformulations of gambogic acid (nanomedicine) have been described.

Gambogenic acid inhibits the proliferation of small‑cell lung cancer cells by arresting the cell cycle and inducing apoptosis

Gambogenic acid (GNA), which is an important active compound present in gamboge, exerts anticancer activity in various types of tumor cells. However, the effect of GNA on small‑cell lung cancer (SCLC) cell lines and the underlying mechanism involved still remain unclear. In the present study, GNA inhibited the proliferation and cell cycle progression of SCLC cells. GNA also promoted the apoptosis of SCLC cells in a dose‑dependent manner, which is associated with modulating the levels of proteins involved in apoptosis pathways in NCI‑H446 and NCI‑H1688 cells. The results demonstrated that GNA increased the level of cleaved caspase‑3, ‑8 and ‑9, and Bax but decreased the expression of anti‑apoptotic protein, Bcl‑2. Furthermore, similar results were obtained in a mouse tumor xenograft model. Additionally, GNA exhibit low toxicity in tissues when administered to mice in the SCLC xenograft models. Collectively, our findings demonstrated that GNA significantly inhibited the proliferation of SCLC cells and promoted cell apoptosis via cell cycle arrest and induction of apoptosis.

Targeting proteasome-associated deubiquitinases as a novel strategy for the treatment of estrogen receptor-positive breast cancer

Estrogen receptor α (ERα) is expressed in ~67% of breast cancers and is critical to their proliferation and progression. The expression of ERα is regarded as a major prognostic marker, making it a meaningful target to treat breast cancer (BCa). However, hormone receptor-positive BCa was sometimes irresponsive or even resistant to classic anti-hormonal therapies (e.g., fulvestrant and tamoxifen). Hence, novel anti-endocrine therapies are urgent for ERα⁺ BCa. A phase II study suggested that bortezomib, an inhibitor blocking the activity of 20 S proteasomes, intervenes in cancer progression for anti-endocrine therapy in BCa. Here we report that proteasome-associated deubiquitinases (USP14 and UCHL5) inhibitors b-AP15 and platinum pyrithione (PtPT) induce growth inhibition in ERα⁺ BCa cells. Further studies show that these inhibitors induce cell cycle arrest and apoptosis associated with caspase activation, endoplasmic reticulum (ER) stress and the downregulation of ERα. Moreover, we suggest that b-AP15 and PtPT block ERα signaling via enhancing the ubiquitin-mediated degradation of ERα and inhibiting the transcription of ERα. Collectively, these findings demonstrate that proteasome-associated deubiquitinases inhibitors b-AP15 and PtPT may have the potential to treat BCa resistant to anti-hormonal therapy.

Emerging small molecule approaches to enhance the antimyeloma benefit of proteasome inhibitors

Multiple myeloma (MM) is a clonal plasma cell malignancy which, despite recent treatment advances, remains incurable in the vast majority of the over 118,000 patients in the USA afflicted with this disease. Treatment of MM has dramatically improved in the past decade with the introduction of new drugs into therapeutic strategies in both the frontline and relapse settings that has led to a significant improvement in the median overall survival (OS). These drugs have been incorporated into clinical guidelines and transformed the treatment approach to MM. Numerous classes of antimyeloma agents, i.e., alkylators, steroids, proteasome inhibitors, immunomodulatory agents, deactylase inhibitors, and monoclonal antibodies, are now FDA-approved and can be combined in doublet or triplet regimens. Moreover, many patients do not respond to therapy and those that do eventually relapse. Emerging therapies that may overcome drug resistance and improve MM treatment include that inhibit regulatory and Ub-processing components of the proteasome, a specialized variant of the proteasome known as the immunoproteasome, proteolysis-targeting chimeric molecules (PROTACS and Degronomids). Emerging strategies also include accessory plasmacytoid dendritic cells (pDCs), vaccines, checkpoint inhibitors, and chimeric antigen receptor-engineered T (CAR-T) cells. Advances in understanding proteasome and plasma cell biology may allow for earlier treatment of MM patients using rationally informed combination therapies with curative potential.

The harsh microenvironment in infarcted heart accelerates transplanted bone marrow mesenchymal stem cells injury: the role of injured cardiomyocytes-derived exosomes

Stem cell therapy can be used to repair and regenerate damaged hearts tissue; nevertheless, the low survival rate of transplanted cells limits their therapeutic efficacy. Recently, it has been proposed that exosomes regulate multiple cellular processes by mediating cell survival and communication among cells. The following study investigates whether injured cardiomyocytes-derived exosomes (cardiac exosomes) affect the survival of transplanted bone marrow mesenchymal stem cells (BMSCs) in infarcted heart. To mimic the harsh microenvironment in infarcted heart that the cardiomyocytes or transplanted BMSCs encounter in vivo, cardiomyocytes conditioned medium and cardiac exosomes collected from H₂O₂-treated cardiomyocytes culture medium were cultured with BMSCs under oxidative stress in vitro. Cardiomyocytes conditioned medium and cardiac exosomes significantly accelerated the injury of BMSCs induced by H₂O₂; increased cleaved caspase-3/caspase-3 and apoptotic percentage, and decreased the ratio of Bcl-2/Bax and cell viability in those cells. Next, we explored the role of cardiac exosomes in the survival of transplanted BMSCs in vivo by constructing a Rab27a knockout (KO) mice model by a transcription activator-like effector nuclease (TALEN) genome-editing technique; Rab27a is a family of GTPases, which has critical role in secretion of exosomes. Male mouse GFP-modified BMSCs were implanted into the viable myocardium bordering the infarction in Rab27a KO and wild-type female mice. The obtained results showed that the transplanted BMSCs survival in infarcted heart was increased in Rab27a KO mice by the higher level of Y-chromosome Sry DNA, GFP mRNA, and the GFP fluorescence signal intensity. To sum up, these findings revealed that the injured cardiomyocytes-derived exosomes accelerate transplanted BMSCs injury in infarcted heart, thus highlighting a new mechanism underlying the survival of transplanted cells after myocardial infarction.

Therapeutic potential of gambogic acid, a caged xanthone, to target cancer

Natural compounds have enormous biological and clinical activity against dreadful diseases such as cancer, as well as cardiovascular and neurodegenerative disorders. In spite of the widespread research carried out in the field of cancer therapeutics, cancer is one of the most prevalent diseases with no perfect treatment till date. Adverse side effects and the development of chemoresistance are the imperative limiting factors associated with conventional chemotherapeutics. For this reason, there is an urgent need to find compounds that are highly safe and efficacious for the prevention and treatment of cancer. Gambogic acid (GA) is a xanthone structure extracted from the dry, brownish gamboge resin secreted from the Garcinia hanburyi tree in Southeast Asia and has inherent anti-cancer properties. In this review, the molecular mechanisms underlying the targets of GA that are liable for its effective anti-cancer activity are discussed that reveal the potential of GA as a pertinent candidate that can be appropriately developed and designed into a capable anti-cancer drug.

CDKN2B is critical for verapamil-mediated reversal of doxorubicin resistance in hepatocellular carcinoma

In this study, we explored the function and mechanism of CDKN2B genes in verapamil (VER)-induced reversal of resistance to doxorubicin (ADM) chemotherapy in hepatocellular carcinoma (HCC). We examined 4 HCC cell lines and found that the expression levels of CDKN2B genes correlated with the level of apoptosis induced by ADM+VER. Overexpression of CDKN2B genes promoted apoptosis in cells treated with VER+ADM. CDKN2B knockdown using siRNA weakened the effect of ADM+VER, indicating that ADM+VER promotes HCC cell apoptosis and that CDKN2B genes participate in VER-mediated promotion in tumor cell apoptosis. Future research will further explore the functional mechanism, and the associated signal transduction pathways via which CDKN2B affects HCC drug resistance.

Longikaurin E induces apoptosis of pancreatic cancer cells via modulation of the p38 and PI3K/AKT pathways by ROS

Pancreatic cancer is a devastating disease with a poor prognosis. It ranks as the fourth or fifth most common cancer in men and women and has the lowest 5-year survival rate. Therefore, there is an urgent need to develop novel therapeutic agents for pancreatic cancer. Longikaurin E (LE), which is derived from the traditional herbal medicine Rabdosia longituba, had been reported to have anti-proliferative and pro-apoptotic properties in several types of cancers. In this study, we investigated the cytotoxic properties of LE against pancreatic cancer cells and explored the mechanism behind the observed apoptosis. Pancreatic cancer cell lines cultured in the presence of LE exhibited dose- and time-dependent growth suppression by clone formation, methylthiazoltetrazolium assay, lactate dehydrogenase cytotoxicity assay, and fluorescence-activated cell sorting analysis, respectively. In addition, these culture conditions also induced the generation of cellular reactive oxygen species (ROS). In order to determine the mechanisms underlying LE-induced cytotoxicity, we used reverse transcription polymerase chain reaction and Western blot analysis in the pancreatic cancer cell line PANC1. The results showed that the expression of Bax was noticeably upregulated and the expression levels of Bcl-2, Bcl-XL, survivin, and c-Myc were significantly downregulated. We also observed increased p38 phosphorylation and decreased phosphorylation of the PI3K/AKT pathway. Interestingly, we also found that LE activated caspase-3. However, N-acetyl-L-cysteine, a kind of antioxidant, reversed all of these cellular activities. In conclusion, this study suggested that LE induced apoptosis of pancreatic cancer cells via ROS generation to modulate the p38 and PI3K/AKT pathways and could be a promising anti-pancreatic agent.

Apoptosis induction associated with the ER stress response through up-regulation of JNK in HeLa cells by gambogic acid

Background

Gambogic acid (GA) was extracted from the dried yellow resin of gamboge (Garcinia hanburyi) which is traditionally used as a coloring material for painting and cloth dying. Gamboge has been also used as a folk medicine for an internal purgative and externally infected wound. We focused on the mechanisms of apoptosis induction by GA through the unfold protein response (ER stress) in HeLa cells.

Methods

The cytotoxic effect of GA against HeLa cells was determined by trypan blue exclusion assay. Markers of ER stress such as XBP-1, GRP78, CHOP, GADD34 and ERdj4 were analyzed by RT-PCR and Real-time RT-PCR. Cell morphological changes and apoptotic proteins were performed by Hoechst33342 staining and Western blotting technique.

Results

Our results indicated a time- and dose-dependent decrease of cell viability by GA. The ER stress induction is determined by the up-regulation of spliced XBP1 mRNA and activated GRP78, CHOP, GADD34 and ERdj4 expression. GA also induced cell morphological changes such as nuclear condensation, membrane blebbing and apoptotic body in Hela cells. Apoptosis cell death detected by increased DR5, caspase-8, −9, and −3 expression as well as increased cleaved-PARP, while decreased Bcl-2 upon GA treatment. In addition, phosphorylated JNK was up-regulated but phosphorylated ERK was down-regulated after exposure to GA.

Conclusions

These results suggest that GA induce apoptosis associated with the ER stress response through up-regulation of p-JNK and down-regulation of p-ERK in HeLa cells.

A Novel Exploration of a Combination of Gambogic Acid with TiO₂ Nanofibers: The Photodynamic Effect for HepG2 Cell Proliferation

As a good photosensitizer, TiO₂ nanomaterials show potential biomedical applications, such as drug carriers or enhancers in photodynamic therapy. In this contribution, novel nanocomposites through the blending of TiO₂ nanofibers with the active compound, gambogic acid (GA), were explored, and the results showed that GA could inhibit cancer cell proliferation in a time-dependent and dose-dependent manner, inducing apoptosis and cell cycle arrest at the G0/G1 phase in HepG2 cells. It is evident that after the GA-TiO₂ nanocomposites were cultured with the cancer cells, the cooperation effect could effectively enhance the cytotoxicity of GA for HepG2 cells. Meanwhile, if activated by UV irradiation, under the presence of GA-TiO₂ nanocomposites, this would lead to significant apoptosis and necrosis for HepG2 cells with a photodynamic therapy (PDT) effect. Associated with the controlled drug-release from these nanocomposites, TiO₂ nanofibers could readily cut down the drug consumption in HepG2 cells and reduce the side-effect for the normal cells and tissue, which may be further utilized in the therapeutic alliance for cancer therapy.