Viability inhibition effect of gambogic acid combined with cisplatin on osteosarcoma cells via mitochondria-independent apoptotic pathway

AATF is Overexpressed in Human Bladder Cancer and Regulates Chemo-Sensitivity Through Survivin

Objective

Dysregulation of apoptosis antagonizing transcription factor (AATF) has been reported to be closely associated with human cancers. However, its involvement in human bladder cancer (BC) remains unexplored. This study aimed to investigate the clinical significance and biological roles of AATF in human bladder cancers.

Methods

AATF protein expression was examined in 107 cases of bladder cancer tissues using immunohistochemistry. AATF plasmid transfection and small interfering RNA (siRNA) knockdown were performed in T24 and 5637 cell lines. CCK-8, colony formation, annexin V/PI, JC-1 staining, and Western blotting were carried out to investigate the biological roles and underlying mechanisms of AATF in bladder cancer cells.

Results

Our results showed that AATF expression was upregulated in human bladder cancer specimens and correlated with T stage. Analysis of the Oncomine database showed elevation of AATF mRNA in BC tissues. The Cancer Genome Atlas (TCGA) data suggested that high AATF expression correlated with poor patient survival. Western blotting showed that AATF protein expression was higher in BC cell lines compared to normal bladder transitional epithelial cell line SV-HUC-1. CCK-8 and colony assays showed that ectopic AATF expression upregulated cell growth rate and colony numbers. CCK-8, annexin V/propidium iodide (PI), JC-1 assays and Western blotting showed that AATF overexpression decreased cisplatin sensitivity, downregulated cisplatin-induced apoptosis and upregulated mitochondrial membrane potential, with decreased cytochrome c and cleaved-PARP expression. AATF siRNA knockdown showed the opposite effects. Mechanistically, AATF overexpression upregulated cyclin E and Survivin at both mRNA and protein levels. The decreased cisplatin sensitivity/apoptosis induced by ectopic AATF were reversed after treatment with Survivin inhibitor YM155.

Conclusion

Our results showed that AATF was overexpressed in human bladder cancers and promoted malignant behavior by regulating cyclin E and Survivin, indicating AATF could serve as a malignant biomarker and potential therapeutic target in BC.

Daam1 Overexpression Promotes Gastric Cancer Progression and Regulates ERK and AKT Signaling Pathways

Objective

The dishevelled-associated activator of morphogenesis 1 (DAAM1) has been reported to be closely associated with human cancers. However, its involvement in human gastric cancer (GC) remains largely unexplored. This study aimed to investigate the clinical significance and biological roles of Daam1 in human GC.

Methods

Daam1 protein expression was examined in 124 cases of gastric adenocarcinomas using immunohistochemistry. Daam1 plasmid and siRNA transfection were carried out in SGC7901 and AGS cell lines. CCK-8, colony formation, Annexin V/PI, JC-1 staining, and Western blotting were used to explore the biological functions and potential underlying mechanisms of Daam1 in GC cells.

Results

Our results showed that Daam1 was overexpressed in GC specimens. A high Daam1 level was associated with tumor-node-metastasis (TNM) stage, T status, nodal metastasis, and poor patient survival. Analysis of the Oncomine dataset revealed upregulation of Daam1 mRNA in GC tissues. Western blot showed that Daam1 protein expression was higher in GC cell lines compared to the normal GES-1 cell line. CCK-8 and colony formation assays showed that ectopic Daam1 expression upregulated the cell growth rate and colony number in SGC-7901 cells, while Daam1 siRNA knockdown downregulated the growth rate and colony number in AGS cells. CCK-8 and Annexin V/PI apoptosis assays demonstrated that Daam1 overexpression decreased cisplatin sensitivity and downregulated cisplatin-induced apoptosis. JC1 staining showed that Daam1 overexpression upregulated, while Daam1 depletion downregulated mitochondrial membrane potential. Mechanistically, Daam1 overexpression downregulated p21 and upregulated p-ERK and p-AKT. The increased proliferation rate and decreased cisplatin sensitivity/apoptosis induced by ectopic Daam1 were reversed after treatment with AKT and ERK inhibitors.

Conclusion

Taken together, our results showed that Daam1 overexpression was associated with poor prognosis and promoted malignant activity via regulation of ERK and AKT pathways in GC cells, indicating Daam1 is a malignant biomarker and potential therapeutic target in GC.

Differential effects of cisplatin combined with the flavonoid apigenin on HepG2, Hep3B, and Huh7 liver cancer cell lines

The potential of apigenin (APG) to enhance cisplatin's (CDDP) chemotherapeutic efficacy was investigated in HepG2, Hep3B, and Huh7 liver cancer cell lines. The presence of 20 μM APG sensitized all cell lines to CDDP treatment (degree of sensitization based on the MTT assay: HepG2>Huh7>Hep3B). As reflected by sister chromatid exchange levels, the degree of genetic instability as well as DNA repair by homologous recombination differed among cell lines. CDDP and 20 μM APG cotreatment exhibited a synergistic genotoxic effect on Hep3B cells and a less than additive effect on HepG2 and Huh7 cells. Cell cycle delays were noticed during the first mitotic division in Hep3B and Huh7 cells and the second mitotic division in HepG2 cells. CDDP and CDDP + APG treatments reduced the clonogenic capacity of all cell lines; however, there was a discordance in drug sensitivity compared with the MMT assay. Furthermore, a senescence-like phenotype was induced, especially in Hep3B and Huh7 cells. Unlike CDDP monotherapy, the combined treatment exhibited a significant anti-invasive and anti-migratory action in all cancer cell lines. The fact that the three liver cancer cell lines responded differently, yet positively, to CDDP + APG cotreatment could be attributed to variations they present in gene expression. Complex mechanisms seem to influence cellular responses and cell fate.

BCAT1 overexpression regulates proliferation and c‑Myc/GLUT1 signaling in head and neck squamous cell carcinoma

Branched chain amino acid transaminase 1 (BCAT1) overexpression has been reported in various cancers; however, at present, its significance and biological role in head and neck squamous cell carcinoma (HNSCC) remain unknown. BCAT1 protein expression was upregulated in 56/106 (52.8%) cases of HNSCC. BCAT1 overexpression was associated with tumor-node-metastasis stage, tumor stage and nodal metastasis. The Cancer Genome Atlas data suggested that high BCAT1 expression was associated with poor patient survival. Oncomine data suggested that BCAT1 expression was increased in HNSCC. Functionally, BCAT1 overexpression promoted cell proliferation, colony formation, invasion and cisplatin resistance in FaDu cells. BCAT1 overexpression also upregulated the mitochondrial membrane potential, and increased ATP production, glucose consumption and glucose uptake. Western blotting demonstrated that BCAT1 overexpression upregulated c-Myc and glucose transporter 1 (GLUT1) protein levels. Depletion of c-Myc using small interfering RNA abolished the influence of BCAT1 on GLUT1. Chromatin immunoprecipitation assays demonstrated that c-Myc has binding sites in the GLUT1 promoter. Collectively, the present findings suggested that BCAT1 is upregulated in human HNSCC and regulates HNSCC cell proliferation, invasion, cisplatin sensitivity and c-Myc/GLUT1 signaling.

Gambogic Acid as a Candidate for Cancer Therapy: A Review

Gambogic acid (GA), a kind of dry resin secreted by the Garcinia hanburyi tree, is a natural active ingredient with various biological activities, such as anti-cancer, anti-inflammatory, antioxidant, anti-bacterial effects, etc. An increasing amount of evidence indicates that GA has obvious anti-cancer effects via various molecular mechanisms, including the induction of apoptosis, autophagy, cell cycle arrest and the inhibition of invasion, metastasis, angiogenesis. In order to improve the efficacy in cancer treatment, nanometer drug delivery systems have been employed to load GA and form micelles, nanoparticles, nanofibers, and so on. In this review, we aim to offer a summary of chemical structure and properties, anti-cancer activities, drug delivery systems and combination therapy of GA, which might provide a reference to promote the development and clinical application of GA.

Rab11a Is Overexpressed in Gastric Cancer and Regulates FAK/AKT Signaling

Dysregulation of Rab11a has been implicated in the progression of several cancers. However, there have been no such studies for human gastric cancers. In the current study, we examined Rab11a protein expression and found it was upregulated in 49 of 108 gastric cancer tissues and correlated with local invasion, nodal metastasis, and advanced stage. Rab11a protein was higher in gastric cancer cell lines than normal gastric cell line. We transfected Rab11a plasmid and siRNA in both MGC803 and AGS cell lines. Rab11a overexpression increased the cell growth rate, colony numbers, and invasion ability in both MGC803 and AGS cell lines. Downregulation of Rab11a using siRNA decreased the cell proliferation rate, colony numbers, and inhibited invasion. Rab11a overexpression also conferred cisplatin resistance. Annexin V/PI staining showed that Rab11a overexpression suppressed cisplatin-induced apoptosis, while Rab11a depletion promoted cell apoptosis. We also showed that Rab11a overexpression maintained mitochondrial membrane potential. Western blot analysis revealed that Rab11a increased protein expression of MMP2, cyclin D1, Bcl-2, p-FAK, and p-AKT, while Rab11a depletion showed the opposite effects. Blockage of FAK using inhibitor downregulated Bcl-2, cyclin D1, MMP2, and p-AKT expression and abolished the effects of Rab11a on these proteins. In summary, our data demonstrated that Rab11a is upregulated in human gastric cancers. Rab11a facilitated cell proliferation and invasion, as well as cisplatin sensitivity and mitochondrial membrane potential, possibly via the FAK/AKT signaling pathway.

Rab18 Regulates Proliferation, Invasion and Cisplatin Sensitivity Through STAT3 Signaling in Head and Neck Squamous Cell Carcinoma

Introduction

The clinical significance, biological roles and potential mechanism of Rab18 remain unknown in most human cancers, including head and neck squamous cell carcinoma (HNSCC).

Methods

We used immunohistochemistry to examine Rab18 protein expression in 112 cases of HNSCC specimens. We overexpressed and knockdown Rab18 in FaDu and Detroit562 cancer cell lines. Biological roles and mechanisms of Rab18 were examined using MTT, colony formation, Matrigel invasion assay, Western blotting, Annexin V and JC1 staining.

Results

Rab18 was upregulated in 45/112 (40.2%) cases of HNSCC tissues, which correlated with advanced T classification, positive nodal metastasis and tumor node metastasis (TNM) stage. The Oncomine and The Cancer Genome Atlas (TCGA) analyses indicated that Rab18 was elevated in human HNSCC tissues and correlated with poor patient survival. Functionally, Rab18 overexpression increased growth rate, colony numbers, cell cycle progression and invading ability in FaDu cells. Rab18 downregulated cisplatin-induced apoptosis and upregulated the mitochondrial membrane potential (Δψm). Western blot revealed that Rab18 overexpression induced epithelial-to-mesenchymal transition, with downregulation of E-cadherin and upregulation of N-cadherin, Vimentin and Twist. Rab18 overexpression also upregulated Survivin protein and Rab18 knockdown showed the opposite effects on these proteins. Treatment of STAT3 inhibitor, SH-4-54, inhibited cell invasion, increased E-cadherin and downregulated N-cadherin, Twist and Survivin. SH-4-54 also abolished the effects of BCAT1 on these proteins, as well as cell invasion.

Conclusion

In summary, our data showed that Rab18 was overexpressed in human HNSCC and functioned as an oncoprotein. Rab18 regulated HNSCC cell proliferation, invasion and cisplatin sensitivity through STAT3 signaling in HNSCC.

Sirt5 Attenuates Cisplatin-Induced Acute Kidney Injury through Regulation of Nrf2/HO-1 and Bcl-2

Cisplatin- (CDDP) induced acute kidney injury (AKI) limits the clinical use of cisplatin. Several sirtuin (SIRT) family proteins are involved in AKI, while the roles of Sirt5 in cisplatin-induced AKI remain unknown. In the present study, we characterized the role and mechanism of Sirt5 in cisplatin-induced apoptosis using the human kidney 2 (HK-2) cell line. CDDP treatment decreased Sirt5 expression of HK-2 cells in a dose-dependent manner. In addition, Sirt5 overexpression enhanced the metabolic activity in CDDP-treated HK-2 cells while Sirt5 siRNA attenuated it. Forced expression of Sirt5 inhibited CDDP-induced apoptosis while Sirt5 siRNA showed the opposite effects. Accordingly, Sirt5 overexpression inhibited the level of caspase 3 cleavage and cytochrome c levels. Furthermore, we found that Sirt5 increased mitochondrial membrane potentials and ameliorated intracellular ROS production. Mitotracker Red staining indicated that Sirt5 overexpression was able to maintain the mitochondrial density during CDDP treatment. We also investigated possible downstream targets of Sirt5 and found that Sirt5 increased Nrf2, HO-1, and Bcl-2 while it decreased Bax protein expression. Sirt5 siRNA showed the opposite effect on these proteins. The levels of Nrf2, HO-1, and Bcl-2 proteins in HK-2 cells were also decreased after CDDP treatment. Moreover, Nrf2 and Bcl-2 siRNA partly abolished the protecting effect of Sirt5 on CDDP-induced apoptosis and cytochrome c release. Catalase inhibitor 3-AT also abolished the cytoprotective effect of Sirt5. Together, the results demonstrated that Sirt5 attenuated cisplatin-induced apoptosis and mitochondrial injury in human kidney HK-2 cells, possibly through the regulation of Nrf2/HO-1 and Bcl-2.

TRIM32 overexpression improves chemoresistance through regulation of mitochondrial function in non-small-cell lung cancers

Background

TRIM32 is overexpressed in several human cancers. However, its expression pattern, biological characteristics and mechanisms in human non-small cell lung cancer (NSCLC) have not been reported.

Methods

We examined TRIM32 protein in 115 cases of NSCLC specimens. TRIM32 plasmid transfection and siRNA knockdown was carried out in NSCLC cell lines. AnnexinV/PI and JC-1 staining were performed to examine the change of apoptosis and mitochondrial membrane potential. Western blot was used to detect change of downstream proteins.

Results

We found that TRIM32 protein was upregulated in 69 cases and positively correlated with advanced TNM stage. TRIM32 overexpression also correlated with poor survival of NSCLC patients. Biological assays demonstrated that TRIM32 overexpression promoted while it depletion inhibited cell growth, colony formation and invasion. In addition, TRIM32 maintained NSCLC cell viability and reduced apoptosis when treated with cisplatin. JC-1 and CellRox staining demonstrated that TRIM32 could maintain mitochondrial membrane potential and reduce Reactive Oxygen Species (ROS) production after cisplatin treatment. Western blot analysis showed that TRIM32 overexpression downregulated caspase 3 cleavage and cytochrome c release. TRIM32 also positively regulated Bcl-2 protein expression and NF-κB signaling. Inhibition of NF-κB abolished the effects of TRIM32 on Bcl-2.

Conclusion

Taken together, our results indicated that TRIM32 is overexpressed in NSCLC and regulates cisplatin resistance, possibly through NF-κB and Bcl-2.

Rab18 overexpression promotes proliferation and chemoresistance through regulation of mitochondrial function in human gastric cancer

Background

Dysregulation of Rab18 has been implicated in human cancers. However, its clinical significance and biological function in gastric cancer have not been investigated.

Methods

We examined Rab18 expression in gastric cancer tissues using immunohistochemistry. We used SNU-1 and AGS cell lines for plasmid and siRNA transfection respectively. MTT, colony formation assay, cell cycle analysis, matrigel invasion, wound healing assay, AnnexinV/PI analysis and western blotting were used to examine the biological effect and mechanism of Rab18 in gastric cancer cell lines.

Results

Rab18 protein expression was upregulated in gastric cancer tissues and this correlated with advanced stage and poor prognosis. Rab18 overexpression promoted proliferation in vitro and in vivo. Cell cycle analysis showed that Rab18 overexpression upregulated, while its depletion downregulated S phase percentage. Matrigel invasion and wound healing assays indicated that Rab18 positively regulated SNU-1 cell invasion and migration while its knockdown inhibited AGS cell invasion and migration. Rab18 maintained cell viability and downregulated apoptosis after cisplatin treatment, with upregulated mitochondrial membrane potential and downregulated mitochondrial reactive oxygen species (ROS) production. Rab18 overexpression upregulated p-Rb, survivin while downregulated cytochrome c, cleaved caspase-3 and cleaved PARP.

Conclusion

In conclusion, our results indicate that Rab18 promoted gastric cancer growth and chemoresistance, possibly through regulation of mitochondrial function and survivin.

Synergistic inhibitory effects of capsaicin combined with cisplatin on human osteosarcoma in culture and in xenografts

BACKGROUND

The combination of phytochemicals with chemotherapy drugs is an emerging new strategy for cancer therapy to increase antitumor responses.

METHODS

The present study investigates the effect of the combination of capsaicin (CAP) with cisplatin (DDP) and the potential underlying anticancer mechanisms in osteosarcoma (OS) cells in vitro and in vivo.

RESULTS

Cell viability assays and isobolographic analyses demonstrated that the combination of CAP and DDP showed synergistic cytotoxic effects on OS cells. We chose relatively low concentrations of CAP (100 μM) and DDP (16.7 μM) for subsequent experiments. Generally, the combination of CAP and DDP had significant effects on apoptosis induction, cell cycle arrest and cell invasion inhibition in OS cells compared with the individual-treatment groups and the control group. Moreover, cotreatment with CAP and DDP triggered prosurvival autophagy through reactive oxygen species (ROS)/JNK and p-AKT/mTOR signaling in OS cells. The combination regimen of CAP and DDP also inhibited tumor growth in an OS xenograft model.

CONCLUSION

These results suggest that the combination of CAP and DDP has strong inhibitory effects on OS cells and identify CAP as a promising agent for supplementing standard chemotherapy and possible future targeted therapy in OS.

Cell-penetrating peptide conjugates of gambogic acid enhance the antitumor effect on human bladder cancer EJ cells through ROS-mediated apoptosis

Background

Gambogic acid (GA) is the main active ingredient of resin gamboges and possesses anti-cancer activity toward various human cancer cells. However, clinical application of GA has been limited by its poor aqueous solubility and dose-limiting toxicities. Cell-penetrating peptides (CPPs) are widely used to deliver anti-cancer drugs into cancer cells and to enhance the water solubility of drugs.

Purpose

The object of this study was to synthesize peptide-drug conjugates in which the cell-penetrating peptide TAT (trans-activator of transcription) was conjugated to GA and evaluated the anti-cancer activity of this GA-CPP conjugate (GA-TAT) in EJ bladder cancer cells.

Methods

GA is built onto the TAT, and the GA-TAT conjugates are cleaved from the solid support and purified via HPLC. The equilibrium solubility of GA-TAT was measured using the shake-flask method. The effects of GA-TAT on EJ cell viability and proliferation were determined by MTT assay, Edu assay and colony formation assay, respectively. After treated with 1.0 μM GA-TAT for 24 h, the apoptosis rate of EJ cells were detected by Acridine orange/ethidium bromide (AO/EB) assay and flow cytometry assay. The proteins of caspase-3 (processing), caspase-9 (processing), Bcl-2 and Bax were analyzed by Western blotting, and the intracellular reactive oxygen species (ROS) production was evaluated by a reactive oxygen species assay.

Results

In contrast to free GA, the solubility of GA-TAT in water was significantly improved. Meanwhile, GA-TAT significantly increased EJ cellular uptake, toxicity and apoptosis. Mechanistic analysis revealed that GA-TAT enhanced the anti-cancer effect of GA against EJ cells through ROS-mediated apoptosis. The results were demonstrated that GA-TAT increased the ROS level in EJ cells, and N-acetyl-L-cysteine (NAC; a well-known ROS scavenger) inhibited GA-TAT-induced ROS generation and apoptosis. Additionally, GA-TAT activated caspase-3 and caspase-9 and down-regulated the Bcl-2/Bax ratio, but these effects were largely rescued by NAC.

Conclusion

GA-TAT has outstanding potential for promoting tumor apoptosis and exhibits promise for use in bladder cancer therapy.

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.

Telomerase reverse transcriptase promotes chemoresistance by suppressing cisplatin-dependent apoptosis in osteosarcoma cells

Cisplatin is one of the most efficacious antimitotic drugs used in the treatment of a range of malignant tumors. However, treatment failures are common due to the development of chemoresistance. In addition to its telomere maintenance function, telomerase plays a pro-survival role, inducing decreased apoptosis and increased resistance against DNA damage. Elucidation of the molecular mechanisms underlying this effect is critical to improve treatment outcomes. Previously, our group showed higher telomerase reverse transcriptase(TERT) expression in cisplatin resistant osteosarcoma cells. In this study, confocal fluorescence microscopy experiments revealed that TERT translocates from the nucleus to mitochondria in cisplatin treated osteosarcoma cells. We observed decreased apoptosis rate and improved mitochondrial function in TERT-overexpressing cells following cisplatin treatment. Based on these results, we further established that TERT inhibits cisplatin-induced apoptosis independently of telomerase reverse transcriptase activity. Moreover, TERT suppressed cisplatin-induced apoptosis and improved mitochondrial function via alleviating intracellular ROS in osteosarcoma cells. Our finding that TERT shuttles from the nucleus to the mitochondrion in response to cisplatin treatment and inhibits cisplatin-induced apoptosis in osteosarcoma cells may be especially important to overcome drug resistance.

Inhibition of inwardly rectifying Kir2.x channels by the novel anti-cancer agent gambogic acid depends on both pore block and PIP2 interference

The caged xanthone gambogic acid (GA) is a novel anti-cancer agent which exhibits anti-proliferative, anti-inflammatory and cytotoxic effects in many types of cancer tissues. In a recent phase IIa study, GA exhibits a favourable safety profile. However, limited data are available concerning its interaction with cardiac ion channels. Heteromeric assembly of Kir2.x channels underlies the cardiac inwardly rectifying I_K1 current which is responsible for the stabilization of the diastolic resting membrane potential. Inhibition of the cardiac I_K1 current may lead to ventricular arrhythmia due to delayed afterdepolarizations. Compared to Kv2.1, hERG and Kir1.1, a slow, delayed inhibition of Kir2.1 channels by GA in a mammalian cell line was reported before but no data exist in literature concerning action of GA on homomeric Kir2.2 and Kir2.3 and heteromeric Kir2.x channels. Therefore, the aim of this study was to provide comparative data on the effect of GA on homomeric and heteromeric Kir2.x channels. Homomeric and heteromeric Kir2.x channels were heterologously expressed in Xenopus oocytes, and the two-microelectrode voltage-clamp technique was used to record Kir2.x currents. To investigate the mechanism of the channel inhibition by GA, alanine-mutated Kir2.x channels with modifications in the channels pore region or at phosphatidylinositol 4,5-bisphosphate (PIP₂)-binding sites were employed. GA caused a slow inhibition of homomeric and heteromeric Kir2.x channels at low micromolar concentrations (with IC₅₀ Kir2.1/2.2 < Kir2.2 < Kir2.2/2.3 < Kir2.3 < Kir2.1 < Kir2.1/2.3). The effect did not reach saturation within 60 min and was not reversible upon washout for 30 min. The inhibition showed no strong voltage dependence. We provide evidence for a combination of direct channel pore blockade and a PIP₂-dependent mechanism as a molecular basis for the observed effect. We conclude that Kir2.x channel inhibition by GA may be relevant in patients with pre-existing cardiac disorders such as chronic heart failure or certain rhythm disorders and recommend a close cardiac monitoring for those patients when treated with GA.

Gambogic acid inhibits the growth of ovarian cancer tumors by regulating p65 activity

Ovarian cancer patients often have poor prognosis, therefore, it is important to search for more effective therapeutic strategies to treat them. Gambogic acid (GA) exhibits an anti-tumor effect through various mechanisms, and has multiple targets in tumor cells. The present study aimed to elucidate the efficacy of GA in the treatment of ovarian cancer both in vivo and in vitro by analyzing its impact on cell survival and tumor growth through cell cycle and apoptosis analysis. GA inhibited the growth of ovarian cancer cells in a dose and time dependent manner, and arrested the cell cycle in ovarian cancer cells. Furthermore, GA increased caspase-3 and caspase-9 activity and inhibited RELA/NF-κB p65 (p65) DNA binding activity. Finally, GA suppressed tumor growth in vivo. Therefore, the current study suggests that GA inhibits the growth of ovarian cancer by regulating p65 activity, and may be developed as a novel therapeutic strategy to treat ovarian cancer.

Alpha-phellandrene-induced apoptosis in mice leukemia WEHI-3 cells in vitro

Although reports have shown that α-phellandrene (α-PA) is one of the monoterpenes and is often used in the food and perfume industry, our previous studies have indicated that α-PA promoted immune responses in normal mice in vivo. However, there is no available information to show that α-PA induced cell apoptosis in cancer cells, thus, we investigated the effects of α-PA on the cell morphology, viability, cell cycle distribution, and apoptosis in mice leukemia WEHI-3 cells in vitro. Results indicated that α-PA induced cell morphological changes and decreased viability, induced G0/G1 arrest and sub-G1 phase (apoptosis) in WEHI-3 cells. α-PA increased the productions of reactive oxygen species (ROS) and Ca²⁺ and decreased the levels of mitochondrial membrane potential (ΔΨ_m ) in dose- and time-dependent manners in WEHI-3 cells that were analyzed by flow cytometer. Results from confocal laser microscopic system examinations show that α-PA promoted the release of cytochrome c, AIF, and Endo G from mitochondria in WEHI-3 cells. These results are the first findings to provide new information for understanding the mechanisms by which α-PA induces cell cycle arrest and apoptosis in WEHI-3 cells in vitro. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1640-1651, 2016.

Hypoxia-induced resistance to cisplatin-mediated apoptosis in osteosarcoma cells is reversed by gambogic acid independently of HIF-1α

In vitro evidence of hypoxia-induced resistance to cisplatin (CDDP)-mediated apoptosis exists in human osteosarcoma (OS). Gambogic acid (GA) is a promising chemotherapeutic compound that could increase the chemotherapeutic effectiveness of CDDP in human OS cells by inducing cell cycle arrest and promoting apoptosis. This study examined whether GA could overcome OS cell resistance to CDDP. Hypoxia significantly reduced levels of CDDP-induced apoptosis in the OS cell lines MG63 and HOS. However, combined treatment with GA and CDDP revealed a strong synergistic action between these drugs, and higher protein levels of the apoptosis-related factor Fas, cleaved caspase-8 and cleaved caspase-3 and lower expression of hypoxia-inducible factor (HIF)-1α are detected in both cell lines. Meanwhile, drug resistance was not reversed by exposure to the HIF-1α inhibitor 2-methoxyestradiol. These findings strongly suggest that hypoxia-induced resistance to CDDP is reversed by GA in OS cells independently of HIF-1α. Furthermore, in vivo studies using xenograft mouse models revealed that combination therapy with CDDP and GA exerted increased antitumor effects by inducing apoptosis. Taken together, our results demonstrate that GA may be a new potent therapeutic agent useful for targeting human OS cells.

Combination of gambogic acid with cisplatin enhances the antitumor effects on cisplatin-resistant lung cancer cells by downregulating MRP2 and LRP expression

Cisplatin resistance is a main clinical problem of lung cancer therapy. Gambogic acid (GA) could prohibit the proliferation of a variety of human cancer cells. However, the effects of GA on cisplatin-resistant lung cancer are still unclear. The objective of the present study was to find out the antitumor effects of GA on cisplatin-resistant human lung cancer A549/DDP cells and further explore its underlying mechanisms. Cell Counting Kit-8 assay was used to observe the impacts of GA and/or cisplatin on the proliferation of lung cancer cells; flow cytometry was used to detect the effects of GA on cell cycle and apoptosis; Western blot was used to examine the effects of GA on the expression of lung resistance protein (LRP) and multidrug resistance-associated protein 2 (MRP2) protein in A549/DDP cells. Our results showed that GA dose- and time-dependently prohibited the proliferation and induced significant cell apoptosis in A549 and A549/DDP cells. GA also induced G0/G1 arrest in both A549/DDP and A549 cells. Moreover, GA upregulated protein expression level of cleaved caspase-3 and Bax and downregulated protein expression level of pro-caspase-9 and Bcl-2 in time- and dose-dependent way in A549/DDP cells. GA combined with cisplatin enhanced the cells apoptotic rate and reduced the cisplatin resistance index in A549/DDP cells. In addition, GA reduced the MRP2 and LRP protein expression level in A549/DDP cells. GA inhibits the proliferation, induces cell cycle arrest and apoptosis in A549/DDP cells. Combination of GA with cisplatin enhances the antitumor effects on cisplatin-resistant lung cancer cells by downregulating MRP2 and LRP expression.

Gambogic acid potentiates clopidogrel-induced apoptosis and attenuates irinotecan-induced apoptosis through down-regulating human carboxylesterase 1 and -2

1. In this study, we report that gambogic acid (GA), a promising anticancer agent, potentiates clopidogrel-induced apoptosis and attenuates CPT-11-induced apoptosis by down-regulating human carboxylesterase (CES) 1 and -2 via ERK and p38 MAPK pathway activation, which provides a molecular explanation linking the effect of drug combination directly to the decreased capacity of hydrolytic biotransformation. 2. The expression levels of CES1 and CES2 decreased significantly in a concentration- and time-dependent manner in response to GA in Huh7 and HepG2 cells; hydrolytic activity was also reduced. 3. The results showed that pretreatment with GA potentiated clopidogrel-induced apoptosis by down-regulating CES1. Moreover, the GA-mediated repression of CES2 attenuated CPT-11-induced apoptosis. 4. Furthermore, the ERK and p38 MAPK pathways were involved in the GA-mediated down-regulation of CES1 and CES2. 5. Taken together, our data suggest that GA is a potent repressor of CES1 and CES2 and that combination with GA will affect the metabolism of drugs containing ester bonds.

Gambogic acid inhibits growth, induces apoptosis, and overcomes drug resistance in human colorectal cancer cells

The emergence of chemoresistance is a major limitation of colorectal cancer (CRC) therapies and novel biologically based therapies are urgently needed. Natural products represent a novel potential anticancer therapy. Gambogic acid (GA), a small molecule derived from Garcinia hanburyi Hook. f., has been demonstrated to be highly cytotoxic to several types of cancer cells and have low toxicity to the hematopoietic system. However, the potential role of GA in colorectal cancer and its ability to overcome the chemotherapeutic resistance in CRC cells have not been well studied. In the present study, we showed that GA directly inhibited proliferation and induced apoptosis in both 5-fluorouracil (5-FU) sensitive and 5-FU resistant colorectal cancer cells; induced apoptosis via activating JNK signaling pathway. The data, therefore, suggested an alternative strategy to overcome 5-FU resistance in CRC and that GA could be a promising medicinal compound for colorectal cancer therapy.

Gambogic acid induces apoptosis and inhibits colorectal tumor growth via mitochondrial pathways

AIM: To investigate the effect of gambogic acid (GA) on apoptosis in the HT-29 human colon cancer cell line.

METHODS: H-29 cells were used for in vitro experiments in this study. Relative cell viability was assessed using MTT assays. Cell apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling and Hoechst 33342 staining, and quantified by flow cytometry. Cellular ultrastructure was observed by transmission electron microscopy. Real-time PCR and Western blot analyses were used to evaluate gene and protein expression levels. For in vivo experiments, BALB/c nude mice received subcutaneous injections of HT-29 cells in the right armpit. When well-established xenografts were palpable with a tumor size of 75 mm³, mice were randomly assigned to a vehicle (negative) control, positive control or GA treatment group (n = 6 each). The animals in the treatment group received one of three dosages of GA (in saline; 5, 10 or 20 mg/kg) via the caudal vein twice weekly, whereas animals in the negative and positive control groups were given equal volumes of 0.9% saline or 10 mg/kg docetaxel, respectively, via the caudal vein once weekly.

RESULTS: The cell viability assay showed that GA inhibited proliferation of HT-29 cells in a dose- and time-dependent manner after treatment with GA (0.00, 0.31, 0.62, 1.25, 2.50, 5.00 or 10.00 μmol/L) for 24, 48 or 72 h. After 48 h, the percentage of apoptotic cells in cells treated with 0.00, 1.25, 2.50 and 5.00 μmol/L GA was 1.4% ± 0.3%, 9.8% ± 1.2%, 25.7% ± 3.3% and 49.3% ± 5.8%, respectively. Ultrastructural analysis of HT-29 cells treated for 48 h with 2.5μmol/L GA revealed apoptotic bodies and condensed and fragmented nuclei. Levels of caspase-8, -9 and -3 mRNAs were significantly increased after treatment with GA (1.25, 2.50 or 5.00 μmol/L) for 48 h (P < 0.05 for all). Protein levels of apoptosis-related factors Fas, FasL, FADD, cytochrome c, and Apaf-1 were increased in GA-treated cells, whereas levels of pro-caspase-8, -9 and -3 were significantly decreased (P < 0.05 for all). Furthermore, GA significantly and dose-dependently inhibited the growth of HT-29 tumors in a mouse xenograft model (P < 0.05).

CONCLUSION: GA inhibits HT-29 proliferation via induction of apoptosis. The anti-cancer effects are likely mediated by death receptor (extrinsic) and mitochondrial (intrinsic) pathways.

Gambogic acid synergistically potentiates cisplatin-induced apoptosis in non-small-cell lung cancer through suppressing NF-κB and MAPK/HO-1 signalling

Background:

Gambogic acid (GA) has been reported to have potent anticancer activity and is authorised to be tested in phase II clinical trials for treatment of non-small-cell lung cancer (NSCLC). The present study aims to investigate whether GA would be synergistic with cisplatin (CDDP) against the NSCLC.

Methods:

1-(4,5-Dimethylthiazol-2-yl)-3,5-diphenylformazan (MTT), combination index (CI) isobologram, western blot, quantitative PCR, flow cytometry, electrophoretic mobility shift assay, xenograft tumour models and terminal deoxynucleotide transferase-mediated dUTP nick-end labelling analysis were used in this study.

Results:

The cell viability results showed that sequential CDDP-GA treatment resulted in a strong synergistic action in A549, NCI-H460, and NCI-H1299 cell lines, whereas the reverse sequence and simultaneous treatments led to a slight synergistic or additive action. Increased sub-G1 phase cells and enhanced PARP cleavage demonstrated that the sequence of CDDP-GA treatment markedly increased apoptosis in comparison with other treatments. Furthermore, the sequential combination could enhance the activation of caspase-3, -8, and 9, increase the expression of Fas and Bax, and decrease the expression of Bcl-2, survivin and X-inhibitor of apoptosis protein (X-IAP) in A549 and NCI-H460 cell lines. In addition, increased apoptosis was correlated with enhanced reactive oxygen species generation. Importantly, it was found that, followed by CDDP treatment, GA could inhibit NF-κB and mitogen-activated protein kinase (MAPK)/heme oxygenase-1 (HO-1) signalling pathways, which have been validated to reduce ROS release and confer CDDP resistance. The roles of NF-κB and MAPK pathways were further confirmed by using specific inhibitors, which significantly increased ROS release and apoptosis induced by the sequential combination of CDDP and GA. Moreover, our results indicated that the combination of CDDP and GA exerted increased antitumour effects on A549 xenograft models through inhibiting NF-κB, HO-1, and subsequently inducing apoptosis.

Conclusion:

Gambogic acid sensitises lung cancer cells to CDDP in vitro and in vivo in NSCLC through inactivation of NF-κB and MAPK/HO-1 signalling pathways, providing a rationale for the combined use of CDDP and GA in lung cancer chemotherapy.