18β-Glycyrrhetinic acid potentiates apoptotic effect of trichostatin A on human epithelial ovarian carcinoma cell lines

Glycyrrhizic acid enhances the anticancer activity of cisplatin in the human ovarian cancer cell line

This study aimed to investigate the effects of glycyrrhizic acid (GL) on the anticancer activity of cisplatin in A2780 ovarian cancer cells. Cultured A2780 cells were treated with different concentrations of GL and cisplatin individually and in combination. The MTT assay, flow cytometry, wound-healing, and clonogenic assay, were used to determine cell viability, apoptosis, migration, and colony formation, respectively. The effects on superoxide dismutase (SOD) activity were also evaluated. QPCR was used to study the effects of individual and combined treatments with GL and cisplatin on the expression levels of migration genes (MMP2 and MMP9), and some apoptosis pathway genes (caspase-3, -8, -9, and BCL2). A synergistic effect was observed between GL and cisplatin (CI < 1). Combination therapy was significantly more effective in reducing cell viability, suppressing migration and colony formation, inducing apoptosis, and altering gene expression compared to single therapies. GL significantly increased SOD activity. The relative expression of caspase -3, -8, and - 9 increased significantly, and the expression levels of MMP2 and MMP9 decreased significantly in the treated cells. Our results indicate that GL enhances the anticancer activity of cisplatin in the A2780 cell line. Therefore, the combination of GL and cisplatin can be proposed as a promising therapeutic strategy for ovarian cancer.

Oxidative stress in pituitary neuroendocrine tumors: Affecting the tumor microenvironment and becoming a new target for pituitary neuroendocrine tumor therapy

Pituitary adenomas (PAs), or pituitary neuroendocrine tumors (PitNETs), are commonly found in the anterior pituitary gland. Although the majority of PitNETs are benign and stable, several tumors have malignant characteristics. The tumor microenvironment (TME) plays an important role in the process of tumorigenesis and is composed of several types of cells. Various cells in the TME are significantly affected by oxidative stress. It has been reported that immunotherapeutic strategies have good effects in several cancers. However, the clinical potential of immunotherapies in PitNETs has not yet been fully discussed. Oxidative stress can regulate PitNET cells and immune cells in the TME, thus affecting the immune status of the TME of PitNETs. Therefore, modulation of oxidative stress-regulated immune cells using a combination of several agents and the immune system to suppress PitNETs is a promising therapeutic direction. In this review, we systematically analyzed the oxidative stress process within PitNET cells and various immune cells to elucidate the potential value of immunotherapy.

Pharmacological Properties of Trichostatin A, Focusing on the Anticancer Potential: A Comprehensive Review

Trichostatin A (TSA), a natural derivative of dienohydroxamic acid derived from a fungal metabolite, exhibits various biological activities. It exerts antidiabetic activity and reverses high glucose levels caused by the downregulation of brain-derived neurotrophic factor (BDNF) expression in Schwann cells, anti-inflammatory activity by suppressing the expression of various cytokines, and significant antioxidant activity by suppressing oxidative stress through multiple mechanisms. Most importantly, TSA exhibits potent inhibitory activity against different types of cancer through different pathways. The anticancer activity of TSA appeared in many in vitro and in vivo investigations that involved various cell lines and animal models. Indeed, TSA exhibits anticancer properties alone or in combination with other drugs used in chemotherapy. It induces sensitivity of some human cancers toward chemotherapeutical drugs. TSA also exhibits its action on epigenetic modulators involved in cell transformation, and therefore it is considered an epidrug candidate for cancer therapy. Accordingly, this work presents a comprehensive review of the most recent developments in utilizing this natural compound for the prevention, management, and treatment of various diseases, including cancer, along with the multiple mechanisms of action. In addition, this review summarizes the most recent and relevant literature that deals with the use of TSA as a therapeutic agent against various diseases, emphasizing its anticancer potential and the anticancer molecular mechanisms. Moreover, TSA has not been involved in toxicological effects on normal cells. Furthermore, this work highlights the potential utilization of TSA as a complementary or alternative medicine for preventing and treating cancer, alone or in combination with other anticancer drugs.

Toll-Like Receptors (TLRs) and their potential therapeutic applications in diabetic neuropathy

One of the most common diabetic microvascular complications is diabetic neuropathy (DN). Immune cell infiltration in the peripheral nerve system (PNS), myelin loss, Schwann cell death, and axonal damage are all hallmarks of DN, which is currently believed to be a chronic inflammatory disease. Toll-like receptors (TLRs) are found in various types of nervous system cells, including Schwann cells, microglia, oligodendrocytes, astrocytes, and neurons. Proinflammatory mediators released at the end of TLR signal transduction can trigger an inflammatory response involving the nervous system. Studies on the association between TLRs and DN began as early as 2004. Since then, several studies have been conducted to assess the involvement of TLRs in the pathogenesis of DN. The focus of this review is to give a complete summary of the researches that have been done in this context, as well as an overview of the role of TLRs and their therapeutic applications in DN.

Advances in Pharmacological Activities and Mechanisms of Glycyrrhizic Acid

Licorice (Glycyrrhiza glabra L.) is widely regarded as an important medicinal plant and has been used for centuries in traditional medicine because of its therapeutic properties. Studies have shown that metabolites isolated from licorice have many pharmacological activities, such as antiinflammatory, anti-viral, participation in immune regulation, anti-tumor and other activities. This article gives an overview of the pharmacological activities and mechanisms of licorice metabolites and the adverse reactions that need attention. This review helps to further investigate the possibility of licorice as a potential drug for various diseases. It is hoped that this review can provide a relevant theoretical basis for relevant scholars' research and their own learning.

Carbenoxolone and 18β-glycyrrhetinic acid inhibit inositol 1,4,5-trisphosphate-mediated endothelial cell calcium signalling and depolarise mitochondria

BACKGROUND AND PURPOSE

Coordinated endothelial control of cardiovascular function is proposed to occur by endothelial cell communication via gap junctions and connexins. To study intercellular communication, the pharmacological agents carbenoxolone (CBX) and 18β-glycyrrhetinic acid (18βGA) are used widely as connexin inhibitors and gap junction blockers.

EXPERIMENTAL APPROACH

We investigated the effects of CBX and 18βGA on intercellular Ca²⁺ waves, evoked by inositol 1,4,5-trisphosphate (IP₃ ) in the endothelium of intact mesenteric resistance arteries.

KEY RESULTS

Acetycholine-evoked IP₃ -mediated Ca²⁺ release and propagated waves were inhibited by CBX (100 μM) and 18βGA (40 μM). Unexpectedly, the Ca²⁺ signals were inhibited uniformly in all cells, suggesting that CBX and 18βGA reduced Ca²⁺ release. Localised photolysis of caged IP₃ (cIP₃ ) was used to provide precise spatiotemporal control of site of cell activation. Local cIP₃ photolysis generated reproducible Ca²⁺ increases and Ca²⁺ waves that propagated across cells distant to the photolysis site. CBX and 18βGA each blocked Ca²⁺ waves in a time-dependent manner by inhibiting the initiating IP₃ -evoked Ca²⁺ release event rather than block of gap junctions. This effect was reversed on drug washout and was unaffected by small or intermediate K⁺ -channel blockers. Furthermore, CBX and 18βGA each rapidly and reversibly collapsed the mitochondrial membrane potential.

CONCLUSION AND IMPLICATIONS

CBX and 18βGA inhibit IP₃ -mediated Ca²⁺ release and depolarise the mitochondrial membrane potential. These results suggest that CBX and 18βGA may block cell-cell communication by acting at sites that are unrelated to gap junctions.

Design, Synthesis, Antibacterial Evaluation, and Induced Apoptotic Behaviors of Epimeric and Chiral 18β-Glycyrrhetinic Acid Ester Derivatives with an Isopropanolamine Bridge against Phytopathogens

Because only a handful of agrochemicals can manage bacterial infections, the discovery and development of innovative, inexpensive, and high-efficiency antibacterial agents targeting these infections are challenging. Herein, a series of novel epimeric and chiral 18β-glycyrrhetinic acid (GA) ester derivatives with various tertiary amine pendants were designed, synthesized, and screened for pharmacological activity. Results showed that some of the title compounds were conferred with significantly enhanced antibacterial activity toward phytopathogens Xanthomonas oryzae pv oryzae (A₂, B₁-B₃, and C₁, EC₅₀ values within 3.81-4.82 μg/mL) and Xanthomonas axonopodis pv citri (B₁, EC₅₀ = 3.18 μg/mL; B₂, EC₅₀ = 2.76 μg/mL). These activities are superior to those of GA (EC₅₀ > 400 μg/mL), thiodiazole copper, and bismerthiazol. Pharmacophore studies revealed that the synergistic combination of GA skeleton and tertiary amine scaffolds contributed to the biological actions. In vivo experiments displayed their promising applications in controlling bacterial infections. Antibacterial mechanism studies revealed that the title compounds could trigger apoptosis in the tested pathogens, evident by bacteria morphological changes observed in scanning electron microscopy images. This outcome should motivate the development of various apoptosis inducers against plant bacterial diseases by a novel mode of action compared to that of existing agricultural chemicals.

Exploring New Structural Features of the 18β-Glycyrrhetinic Acid Scaffold for the Inhibition of Anaplastic Lymphoma Kinase

Novel 18β-glycyrrhetinic acid derivatives possessing a carbamate moiety and structurally similar ester derivatives were developed and evaluated for their efficacy as antitumor inhibitors. In the cellular assays, most of the N-substituted carbamate derivatives at the C3-position exhibited potent activities. The results of SAR investigation revealed that the introduction of the morpholine group at the C30-COOH led to a significant loss of the inhibitory potency. Among the ester derivatives, the ester group at C3-position also determined a noticeable reduction in the efficacy. Compound 3j exhibited the most prominent antiproliferative activity against six human cancer cells (A549, HT29, HepG2, MCF-7, PC-3, and Karpas299). Furthermore, compound 3j exerted a moderate inhibiting effect on the ALK. The results of molecular docking analyses suggested that it could bind well to the active site of the receptor ALK, which was consistent with the biological data. These results might inspire further structural optimization of 18β-glycyrrhetinic acid aiming at the development of potent antitumor agents. The structures 4d, 4g, 4h, 4j, and 4n were studied by X-ray crystallographic analyses.

Evaluation of the Cytotoxic and Apoptogenic Effects of Glabridin and Its Effect on Cytotoxicity and Apoptosis Induced by Doxorubicin Toward Cancerous Cells

Purposes: In the present study, we tried for the first time to examine the anti-proliferative and anti-apoptogenic effect of Glabridin (Glab) toward three groups of cancer cells (SKNMC, H1299, and A2780). Furthermore, the possibility of co-administration of Glab with doxorubicin (DOX) to these cells was also examined to find out whether Glab can potentiate the cytotoxic effect of this chemotherapy agent.

Methods: Different cellular assays (MTT, caspase-3 activity, MMP, RT-PCR analysis) were carried out on the cancer cells treated with Glab.

Results: Cellular toxicity assay revealed that Glab can potentially reduce the viability of these cells with IC50 concentrations up to 10, 12, and 38 μM toward A2780, SKNMC, and H1299 cell lines, respectively. The results of MMP and caspase-3 activity assays, in association with the results corresponding to the BAX and Bcl-2 gene expressions, altogether revealed that Glab can exert apoptogenic effect on these cells. The intrinsic mitochondrial pathway was found to be the main mechanism, in which Glab induced apoptosis toward H1299 cells and SKNMC cells, while the apoptosis mechanism for A2780 cells could be probably through extrinsic pathway. Glab also potentiated the cytotoxic effect of DOX and its accumulation in H1299 cell line.

Conclusion: The results of this study revealed the promising cytotoxic role of Glab on different carcinoma cells. These data also suggested that co-chemotherapy method using Glab could be effective for treatment of cancer, but further in-vivo and clinical studies are still needed to assure these results.

The MAPK Pathway-Based Drug Therapeutic Targets in Pituitary Adenomas

Mitogen-activated protein kinases (MAPKs) include ERK, p38, and JNK MAPK subfamilies, which are crucial regulators of cellular physiology, cell pathology, and many diseases including cancers. For the MAPK signaling system in pituitary adenomas (PAs), the activation of ERK signaling is generally thought to promote cell proliferation and growth; whereas the activations of p38 and JNK signaling are generally thought to promote cell apoptosis. The role of MAPK in treatment of PAs is demonstrated through the effects of currently used medications such as somatostatin analogs such as SOM230 and OCT, dopamine agonists such as cabergoline and bromocriptine, and retinoic acid which inhibit the MAPK pathway. Further, there are potential novel therapies based on putative molecular targets of the MAPK pathway, including 18beta-glycyrrhetinic acid (GA), dopamine-somatostatin chimeric compound (BIM-23A760), ursolic acid (UA), fulvestrant, Raf kinase inhibitory protein (RKIP), epidermal growth factor pathway substrate number 8 (Eps8), transmembrane protein with EGF-like and two follistatin-like domains (TMEFF2), cold inducible RNA-binding protein (CIRP), miR-16, and mammaliansterile-20-like kinase (MST4). The combined use of ERK inhibitor (e.g., SOM230, OCT, or dopamine) plus p38 activator (e.g., cabergoline, bromocriptine, and fulvestrant) and/or JNK activator (e.g., UA), or the development of single drug (e.g., BIM-23A760) to target both ERK and p38 or JNK pathways, might produce better anti-tumor effects on PAs. This article reviews the advances in understanding the role of MAPK signaling in pituitary tumorigenesis, and the MAPK pathway-based potential therapeutic drugs for PAs.

Synthesis and Antiproliferative Activity of Novel Heterocyclic Glycyrrhetinic Acid Derivatives

A new series of glycyrrhetinic acid derivatives has been synthesized via the introduction of different heterocyclic rings conjugated with an α,β-unsaturated ketone in its ring A. These new compounds were screened for their antiproliferative activity in a panel of nine human cancer cell lines. Compound 10 was the most active derivative, with an IC₅₀ of 1.1 µM on Jurkat cells, which is 96-fold more potent than that of glycyrrhetinic acid, and was 4-fold more selective toward that cancer cell line. Further biological studies performed in Jurkat cells showed that compound 10 is a potent inducer of apoptosis that activates both the intrinsic and extrinsic pathways.

Pharmacological Activities and Phytochemical Constituents

Glycyrrhiza glabra is one of the most popular medicinal plants and it has been used in traditional herbal remedy since ancient times (Blumenthal et al. in Herbal medicine: expanded commission E monographs. Integrative Medicine Communications, Newton, 2000; Parvaiz et al. in Global J Pharmocol 8(1):8–13, 2014; Altay et al. in J Plant Res 129(6):1021–1032, 2016). Many experimental, pharmacological and clinical studies show that liquorice has antimicrobial, antibacterial, antiviral, antifungal, antihepatotoxic, antioxidant, antiulcer, anti-hemorrhoid antihyperglycemic, antidiuretic, antinephritic, anticarcinogenic, antimutagenic, anticytotoxic, anti-inflammatory, and blood stopper activity.

Possible pharmacotherapy for nifedipine-induced gingival overgrowth: 18α-glycyrrhetinic acid inhibits human gingival fibroblast growth

BACKGROUND AND PURPOSE

This investigation aimed to establish the basis of a pharmacotherapy for nifedipine-induced gingival overgrowth. Gingival overgrowth has been attributed to the enhanced growth of gingival fibroblasts. In this study, we investigated the effects of 18-α-glycyrrhetinic acid (18α-GA) on growth, the cell cycle, and apoptosis and on the regulators of these processes in gingival fibroblasts isolated from patients who presented with nifedipine-induced gingival overgrowth.

EXPERIMENTAL APPROACH

Gingival fibroblasts were cultured in medium containing 1% FBS with/without 10 μM 18α-GA for 24 or 48 h, and the cell number, cell cycle phase distribution, relative DNA content, apoptotic cell number and morphological characteristics of the cells undergoing apoptosis were measured together with the levels of proteins that regulate these processes and the level of caspase activity.

KEY RESULTS

18α-GA significantly decreased cell numbers and significantly increased the percentage of cells in the sub-G1 and G0 /G1 phases of the cell cycle and the number of apoptotic cells. Nuclear condensation and fragmentation of cells into small apoptotic bodies appeared in the fibroblasts treated with 18α-GA. In addition, 18α-GA significantly decreased the protein levels of cyclins A and D1, CDKs 2 and 6, phosphorylated Rb (ser(780) and ser(807/811)), Bcl-xL and Bcl-2 and increased the protein levels of p27, cytosolic cytochrome c, pro-caspase-3, and cleaved caspase-3 and the activities of caspases 3 and 9.

CONCLUSIONS AND IMPLICATIONS

18α-GA inhibited gingival fibroblast growth by suppressing the G1 /S phase transition and inducing apoptosis. In conclusion, 18α-GA may be used as a pharmacotherapy for nifedipine-induced gingival overgrowth.

Glycyrrhizin, silymarin, and ursodeoxycholic acid regulate a common hepatoprotective pathway in HepG2 cells

BACKGROUND

Glycyrrhizin, silymarin, and ursodeoxycholic acid are widely used hepatoprotectants for the treatment of liver disorders, such as hepatitis C virus infection, primary biliary cirrhosis, and hepatocellular carcinoma.

PURPOSE

The gene expression profiles of HepG2 cells responsive to glycyrrhizin, silymarin, and ursodeoxycholic acid were analyzed in this study.

METHODS

HepG2 cells were treated with 25 µM hepatoprotectants for 24 h. Gene expression profiles of hepatoprotectants-treated cells were analyzed by oligonucleotide microarray in triplicates. Nuclear factor-κB (NF-κB) activities were assessed by luciferase assay.

RESULTS

Among a total of 30,968 genes, 252 genes were commonly regulated by glycyrrhizin, silymarin, and ursodeoxycholic acid. These compounds affected the expression of genes relevant various biological pathways, such as neurotransmission, and glucose and lipid metabolism. Genes involved in hepatocarcinogenesis, apoptosis, and anti-oxidative pathways were differentially regulated by all compounds. Moreover, interaction networks showed that NF-κB might play a central role in the regulation of gene expression. Further analysis revealed that these hepatoprotectants inhibited NF-κB activities in a dose-dependent manner.

CONCLUSION

Our data suggested that glycyrrhizin, silymarin, and ursodeoxycholic acid regulated the expression of genes relevant to apoptosis and oxidative stress in HepG2 cells. Moreover, the regulation by these hepatoprotectants might be relevant to the suppression of NF-κB activities.

Potential drug interactions associated with glycyrrhizin and glycyrrhetinic acid

Glycyrrhizin (GZ), the main active component of licorice, is a widely used therapeutic in the clinic. Depending on the disease, the treatment may involve a long course of high dose GZ. Another component of licorice, glycyrrhetinic acid (GA), is the main active metabolite of GZ and is thought to be responsible for the majority of the pharmacological properties of GZ. Therefore, GZ and GA are both used for therapeutic purposes. In addition, GZ and GA are also widely used to sweeten and flavor foods. Due to this widespread, multifaceted use of these substances, potential drug interactions with GZ and GA have recently gained attention. Along these lines, this review covers the known effects of GZ and GA on drug-metabolizing enzymes and efflux transporters. We conclude that both GZ and GA may have an effect on the activity of CYPs. For example, GZ may induce CYP3A activity through activation of PXR. Also, GZ and GA may affect glucuronidation in rats and humans. Furthermore, 18β-GA is a potent inhibitor of P-gp, while GZ and GA are inhibitors of MRP1, MRP2 and BCRP. The pharmacokinetics and pharmacodynamics of many medications may be altered when used concurrently with GZ or GA, which is also covered in this review. Overall, GZ, GA or related products should be taken with caution when taken with additional medications due to the possible drug interactions.

Glycyrrhetinic acid induces G1‑phase cell cycle arrest in human non‑small cell lung cancer cells through endoplasmic reticulum stress pathway

Glycyrrhetinic acid (GA) is a natural compound extracted from liquorice, which is often used in traditional Chinese medicine. The purpose of the present study was to investigate the antitumor effect of GA in human non-small cell lung cancer (NSCLC), and its underlying mechanisms in vitro. We have shown that GA suppressed the proliferation of A549 and NCI-H460 cells. Flow cytometric analysis showed that GA arrested cell cycle in G0/G1 phase without inducing apoptosis. Western blot analysis indicated that GA mediated G1-phase cell cycle arrest by upregulation of cyclin-dependent kinase inhibitors (CKIs) (p18, p16, p27 and p21) and inhibition of cyclins (cyclin-D1, -D3 and -E) and cyclin-dependent kinases (CDKs) (CDK4, 6 and 2). GA also maintained pRb phosphorylation status, and inhibited E2F transcription factor 1 (E2F-1) in both cell lines. GA upregulated the unfolded proteins, Bip, PERK and ERP72. Accumulation of unfolded proteins in the endoplasmic reticulum (ER) triggered the unfolded protein response (UPR), which could be the mechanism by which GA inhibited cell proliferation in NSCLC cells. GA then coordinated the induction of ER chaperones, which decreased protein synthesis and induced cell cycle arrest in the G1 phase. This study provides experimental evidence to support the development of GA as a chemotherapeutic agent for NSCLC.

18β-Glycyrrhetinic acid suppresses cell proliferation through inhibiting thromboxane synthase in non-small cell lung cancer

18β-glycyrrhetinic acid (18β-GA) is a bioactive component of licorice. The anti-cancer activity of 18β-GA has been studied in many cancer types, whereas its effects in lung cancer remain largely unknown. We first showed that 18β-GA effectively suppressed cell proliferation and inhibited expression as well as activity of thromboxane synthase (TxAS) in non-small cell lung cancer (NSCLC) cells A549 and NCI-H460. In addition, the administration of 18β-GA did not have any additional inhibitory effect on the decrease of cell proliferation induced by transfection with TxAS small interference RNA (siRNA). Moreover, 18β-GA failed to inhibit cell proliferation in the immortalized human bronchial epithelial cells 16HBE-T and another NSCLC cell line NCI-H23, both of which expressed minimal level of TxAS as compared to A549 and NCI-H460. However, 18β-GA abolished the enhancement of cell proliferation induced by transfection of NCI-H23 with pCMV6-TxAS plasmid. Further study found that the activation of both extracellular signal-regulated kinase (ERK)1/2 and cyclic adenosine monophosphate response element binding protein (CREB) induced by TxAS cDNA transfection could be totally blocked by 18β-GA. Altogether, we have delineated that, through inhibiting TxAS and its initiated ERK/CREB signaling, 18β-GA suppresses NSCLC cell proliferation. Our study has highlighted the significance of 18β-GA with respect to prevention and treatment of NSCLC.

Bioactivity and potential health benefits of licorice

Licorice is an herbal plant named for its unique sweet flavor. It is widely used in the food and tobacco industries as a sweetener. Licorice is also used in traditional Chinese medicine (TCM) and complementary medicine. Because the use of licorice has long been a part of TCM, the details of its therapeutic applications have been thoroughly established. In modern science, licorice is of interest because of its broad range of applications. Extracts of and compounds isolated from licorice have been well studied and biologically characterized. In this review, we discuss the nutraceutical and functional activities of licorice as well as those of the extracts of and the isolated compounds from licorice, including agents with anti-inflammatory activity, cell-protective abilities, and chemopreventive effects. The side effects of licorice are also enumerated. A comparison of the activities of licorice described by modern science and TCM is also presented, revealing the correspondence of certain characteristics.

18beta-glycyrrhetinic acid induces apoptosis in pituitary adenoma cells via ROS/MAPKs-mediated pathway

The purpose of the present study was to evaluate the anti-tumor effects of 18beta-glycyrrhetinic acid (GA), a natural compound extracted from liquorice, against pituitary adenoma and its underlying mechanisms in cultured cells and mouse model of xenografted tumor. GA induced cellular damage in rat pituitary adenoma-derived MMQ and GH3 cells, manifested as reduced cell viability, increased lactate dehydrogenase release, elevated intracellular reactive oxygen species (ROS) and Ca(2+) concentration. GA also caused G0/G1 phase arrest, increased apoptosis rate and increased mitochondrial membrane permeabilization by suppressing the mitochondrial membrane potential and down-regulating a ratio of B cell lymphoma 2 (Bcl-2) and Bax. GA activated calcium/calmodulin-dependent protein kinase II (CaMKII), c-Jun N-terminal kinase (JNK) and P38; but these activating effects were attenuated by pretreatment with N-acetyl-L-cysteine, a ROS inhibitor. Pretreatment with KN93, a CaMKII inhibitor, also abolished the GA activation of JNK and P38. GA remarkably inhibited growth of pituitary adenoma grafted on nude mice. These results suggest that the anti-pituitary adenoma effect of GA is associated with its apoptotic actions by activating mitochondria-mediated ROS/mitogen-activated protein kinase pathways in particular CaMKII that may serve a linkage between ROS accumulation and the activation of JNK and P38. This study provides experimental evidence in the support of further developing GA as a chemotherapeutic agent for pituitary adenoma.