GIP as a potential therapeutic agent?

Glucose-dependent insulinotropic polypeptide (GIP) is released from K-cells in the gut after meal ingestion, and acts in concert with glucagon-like peptide 1 (GLP-1) to augment glucose-stimulated insulin secretion. While derivatives of GLP-1 are under active investigation for the treatment of type 2 diabetes, the case is different for GIP. Indeed, the insulinotropic effect of GIP is almost absent in patients with type 2 diabetes. In addition, the unfavourable pharmacokinetic profile of native GIP obviates its clinical application. Different analogues of GIP exhibiting prolonged stability and enhanced biological potency have been generated in order improve the anti-diabetic properties of GIP. However, glucose-normalisation, as is typically observed during the intravenous administration of GLP-1 in patients with type 2 diabetes, has not yet been achieved with GIP or its derivatives. Since GIP appears to play a role in lipid physiology and elevated levels of GIP have been associated with obesity, antagonising GIP action has been proposed as a therapeutic strategy for obesity. This concept has recently been reinforced by the observation that GIP receptor knock-out mice are protected from high-fat diet-induced obesity. However, eliminating the effect of endogenous GIP may at the same time impair postprandial insulin secretion, thereby severely disturbing glucose homeostasis. Therefore, therapeutic strategies based on either augmenting or antagonising GIP action are far from being established alternatives for the future therapy of type 2 diabetes or obesity.     

Suberoylanilide hydroxamic acid induces apoptosis and sub-G1 arrest of 320 HSR colon cancer cells

Background  

Histone deacetylases and histone acetyl transferases covalently modify histone proteins, consequentially altering chromatin architecture and gene expression.     

Suberoylanilide hydroxamic acid induces ROS-mediated cleavage of HSP90 in leukemia cells

Heat shock protein 90 (HSP90) is a molecular chaperone that supports stability of client proteins. We found that HSP90 was cleaved to 55 kDa protein after treatment with histone deacetylase (HDAC) inhibitors including suberoylanilide hydroxamic acid (SAHA) in several leukemia cell lines. We further analyzed molecular changes induced by SAHA in K562 cells. The SAHA-induced cleavage of HSP90 was blocked by a pan-caspase inhibitor, z-VAD-fmk, implying that the process is dependent on caspase activity. However, the experiments using antagonistic and agonistic Fas antibodies revealed that the cleavage of HSP90 was not dependent on Fas signaling. SAHA induced generation of reactive oxygen species (ROS), and the cleavage of HSP90 was blocked by a ROS scavenger N-acetylcystein (NAC). We also confirmed that hydrogen peroxide (H₂O₂) induced cleavage of HSP90 in a similar manner. Caspase 2, 3, 4, 6, 8, and 10 were activated by treatment with SAHA, and the activities were reduced by the pretreatment of NAC. Treatment of the cells with caspase 10 inhihitor, but not other inhibitors of caspases activated by SAHA, prevented cleavage of HSP90 by SAHA. SAHA-induced ROS generation and HSP90 cleavage were dependent on newly synthesized unknown proteins. Taken together, our results suggest that the cleavage of HSP90 by SAHA is mediated by ROS generation and caspase 10 activation. HSP90 cleavage may provide an additional mechanism involved in anti-cancer effects of HDAC inhibitors.

Electronic supplementary material

The online version of this article (doi:10.1007/s12192-014-0533-4) contains supplementary material, which is available to authorized users.     

Identification of a series of tetrahydroisoquinoline derivatives as potential therapeutic agents for breast cancer

A series of tetrahydroisoquinoline-N-phenylamide derivatives were designed, synthesized, and tested for their relative binding affinities, and antagonistic activities against estrogen receptor (ER). Compound 1f (relative binding affinity, RBA=5) showed higher binding affinity than tamoxifen (RBA=1), a potent ER antagonist and currently being used for breast cancer therapy. Compound 1f also exerted optimal antagonistic activity against ER in reporter and cell proliferation assays. Interestingly, compound 1j, which only has a minor agonistic effect against ER, acted as a progesterone receptor (PR) antagonist and exerted agonistic activity against AP-1 through ER pathway. Our results show that these new compounds can be employed as leading pharmacophore for further development of potent selective ER and/or PR modulators or antagonists.     

Bioactive cationic peptides as potential agents for breast cancer treatment

Breast cancer continues to affect millions of women worldwide, and the number of new cases dramatically increases every year. The physiological causes behind the disease are still not fully understood. One in every 100 cases can occur in men, and although the frequency is lower than among women, men tend to have a worse prognosis of the disease. Various therapeutic alternatives to combat the disease are available. These depend on the type and progress of the disease, and include chemotherapy, radiotherapy, surgery, and cancer immunotherapy. However, there are several well-reported side effects of these treatments that have a significant impact on life quality, and patients either relapse or are refractory to treatment. This makes it necessary to develop new therapeutic strategies. One promising initiative are bioactive peptides, which have emerged in recent years as a family of compounds with an enormous number of clinical applications due to their broad spectrum of activity. They are widely distributed in several organisms as part of their immune system. The antitumoral activity of these peptides lies in a nonspecific mechanism of action associated with their interaction with cancer cell membranes, inducing, through several routes, bilayer destabilization and cell death. This review provides an overview of the literature on the evaluation of cationic peptides as potential agents against breast cancer under different study phases. First, physicochemical characteristics such as the primary structure and charge are presented. Secondly, information about dosage, the experimental model used, and the mechanism of action proposed for the peptides are discussed.     

Suberoylanilide hydroxamic acid (SAHA) at subtoxic concentrations increases the adhesivity of human leukemic cells to fibronectin

Suberoylanilide hydroxamic acid (SAHA) is an inhibitor of histone deacetylases (HDACs) which is being introduced into clinic for the treatment of hematological diseases. We studied the effect of this compound on six human hematopoietic cell lines (JURL‐MK1, K562, CML‐T1, Karpas‐299, HL‐60, and ML‐2) as well as on normal human lymphocytes and on leukemic primary cells. SAHA induced dose‐dependent and cell type‐dependent cell death which displayed apoptotic features (caspase‐3 activation and apoptotic DNA fragmentation) in most cell types including the normal lymphocytes. At subtoxic concentrations (0.5–1 µM), SAHA increased the cell adhesivity to fibronectin (FN) in all leukemia/lymphoma‐derived cell lines but not in normal lymphocytes. This increase was accompanied by an enhanced expression of integrin β1 and paxillin, an essential constituent of focal adhesion complexes, both at the protein and mRNA level. On the other hand, the inhibition of ROCK protein, an important regulator of cytoskeleton structure, had no consistent effect on SAHA‐induced increase in the cell adhesivity. The promotion of cell adhesivity to FN seems to be specific for SAHA as we observed no such effects with other HDAC inhibitors (trichostatin A and sodium butyrate). J. Cell. Biochem. 109: 184–195, 2010. © 2009 Wiley‐Liss, Inc.     

Nek2A contributes to tumorigenic growth and possibly functions as potential therapeutic target for human breast cancer

Nek2A (NIMA-related kinases 2A) has been known as an important centrosome regulatory factor. The aim of this study was to investigate the expression of Nek2A and the role it played in different stages of breast cancer. We detected the expression of Nek2A in both mRNA and protein levels in MCF10 cell lines including MCF-10A, MCF-10DCIS.com, MCF-10CA1a and in human breast samples which contained normal breast tissue (NBT), breast ductal carcinoma in situ (DCIS), and invasive ductal carcinoma (IDC). Our study revealed that the mRNA and protein expression of Nek2A were significantly up-regulated in MCF-10DCIS.com and MCF-10CA1a cell lines as well as in human primary breast cancer tissue (DCIS and IDC). Our study also presented a correlation between Nek2A mRNA expression and some clinic pathological factors. We found that Nek2A mRNA expression was associated with molecular subtypes, ER, PR and Ki-67 immunoreactivity (P<0.05) in DCIS and associated with histological grade, lymph node metastasis, molecular subtypes, c-erbB-2, and Ki-67 expression (P<0.05) in IDC. In addition, we observed that ectopic expression of Nek2A in "normal" immortalized MCF-10A breast epithelial cell resulted in increased Nek2A which lead to abnormal centrosomes. Furthermore, knockdown of Nek2A in MCF-10DCIS.com could remarkably inhibit cell proliferation and induce cell cycle arrest in MCF-10DCIS.com cell line. These data suggested that Nek2A might bear a close relationship with development and progression of breast carcinoma, and highlighted its role as a novel potential biomarker for diagnosis and a possible therapeutic target for human breast cancer especially for DCIS.     

Estradiol as an anti-aromatase agent in human breast cancer cells

Estradiol (E(2)) is an important risk factor in the development and progression of breast cancer. However, a "direct effect" of E(2) in breast cancerization has not yet been demonstrated. The estrogen receptor complex can mediate the activation of oncogens, proto-oncogens, nuclear proteins and other target genes that can be involved in the transformation of normal to cancerous cells. Breast cancer cells possess all the enzymes (sulfatase, aromatase, 17beta-hydroxysteroid dehydrogenase (17beta-HSD)) necessary for the local bioformation of E(2). In the last years, many studies have shown that treatment of breast cancer patients using anti-aromatase agents has beneficial therapeutic effects. The aromatase activity is very low in most breast cancer cells but was significantly increased in a hormone-dependent breast cancer cell line: the MCF-7aro, using the aromatase cDNA transfection and G-418 (neomycin) selection. In the present study, we explore the effect of E(2) on the aromatase activity of this cell line. The MCF-7aro cell line was a gift from Dr. S. Chen (Beckman Research Institute, Duarte, U.S.A.). For experiments the cells were stripped of endogenous steroids and incubated with physiological concentrations of [(3)H]-testosterone (5 x 10(-9)mol/l) alone or in the presence of E(2) (5 x 10(-5), 5 x 10(-7) and 5 x 10(-9)mol/l) for 24h at 37 degrees C. The cellular radioactivity uptake was determined in the ethanolic supernatant and the DNA content in the remaining pellet. [(3)H]-E(2), [(3)H]-estrone ([(3)H]-E(1)) and [(3)H]-testosterone were characterized by thin layer chromatography and quantified using the corresponding standard. It was observed that [(3)H]-testosterone is converted mainly into [(3)H]-E(2) and not to E(1), which suggests very low or absence of oxidative 17beta-HSD (type 2) activity in these experimental conditions. The aromatase activity, corresponding to the conversion of [(3)H]-testosterone to [(3)H]-E(2) after 24h, is relatively high, since the concentration of E(2) was 2.74+/-0.11pmol/mg DNA in the non-treated cells. E(2) inhibits this conversion by 77, 57 and 21%, respectively, at the concentrations of 5 x 10(-5), 5 x 10(-7) and 5 x 10(-9)mol. In previous studies, it was demonstrated that E(2) exerts a potent anti-sulfatase activity in the MCF-7 and T-47D breast cancer cells. The present data show that E(2) can also block the aromatase activity. The dual inhibition of the aromatase and sulfatase activities, two crucial enzymes for the biosynthesis of E(2) by E(2) itself in breast cancer add interesting and attractive information for the use of estrogen therapeutic treatments.     

Vesicular trafficking–related proteins as the potential therapeutic target for breast cancer

Protoplasma - Vesicular trafficking between endoplasmic reticulum and Golgi plays a major role in the growth and proliferation of breast cancer cells. Various proteins regulate this ER-Golgi...     

Synthesis and biological evaluation of 2,3,4-triarylbenzopyran derivatives as SERM and therapeutic agent for breast cancer

A novel class of 2,3,4-triarylbenzopyrans has been synthesized and were evaluated for their selective estrogen receptor modulation activity and as a therapeutic agent for breast cancer. Among the compounds synthesized, compounds 11a and 12c exhibited 73.91% and 69.24% inhibition as estrogen antagonistic activity, respectively. Compound 12a showed the lowest IC₅₀ at 6.97 μM against MCF-7 and 11f showed the lowest IC₅₀ value of 5.6 μM against MDA-MB-231 cell line in spite of their low receptor binding affinity implicating these compounds probably act through ER independent mechanism.     

L-Canavanine as a radiosensitization agent for human pancreatic cancer cells

This study evaluated the in vitro effect of L-canavanine on cell cycle progression in the two human pancreatic cancer cells lines PANC-1 and MIA PaCa-2. After 72 h of exposure to L-canavanine, the percentage of cells in the radiosensitive G₂/M phase of the cell cycle increased 6-fold in PANC-1 cells and 4-fold in MIA PaCa-2 cells, when compared to untreated cells. The capacity of L-canavanine to redistribute cells into the G₂/M phase of the cell cycle was both concentration- and time-dependent. Since many drugs that cause cells to accumulate in the G₂/M phase of the cell cycle are effective radiosensitization agents, the potential of L-canavanine to synergistically enhance the effects of ionizing radiation also was evaluated. The interaction between these treatment modalities was quantified using the median-effect equation and combination index analysis. L-Canavanine was found to be synergistic with radiation when either PANC-1 or MIA PaCa-2 cells were exposed to L-canavanine for 72 h prior to irradiation. These results suggest that L-canavanine in combination with radiation may have clinical potential in the treatment of pancreatic cancer.     

RAD51 as a potential biomarker and therapeutic target for pancreatic cancer

Chemotherapy is a very important therapeutic strategy for cancer treatment. The failure of conventional and molecularly targeted chemotherapeutic regimes for the treatment of pancreatic cancer highlights a desperate need for novel therapeutic interventions. Chemotherapy often fails to eliminate all tumor cells because of intrinsic or acquired drug resistance, which is the most common cause of tumor recurrence. Overexpression of RAD51 protein, a key player in DNA repair/recombination has been observed in many cancer cells and its hyperexpression is implicated in drug resistance. Recent studies suggest that RAD51 overexpression contributes to the development, progression and drug resistance of pancreatic cancer cells. Here we provide a brief overview of the available pieces of evidence in support of the role of RAD51 in pancreatic tumorigenesis and drug resistance, and hypothesize that RAD51 could serve as a potential biomarker for diagnosis of pancreatic cancer. We discuss the possible involvement of RAD51 in the drug resistance associated with epithelial to mesenchymal transition and with cancer stem cells. Finally, we speculate that targeting RAD51 in pancreatic cancer cells may be a novel approach for the treatment of pancreatic cancer.     

Transcriptome analysis reveals GPNMB as a potential therapeutic target for gastric cancer

Gastric cancer has the fifth highest incidence of disease and is the third leading cause of cancer-associated mortality in the world. The etiology of gastric cancer is complex and needs to be fully elucidated. Thus, it is necessary to explore potential pathogenic genes and pathways that contribute to gastric cancer. Gene expression profiles of the GSE33335 and GSE54129 datasets were downloaded from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) were compared and identified using R software. The DEGs were then subjected to gene set enrichment analysis and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. Survival analyses based on The Cancer Genome Atlas database were used to further screen the essential DEGs. A knockdown assay was performed to determine the function of the candidate gene in gastric cancer. Finally, the association between the candidate gene and immune-related genes was investigated. We found that GPNMB serves as an essential gene, with a high expression level, and predicts a worse outcome of gastric cancer. Knockdown of GPNMB inhibited gastric cancer cell proliferation and migration. In addition, GPNMB may augment the immunosuppressive ability of gastric cancer by recruiting immunosuppressive cells and promoting immune cell exhaustion through PI3K/AKT/CCL4 signaling axis. Collectively, these data suggest that GPNMB acts as an important positive mediator of tumor progression in gastric cancer, and GPNMB could exert multimodality modulation of gastric cancer-mediated immune suppression.     

Pre-clinical evaluation of cinobufotalin as a potential anti-lung cancer agent

Lung cancer is a major cause of cancer-related mortality in the United States and around the world. Due to the pre-existing or acquired chemo-resistance, the current standard chemotherapy regimens only show moderate activity against lung cancer. In the current study, we explored the potential anti-lung cancer activity of cinobufotalin in vivo and in vitro, and studied the underlying mechanisms. We demonstrated that cinobufotalin displayed considerable cytotoxicity against lung cancer cells (A549, H460 and HTB-58 lines) without inducing significant cell apoptosis. Our data suggest that mitochondrial protein cyclophilin D (Cyp-D)-dependent mitochondrial permeability transition pore (mPTP) opening mediates cinobufotalin-induced non-apoptotic death of lung cancer cells. The Cyp-D inhibitor cyclosporine A (CsA), the mPTP blocker sanglifehrin A (SfA), and Cyp-D shRNA-silencing significantly inhibited cinobufotalin-induced mitochondrial membrane potential (MMP) reduction and A549 cell death (but not apoptosis). Using a mice xenograft model, we found that cinobufotalin inhibited A549 lung cancer cell growth in vivo. Thus, cinobufotalin mainly induces Cyp-D-dependent non-apoptotic death in cultured lung cancer cells. The results of this study suggest that cinobufotalin might be further investigated as a novel anti-lung cancer agent.