Apoptosis-modulating drugs for improved cancer therapy

Naringin Induces ROS-Stimulated G1 Cell-Cycle Arrest and Apoptosis in Nasopharyngeal Carcinoma Cells

Naringin, a bioflavonoid compound from grapefruit or citrus, exerts anticancer activities on cervical, thyroid, colon, brain, liver, lung, thyroid, and breast cancers. The present investigation addressed exploring the anticancer effects of naringin on nasopharyngeal carcinoma (NPC) cells. Naringin exhibits a cytotoxic effect on NPC-TW 039 and NPC-TW 076 cells with IC50 372/328 and 394/307 μM for 24 or 48 h, respectively, while causing little toxicity toward normal gingival epithelial (SG) cells (>500/500 μM). We established that naringin triggered G1 arrest is achieved by suppressing cyclin D1, cyclin A, and CDK2, and upregulating p21 protein in NPC cells. Exposure of NPC cells to naringin caused a series of events leading to apoptosis including morphology change (cell shrinkage and membrane blebbing) and chromatin condensation. Annexin V and PI staining indicated that naringin treatment promotes necrosis and late apoptosis in NPC cells. DiOC6 staining showed a decline in the mitochondrial membrane potential by naringin treatment, which was followed with cytochrome c release, Apaf-1/caspase-9/-3 activation, PARP cleavage, and EndoG expression in NPC cells. Naringin upregulated proapoptotic Bax and decreased antiapoptotic Bcl-xL expression, and dysregulated Bax/Bcl-xL ratio in NPC cells. Notably, naringin enhanced death receptor-related t-Bid expression. Furthermore, an increased Ca2+ release by naringin treatment which instigated endoplasmic reticulum stress-associated apoptosis through increased IRE1, ATF-6, GRP78, GADD153, and caspase-12 expression in NPC cells. In addition, naringin triggers ROS production, and inhibition of naringin-induced ROS generation by antioxidant N-acetylcysteine resulted in the prevention of G1 arrest and apoptosis in NPC cells. Naringin-induced ROS-mediated G1 arrest and mitochondrial-, death receptor-, and endoplasmic reticulum stress-mediated apoptosis may be a promising strategy for treating NPC.

Fundamental insights and molecular interactions in pancreatic cancer: Pathways to therapeutic approaches

The gastrointestinal tract can be affected by a number of diseases that pancreatic cancer (PC) is a malignant manifestation of them. The prognosis of PC patients is unfavorable and because of their diagnosis at advanced stage, the treatment of this tumor is problematic. Owing to low survival rate, there is much interest towards understanding the molecular profile of PC in an attempt in developing more effective therapeutics. The conventional therapeutics for PC include surgery, chemotherapy and radiotherapy as well as emerging immunotherapy. However, PC is still incurable and more effort should be performed. The molecular landscape of PC is an underlying factor involved in increase in progression of tumor cells. In the presence review, the newest advances in understanding the molecular and biological events in PC are discussed. The dysregulation of molecular pathways including AMPK, MAPK, STAT3, Wnt/β-catenin and non-coding RNA transcripts has been suggested as a factor in development of tumorigenesis in PC. Moreover, cell death mechanisms such as apoptosis, autophagy, ferroptosis and necroptosis demonstrate abnormal levels. The EMT and glycolysis in PC cells enhance to ensure their metastasis and proliferation. Furthermore, such abnormal changes have been used to develop corresponding pharmacological and nanotechnological therapeutics for PC.

Oleanolic Acid Acetate Alleviates Cisplatin-Induced Nephrotoxicity via Inhibition of Apoptosis and Necroptosis In Vitro and In Vivo

Cisplatin is a widely used anti-cancer drug for treating solid tumors, but it is associated with severe side effects, including nephrotoxicity. Various studies have suggested that the nephrotoxicity of cisplatin could be overcome; nonetheless, an effective adjuvant drug has not yet been established. Oleanolic acid acetate (OAA), a triterpenoid isolated from Vigna angularis, is commonly used to treat inflammatory and allergic diseases. This study aimed to investigate the protective effects of OAA against cisplatin-induced apoptosis and necroptosis using TCMK-1 cells and a mouse model. In cisplatin-treated TCMK-1 cells, OAA treatment significantly reduced Bax and cleaved-caspase3 expression, whereas it increased Bcl-2 expression. Moreover, in a cisplatin-induced kidney injury mouse model, OAA treatment alleviated weight loss in the body and major organs and also relieved cisplatin-induced nephrotoxicity symptoms. RNA sequencing analysis of kidney tissues identified lipocalin-2 as the most upregulated gene by cisplatin. Additionally, necroptosis-related genes such as receptor-interacting protein kinase (RIPK) and mixed lineage kinase domain-like (MLKL) were identified. In an in vitro study, the phosphorylation of RIPKs and MLKL was reduced by OAA pretreatment in both cisplatin-treated cells and cells boosted via co-treatment with z-VAD-FMK. In conclusion, OAA could protect the kidney from cisplatin-induced nephrotoxicity and may serve as an anti-cancer adjuvant.

Synthesis and Biological Evaluation of Some New 3-Aryl-2-thioxo-2,3-dihydroquinazolin-4(1H)-ones and 3-Aryl-2-(benzylthio)quinazolin-4(3H)-ones as Antioxidants; COX-2, LDHA, α-Glucosidase and α-Amylase Inhibitors; and Anti-Colon Carcinoma and Apoptosis-Inducing Agents

Oxidative stress, COX-2, LDHA and hyperglycemia are interlinked contributing pathways in the etiology, progression and metastasis of colon cancer. Additionally, dysregulated apoptosis in cells with genetic alternations leads to their progression in malignant transformation. Therefore, quinazolinones 3a-3h and 5a-5h were synthesized and evaluated as antioxidants, enzymes inhibitors and cytotoxic agents against LoVo and HCT-116 cells. Moreover, the most active cytotoxic derivatives were evaluated as apoptosis inducers. The results indicated that 3a, 3g and 5a were efficiently scavenged DPPH radicals with lowered IC50 values (mM) ranging from 0.165 ± 0.0057 to 0.191 ± 0.0099, as compared to 0.245 ± 0.0257 by BHT. Derivatives 3h, 5a and 5h were recognized as more potent dual inhibitors than quercetin against α-amylase and α-glucosidase, in addition to 3a, 3c, 3f and 5b-5f against α-amylase. Although none of the compounds demonstrated a higher efficiency than the reference inhibitors against COX-2 and LDHA, 3a and 3g were identified as the most active derivatives. Molecular docking studies were used to elucidate the binding affinities and binding interactions between the inhibitors and their target proteins. Compounds 3a and 3f showed cytotoxic activities, with IC50 values (µM) of 294.32 ± 8.41 and 383.5 ± 8.99 (LoVo), as well as 298.05 ± 13.26 and 323.59 ± 3.00 (HCT-116). The cytotoxicity mechanism of 3a and 3f could be attributed to the modulation of apoptosis regulators (Bax and Bcl-2), the activation of intrinsic and extrinsic apoptosis pathways via the upregulation of initiator caspases-8 and -9 as well as executioner caspase-3, and the arrest of LoVo and HCT-116 cell cycles in the G2/M and G1 phases, respectively. Lastly, the physicochemical, medicinal chemistry and ADMET properties of all compounds were predicted.

Butyrate inhibits the mitochondrial complex Ι to mediate mitochondria-dependent apoptosis of cervical cancer cells

BACKGROUND

Cervical cancer (CC) is a common gynecological malignancy with high morbidity worldwide. Butyrate, a short-chain fatty acid produced by intestinal flora, has been reported to inhibit cervical carcinogenesis. This study aimed to investigate the pro-apoptotic effects of butyrate on CC and the underlying mechanisms.

METHODS

Human HeLa and Ca Ski cells were used in this study. Cell proliferation, cell migration and invasion were detected by CCK-8 and EdU staining, transwell and wound healing assay, respectively. Cell cycle, mitochondrial membrane potential and apoptosis were evaluated by flow cytometry. Western blot and RT-qPCR were carried out to examine the related genes and proteins to the mitochondrial complex Ι and apoptosis. Metabolite changes were analyzed by energy metabolomics and assay kits. The association between G protein-coupled receptor 41, 43, 109a and CC prognosis was analyzed using data from The Cancer Genome Atlas (TCGA).

RESULTS

CCK-8 results showed significant inhibition of CC cell proliferation induced by butyrate treatment, which was confirmed by EdU staining and cell cycle detection. Data from the transwell and wound healing assay revealed that CC cell migration was dramatically reduced following butyrate treatment. Additionally, invasiveness was also decreased by butyrate. Western blot analysis showed that cleaved Caspase 3 and cleaved PARP, the enforcers of apoptosis, were increased by butyrate treatment. The results of Annexin V/PI staining and TUNEL also showed an increase in butyrate-induced apoptotic cells. Expression of Cytochrome C (Cytc), Caspase 9, Bax, but not Caspase 12 or 8, were up-regulated under butyrate exposure. Mechanistically, the decrease in mitochondrial NADH and NAD + levels after treatment with butyrate was observed by energy metabolomics and the NAD+/NADH Assay Kit, similar to the effects of the complex Ι inhibitor rotenone. Western blot results also demonstrated that the constituent proteins of mitochondrial complex Ι were reduced by butyrate. Furthermore, mitochondria-dependent apoptosis has been shown to be initiated by inhibition of the complex Ι.

CONCLUSION

Collectively, our results revealed that butyrate inhibited the proliferation, migration and invasion of CC cells, and induced mitochondrial-dependent apoptosis by inhibiting mitochondrial complex Ι.

Novel thiazolidines of potential anti-proliferation properties against esophageal squamous cell carcinoma via ERK pathway

The discovery of a new class of extracellular-signal-regulated kinase (ERK) inhibitors has been achieved via developing novel 2-imino-5-arylidene-thiazolidine analogues. A novel synthetic method employing a solid support-mediated reaction was used to construct the targeted thiazolidines through a cascade reaction with good yields. The chemical and physical stability of the new thiazolidine library has successfully been achieved by blocking the labile C5-position to aerobic oxidation. A cell viability study was performed using esophageal squamous cell carcinoma cell lines (KYSE-30 and KYSE-150) and non-tumorous esophageal epithelial cell lines (HET-1A and NES-G4T) through utilization of an MTT assay, revealing that (Z)-5-((Z)-4-bromobenzylidene)-N-(4-methoxy-2-nitrophenyl)-4,4-dimethylthiazolidin-2-imine (6g) was the best compound among the synthesized library in terms of selectivity. DAPI staining experiments were performed to visualize the morphological changes and to investigate the apoptotic activity. Moreover, western blots were used to probe the mechanism/pathway behind the observed activity/selectivity of thiazolidine 6g which established selective inhibition of phosphorylation in the ERK pathway. Molecular modeling techniques have been utilized to confirm the observed activity. A molecular docking study revealed similar binding interactions between the synthesized thiazolidines and reported co-crystalized inhibitors with ERK proteins. Thus, the present study provides a starting point for the development of interesting bioactive 2-imino-5-arylidene-thiazolidines.

The Chloroform Extracts of Vietnamese Sophora flavescens Ait. Inhibit the Proliferation of HepG2 Cells through Apoptosis Induction

The present study evaluated the effects of Sophora flavescens Ait. root extract on the proliferation of human hepatoma cell line HepG2. HPLC-UV analysis showed that the highest matrine and oxymatrine contents were obtained in the chloroform extract, compared to ethanol extract and ethyl acetate extract. The morphological analysis revealed that the chloroform extract of Sophora flavescens Ait. (SFA-CHCl3 extract) induced alterations of HepG2 cell morphology, resulting in the shrinkage of cells, the formation of debris, and cell detachment. The proliferation of HepG2 cells was inhibited by SFA-CHCl3 extract treatment. Cell cycle analysis exhibited that the cell proportion of the G0/G1 phase of HepG2 cells with SFA-CHCl3 extract treatment was decreased, while the cell proportion of the G2/M phase was increased. Flow cytometry analysis indicated a dramatic increase in the apoptotic percentage of HepG2 cells over the time of SFA-CHCl3 extract treatment. The SFA-CHCl3 extract also caused morphological changes in HepG2 nuclear, including chromatin condensation and DNA fragmentation. SFA-CHCl3 extract treatment induced the bax up-regulation and the bcl-2 down-regulation in HepG2 cells. These results revealed that SFA-CHCl3 extract could be a potential apoptosis inducer in HepG2 cells.

In vitro biochemical characterization and genotoxicity assessment of Sapindus saponaria seed extract

ETHNOPHARMACOLOGICAL RELEVANCE

Sapindus saponaria, also popularly known as soapberry, has been used in folk medicinal values because of its therapeutic properties and several compounds in its composition, which represent a target in potential for drug discovery. However, few data about its potential toxicity has been reported.

AIM OF THE STUDY

Plant proteins can perform essential roles in survival, acting as defense mechanism, as well functioning as important molecular reserves for its natural metabolism. The aim of the current study was to investigate the in vitro toxicity profile of protein extract of S. saponaria and detect protein potentially involved in biological effects such as collagen hydrolysis and inhibition of viral proteases.

MATERIALS AND METHODS

Protein extract of soapberry seeds was investigated for its cytotoxic and genotoxic action using the Ames test. The protein extract was also subjected to a partial purification process of a protease and a protease inhibitor by gel chromatography filtration techniques and the partially isolated proteins were characterized biochemically.

RESULTS

Seed proteins extract of S. saponaria was evaluated until 100 μg/mL concentration, presenting cytotoxicity and mutagenicity in bacterial model mostly when exposed to exogenous metabolic system and causing cytotoxic and genotoxic effects in HepG2 cells. The purification and partial characterization of a serine protease (43 kDa) and a cysteine protease inhibitor (32.8 kDa) from protein extract of S. Saponaria, corroborate the idea of ​​the biological use of the plant as an insecticide and larvicide. Although it shows cytotoxic, mutagenic and genotoxic effects.

CONCLUSION

The overall results of the present study provide supportive data on the potential use of proteins produced in S. saponaria seeds as pharmacological and biotechnological agents that can be further explored for the development of new drugs.

Custard Apple (Annona squamosa L.) Leaves: Nutritional Composition, Phytochemical Profile, and Health-Promoting Biological Activities

Annona squamosa L. (custard apple) belongs to the family Annonaceae and is an important tropical fruit cultivated in the West Indies, South and Central America, Ecuador, Peru, Brazil, India, Mexico, the Bahamas, Bermuda, and Egypt. Leaves of custard apple plants have been studied for their health benefits, which are attributed to a considerable diversity of phytochemicals. These compounds include phenol-based compounds, e.g., proanthocyanidins, comprising 18 different phenolic compounds, mainly alkaloids and flavonoids. Extracts from Annona squamosa leaves (ASLs) have been studied for their biological activities, including anticancer, antidiabetic, antioxidant, antimicrobial, antiobesity, lipid-lowering, and hepatoprotective functions. In the current article, we discussed the nutritional and phytochemical diversity of ASLs. Additionally, ASL extracts were discussed with respect to their biological activities, which were established by in vivo and in vitro experiments. A survey of the literature based on the phytochemical profile and health-promoting effects of ASLs showed that they can be used as potential ingredients for the development of pharmaceutical drugs and functional foods. Although there are sufficient findings available from in vitro and in vivo investigations, clinical trials are still needed to determine the exact effects of ASL extracts on human health.

New bioactive 5-arylcarboximidamidopyrazolo[3,4-c]pyridines: Synthesis, cytotoxic activity, mechanistic investigation and structure-activity relationships

In this study, a series of novel substituted pyrazolo[3,4-c]pyridin-5-ylamidines was synthesized and their cytotoxicity against three cancer cell lines (MDA-MB-231, HT-1080, PC-3), as well as a human normal cell line (AG01523) was evaluated. A number of derivatives could strongly reduce cancer cells proliferation and exhibit apoptotic induction capability, while reasonable structure-activity relationships could be extracted. Certain analogues were endowed with low toxicity against normal cells. Cell cycle analysis revealed that most of the active compounds induced a G₀/G₁ arrest of HT-1080 cells. Moreover, the potential mechanisms of the cytotoxic activity of the promising compounds were investigated in HT-1080 cells, upon study of their effects on the phosphorylation of Akt, ERK and p38 MAPK. Most of the active derivatives inhibit phosphorylation of Akt and ERK and/or induce p38 MAPK phosphorylation, providing a potential indication on the mode of action of this class.

A bismuth diethyldithiocarbamate compound induced apoptosis via mitochondria-dependent pathway and suppressed invasion in MCF-7 breast cancer cells

Interest in bismuth(III) dithiocarbamate complexes as potential drug candidates is increasing due to their low toxicity compared to other group 15 elements (pnictogen) of the periodic table. Bismuth dithiocarbamate compounds have been reported to induce greater cytotoxicity in various human carcinoma cancer cell lines. Using various in vitro cancer-related assays, we investigated the antiproliferative activity of bismuth diethyldithiocarbamate, denoted as 1, against the MCF-7 human breast adenocarcinoma cell line and the effect on genes that may be involved in antiproliferation, apoptosis, DNA fragmentation, invasion and polyubiquitination functions. In general, 1 exhibited high cytotoxicity in MCF-7 cells, with an IC₅₀ of 1.26 ± 0.02 µM, by inducing the intrinsic apoptotic pathway, as ascertained by measurements of intracellular reactive oxygen species (ROS), caspase activity, the amount of cytochrome c released and the extent of DNA fragmentation and by staining assays that reveal apoptotic cells. In addition, 1 significantly attenuated cell invasion and modulated several cancer-related genes, including PLK2, FIGF, FLT4, PARP4, and HDAC11, as determined via gene expression analysis. The NF-κB signaling pathway was inhibited by 1 upon the activation of Lys48- and Lys63-linked polyubiquitination, thus leading to its degradation via the proteasome. Overall, 1 has the potential to act as an antiproliferative agent and a proteasome inhibitor in estrogen-positive breast cancer.

The Pentose Phosphate Pathway Dynamics in Cancer and Its Dependency on Intracellular pH

The Pentose Phosphate Pathway (PPP) is one of the key metabolic pathways occurring in living cells to produce energy and maintain cellular homeostasis. Cancer cells have higher cytoplasmic utilization of glucose (glycolysis), even in the presence of oxygen; this is known as the "Warburg Effect". However, cytoplasmic glucose utilization can also occur in cancer through the PPP. This pathway contributes to cancer cells by operating in many different ways: (i) as a defense mechanism via the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) to prevent apoptosis, (ii) as a provision for the maintenance of energy by intermediate glycolysis, (iii) by increasing genomic material to the cellular pool of nucleic acid bases, (iv) by promoting survival through increasing glycolysis, and so increasing acid production, and (v) by inducing cellular proliferation by the synthesis of nucleic acid, fatty acid, and amino acid. Each step of the PPP can be upregulated in some types of cancer but not in others. An interesting aspect of this metabolic pathway is the shared regulation of the glycolytic and PPP pathways by intracellular pH (pHi). Indeed, as with glycolysis, the optimum activity of the enzymes driving the PPP occurs at an alkaline pHi, which is compatible with the cytoplasmic pH of cancer cells. Here, we outline each step of the PPP and discuss its possible correlation with cancer.

Reflexin A, a new indole alkaloid from Rauvolfia reflexa induces apoptosis against colon cancer cells

One new indole alkaloid, reflexin A (1), and two known indoles, macusine B (2) and vinorine (3), were isolated from the bark of Rauvolfia reflexa. Their structures were elucidated by 1D and 2D NMR, UV, IR, and MS spectroscopic analyses. Compound 1 displayed anticancer activity against HCT-116 colon cancer cells with an IC₅₀ value of 30.24 ± 0.75 µM. The results implied that the newly isolated 1 induced apoptosis in HCT-116 cells, suggesting its possible role as an anticancer agent. In vivo acute toxicity study was performed on compound 1 to evaluate its safety profile.

Necroptosis and Caspase-2-Mediated Apoptosis of Astrocytes and Neurons, but Not Microglia, of Rat Hippocampus and Parenchyma Caused by Angiostrongylus cantonensis Infection

Infection with the roundworm Angiostrongylus cantonensis is the main cause of eosinophilic meningitis worldwide. The underlying molecular basis of the various pathological outcomes in permissive and non-permissive hosts infected with A. cantonensis remains poorly defined. In the present study, the histology of neurological disorders in the central nervous system (CNS) of infected rats was assessed by using hematoxylin and eosin staining. Quantitative reverse transcription polymerase chain reaction (RT-qPCR), western blot and immunofluorescence (IF) were used in evolutions of the transcription and translation levels of the apoptosis-, necroptosis-, autophagy-, and pyroptosis-related genes. The distribution of apoptotic and necroptotic cells in the rat hippocampus and parenchyma was further detected using flow cytometry, and the features of the ultrastructure of the cells were examined by transmission electron microscopy (TEM). The inflammatory response upon CNS infection with A. cantonensis evolved, as characterized by the accumulation of a small number of inflammatory cells under the thickened meninges, which peaked at 21 days post-infection (dpi) and returned to normal by 35 dpi. The transcription levels and translation of caspase-2, caspase-8, RIP1 and RIP3 increased significantly at 21 and 28 dpi but decreased sharply at 35 dpi compared to those in the normal control group. However, the changes in the expression of caspase-1, caspase-3, caspase-11, Beclin-1 and LC3B were not obvious, suggesting that apoptosis and necroptosis but not autophagy or pyroptosis occurred in the brains of infected animals at 21 and 28 dpi. The results of RT-qPCR, western blot analysis, IF, flow cytometry and TEM further illustrated that necroptosis and caspase-2-mediated apoptosis occurred in astrocytes and neurons but not in microglia in the parenchyma and hippocampus of infected animals. This study provides the first evidence that neuronal and astrocytic necroptosis and caspase-2-mediated apoptosis are induced by A. cantonensis infection in the parenchymal and hippocampal regions of rats at 21 and 28 dpi but these processes are negligible at 35 dpi. These findings enhance our understanding of the pathogenesis of A. cantonensis infection and provide new insights into therapeutic approaches targeting the occurrence of cell death in astrocytes and neurons in infected patients.

Vasorin/ATIA Promotes Cigarette Smoke-Induced Transformation of Human Bronchial Epithelial Cells by Suppressing Autophagy-Mediated Apoptosis

BACKGROUND

Escaping cell death pathways is an important event during carcinogenesis. We previously identified anti-TNFα-induced apoptosis (ATIA, also known as vasorin) as an antiapoptotic factor that suppresses reactive oxygen species (ROS) production. However, the role of vasorin in lung carcinogenesis has not been investigated.

METHODS

Vasorin expression was examined in human lung cancer tissues with immunohistochemistry and database analysis. Genetic and pharmacological approaches were used to manipulate protein expression and autophagy activity in human bronchial epithelial cells (HBECs). ROS generation was measured with fluorescent indicator, apoptosis with release of lactate dehydrogenase, and cell transformation was assessed with colony formation in soft agar.

RESULTS

Vasorin expression was increased in human lung cancer tissues and cell lines, which was inversely associated with lung cancer patient survival. Cigarette smoke extract (CSE) and benzo[a]pyrene diol epoxide (BPDE)-induced vasorin expression in HBECs. Vasorin knockdown in HBECs significantly suppressed CSE-induced transformation in association with enhanced ROS accumulation and autophagy. Scavenging ROS attenuated autophagy and cytotoxicity in vasorin knockdown cells, suggesting that vasorin potentiates transformation by impeding ROS-mediated CSE cytotoxicity and improving survival of the premalignant cells. Suppression of autophagy effectively inhibited CSE-induced apoptosis, suggesting that autophagy was pro-apoptotic in CSE-treated cells. Importantly, blocking autophagy strongly potentiated CSE-induced transformation.

CONCLUSION

These results suggest that vasorin is a potential lung cancer-promoting factor that facilitates cigarette smoke-induced bronchial epithelial cell transformation by suppressing autophagy-mediated apoptosis, which could be exploited for lung cancer prevention.

Epigenetic Regulation of RIP3 Suppresses Necroptosis and Increases Resistance to Chemotherapy in NonSmall Cell Lung Cancer

INTRODUCTION

The efficacy of chemotherapeutic agents in killing cancer cells is mainly attributed to the induction of apoptosis. However, the tremendous efforts on enhancing apoptosis-related mechanisms have only moderately improved lung cancer chemotherapy, suggesting that other cell death mechanisms such as necroptosis could be involved. In this study, we investigated the role of the necroptosis pathway in the responsiveness of nonsmall cell lung cancer (NSCLC) to chemotherapy.

METHODS

In vitro cell culture and in vivo xenograft tumor therapy models and clinical sample studies are combined in studying the role of necroptosis in chemotherapy and mechanism of necroptosis suppression involving RIP3 expression regulation.

RESULTS

While chemotherapeutic drugs were able to induce necroptotic cell death, this pathway was suppressed in lung cancer cells at least partly through downregulation of RIP3 expression. Ectopic RIP3 expression significantly sensitized lung cancer cells to the cytotoxicity of anticancer drugs such as cisplatin, etoposide, vincristine, and adriamycin. In addition, RIP3 suppression was associated with RIP3 promoter methylation, and demethylation partly restored RIP3 expression and increased chemotherapeutic-induced necroptotic cell death. In a xenograft tumor therapy model, ectopic RIP3 expression significantly sensitized anticancer activity of cisplatin in vivo. Furthermore, lower RIP3 expression was associated with worse chemotherapy response in NSCLC patients.

CONCLUSION

Our results indicate that the necroptosis pathway is suppressed in lung cancer through RIP3 promoter methylation, and reactivating this pathway should be exploited for improving lung cancer chemotherapy.

Inhibitory Effect of Oat Bran Ethanol Extract on Survival and Gemcitabine Resistance of Pancreatic Cancer Cells

Pancreatic cancer (PC) is one of the most aggressive malignancies in the world. Gemcitabine (Gem), a nucleoside pyrimidine analogue, is a first-line chemotherapeutic drug for PC, but the tumor response rate of Gem is very low and resistance to Gem has emerged as a major problem in the treatment of PC. Oat bran, used as animal and human food, has been found to be beneficial to health. In this study, effects of oat bran ethanol extract (OBE) on PC cells and Gem-resistant PC cells were investigated in vitro. OBE decreased cell survival and colony forming ability of PC cells, without any cytotoxicity on the normal pancreatic cells. Flow cytometry analysis and TUNEL assay showed that the OBE reduced G1/S phase transition and induced death in PC cells through AMPK activation and downregulation of JNK. Additionally, OBE could overcome Gem resistance through reduction in RRM1/2 expression and showed synergistic effect by combinatorial treatment with Gem on Gem-resistant PC cells. Additionally, LC-MS data showed that avenacoside A was a component of OBE. Thus, this study elucidated the anti-proliferative effect of OBE and synergistic effect of OBE with Gem on PC cells and Gem-resistant cells.

Combinations of the antioxidants sulforaphane or curcumin and the conventional antineoplastics cisplatin or doxorubicin as prospects for anticancer chemotherapy

Drugs used in clinical oncology have narrow therapeutic indices with adverse toxicity often involving oxidative damage. Chemoresistance to these conventional antineoplastics is usually mediated by oxidative stress-upregulated pathways such as those of nuclear factor-kappa B (NF-κB) and hypoxia-inducible factor-1 alpha (HIF-1α). Accordingly, the use of antioxidants in combinational approaches has begun to be considered for fighting cancer because of both the protective role against adverse effects and the ability to sensitize chemoresistant cancer cells. Nuclear factor erythroid 2-related factor 2 (Nrf2) has been identified as a mediator of the cytoprotection but it is not regularly associated with tumor chemosensitization. However, some Nrf2 inducers could be exerting cytoprotective and chemosensitizing roles through a simple integrated mechanism in which the cellular level of reactive oxygen species is controlled, thus inhibiting the oxidative damage in non-target tissues and the tumor chemoresistance mediated by NF-κB or HIF-1α. As examples to show the general idea of this antioxidant combination chemotherapy, this review explores the preclinical information available for four combinations, each composed by a paradigmatic oncological drug (cisplatin or doxorubicin) and a recognized antioxidant (sulforaphane or curcumin). The issues for translating these outcomes to clinical trials are briefly discussed.

Manilkara zapota (L.) P. Royen Leaf Water Extract Induces Apoptosis in Human Hepatocellular Carcinoma (HepG2) Cells via ERK1/2/Akt1/JNK1 Signaling Pathways

Manilkara zapota (L.) P. Royen, called sapodilla, or locally known as ciku, belongs to the family Sapotaceae. We found that Manilkara zapota leaf water extract has cytotoxic effect against human hepatocellular carcinoma (HepG2) cell line in our earlier study. Therefore, this study aimed to explore the anticancer properties of Manilkara zapota leaf water extract in HepG2 cells. We also aimed to unravel yet undiscovered mechanisms and identified several expressed genes whose functions in cytotoxicity activity of Manilkara zapota leaf water extract in HepG2 cells have not been well-studied. The apoptosis and intracellular reactive oxygen species (ROS) activities were analyzed using Annexin V-propidium iodide staining and dichlorodihydrofluorescein diacetate, respectively, by NovoCyte Flow Cytometer. Bax and Bcl-2 expression were assessed using Enzyme-Linked Immunosorbent Assay. The associated molecular pathways were evaluated by quantitative real-time PCR. Overall analyses revealed that Manilkara zapota leaf water extract can increase percentage of early apoptotic cells, induce the formation of ROS, upregulate c-Jun N-terminal kinase 1 (JNK1) and inducible nitric oxide synthase (iNOS), and reduce Akt1 and vascular endothelial growth factor A (VEGFA) transcriptional activities. Our data suggest that Manilkara zapota leaf water extract can suppress the growth of HepG2 cells via modulation of ERK1/2/Akt1/JNK1 transcriptional expression.

Hinokitiol Inhibits Migration of A549 Lung Cancer Cells via Suppression of MMPs and Induction of Antioxidant Enzymes and Apoptosis

Hinokitiol, a natural monoterpenoid from the heartwood of Calocedrus formosana, has been reported to have anticancer effects against various cancer cell lines. However, the detailed molecular mechanisms and the inhibiting roles of hinokitiol on adenocarcinoma A549 cells remain to be fully elucidated. Thus, the current study was designed to evaluate the effect of hinokitiol on the migration of human lung adenocarcinoma A549 cells in vitro. The data demonstrates that hinokitiol does not effectively inhibit the viability of A549 cells at up to a 10 µM concentration. When treated with non-toxic doses (1–5 µM) of hinokitiol, the cell migration is markedly suppressed at 5 µM. Hinokitiol significantly reduced p53 expression, followed by attenuation of Bax in A549 cells. A dose-dependent inhibition of activated caspase-9 and -3 was observed in the presence of hinokitiol. An observed increase in protein expression of matrix metalloproteinases (MMPs) -2/-9 in A549 cells was significantly inhibited by hinokitiol. Remarkably, when A549 cells were subjected to hinokitiol (1–5 µM), there was an increase in the activities of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD) from the reduction in cells. In addition, the incubation of A549 cells with hinokitiol significantly activated the cytochrome c expression, which may be triggered by activation of caspase-9 followed by caspase-3. These observations indicate that hinokitiol inhibited the migration of lung cancer A549 cells through several mechanisms, including the activation of caspases-9 and -3, induction of p53/Bax and antioxidant CAT and SOD, and reduction of MMP-2 and -9 activities. It also induces cytochrome c expression. These findings demonstrate a new therapeutic potential for hinokitiol in lung cancer chemoprevention.

Ethanolic extract of Brucea javanica inhibit proliferation of HCT-116 colon cancer cells via caspase activation

Brucea javanica (L.) Merr. is a well-known plant in Chinese System of Medicine. Its fruits and seeds have been reported to possess curative properties against various ailments. The chemical constituents and biological activity of this plant have been an interesting area in plant and chemistry medicine. The aim of this study is to evaluate the antiproliferative effects of the B. javanica extract against a colon cancer cell line and identification of the chemical components derived from the extract. An ethanolic extract from B. javanica fruits was prepared by cold maceration method, subjected to LC-MS profiling to elucidate the composition abbreviated as BJEE. The extract was screened for the cytotoxicity effects on HCT-116 colon cancer cells via MTT and LDH methods. Additionally, AO/PI staining verified apoptosis features in HCT-116 cells through microscopic analysis. ROS, caspase activity, and gene expression has been performed to identify its possible mechanism of actions which contribute to apoptosis. Output data from this study showed BJEE inhibited the cell proliferation of HCT-116 colon cancer cells at IC50 value of 8.9 ± 1.32 (μg mL-1) and significantly increased the levels of caspase-8, 9, and 3/7 in treated cells in comparison to untreated. The changes in expression of caspase genes and some apoptosis genes like Bax and Bcl-2 were confirmed using RT-PCR. Phytochemical analysis by LC-MS identified six major active compounds (bruceine D, isobrucein A, quassimarin, C16 sphinganine, phytosphingosine, and enigmol) in BJEE that may play a key role in cell apoptosis. The current study showed BJEE could be a promising agent for colorectal cancer therapy by significant increase in caspase activity level, and up-regulation of the specific apoptotic genes.

In vitro and in vivo anti-tumor activity of CoQ0 against melanoma cells: inhibition of metastasis and induction of cell-cycle arrest and apoptosis through modulation of Wnt/β-catenin signaling pathways

Coenzyme Q₀ (CoQ₀, 2,3-dimethoxy-5-methyl-1,4-benzoquinone), a novel quinone derivative, has been shown to modulate cellular redox balance. However, effect of this compound on melanoma remains unclear. This study examined the in vitro or in vivo anti-tumor, apoptosis, and anti-metastasis activities of CoQ₀ (0-20 μM) through inhibition of Wnt/β-catenin signaling pathway. CoQ₀ exhibits a significant cytotoxic effect on melanoma cell lines (B16F10, B16F1, and A2058), while causing little toxicity toward normal (HaCaT) cells. The suppression of β-catenin was seen with CoQ₀ administration accompanied by a decrease in the expression of Wnt/β-catenin transcriptional target c-myc, cyclin D1, and survivin through GSK3β-independent pathway. We found that CoQ₀ treatment caused G₁ cell-cycle arrest by reducing the levels of cyclin E and CDK4. Furthermore, CoQ₀ treatment induced apoptosis through caspase-9/-3 activation, PARP degradation, Bcl-2/Bax dysregulation, and p53 expression. Notably, non- or sub-cytotoxic concentrations of CoQ₀ markedly inhibited migration and invasion, accompanied by the down-regulation of MMP-2 and -9, and up-regulation of TIMP-1 and -2 expressions in highly metastatic B16F10 cells. Furthermore, the in vivo study results revealed that CoQ₀ treatment inhibited the tumor growth in B16F10 xenografted nude mice. Histological analysis and western blotting confirmed that CoQ₀ significantly decreased the xenografted tumor progression as demonstrated by induction of apoptosis, suppression of β-catenin, and inhibition of cell cycle-, apoptotic-, and metastatic-regulatory proteins. The data suggest that CoQ₀ unveils a novel mechanism by down-regulating Wnt/β-catenin pathways and could be used as a potential lead compound for melanoma chemotherapy.

WITHDRAWN: Up-regulation of RIP3 alleviates cervical cancer progression through inducing necroptosis

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Enhancement of TRAIL-induced apoptosis by 5-fluorouracil requires activating Bax and p53 pathways in TRAIL-resistant lung cancers

Lung cancer, especially lung adenocarcinoma, is one of the main causes of death worldwide. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a primary anticancer agent and a member of the tumor necrosis factor family that selectively induces apoptosis in various tumor cells, but not in normal cells. Combination chemotherapy can be used for treating specific cancer types even at progressive stages. In the present study, we observed that 5-fluorouracil, which exerts anticancer effects by inhibiting tumor cell proliferation, enhanced TRAIL-induced apoptosis of TRAIL-resistant human adenocarcinoma A549 cells. Interestingly, 5-fluorouracil treatment markedly increased Bax and p53 levels and 5-fluorouracil and TRAIL cotreatment increased Ac-cas3 and Ac-cas8 levels compared with those in control cells. Taken together, the present study demonstrated that 5-fluorouracil enhances TRAIL-induced apoptosis in TRAIL-resistant lung adenocarcinoma cells by activating Bax and p53, and also suggest that TRAIL and 5-fluorouracil cotreatment can be used as an adequate therapeutic strategy for TRAIL-resistant human cancers.

Selective cytotoxicity of vanadium complexes on human pancreatic ductal adenocarcinoma cell line by inducing necroptosis, apoptosis and mitotic catastrophe process

The pancreatic cancer is the fourth leading cause of cancer-related death and characterized by one of the lowest five-year survival rate. The current therapeutic options are demonstrating minimal effectiveness, therefore studies on new potential anticancer compounds, with non-significant side effects are highly desirable. Recently, it was demonstrated that vanadium compounds, in particular organic derivatives, exhibit anticancer properties against different type of tumor as well as favorable biodistribution from a pancreatic cancer treatment perspective. In this research, we showed selective cytotoxic effect of vanadium complexes, containing phenanthroline and quinoline as an organic ligands, against human pancreatic ductal adenocarcinoma cell line (PANC-1), compared to non-tumor human immortalized pancreas duct epithelial cells (hTERT-HPNE). Results exhibited that vanadium complexes inhibited autophagy process in selective cytotoxic concentration as well as caused the cell cycle arrest in G2/M phase associated with mitotic catastrophe and increased level of reactive oxygen species (ROS). Moreover, in higher concentration, vanadium derivatives induced a mix type of cell death in PANC-1 cells, including apoptotic and necroptotic process. Our investigation emphasizes the anticancer potential of vanadium complexes by indicating their selective cytotoxic activity, through different process posed by alternative type of cell deaths to apoptosis-resistant cancer cells. Further studies supporting the therapeutic potential of vanadium in pancreatic cancer treatment is highly recommended.

Inhibition of Aurora kinases induces apoptosis and autophagy via AURKB/p70S6K/RPL15 axis in human leukemia cells

Leukemia is a common malignancy of blood cells with poor prognosis in many patients. Aurora kinases, a family of serine/threonine kinases, play a key role in regulating cell division and mitosis and are linked to tumorigenesis, metastasis, and poor prognosis in many human cancers including leukemia and lymphoma. Danusertib (Danu) is a pan-inhibitor of Aurora kinases with few data available in leukemia therapy. This study aimed to identify new molecular targets for Aurora kinase inhibition in human leukemia cells using quantitative proteomic analysis followed by verification experiments. There were at least 2932 proteins responding to Danu treatment, including AURKB, p70S6K, and RPL15, and 603 functional proteins and 245 canonical signaling pathways were involved in regulating cell proliferation, metabolism, apoptosis, and autophagy. The proteomic data suggested that Danu-regulated RPL15 signaling might contribute to the cancer cell killing effect. Our verification experiments confirmed that Danu negatively regulated AURKB/p70S6K/RPL15 axis with the involvement of PI3K/Akt/mTOR, AMPK, and p38 MAPK signaling pathways, leading to the induction of apoptosis and autophagy in human leukemia cells. Further studies are warranted to verify the feasibility via targeting AURKB/p70S6K/RPL15 axis for leukemia therapy.

Monobenzyltin Complex C1 Induces Apoptosis in MCF-7 Breast Cancer Cells through the Intrinsic Signaling Pathway and through the Targeting of MCF-7-Derived Breast Cancer Stem Cells via the Wnt/β-Catenin Signaling Pathway

Monobenzyltin Schiff base complex, [N-(3,5-dichloro-2-oxidobenzylidene)-4-chlorobenzyhydrazidato](o-methylbenzyl)aquatin(IV) chloride, C1, is an organotin non-platinum metal-based agent. The present study was conducted to investigate its effects on MCF-7 cells with respect to the induction of apoptosis and its inhibitory effect against MCF-7 breast cancer stem cells. As determined in a previous study, compound C1 revealed strong antiproliferative activity on MCF-7 cells with an IC₅₀ value of 2.5 μg/mL. Annexin V/propidium iodide staining coupled with flow cytometry indicated the induction of apoptosis in treated cells. Compound C1 induced apoptosis in MCF-7 cells and was mediated through the intrinsic pathway with a reduction in mitochondrial membrane potential and mitochondrial cytochrome c release to cytosol. Complex C1 activated caspase 9 as a result of cytochrome c release. Subsequently, western blot and real time PCR revealed a significant increase in Bax and Bad expression and a significant decrease in the expression levels of Bcl2 and HSP70. Furthermore, a flow cytometric analysis showed that treatment with compound C1 caused a significant arrest of MCF-7 cells in G0/G1 phase. The inhibitory analysis of compound C1 against derived MCF-7 stem cells showed a significant reduction in the aldehyde dehydrogenase-positive cell population and a significant reduction in the population of MCF-7 cancer stem cells in primary, secondary, and tertiary mammospheres. Moreover, treatment with C1 down-regulated the Wnt/β-catenin self-renewal pathway. These findings indicate that complex C1 is a suppressive agent of MCF-7 cells that functions through the induction of apoptosis, cell cycle arrest, and the targeting of MCF-7-derived cancer stem cells. This work may lead to a better treatment strategy for the reduction of breast cancer recurrence.

The inhibitory effects of carnosic acid on cervical cancer cells growth by promoting apoptosis via ROS-regulated signaling pathway

Cervical cancer has been the fourth most common cancer killing many women across the world. Carnosic acid (CA), as a phenolic diterpene, has been suggested to against cancer, exerting protective effects associated with inflammatory cytokines. It is aimed to demonstrate the therapeutic role of carnosic acid against cervical cancer and indicate its underlying molecular mechanisms. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) was performed to assess the possible anti-proliferative effects of carnosic acid. And also, colony formation was used to further estimate carnosic acid's ability in suppressing cervical cancer cells proliferation. Flow cytometry assays were performed here to indicate the alterations of cervical cancer cells cycle and the development of apoptosis. Western blot assays and RT-PCR were also applied to clarify the apoptosis-associated signaling pathways affected by reactive oxygen species (ROS) generation. And immunofluorescence was used to detect ROS-positive cells. In vivo experiments, CaSki xenograft model samples of nude mice were involved to further elucidate the effects of carnosic acid. In our results, we found that carnosic acid exerted anti-tumor ability in vitro supported by up-regulation of apoptosis and ROS production in cervical cancer cells. Also, acceleration of ROS led to the phospharylation of (c-Jun N-terminal kinase (JNK) and its-related signals, as well as activation of Endoplasmic Reticulum (ER) stress, promoting the progression of apoptosis via stimulating Caspase3 expression. The development and growth of xenograft tumors in nude mice were found to be inhibited by the administration of carnosic acid for five weeks. And the suppressed role of carnosic acid in proliferation of cervical cancer cells and apoptosis of nude mice with tumor tissues were observed in our study. Taken together, our data indicated that carnosic acid resulted in apoptosis both in vitro and vivo experiments via promoting ROS and activating JNK signaling pathways in human cervical cancer cells, which supplied a potential therapy for the application of carnosic acid in clinical treatment.

Reduction of myeloid-derived suppressor cells and lymphoma growth by a natural triterpenoid

Lymphoma is a potentially life threatening disease. The goal of this study was to investigate the therapeutic potential of a natural triterpenoid, Ganoderic acid A (GA-A) in controlling lymphoma growth both in vitro and in vivo. Here, we show that GA-A treatment induces caspase-dependent apoptotic cell death characterized by a dose-dependent increase in active caspases 9 and 3, up-regulation of pro-apoptotic BIM and BAX proteins, and a subsequent loss of mitochondrial membrane potential with release of cytochrome c. In addition to GA-A's anti-growth activity, we show that lower doses of GA-A enhance HLA class II-mediated antigen (Ag) presentation and CD4+ T cell recognition of lymphoma cells in vitro. The therapeutic relevance of GA-A treatment was also tested in vivo using the EL4 syngeneic mouse model of metastatic lymphoma. GA-A-treatment significantly prolonged survival of EL4 challenged mice and decreased tumor metastasis to the liver, an outcome accompanied by a marked down-regulation of STAT3 phosphorylation, reduction myeloid-derived suppressor cells (MDSCs), and enhancement of cytotoxic CD8+ T cells in the host. Thus, GA-A not only selectively induces apoptosis in lymphoma cells, but also enhances cell-mediated immune responses by attenuating MDSCs, and elevating Ag presentation and T cell recognition. The demonstrated therapeutic benefit indicates that GA-A is a candidate for future drug design for the treatment of lymphoma.

Autophagy-Mediated Degradation of IAPs and c-FLIP(L) Potentiates Apoptosis Induced by Combination of TRAIL and Chal-24

Combination chemotherapy is an effective strategy for increasing anticancer efficacy, reducing side effects and alleviating drug resistance. Here we report that combination of the recently identified novel chalcone derivative, chalcone-24 (Chal-24), and TNF-related apoptosis-inducing ligand (TRAIL) significantly increases cytotoxicity in lung cancer cells. Chal-24 treatment significantly enhanced TRAIL-induced activation of caspase-8 and caspase-3, and the cytotoxicity induced by combination of these agents was effectively suppressed by the pan-caspase inhibitor z-VAD-fmk. Chal-24 and TRAIL combination suppressed expression of cellular FLICE (FADD-like IL-1β-converting enzyme)-inhibitory protein large (c-FLIP(L)) and cellular inhibitor of apoptosis proteins (c-IAPs), and ectopic expression of c-FLIP(L) and c-IAPs inhibited the potentiated cytotoxicity. In addition, TRAIL and Chal-24 cooperatively activated autophagy. Suppression of autophagy effectively attenuated cytotoxicity induced by Chal-24 and TRAIL combination, which was associated with attenuation of c-FLIP(L) and c-IAPs degradation. Altogether, these results suggest that Chal-24 potentiates the anticancer activity of TRAIL through autophagy-mediated degradation of c-FLIP(L) and c-IAPs, and that combination of Chal-24 and TRAIL could be an effective approach in improving chemotherapy efficacy.

Curcuma purpurascens BI. rhizome accelerates rat excisional wound healing: involvement of Hsp70/Bax proteins, antioxidant defense, and angiogenesis activity

PURPOSE

Curcuma purpurascens BI. is a member of Zingiberaceae family. The purpose of this study is to investigate the wound healing properties of hexane extract of C. purpurascens rhizome (HECP) against excisional wound healing in rats.

MATERIALS AND METHODS

Twenty four rats were randomly divided into 4 groups: A) negative control (blank placebo, acacia gum), B) low dose of HECP, C) high dose of HECP, and D) positive control, with 6 rats in each group. Full-thickness incisions (approximately 2.00 cm) were made on the neck area of each rat. Groups 1-4 were treated two-times a day for 20 days with blank placebo, HECP (100 mg/kg), HECP (200 mg/kg), and intrasite gel as a positive control, respectively. After 20 days, hematoxylin and eosin and Masson's trichrome stainings were employed to investigate the histopathological alterations. Protein expressions of Bax and Hsp70 were examined in the wound tissues using immunohistochemistry analysis. In addition, levels of enzymatic antioxidants and malondialdehyde representing lipid peroxidation were measured in wound tissue homogenates.

RESULTS

Macroscopic evaluation of wounds showed conspicuous elevation in wound contraction after topical administration of HECP at both doses. Moreover, histopathological analysis revealed noteworthy reduction in the scar width correlated with the enhanced collagen content and fibroblast cells, accompanied by a reduction of inflammatory cells in the granulation tissues. At the molecular level, HECP facilitates wound-healing process by downregulating Bax and upregulating Hsp70 protein at the wound site. The formation of new blood vessel was observed in Masson's trichrome staining of wounds treated with HECP (100 and 200 mg/kg). In addition, HECP administration caused a significant surge in enzymatic antioxidant activities and a decline in lipid peroxidation.

CONCLUSION

These findings suggested that HECP accelerated wound-healing process in rats via antioxidant activity, angiogenesis effect and anti-inflammatory responses involving Hsp70/Bax.

Pentoxifylline during steroid window phase at induction to remission increases apoptosis in childhood with acute lymphoblastic leukemia

PURPOSE

Pentoxifylline (PTX) has been shown to increase chemotherapy-induced apoptosis. A clinical trial was developed to evaluate the effect of the addition of PTX to the induction steroid window phase in children with acute lymphoblastic leukemia (ALL).

METHODS

Thirty-two children were enrolled on this study. Children with a new diagnosis of ALL were randomly assigned to receive prednisone (PRD) 40 mg/m(2)/day only during the 7-day treatment pre-phase (PRD group, 11 patients) or to receive PRD with PTX (10 mg/kg/day) (PTX group, 11 patients); the control group included children with normal bone marrow (10 patients). Bone marrow aspiration (BMA) was performed at diagnosis (day -7) in all groups, and at day 0 (end of PRD window) for patients with ALL (PRD and PTX groups). Apoptosis was evaluated by flow cytometry (FC) using Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) stains. Statistical analysis was performed using the Mann-Whitney U test.

RESULTS

Apoptotic index at day -7 was similar in all groups. However, at day 0 post-treatment, apoptosis was significantly higher in the PTX group than in the PRD group (p < 0.001). There were no serious adverse effects associated with PTX.

CONCLUSIONS

PTX potentiates blast apoptosis induced by PRD in children with ALL during steroid window phase.

Mechanisms of Drug Resistance in Veterinary Oncology- A Review with an Emphasis on Canine Lymphoma

Drug resistance (DR) is the major limiting factor in the successful treatment of systemic neoplasia with cytotoxic chemotherapy. DR can be either intrinsic or acquired, and although the development and clinical implications are different, the underlying mechanisms are likely to be similar. Most causes for DR are pharmacodynamic in nature, result from adaptations within the tumor cell and include reduced drug uptake, increased drug efflux, changes in drug metabolism or drug target, increased capacity to repair drug-induced DNA damage or increased resistance to apoptosis. The role of active drug efflux transporters, and those of the ABC-transporter family in particular, have been studied extensively in human oncology and to a lesser extent in veterinary medicine. Methods reported to assess ABC-transporter status include detection of the actual protein (Western blot, immunohistochemistry), mRNA or ABC-transporter function. The three major ABC-transporters associated with DR in human oncology are ABCB1 or P-gp, ABCC1 or MRP1, and ABCG2 or BCRP, and have been demonstrated in canine cell lines, healthy dogs and dogs with cancer. Although this supports a causative role for these ABC-transporters in DR cytotoxic agents in the dog, the relative contribution to the clinical phenotype of DR in canine cancer remains an area of debate and requires further prospective studies.

Pachymic acid induces apoptosis via activating ROS-dependent JNK and ER stress pathways in lung cancer cells

BACKGROUND

Pachymic acid (PA), a lanostane-type triterpenoid from Poria cocos, has been reported to possess anti-emetic, anti-inflammatory, and anti-cancer properties. Nonetheless, the anti-tumor effect of PA in lung cancer cells remains unclear. Herein, we report the chemotherapeutic effects and underlying mechanisms of PA against human lung cancer.

METHODS

The anti-proliferative ability of PA on lung cancer cells was assessed by MTT, colony formation and EdU proliferation assays. Flow cytometric analysis was used to detect cell cycle changes. Apoptosis was determined by annexin V/PI double-staining and the DNA ladder formation assays. The expressions of the apoptosis-related proteins were analysed by western blot. The in vivo efficacy of PA was measured using a NCI-H23 xenograft model in nude mice.

RESULTS

PA exhibited anti-tumor effects in vitro accompanied by induction of G2/M phase arrest and apoptosis in NCI-H23 and NCI-H460 lung cancer cells. Mechanistically, our data showed that PA induced reactive oxygen species (ROS) production, resulting in the activation of both c-Jun N-terminal kinase (JNK) and endoplasmic reticulum (ER) stress apoptotic pathways in lung cancer cells. Moreover, blockage of ROS production reversed PA-induced JNK and ER stress activation. Finally, PA inhibited the growth of NCI-H23 xenograft tumors without causing any host toxicity, and inhibited cell proliferation and induction of apoptosis of tumor cells in tumor xenograft tissues.

CONCLUSIONS

In summary, our study demonstrates that PA induces apoptosis through activation of the JNK and ER stress pathways in human lung cancer cells. Our findings provide a rationale for the potential application of PA in lung cancer therapy.

The chemopreventive potential of Curcuma purpurascens rhizome in reducing azoxymethane-induced aberrant crypt foci in rats

Curcuma purpurascens BI. rhizome, a member of the Zingiberaceae family, is a popular spice in Indonesia that is traditionally used in assorted remedies. Dichloromethane extract of C. purpurascens BI. rhizome (DECPR) has previously been shown to have an apoptosis-inducing effect on colon cancer cells. In the present study, we examined the potential of DECPR to prevent colon cancer development in rats treated with azoxymethane (AOM) (15 mg/kg) by determining the percentage inhibition in incidence of aberrant crypt foci (ACF). Starting from the day immediately after AOM treatment, three groups of rats were orally administered once a day for 2 months either 10% Tween 20 (5 mL/kg, cancer control), DECPR (250 mg/kg, low dose), or DECPR (500 mg/kg, high dose). Meanwhile, the control group was intraperitoneally injected with 5-fluorouracil (35 mg/kg) for 5 consecutive days. After euthanizing the rats, the number of ACF was enumerated in colon tissues. Bax, Bcl-2, and proliferating cell nuclear antigen (PCNA) protein expressions were examined using immunohistochemical and Western blot analyses. Antioxidant enzymatic activity was measured in colon tissue homogenates and associated with malondialdehyde level. The percentage inhibition of ACF was 56.04% and 68.68% in the low- and high-dose DECPR-treated groups, respectively. The ACF inhibition in the treatment control group was 74.17%. Results revealed that DECPR exposure at both doses significantly decreased AOM-induced ACF formation, which was accompanied by reduced expression of PCNA. Upregulation of Bax and downregulation of Bcl-2 suggested the involvement of apoptosis in the chemopreventive effect of DECPR. In addition, the oxidative stress resulting from AOM treatment was significantly attenuated after administration of DECPR, which was shown by the elevated antioxidant enzymatic activity and reduced malondialdehyde level. Taken together, the present data clearly indicate that DECPR significantly inhibits ACF formation in AOM-treated rats and may offer protection against colon cancer development.

Chemopreventive Activity of Ferulago angulate against Breast Tumor in Rats and the Apoptotic Effect of Polycerasoidin in MCF7 Cells: A Bioassay-Guided Approach

Ferulago angulata leaf hexane extract (FALHE) was found to be a potent inducer of MCF7 cell apoptosis. The aims of the present study were to investigate the in vivo chemopreventive effect of FALHE in rats, to identify the contributing anticancer compound in FALHE and to determine its potential mechanism of action against MCF7 cells. Thirty rats harboring LA7-induced breast tumors were divided into five groups: tumor control, low-dose FALHE, high-dose FALHE, treatment control (tamoxifen) and normal control. Breast tissues were then subjected to histopathological and immunohistochemical analyses. A bioassay-guided investigation on FALHE was performed to identify the cytotoxic compound and its mechanism of action through flow cytometry, real-time qPCR and western blotting analyses. An in vivo study showed that FALHE suppressed the expression of the tumor markers PCNA and Ki67. The tumor size was reduced from 2031 ± 281 mm³ to 432 ± 201 mm³ after FALHE treatment. FALHE administration induced apoptosis in breast tumor cells, and this was confirmed by high expression levels of Bax, p53 and caspase 3. Cell cycle arrest was suggested by the expression of p21 and p27. The in vitro experimental results resulted in the isolation of polycerasoidin as a bioactive ingredient of FALHE with an IC₅₀ value of 3.16 ± 0.31 μg/ml against MCF7 cells. Polycerasoidin induced mitochondrial-dependent apoptosis in breast cancer cells via caspase activation and changes in the mRNA and protein expression of Bax and Bcl-2. In addition, flow cytometric analysis demonstrated that the treated MCF7 cells were arrested at the G₁ phase, and this was associated with the up-regulation of p21 and p27 at both the mRNA and protein levels. The results of the present study reinforce further investigations scrutinizing the promising potential of the F. angulata chemical constituents as breast cancer chemopreventive agents.

The chemopotential effect of Annona muricata leaves against azoxymethane-induced colonic aberrant crypt foci in rats and the apoptotic effect of Acetogenin Annomuricin E in HT-29 cells: a bioassay-guided approach

Annona muricata has been used in folk medicine for the treatment of cancer and tumors. This study evaluated the chemopreventive properties of an ethyl acetate extract of A. muricata leaves (EEAML) on azoxymethane-induced colonic aberrant crypt foci (ACF) in rats. Moreover, the cytotoxic compound of EEAML (Annomuricin E) was isolated, and its apoptosis-inducing effect was investigated against HT-29 colon cancer cell line using a bioassay-guided approach. This experiment was performed on five groups of rats: negative control, cancer control, EEAML (250 mg/kg), EEAML (500 mg/kg) and positive control (5-fluorouracil). Methylene blue staining of colorectal specimens showed that application of EEAML at both doses significantly reduced the colonic ACF formation compared with the cancer control group. Immunohistochemistry analysis showed the down-regulation of PCNA and Bcl-2 proteins and the up-regulation of Bax protein after administration of EEAML compared with the cancer control group. In addition, an increase in the levels of enzymatic antioxidants and a decrease in the malondialdehyde level of the colon tissue homogenates were observed, suggesting the suppression of lipid peroxidation. Annomuricin E inhibited the growth of HT-29 cells with an IC50 value of 1.62 ± 0.24 μg/ml after 48 h. The cytotoxic effect of annomuricin E was further substantiated by G1 cell cycle arrest and early apoptosis induction in HT-29 cells. Annomuricin E triggered mitochondria-initiated events, including the dissipation of the mitochondrial membrane potential and the leakage of cytochrome c from the mitochondria. Prior to these events, annomuricin E activated caspase 3/7 and caspase 9. Upstream, annomuricin E induced a time-dependent upregulation of Bax and downregulation of Bcl-2 at the mRNA and protein levels. In conclusion, these findings substantiate the usage of A. muricata leaves in ethnomedicine against cancer and highlight annomuricin E as one of the contributing compounds in the anticancer activity of A. muricata leaves.

Synergistic anticancer effect of cisplatin and Chal-24 combination through IAP and c-FLIPL degradation, Ripoptosome formation and autophagy-mediated apoptosis

Drug resistance is a major hurdle in anticancer chemotherapy. Combined therapy using drugs with distinct mechanisms of function may increase anticancer efficacy. We have recently identified the novel chalcone derivative, chalcone-24 (Chal-24), as a potential therapeutic that kills cancer cells through activation of an autophagy-mediated necroptosis pathway. In this report, we investigated if Chal-24 can be combined with the frontline genotoxic anticancer drug, cisplatin for cancer therapy. The combination of Chal-24 and cisplatin synergistically induced apoptotic cytotoxicity in lung cancer cell lines, which was dependent on Chal-24-induced autophagy. While cisplatin slightly potentiated the JNK/Bcl2/Beclin1 pathway for autophagy activation, its combination with Chal-24 strongly triggered proteasomal degradation of the cellular inhibitor of apoptosis proteins (c-IAPs) and formation of the Ripoptosome complex that contains RIP1, FADD and caspase 8. Furthermore, the cisplatin and Chal-24 combination induced dramatic degradation of cellular FLICE (FADD-like IL-1β-converting enzyme)-inhibitory protein large (cFLIPL) which suppresses Ripoptosome-mediated apoptosis activation. These results establish a novel mechanism for potentiation of anticancer activity with the combination of Chal-24 and cisplatin: to enhance apoptosis signaling through Ripoptosome formation and to release the apoptosis brake through c-FLIPL degradation. Altogether, our work suggests that the combination of Chal-24 and cisplatin could be employed to improve chemotherapy efficacy.

Inhibitory effect of Curcuma purpurascens BI. rhizome on HT-29 colon cancer cells through mitochondrial-dependent apoptosis pathway

Background

Curcuma purpurascens BI. (Zingiberaceae) commonly known as ‘Koneng Tinggang’ and ‘Temu Tis’ is a Javanese medicinal plant which has been used for numerous ailments and diseases in rural Javanese communities. In the present study, the apoptogenic activity of dichloromethane extract of Curcuma purpurascens BI. rhizome (DECPR) was investigated against HT-29 human colon cancer cells.

Methods

Acute toxicity study of DECPR was performed in Sprague–Dawley rats. Compounds of DECPR were analyzed by the gas chromatography–mass spectrometry–time of flight (GC-MS-TOF) analysis. Cytotoxic effect of DECPR on HT-29 cells was analyzed by MTT and lactate dehydrogenase (LDH) assays. Effects of DECPR on reactive oxygen species (ROS) formation and mitochondrial-initiated events were investigated using a high content screening system. The activities of the caspases were also measured using a fluorometric assay. The quantitative PCR analysis was carried out to examine the gene expression of Bax, Bcl-2 and Bcl-xl proteins.

Results

The in vivo acute toxicity study of DECPR on rats showed the safety of this extract at the highest dose of 5 g/kg. The GC-MS-TOF analysis of DECPR detected turmerone as the major compound in dichloromethane extract. IC₅₀ value of DECPR towards HT-29 cells after 24 h treatment was found to be 7.79 ± 0.54 μg/mL. In addition, DECPR induced LDH release and ROS generation in HT-29 cells through a mechanism involving nuclear fragmentation and cytoskeletal rearrangement. The mitochondrial-initiated events, including collapse in mitochondrial membrane potential and cytochrome c leakage was also triggered by DECPR treatment. Initiator caspase-9 and executioner caspase-3 was dose-dependently activated by DECPR. The quantitative PCR analysis on the mRNA expression of Bcl-2 family of proteins showed a significant up-regulation of Bax associated with down-regulation in Bcl-2 and Bcl-xl mRNA expression.

Conclusions

The findings presented in the current study showed that DECP suppressed the proliferation of HT-29 colon cancer cells and triggered the induction of apoptosis through mitochondrial-dependent pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-015-0534-6) contains supplementary material, which is available to authorized users.

Gastroprotective activity of Annona muricata leaves against ethanol-induced gastric injury in rats via Hsp70/Bax involvement

The popular fruit tree of Annona muricata L. (Annonaceae), known as soursop and graviola, is a widely distributed plant in Central and South America and tropical countries. Leaves of A. muricata have been reported to possess antioxidant and anti-inflammatory activities. In this study, the gastroprotective effects of ethyl acetate extract of A. muricata leaves (EEAM) were investigated against ethanol-induced gastric injury models in rats. The acute toxicity test of EEAM in rats, carried out in two doses of 1 g/kg and 2 g/kg, showed the safety of this plant, even at the highest dose of 2 g/kg. The antiulcer study in rats (five groups, n=6) was performed with two doses of EEAM (200 mg/kg and 400 mg/kg) and with omeprazole (20 mg/kg), as a standard antiulcer drug. Gross and histological features showed the antiulcerogenic characterizations of EEAM. There was significant suppression on the ulcer lesion index of rats pretreated with EEAM, which was comparable to the omeprazole effect in the omeprazole control group. Oral administration of EEAM to rats caused a significant increase in the level of nitric oxide and antioxidant activities, including catalase, glutathione, and superoxide dismutase associated with attenuation in gastric acidity, and compensatory effect on the loss of gastric wall mucus. In addition, pretreatment of rats with EEAM caused significant reduction in the level of malondialdehyde, as a marker for oxidative stress, associated with an increase in prostaglandin E2 activity. Immunohistochemical staining also demonstrated that EEAM induced the downregulation of Bax and upregulation of Hsp70 proteins after pretreatment. Collectively, the present results suggest that EEAM has a promising antiulcer potential, which could be attributed to its suppressive effect against oxidative damage and preservative effect toward gastric wall mucus.

Annona muricata leaves induce G₁ cell cycle arrest and apoptosis through mitochondria-mediated pathway in human HCT-116 and HT-29 colon cancer cells

ETHNOPHARMACOLOGICAL RELEVANCE

Annona muricata known as "the cancer killer" has been widely used in the traditional medicine for the treatment of cancer and tumors. The purpose of this study is to investigate the anticancer properties of ethyl acetate extract of Annona muricata leaves (EEAM) on HT-29 and HCT-116 colon cancer cells and the underlying mechanisms.

MATERIALS AND METHODS

The effect of EEAM on the cell proliferation of HT-29 and HCT-116 cells was analyzed by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium) assay. High content screening system (HCS) was applied to investigate the cell membrane permeability, mitochondrial membrane potential (MMP), nuclear condensation and cytochrome c translocation from mitochondria to cytosol. Reactive oxygen species (ROS) formation, lactate dehydrogenase (LDH) release and activation of caspase-3/7, -8 and -9 were measured while treatment. Flow cytometric analysis was used to determine the cell cycle distribution and phosphatidylserine externalization. The protein expression of Bax and Bcl-2 was determined using immunofluorescence analysis. In addition, the potential of EEAM to suppress the migration and invasion of colon cancer cells was also examined.

RESULTS

EEAM exerted significant cytotoxic effects on HCT-116 and HT-29 cells as determined by MTT and LDH assays. After 24 h treatment, EEAM exhibited the IC₅₀ value of 11.43 ± 1.87 µg/ml and 8.98 ± 1.24 µg/ml against HT-29 and HCT-116 cells, respectively. Flow cytometric analysis demonstrated the cell cycle arrest at G1 phase and phosphatidylserine externalization confirming the induction of apoptosis. EEAM treatment caused excessive accumulation of ROS followed by disruption of MMP, cytochrome c leakage and activation of the initiator and executioner caspases in both colon cancer cells. Immunofluorescence analysis depicted the up-regulation of Bax and down-regulation of Bcl-2 proteins while treated with EEAM. Furthermore, EEAM conspicuously blocked the migration and invasion of HT-29 and HCT-116 cells.

CONCLUSIONS

These findings provide a scientific basis for the use of A. muricata leaves in the treatment of cancer, although further in vivo studies are still required.

Growth arrest and apoptosis via caspase activation of dioscoreanone in human non-small-cell lung cancer A549 cells

Background

Dioscoreanone (DN) isolated from Dioscorea membranacea Pierre has been reported to exert potent cytotoxic effects against particular types of cancer. The present study was carried out to investigate the cytotoxicity of DN against a panel of different human lung cancer cell lines. The study further examined the underlying mechanisms of its anticancer activity in the human lung adenocarcinoma cell line A549.

Methods

Antiproliferative effects of DN were determined by SRB and CFSE assays. The effect of DN on cell cycle distribution was assessed by flow cytometric analysis. Apoptotic effects of DN were determined by sub-G₁ quantitation and Annexin V-FITC/PI flow cytometric analyses, as well as by changes in caspase-3 activity and relative levels of Bax and Bcl-2 mRNA.

Results

DN exerted antiproliferative and cytotoxic effects on all three subtypes of non-small cell lung cancer (NSCLC) cells, but not on small cell lung cancer (SCLC) cells and normal lung fibroblasts. DN slowed down the cell division and arrested the cell cycle at the G2/M phase in treated A549 cells, leading to a dose- and time- dependent increase of the sub-G1 population (apoptotic cells). Consistently, early apoptotic cells (AnnexinV ⁺/PI^-) were detected in those cells that were treated for 24 h and increased progressively over time. Moreover, the highest activity of caspase-3 in DN-treated A549 cells was detected within the first 24 h, and pretreatment with the general caspase inhibitor z-VAD-fmk completely abolished such activity and also DN-induced apoptosis in a dose-dependent manner. Additionally, DN increased the Bax/Bcl-2 ratio in treated A549 cells with time, indicating its induction of apoptosis via the mitochondrial pathway.

Conclusions

This study reveals for the first time that the anticancer activity of DN was induced through regulation of the Bcl-2 family protein-mediated mitochondrial pathway and the subsequent caspase-3 activation in A549 cancer cells, thus supporting its potential role as a natural apoptosis-inducing agent for NSCLC.

Natural compounds to overcome cancer chemoresistance: toxicological and clinical issues

INTRODUCTION

Defects in initiating or executing cell death programs are responsible for cancer chemoresistance. The growing understanding of apoptotic programs suggests that compounds simultaneously inhibiting multiple signaling pathways might provide a better therapeutic outcome than that of individual inhibitors.

AREAS COVERED

Natural compounds can modulate different survival pathways, thus enhancing the therapeutic effects of anticancer treatments. This review provides an overview of the preclinical and clinical relevance of chemosensitization, giving special reference to curcumin (CUR) and sulforaphane (SFN) as agents to overcome apoptosis resistance against chemotherapy.

EXPERT OPINION

Even if CUR and SFN are common dietary constituents, they are characterized by several problems still unresolved and hampering their development as anticancer drugs. For a drug to be safe, it must be devoid of toxicity, and some studies conducted to date raises concern about CUR and SFN safety. Moreover, the efficacy of a drug, alone or in association, is usually determined by randomized, placebo-controlled, double-blind clinical trials. No such trials have shown CUR and SFN to be effective so far. Thus, caution should be exercised when suggesting the use of CUR or SFN for cancer-related therapeutic purpose, especially for very early stage of malignancy, or in patients who are undergoing chemotherapy.

Evaluation of acute toxicity and gastroprotective activity of curcuma purpurascens BI. rhizome against ethanol-induced gastric mucosal injury in rats

Background

Curcuma purpurascens BI. is a medicinal plant from the Zingiberaceae family, which is widely used as a spice and as folk medicine. The aim of the present study is to investigate the gastroprotective activity of C. purpurascens rhizome hexane extract (CPRHE) against ethanol- induced gastric ulcers in rats.

Methods

Acute toxicity test was carried out on 36 rats (18 males and 18 females) with low dose of CPRHE (1 g/kg), high dose of CPRHE (2 g/kg) and vehicle (5% Tween 20). To determine the gastroprotective effect of CPRHE, gastric juice acidity, gross and histological gastric lesions, mucus content and ulcer index were evaluated in ethanol-induced ulcer in rats. In addition, superoxide dismutase activity, nitric oxide level and immunohistochemical evaluation of Bax and HSP70 proteins were examined.

Results

The CPRHE acute toxicity test on rats did not reveal any signs of mortality and toxicity up to 2 g/kg. The oral administration of CPRHE at doses of 200 mg/kg and 400 mg/kg and omeprazole (positive control) at a dose of 20 mg/kg to rats remarkably attenuated gastric lesions induced by ethanol. Pre-treatment of rats with CPRHE significantly replenished the depletion of mucus content caused by ethanol administration and decreased the acidity of gastric walls. Further examination of gastric mucosal homogenate revealed significant elevation of superoxide dismutase and nitric oxide activities and reduction in malondialdehyde level in CPRHE-treated group, compared to the lesion control group. Histological assessment of gastric walls obtained from rats pre-treated with CPRHE demonstrated a noteworthy decrease in hemorrhagic mucosal lesions. Immunohistochemical staining showed down-regulation of Bax protein and up-regulation of Hsp70 protein.

Conclusion

Taken together, these findings confirmed the gastroprotective effect of Curcuma purpurascens rhizome against gastric damage.

Ferulago angulata activates intrinsic pathway of apoptosis in MCF-7 cells associated with G1 cell cycle arrest via involvement of p21/p27

Ferulago angulata is a medicinal plant that is traditionally known for its anti-inflammatory and antiulcer properties. The present study was aimed to evaluate its anticancer activity and the possible mechanism of action using MCF-7 as an in vitro model. F. angulata leaf extracts were prepared using solvents in the order of increasing polarity. As determined by MTT assay, F. angulata leaves hexane extract (FALHE) revealed the strongest cytotoxicity against MCF-7 cells with the half maximal inhibitory concentration (IC₅₀) value of 5.3±0.82 μg/mL. The acute toxicity study of FALHE provided evidence of the safety of the plant extract. Microscopic and flow cytometric analysis using annexin-V probe showed an induction of apoptosis in MCF-7 by FALHE. Treatment of MCF-7 cells with FALHE encouraged the intrinsic pathway of apoptosis, with cell death transducing signals that reduced the mitochondrial membrane potential with cytochrome c release from mitochondria to cytosol. The released cytochrome c triggered the activation of caspase-9. Meanwhile, the overexpression of caspase-8 suggested the involvement of an extrinsic pathway in the induced apoptosis at the late stage of treatment. Moreover, flow cytometric analysis showed that FALHE treatment significantly arrested MCF-7 cells in the G₁ phase, which was associated with upregulation of p21 and p27 assessed by quantitative polymerase chain reaction. Immunofluorescence and the quantitative polymerase chain reaction analysis of MCF-7 cells after treatment with FALHE revealed an upregulation of Bax and a downregulation of Bcl-2 proteins. These findings proposed that FALHE suppressed the proliferation of MCF-7 cells via cell cycle arrest and the induction of apoptosis through intrinsic pathway.

Compound A398, a novel podophyllotoxin analogue: cytotoxicity and induction of apoptosis in human leukemia cells

Despite advances in oncology research, cancer is one of the leading causes of death worldwide. Thus, there is a demand for the development of more selective and effective antitumor agents. This study showed that A398, a novel podophyllotoxin analogue, was cytotoxic to the HT-29, MCF-7, MOLT-4 and HL-60 tumor cell lines, being less active in human peripheral blood mononuclear cells and normal cell lines FGH and IEC-6. Tests using the HepG2 lineage indicated that its metabolites do not contribute to its cytotoxicity. In the HL-60 cells, A398 induced apoptosis in a time and concentration-dependent manner, promoting mitochondrial depolarization, inhibition of Bcl-2, phosphatidylserine exposure, activation of caspases -8, -9 and -3, and DNA fragmentation. The production of reactive oxygen species does not seem to be a crucial event for the apoptotic process. Pretreatment with specific inhibitors of kinases ERK1/2, JNK and p38 resulted in an increased percentage of death induced by A398. These results indicate that the compound induced apoptosis through activation of intrinsic and extrinsic death pathways with the mechanism involving the inhibition of the MAPKs and Bcl-2. Taken together, our findings suggest that A398 has an anticancer potential, proving itself to be a candidate for preclinical studies.