Tirucallic acids are novel pleckstrin homology domain-dependent Akt inhibitors inducing apoptosis in prostate cancer cells

Triterpenoids from Frankincense and Boswellia: A focus on their pharmacology and 13C-NMR assignments

Here we report for the first time the entire 13C-NMR spectral assignments of 119 (out of 127) triterpenoids from the oleo-gum resins of the medicinally important genus Boswellia, which includes the culturally highly valuable Frankincense species. The complete 13C-NMR resonances of these triterpenoids isolated between 1998 and 2024 and their biological activities are presented. 13C-NMR spectroscopy is a highly powerful tool for the characterization of these bioactive natural products. The compounds are arranged according to their skeletons, i.e., ursane, oleanane, lupane, dammarane, and tirucallane triterpenes. This review will be a future reference for the identification of these compounds, which have key medicinal properties in the areas of cytotoxicity and inflammation.

Chemical Constituents and Pharmacological Properties of Frankincense: Implications for Anticancer Therapy

The discovery of novel antitumor agents derived from natural plants is a principal objective of anticancer drug research. Frankincense, a widely recognized natural antitumor medicine, has undergone a systematic review encompassing its species, chemical constituents, and diverse pharmacological activities and mechanisms. The different species of frankincense include Boswellia serrata, Somali frankincense, Boswellia frereana, and Boswellia arabica. Various frankincense extracts and compounds exhibit antitumor, anti-inflammatory, and hepatoprotective properties and antioxidation, memory enhancement, and immunological regulation capabilities. They also have comprehensive effects on regulating flora. Frankincense and its principal chemical constituents have demonstrated promising chemoprophylactic and therapeutic abilities against tumors. This review provides a systematic summary of the mechanism of action underlying the antitumor effects of frankincense and its major constituents, thus laying the foundations for developing effective tumor-combating targets.

A Simple HPTLC Approach of Quantification of Serratol and Tirucallic Acid with Boswellic Acids in Boswellia serrata by Validated Densitometric Method with MS/MS Characterization

This study was planned to develop a simple high-performance thin-layer chromatography method for qualitative and quantitative estimation of 3-acetyl-11-keto-β-boswellic acid (AKBBA), β-boswellic acid (BBA), 3-oxo-tirucallic acid (TCA) and serratol (SRT) with HPTLC-ESI-MS/MS for characterization in Boswellia serrata Roxb. oleo gum resin extract. The method was developed with hexane-ethyl acetate-toluene-chloroform-formic acid as mobile phase. RF values observed for AKBBA, BBA, TCA and SRT were 0.42, 0.39, 0.53 and 0.72, respectively. The method was validated according to International Council for Harmonisation guidelines. The concentration range for linearity was 100-500 ng/band for AKBBA and 200-700 ng/band for the other three markers with r2 > 0.99. The method resulted in good recoveries as 101.56, 100.68, 98.64 and 103.26%. The limit of detection was noticed as 25 , 37, 54 and 38 ng/band, with a limit of quantification as 76, 114, 116 and 115 ng/band, for AKBBA, BBA, TCA and SRT, respectively. The four markers were identified and confirmed in B. serrata extract using TLC-MS by indirect profiling by LC-ESI-MS/MS and were identified as terpenoids, TCA and cembranoids: AKBBA (mass/charge (m/z) = 513.00), BBA (m/z = 455.40), 3-oxo-tirucallic acid (m/z = 455.70) and SRT (m/z = 291.25), respectively.

Pleckstrin Homology [PH] domain, structure, mechanism, and contribution to human disease

The pleckstrin homology [PH] domain is a structural fold found in more than 250 proteins making it the 11th most common domain in the human proteome. 25% of family members have more than one PH domain and some PH domains are split by one, or several other, protein domains although still folding to give functioning PH domains. We review mechanisms of PH domain activity, the role PH domain mutation plays in human disease including cancer, hyperproliferation, neurodegeneration, inflammation, and infection, and discuss pharmacotherapeutic approaches to regulate PH domain activity for the treatment of human disease. Almost half PH domain family members bind phosphatidylinositols [PIs] that attach the host protein to cell membranes where they interact with other membrane proteins to give signaling complexes or cytoskeleton scaffold platforms. A PH domain in its native state may fold over other protein domains thereby preventing substrate access to a catalytic site or binding with other proteins. The resulting autoinhibition can be released by PI binding to the PH domain, or by protein phosphorylation thus providing fine tuning of the cellular control of PH domain protein activity. For many years the PH domain was thought to be undruggable until high-resolution structures of human PH domains allowed structure-based design of novel inhibitors that selectively bind the PH domain. Allosteric inhibitors of the Akt1 PH domain have already been tested in cancer patients and for proteus syndrome, with several other PH domain inhibitors in preclinical development for treatment of other human diseases.

Phytotherapy in Integrative Oncology-An Update of Promising Treatment Options

Modern phytotherapy is part of today's conventional evidence-based medicine and the use of phytopharmaceuticals in integrative oncology is becoming increasingly popular. Approximately 40% of users of such phytopharmaceuticals are tumour patients. The present review provides an overview of the most important plants and nature-based compounds used in integrative oncology and illustrates their pharmacological potential in preclinical and clinical settings. A selection of promising anti-tumour plants and ingredients was made on the basis of scientific evidence and therapeutic practical relevance and included Boswellia, gingko, ginseng, ginger, and curcumin. In addition to these nominees, there is a large number of other interesting plants and plant ingredients that can be considered for the treatment of cancer diseases or for the treatment of tumour or tumour therapy-associated symptoms. Side effects and interactions are included in the discussion. However, with the regular and intended use of phytopharmaceuticals, the occurrence of adverse side effects is rather rare. Overall, the use of defined phytopharmaceuticals is recommended in the context of a rational integrative oncology approach.

Molecular evidences on anti-inflammatory, anticancer, and memory-boosting effects of frankincense

Chemical diversity of natural products with drug-like features has attracted much attention from medicine to develop more safe and effective drugs. Their anti-inflammatory, antitumor, analgesic, and other therapeutic properties are sometimes more successful than chemical drugs in controlling disease due to fewer drug resistance and side effects and being more tolerable in a long time. Frankincense, the oleo gum resin extracted from the Boswellia species, contains some of these chemicals. The anti-inflammatory effect of its main ingredient, boswellic acid, has been traditionally used to treat many diseases, mainly those target memory functions. In this review, we have accumulated research evidence from the beneficial effect of Frankincense consumption in memory improvement and the prevention of inflammation and cancer. Besides, we have discussed the molecular pathways mediating the therapeutic effects of this natural supplement.

Review of the Chemical Composition, Pharmacological Effects, Pharmacokinetics, and Quality Control of Boswellia carterii

OBJECTIVE

This review aimed to systematically summarize studies that investigated the bioactivities of compounds and extracts from Boswellia.

METHODS

A literature review on the pharmacological properties and phytochemicals of B. carterii was performed. The information was retrieved from secondary databases such as PubMed, Chemical Abstracts Services (SciFinder), Google Scholar, and ScienceDirect.

RESULTS

The various Boswellia extracts and compounds demonstrated pharmacological properties, such as anti-inflammatory, antitumour, and antioxidant activities. B. carterii exhibited a positive effect on the treatment and prevention of many ageing diseases, such as diabetes, cancer, cardiovascular disease, and neurodegenerative diseases.

CONCLUSION

Here, we highlight the pharmacological properties and phytochemicals of B. carterii and propose further evidence-based research on plant-derived remedies and compounds.

Molecular Basis of Prostate Cancer and Natural Products as Potential Chemotherapeutic and Chemopreventive Agents

Prostate cancer is the second most common malignant cancer in males. It involves a complex process driven by diverse molecular pathways that closely related to the survival, apoptosis, metabolic and metastatic characteristics of aggressive cancer. Prostate cancer can be categorized into androgen dependent prostate cancer and castration-resistant prostate cancer and cure remains elusive due to the developed resistance of the disease. Natural compounds represent an extraordinary resource of structural scaffolds with high diversity that can offer promising chemical agents for making prostate cancer less devastating and curable. Herein, those natural compounds of different origins and structures with potential cytotoxicity and/or in vivo anti-tumor activities against prostate cancer are critically reviewed and summarized according to the cellular signaling pathways they interfere. Moreover, the anti-prostate cancer efficacy of many nutrients, medicinal plant extracts and Chinese medical formulations were presented, and the future prospects for the application of these compounds and extracts were discussed. Although the failure of conventional chemotherapy as well as involved serious side effects makes natural products ideal candidates for the treatment of prostate cancer, more investigations of preclinical and even clinical studies are necessary to make use of these medical substances reasonably. Therefore, the elucidation of structure-activity relationship and precise mechanism of action, identification of novel potential molecular targets, and optimization of drug combination are essential in natural medicine research and development.

3-Alkenyl-2-oxindoles: Synthesis, antiproliferative and antiviral properties against SARS-CoV-2

Sets of 3-alkenyl-2-oxindoles (6,10,13) were synthesized in a facile synthetic pathway through acid dehydration (EtOH/HCl) of the corresponding 3-hydroxy-2-oxoindolines (5,9,12). Single crystal (10a,c) and powder (12a,26f) X-ray studies supported the structures. Compounds 6c and 10b are the most effective agents synthesized (about 3.4, 3.3 folds, respectively) against PaCa2 (pancreatic) cancer cell line relative to the standard reference used (Sunitinib). Additionally, compound 10b reveals antiproliferative properties against MCF7 (breast) cancer cell with IC₅₀ close to that of Sunitinib. CAM testing reveals that compounds 6 and 10 demonstrated qualitative and quantitative decreases in blood vessel count and diameter with efficacy comparable to that of Sunitinib, supporting their anti-angiogenic properties. Kinase inhibitory properties support their multi-targeted inhibitory activities against VEGFR-2 and c-kit in similar behavior to that of Sunitinib. Cell cycle analysis studies utilizing MCF7 exhibit that compound 6b arrests the cell cycle at G1/S phase while, 10b reveals accumulation of the tested cell at S phase. Compounds 6a and 10b reveal potent antiviral properties against SARS-CoV-2 with high selectivity index relative to the standards (hydroxychloroquine, chloroquine). Safe profile of the potent synthesized agents, against normal cells (VERO-E6, RPE1), support the possible development of better hits based on the attained observations.

The chorioallantoic membrane as a bio-barrier model for the evaluation of nanoscale drug delivery systems for tumour therapy

In 2010, the European Parliament and the European Union adopted a directive on the protection of animals used for scientific purposes. The directive aims to protect animals in scientific research, with the final goal of complete replacement of procedures on live animals for scientific and educational purposes as soon as it is scientifically viable. Furthermore, the directive announces the implementation of the 3Rs principle: "When choosing methods, the principles of replacement, reduction and refinement should be implemented through a strict hierarchy of the requirement to use alternative methods." The visibility, accessibility, and the rapid growth of the chorioallantoic membrane (CAM) offers a clear advantage for various manipulations and for the simulation of different Bio-Barriers according to the 3R principle. The extensive vascularisation on the CAM provides an excellent substrate for the cultivation of tumour cells or tumour xenografts which could be used for the therapeutic evaluation of nanoscale drug delivery systems. The tumour can be targeted either by topical application, intratumoural injection or i.v. injection. Different application sites and biological barriers can be examined within a single model.

Natural Compounds in Sex Hormone-Dependent Cancers: The Role of Triterpenes as Therapeutic Agents

Sex hormone-dependent cancers currently contribute to the high number of cancer-related deaths worldwide. The study and elucidation of the molecular mechanisms underlying the progression of these tumors was a double-edged sword, leading to the expansion and development of new treatment options, with the cost of triggering more aggressive, therapy resistant relapses. The interaction of androgen, estrogen and progesterone hormones with specific receptors (AR, ER, PR) has emerged as a key player in the development and progression of breast, ovarian, prostate and endometrium cancers. Sex hormone-dependent cancers share a common and rather unique carcinogenesis mechanism involving the active role of endogenous and exogenous sex hormones to maintain high mitotic rates and increased cell proliferation thus increasing the probability of aberrant gene occurrence and accumulation highly correlated with abnormal cell division and the occurrence of malignant phenotypes. Cancer related hormone therapy has evolved, currently being associated with the blockade of other signaling pathways often associated with carcinogenesis and tumor progression in cancers, with promising results. However, despite the established developments, there are still several shortcomings to be addressed. Triterpenes are natural occurring secondary metabolites biosynthesized by various pathways starting from squalene cyclization. Due to their versatile therapeutic potential, including the extensively researched antiproliferative effect, these compounds are most definitely a cornerstone in the research and development of new natural/semisynthetic anticancer therapies. The present work thoroughly describes the ongoing research related to the antitumor activity of triterpenes in sex hormone-dependent cancers. Also, the current review highlights both the biological activity of various triterpenoid compounds and their featured mechanisms of action correlated with important chemical structural features.

Chrysosplenol d, a Flavonol from Artemisia annua, Induces ERK1/2-Mediated Apoptosis in Triple Negative Human Breast Cancer Cells

Triple negative human breast cancer (TNBC) is an aggressive cancer subtype with poor prognosis. Besides the better-known artemisinin, Artemisia annua L. contains numerous active compounds not well-studied yet. High-performance liquid chromatography coupled with diode-array and mass spectrometric detection (HPLC-DAD-MS) was used for the analysis of the most abundant compounds of an Artemisia annua extract exhibiting toxicity to MDA-MB-231 TNBC cells. Artemisinin, 6,7-dimethoxycoumarin, arteannuic acid were not toxic to any of the cancer cell lines tested. The flavonols chrysosplenol d and casticin selectively inhibited the viability of the TNBC cell lines, MDA-MB-231, CAL-51, CAL-148, as well as MCF7, A549, MIA PaCa-2, and PC-3. PC-3 prostate cancer cells exhibiting high basal protein kinase B (AKT) and no ERK1/2 activation were relatively resistant, whereas MDA-MB-231 cells with high basal ERK1/2 and low AKT activity were more sensitive to chrysosplenol d treatment. In vivo, chrysosplenol d and casticin inhibited MDA-MB-231 tumor growth on chick chorioallantoic membranes. Both compounds induced mitochondrial membrane potential loss and apoptosis. Chrysosplenol d activated ERK1/2, but not other kinases tested, increased cytosolic reactive oxygen species (ROS) and induced autophagy in MDA-MB-231 cells. Lysosomal aberrations and toxicity could be antagonized by ERK1/2 inhibition. The Artemisia annua flavonols chrysosplenol d and casticin merit exploration as potential anticancer therapeutics.

A Naturally Derived Carrier for Photodynamic Treatment of Squamous Cell Carcinoma: In Vitro and In Vivo Models

Photodynamic therapy (PDT) is a non-invasive treatment strategy that includes the combination of three components-a photosensitizer, a light source, and tissue oxygen. PDT can be used for the treatment of skin diseases such as squamous cell carcinoma. The photosensitizer used in this study is the naturally derived chlorophyll derivative chlorin e6 (Ce6), which was encapsulated in ultradeformable ethosomes. Singlet oxygen production by Ce6 upon laser light irradiation was not significantly affected by encapsulation into ethosomes. PDT of squamous cell carcinoma cells treated with Ce6 ethosomes triggered increased mitochondrial superoxide levels and increased caspase 3/7 activity, resulting in concentration- and light-dose-dependent cytotoxicity. Ce6 ethosomes showed good penetration into 3D squamous cell carcinoma spheroids, which upon laser light irradiation exhibited reduced size, proliferation, and viability. The PDT effect of Ce6 ethosomes was specific and showed higher cytotoxicity against squamous cell carcinoma spheroids compared to normal skin fibroblast spheroids. In addition, PDT treatment of squamous cell carcinoma xenografts grown on chorioallantoic membranes of chick eggs (CAM) exhibited reduced expression of Ki-67 proliferation marker and increased terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) staining, indicating reduced proliferation and activation of apoptosis, respectively. The results demonstrate that Ce6-loaded ethosomes represent a convenient formulation for photodynamic treatment of squamous cell carcinoma.

Anti-inflammatory and anti-cancer activities of frankincense: Targets, treatments and toxicities

The oleogum resins of Boswellia species known as frankincense have been used for ages in traditional medicine in India, China and the Arabian world independent of its use for cultural and religious rituals in Europe. During the past two decades, scientific investigations provided mounting evidence for the therapeutic potential of frankincense. We conducted a systematic review on the anti-inflammatory and anti-cancer activities of Boswellia species and their chemical ingredients (e.g. 3-O-acetyl-11-keto-β boswellic acid, α- and β-boswellic acids, 11-keto-β-boswellic acid and other boswellic acids, lupeolic acids, incensole, cembrenes, triterpenediol, tirucallic acids, and olibanumols). Frankincense acts by multiple mechanisms, e.g. by the inhibition of leukotriene synthesis, of cyclooxygenase 1/2 and 5-lipoxygenase, of oxidative stress, and by regulation of immune cells from the innate and acquired immune systems. Furthermore, frankincense modulates signaling transduction responsible for cell cycle arrest and inhibition of proliferation, angiogenesis, invasion and metastasis. Clinical trials showed the efficacy of frankincense and its phytochemicals against osteoarthritis, multiple sclerosis, asthma, psoriasis and erythematous eczema, plaque-induced gingivitis and pain. Frankincense revealed beneficial effects towards brain tumor-related edema, but did not reduce glioma size. Even if there is no treatment effect on brain tumors itself, the management of glioma-associated edema may represent a desirable improvement. The therapeutic potential against other tumor types is still speculative. Experimental toxicology and clinical trials revealed only mild adverse side effects. More randomized clinical trials are required to estimate the full clinical potential of frankincense for cancer therapy.

The Phytosterol Peniocerol Inhibits Cell Proliferation and Tumor Growth in a Colon Cancer Xenograft Model

Objective: This study aimed to evaluate the cytotoxic activity of peniocerol against human colon cancer cell lines and its antitumor effect in vivo in a xenograft model using nu/nu mice.

Materials and Methods: SW-620, HCT-15, and HCT-116 colon cancer cell lines were treated with peniocerol for cytotoxicity by crystal violet technique. Cell apoptosis induction was detected by flow cytometry, and the antitumor activity of peniocerol was evaluated in a xenograft model of HCT-116 in nu/nu mice. After treatment, the effect of peniocerol was analyzed in histological sections of tumors by immunohistochemistry using DAPI, anti-PCNA, and PARP-1 antibodies.

Results: Peniocerol inhibited cell growth and induced apoptosis in vitro in a time and dose-dependent manner. Besides, peniocerol administration (30 or 15 mg/kg) inhibited tumor growth and induced apoptosis in the xenograft mice. The lack of peniocerol toxicity was proved by a biochemical blood analysis of healthy nu/nu mice administrated with this sterol.

Conclusions: Our results proved that peniocerol induces apoptosis in vitro and in vivo assays.

Seeing the Unseen of the Combination of Two Natural Resins, Frankincense and Myrrh: Changes in Chemical Constituents and Pharmacological Activities

For the treatment of diseases, especially chronic diseases, traditional natural drugs have more effective therapeutic advantages because of their multi-target and multi-channel characteristics. Among many traditional natural medicines, resins frankincense and myrrh have been proven to be effective in the treatment of inflammation and cancer. In the West, frankincense and myrrh have been used as incense in religious and cultural ceremonies since ancient times; in traditional Chinese and Ayurvedic medicine, they are used mainly for the treatment of chronic diseases. The main chemical constituents of frankincense and myrrh are terpenoids and essential oils. Their common pharmacological effects are anti-inflammatory and anticancer. More interestingly, in traditional Chinese medicine, frankincense and myrrh have been combined as drug pairs in the same prescription for thousands of years, and their combination has a better therapeutic effect on diseases than a single drug. After the combination of frankincense and myrrh forms a blend, a series of changes take place in their chemical composition, such as the increase or decrease of the main active ingredients, the disappearance of native chemical components, and the emergence of new chemical components. At the same time, the pharmacological effects of the combination seem magically powerful, such as synergistic anti-inflammation, synergistic anticancer, synergistic analgesic, synergistic antibacterial, synergistic blood-activation, and so on. In this review, we summarize the latest research on the main chemical constituents and pharmacological activities of these two natural resins, along with chemical and pharmacological studies on the combination of the two.

Comparative Analysis of Pentacyclic Triterpenic Acid Compositions in Oleogum Resins of Different Boswellia Species and Their In Vitro Cytotoxicity against Treatment-Resistant Human Breast Cancer Cells

Pentacyclic triterpenic acids from oleogum resins of Boswellia species are of considerable therapeutic interest. Yet, their pharmaceutical development is hampered by uncertainties regarding botanical identification and the complexity of triterpenic acid mixtures. Here, a highly sensitive, selective, and accurate method for the simultaneous quantification of eight boswellic and lupeolic acids by high-performance liquid chromatography with tandem mass spectrometry detection (HPLC-MS/MS) was developed. The method was applied to the comparative analysis of 41 oleogum resins of the species B. sacra, B. dalzielli, B. papyrifera, B. serrata, B. carterii, B. neglecta, B. rivae, B. frereana, and B. occulta. Multivariate statistical analysis of the data revealed differences in the triterpenic acid composition that could be assigned to distinct Boswellia species and to their geographic growth location. Extracts of the oleogum resins exhibited cytotoxicity against the human, treatment-resistant, metastatic breast cancer cell line MDA-MB-231. Extracts from B. sacra were the most potent ones with an average IC₅₀ of 8.3 ± 0.6 µg/mL. The oleogum resin of the B. sacra was further fractionated to enrich different groups of substances. The cytotoxic efficacy against the cancer cells correlates positively with the contents of pentacyclic triterpenic acids in Boswellia extracts.

The Akt pathway in oncology therapy and beyond (Review)

Protein kinase B (Akt), similar to many other protein kinases, is at the crossroads of cell death and survival, playing a pivotal role in multiple interconnected cell signaling mechanisms implicated in cell metabolism, growth and division, apoptosis suppression and angiogenesis. Akt protein kinase displays important metabolic effects, among which are glucose uptake in muscle and fat cells or the suppression of neuronal cell death. Disruptions in the Akt-regulated pathways are associated with cancer, diabetes, cardiovascular and neurological diseases. The regulation of the Akt signaling pathway renders Akt a valuable therapeutic target. The discovery process of Akt inhibitors using various strategies has led to the identification of inhibitors with great selectivity, low side-effects and toxicity. The usefulness of Akt emerges beyond cancer therapy and extends to other major diseases, such as diabetes, heart diseases, or neurodegeneration. This review presents key features of Akt structure and functions, and presents the progress of Akt inhibitors in regards to drug development, and their preclinical and clinical activity in regards to therapeutic efficacy and safety for patients.

Boosting Antitumor Drug Efficacy with Chemically Engineered Multidomain Proteins

A facile chemical approach integrating supramolecular chemistry, site-selective protein chemistry, and molecular biology is described to engineer synthetic multidomain protein therapeutics that sensitize cancer cells selectively to significantly enhance antitumor efficacy of existing chemotherapeutics. The desired bioactive entities are assembled via supramolecular interactions at the nanoscale into structurally ordered multiprotein complexes comprising a) multiple copies of the chemically modified cyclic peptide hormone somatostatin for selective targeting and internalization into human A549 lung cancer cells expressing SST-2 receptors and b) a new cysteine mutant of the C3bot1 (C3) enzyme from Clostridium botulinum, a Rho protein inhibitor that affects and influences intracellular Rho-mediated processes like endothelial cell migration and blood vessel formation. The multidomain protein complex, SST3-Avi-C3, retargets C3 enzyme into non-small cell lung A549 cancer cells and exhibits exceptional tumor inhibition at a concentration ≈100-fold lower than the clinically approved antibody bevacizumab (Avastin) in vivo. Notably, SST3-Avi-C3 increases tumor sensitivity to a conventional chemotherapeutic (doxorubicin) in vivo. These findings show that the integrated approach holds vast promise to expand the current repertoire of multidomain protein complexes and can pave the way to important new developments in the area of targeted and combination cancer therapy.

Transcriptomic Profiling of MDA-MB-231 Cells Exposed to Boswellia Serrata and 3-O-Acetyl-B-Boswellic Acid; ER/UPR Mediated Programmed Cell Death

BACKGROUND/AIM

Triple-negative breast cancer (TNBC) is characterized by the absence of hormone receptors (estrogen, progesterone and human epidermal growth factor receptor-2) and a relatively poor prognosis due to inefficacy of hormone receptor-based chemotherapies. It is imperative that we continue to explore natural products with potential to impede growth and metastasis of TNBC. In this study, we screened over 1,000 natural products for capacity to induce cell death in TNBC (MDA-MB -231) cells.

MATERIALS AND METHODS

Frankincense (Boswellia serrata extract (BSE)) and 3-O-Acetyl-β-boswellic acid (3-OAβBA) were relatively potent, findings that corroborate the body of existing literature. The effects of BSE and 3-OAβBA on genetic parameters in MDA-MB-231 cells were evaluated by examining whole-transcriptomic influence on mRNAs, long intergenic non-coding RNA transcripts (lincRNA) and non-coding miRNAs.

RESULTS

Bio-statistical analysis demarcates the primary effect of both BSE/3-OAβBA on the up-regulation of PERK (protein kinase RNA-like endoplasmic reticulum kinase)- endoplasmic reticulum (ER)/unfolded protein response (UPR) pathways that are closely tied to activated programmed cell death (APCD). Global profiling confirms concomitant effects of BSE/3-OAβBA on upwardly expressed ER/URP APCD key components PERK (EIF2AK3), XBP1, C/EBP homologous protein transcription factor (CHOP), ATF3 and DDIT3,4/DNA-damage-inducible transcript 3,4 (GADD34). Further, BSE and/or 3-OAβBA significantly down-regulated oncogenes (OG) which, heretofore, lack functional pathway mapping, but are capable of driving epithelial-mesenchymal transition (EMT), cell survival, proliferation, metastasis and drug resistance. Among these are cell migration-inducing protein hyaluronan binding (CEMIP) [-7.22]; transglutaminase 2 [-4.96], SRY box 9 (SOX9) [-4.09], inhibitor of DNA binding 1, dominant negative helix-loop-helix protein (ID1) [-6.56]; and endothelin 1 (EDN1, [-5.06]). Likewise, in the opposite manner, BSE and/or 3-OAβBA induced the robust overexpression of tumor suppressor genes (TSGs), including: glutathione-depleting ChaC glutathione-specific gamma-glutamylcyclotransferase 1 (CHAC1) [+21.67]; the mTOR inhibitors - sestrin 2 (SESN2) [+16.4] Tribbles homolog 3 (TRIB3) [+6.2], homocysteine-inducible, endoplasmic reticulum stress-inducible, ubiquitin-like domain member 1 (HERPUD1) [+12.01]; and cystathionine gamma-lyase (CTH) [+11.12].

CONCLUSION

The anti-cancer effects of the historically used frankincense sap (BSE) appear to involve major impact on the ER/UPR response, concomitant to effecting multiple targets counter to the growth, proliferation and metastasis of TNBC cancer cells. The microarray data are available at Expression Omnibus GEO Series accession number GSE102891.

Triterpene Acids from Frankincense and Semi-Synthetic Derivatives That Inhibit 5-Lipoxygenase and Cathepsin G

Age-related diseases, such as osteoarthritis, Alzheimer’s disease, diabetes, and cardiovascular disease, are often associated with chronic unresolved inflammation. Neutrophils play central roles in this process by releasing tissue-degenerative proteases, such as cathepsin G, as well as pro-inflammatory leukotrienes produced by the 5-lipoxygenase (5-LO) pathway. Boswellic acids (BAs) are pentacyclic triterpene acids contained in the gum resin of the anti-inflammatory remedy frankincense that target cathepsin G and 5-LO in neutrophils, and might thus represent suitable leads for intervention with age-associated diseases that have a chronic inflammatory component. Here, we investigated whether, in addition to BAs, other triterpene acids from frankincense interfere with 5-LO and cathepsin G. We provide a comprehensive analysis of 17 natural tetra- or pentacyclic triterpene acids for suppression of 5-LO product synthesis in human neutrophils. These triterpene acids were also investigated for their direct interference with 5-LO and cathepsin G in cell-free assays. Furthermore, our studies were expanded to 10 semi-synthetic BA derivatives. Our data reveal that besides BAs, several tetra- and pentacyclic triterpene acids are effective or even superior inhibitors of 5-LO product formation in human neutrophils, and in parallel, inhibit cathepsin G. Their beneficial target profile may qualify triterpene acids as anti-inflammatory natural products and pharmacological leads for intervention with diseases related to aging.

Masticadienonic and 3α-OH Masticadienoic Acids Induce Apoptosis and Inhibit Cell Proliferation and Tumor Growth in Prostate Cancer Xenografts in Vivo

The triterpenes have been constituted as a group of interesting molecules as possible antitumor agents. Despite several of them not presenting a potent cytotoxic activity in vitro against cancer cells, in vivo in xenotransplant tumors studies, they show promising results. Based on the above considerations, we investigated the antitumor activity of both masticadienonic (MDA) and 3α-OH masticadienoic (3α-OH MDA) acids in a mouse prostate cancer xenograft model. Immunohistochemical assays were used to evaluate the decrease in the expression of the Proliferating Cell Nuclear Antigen (PCNA) and the Ki-67 induced by MDA and 3α-OH MDA. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay was performed to demonstrate the fragmentation of DNA. Our results showed that the two triterpenes inhibited tumor growth, had anti-proliferative effect in vivo and induced cell death by apoptosis. Collectively, our data suggested that the antitumor mechanism of MDA and 3α-OH MDA involves several molecular targets related to cell proliferation and apoptosis.

Acetyl-lupeolic acid inhibits Akt signaling and induces apoptosis in chemoresistant prostate cancer cells in vitro and in vivo

The triterpenoid acetyl-lupeolic acid (ac-LA) isolated from the oleogum resin of Boswellia carterii reduced the viability of a panel of cancer cell lines more efficiently than lupeol. There was no detectable intracellular conversion of ac-LA to lupeol and vice versa. In contrast to docetaxel, ac-LA did not induce selection of treatment-resistant cancer cells. By various parameters including DNA fragmentation, ac-LA was shown to induce apoptosis in androgen-independent PC-3 cells, whereas in MDA-MB-231 breast cancer cells, ac-LA led to cell accumulation in the G₂/M phase of the cell cycle, but not to apoptosis. In silico docking combined with in vitro kinase assays implied that ac LA potently inhibits Akt mainly by direct binding to the pleckstrin homology domain. Consistently, an Akt1 mutant deficient of the PH domain afforded partial resistance to ac-LA and complete resistance to lupeol and the Akt inhibitor III. Ac-LA inhibited phosphorylation of downstream targets of the Akt signaling pathway, which was followed by inhibition of the mTOR target p70 ribosomal six protein kinase and the nuclear accumulation of p65/NF-κB, β-catenin, and c-myc, as well as loss of the mitochondrial membrane potential. Ac-LA exhibited antiproliferative, proapoptotic, and antitumorigenic effects on PC-3-tumors xenografted either on chick chorioallantoic membranes or in nude mice. Ac-LA exhibited a clearly better safety profile than docetaxel or lupeol during chronic administration in vivo. In contrast to lupeol, ac-LA also inhibited release of vascular endothelial growth factor in vitro and accordingly angiogenesis in vivo. Thus, ac-LA deserves further exploration as a potential new antitumor compound.

The CAM cancer xenograft as a model for initial evaluation of MR labelled compounds

Non-invasive assessment of the biodistribution is of great importance during the development of new pharmaceutical compounds. In this contribution, the applicability of in ovo MRI for monitoring the biodistribution of MR contrast agent-labelled compounds was investigated in mamaria carcinomas xentotransplanted on the chorioallantoic membrane (CAM) exemplarily for Gd-DOTA and cHSA-PEO (2000)16-Gd after systemic injection of the compounds into a chorioallantoic capillary vein. MRI was performed directly prior and 30 min, 3 h, 5 h, 20 h, and 40 h after injection of the compound. The biodistribution of injected compounds could be assessed by MRI in different organs of the chicken embryo as well as in xenotransplanted tumors at all time points. A clearly prolonged enhancement of the tumor substrate could be shown for cHSA-PEO (2000)₁₆-Gd. In conclusion, high-resolution in ovo MR imaging can be used for assessment of the in vivo biodistribution of labelled compounds, thus enabling efficient non-invasive initial testing.

Akt inhibitors in cancer treatment: The long journey from drug discovery to clinical use (Review)

Targeted cancer therapies are used to inhibit the growth, progression, and metastasis of the tumor by interfering with specific molecular targets and are currently the focus of anticancer drug development. Protein kinase B, also known as Akt, plays a central role in many types of cancer and has been validated as a therapeutic target nearly two decades ago. This review summarizes the intracellular functions of Akt as a pivotal point of converging signaling pathways involved in cell growth, proliferation, apoptotis and neo‑angiogenesis, and focuses on the drug design strategies to develop potent anticancer agents targeting Akt. The discovery process of Akt inhibitors has evolved from adenosine triphosphate (ATP)‑competitive agents to alternative approaches employing allosteric sites in order to overcome the high degree of structural similarity between Akt isoforms in the catalytic domain, and considerable structural analogy to the AGC kinase family. This process has led to the discovery of inhibitors with greater specificity, reduced side-effects and lower toxicity. A second generation of Akt has inhibitors emerged by incorporating a chemically reactive Michael acceptor template to target the nucleophile cysteines in the catalytic activation loop. The review outlines the development of several promising drug candidates emphasizing the importance of each chemical scaffold. We explore the pipeline of Akt inhibitors and their preclinical and clinical examination status, presenting the potential clinical application of these agents as a monotherapy or in combination with ionizing radiation, other targeted therapies, or chemotherapy.

The critical role of Akt in cardiovascular function

Akt kinase, a member of AGC kinases, is important in many cellular functions including proliferation, migration, cell growth and metabolism. There are three known Akt isoforms which play critical and diverse roles in the cardiovascular system. Akt activity is regulated by its upstream regulatory pathways at transcriptional and post-translational levels. Beta-catenin/Tcf-4, GLI1 and Stat-3 are some of few known transcriptional regulators of AKT gene. Threonine 308 and serine 473 are the two critical phosphorylation sites of Akt1. Translocation of Akt to the cell membrane facilitates PDK1 phosphorylation of the threonine site. The serine site is phosphorylated by mTORC2. Ack1, Src, PTK6, TBK1, IKBKE and IKKε are some of the non-canonical pathways which affect the Akt activity. Protein-protein interactions of Akt to actin and Hsp90 increase the Akt activity while Akt binding to other proteins such as CTMP and TRB3 reduces the Akt activity. The action of Akt on its downstream targets determines its function in cardiovascular processes such as cell survival, growth, proliferation, angiogenesis, vasorelaxation, and cell metabolism. Akt promotes cell survival via caspase-9, YAP, Bcl-2, and Bcl-x activities. Inhibition of FoxO proteins by Akt also increases cell survival by transcriptional mechanisms. Akt stimulates cell growth and proliferation through mTORC1. Akt also increases VEGF secretion and mediates eNOS phosphorylation, vasorelaxation and angiogenesis. Akt can increase cellular metabolism through its downstream targets GSK3 and GLUT4. The alterations of Akt signaling play an important role in many cardiovascular pathological processes such as atherosclerosis, cardiac hypertrophy, and vascular remodeling. Several Akt inhibitors have been developed and tested as anti-tumor agents. They could be potential novel therapeutics for the cardiovascular diseases.

Review on the Applications and Molecular Mechanisms of Xihuang Pill in Tumor Treatment

Xihuang pill (XH) is a complementary and alternative medicine that has been used in traditional Chinese medicine (TCM) for the treatment of tumors since the 18th century. XH has clinical effects on non-Hodgkin lymphoma, breast cancer, gastric cancer, liver cancer, and bone metastasis. XH can also inhibit the growth of tumor cells and cancer stem cells, prevent tumor invasion and angiogenesis, and regulate the tumor microenvironment. XH is composed of Ru Xiang (olibanum), Mo Yao (Commiphora myrrha), She Xiang (Moschus), and Niu Huang (Calculus bovis). Some of the compounds found in these ingredients exert multiple antitumor effects and may synergize with the other ingredients. We aimed to summarize the clinical applications and molecular mechanisms of XH and its chemical composition. This review will provide potential new strategies and alternative perspectives for tumor treatments and basic research into complementary and alternative medicine.

Insights into the inhibitory mechanism of triazole-based small molecules on phosphatidylinositol-4,5-bisphosphate binding pleckstrin homology domain

Background

Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P₂] is an important regulator of several cellular processes and a precursor for other second messengers which are involved in cell signaling pathways. Signaling proteins preferably interact with PI(4,5)P₂ through its pleckstrin homology (PH) domain. Efforts are underway to design small molecule-based antagonist, which can specifically inhibit the PI(4,5)P₂/PH-domain interaction to establish an alternate strategy for the development of drug(s) for phosphoinositide signaling pathways.

Methods

Surface plasmon resonance, molecular docking, circular dichroism, competitive Förster resonance energy transfer, isothermal titration calorimetric analyses and liposome pull down assay were used.

Results

In this study, we employed 1,2,3-triazol-4-yl methanol containing small molecule (CIPs) as antagonists for PI(4,5)P₂/PH-domain interaction and determined their inhibitory effect by using competitive-surface plasmon resonance analysis (IC₅₀ ranges from 53 to 159 nM for PI(4,5)P₂/PLCδ1-PH domain binding assay). We also used phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P₃], phosphatidylinositol 3,4-bisphosphate [PI(3,4)P₂], PI(4,5)P₂ specific PH-domains to determine binding selectivity of the compounds. Various physicochemical analyses showed that the compounds have weak affect on fluidity of the model membrane but, strongly interact with the phospholipase C δ1 (PLCδ1)-PH domains. The 1,2,3-triazol-4-yl methanol moiety and nitro group of the compounds are essential for their exothermic interaction with the PH-domains. Potent compound can efficiently displace PLCδ1-PH domain from plasma membrane to cytosol in A549 cells.

Conclusions

Overall, our studies demonstrate that these compounds interact with the PIP-binding PH-domains and inhibit their membrane recruitment.

General significance

These results suggest specific but differential binding of these compounds to the PLCδ1-PH domain and emphasize the role of their structural differences in binding parameters. These triazole-based compounds could be directly used/further developed as potential inhibitor for PH domain-dependent enzyme activity.

High-resolution MRI analysis of breast cancer xenograft on the chick chorioallantoic membrane

The chick chorioallantoic membrane (CAM) model has been successfully used to study angiogenesis, cancer progression and its pharmacological treatment, tumor pharmacokinetics, and properties of novel nanomaterials. MRI is an attractive technique for non-invasive and longitudinal monitoring of physiological processes and tumor growth. This study proposes an age-adapted cooling regime for immobilization of the chick embryo, enabling high-resolution MRI of the embryo and the CAM tumor xenograft. 64 chick embryos were enrolled in this study. The novel immobilization and imaging protocol was optimized in 29 embryos. From d7 to d18 immobilization of the embryo up to 90 min was achieved by cooling at 4 °C pre-imaging, with cooling times adapted to age. Its application to tumor growth monitoring was evaluated in 15 embryos after xenotransplantation of human MDA-MB-231 breast cancer cells on CAM. Tumor volumes were monitored from d4 to d9 after grafting (d11 to d16 after incubation) applying a T2 -weighted multislice RARE sequence. At d9 after grafting, the tumors were collected and compared with the MRI-derived data by histology and weight measurements. Additional imaging methods comprising DWI, T2 mapping, and the bio-distribution of contrast agents were tested at d9 after grafting in 20 further embryos. With the adaptive cooling regime, motion artifacts could be completely avoided for up to 90 min scan time, enabling high-resolution in ovo imaging. Excellent anatomical details could be obtained in the embryo and tumors. Tumor volumes could be quantified over time. The results prove the feasibility of high-resolution MRI for longitudinal tumor and organ growth monitoring. The suggested method is promising for future applications such as testing tailored and/or targeted treatment strategies, longitudinal monitoring of tumor development, analysis of therapeutic efficacies of drugs, or assessment of tumor pharmacokinetics. The method provides an alternative to animal experimentation.

Plant natural products: from traditional compounds to new emerging drugs in cancer therapy

Natural products are chemical compounds or substances produced naturally by living organisms. With the development of modern technology, more and more plant extracts have been found to be useful to medical practice. Both micromolecules and macromolecules have been reported to have the ability to inhibit tumour progression, a novel weapon to fight cancer by targeting its 10 characteristic hallmarks. In this review, we focus on summarizing plant natural compounds and their derivatives with anti-tumour properties, into categories, according to their potential therapeutic strategies against different types of human cancer. Taken together, we present a well-grounded review of these properties, hoping to shed new light on discovery of novel anti-tumour therapeutic drugs from known plant natural sources.

Inhibition of phosphatidylinositol-3,4,5-trisphosphate binding to the AKT pleckstrin homology domain by 4-amino-1,2,5-oxadiazole derivatives

4-Amino-1,2,5-oxadiazole derivatives has been developed as an inhibitor of AKT pleckstrin homology domain.

Synthesis of the novel elemonic acid derivatives as Pin1 inhibitors

A novel series of elemonic acid derivatives were synthesized and evaluated for their inhibitory activity on Pin1. Five compounds displayed significantly improved ability to inhibit Pin1 activity at micromolar levels. Compound 10 with 2-carboxylmethylene was the most active one with an IC50 value of 0.57 μM. The docking models of Pin1 support that introduction of an acidic group to elemonic acid enhance the Pin1 inhibitory activity.

Tetra- and pentacyclic triterpene acids from the ancient anti-inflammatory remedy frankincense as inhibitors of microsomal prostaglandin E(2) synthase-1

The microsomal prostaglandin E2 synthase (mPGES)-1 is the terminal enzyme in the biosynthesis of prostaglandin (PG)E2 from cyclooxygenase (COX)-derived PGH2. We previously found that mPGES-1 is inhibited by boswellic acids (IC50 = 3-30 μM), which are bioactive triterpene acids present in the anti-inflammatory remedy frankincense. Here we show that besides boswellic acids, additional known triterpene acids (i.e., tircuallic, lupeolic, and roburic acids) isolated from frankincense suppress mPGES-1 with increased potencies. In particular, 3α-acetoxy-8,24-dienetirucallic acid (6) and 3α-acetoxy-7,24-dienetirucallic acid (10) inhibited mPGES-1 activity in a cell-free assay with IC50 = 0.4 μM, each. Structure-activity relationship studies and docking simulations revealed concrete structure-related interactions with mPGES-1 and its cosubstrate glutathione. COX-1 and -2 were hardly affected by the triterpene acids (IC50 > 10 μM). Given the crucial role of mPGES-1 in inflammation and the abundance of highly active triterpene acids in frankincence extracts, our findings provide further evidence of the anti-inflammatory potential of frankincense preparations and reveal novel, potent bioactivities of tirucallic acids, roburic acids, and lupeolic acids.

Frankincense ( rǔ xiāng; boswellia species): from the selection of traditional applications to the novel phytotherapy for the prevention and treatment of serious diseases

Frankincense (乳香 Rǔ Xiāng; Boswellia Species), the resinous extract from the trees of the genus Boswellia, has been used for centuries in cultural ceremonies, as a cosmetic agent, and as a traditional medicine to treat a variety of ailments, especially inflammatory diseases including asthma, arthritis, cerebral edema, chronic pain syndrome, chronic bowel diseases, cancer, and some other illnesses. Boswellic acids are the active compounds of frankincense and AKBA (3-O-acetyl-11-keto-β-boswellic acid) is the most important and effective acid among them. Some studies have shown that the use of frankincense can also improve the learning and enhance the memory in animals and human beings. It seems that frankincense might have a potential ability to be used as an alternative natural medicine not only for chronic and inflammatory diseases but also for brain and memory disorders.

Amino-functionalized nanoparticles as inhibitors of mTOR and inducers of cell cycle arrest in leukemia cells

Activation of the mammalian target of rapamycin (mTOR) has been implicated in anticancer drug resistance, type 2 diabetes, and aging. Here, we show that surface functionalization of polystyrene nanoparticles with amino groups (PS-NH2), but not with carboxyl groups (PS-COOH), induces G2 cell-cycle arrest and inhibition of proliferation in three leukemia cell lines. Besides, PS-NH2 inhibit angiogenesis and proliferation of leukemia cells xenografted onto the chick chorioallantoic membrane. At the molecular level, PS-NH2 inhibit, whereas PS-COOH activate mTOR signaling in leukemia cells. Consistently, PS-NH2 block activation of the mTOR downstream targets, Akt and p70 ribosomal S6 kinase 1, and induce overexpression of the cell-cycle regulator p21(Cip1/Waf1) and degradation of cyclin B1. After addition, both types of particles rapidly induce autophagy in leukemia cells. Yet, only in PS-NH2-treated cells, acidic vesicular organelles show elevated pH and impaired processing of procathepsin B. Moreover, solely in PS-NH2-treated cells, autophagy is followed by permeabilization of acidic vesicular organelles and induction of apoptosis. By contrast, primary macrophages, which do not exhibit activated mTOR signaling, proved relatively resistant to PS-NH2-induced toxicity. These data indicate that functionalized nanoparticles can be used to control activation of mTOR signaling pathways, and to influence proliferation and viability of malignant cells.

Triterpenoid resinous metabolites from the genus Boswellia: pharmacological activities and potential species-identifying properties

The resinous metabolites commonly known as frankincense or olibanum are produced by trees of the genus Boswellia and have attracted increasing popularity in Western countries in the last decade for their various pharmacological activities. This review described the pharmacological specific details mainly on anti-inflammatory, anti-carcinogenic, anti-bacterial and apoptosis-regulating activities of individual triterpenoid together with the relevant mechanism. In addition, species-characterizing triterpenic markers with the methods for their detection, bioavailability, safety and other significant properties were reviewed for further research.

Alpha-tomatine attenuation of in vivo growth of subcutaneous and orthotopic xenograft tumors of human prostate carcinoma PC-3 cells is accompanied by inactivation of nuclear factor-kappa B signaling

Background

Nuclear factor-kappa B (NF-κB) plays a role in prostate cancer and agents that suppress its activation may inhibit development or progression of this malignancy. Alpha (α)-tomatine is the major saponin present in tomato (Lycopersicon esculentum) and we have previously reported that it suppresses tumor necrosis factor-alpha (TNF-α)-induced nuclear translocation of nuclear factor-kappa B (NF-κB) in androgen-independent prostate cancer PC-3 cells and also potently induces apoptosis of these cells. However, the precise mechanism by which α-tomatine suppresses NF-κB nuclear translocation is yet to be elucidated and the anti-tumor activity of this agent in vivo has not been examined.

Methodology/ Principal Findings

In the present study we show that suppression of NF-κB activation by α-tomatine occurs through inhibition of I kappa B alpha (IκBα) kinase activity, leading to sequential suppression of IκBα phosphorylation, IκBα degradation, NF-κB/p65 phosphorylation, and NF-κB p50/p65 nuclear translocation. Consistent with its ability to induce apoptosis, α-tomatine reduced TNF-α induced activation of the pro-survival mediator Akt and its inhibition of NF-κB activation was accompanied by significant reduction in the expression of NF-κB-dependent anti-apoptotic (c-IAP1, c-IAP2, Bcl-2, Bcl-xL, XIAP and survivin) proteins. We also evaluated the antitumor activity of α-tomatine against PC-3 cell tumors grown subcutaneously and orthotopically in mice. Our data indicate that intraperitoneal administration of α-tomatine significantly attenuates the growth of PC-3 cell tumors grown at both sites. Analysis of tumor material indicates that the tumor suppressing effects of α-tomatine were accompanied by increased apoptosis and lower proliferation of tumor cells as well as reduced nuclear translocation of the p50 and p65 components of NF-κB.

Conclusion/ Significance

Our study provides first evidence for in vivo antitumor efficacy of α-tomatine against the human androgen-independent prostate cancer. The potential usefulness of α-tomatine in prostate cancer prevention and therapy requires further investigation.

Frankincense essential oil prepared from hydrodistillation of Boswellia sacra gum resins induces human pancreatic cancer cell death in cultures and in a xenograft murine model

Background

Regardless of the availability of therapeutic options, the overall 5-year survival for patients diagnosed with pancreatic cancer remains less than 5%. Gum resins from Boswellia species, also known as frankincense, have been used as a major ingredient in Ayurvedic and Chinese medicine to treat a variety of health-related conditions. Both frankincense chemical extracts and essential oil prepared from Boswellia species gum resins exhibit anti-neoplastic activity, and have been investigated as potential anti-cancer agents. The goals of this study are to identify optimal condition for preparing frankincense essential oil that possesses potent anti-tumor activity, and to evaluate the activity in both cultured human pancreatic cancer cells and a xenograft mouse cancer model.

Methods

Boswellia sacra gum resins were hydrodistilled at 78°C; and essential oil distillate fractions were collected at different durations (Fraction I at 0–2 h, Fraction II at 8–10 h, and Fraction III at 11–12 h). Hydrodistillation of the second half of gum resins was performed at 100°C; and distillate was collected at 11–12 h (Fraction IV). Chemical compositions were identified by gas chromatography–mass spectrometry (GC-MS); and total boswellic acids contents were quantified by high-performance liquid chromatography (HPLC). Frankincense essential oil-modulated pancreatic tumor cell viability and cytotoxicity were determined by colorimetric assays. Levels of apoptotic markers, signaling molecules, and cell cycle regulators expression were characterized by Western blot analysis. A heterotopic (subcutaneous) human pancreatic cancer xenograft nude mouse model was used to evaluate anti-tumor capability of Fraction IV frankincense essential oil in vivo. Frankincense essential oil-induced tumor cytostatic and cytotoxic activities in animals were assessed by immunohistochemistry.

Results

Longer duration and higher temperature hydrodistillation produced more abundant high molecular weight compounds, including boswellic acids, in frankincense essential oil fraactions. Human pancreatic cancer cells were sensitive to Fractions III and IV (containing higher molecular weight compounds) treatment with suppressed cell viability and increased cell death. Essential oil activated the caspase-dependent apoptotic pathway, induced a rapid and transient activation of Akt and Erk1/2, and suppressed levels of cyclin D1 cdk4 expression in cultured pancreatic cancer cells. In addition, Boswellia sacra essential oil Fraction IV exhibited anti-proliferative and pro-apoptotic activities against pancreatic tumors in the heterotopic xenograft mouse model.

Conclusion

All fractions of frankincense essential oil from Boswellia sacra are capable of suppressing viability and inducing apoptosis of a panel of human pancreatic cancer cell lines. Potency of essential oil-suppressed tumor cell viability may be associated with the greater abundance of high molecular weight compounds in Fractions III and IV. Although chemical component(s) responsible for tumor cell cytotoxicity remains undefined, crude essential oil prepared from hydrodistillation of Boswellia sacra gum resins might be a useful alternative therapeutic agent for treating patients with pancreatic adenocarcinoma, an aggressive cancer with poor prognosis.

A novel semisynthetic inhibitor of the FRB domain of mammalian target of rapamycin blocks proliferation and triggers apoptosis in chemoresistant prostate cancer cells

The mammalian target of rapamycin (mTOR) is a key regulator of cell growth and its uncontrolled activation is a hallmark of cancer. Moreover, mTOR activation has been implicated in the resistance of cancer cells to many anticancer drugs, rendering this pathway a promising pharmacotherapeutic target. Here we explored the capability of a semisynthetic compound to intercept mTOR signaling. We synthesized and chemically characterized a novel, semisynthetic triterpenoid derivative, 3-cinnamoyl-11-keto-β-boswellic acid (C-KβBA). Its pharmacodynamic effects on mTOR and several other signaling pathways were assessed in a number of prostate and breast cancer cell lines as well as in normal prostate epithelial cells. C-KβBA exhibits specific antiproliferative and proapoptotic effects in cancer cell lines in vitro as well as in PC-3 prostate cancer xenografts in vivo. Mechanistically, the compound significantly inhibits the cap-dependent transition machinery, decreases expression of eukaryotic translation initiation factor 4E and cyclin D1, and induces G(1) cell-cycle arrest. In contrast to conventional mTOR inhibitors, C-KβBA downregulates the phosphorylation of p70 ribosomal S6 kinase, the major downstream target of mTOR complex 1, without concomitant activation of mTOR complex 2/Akt and extracellular signal-regulated kinase pathways, and independently of protein phosphatase 2A, liver kinase B1/AMP-activated protein kinase/tuberous sclerosis complex, and F12-protein binding. At the molecular level, the compound binds to the FKBP12-rapamycin-binding domain of mTOR with high affinity, thereby competing with the endogenous mTOR activator phosphatidic acid. C-KβBA represents a new type of proapoptotic mTOR inhibitor that, due to its special mechanistic profile, might overcome the therapeutic drawbacks of conventional mTOR inhibitors.

Targeted inhibition of tumor proliferation, survival, and metastasis by pentacyclic triterpenoids: potential role in prevention and therapy of cancer

Over the last two decades, extensive research on plant-based medicinal compounds has revealed exciting and important pharmacological properties and activities of triterpenoids. Fruits, vegetables, cereals, pulses, herbs and medicinal plants are all considered to be biological sources of these triterpenoids, which have attracted great attention especially for their potent anti-inflammatory and anti-cancer activities. Published reports in the past have described the molecular mechanism(s) underlying the various biological activities of triterpenoids which range from inhibition of acute and chronic inflammation, inhibition of tumor cell proliferation, induction of apoptosis, suppression of angiogenesis and metastasis. However systematic analysis of various pharmacological properties of these important classes of compounds has not been done. In this review, we describe in detail the pre-clinical chemopreventive and therapeutic properties of selected triterpenoids that inhibit multiple intracellular signaling molecules and transcription factors involved in the initiation, progression and promotion of various cancers. Molecular targets modulated by these triterpenoids comprise, cytokines, chemokines, reactive oxygen intermediates, oncogenes, inflammatory enzymes such as COX-2, 5-LOX and MMPs, anti-apoptotic proteins, transcription factors such as NF-κB, STAT3, AP-1, CREB, and Nrf2 (nuclear factor erythroid 2-related factor) that regulate tumor cell proliferation, transformation, survival, invasion, angiogenesis, metastasis, chemoresistance and radioresistance. Finally, this review also analyzes the potential role of novel synthetic triterpenoids identified recently which mimic natural triterpenoids in physical and chemical properties and are moving rapidly from bench to bedside research.

Boswellia sacra essential oil induces tumor cell-specific apoptosis and suppresses tumor aggressiveness in cultured human breast cancer cells

Background

Gum resins obtained from trees of the Burseraceae family (Boswellia sp.) are important ingredients in incense and perfumes. Extracts prepared from Boswellia sp. gum resins have been shown to possess anti-inflammatory and anti-neoplastic effects. Essential oil prepared by distillation of the gum resin traditionally used for aromatic therapy has also been shown to have tumor cell-specific anti-proliferative and pro-apoptotic activities. The objective of this study was to optimize conditions for preparing Boswellea sacra essential oil with the highest biological activity in inducing tumor cell-specific cytotoxicity and suppressing aggressive tumor phenotypes in human breast cancer cells.

Methods

Boswellia sacra essential oil was prepared from Omani Hougari grade resins through hydrodistillation at 78 or 100 ^oC for 12 hours. Chemical compositions were identified by gas chromatography-mass spectrometry; and total boswellic acids contents were quantified by high-performance liquid chromatography. Boswellia sacra essential oil-mediated cell viability and death were studied in established human breast cancer cell lines (T47D, MCF7, MDA-MB-231) and an immortalized normal human breast cell line (MCF10-2A). Apoptosis was assayed by genomic DNA fragmentation. Anti-invasive and anti-multicellular tumor properties were evaluated by cellular network and spheroid formation models, respectively. Western blot analysis was performed to study Boswellia sacra essential oil-regulated proteins involved in apoptosis, signaling pathways, and cell cycle regulation.

Results

More abundant high molecular weight compounds, including boswellic acids, were present in Boswellia sacra essential oil prepared at 100 ^oC hydrodistillation. All three human breast cancer cell lines were sensitive to essential oil treatment with reduced cell viability and elevated cell death, whereas the immortalized normal human breast cell line was more resistant to essential oil treatment. Boswellia sacra essential oil hydrodistilled at 100 ^oC was more potent than the essential oil prepared at 78 ^oC in inducing cancer cell death, preventing the cellular network formation (MDA-MB-231) cells on Matrigel, causing the breakdown of multicellular tumor spheroids (T47D cells), and regulating molecules involved in apoptosis, signal transduction, and cell cycle progression.

Conclusions

Similar to our previous observations in human bladder cancer cells, Boswellia sacra essential oil induces breast cancer cell-specific cytotoxicity. Suppression of cellular network formation and disruption of spheroid development of breast cancer cells by Boswellia sacra essential oil suggest that the essential oil may be effective for advanced breast cancer. Consistently, the essential oil represses signaling pathways and cell cycle regulators that have been proposed as therapeutic targets for breast cancer. Future pre-clinical and clinical studies are urgently needed to evaluate the safety and efficacy of Boswellia sacra essential oil as a therapeutic agent for treating breast cancer.

Novel inhibitors of AKT: assessment of a different approach targeting the pleckstrin homology domain

Protein kinase B/AKT plays a central role in cancer. The serine/threonine kinase is overexpressed or constitutively active in many cancers and has been validated as a therapeutic target for cancer treatment. However, targeting the kinase activity has revealed itself to be a challenge due to non-selectivity of the compounds towards other kinases. This review summarizes other approaches scientists have developed to inhibit the activity and function of AKT. They consist in targeting the pleckstrin homology (PH) domain of AKT. Indeed, upon the generation of 3-phosphorylated phosphatidylinositol phosphates (PI3Ps) by PI3-kinase (PI3K), AKT translocates from the cytosol to the plasma membrane and binds to the PI3Ps via its PH domain. Thus, several analogs of PI3Ps (PI Analogs or PIAs), alkylphospholipids (APLs), such as edelfosine or inositol phophates (IPs) have been described that inhibit the binding of the PH domain to PI3Ps. Recent allostertic inhibitors and small molecules that do not bind the kinase domain but affect the kinase activity of AKT, presumably by interacting with the PH domain, have been also identified. Finally, several drug screening studies spawned novel chemical scaffolds that bind the PH domain of AKT. Together, these approaches have been more or less sucessfull in vitro and to some extent translated in preclinical studies. Several of these new AKT PH domain inhibitors exhibit promising anti-tumor activity in mouse models and some of them show synergy with ionizing radiation and chemotherapy. Early clinical trials have started and results will attest to the validity and efficacy of such approaches in the near future.

(8R)-3β,8-dihydroxypolypoda-13E,17E,21-triene induces cell cycle arrest and apoptosis in treatment-resistant prostate cancer cells

Mastic, a resinous exudate from Pistacia lentiscus, has been reported to exhibit selective cytotoxicity against different cancer cell lines. There are, however, no data published correlating distinct mastic-derived compounds with the postulated cytotoxic activity. A polypodane-type bicyclic triterpenoid, (8R)-3β,8-dihydroxypolypoda-13E,17E,21-triene (1), was isolated from P. lentiscus oleogum resin. In androgen-independent PC-3 prostate cancer cells, 1 potently inhibited the expression of cyclins D1 and E, but had no effect on the expression of the cyclin kinase inhibitor p21(Waf1/Cip1). Inhibition of the expression of cell cycle-regulating cyclins resulted in cell cycle arrest in the G₀/G₁ phase, reduction in the number of cells in the S phase, and the triggering of apoptosis, as detected by increased expression of phosphatidylserine on the cell surface and by formation of DNA laddering. In addition, 1 suppressed the formation of prostate cancer colonies in soft agar and inhibited proliferation, angiogenesis, and the growth of prostate tumors xenografted onto chick chorioallantoic membranes without overt systemic toxicity. Taken together, these data show that 1 triggers apoptosis in chemoresistant, androgen-independent human prostate cancer cells in vitro and in vivo. Thus, 1 may serve as a lead compound for targeting so far incurable androgen-insensitive prostate cancers.