The cell cycle as a target for cancer therapy: basic and clinical findings with the small molecule inhibitors flavopiridol and UCN-01

Emerging pharmaceutical therapies of Ascidian-derived natural products and derivatives

In a growing multidrug-resistant environment, the identification of potential new drug candidates with an acceptable safety profile is a substantial crux in pharmaceutical discovery. This review discusses several aspects and properties of approved marine natural products derived from ascidian sources (phylum Chordata, subphylum Tunicata) and/or their deduced analogues including their biosynthetic origin, (bio)chemical preclinical assessments and known efficacy-safety profiles, clinical status in trials, but also translational developments, opportunities and final conclusions. The review also describes the preclinical assessments of a large number of other ascidian compounds that have not been involved in clinical trials yet. Finally, the emerging research on the connectivity of the ascidian hosts and their independent or obligate symbiotic guests is discussed. The review covers the latest information on the topic of ascidian-derived marine natural products over the last two decades including 2022, with the majority of publications published in the last decade.

Biochemical features and therapeutic potential of α-Mangostin: Mechanism of action, medicinal values, and health benefits

α-Mangostin (α-MG) is a natural xanthone obtained from the pericarps of mangosteen. It exhibits excellent potential, including anti-cancer, neuroprotective, antimicrobial, antioxidant, and anti-inflammatory properties, and induces apoptosis. α-MG controls cell proliferation by modulating signaling molecules, thus implicated in cancer therapy. It possesses incredible pharmacological features and modulates crucial cellular and molecular factors. Due to its lesser water solubility and pitiable target selectivity, α-MG has limited clinical application. As a known antioxidant, α-MG has gained significant attention from the scientific community, increasing interest in extensive technical and biomedical applications. Nanoparticle-based drug delivery systems were designed to improve the pharmacological features and efficiency of α-MG. This review is focused on recent developments on the therapeutic potential of α-MG in managing cancer and neurological diseases, with a special focus on its mechanism of action. In addition, we highlighted biochemical and pharmacological features, metabolism, functions, anti-inflammatory, antioxidant effects and pre-clinical applications of α-MG.

Identification of potential ATP-competitive cyclin-dependent kinase 1 inhibitors: De novo drug generation, molecular docking, and molecular dynamics simulation

Cyclin-dependent kinases 1 (CDK1) has been identified as a potential target for the search for new antitumor drugs. However, no clinically effective CDK1 inhibitors are now available for cancer treatment. Therefore, this study aimed to offer potential CDK1 inhibitors using de novo drug generation, molecular docking, and molecular dynamics (MD) simulation studies. We first utilized the BREED algorithm (a de novo drug generation approach) to produce a novel library of small molecules targeting CDK1. To initially obtain novel potential CDK1 inhibitors with favorable physicochemical properties and excellent druggability, we performed a virtual rule-based rational drug screening on our generated library and found ten initial hits. Then, the molecular interactions and dynamic stability of these ten initial hits and CDK1 complexes during their all-atom MD simulations (total 18 μs) and binding pose metadynamics simulations were investigated, resulting in five final hits. Furthermore, another MD simulation (total 2.1 μs) with different force fields demonstrated the binding ability of the five hits to CDK1. It was found that these five hits, CBMA001 (ΔG = -29.88 kcal/mol), CBMA002 (ΔG = -34.89 kcal/mol), CBMA004 (ΔG = -32.47 kcal/mol), CBMA007 (ΔG = -31.16 kcal/mol), and CBMA008 (ΔG = -34.78 kcal/mol) possessed much greater binding affinity to CDK1 than positive compound Flavopiridol (FLP, ΔG = -25.38 kcal/mol). Finally, CBMA002 and CBMA004 were identified as excellent selective CDK1 inhibitors in silico. Together, this study provides a workflow for rational drug design and two promising selective CDK1 inhibitors that deserve further investigation.

Development and Challenges of Diclofenac-Based Novel Therapeutics: Targeting Cancer and Complex Diseases

Simple Summary

Diclofenac is a widely used drug for its anti-inflammatory and pain alleviating properties. This review summarizes the current understanding about the drug diclofenac. The potential applications of diclofenac beyond its well-known anti-inflammatory properties for other diseases such as cancer are discussed, along with existing limitations.

Abstract

Diclofenac is a highly prescribed non-steroidal anti-inflammatory drug (NSAID) that relieves inflammation, pain, fever, and aches, used at different doses depending on clinical conditions. This drug inhibits cyclooxygenase-1 and cyclooxygenase-2 enzymes, which are responsible for the generation of prostaglandin synthesis. To improve current diclofenac-based therapies, we require new molecular systematic therapeutic approaches to reduce complex multifactorial effects. However, the critical challenge that appears with diclofenac and other drugs of the same class is their side effects, such as signs of stomach injuries, kidney problems, cardiovascular issues, hepatic issues, and diarrhea. In this article, we discuss why defining diclofenac-based mechanisms, pharmacological features, and its medicinal properties are needed to direct future drug development against neurodegeneration and imperfect ageing and to improve cancer therapy. In addition, we describe various advance molecular mechanisms and fundamental aspects linked with diclofenac which can strengthen and enable the better designing of new derivatives of diclofenac to overcome critical challenges and improve their applications.

Molecular Mechanisms of Anticancer Activity of N-Glycosides of Indolocarbazoles LCS-1208 and LCS-1269

Novel indolocarbazole derivatives named LCS were synthesized by our research group. Two of them were selected as the most active anticancer agents in vivo. We studied the mechanisms of anticancer activity in accordance with the previously described effects of indolocarbazoles. Cytotoxicity was estimated by MTT assay. We analyzed LCS-DNA interactions by circular dichroism in cholesteric liquid crystals and fluorescent indicator displacement assay. The effect on the activity of topoisomerases I and II was studied by DNA relaxation assay. Expression of interferon signaling target genes was estimated by RT-PCR. Chromatin remodeling was analyzed–the effect on histone H1 localization and reactivation of epigenetically silenced genes. LCS-induced change in the expression of a wide gene set was counted by means of PCR array. Our study revealed the cytotoxic activity of the compounds against 11 cancer cell lines and it was higher than in immortalized cells. Both compounds bind DNA; binding constants were estimated—LCS-1208 demonstrated higher affinity than LCS-1269; it was shown that LCS-1208 intercalates into DNA that is typical for rebeccamycin derivatives. LCS-1208 also inhibits topoisomerases I and IIα. Being a strong intercalator and topoisomerase inhibitor, LCS-1208 upregulates the expression of interferon-induced genes. In view of LCSs binding to DNA we analyzed their influence on chromatin stability and revealed that LCS-1269 displaces histone H1. Our analysis of chromatin remodeling also included a wide set of epigenetic experiments in which LCS-1269 demonstrated complex epigenetic activity. Finally, we revealed that the antitumor effect of the compounds is based not only on binding to DNA and chromatin remodeling but also on alternative mechanisms. Both compounds induce expression changes in genes involved in neoplastic transformation and target genes of the signaling pathways in cancer cells. Despite of being structurally similar, each compound has unique biological activities. The effects of LCS-1208 are associated with intercalation. The mechanisms of LCS-1269 include influence on higher levels such as chromatin remodeling and epigenetic effects.

Downregulation of TMPRSS4 Enhances Triple-Negative Breast Cancer Cell Radiosensitivity Through Cell Cycle and Cell Apoptosis Process Impairment

Background:

Radioresistance remains a challenge for cancer radiotherapy. The present study aims to investigate the role of TMPRSS4 in triple negative breast cancer (TNBC) cell radiosensitivity.

Materials and Methods:

After transfection of MDA-MD-468 triple negative breast cancer cells line by using the lentivirus vector, the effect of TMPRSS4 down-regulation on TNBC radiosensitivity was evaluated by using cloning assay and CCK-8 assay. The CCK-8 assay was also used for performing cell proliferation analysis. Western blot was carried out to detect the expression of certain proteins related to cell cycle pathways (cyclin D1), cell apoptosis pathways (Bax, Bcl2, and Caspase3), DNA damage and DNA damage repair (TRF2, Ku80 , ˠH2AX) . The cell cycle and cell apoptosis were also investigated using flow cytometer analysis.

Results:

TMPRSS4 expression was down-regulated in MDA-MB-468 cells which enhanced MDA-MB-468 cells radiosensitivity. TMPRSS4 silencing also improved IR induced cell proliferation ability reduction and promoted cell arrested at G2/M phase mediated by 6 Gy IR associated with cyclin D1 expression inhibition. Moreover, TMPRSS4 inhibition enhanced TNBC apoptosis induced by 6 Gy IR following by over-expression of (Bax, Caspase3) and down-regulation of Bcl2 as the pro-apoptotic and anti-apoptotic proteins, respectively. Otherwise, TMPRSS4 down-regulation increases DNA damage induced by 6 Gy IR and delays DNA damage repair respectively illustrated by downregulation of TRF2 and permanent increase of Ku80 and ˠH2AX expression at 1 h and 10 h post-IR.

Conclusion:

Down-regulation of TMPRSS4 increases triple negative breast cancer cell radiosensitivity and the use of TMPRSS4 inhibitor can be encouraged for improving radiotherapy effectiveness in TNBC radioresistant patients.

Pan-Cancer Analysis Reveals the Functional Importance of Protein Lysine Modification in Cancer Development

Large-scale tumor genome sequencing projects have revealed a complex landscape of genomic mutations in multiple cancer types. A major goal of these projects is to characterize somatic mutations and discover cancer drivers, thereby providing important clues to uncover diagnostic or therapeutic targets for clinical treatment. However, distinguishing only a few somatic mutations from the majority of passenger mutations is still a major challenge facing the biological community. Fortunately, combining other functional features with mutations to predict cancer driver genes is an effective approach to solve the above problem. Protein lysine modifications are an important functional feature that regulates the development of cancer. Therefore, in this work, we have systematically analyzed somatic mutations on seven protein lysine modifications and identified several important drivers that are responsible for tumorigenesis. From published literature, we first collected more than 100,000 lysine modification sites for analysis. Another 1 million non-synonymous single nucleotide variants (SNVs) were then downloaded from TCGA and mapped to our collected lysine modification sites. To identify driver proteins that significantly altered lysine modifications, we further developed a hierarchical Bayesian model and applied the Markov Chain Monte Carlo (MCMC) method for testing. Strikingly, the coding sequences of 473 proteins were found to carry a higher mutation rate in lysine modification sites compared to other background regions. Hypergeometric tests also revealed that these gene products were enriched in known cancer drivers. Functional analysis suggested that mutations within the lysine modification regions possessed higher evolutionary conservation and deleteriousness. Furthermore, pathway enrichment showed that mutations on lysine modification sites mainly affected cancer related processes, such as cell cycle and RNA transport. Moreover, clinical studies also suggested that the driver proteins were significantly associated with patient survival, implying an opportunity to use lysine modifications as molecular markers in cancer diagnosis or treatment. By searching within protein-protein interaction networks using a random walk with restart (RWR) algorithm, we further identified a series of potential treatment agents and therapeutic targets for cancer related to lysine modifications. Collectively, this study reveals the functional importance of lysine modifications in cancer development and may benefit the discovery of novel mechanisms for cancer treatment.

Kinase inhibitors as potential agents in the treatment of multiple myeloma

Recent years have witnessed a dramatic increase in the number of therapeutic options available for the treatment of multiple myeloma (MM) - from immunomodulating agents to proteasome inhibitors to histone deacetylase (HDAC) inhibitors and, most recently, monoclonal antibodies. Used in conjunction with autologous hematopoietic stem cell transplantation, these modalities have nearly doubled the disease's five-year survival rate over the last three decades to about 50%. In spite of these advances, MM still is considered incurable as resistance and relapse are common. While small molecule protein kinase inhibitors have made inroads in the therapy of a number of cancers, to date their application to MM has been less than successful. Focusing on MM, this review examines the roles played by a number of kinases in driving the malignant state and the rationale for target development in the design of a number of kinase inhibitors that have demonstrated anti-myeloma activity in both in vitro and in vivo xenograph models, as well as those that have entered clinical trials. Among the targets and their inhibitors examined are receptor and non-receptor tyrosine kinases, cell cycle control kinases, the PI3K/AKT/mTOR pathway kinases, protein kinase C, mitogen-activated protein kinase, glycogen synthase kinase, casein kinase, integrin-linked kinase, sphingosine kinase, and kinases involved in the unfolded protein response.

Metabolic reprogramming is associated with flavopiridol resistance in prostate cancer DU145 cells

Flavopiridol (FP) is a pan-cyclin dependent kinase inhibitor, which shows strong efficacy in inducing cancer cell apoptosis. Although FP is potent against most cancer cells in vitro, unfortunately it proved less efficacious in clinical trials in various aggressive cancers. To date, the molecular mechanisms of the FP resistance are mostly unknown. Here, we report that a small fraction human prostate cancer DU145 cells can survive long-term FP treatment and emerge as FP-resistant cells (DU145FP). These DU145FP cells show accumulated mitochondrial lesions with stronger glycolytic features, and they proliferate in slow-cycling and behave highly migratory with strong anti-apoptotic potential. In addition, the cells are less sensitive to cisplatin and docetaxel-induced apoptotic pressure, and over-express multiple stem cell associated biomarkers. Our studies collectively uncover for the first time that FP-resistant prostate cancer cells show metabolic remodeling, and the metabolic plasticity might be required for the FP resistance-associated cancer cell stemness up-regulation.

A3 Adenosine Receptor Agonist Inhibited Survival of Breast Cancer Stem Cells via GLI-1 and ERK1/2 Pathway

Numerous studies have demonstrated the role of A3 adenosine receptor (A3AR) and signaling pathways in the multiple aspects of the tumor. However, there is a little study about the function of A3AR in the biological processes of cancer stem cells (CSCs). CSCs have a critical role in the maintenance and survival of breast cancer. The aim of current study was to investigate the effect of A3AR agonist on breast cancer stem cells (BCSCs). XTT assay showed antiproliferative effect of A3AR agonist (Cl-IB-MECA) on BCSCs. Our results also demonstrated that A3AR agonist reduces mammosphere formation in a dose-dependent manner. Flow cytometry analysis showed that A3AR agonist induces G1 cell cycle arrest and apoptosis in BCSCs. Western blot assay showed that A3AR agonist inhibits the expression of cell cycle and apoptotic regulatory proteins as well as the expression of ERK1/2 and GLI-1 proteins. Finally, these findings propose that A3AR agonist induces cell cycle arrest and apoptosis in BCSCs by inhibition of ERK1/2 and GLI-1 cascade. J. Cell. Biochem. 118: 2909-2920, 2017. © 2017 Wiley Periodicals, Inc.

Jellyfish extract induces apoptotic cell death through the p38 pathway and cell cycle arrest in chronic myelogenous leukemia K562 cells

Jellyfish species are widely distributed in the world's oceans, and their population is rapidly increasing. Jellyfish extracts have several biological functions, such as cytotoxic, anti-microbial, and antioxidant activities in cells and organisms. However, the anti-cancer effect of Jellyfish extract has not yet been examined. We used chronic myelogenous leukemia K562 cells to evaluate the mechanisms of anti-cancer activity of hexane extracts from Nomura's jellyfish in vitro. In this study, jellyfish are subjected to hexane extraction, and the extract is shown to have an anticancer effect on chronic myelogenous leukemia K562 cells. Interestingly, the present results show that jellyfish hexane extract (Jellyfish-HE) induces apoptosis in a dose- and time-dependent manner. To identify the mechanism(s) underlying Jellyfish-HE-induced apoptosis in K562 cells, we examined the effects of Jellyfish-HE on activation of caspase and mitogen-activated protein kinases (MAPKs), which are responsible for cell cycle progression. Induction of apoptosis by Jellyfish-HE occurred through the activation of caspases-3,-8 and -9 and phosphorylation of p38. Jellyfish-HE-induced apoptosis was blocked by a caspase inhibitor, Z-VAD. Moreover, during apoptosis in K562 cells, p38 MAPK was inhibited by pretreatment with SB203580, an inhibitor of p38. SB203580 blocked jellyfish-HE-induced apoptosis. Additionally, Jellyfish-HE markedly arrests the cell cycle in the G0/G1 phase. Therefore, taken together, the results imply that the anti-cancer activity of Jellyfish-HE may be mediated apoptosis by induction of caspases and activation of MAPK, especially phosphorylation of p38, and cell cycle arrest at the Go/G1 phase in K562 cells.

Role of apoptosis-related miRNAs in resveratrol-induced breast cancer cell death

Breast cancer is the most frequently diagnosed cancer in women, and one of the leading causes of cancer-related deaths worldwide. Recent evidences indicate that dietary agents such as resveratrol may inhibit cancer progression through modulation of microRNAs (miRNAs). We demonstrate that resveratrol regulates apoptotic and cell cycle machinery in breast cancer cells by modulating key tumor-suppressive miRNAs including miR-125b-5p, miR-200c-3p, miR-409-3p, miR-122-5p and miR-542-3p. Resveratrol-mediated miRNA modulation regulates key anti-apoptotic and cell cycle proteins including Bcl-2, X-linked inhibitor of apoptosis protein and CDKs, which are critical for its activity. Modulating miRNAs with mimics or inhibitors further validated a key role for miR-542-3p in MCF-7 and miR-122-5p in MDA-MB-231 breast cancer cell death in response to resveratrol. In conclusion, this study reveals novel miRNAs modulated by resveratrol that have a key role in breast cancer cell death.

Insights on Structural Characteristics and Ligand Binding Mechanisms of CDK2

Cyclin-dependent kinase 2 (CDK2) is a crucial regulator of the eukaryotic cell cycle. However it is well established that monomeric CDK2 lacks regulatory activity, which needs to be aroused by its positive regulators, cyclins E and A, or be phosphorylated on the catalytic segment. Interestingly, these activation steps bring some dynamic changes on the 3D-structure of the kinase, especially the activation segment. Until now, in the monomeric CDK2 structure, three binding sites have been reported, including the adenosine triphosphate (ATP) binding site (Site I) and two non-competitive binding sites (Site II and III). In addition, when the kinase is subjected to the cyclin binding process, the resulting structural changes give rise to a variation of the ATP binding site, thus generating an allosteric binding site (Site IV). All the four sites are demonstrated as being targeted by corresponding inhibitors, as is illustrated by the allosteric binding one which is targeted by inhibitor ANS (fluorophore 8-anilino-1-naphthalene sulfonate). In the present work, the binding mechanisms and their fluctuations during the activation process attract our attention. Therefore, we carry out corresponding studies on the structural characterization of CDK2, which are expected to facilitate the understanding of the molecular mechanisms of kinase proteins. Besides, the binding mechanisms of CDK2 with its relevant inhibitors, as well as the changes of binding mechanisms following conformational variations of CDK2, are summarized and compared. The summary of the conformational characteristics and ligand binding mechanisms of CDK2 in the present work will improve our understanding of the molecular mechanisms regulating the bioactivities of CDK2.

Synopsis on the linkage of Alzheimer's and Parkinson's disease with chronic diseases

Neurodegeneration is the progressive loss of neuronal structure and function, which ultimately leads to neurological disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis, and Huntington's disease. Even after the recent significant advances in neurobiology, the above-mentioned disorders continue to haunt the global population. Several studies have suggested the role of specific environmental and genetic risk factors associated with these disorders. However, the exact mechanism associated with the progression of these disorders still needs to be elucidated. In the recent years, sophisticated research has revealed interesting association of prominent neurodegenerative disorders such as AD and PD with chronic diseases such as cancer, diabetes, and cardiovascular diseases. Several common molecular mechanisms such as generation of free radicals, oxidative DNA damage, aberrations in mitochondrial DNA, and dysregulation of apoptosis have been highlighted as possible points of connection. The present review summarizes the possible mechanism of coexistence of AD and PD with other chronic diseases.

Mechanisms of resistance to BCR-ABL TKIs and the therapeutic strategies: A review

BCR-ABL caused by the translocation of t(9,22) with elevated tyrosine-kinase activity could induce leukemia in mice, which established BCR-ABL as the molecular pathogenic event in CML (Chronic myeloid leukemia). In recent years, a variety of tyrosine kinase inhibitors (TKIs) targeting at BCR-ABL specifically and effectively have been developed, which has fundamentally promoted the treatment of CML. However, the efficacy of TKIs was limited by its resistance induced by the development of kinase domain mutations and other mechanisms illustrated. In this review, we summarized BCR-ABL inhibitors approved by Food and Drug Administration (FAD), with the same concerns focus on the resistant mechanisms of BCR-ABL inhibitors and therapeutic resistant strategies.

Inhibit globally, act locally: CDK7 inhibitors in cancer therapy

Cyclin-dependent kinases (CDKs) are involved in temporal control of the cell cycle and transcription and play central roles in cancer development and metastasis. Recently, Kwiatkowski and colleagues identified a novel CDK7-specific inhibitor, THZ1, that hinders proliferation in cancer cell lines and dampens global transcription in T cell leukemia.

Flavopiridol synergizes with sorafenib to induce cytotoxicity and potentiate antitumorigenic activity in EGFR/HER-2 and mutant RAS/RAF breast cancer model systems

Oncogenic receptor tyrosine kinase (RTK) signaling through the Ras-Raf-Mek-Erk (Ras-MAPK) pathway is implicated in a wide array of carcinomas, including those of the breast. The cyclin-dependent kinases (CDKs) are implicated in regulating proliferative and survival signaling downstream of this pathway. Here, we show that CDK inhibitors exhibit an order of magnitude greater cytotoxic potency than a suite of inhibitors targeting RTK and Ras-MAPK signaling in cell lines representative of clinically recognized breast cancer (BC) subtypes. Drug combination studies show that the pan-CDK inhibitor, flavopiridol (FPD), synergistically potentiated cytotoxicity induced by the Raf inhibitor, sorafenib (SFN). This synergy was most pronounced at sub-EC50 SFN concentrations in MDA-MB-231 (KRAS-G13D and BRAF-G464V mutations), MDA-MB-468 [epidermal growth factor receptor (EGFR) overexpression], and SKBR3 [ErbB2/EGFR2 (HER-2) overexpression] cells but not in hormone-dependent MCF-7 and T47D cells. Potentiation of SFN cytotoxicity by FPD correlated with enhanced apoptosis, suppression of retinoblastoma (Rb) signaling, and reduced Mcl-1 expression. SFN and FPD were also tested in an MDA-MB-231 mammary fat pad engraftment model of tumorigenesis. Mice treated with both drugs exhibited reduced primary tumor growth rates and metastatic tumor load in the lungs compared to treatment with either drug alone, and this correlated with greater reductions in Rb signaling and Mcl-1 expression in resected tumors. These findings support the development of CDK and Raf co-targeting strategies in EGFR/HER-2-overexpressing or RAS/RAF mutant BCs.

Applications of NMR screening techniques to the pharmaceutical target Checkpoint kinase 1

Ligand screening techniques based on NMR spectroscopy are not as sensitive as other commonly used methods like fluorescence, radiolabeling and surface plasmon resonance. However, using modern NMR instrumentation, they can achieve reliable screening under near physiological condition using as little as 4.6 nmol of receptor and 100 nmol of ligand. Additionally, these NMR methods can also provide valuable and specific information on the ligand under investigation such as the dissociation constant KD, the binding epitope and most importantly some structural information on the actual conformation in the bound state. In this manuscript, we describe the use of NMR based screening techniques ("Saturation Transfer Difference" (STD) and "Water Ligand Observed via Gradient SpectroscopY" (WaterLOGSY)) to detect small therapeutic molecules that interact with the DNA damage checkpoint enzyme Checkpoint kinase 1 (Chk1). After the identification of the most potent ligand, we used specific NMR experiments to perform the epitope mapping of this ligand ("Group epitope mapping-STD" (GEM-STD), "Difference of Inversion REcovery rate with and without Target IrradiatiON" (DIRECTION)) and to characterize its bound conformation ("Transferred-Nuclear Overhauser Effect SpectroscopY" (tr-NOESY), "Transferred-Rotating frame Overhauser Effect SpectroscopY" (tr-ROESY)). Finally, we used molecular docking procedures to position the ligand within the active site of Chk1. On the experimental level, a comparison between NMR studies performed in a 90%H2O/10%D2O buffer and a 100% D2O buffer is also presented and discussed.

Synthesis of C-glycosyl pyrrolo[3,4-c]carbazole-1,3(2H,6H)-diones as a scaffold for check point kinase 1 inhibitors

Indolocarbazole natural products are known to possess a variety of biological activities that hold promise as cancer chemotherapeutic agents. We newly designed C-glycosyl pyrrolo[3,4-c]carbazole-1,3(2H,6H)-dione derivatives 7 and 8, which are natural-product-like scaffolds. Compounds 7 and 8 were stereoselectively and efficiently synthesized using β-selective C-allylation, Heck reaction, and thermal 6π-electron cyclization/oxidative aromatization. Their potential as Chk1 inhibitors was investigated, and 7 and 8 exhibited an inhibitory activity with IC50 values of 0.5-9.5 μM, which is good activity for scaffolds. The key intermediate 23 was obtained by five steps from d-ribose in 33% overall yield by this synthetic route, which would enable us to prepare a range of analogues in order to investigate further structure-activity relationship studies in the optimization process.

Phase I trial of the combination of flavopiridol and imatinib mesylate in patients with Bcr-Abl+ hematological malignancies

PURPOSE

Imatinib is an inhibitor of the Bcr-Abl tyrosine kinase; however, resistance is common. Flavopiridol, a cyclin-dependent kinase (CDK) inhibitor, down-regulates short-lived anti-apoptotic proteins via inhibition of transcription. In preclinical studies, flavopiridol synergizes with imatinib to induce apoptosis. We investigated this novel combination regimen in patients with Bcr-Abl(+) malignancies.

METHODS

In a phase I dose-escalation study, imatinib was administered orally daily, and flavopiridol by 1 h intravenous infusion weekly for 3 weeks every 4 weeks. Adults with chronic myelogenous leukemia or Philadelphia chromosome-positive acute leukemia were eligible. Patients were divided into two strata based on peripheral blood and bone marrow blast counts. The primary objective was to identify the recommended phase II doses for the combination. Correlative pharmacokinetic and pharmacodynamic studies were also performed.

RESULTS

A total of 21 patients received study treatment. Four dose levels were evaluated before the study was closed following the approval of the second-generation Bcr-Abl tyrosine kinase inhibitors (TKIs). Five patients responded, including four sustained responses. Four patients had stable disease. All but one responder, and all patients with stable disease had previously been treated with imatinib. One patient had a complete response sustained for 30 months. Changes in expression of phospho-Bcr/Abl, -Stat5, and Mcl-1 were monitored. No major pharmacokinetic interaction was observed.

CONCLUSIONS

This is the first study to evaluate the combination of a CDK inhibitor and a TKI in humans. The combination of flavopiridol and imatinib is tolerable and produces encouraging responses, including in some patients with imatinib-resistant disease.

Anticancer Activities and Mechanisms of Blumea balsamifera Extract in Hepatocellular Carcinoma Cells

Blumea balsamifera (also known as sambong), a medicinal plant, is known to improve physiological disorders such as rheumatism and hypertension. However, its anticancer activity has not been well elucidated. In this study, we found that Blumea balsamifera MeOH extract (BME) induced growth inhibitory activity in rat and human hepatocellular carcinoma cells (McA-RH7777, HepG2, respectively) without cytotoxicity as in with rat hepatocytes used as a normal cell model. BME induced cell cycle arrest at G1 phase via decreases in expression of cyclin-E and phosphorylation of retinoblastoma (Rb) protein in both dose- and time-dependent manners. Furthermore, BME reduced the level of a proliferation related ligand (APRIL) which stimulates tumor cell growth. The anti-proliferative effect of BME was improved slightly but significantly by the treatment with recombinant human APRIL. These findings suggest that BME may have a possible therapeutic potential in hepatoma cancer patients and the depletion of cellular APRIL may be one of the important mechanisms on the growth inhibitory effect of BME.

Synthesis and in vitro cytotoxic activity of chromenopyridones

Novel substituted chromenopyridones (3a-j and 6a-d) were synthesized and evaluated in vitro for the cytotoxic activity against various human cancer cell lines such as prostate (PC-3), breast (MCF-7), CNS (IMR-32), cervix (Hela), and liver (Hep-G2). preliminary cytotoxic screening showed that all the compounds possess a good to moderate inhibitory activity against various cancer cell lines. Particularly, compound 6b bearing allyl moiety displayed a significant cytotoxic potential in comparison to standard drugs.

Phase I trial of 7-hydroxystaurosporine and fludararbine phosphate: in vivo evidence of 7-hydroxystaurosporine induced apoptosis in chronic lymphocytic leukemia

This is a phase I study of 7-hydroxystaurosporine (UCN-01) and fludararbine monophosphate (FAMP) in relapsed lymphoma. UCN-01 alone was administered in cycle 1 and with FAMP in cycles 2-6. FAMP was escalated in cohorts from 1 to 5 days. UCN-01 and FAMP pharmacokinetics and apoptosis of malignant lymphocytes was evaluated. Eighteen patients were enrolled. Standard FAMP with UCN-01 was tolerated without dose-limiting toxicity (DLT) and those seen were common to either agent alone. One patient died due to Stevens-Johnson syndrome. Seven of 18 patients responded. No pharmacological effect of UCN-01 by FAMP was noted. Lymphocytosis occurred in 15 of 18 patients following UCN-01 to paradoxically increase circulating tumor cells. UCN-01 induced apoptosis in six of eight patients with chronic lymphocytic leukemia (CLL). UCN-01 does not increase FAMP toxicity. Transient lymphocytosis followed by apoptosis occurs with UCN-01. Mobilization from tissue reservoirs may play a role in the induction of cell death in malignant lymphocytes.

Targeting PML-RARα and Oncogenic Signaling Pathways by Chinese Herbal Mixture Tien-Hsien Liquid in Acute Promyelocytic Leukemia NB4 Cells

Tien-Hsien Liquid (THL) is a Chinese herbal mixture that has been used worldwide as complementary treatment for cancer patients in the past decade. Recently, THL has been shown to induce apoptosis in various types of solid tumor cells in vitro. However, the underlying molecular mechanisms have not yet been well elucidated. In this study, we explored the effects of THL on acute promyelocytic leukemia (APL) NB4 cells, which could be effectively treated by some traditional Chinese remedies containing arsenic trioxide. The results showed THL could induce G2/M arrest and apoptosis in NB4 cells. Accordingly, the decrease of cyclin A and B1 were observed in THL-treated cells. The THL-induced apoptosis was accompanied with caspase-3 activation and decrease of PML-RARα fusion protein. Moreover, DNA methyltransferase 1 and oncogenic signaling pathways such as Akt/mTOR, Stat3 and ERK were also down-regulated by THL. By using ethyl acetate extraction and silica gel chromatography, an active fraction of THL named as EAS5 was isolated. At about 0.5–1% of the dose of THL, EAS5 appeared to have most of THL-induced multiple molecular targeting effects in NB4 cells. Based on the findings of these multi-targeting effects, THL might be regarding as a complementary and alternative therapeutic agent for refractory APL.

Design, synthesis and SAR of thienopyridines as potent CHK1 inhibitors

A novel series of CHK1 inhibitors based on thienopyridine template has been designed and synthesized. These inhibitors maintain critical hydrogen bonding with the hinge and conserved water in the ATP binding site. Several compounds show single digit nanomolar CHK1 activities. Compound 70 shows excellent enzymatic activity of 1 nM.

A novel liposomal formulation of flavopiridol

Flavopiridol has shown promising activities in hematologic and solid tumor models, as well as in clinical trials in chronic lymphocytic leukemia patients. Flavopiridol has relatively low solubility and high plasma protein-binding. To address these issues and to provide an alternative strategy to achieve clinical efficacy, we encapsulated flavopiridol into a liposomal carrier and characterized its physicochemical and pharmacokinetic properties. The liposomes, comprising hydrogenated soy phosphatidylcholine (HSPC), cholesterol and poly (ethylene glycol) 2000-distearoyl phosphatidylethanolamine (PEG-DSPE), were prepared by polycarbonate membrane extrusion and then loaded with flavopiridol by a pH-gradient driven remote loading procedure. The liposomes had a mean diameter of 120.7 nm and a flavopiridol entrapment efficiency of 70.4%. Pharmacokinetic study in mice after i.v. bolus injection showed that the liposomal flavopiridol had an increased elimination phase half-life (T((1/2)beta), 339.7 min vs. 57.0 min), decreased clearance (CL, 0.012 L/min vs. 0.036 L/min), and increased area under the plasma concentration-time curve (AUC, 10.8 min micromol/L vs. 3.4 min micromol/L) compared to the free drug. This indicates a significant and potentially beneficial change in flavopiridol pharmacokinetics for the liposomal formulation. Further preclinical studies are warranted to define the toxicity and therapeutic efficacy of this novel formulation.

Mechanism of growth inhibitory effect of Blumea balsamifera extract in hepatocellular carcinoma

Blumea balsamifera is known to improve physiological disorders such as rheumatism and hypertension, but its anticancer activity has not been well elucidated. In this study, we found that Blumea balsamifera MeOH extract (BME) induced growth-inhibitory activity in rat and human hepatocellular carcinoma cells without cytotoxicity in rat hepatocytes which were used as a normal cell model. BME induced cell cycle arrest at the G1 phase via decreases in the expression of cyclin-E and phosphorylation of retinoblastoma protein. Furthermore, BME reduced the level of a proliferation-inducing ligand, that stimulates tumor cell growth. These findings suggest that BME has possible therapeutic potential in hepatoma cancer patients and that depletion of cellular APRIL is an important mechanism in the growth-inhibitory effect of BME.

Flavopiridol suppresses tumor necrosis factor-induced activation of activator protein-1, c-Jun N-terminal kinase, p38 mitogen-activated protein kinase (MAPK), p44/p42 MAPK, and Akt, inhibits expression of antiapoptotic gene products, and enhances apoptosis through cytochrome c release and caspase activation in human myeloid cells

Although flavopiridol, a semisynthetic flavone, was initially thought to be a specific inhibitor of cyclin-dependent kinases, it has now been shown that flavopiridol mediates antitumor responses through mechanism(s) yet to be defined. We have shown previously that flavopiridol abrogates tumor necrosis factor (TNF)-induced nuclear factor-kappaB (NF-kappaB) activation. In this report, we examined whether this flavone affects other cellular responses activated by TNF. TNF is a potent inducer of activator protein-1 (AP-1), and flavopiridol abrogated this activation in a dose- and time-dependent manner. Flavopiridol also suppressed AP-1 activation induced by various carcinogens and inflammatory stimuli. When examined for its effect on other signaling pathways, flavopiridol inhibited TNF-induced activation of various mitogen-activated protein kinases, including c-Jun NH(2)-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), and p44/p42 MAPK. It is noteworthy that this flavone also suppressed TNF-induced activation of Akt, a cell survival kinase, and expression of various antiapoptotic proteins, such as IAP-1, IAP-2, XIAP, Bcl-2, Bcl-xL, and TRAF-1. Flavopiridol also inhibited the TNF-induced induction of intercellular adhesion molecule-1, c-Myc, and c-Fos, all known to mediate tumorigenesis. Moreover, TNF-induced apoptosis was enhanced by flavopiridol through activation of the bid-cytochrome-caspase-9-caspase-3 pathway. Overall, our results clearly suggest that flavopiridol interferes with the TNF cell-signaling pathway, leading to suppression of antiapoptotic mechanisms and enhancement of apoptosis.

Aberrant kinase signaling: lessons from head and neck cancer

Cancers, including head and neck squamous cell carcinoma (HNSCC), are characterized by the increased expression of receptor and nonreceptor tyrosine kinases. Many small molecules have been developed that selectively inhibit these kinases. These drugs have demonstrated antitumor effects in many preclinical cancer models and are now either approved for use in selected cancer patients or are under active clinical development. Receptor tyrosine kinases can also be targeted using monoclonal antibodies. Cetuximab is a chimeric antibody that inhibits the epidermal growth factor receptor and was approved for use in HNSCC, making it the first new drug for the treatment of this malignancy in over 40 years. Serine/threonine kinases are also aberrantly expressed in HNSCC and inhibitors of these kinases are being developed for clinical use. These developments will allow for the rational design of treatment regimens for HNSCC patients based on the aberrant kinase signaling in their tumors.

Five years of progress on cyclin-dependent kinases and other cellular proteins as potential targets for antiviral drugs

In 1997-1998, the pharmacological cyclin-dependent kinase (CDK) inhibitors (PCIs) were independently discovered to inhibit replication of human cytomegalovirus, herpes simplex virus type 1 and HIV-1. The results from small clinical trials against cancer were then suggesting that PCIs could be safe enough to be used clinically. It was thus hypothesized that PCIs could have the potential to be developed as novel antivirals targeting cellular proteins. Consequently, Antiviral Chemistry & Chemotherapy published in 2001 the first review on the potential of CDKs, and cellular proteins in general, as potential targets for antivirals. The viral functions inhibited by PCIs, or their cellular targets, were then just starting to be characterized. The antiviral spectrum of PCIs and their effects on viral disease were still mostly untested. Even their actual specificity was not yet completely characterized. In addition, cellular proteins were not accepted as valid targets for antivirals. Significant progress has been made in the last 5 years in understanding the antiviral activities of PCIs and the potential roles of cellular proteins in general as targets for antivirals. The first clinical trials of the antiviral activities of PCIs and other inhibitors of cellular protein kinases have now been scheduled. Herein, we review the progress made since the publication of the first review on PCIs as potential antiviral drugs and on CDKs, and cellular proteins in general, as potential targets for antiviral drugs. We also highlight the major issues that still need to be addressed before PCIs or other drugs targeting cellular proteins can be developed as clinical antivirals.

Discovery of [4-Amino-2-(1-methanesulfonylpiperidin-4-ylamino)pyrimidin-5-yl](2,3-difluoro-6- methoxyphenyl)methanone (R547), a potent and selective cyclin-dependent kinase inhibitor with significant in vivo antitumor activity

The cyclin-dependent kinases (CDKs) and their cyclin partners are key regulators of the cell cycle. Since deregulation of CDKs is found with high frequency in many human cancer cells, pharmacological inhibition of CDKs with small molecules has the potential to provide an effective strategy for the treatment of cancer. The 2,4-diamino-5-ketopyrimidines 6 reported here represent a novel class of potent and ATP-competitive inhibitors that selectively target the cyclin-dependent kinase family. This diaminopyrimidine core with a substituted 4-piperidine moiety on the C2-amino position and 2-methoxybenzoyl at the C5 position has been identified as the critical structure responsible for the CDK inhibitory activity. Further optimization has led to a good number of analogues that show potent inhibitory activities against CDK1, CDK2, and CDK4 but are inactive against a large panel of serine/threonine and tyrosine kinases (K(i) > 10 microM). As one of these representative analogues, compound 39 (R547) has the best CDK inhibitory activities (K(i) = 0.001, 0.003, and 0.001 microM for CDK1, CDK2, and CDK4, respectively) and excellent in vitro cellular potency, inhibiting the growth of various human tumor cell lines including an HCT116 cell line (IC(50) = 0.08 microM). An X-ray crystal structure of 39 bound to CDK2 has been determined in this study, revealing a binding mode that is consistent with our SAR. Compound 39 demonstrates significant in vivo efficacy in the HCT116 human colorectal tumor xenograft model in nude mice with up to 95% tumor growth inhibition. On the basis of its superior overall profile, 39 was chosen for further evaluation and has progressed into Phase I clinical trial for the treatment of cancer.

Indolocarbazole natural products: occurrence, biosynthesis, and biological activity

The indolocarbazole family of natural products, including the biosynthetically related bisindolylmaleimides, is reviewed (with 316 references cited). The isolation of indolocarbazoles from natural sources and the biosynthesis of this class of compounds are thoroughly reviewed, including recent developments in molecular genetics, enzymology and metabolic engineering. The biological activities and underlying modes of action displayed by natural and synthetic indolocarbazoles is also presented, with an emphasis on the development of analogs that have entered clinical trials for its future use against cancer or other diseases.

Molecular targets and the treatment of myeloid leukemia

Leukemia is a multistep process involving accumulation of genetic alterations over time. These genetic mutations destroy the delicate balance between cell proliferation, differentiation, and apoptosis. Traditional approaches to treatment of leukemia involve chemotherapy, radiation, and bone marrow transplantation. In recent years, specific targeted therapies have been developed for the treatment of leukemia. The success of treatment of acute promyelocytic leukemia with All Trans Retinoic Acid (ATRA) and CML with imatinib have lead to increased efforts to identify targets that can be inhibited by small molecules for treatment of hematological malignancies. In this review, we describe the current advances in the development of targeted therapy in acute myeloid leukemia.

A new cancer diagnostic system based on a CDK profiling technology

A series of molecular pathological investigations of the molecules that stimulate the cyclin dependent kinases (CDK1, 2, 4, and 6) have led to enormous accumulation of knowledge of the clinical significance of these molecules for cancer diagnosis. However, the molecules have yet to be applied to clinical cancer diagnosis, as there is no available technology for application of the knowledge in a clinical setting. We hypothesized that the direct measurement of CDK activities and expressions (CDK profiling) might produce clinically relevant values for the diagnosis. This study investigated the clinical relevance of CDK profiling in gastrointestinal carcinoma tissues by using originally developed expression and activity analysis methods. We have established novel methods and an apparatus for analyzing the expression and activities of the CDK molecules in lysate of tumor tissue in a clinical setting, and examined 30 surgically dissected gastrointestinal carcinomas and corresponding normal mucosal specimens. We demonstrate here that remarkably elevated CDK2 activity is evident in more than 70% of carcinoma tissues. Moreover, a G1-CDK activity profiling accurately mirrored the differences in proliferation between tumor and normal colonic tissues. Our results suggest that CDK profiling is a potent molecular-clinical approach to complement the conventional pathological diagnosis, and to further assist in the individualized medications.

Common markers of proliferation

When normal tissue and tumour samples are compared by microarray analysis, the biggest differences most often occur in the expression levels of genes that control cell proliferation. However, this difference is detected whenever mRNA samples that are taken from two cell populations with different proliferation rates are compared. Although the exact genes that comprise this 'proliferation signature' often differ, they are almost always genes that are involved in the fundamental process of cell proliferation. Can the proliferation signature be used to improve our understanding of the cell cycle and cancer pathogenesis, as well as being used as a biomarker for cancer diagnosis and prognosis?

p21CDKN1A allows the repair of replication-mediated DNA double-strand breaks induced by topoisomerase I and is inactivated by the checkpoint kinase inhibitor 7-hydroxystaurosporine

This study provides evidence for the importance of p21(CDKN1A) for the repair of replication-mediated DNA double-strand breaks (DSBs) induced by topoisomerase I. We report that defects of p21(CDKN1A) and p53 enhance camptothecin-induced histone H2AX phosphorylation (gammaH2AX), a marker for DNA DSBs. In human colon carcinoma HCT116 cells with wild-type (wt) p53, gammaH2AX reverses after camptothecin removal. By contrast, gammaH2AX increases after camptothecin removal in HCT116 cells deficient for p53 (p53-/-) or p21(CDKN1A) (p21-/-) as the cells reach the late-S and G2 phases. Since p21-/- cells exhibit similar S-phase arrest as wt cells in response to camptothecin and aphidicolin does not abrogate the enhanced gammaH2AX formation in p21-/- cells, we conclude that enhanced gammaH2AX formation in p21-/- cells is not due to re-replication. The cell cycle checkpoint abrogator and Chk1/Chk2 inhibitor 7-hydroxystaurosporine (UCN-01) also increases camptothecin-induced gammaH2AX formation and inhibits camptothecin-induced p21(CDKN1A) upregulation in HCT116 wt cells. TUNEL (terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling) assays demonstrate that gammaH2AX formation in late S and G2 cells following CPT treatment corresponds to DNA breaks. However, these breaks are not related to apoptotic DNA fragmentation. We propose that p21(CDKN1A) prevents the collapse of replication forks damaged by stabilized topoisomerase I cleavage complexes.

Xanthones induce cell-cycle arrest and apoptosis in human colon cancer DLD-1 cells

We investigated the antiproliferative effects of four structurally similar prenylated xanthones, alpha-mangostin, beta-mangostin, gamma-mangostin, and methoxy-beta-mangostin, in human colon cancer DLD-1 cells. These xanthones differ in the number of hydroxyl and methoxy groups. Except for methoxy-beta-mangostin, the other three xanthones strongly inhibited cell growth at 20 microM and their antitumor efficacy was correlated with the number of hydroxyl groups. Hoechst 33342 nuclear staining and nucleosomal DNA-gel electrophoresis revealed that the antiproliferative effects of alpha- and gamma-mangostin, but not that of beta-mangostin, were associated with apoptosis. It was also shown that their antiproliferative effects were associated with cell-cycle arrest by affecting the expression of cyclins, cdc2, and p27; G1 arrest was by alpha-mangostin and beta-mangostin, and S arrest by gamma-mangostin. These findings provide a relevant basis for the development of xanthones as an agent for cancer prevention and combination therapy with anti-cancer drugs.

The survival kinases Akt and Pim as potential pharmacological targets

The Akt and Pim kinases are cytoplasmic serine/threonine kinases that control programmed cell death by phosphorylating substrates that regulate both apoptosis and cellular metabolism. The PI3K-dependent activation of the Akt kinases and the JAK/STAT-dependent induction of the Pim kinases are examples of partially overlapping survival kinase pathways. Pharmacological manipulation of such kinases could have a major impact on the treatment of a wide variety of human diseases including cancer, inflammatory disorders, and ischemic diseases.

Identification of a buried pocket for potent and selective inhibition of Chk1: prediction and verification

Inhibition of the Chk1 kinase by small molecules binding to its active site is a strategy of great therapeutic interest for oncology. We report how computational modelling predicted the binding mode of ligands of special interest to the Chk1 ATP site, for representatives of an indazole series and debromohymenialdisine. These binding modes were subsequently confirmed by X-ray crystallography. The binding mode of a potent indazole derivative involves non-conventional C-H...O and N-H...pi-aromatic interactions with the protein. These interactions are formed in a buried pocket at the periphery of the ATP-binding site, the importance of which has previously been overlooked for ligand design against Chk1. It is demonstrated that filling this pocket can confer ligands with dramatically enhanced affinity for Chk1. Structural arguments in conjunction with assay data explain why targeting this pocket is also advantageous for selective binding to Chk1. Structural overlays of known inhibitors complexed with Chk1 show that only the indazole series utilizes the pocket of interest. Therefore, the analysis presented here should prove helpful in guiding future structure-based ligand design efforts against Chk1.