Induction of apoptosis by a novel indirubin-5-nitro-3′-monoxime, a CDK inhibitor, in human lung cancer cells

The Fundamental Role of Oxime and Oxime Ether Moieties in Improving the Physicochemical and Anticancer Properties of Structurally Diverse Scaffolds

The present review explores the critical role of oxime and oxime ether moieties in enhancing the physicochemical and anticancer properties of structurally diverse molecular frameworks. Specific examples are carefully selected to illustrate the distinct contributions of these functional groups to general strategies for molecular design, modulation of biological activities, computational modeling, and structure-activity relationship studies. An extensive literature search was conducted across three databases, including PubMed, Google Scholar, and Scifinder, enabling us to create one of the most comprehensive overviews of how oximes and oxime ethers impact antitumor activities within a wide range of structural frameworks. This search focused on various combinations of keywords or their synonyms, related to the anticancer activity of oximes and oxime ethers, structure-activity relationships, mechanism of action, as well as molecular dynamics and docking studies. Each article was evaluated based on its scientific merit and the depth of the study, resulting in 268 cited references and more than 336 illustrative chemical structures carefully selected to support this analysis. As many previous reviews focus on one subclass of this extensive family of compounds, this report represents one of the rare and fully comprehensive assessments of the anticancer potential of this group of molecules across diverse molecular scaffolds.

Substituent Orchestration in Dimethylquinoxaline Derivatives: A Tool for Fishing Out Appropriate CDK5 Inhibitors as Potential Therapeutics for Alzheimer's

A set of new heterocyclic analogs (Compounds I-IX), comprising of 6,7 dimethyl Quinoxalines were found to be active against the receptor GSK3β (Compounds IV-V) (Chem. Biodiversity 2021, 18, e2100364). In an effort to modulate effective CDK5 inhibitors herein our hypothesis underpinned to fish out an appropriate derivative from the same quinoxaline series, as these two targets GSK3β and CDK5 shared structural resemblance with each other. Aligned to the goal we have synthesized Compounds I-IX, characterized them using a combination of spectroscopic techniques and evaluated their activities against CDK5. Our analysis reflected that the adjacently located alkoxy/hydroxy functionality derivatives namely Compounds III and VI, to be the most potent (micromolar) amongst others in the series, backed by Density Functional Theory (DFT) calculations and molecular modelling studies. Also, the efficacy of the Compounds I-IX, were monitored in few other members of the CMGC family namely DYRK1A, CLK1and CK1δ that have been known to be directly involved in hyperphosphorylation of Tau. But unfortunately in none of the targets, our quinoxaline series were active. In a nut shell further optimisation of these intelligent nucleus, would not only lead to the discovery of novel pharmacophores, but also marked selectivity against a pool of kinases, thereby implementing a distinct roadmap towards the design of potential therapeutics against Alzheimer's.

Treatments for psoriasis: A journey from classical to advanced therapies. How far have we reached?

Psoriasis is considered an autoimmune, inflammatory disorder with a genetic basis. The underlying aetiology is yet unclear. Evidence suggests the congregation of immune cells and their secreted inflammatory cytokines, leukocytes, and other inflammation-promoting factors in large amounts within the epidermal layers of the skin, driving an inflammatory milieu. Although psoriasis is not a fatal condition, patients experience severe pain and suffering. It has a debilitating effect on the physiological and psychological state of the patient. Its distinguishing features are inflammation, formation of plaques on the skin and hyperproliferation of keratinocytes. Therapeutic strategies for treating psoriasis witnessed a radical improvement from traditional therapies to the approval of specific therapies like biologics and small molecules. The emerging evidence about new pharmacological targets and mechanisms in psoriasis has widened the scope for expanding therapeutic strategies. Our review discusses the existing treatments for plaque psoriasis and updates on therapies based on novel pharmacological targets in clinical development.

Anticancer potential of indirubins in medicinal chemistry: Biological activity, structural modification, and structure-activity relationship

Indirubin is the crucial ingredient of Danggui Longhui Wan and Qing-Dai, traditional Chinese medicine herbal formulas used for the therapy of chronic myelocytic leukemia in China for hundreds of years. Although the monomeric indirubin has been used in China for the treatment human chronic myelocytic leukemia. However, due to low water solubility, poor pharmacokinetic properties and low therapeutic effects are the major obstacle, and had significantly limited its clinical application. Consequently, the attractive anticancer profile of indirubin has enthused numerous researchers to discover novel indirubin derivatives with improved pharmacodynamic activity as well as good pharmacokinetic property. In this paper, we comprehensively review the recent progress of anticancer potential of indirubins, structural modification and structure-activity relationship, which may provide useful direction for the further development of novel indirubins with improved pharmacological profiles for the treatment of various types of cancer.

Inhibition of Cyclin-dependent Kinase (CDK) Decreased Survival of NB4 Leukemic Cells: Proposing a p53-Independent Sensitivity of Leukemic Cells to Multi-CDKs Inhibitor AT7519

An unbounded number of events exist beneath the intricacy of each particular hematologic malignancy, prompting the tumor cells into an unrestrained proliferation and invasion. Aberrant expression of cyclin-dependent kinases (CDKs) is one of these events which disrupts the regulation of cell cycle and subsequently, results in cancer progression. In this study, we surveyed the repressive impact of multi-CDK inhibitor AT7519 on a panel of leukemia-derived cell lines. Our data underlined that AT7519 abated the survival of all tested cells; however, in an overview, the response rate of leukemic cells to the inhibitor was varied irrespective of p53 status. Notably, the less sensitivity of leukemia cells to AT7519 was found to be mediated partly by the compensatory activation of c-Myc oncogene which was confirmed by the induction of a superior cytotoxicity upon its suppression in less sensitive cell. The blockage of cell cycle, as announced by induction of sub-G1 arrest as well as reduced S phase, resulted in a significant decrease in survival of acute promyelocytic leukemia (APL)-derived NB4 cells, as the most sensitive cell line, either as monotherapy or in combination with arsenic trioxide. Anti-leukemic effects of the inhibitor were further verified by apoptosis analysis, where we discovered that AT7519 induced apoptosis via alteration of pro- and anti-apoptotic genes in NB4. All in all, this study proposed that AT7519 is a rewarding agent opposed to APL; however, additional examinations should be performed to determine the advantages of this inhibitor in clinical setting.

Discovery of orally active indirubin-3'-oxime derivatives as potent type 1 FLT3 inhibitors for acute myeloid leukemia

FMS-like receptor tyrosine kinase-3 (FLT3) is expressed on acute leukemia cells and is implicated in the survival, proliferation and differentiation of hematopoietic cells in most acute myeloid leukemia (AML) patients. Despite recent achievements in the development of FLT3-targeted small-molecule drugs, there are still unmet medical needs related to kinase selectivity and the progression of some mutant forms of FLT3. Herein, we describe the discovery of novel orally available type 1 FLT3 inhibitors from structure-activity relationship (SAR) studies for the optimization of indirubin derivatives with biological and pharmacokinetic profiles as potential therapeutic agents for AML. The SAR exploration provided important structural insights into the key substituents for potent inhibitory activities of FLT3 and in MV4-11 cells. The profile of the most optimized inhibitor (36) showed IC₅₀ values of 0.87 and 0.32 nM against FLT3 and FLT3/D835Y, respectively, along with potent inhibition against MV4-11 and FLT3/D835Y expressed MOLM14 cells with a GI₅₀ value of 1.0 and 1.87 nM, respectively. With the high oral bioavailability of 42.6%, compound 36 displayed significant in vivo antitumor activity by oral administration of 20 mg/kg once daily dosing schedule for 21 days in a mouse xenograft model. The molecular docking study of 36 in the homology model of the DFG-in conformation of FLT3 resulted in a reasonable binding mode in type 1 kinases similar to the reported type 1 FLT3 inhibitors Crenolanib and Gilteritinib.

Natural-Based Indirubins Display Potent Cytotoxicity toward Wild-Type and T315I-Resistant Leukemia Cell Lines

Drug resistance in chronic myelogenous leukemia (CML) requires the development of new CML chemotherapeutic drugs. Indirubin, a well-known mutikinase inhibitor, is the major active component of "Danggui Longhui Wan", a Chinese traditional medicine used for the treatment of CML symptoms. An in-house collection of indirubin derivatives was screened at 1 μM on wild-type and imatinib-resistant T315I mutant CML cells. Herein are reported that only 15 analogues of the natural 6-bromoindirubin displayed potent cytotoxicity in the submicromolar range. Kinase assays in vitro show that eight out of the 15 active molecules strongly inhibited both c-Src and Abl oncogenic kinases in the nanomolar range. Most importantly, these eight molecules blocked the activity of T315I mutant Abl kinase at the submicromolar level and with analogue 22 exhibiting inhibitory activity at the low nanomolar range. Docking calculations suggested that active indirubins might inhibit T315I Abl kinase through an unprecedented binding to both active and Src-like inactive conformations. Analogue 22 is the first derivative of a natural product identified as an inhibitor of wild-type and imatinib-resistant T315I mutant Abl kinases.

Indirubin and Indirubin Derivatives for Counteracting Proliferative Diseases

Indirubin is the active component of Danggui Longhui Wan, a traditional Chinese medicine formulation. The encouraging clinical results from the 1980s obtained in chronic myelocytic leukemia patients treated with indirubin stimulated numerous studies on this compound. These investigations explored the use of indirubin in different types of cancer and reported the synthesis of novel derivatives with improved chemical and pharmacokinetic properties. In this paper, we review the impressive progress that has been made in elucidating the mechanistic understanding of how indirubin and its derivatives affect physiological and pathophysiological processes, mainly by inhibition of cell proliferation and induction of cell death. Furthermore, we survey the therapeutic use of these compounds in combating proliferative diseases such as cancer, restenosis, and psoriasis.

Enhancing effects of indirubin on the arsenic disulfide-induced apoptosis of human diffuse large B-cell lymphoma cells

The aim of the present study was to investigate the indirubin-enhanced effects of arsenic disulfide (As₂S₂) on the proliferation and apoptosis of diffuse large B-cell lymphoma (DLBCL) cells in order to identify an optimum combination therapy. The human DLBCL cells, LY1 and LY8, were treated with different concentrations of indirubin for 24, 48 and 72 h. Next, the cells were treated with 10 μM As₂S₂ or a combination of 10 μM As₂S₂ and 20 μM indirubin for 48 h. Cell proliferation inhibition was detected using cell counting kit-8 and cell apoptosis was determined using flow cytometry. The expression levels of Bcl-2, Bcl-2-associated X protein (Bax) and caspase-3 were analyzed by quantitative polymerase chain reaction (qPCR) and western blotting. The DLBCL cell viability exhibited no significant changes at 24, 48 or 72 h with increasing indirubin concentration. In addition, the apoptotic rates of the LY1 and LY8 cells demonstrated no noticeable effects at 48 h with increasing indirubin concentration. Following treatment with the combination of indirubin and As₂S₂, the inhibitory and apoptotic rates of the cells were notably increased compared with those of the As₂S₂-treated group. The qPCR results revealed that indirubin alone had no enhancing effect upon the Bax/Bcl-2 mRNA expression ratio and caspase-3 mRNA expression. Western blot analysis revealed that indirubin alone had an enhancing effect upon the Bax/Bcl-2 protein ratio and procaspase-3 protein expression. In addition, the results demonstrated that the 21-KDa Bax protein was proteolytically cleaved into an 18-KDa Bax in the DLBCL cells treated with the combination of indirubin and As₂S₂. Indirubin alone did not inhibit proliferation or induce the apoptosis of the LY1 and LY8 cells. However, the combination of indirubin and As₂S₂ yielded enhancing effects. Therefore, the results of the present study demonstrated that with regard to antitumor activities, As₂S₂ served as the principal drug, whereas indirubin served as the adjuvant drug. The enhancing effect was due, in part, to the induction of the mitochondrial apoptotic pathway, which involves the cleavage of Bax.

Regioselective Suzuki–Miyaura reactions of 4,7-dichloro-N-methylisatin. Synthesis, anti-HIV activity and modeling study

Suzuki–Miyaura reactions of 4,7-dichloro-N-methylisatin provide a convenient access to arylated methylisatins.

Application of a homogenous membrane potential assay to assess mitochondrial function

Decreases in mitochondrial membrane potential (MMP) have been associated with mitochondrial dysfunction that could lead to cell death. The MMP is generated by an electrochemical gradient via the mitochondrial electron transport chain coupled to a series of redox reactions. Measuring the MMP in living cells is commonly used to assess the effect of chemicals on mitochondrial function; decreases in MMP can be detected using lipophilic cationic fluorescent dyes. To identify an optimal dye for use in a high-throughput screening (HTS) format, we compared the ability of mitochondrial membrane potential sensor (Mito-MPS), 5,5',6,6'-tetrachloro-1,1',3,3' tetraethylbenzimidazolylcarbocyanine iodide, rhodamine 123, and tetramethylrhodamine to quantify a decrease in MMP in chemically exposed HepG2 cells cultured in 1,536-well plates. Under the conditions used, the optimal dye for this purpose is Mito-MPS. Next, we developed and optimized a homogenous cell-based Mito-MPS assay for use in 1,536-well plate format and demonstrated the utility of this assay by screening 1,280 compounds in the library of pharmacologically active compounds in HepG2 cells using a quantitative high-throughput screening platform. From the screening, we identified 14 compounds that disrupted the MMP, with half-maximal potencies ranging from 0.15 to 18 μM; among these, compound clusters that contained tyrphostin and 3'-substituted indolone analogs exhibited a structure-activity relationship. Our results demonstrate that this homogenous cell-based Mito-MPS assay can be used to evaluate the ability of large numbers of chemicals to decrease mitochondrial function.

Effect of indirubin-3-monoxime against lung cancer as evaluated by histological and transmission electron microscopic studies

The aim of this study is to evaluate the antitumor effect of indirubin-3-monoxime and its mode of action in benzo(α)pyrene [B(α)P] induced lung cancer in A/J mice. Light microscopic examination of lung sections of [B(α)P] induced lung cancer mice revealed the presence of adenocarcinoma characterized by extensive proliferation of alveolar epithelium and loss of alveolar spaces. The control lung tissue showed a normal architecture with clear alveolar spaces. Interestingly the indirubin-3-monoxime treated groups showed the reduced adenocarcinoma with appearance of alveolar spaces. Transmission Electron Microscopic (TEM) studies of lung sections of [B(α)P] induced lung cancer mice showed the presence of phaemorphic cells with dense granules and increased mitochondria. The lung sections of mice treated with indirubin-3-monoxime showed the presence of shrunken, fragmented, and condensed nuclei implying apoptosis. The effects were dose dependent and prominent in 10 mg/kg/5 d/week groups suggesting the therapeutic role of indirubin analogue against this deadly human malignancy. Here, our results indicate that indirubin-3-monoxime brings antitumor effect against [B(α)P] induced lung cancer by its apoptotic action in A/J mice.

A novel 7-azaisoindigo derivative-induced cancer cell apoptosis and mitochondrial dysfunction mediated by oxidative stress

This research focused on a novel 7-azaisoindigo derivative [namely N(1)-(n-butyl)-7-azaisoindigo, 7-AI-b], and investigated its molecular antitumor mechanism by exploring the means of cell death and the effects on mitochondrial function. 7-AI-b inhibited cancer cell proliferation in a dose- and time-dependent way. The morphological and nuclei changes in H(2) B-GFP-labeled HeLa cells were observed using a live cell system. The results suggested that cell death induced by 7-AI-b is closely related to apoptosis. 7-AI-b induced release of cytochrome C from mitochondria to cytosol and activation of caspase-3, showing that the apoptosis is mediated by the mitochondrial pathway. Furthermore, our data indicated that 7-AI-b triggers apoptosis through reactive oxygen species (ROS): cellular ROS levels were increased after 3 h exposure of 7-AI-b, which was reversed by the ROS scavenger N-acetyl-L-cysteine. As a consequence, 7-AI-b-mediated cell death, mitochondrial transmembrane potential collapse and ATP level were partly blocked by N-acetyl-L-cysteine. Further study showed that 7-AI-b could induce mitochondrial dysfunction: collapse of the mitochondrial transmembrane potential and reduction of intracellular ATP level. In summary, the novel synthesized 7-AI-b was demonstrated to be effective in killing cancer cells via an ROS-promoted and mitochondria- and caspase-dependent apoptotic pathway.

Inhibition of invasion and migration of salivary gland adenocarcinoma cells by 5'-nitro-indirubinoxime (5'-NIO)

BACKGROUND

5'-Nitro-indirubinoxime (5'-NIO) is a derivative of the bis-indole indirubin that exhibits anticancer activities. The present study investigated the anti-invasive action of 5'-NIO in salivary gland ductal adenocarcinoma, SGT cells.

METHODS

The wound-scratch, migration, and invasion assays were applied to determine the effect of 5'-NIO on the migration capacity and invasiveness of SGT cells. Reverse-transcriptase-polymerase chain reaction (RT-PCR) and Western blot were performed to evaluate the impacts of 5'-NIO on the expression of beta1 integrin and matrix metalloproteinases MMP-2 (gelatinase-A) and MMP-9 (gelatinase-B).

RESULTS

The viability of SGT cells was decreased by 5'-NIO in a dose-dependent manner, but not significant at the concentrations of 0.5 and 1 microM. Under the concentrations showing little cytotoxic effect, 5'-NIO exhibited a dose-dependent inhibitory effect on the invasion and migration of SGT cells. Furthermore, 5'-NIO suppressed the mRNA and protein expression of beta1 integrin and MMP-2 and MMP-9.

CONCLUSION

Taken together, these results suggest that 5'-NIO, even at low concentrations, may effectively inhibit the invasion and migration of SGT cells by suppressing beta1 integrin-mediated signaling.

5'-Nitro-indirubinoxime induces G1 cell cycle arrest and apoptosis in salivary gland adenocarcinoma cells through the inhibition of Notch-1 signaling

BACKGROUND

5'-Nitro-indirubinoxime (5'-NIO) is a new derivative of indirubin that exhibits anti-cancer activity in a variety of human cancer cells. However, its mechanism has not been fully clarified.

METHODS

Human salivary gland adenocarcinoma (SGT) cells were used in this study. Western blot and RT-PCR analyses were performed to determine cellular Notch levels. The cell cycle stage and level of apoptosis were analyzed using flow cytometry analysis.

RESULTS

5'-NIO significantly inhibited the mRNA levels of Notch-1 and Notch-3 and their ligands (Delta1, 2, 3, and Jagged-2) in SGT cells. Immunocytochemistry analysis showed that 5'-NIO specifically decreased the level of Notch-1 in the nucleus. In addition, 5'-NIO induced G1 cell cycle arrest by reducing levels of CDK4 and CDK6 in SGT cells. Using flow cytometry and immunoblotting analysis, we found that 5'-NIO induces apoptosis following the secretion of cytochrome c and the activation of caspase-3 and caspase-7. Intracellular Notch-1 overexpression led to a decrease in G1 phase arrest and an inhibition of 5'-NIO-induced apoptosis.

CONCLUSION

These observations suggest that 5'-NIO induces cell cycle arrest and apoptosis by down-regulating Notch-1 signaling.

GENERAL SIGNIFICANCE

This study identifies a new mechanism of 5'-NIO-mediated anti-tumor properties. Thus, 5'-NIO could be used as a candidate for salivary gland adenocarcinoma therapeutics.

Anti-inflammatory effects of the extract of indigo naturalis in human neutrophils

ETHNOPHARMACOLOGICAL RELEVANCE

Indigo naturalis is used by traditional Chinese medicine to treat various inflammatory diseases.

AIM OF THE STUDY

Topical indigo naturalis ointment showed efficacy in treating psoriasis in our previous clinical studies. In this study, we investigated the anti-inflammatory effects of the extract of indigo naturalis (QD) and its main components indirubin, indigo, and tryptanthrin in human neutrophils.

MATERIALS AND METHODS

Superoxide anion (O2(.-)) generation and elastase release were measured by spectrophotometry. Some important signals including mitogen-activated protein kinase (MAPK), cAMP, and calcium were studied by Western blot analysis, an enzyme immunoassay, and spectrofluorometry.

RESULTS

QD significantly inhibited O2(.-) generation and elastase release in formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP)-activated human neutrophils in a concentration-dependent fashion, while neither indirubin, indigo, nor tryptanthrin produced a comparable result. QD attenuated the FMLP-induced phosphorylation of extracellular regulated kinase, p38 MAPK, and c-Jun N-terminal kinase. Furthermore, QD inhibited calcium mobilization caused by FMLP. However, QD did not affect cellular cAMP levels. On the other hand, neither indirubin, indigo, nor tryptanthrin produced similar changes in human neutrophils.

CONCLUSIONS

Taken collectively, these findings indicate that QD, but not indirubin, indigo, or tryptanthrin, inhibited O2(.-) generation and elastase release in FMLP-induced human neutrophils, which was at least partially mediated by the inhibition of MAPK activation and regulation of calcium mobilization.

Indirubin-3'-oxime impairs mitochondrial oxidative phosphorylation and prevents mitochondrial permeability transition induction

Indirubin, a red colored 3,2'-bisindole isomer, is a component of Indigo naturalis and is an active ingredient used in traditional Chinese medicine for the treatment of chronic diseases. The family of indirubin derivatives, such as indirubin-3'-oxime, has been suggested for various therapeutic indications. However, potential toxic interactions such as indirubin effects on mitochondrial bioenergetics are still unknown. This study evaluated the action of indirubin-3'-oxime on the function of isolated rat liver mitochondria contributing to a better understanding of the biochemical mechanisms underlying the multiple effects of indirubin. Indirubin-3'-oxime incubated with isolated rat liver mitochondria, at concentrations above 10microM, significantly depresses the phosphorylation efficiency of mitochondria as inferred from the decrease in the respiratory control and ADP/O ratios, the perturbations in mitochondrial membrane potential and in the phosphorylative cycle induced by ADP. Furthermore, indirubin-3'-oxime at up to 25microM stimulates the rate of state 4 respiration and inhibits state 3 respiration. The increased lag phase of repolarization was associated with a direct inhibition of the mitochondrial ATPase. Indirubin-3'-oxime significantly inhibited the activity of complex II and IV thus explaining the decreased FCCP-stimulated mitochondrial respiration. Mitochondria pre-incubated with indirubin-3'-oxime exhibits decreased susceptibility to calcium-induced mitochondrial permeability transition. This work shows for the first time multiple effects of indirubin-3'-oxime on mitochondrial bioenergetics thus indicating a potential mechanism for indirubin-3'-oxime effects on cell function.

Apigenin causes G(2)/M arrest associated with the modulation of p21(Cip1) and Cdc2 and activates p53-dependent apoptosis pathway in human breast cancer SK-BR-3 cells

We studied the effects of apigenin on the cell cycle distribution and apoptosis of human breast cancer cells and explored the mechanisms underlying these effects. We first investigated the antiproliferative effects in SK-BR-3 cells exposed to between 1 and 100 microM apigenin for 24, 48 and 72 h. Apigenin significantly inhibited cell proliferation at concentrations over 50 microM, regardless of exposure time (P<.05), and resulted in significant cell cycle arrest in the G(2)/M phase after 48 h of treatment at high concentrations (50 and 100 microM; P<.05). To investigate the regulatory proteins of cell cycle arrest affected by apigenin, we treated cells with 50 and 100 microM apigenin for 72 h. Apigenin caused a slight decrease in cyclin D and cyclin E expression, with no change in CDK2 and CDK4. In addition, the apigenin-induced accumulation of the cell population in the G(2)/M phase resulted in a decrease in CDK1 together with cyclin A and cyclin B. In an additional study, apigenin also increased the accumulation of p53 and further enhanced the level of p21(Cip1), with no change in p27(Kip1). The expression of Bax and cytochrome c of p53 downstream target was increased markedly at high concentration treatment over 50 microM apigenin. Based on our findings, the mechanism by which apigenin causes cell cycle arrest via the regulation of CDK1 and p21(Cip1) and induction of apoptosis seems to be involved in the p53-dependent pathway.

Expanding the chemical diversity of CK2 inhibitors

None of the already described CK2 inhibitors did fulfill the requirements for successful clinical settings. In order to find innovative CK2 inhibitors based on new scaffolds, we have performed a high-throughput screening of diverse chemical libraries. We report here the identification and characterization of several classes of new inhibitors. Whereas some share characteristics of previously known CK2 inhibitors, others are chemically unrelated and may represent new opportunities for the development of better CK2 inhibitors. By combining structure-activity relationships with a docking procedure, we were able to determine the binding mode of these inhibitors. Interestingly, beside the identification of several nanomolar ATP-competitive inhibitors, one class of chemical inhibitors displays a non-ATP competitive mode of inhibition, a feature that suggests that CK2 possess distinct druggable binding sites. For the most promising inhibitors, selectivity profiling was performed. We also provide evidence that some chemical compounds are inhibiting CK2 in living cells. Finally, the collected data allowed us to draw the rules about the chemical requirements for CK2 inhibition both in vitro and in a cellular context.

The Efficacy and Safety of Topically Applied Indigo Naturalis Ointment in Patients with Plaque-Type Psoriasis

BACKGROUND

It has been reported in the Chinese literature that indigo naturalis exhibits potential antipsoriatic effects in systemic therapy.

OBJECTIVE

To evaluate the efficacy and safety of topically applied indigo naturalis on treating plaque-type psoriasis and to analyze the histological change in skin tissues.

METHODS

Fourteen patients with chronic plaque psoriasis were enrolled. The patients were topically applied with either indigo naturalis ointment or vehicle ointment on contralateral skin lesions daily for 8 weeks. Efficacy was evaluated on the basis of the clinical scores, including induration, scaling, erythema and clearing percentage. At the end of treatment, skin punch biopsies were taken and prepared for the immunohistochemical analysis.

RESULTS

A significant reduction in clinical scores was achieved with topically applied indigo naturalis ointment. Analysis of biopsies showed a marked improvement of skin histology. The expressions of proliferating marker Ki-67 and inflammatory marker CD3 were decreased, but the differentiation marker such as filaggrin was increased in the epidermis after indigo naturalis ointment treatment.

CONCLUSIONS

The results suggest that topical application of indigo naturalis ointment may be a novel, safe and effective therapy for psoriasis that is mediated, at least in part, by modulating the proliferation and differentiation of keratinocytes in epidermis, as well as by inhibiting the infiltration of T lymphocytes and therefore the subsequent inflammatory reactions in psoriatic lesions.

Antitumor Activity of Novel Indirubin Derivatives in Rat Tumor Model

PURPOSE

The novel indirubin derivatives 5'-nitro-indirubinoxime, 5'-fluoro-indirubinoxime, and 5'-trimethylacetamino-indirubinoxime were designed and tested for antitumor activity both in vitro and in vivo using rat tumor model.

EXPERIMENTAL DESIGN

Three-week-old male Sprague-Dawley rats were inoculated s.c. on the left flank with 10(7) RK3E-ras rat kidney epithelial cells harboring k-ras gene. Alternatively, 5 x 10(6) RK3E-ras cells were injected into the oral mucosa. Indirubin derivative treatment began on the 3rd or 6th day after oral or s.c. cell injection, respectively. Indirubin derivatives were directly injected into the tumor every other day for a total of five times. Animals were monitored daily and tumor volume was measured by caliper.

RESULTS

Indirubin derivatives showed potent antiproliferative activity on various human cancer cells and oncogenic RK3E-ras rat kidney cells, with IC(50) ranging from 1 to 12 mumol/L. Treatment with indirubin derivatives induced the activation of caspase-7 followed by apoptosis in RK3E-ras cells. Indirubin derivatives showed strong antitumor activity in rat solid and oral tumor models. Direct injection of indirubin derivatives every other day for 10 days induced significant inhibition of tumor growth in Sprague-Dawley rats bearing RK3E-ras-induced tumors. Histologically, treatment with indirubin derivatives caused significant inhibition of tumor formation with increased apoptosis and decreased tumor cell proliferation.

CONCLUSIONS

Our data showed that novel indirubin derivatives 5'-nitro-indirubinoxime, 5'-fluoro-indirubinoxime, and 5'-trimethylacetamino-indirubinoxime effectively arrested the tumor growth by inhibiting cell proliferation and inducing apoptosis. These findings provide the potential value of indirubin derivatives as novel candidates for antitumor agents.

Indirubin enhances tumor necrosis factor-induced apoptosis through modulation of nuclear factor-kappa B signaling pathway

Although indirubin is known to exhibit anti-cancer and anti-inflammatory activities, very little is known about its mechanism of action. In this study, we investigated whether indirubin mediates its effects through interference with the NF-kappaB pathway. As examined by the DNA binding of NF-kappaB, we found that indirubin suppressed tumor necrosis factor (TNF)-induced NF-kappaB activation in a dose- and time-dependent manner. Indirubin also suppressed the NF-kappaB activation induced by various inflammatory agents and carcinogens. Further studies showed that indirubin blocked the phosphorylation and degradation of IkappaB alpha through the inhibition of activation of IkappaB alpha kinase and phosphorylation and nuclear translocation of p65. NF-kappaB reporter activity induced by TNFR1, TNF receptor-associated death domain, TRAF2, TAK1, NF-kappaB-inducing kinase, and IKKbeta was inhibited by indirubin but not that induced by p65 transfection. We also found that indirubin inhibited the expression of NF-kappaB-regulated gene products involved in antiapoptosis (IAP1, IAP2, Bcl-2, Bcl-xL, and TRAF1), proliferation (cyclin D1 and c-Myc), and invasion (COX-2 and MMP-9). This correlated with enhancement of the apoptosis induced by TNF and the chemotherapeutic agent taxol in human leukemic KBM-5 cells. Indirubin also suppressed cytokine-induced cellular invasion. Overall, our results indicate that anti-cancer and anti-inflammatory activities previously assigned to indirubin may be mediated in part through the suppression of the NF-kappaB activation pathway.

7-Bromoindirubin-3'-oxime induces caspase-independent cell death

Indirubin, an isomer of indigo, is a reported inhibitor of cyclin-dependent kinases (CDKs) and glycogen synthase kinase-3 (GSK-3) as well as an agonist of the aryl hydrocarbon receptor (AhR). Indirubin is the active ingredient of a traditional Chinese medicinal recipe used against chronic myelocytic leukemia. Numerous indirubin analogs have been synthesized to optimize this promising kinase inhibitor scaffold. We report here on the cellular effects of 7-bromoindirubin-3'-oxime (7BIO). In contrast to its 5-bromo- and 6-bromo- isomers, and to indirubin-3'-oxime, 7BIO has only a marginal inhibitory activity towards CDKs and GSK-3. Unexpectedly, 7BIO triggers a rapid cell death process distinct from apoptosis. 7-Bromoindirubin-3'-oxime induces the appearance of large pycnotic nuclei, without classical features of apoptosis such as chromatin condensation and nuclear fragmentation. 7-Bromoindirubin-3'-oxime-induced cell death is not accompanied by cytochrome c release neither by any measurable effector caspase activation. Furthermore, the death process is not altered either by the presence of Q-VD-OPh, a broad-spectrum caspase inhibitor, or the overexpression of Bcl-2 and Bcl-XL proteins. Neither AhR nor p53 is required during 7BIO-induced cell death. Thus, in contrast to previously described indirubins, 7BIO triggers the activation of non-apoptotic cell death, possibly through necroptosis or autophagy. Although their molecular targets remain to be identified, 7-substituted indirubins may constitute a new class of potential antitumor compounds that would retain their activity in cells refractory to apoptosis.

Synthesis and structure-activity relationships of novel indirubin derivatives as potent anti-proliferative agents with CDK2 inhibitory activities

Indirubin, an active ingredient of a traditional Chinese recipe Danggui Longhui Wan, has been known as a CDK inhibitor competing with ATP for binding to the catalytic site of cyclin-dependent kinases (CDKs). Since CDKs, a group of serine/threonine kinases forming active heterodimeric complexes with cyclins, are key regulators of the cell cycle regulation, therapeutic interventions targeting CDKs have been stimulated for the treatment of proliferative diseases, such as cancer, psoriasis, and for the prevention of chemotherapy-associated side effects, such as alopecia. A series of novel indirubin analogs was synthesized and evaluated for anti-proliferative and CDK2 inhibitory activities. Among the indirubin derivatives tested in the growth inhibitions against several human cancer cell lines, 5-nitro, halide, and bulky group containing acylamino substituted analogs showed high anti-proliferative effects. Selected analogs showing potent anti-proliferative activities were evaluated further in the CDK2 enzyme assay, which resulted in the discovery of potent CDK2 inhibitors.