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

STK214947, a novel indole alkaloids, inhibits HeLa and SK-HEP-1 cells survival and EMT process by blocking the Notch3 and Akt signals

Apoptosis and epithelial-to-mesenchymal transition (EMT) are closely associated with tumor survival and metastasis. These are the basic events in tumor occurrence and progression. STK214947 is an indole alkaloid with a skeleton that is similar to that of indirubin. Indole alkaloids have attracted considerable attention because of their antitumor activity. However, the relationship between STK214947 and these basic events remains unknown. In this study, the effects of STK214947 on inducing apoptosis and reversing the EMT process in tumor cells were confirmed. Mild concentrations of STK214947 inhibited tumor cell migration by reversing EMT and significantly regulated the expression of EMT-related proteins, including Notch3, E-cadherin, N-cadherin and vimentin. In addition, STK214947 in high concentration could induce apoptosis by down-regulating Notch3, p-Akt/Akt, and NF-κB, and upregulating Caspase 3. These findings support the further development of STK214947 as a potential antitumor small molecule that targets Notch3 and Akt signal transduction in cancer.

Lycopene Alleviates Chronic Stress-Induced Spleen Apoptosis and Immunosuppression via Inhibiting the Notch Signaling Pathway in Rats

Chronic stress induction in immunosuppression and splenocyte apoptosis is commonly associated with increased susceptibility to various diseases. Lycopene (LYC) is a member of the carotenoid family with immune restoration and anti-apoptotic function. However, little is known about the mechanisms underlying the protective roles of LYC against spleen injury induced by chronic stress. Herein, male Wistar rats were undergoing chronic restraint stress and/or administered LYC (10 mg/kg) for 21 days. The effective model establishment was validated by open-field tests and levels of corticosterone in serum. Histopathological staining observation displayed that LYC could reduce chronic stress-induced spleen structure damage. Furthermore, LYC treatment significantly reduced the number of apoptotic-positive splenocytes caused by chronic stress via the death receptor apoptotic pathway. We detected the interleukin 4 and interferon γ levels in serum and spleen to determine the ratio of Th1 and Th2 and found that LYC can alleviate the immunosuppression induced by chronic stress. Notably, western blot and real-time polymerase chain reaction indicated that LYC can reduce the expression of the Notch-pathway-related proteins and mRNA in rats exposed to chronic stress. Further study of the potential mechanisms by adding the Notch pathway inhibitor DAPT revealed that LYC alleviates the structure damage, apoptosis, and immunosuppression caused by chronic stress via the suppression of the Notch pathway. Overall, this study presents a strong rationale to target LYC as a treatment strategy to relieve chronic stress-induced spleen injury.

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.

Expression of CDK6 in Oral Squamous Cell Carcinomas

Background: CDK6 is the key factor in regulation of the cell cycle and essential for passage into the G1 phase. It also plays an important role in the development of various tumors. In this cross-sectional study expression of the CDK6 protein in oral squamous cell carcinoma (OSCC) and healthy oral mucosa of controls was assessed to determine relations with malignant transformation and clinicopathologic factors. Method: A total of 60 samples, 45 from OSCCs and 15 from healthy tissue, underwent immunohistochemistry for CDK6. Nuclear and cytoplasmic staining of keratinocytes was considered as positive and the percentages of positive cells were calculated. Results: Expression of CDK6 was detected in 55.6% of OSCC samples (25 cases) and 13.3% of controls (2 cases), the difference being significant. Mean percentage of CDK6 stained cells was 24.2±29.3 in the OSCC cases and 4.33±2.1 in the control group, again statistically significant. No relationship was detected between CDK6 expression and clinicopathologic factors. Conclusion: Overexpression of CDK6 observed in OSCC points to a role for this protein in oral carcinogenesis.

(E)-3-(Aryl(arylamino)Methylene)Indolin-2-One Derivatives: An Efficient Synthetic Approach and Evaluation of their Cancer Inhibitory Activity

A series of (E)-3-(aryl(arylamino)methylene)indolin-2-one derivatives were synthesised using an efficient synthetic approach. The method involved reaction of 3-bromo-3-(bromo(aryl)methyl)indolin-2-one with substituted anilines through nucleophilic substitution and a simultaneous elimination using NaHCO3 in DMF. The anticancer activity of the products against four cell lines, HCT-116, A549, SKOV3 and MDA-MB-231, was also evaluated, and several compounds showed moderate inhibitory activity.

Design, synthesis and biological evaluation of novel indolin-2-ones as potent anticancer compounds

The indolin-2-one core is a privileged structure for antitumor agents, especially kinase inhibitors. Twenty-three novel indolin-2-ones were designed by molecular dissection of the anticancer drug indirubin. Seventeen of them exhibited significant inhibition against the tested cell lines, and two of them (1c and 1h) showed IC₅₀ values at the submicromolar level against HCT-116 cells. Compounds 1c and 2c were also potent inhibitors of the triple-negative breast cancer (TNBC) cell line MDA-MB-231. Flow cytometry was utilized to explore the antitumor mechanism of 1c and 2c with MDA-MB-231 cells, and distinct effects were observed on 2c. Furthermore, immunocytochemical examination of 1c suggested a destabilization of microtubules, which was significantly different from the effect of IM, an indirubin derivative.

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.

Discovery of novel indirubin-3'-monoxime derivatives as potent inhibitors against CDK2 and CDK9

Indirubin-3'-monoxime (IM) is a potent cyclin-dependent kinase (CDK) inhibitor. Twenty novel IM derivatives were prepared to investigate the structure-activity relationships (SAR) of this compound class. Six compounds showed significant inhibition against both CDK2/cyclin E1 and CDK9/cyclin T1. The most potent compound 7t exhibited IC50 values at submicromolar level. Preliminary SAR trends were suggested and cytotoxicity of these compounds was investigated. Molecular docking studies on compounds 7l and 7t provided conducive clues for further structural optimization.

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.

Level of Notch activation determines the effect on growth and stem cell-like features in glioblastoma multiforme neurosphere cultures

BACKGROUND

Brain cancer stem-like cells (bCSC) are cancer cells with neural stem cell (NSC)-like properties found in glioblastoma multiforme (GBM) and they are assigned a central role in tumor initiation, progression and relapse. The Notch pathway is important for maintenance and cell fate decisions in the normal NSC population. Notch signaling is often deregulated in GBM and recent results suggest that this pathway plays a significant role in bCSC as well. We therefore wished to further elucidate the role of Notch activation in GBM-derived bCSC.

METHODS

Human-derived GBM xenograft cells were cultured as NSC-like neurosphere cultures. Notch modulation was accomplished either by blocking the pathway using the γ-secretase inhibitor DAPT or by activating it by transfecting the cells with the constitutive active Notch-1 receptor.

RESULTS

GBM neurosphere cultures with high endogenous Notch activation displayed sensitivity toward Notch inhibition with regard to tumorigenic features as demonstrated by increased G0/G1 population and reduced colony formation capacity. Of the NSC-like characteristics, only the primary sphere forming potential was affected, while no effect was observed on self-renewal or differentiation. In contrast, when Notch signaling was activated a decrease in the G0/G1 population and an enhanced capability of colony formation was observed, along with increased self-renewal and de-differentiation.

CONCLUSION

Based on the presented results we propose that active Notch signaling plays a role for cell growth and stem cell-like features in GBM neurosphere cultures and that Notch-targeted anti-bCSC treatment could be feasible for GBM patients with high endogenous Notch pathway activation.

Lentiviral-mediated gene silencing of Notch-4 inhibits in vitro proliferation and perineural invasion of ACC-M cells

Salivary adenoid cystic carcinoma (SACC) is a common type of salivary gland cancer. The poor long-term prognosis for patients with SACC is mainly due to local recurrence, perineural invasion (PNI) and distant metastasis. Notch signaling plays a critical role in determining cell fate such as proliferation, differentiation and apoptosis. Accumulating evidence indicates that aberrant Notch-4 expression has a tumor-promoting function in SACC. In the present study, we used lentiviral-mediated RNA interference (RNAi) targeted against Notch-4 to determine the effects of decreased levels of this protein in the human highly metastatic adenoid cystic carcinoma cell line ACC-M. Furthermore, the proliferative capability as well as the PNI potential of the treated cells were observed in vitro. Our studies demonstrated that RNAi directed against Notch-4 markedly decreased Notch-4 gene expression, resulting in the inhibition of cell proliferation, and G0/G1 to S phase arrest in ACC-M cells. Knockdown of Notch-4 also resulted in a decrease in the in vitro PNI activity in ACC-M cells. To conclude, RNAi targeting against Notch-4 induces the suppression of cell growth and inhibition of PNI in vitro in ACC-M cells. Notch-4 may play an important role in regulating proliferation and PNI activity of SACC.

Notch1 is a 5-fluorouracil resistant and poor survival marker in human esophagus squamous cell carcinomas

Notch signaling involves the processes that govern cell proliferation, cell fate decision, cell differentiation and stem cell maintenance. Due to its fundamental role in stem cells, it has been speculated during the recent years that Notch family may have critical functions in cancer stem cells or cancer cells with a stem cell phenotype, therefore playing an important role in the process of oncogenesis. In this study, expression of Notch family in KYSE70, KYSE140 and KYSE450 squamous esophageal cancer cell lines and virus transformed squamous esophageal epithelial cell line Het-1A was examined by quantitative RT-PCR. Compared to the Het-1A cells, higher levels of Nocth1 and Notch3 expression in the cancer cell lines were identified. Due to the finding that NOTCH3 mainly mediates squamous cell differentiation, NOTCH1 expression was further studied in these cell lines. By Western blot analyses, the KYSE70 cell line which derived from a poorly differentiated tumor highly expressed Notch1, and the Notch1 expression in this cell line was hypoxia inducible, while the KYSE450 cell line which derived from a well differentiated tumor was always negative for Notch1, even in hypoxia. Additional studies demonstrated that the KYSE70 cell line was more 5-FU resistant than the KYSE450 cell line and such 5-FU resistance is correlated to Notch1 expression verified by Notch1 knockdown experiments. In clinical samples, Notch1 protein expression was detected in the basal cells of human esophagus epithelia, and its expression in squamous cell carcinomas was significantly associated with higher pathological grade and shorter overall survival. We conclude that Notch1 expression is associated with cell aggressiveness and 5-FU drug resistance in human esophageal squamous cell carcinoma cell lines in vitro and is significantly associated with a poor survival in human esophageal squamous cell carcinomas.

Inhibition of Plk1 and Pin1 by 5'-nitro-indirubinoxime suppresses human lung cancer cells

A novel indirubin derivative, 5'-nitro-indirubinoxime (5'-NIO), exhibits a strong anti-cancer activity against human cancer cells. Here, the 5'-NIO-mediated G1 cell cycle arrest in lung cancer cells was associated with a decrease in protein levels of polo-like kinase 1 (Plk1) and peptidyl-prolyl cis/trans isomerase Pin1. Treatment with Plk1 siRNA or Pin1 inhibitor effectively inhibited the Rb phosphorylation, suggesting their regulatory role at G1 phase. In addition, the overexpression of Plk1 or Pin1 inhibited apoptotic signals following the cleavage of PARP in 5'-NIO-treated cells. These findings suggest that 5'-NIO have potential anti-cancer efficacy through the inhibition of Plk1 or/and Pin1 expression.

Inhibitory effect of curcumin on oral carcinoma CAL-27 cells via suppression of Notch-1 and NF-κB signaling pathways

Curcumin has been reported to inhibit cell growth and induce apoptosis in oral cancer cells. Although many studies have been done to uncover the mechanisms by which curcumin exerts its antitumor activity, the precise molecular mechanisms remain to be unclear. In the present study, we assessed the effects of curcumin on cell viability and apoptosis in oral cancer. For mechanistic studies, we used multiple cellular and molecular approaches such as gene transfection, real-time RT-PCR, Western blotting, invasion assay, and ELISA. For the first time, we found a significant reduction in cell viability in curcumin-treated cells, which was consistent with induction of apoptosis and also associated with down-regulation of Notch-1 and nuclear factor-κB (NF-κB). Taken together, we conclude that the down-regulation of Notch-1 by curcumin could be an effective approach, which will cause down-regulation of NF-κB, resulting in the inhibition of cell growth and invasion. These results suggest that antitumor activity of curcumin is mediated through a novel mechanism involving inactivation of Notch-1 and NF-κB signaling pathways.

5,5'-substituted indirubin-3'-oxime derivatives as potent cyclin-dependent kinase inhibitors with anticancer activity

To enhance the ability of indirubin derivatives to inhibit CDK2/cyclin E, a target of anticancer agents, we designed and synthesized a new series of indirubin-3'-oxime derivatives with combined substitutions at the 5 and 5' positions. A molecular docking study predicted the binding of derivatives with OH or halogen substitutions at the 5' position to the ATP binding site of CDK2, revealing the critical interactions that may explain the improved CDK2 inhibitory activity of these derivatives. Among the synthesized derivatives, the 5-nitro-5'-hydroxy analogue 3a and the 5-nitro-5'-fluoro analogue 5a displayed potent inhibitory activity against CDK2, with IC(50) values of 1.9 and 1.7 nM, respectively. These derivatives also showed antiproliferative activity against several human cancer cell lines, with IC(50) values of 0.2-3.3 microM. A representative analogue, 3a, showed greater than 500-fold selectivity for CDK relative to selected kinase panel and potent in vivo anticancer activity.