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The ubiquitin-proteasome system (UPS) is a complex process that regulates protein stability and activity by the sequential actions of E1, E2 and E3 enzymes to influence diverse aspects of eukaryotic cells. However, due to the diversity of proteins in cells, substrate selection is a highly critical part of the process. As a key player in UPS, E3 ubiquitin ligases recruit substrates for ubiquitination specifically. Among them, RING E3 ubiquitin ligases which are the most abundant E3 ubiquitin ligases contribute to diverse cellular processes. The multisubunit cullin-RING ligases (CRLs) are the largest family of RING E3 ubiquitin ligases with tremendous plasticity in substrate specificity and regulate a vast array of cellular functions. The F-box protein Skp2 is a component of CRL1 (the prototype of CRLs) which is expressed in many tissues and participates in multiple cellular functions such as cell proliferation, metabolism, and tumorigenesis by contributing to the ubiquitination and subsequent degradation of several specific tumor suppressors. Most importantly, Skp2 plays a pivotal role in a plethora of cancer-associated signaling pathways. It enhances cell growth, accelerates cell cycle progression, promotes migration and invasion, and inhibits cell apoptosis among others. Hence, targeting Skp2 may represent a novel and attractive strategy for the treatment of different human cancers overexpressing this oncogene. In this review article, we summarized the known roles of Skp2 both in health and disease states in relation to the UPS.

Dual target compounds have become a hot spot in the treatment of cancer in recent years. Histone lysine specific demethylase 1 (LSD1) is identified as histone demethylase and acts as a key regulator involved in many other cellular activities through its demethylation function. We have reported a triazolo [1,5-α] pyrimidine-based DCN1(defective in cullin neddylation protein 1) inhibitor compound 383 (IC

Interleukin 33 (IL33) has been found to be cardioprotective on various cardiovascular pathologies. However, it is not clear whether IL33 may inhibit myocardial infarction-related ventricular remodeling through inducing macrophage polarization. The objective of present study is to assess whether IL33 can improve ventricular remodeling after myocardial infarction by inducing macrophage polarization. In this study, the direct influence of IL33 on the polarization of macrophages and its mechanism in vitro were investigated. The potential protective effects of IL33 on acute and chronic myocardial infarction (MI) in vivo as well as its underlying mechanism through macrophage polarization were also determined. We found that IL33 significantly enhanced M2 macrophage and decreased the proportion of M1 macrophage. Importantly, IL33 induced M2 macrophage polarization by activating the JAK/STAT signaling pathway. In vivo, IL33 weaken the inflammatory level and myocardial apoptosis after MI and improved the systolic and diastolic function of the heart. Furthermore, IL33 significantly reduced infarct area and prevented the progression of fibrosis by inducing M2 macrophage polarization. The protective effects of IL33 were suppressed by JAK/STAT signaling pathway inhibitor. Our findings highlighted that IL33 not only reduced the early inflammatory response and inhibited myocardial apoptosis, but also increased the number of M2 macrophage in the infarcted area, significantly reduced infarct area and prevented the progression of fibrosis by activating JAK/STAT pathway. Therefore, IL33 may be a novel cardiac protective cytokine for myocardial infarction.

EGFR tyrosine kinase inhibitor (EGFR-TKI) has been used successfully in clinic for the treatment of solid tumors. In the present study, we reported the discovery of WS-157 from our in-house diverse compound library, which was validated to be a potent and selective EGFR-TKI. WS-157 showed excellent inhibitory activities against EGFR (IC50 = 0.81 nmol/L), EGFR[d746−750] (IC50 = 1.2 nmol/L) and EGFR[L858R] (IC50 = 1.1 nmol/L), but was less effective or even inactive against other nine kinases. WS-157 also displayed excellent antiproliferative activities against a panel of human cancer cell lines, and exhibited the ability to reduce colony formation and wound healing the same as gefitinib. We found that WS-157 upon oral administration showed better anti-tumor activity in A431 bearing xenograft mouse models compared to gefitinib. In addition, WS-157 showed better intestinal absorption than gefitinib and had favorable pharmacokinetic properties and microsomal metabolic stability in different species. These studies indicate that WS-157 has strong antitumor activity in vitro and in vivo, and could be used for the development of anti-lung cancer agent targeting EGFR., Graphical abstract WS-157 identified from our in-house diverse compound library was fully characterized as a potent and selective EGFR-TKI. WS-157 showed excellent inhibitory activities against EGFR (IC50 = 0.81 nmol/L), EGFR[d746−750] (IC50 = 1.2 nmol/L) and EGFR[L858R] (IC50 = 1.1 nmol/L), good in vivo antitumor activity and acceptable pharmacokinetic properties.Image 1

Abnormal epigenetics is a critical hallmark of human cancers. Anticancer drug discovery directed at histone epigenetic modulators has gained impressive advances with six drugs available for cancer therapy and numerous other candidates undergoing clinical trials. However, limited therapeutic profile, drug resistance, narrow safety margin, and dose-limiting toxicities pose intractable challenges for their clinical utility. Because histone epigenetic modulators undergo intricate crosstalk and act cooperatively to shape an aberrant epigenetic profile, co-targeting histone epigenetic modulators with a different mechanism of action has rapidly emerged as an attractive strategy to overcome the limitations faced by the single-target epigenetic inhibitors. In this review, we summarize in detail the crosstalk of histone epigenetic modulators in regulating gene transcription and the progress of dual epigenetic inhibitors targeting this crosstalk.

Targeting mitochondria using proper pharmacological agents is considered an attractive strategy for cancer control and management. Herein, we report a newly synthetic triazole analog of Jaridonin, DN3, which exhibits more potent antitumor activity via acting directly on mitochondria. DN3 potently reduced viabilities of gastric cancer cell lines HGC-27 and MGC-803 through inducing apoptosis and cell cycle arrest. But, normal human gastric epithelial cell line GES-1 is more resistant to the growth inhibition by DN3 compared with gastric cancer cells. DN3 induced mitochondrial membrane potential (MMP) decrease and cytochrome c release in intact gastric cancer cell lines. Meanwhile, the DN3 treatment also caused the release of cytochrome c from mitochondria isolated from cancer cell lines in a mitochondrial permeability transition pore complex (PTPC) mediated manner, but not from mitochondria isolated from normal gastric epithelial cell. The induction of mitochondrial PTPC proteins voltage-dependent anion channel (VDAC) and cyclophilin D (CypD) were also observed in DN3-treated cells. More interestingly, DN3 mediated MMP decrease, release of cytochrome c, the expression of VDAC and CypD and apoptosis were blocked by the pretreatment of VDAC1 inhibitor (4, 4′-diisothiocyanatostilbene-2,2′-disulfonic acid, DIDS) and CypD inhibitor (cyclosporine A, CsA). In a mouse xenograft model of human gastric cancer, the treatment of 5 mg/kg DN3 led to significant tumor regression without affecting body weight. In conclusion, our findings indicate that DN3 is a potential agent for the treatment of gastric cancer through acting directly on mitochondria, and would be useful for us to design more and better anti-cancer compounds.

In this work, a novel series of tofacitinib analogs were designed and synthesized based on the scaffold hybridization strategy and then evaluated for their antiproliferative activity toward three gastric cancer cell lines, leading to the identification of compound C18 which exhibited potent inhibitory activity against MGC-803 cell lines with an IC50 value of 2.68 μM. Compound C18 could effectively inhibit the colony formation, suppress the cell migration and induce apoptosis of MGC-803 cells through activating the p38 and JNK signaling pathways, while C18 showed no obvious effect on the cell cycle distribution in MGC-803 cells. In addition, C18 could initiate mitochondrial dysfunction of MGC-803 cells. Besides, in vivo antitumor studies indicated that C18 could inhibit gastric cancer tumor growth in vivo without obvious global toxicity.

PI3K/Akt/mTOR signaling pathway plays a vital role in regulating cell survival, differentiation, metabolism and migration, which is frequently hyperactive in a number of cancers, including esophageal squamous cell carcinoma (ESCC). As the core subunit of mTORC2, Rictor is shown to be amplified in ESCC patients' tissues and plays an important role in regulation of Akt. The objective of this study is to evaluate the effects of Rictor knockdown on cell sensitivity to PI3K inhibitor LY294002 in ESCC cells and ESCC xenografts as well as its mechanisms. We found LY294002 obviously restrained cell proliferation in dose-dependent and time-dependent manners by inhibiting PI3K/Akt/mTOR/p70S6K signaling pathway, whereas triggered mTORC2-medicated phosphorylation of Akt (Ser473)/PRAS40 (Thr246) in ECa109 and EC9706 cells. Stable knockdown of Rictor by shRNA enhanced the inhibitory effects of LY294002 on cell proliferative, migration and colony formation, as well as promoted its effects on cell cycle arrest and cell apoptosis in vitro. Furthermore, stable knockdown of Rictor enhanced the antitumor effects of LY294002 by inhibiting tumor growth and promoting cell apoptosis in vivo. Mechanistic assay revealed that knockdown of Rictor could attenuate LY294002-induced phosphorylation of Akt (Ser473)/PRAS40 (Thr246). Our results provide rationale that combined inhibition of Rictor/mTORC2 and PI3K for the treatment of ESCC.

Histone lysine-specific demethylase 1 (LSD1) is the first discovered and reported histone demethylase by Dr. Shi Yang's group in 2004. It is classified as a member of amine oxidase superfamily, the common feature of which is using the flavin adenine dinucleotide (FAD) as its cofactor. Since it is located in cell nucleus and acts as a histone methylation eraser, LSD1 specifically removes mono- or dimethylated histone H3 lysine 4 (H3K4) and H3 lysine 9 (H3K9) through formaldehyde-generating oxidation. It has been indicated that LSD1 and its downstream targets are involved in a wide range of biological courses, including embryonic development and tumor-cell growth and metastasis. LSD1 has been reported to be overexpressed in variety of tumors. Inactivating LSD1 or downregulating its expression inhibits cancer-cell development. LSD1 targeting inhibitors may represent a new insight in anticancer drug discovery. This review summarizes recent studies about LSD1 and mainly focuses on the basic physiological function of LSD1 and its involved mechanisms in pathophysiologic conditions, as well as the development of LSD1 inhibitors as potential anticancer therapeutic agents.

Jaridon 6, a novel ent-kaurene diterpenoid derived from Rabdosia rubescens (Hemsl.) Hara, possesses strong anti-tumor activity in esophageal cancer cells. In this study, we explored the underlying molecular events of the anti-tumor activity of Jaridon 6. Cell viability and apoptosis results obtained by flow cytometry confirmed the tumor inhibitory effect of Jaridon 6 in esophageal cancer cells. A cDNA microarray was performed and the observations were validated using quantitative reverse transcription polymerase chain reaction. The microarray data showed that 151 genes were differentially expressed between the untreated group and the Jaridon 6-treated group, among these were 57 upregulated genes, and 94 downregulated genes (P < 0.01, fold change threshold: 2). These included genes such as Wnt, peroxisome, and genes involved in chemokine signaling pathways. In addition, Western blot analysis demonstrated that Jaridon 6 regulated the expression of Wnt pathway proteins, including reduced levels of Dvl 2, survivin and cyclin D1, and increased levels of p-β-catenin, and AXIN2 in EC109 and EC9706 esophageal cancer cells. In addition, recombinant murine Wnt3a could change the regulation of Jaridon 6 on Wnt pathway proteins. Immunohistochemical analysis indicated that the anti-tumor activity of Jaridon 6 was closely related to the Wnt signaling pathway in esophageal cancer cells.

A novel [1,2,4] triazolo [1,5-a] pyrimidine-based phenyl-linked steroid dimer was designed, synthesized and evaluated for its cytotoxic activity against five human cancer cell lines and the cytotoxicity against human normal liver cell L-02. Compound 3 showed excellent cytotoxic activity and good selectivity between cancer and normal cells. Further mechanistic studies revealed that treatment of EC109 cells with compound 3 caused an obvious G2/M arrest in a concentration- and time-dependent manner and induced apoptosis probably through the mitochondrial pathway accompanied with the decrease of mitochondrial membrane potential, activations of caspase-9/-3, cleavage of MDM2 as well as up-regulation of the expressions of p53 and Bax.

The stereoselective and metal-free protocol involving a cascade aldol/cyclization process for the synthesis of steroidal (E, E) dienamides from steroidal α, α-dicyanoalkene was reported. This protocol efficiently achieved the construction of C C bond and selective conversion of cyano group into carboxamide in one-pot procedure under mild condition. Further biological evaluation showed that some of these compounds had moderate to excellent cytotoxic activities against all the tested cancer cell lines and were more potent than well-known drug 5-fluorouracil. Particularly, compound 3c represented excellent inhibitory effect against MCF-7 (IC50 = 0.76 μM), which was about 10-fold more potent than 5-fluorouracil.

A series of novel 1,2,3-triazole-dithiocarbamate hybrids were designed, synthesized and evaluated for anticancer activity against four selected human tumor cell lines (MGC-803, MCF-7, PC-3, EC-109). Majority of the synthesized compounds exhibited moderate to potent activity against MGC-803 and MCF-7. Among them, compounds 3a and 3c showed excellent broad spectrum anticancer activity with IC50 values ranging from 0.73 to 11.61 μM and 0.49-12.45 μM, respectively. Particularly, compound 3a was more potent than 5-fluorouracil against all tested human cancer cell lines. Flow cytometry analysis demonstrated that treatment of MGC-803 with 3c led to cell cycle arrest at G2/M phase accompanied by an increase in apoptotic cell death after 12 h.

The utility of natural products for identifying anticancer agents has been highly pursued in the last decades and over 100 drug molecules in clinic are natural products or natural product-derived compounds. Natural products are believed to be able to cover unexplored chemical space that is normally not occupied by commercially available molecule libraries. However, the low abundance and synthetic intractability of natural products have limited their applications in drug discovery. Recently, the identification of biologically relevant fragments derived from biologically validated natural products has been recognized as a powerful strategy in searching new biological probes and drugs. The spirocyclic oxindoles, as privileged structural scaffolds, have shown their potential in designing new drugs. Several anticancer drug candidates such as SAR405838, RO8994, CFI-400945 and their bioisosteres are undergoing clinical trials or preclinical studies. To highlight the significant progress, we focus on illustrating the discovery of SAR405838, RO8994, CFI-400945 and their bioisosteres for cancer therapy using substructure-based strategies and discussing modes of action, binding models and preclinical data.

A series of novel steroidal spirooxindoles 3a-h were synthesized from pregnenolone in a high regioselective manner using the 1,3-dipolar cycloaddition as the key step. This protocol resulted in the formation of two C-C bonds, one C-N bond and the creation of one pyrrolidine ring and three contiguous stereocenters in a single operation. Biological evaluation showed that these synthesized steroidal spirooxindoles exhibited moderate to good antiproliferative activity against the tested cell lines and some of them were more potent than 5-FU. Among them, compounds 3e and 3f displayed the best antiproliferative activity against MCF-7 cells with the IC50 values of 4.0 and 3.9μM, respectively. Flow cytometry analysis demonstrated that compound 3d caused the cellular apoptosis and cell cycle arrest at G2/M phase in a concentration-dependent manner. Docking results indicated that compound 3d fitted well into the MDM2 active site 1RV1 by interacting with Lys94 and Thr101 residues.

Jaridonin, a novel diterpenoid from Isodon rubescens, has been shown previously to inhibit proliferation of esophageal squamous cancer cells (ESCC) through G2/M phase cell cycle arrest. However, the involved mechanism is not fully understood. In this study, we found that the cell cycle arrest by Jaridonin was associated with the increased expression of phosphorylation of ATM at Ser1981 and Cdc2 at Tyr15. Jaridonin also resulted in enhanced phosphorylation of Cdc25C via the activation of checkpoint kinases Chk1 and Chk2, as well as in increased phospho-H2A.X (Ser139), which is known to be phosphorylated by ATM in response to DNA damage. Furthermore, Jaridonin-mediated alterations in cell cycle arrest were significantly attenuated in the presence of NAC, implicating the involvement of ROS in Jaridonin's effects. On the other hand, addition of ATM inhibitors reversed Jaridonin-related activation of ATM and Chk1/2 as well as phosphorylation of Cdc25C, Cdc2 and H2A.X and G2/M phase arrest. In conclusion, these findings identified that Jaridonin-induced cell cycle arrest in human esophageal cancer cells is associated with ROS-mediated activation of ATM–Chk1/2–Cdc25C pathway.

A series of novel steroidal pyran–oxindole hybrids were efficiently synthesized in a single operation through the vinylogous aldol reaction of vinyl malononitrile 3 with substituted isatins involving the construction of C–C and C–O bonds. Some compounds displayed moderate to good cytotoxicity against T24, SMMC-7721, MCF-7 and MGC-803 cells. Compounds 4f and 4i were more potent than 5-Fu against T24 and MGC-803 cells with the IC50 values of 4.43 and 8.45 μM, respectively. Further mechanism studies indicated that compound 4i induced G2/M arrest and early apoptosis in a concentration- and time-dependent manner.

Two series of more available novel 1,2,3-triazole-Jaspine B hybrids were efficiently synthesized employing click chemistry approach and evaluated for their cytotoxic activities against three human cancer cell lines (EC-9706, MGC-803 and MCF-7). Among them, compound 14h showed excellent inhibition against MCF-7 (IC 50 = 1.93 μM) and was more potent than 5-Fu and Jaspine B against all three cancer cell lines. Further investigation of apoptosis assay and cell cycle analysis demonstrated that compound 14h caused cellular early and late apoptosis and arrested the cell cycle at G2/M phase in a concentration- and time-independent manner. This was the first report about the synthesis and in vitro cytotoxic evaluation of 1,2,3-triazole-Jaspine B hybrids.

Two series of steroidal dienamides 4aeq and 5aef were designed, synthesized and evaluated for cytotoxic activities against five human cancer cell lines (MGC-803, EC109, PC-3, SMMC-7721 and MCF-7). The protocol developed efficiently achieved the construction of carbonecarbon double bond and selective conversion of nitrile group into carboxamide in one-pot procedure. Besides, compounds 4aeq and 5aef showed moderate to excellent cytotoxic activities with the IC50 values ranging from 0.1 to 40 mM and most of them were more potent than 5-fluorouracil. Particularly, four compounds 4d, 4e, 4q and 5a showed excellent selectivity against MGC-803 with the IC50 values less than 1 mM. Flow cytometry analysis demonstrated that compound 4c caused the cellular early apoptosis and cell cycle arrest in G2/M phase in a concentration-independent manner.

The application of doxorubicin (DOX), a well-known antitumor drug, is limited due to its cumulative cardiotoxicity. Up to now, no effective prevention is available for its side effect. It has been shown that peroxiredoxin II (Prx II) protects cardiomyocytes from oxidative stress-induced injury and

Isodon rubescens, a Chinese herb, has been used as a folk, botanical medicine in China for inflammatory diseases and cancer treatment for many years. Recently, we isolated a new ent-kaurene diterpenoid, named Jaridonin, from Isodon rubescens. The chemical structure of Jaridonin was verified by infrared (IR), nuclear magnetic resonance (NMR), and mass spectrum (MS) data as well as X-ray spectra. Jaridonin potently reduced viabilities of several esophageal cancer cell lines, including EC109, EC9706 and EC1. Jaridonin treatment resulted in typical apoptotic morphological characteristics, increased the number of annexin V-positive staining cells, as well as caused a G2/M arrest in cell cycle progression. Furthermore, Jaridonin resulted in a significant loss of mitochondrial membrane potential, release of cytochrome c into the cytosol, and then activation of Caspase-9 and -3, leading to activation of the mitochondria mediated apoptosis. Furthermore, these effects of Jaridonin were accompanied by marked reactive oxygen species (ROS) production and increased expression of p53, p21(waf1/Cip1) and Bax, whereas two ROS scavengers, N-acetyl-L-cysteine (LNAC) and Vitamin C, significantly attenuated the effects of Jaridonin on the mitochondrial membrane potential, DNA damage, expression of p53 and p21(waf1/Cip1) and reduction of cell viabilities. Taken together, our results suggest that a natural ent-kaurenoid diterpenoid, Jaridonin, is a novel apoptosis inducer and deserves further investigation as a new chemotherapeutic strategy for patients with esophageal cancer.