Linjiang Tong

Philinopside a, a novel marine‐derived compound possessing dual anti‐angiogenic and anti‐tumor effects

Philinopside A is a novel sulfated saponin isolated from the sea cucumber, Pentacta quadrangulari. The effects of philinopside A on angiogenesis and tumor growth were assessed in a series of models in vitro and in vivo. Our results demonstrated that philinopside A significantly inhibited the proliferation, migration and tube formation of human microvascular endothelial cells (HMECs) in a dose‐dependent manner, with average IC50 values of 1.4 ± 0.17, 0.89 ± 0.23 and 0.98 ± 0.19 μM, respectively. Rat aortas culture assay provides a close imitation of in vivo angiogenesis process and 2–10 μM philinopside A suppressed the formation of new microvessels in cultured rat aortas. Philinopside A 2–10 nmol/egg obviously inhibited angiogenesis in chick embryo chorioallantoic membrane assay. In addition, philinopside A manifested strong anti‐tumor activities both in vitro and in vivo. Through immunofluorescent analysis, we found the compound reduced mouse sarcoma 180 tumor volume by inducing apoptosis of tumor and tumor‐associated endothelial cells. An examination of the effects of philinopside A on the angiogenesis‐related receptor tyrosine kinases (RTKs) showed that philinopside A broadly inhibited all tested RTKs, including vascular endothelial growth factor (VEGF) receptor, fibroblast growth factor (FGF) receptor‐1, platelet‐derived growth factor (PDGF) receptor‐β and epithelial growth factor (EGF) receptor, with IC50 values ranging from 2.6–4.9 μM. These results suggest that philinopside A is a promising anti‐cancer agent that possesses dual cytotoxic and anti‐angiogenic effects that were at least partly due to its inhibitory effects on RTKs.

Dihydroartemisinin induces apoptosis in HL-60 leukemia cells dependent of iron and p38 mitogen-activated protein kinase activation but independent of reactive oxygen species

Dihydroartemisinin (DHA), the main active metabolite of artemisinin derivatives, is one of the most effective anti-malarial analogs of artemisinin. In the current study, we found that DHA inhibited the proliferation of a panel of tumor cells originated from different tissue types. DHA effectively induced apoptosis in human promyelocytic leukemia HL-60 cells, which was accompanied with mitochondrial dysfunction and caspases activation. Further studies indicated that DHA-induced apoptosis was iron-dependent. Though DHA slightly elicited superoxide anion, these reactive oxygen species (ROS) contribute little to DHA-induced apoptosis in HL-60 cells. Moreover, DHA time-dependently activated mitogen-activeted protein kinases (MAPKs) and specific inhibition of p38 MAPK, but not c-Jun-NH2-terminal kinase (JNK) or extracellular signal-regulated kinase (ERK), abolished DHA-induced apoptosis, indicating that activation of p38 MAPK is required for DHA-induced apoptosis in HL-60 cells. Altogether, our data uncover that DHA induces apoptosis is dependent of iron and p38 MAPK activation but not ROS in HL-60 cells.

Naturally occurring homoisoflavonoids function as potent protein tyrosine kinase inhibitors by c-Src-based high-throughput screening

Protein tyrosine kinase (PTK) inhibitors represent emerging therapeutics for cancer chemoprevention. In our study, hematoxylin (26) was identified as one of the most remarkable c-Src inhibitors in an orthogonal compound-mixing library (32200 compounds) by using an ELISA-based automated high-throughput screening (HTS) strategy. Interestingly, hematoxylin was found to be an ATP competitive broad-spectrum PTK inhibitor in vitro, with IC50 values ranging from nanomolar to micromolar level. Further studies showed that such inhibition was associated with the PTK phosphorylation and subsequent downstream signaling pathways. The structure-activity relationship assessment of the PTK inhibitory potency of hematoxylin analogues isolated from Heamatoxylon campechianum was in good agreement with the result of concurrent molecular docking simulation: the catechol moiety in ring A and the hematoxylin-like three-dimensional structure were essential for c-Src-targeted activities. Hematoxylin and its natural analogues were substantially validated to function as a new class of PTK inhibitors.

The discovery of colchicine-SAHA hybrids as a new class of antitumor agents.

A novel class of colchicine-SAHA hybrids were designed and synthesised based on the synergistic antitumor effect of tubulin inhibitors and histone deacetylases (HDAC) inhibitors. To the best of our knowledge, this is the first design of molecules that are dual inhibitors of tubulin and HDAC. Biological evaluations of these compounds included the inhibitory activity of HDAC, in vitro cell cycle analysis in BEL-7402 cells as well as cytotoxicity in five cancer cell lines.

Acenaphtho[1,2-b]pyrrole-based selective fibroblast growth factor receptors 1 (FGFR1) inhibitors: design, synthesis, and biological activity.

A novel series of acenaphtho[1,2-b]pyrrole derivatives as potent and selective inhibitors of fibroblast growth factor receptor 1 (FGFR1) were designed and synthesized. In silico target prediction revealed that tyrosine kinases might be the potential targets of the representative compound 2, which was subsequently validated by enzyme-linked immunosorbent assay (ELISA) for its selective and active FGFR1 inhibition of various tyrosine kinases. The structure-activity relationship (SAR) analysis aided by molecular docking simulation in the ATP-binding site demonstrated that acenaphtho[1,2-b]pyrrole carboxylic acid esters (2-5) are potent inhibitors of FGFR1 with IC(50) values ranging from 19 to 77 nM. Furthermore, these compounds exhibited favorable growth inhibition property against FGFR-expressing cancer cell lines with IC(50) values ranging from micromolar to submicromolar. Western blotting analysis showed that compounds 2, 3, and 2b inhibited activation of FGFR1 and extracellular-signal regulated kinase 1/2 (Erk1/2).

BM6, a New Semi-Synthetic Vinca Alkaloid, Exhibits Its Potent In Vivo Anti-Tumor Activities Via its High Binding Affinity for Tubulin and Improved Pharmacokinetic Profiles

The aim of this study was to evaluate the anti-tumor activities and to establish the mechanism of the action of 3-decarboxyl-acetyloxylmethyl-anhydrovinblastine (BM6), a new semi-synthetic Vinca alkaloid, in an effort towards finding the favorable therapeutics of Vinca alkaloid derivatives. BM6 was characterized by its superior in vivo activity to vinorelbine in preclinical tumor models, though BM6 exerted in vitro cytotoxic activity against a wide spectrum of tumor cell lines with IC50 values generally 10-fold higher than the classic Vinca alkaloids. Of note, BM6 displayed more potent cytotoxic activity against multidrug-resistant sublines. We further found that BM6 shared the mitotic arresting and tubulin-interacting properties comparable with other Vinca alkaloids. BM6 also induced significant cell cycle arrested in mitosis and cytoskeleton disruption via interacting with the Vinca binding site on tubulin. Encouragingly, the features in term of its higher tubulin binding affinities and better pharmacokinetic profiles highlight BM6 distinct from other Vinca alkaloids, which help provide more data for exploiting new semi-synthetic Vinca alkaloids.

Discovery and SAR of Thiazolidine-2,4-dione Analogues as Insulin-like Growth Factor-1 Receptor (IGF-1R) Inhibitors via Hierarchical Virtual Screening

Insulin-like growth factor-1 receptor (IGF-1R) is a growth factor receptor tyrosine kinase acting as a critical mediator of cell proliferation and survival. Novel 5-benzylidenethiazolidine-2,4-dione (5) and 5-(furan-2-ylmethylene)thiazolidine-2,4-dione (6) compounds were identified as potent and selective IGF-1R inhibitors via hierarchical virtual screening. Initial SAR and biological activity of the analogues of 5 and 6 with thiazolidine-2,4-dione template are presented, and several inhibitors with low nanomolar potency are reported.

AST1306, A Novel Irreversible Inhibitor of the Epidermal Growth Factor Receptor 1 and 2, Exhibits Antitumor Activity Both In Vitro and In Vivo

Despite the initial response to the reversible, ATP-competitive quinazoline inhibitors that target ErbB-family, such a subset of cancer patients almost invariably develop resistance. Recent studies have provided compelling evidence that irreversible ErbB inhibitors have the potential to override this resistance. Here, we found that AST1306, a novel anilino-quinazoline compound, inhibited the enzymatic activities of wild-type epidermal growth factor receptor (EGFR) and ErbB2 as well as EGFR resistant mutant in both cell-free and cell-based systems. Importantly, AST1306 functions as an irreversible inhibitor, most likely through covalent interaction with Cys797 and Cys805 in the catalytic domains of EGFR and ErbB2, respectively. Further studies showed that AST1306 inactivated pathways downstream of these receptors and thereby inhibited the proliferation of a panel of cancer cell lines. Although the activities of EGFR and ErbB2 were similarly sensitive to AST1306, ErbB2-overexpressing cell lines consistently exhibited more sensitivity to AST1306 antiproliferative effects. Consistent with this, knockdown of ErbB2, but not EGFR, decreased the sensitivity of SK-OV-3 cells to AST1306. In vivo, AST1306 potently suppressed tumor growth in ErbB2-overexpressing adenocarcinoma xenograft and FVB-2/Nneu transgenic breast cancer mouse models, but weakly inhibited the growth of EGFR-overexpressing tumor xenografts. Tumor growth inhibition induced by a single dose of AST1306 in the SK-OV-3 xenograft model was accompanied by a rapid (within 2 h) and sustained (≥24 h) inhibition of both EGFR and ErbB2, consistent with an irreversible inhibition mechanism. Taken together, these results establish AST1306 as a selective, irreversible ErbB2 and EGFR inhibitor whose growth-inhibitory effects are more potent in ErbB2-overexpressing cells.

WJD008, a dual phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin inhibitor, prevents PI3K signaling and inhibits the proliferation of transformed cells with oncogenic PI3K mutant.

The phosphatidylinositol-3-kinase (PI3K)-protein kinase B (Akt)-mammalian target of rapamycin (mTOR) signaling pathway is often constitutively activated in various human cancers, providing validated targets for cancer therapy. Among a series of 5-cyano-6-morpholino-4-substituted-pyrimidine analogs designed and synthesized based on PI3K target, 4-(2-(dimethylamino)vinyl)-2-(3-hydroxyphenyl)-6-morpholinopyrimidine-5-carbonitrile (WJD008) was selected for further pharmacological characterization because of its potent activity against PI3K signaling. WJD008 inhibited kinase activity of PI3Kα and mTOR with less activity against PIKK family members. In cellular settings, WJD008 abrogated insulin-like growth factor-I-activated PI3K-Akt-mTOR signaling cascade and blocked the membrane translocation of a pleckstrin homology domain containing enhanced green fluorescent protein-general receptor for phosphoinositides, isoform 1-pleckstrin homology fusion protein, suggesting down-regulation of phosphatidylinositol (3,4,5)-trisphosphate output induced by WJD008 resulted in inactivation of PI3K pathway. Consequently, WJD008 arrested cells in G1 phase without induction of apoptosis. Furthermore, WJD008 reversed the hyperactivation of the PI3K pathway caused by the oncogenic mutation of p110α H1047R and suppressed the proliferation and clonogenesis of transformed RK3E cells harboring this mutant. WJD008 was superior to the pan-PI3K inhibitor wortmannin against proliferation of a panel of cancer cells independently of their status of PI3K pathway or tissue originations. In summary, WJD008 is a potent dual PI3K/mTOR modulator with antiproliferative and anticlonogenic activity in tumor cells and transformed cells with PIK3CA mutant, which provides new clues for the design and development of this chemical scaffold as an anticancer drug.

The marine-derived oligosaccharide sulfate (MdOS), a novel multiple tyrosine kinase inhibitor, combats tumor angiogenesis both in vitro and in vivo.

Despite the emerging success of multi-targeted protein tyrosine kinase (PTK) inhibitors in cancer therapy, significant side effects and resistance concerns seems to be avoided unlikely. The aim of the present study was to identify novel multi-targeting PTK inhibitors. The kinase enzymatic activities were measured by enzyme-linked immunosorbent assay (ELISA). The antiproliferative activities in human microvascular endothelial cells (HMECs) were evaluated by sulforhodamine (SRB) assay. The phosphorylation of kinases and their downstream molecules was probed by western blot analysis. The binding mode between MdOS and PTKs was profiled by surface plasmon resonance (SPR) approach and molecular simulation. Tube formation assay, rat aortic ring method and chicken chorioallantoic membrane assay were combined to illustrate the in vitro and in vivo anti-angiogenic effects. Results indicated that MdOS, a novel marine-derived oligosaccharide sulfate, exhibited a broad-spectrum PTK inhibitory action. At an enzymatic level, MdOS inhibited HER2, EGFR, VEGFR, PDGFR, c-Kit, FGFR1 and c-Src, with little impact on FGFR2. In cellular settings, MdOS inhibited phosphorylation of PTKs, exemplified by HER2, EGFR and VEGFR2, and downstream molecules of Erk1/2 and AKT. Further studies demonstrated that MdOS acted as an ATP-competitive inhibitor via directly binding to the residues of entrance rather than those of the ATP-binding pocket. Furthermore, MdOS inhibited proliferation and tube formation of HMECs, arrested microvessel outgrowth of rat aortic rings and hindered the neovascularization of chick allantoic membrane. Taken together, results presented here indicated that MdOS exhibited anti-angiogenic activity in a PTK-dependent manner and make it a promising agent for further evaluation in PTK-associated cancer therapy.