Gaozhi Chen

Small molecule inhibition of fibroblast growth factor receptors in cancer

Fibroblast growth factors (FGFs) signal through FGF receptors (FGFRs), which are a sub-family of the superfamily of receptor tyrosine kinases, to regulate human development and metabolism. Uncontrolled FGF signaling is responsible for diverse array of developmental disorders, most notably skeletal syndromes due to FGFR gain-of-function mutations. Studies in the last few years have provided significant evidence for the importance of FGF signaling in the pathogenesis of diverse cancers, including endometrial and bladder cancers. FGFs are both potent mitogenic and angiogenic factors and can contribute to carcinogenesis by stimulating cell proliferation and tumor angiogenesis. Gene knockout and pharmacological inhibition of FGFRs in in vivo and in vitro models validate FGFRs as a target for cancer treatment. Considerable efforts are being expended to develop specific, small-molecule inhibitors for treating FGFR-driven cancers. Recent reviews on the FGF/FGFR system have focused primarily on signaling, pathophysiology, and functions in cancer. In this article, we review the key roles of FGFR in cancer, provide an update on the status of clinical trials with small-molecule FGFR inhibitors, and discuss how the current structural data on FGFR kinases guide the design and characterization of new FGFR inhibitors.

Synthesis and Anti-inflammatory Evaluation of Novel Benzimidazole and Imidazopyridine Derivatives.

Sepsis, an acute inflammatory disease, remains the most common cause of death in intensive care units. A series of benzimidazole and imidazopyridine derivatives were synthesized and screened for anti-inflammatory activities, and the imidazopyridine series showed excellent inhibition of the expression of inflammatory cytokines in LPS-stimulated macrophages. Compounds X10, X12, X13, X14, and X15 inhibited TNF-α and IL-6 release in a dose-dependent manner, and X12 showed no cytotoxicity in hepatic cells. Furthermore, X12 exhibited a significant protection against LPS-induced septic death in mouse models. Together, these data present a series of new imidazopyridines with potential therapeutic effects in acute inflammatory diseases.

Synthesis and biological evaluation of allylated and prenylated mono-carbonyl analogs of curcumin as anti-inflammatory agents.

Curcumin has been shown to possess anti-inflammatory activities but has been limited for its low stability and poor bioavailability. We have previously reported four series of 5-carbon linker-containing mono-carbonyl analogs of curcumin (MACs). In continuation of our ongoing research, we designed and synthesized 33 novel allylated or prenylated MACs here, and evaluated their anti-inflammatory effects in RAW 264.7 macrophages. A majority of them effectively inhibited the LPS-induced expression of TNF-α and IL-6, especially IL-6. The preliminary SAR and quantitative SAR analysis were conducted. Compound 14q is the most potent analog among them, and exhibits significant protection against LPS-induced death in septic mice. Together, these data present a series of new analogs of curcumin as promising anti-inflammatory agents.

Synthesis and biological evaluation of novel thiazolidinone derivatives as potential anti-inflammatory agents

The modulation of pro-inflammatory cytokines provides a target for controlling inflammatory diseases and attracts much attention in current anti-inflammatory drug development. Here, four series of thiazolidinone derivatives were synthesized and screened for anti-inflammatory activities. A majority of these compounds showed excellent inhibition on the expression of TNF-α and IL-6 in LPS-stimulated macrophages. Discussions are given regarding the structure-activity relationships. Compounds 12d and 12h inhibited LPS-induced TNF-α and IL-6 release in a dose-dependent manner. Furthermore, 12d exhibited a significant protection against LPS-induced septic death in mouse model. Together, these data present a series of new thiazolidinones with potential therapeutic effects in acute inflammatory diseases and they could be important leads in the continuing anti-inflammatory drug research.

MD-2 as the target of a novel small molecule, L6H21, in the attenuation of LPS-induced inflammatory response and sepsis.

Myeloid differentiation 2 (MD‐2) recognizes LPS, which is required for TLR4 activation, and represents an attractive therapeutic target for severe inflammatory disorders. We previously found that a chalcone derivative, L6H21, could inhibit LPS‐induced overexpression of TNF‐α and IL‐6 in macrophages. Here, we performed a series of biochemical experiments to investigate whether L6H21 specifically targets MD‐2 and inhibits the interaction and signalling transduction of LPS‐TLR4/MD‐2.

Curcumin Analog L48H37 Prevents Lipopolysaccharide-Induced TLR4 Signaling Pathway Activation and Sepsis via Targeting MD2

Endotoxin-induced acute inflammatory diseases such as sepsis, mediated by excessive production of various proinflammatory cytokines, remain the leading cause of mortality in critically ill patients. Lipopolysaccharide (LPS), the characteristic endotoxin found in the outer membrane of Gram-negative bacteria, can induce the innate immunity system and through the myeloid differentiation protein 2 (MD2) and Toll-like receptor 4 (TLR4) complex, increase the production of inflammatory mediators. Our previous studies have found that a curcumin analog, L48H37 [1-ethyl-3,5-bis(3,4,5-trimethoxybenzylidene)piperidin-4-one], was able to inhibit LPS-induced inflammation, particularly tumor necrosis factor α and interleukin 6 production and gene expression in mouse macrophages. In this study, a series of biochemical experiments demonstrate L48H37 specifically targets MD2 and inhibits the interaction and signaling transduction of LPS-TLR4/MD2. L48H37 binds to the hydrophobic region of MD2 pocket and forms hydrogen bond interactions with Arg90 and Tyr102. Subsequently, L48H37 was shown to suppress LPS-induced mitogen-activated protein kinase phosphorylation and nuclear factor κB activation in macrophages; it also dose dependently inhibits the cytokine expression in macrophages and human peripheral blood mononuclear cells stimulated by LPS. In LPS-induced septic mice, both pretreatment and treatment with L48H37 significantly improved survival and protected lung injury. Taken together, this work identified a new MD2 specific inhibitor, L48H37, as a potential candidate in the treatment of sepsis.

Piperlongumine as a direct TrxR1 inhibitor with suppressive activity against gastric cancer

Piperlongumine (PL), a natural alkaloid isolated from the fruit of long pepper, is known to selectively kill tumor cells while sparing their normal counterparts. However, the cellular target and potent anticancer efficacy of PL in numerous types of human cancer cells have not been fully defined. We report here that PL may interact with the thioredoxin reductase 1 (TrxR1), an important selenocysteine (Sec)-containing antioxidant enzyme, to induce reactive oxygen species (ROS)-mediated apoptosis in human gastric cancer cells. By inhibiting TrxR1 activity and increasing intracellular ROS levels, PL induces a lethal endoplasmic reticulum stress and mitochondrial dysfunction in human gastric cancer cells. Importantly, knockdown of TrxR1 sensitizes cells to PL treatment, and PL displays synergistic lethality with GSH inhibitors (BSO and Erastin) against gastric cancer cells. In vivo, PL treatment markedly reduces the TrxR1 activity and tumor cell burden. Remarkably, TrxR1 was significantly overexpressed in gastric cancer cell lines and human gastric cancer tissues. Targeting TrxR1 with PL thus discloses a previously unrecognized mechanism underlying the biological activity of PL and provides an in-depth insight into the action of PL in the treatment of gastric cancer.

Discovery of a New Inhibitor of Myeloid Differentiation 2 from Cinnamamide Derivatives with Anti-Inflammatory Activity in Sepsis and Acute Lung Injury

Acute inflammatory diseases, including acute lung injury and sepsis, remain the most common life-threatening illness in intensive care units worldwide. Cinnamamide has been incorporated in several synthetic compounds with therapeutic potentials including anti-inflammatory properties. However, the possible mechanism and direct molecular target of cinnamamides for their anti-inflammatory effects were rarely investigated. In this study, we synthesized a series of cinnamamides and evaluated their anti-inflammatory activities. The most active compound, 2i, was found to block LPS-induced MD2/TLR4 pro-inflammatory signaling activation in vitro and to attenuate LPS-caused sepsis and acute lung injury in vivo. Mechanistically, we demonstrated that 2i exerts its anti-inflammatory effects by directly targeting and binding MD2 in Arg90 and Tyr102 residues and inhibiting MD2/TLR4 complex formation. Taken together, this work presents a novel MD2 inhibitor, 2i, which has the potential to be developed as a candidate for the treatment of sepsis, and provides a new lead structure for the development of anti-inflammatory agents targeting MD2.

Discovery of new MD2 inhibitor from chalcone derivatives with anti-inflammatory effects in LPS-induced acute lung injury

Acute lung injury (ALI) is a life-threatening acute inflammatory disease with limited options available for therapy. Myeloid differentiation protein 2, a co-receptor of TLR4, is absolutely required for TLR4 sense LPS, and represents an attractive target for treating severe inflammatory diseases. In this study, we designed and synthesized 31 chalcone derivatives that contain the moiety of (E)-4-phenylbut-3-en-2-one, which we consider the core structure of current MD2 inhibitors. We first evaluated the anti-inflammatory activities of these compounds in MPMs. For the most active compound 20, we confirmed that it is a specific MD2 inhibitor through a series of biochemical experiments and elucidated that it binds to the hydrophobic pocket of MD2 via hydrogen bonds with Arg90 and Tyr102 residues. Compound 20 also blocked the LPS-induced activation of TLR4/MD2 -downstream pro-inflammatory MAPKs/NF-κB signaling pathways. In a rat model with ALI induced by intracheal LPS instillation, administration with compound 20 exhibited significant protective effect against ALI, accompanied by the inhibition of TLR4/MD2 complex formation in lung tissues. Taken together, the results of this study suggest the specific MD2 inhibitor from chalcone derivatives we identified is a potential candidate for treating acute inflammatory diseases.

Synthesis and biological evaluation of novel oxindole-based RTK inhibitors as anti-cancer agents.

Given that receptor tyrosine kinases (RTKs) have emerged as key regulators of all aspects of cancer development, including proliferation, invasion, angiogenesis and metastasis, the RTK family represents an important therapeutic target for anti-cancer drug development. Oxindole structure has been used in RTK inhibitors such as SU4984 and intedanib. In this study, two series of new heterocyclic compounds containing oxindole scaffold have been designed and synthesized, and their inhibitory activity against the proliferation of nine cancer cell lines has been evaluated. Among them, compounds 9a and 9b displayed the strongest anti-proliferative activity with the IC50s below 10μM. Flow cytometric analysis showed that the compounds 9a and 9b dose-dependently arrested the cell cycle at G0/G1 phase. Although the leading compounds SU4984 and intedanib targets FGFR1, the kinase activity test revealed that these compounds only showed slight inhibitory activity on FGFR1 kinase. Further enzymatic test aided by molecular docking simulation in the ATP-binding site demonstrated that 9a and 9b are potent inhibitors of c-Kit kinase. These compounds are worthy of further evaluation as anticancer agents.