Meiyu Geng

Molecularly targeted cancer therapy: some lessons from the past decade

The tremendous advances achieved in the understanding of cancer biology have delivered unprecedented progress in molecularly targeted cancer therapy in the past decade. The fast growing category of targeted anticancer agents available for clinical use is accompanied by a conceptual revolution in anticancer drug development. Nevertheless, molecularly targeted cancer therapy remains challenged by a high failure rate and an extremely small proportion of patients that can benefit. It is pivotal to take lessons from the past and seek new solutions. This review discusses conceptual progress and remaining challenges in molecularly targeted cancer therapy, and proposes feasible alternatives to increase chances of clinical success in the future.

Effect of acidic oligosaccharide sugar chain on scopolamine-induced memory impairment in rats and its related mechanisms

In this study we evaluated the effect of a novel, marine-derived, acidic oligosaccharide on scopolamine-induced amnesia in rats using the Morris water maze test. The results show that 30-day administration of this oligosaccharide, referred to as acidic oligosaccharide sugar chain (AOSC), to rats attenuates memory impairment by scopolamine, as evaluated by shortened escape latency, swimming distance, and increased swimming time of rats with memory impairment induced by scopolamine in the quadrant where the platform is placed. The data additionally suggest that an appropriate dose of scopolamine, a traditional muscarinic receptor antagonist, elevates oxidative damage in brain, characterized by inactivation of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and consequently, inhibition of ATPase in the hippocampus and cerebral cortex. AOSC ameliorates oxidative injuries caused by scopolamine by increasing the activities of SOD, GSH-Px, and ATPase. Further investigation by flow cytometry revealed that AOSC significantly reduces the overloading of intracellular free calcium ion ([Ca2+]i), thus suppressing apoptosis induced by H2O2 in human neuroblastoma SH-SY5Y cells. These findings suggest that AOSC can induce cognitive improvement via its antioxidant activity.

Small molecule inhibitors of amyloid β peptide aggregation as a potential therapeutic strategy for Alzheimer's disease

Amyloid β (Aβ) peptides have long been viewed as a potential target for Alzheimers disease (AD). Aggregation of Aβ peptides in the brain tissue is believed to be an exclusively pathological process. Therefore, blocking the initial stages of Aβ peptide aggregation with small molecules could hold considerable promise as the starting point for the development of new therapies for AD. Recent rapid progresses in our understanding of toxic amyloid assembly provide a fresh impetus for this interesting approach. Here, we discuss the problems, challenges and new concepts in targeting Aβ peptides.

Oligomannurarate Sulfate, a Novel Heparanase Inhibitor Simultaneously Targeting Basic Fibroblast Growth Factor, Combats Tumor Angiogenesis and Metastasis

Inhibitors of tumor angiogenesis and metastasis are increasingly emerging as promising agents for cancer therapy. Recently, heparanase inhibitors have offered a new avenue for such work because heparanase is thought to be critically involved in the metastatic and angiogenic potentials of tumor cells. Here, we report that oligomannurarate sulfate (JG3), a novel marine-derived oligosaccharide, acts as a heparanase inhibitor. Our results revealed that JG3 significantly inhibited tumor angiogenesis and metastasis, both in vitro and in vivo, by combating heparanase activity via binding to the KKDC and QPLK domains of the heparanase molecule. The JG3-heparanase interaction was competitively inhibited by low molecular weight heparin (4,000 Da) but not by other glycosaminoglycans. In addition, JG3 abolished heparanase-driven invasion, inhibited the release of heparan sulfate-sequestered basic fibroblast growth factor (bFGF) from the extracellular matrix, and repressed subsequent angiogenesis. Moreover, JG3 inactivated bFGF-induced bFGF receptor and extracellular signal-regulated kinase 1/2 phosphorylation and blocked bFGF-triggered angiogenic events by directly binding to bFGF. Thus, JG3 seems to inhibit both major heparanase activities by simultaneously acting as a substrate mimetic and as a competitive inhibitor of heparan sulfate. These findings suggest that JG3 should be considered as a promising candidate agent for cancer therapy.

R16, a novel amonafide analogue, induces apoptosis and G2-M arrest via poisoning topoisomerase II.

Amonafide, a naphthalimide derivative, although selected for exploratory clinical trials for its potent anticancer activity, has long been challenged by its unpredictable side effects. In the present study, a novel amonafide analogue, 2-(2-dimethylamino)-6-thia-2-aza-benzo-[def]-chrysene-1,3-diones (R16) was synthesized by substituting 5′-NH2 of the naphthyl with a heterocyclic group to amonafide, with additional introduction of a thiol group. In a panel of various human tumor cell lines, R16 was more cytotoxic than its parent compound amonafide. It was also effective against multidrug-resistant cells. Importantly, the i.p. administration of R16 inhibited tumor growth in mice implanted with S-180 sarcoma and H22 hepatoma. The molecular and cellular machinery studies showed that the R16 functions as a topoisomerase II (topo II) poison via binding to the ATPase domain of human topo IIα. The superior cytotoxicity of R16 to amonafide was ascribed to its potent effects on trapping topo II–DNA cleavage complexes. Moreover, using a topo II catalytic inhibitor aclarubicin, ataxia-telangiectasia-mutated (ATM)/ATM- and Rad3-related (ATR) kinase inhibitor caffeine and topo II–deficient HL-60/MX2 cells, we further showed that R16-triggered DNA double-strand breaks, tumor cell cycle arrest, and apoptosis were in a topo II–dependent manner. Taken together, R16 stood out by its improved anticancer activity, appreciable anti–multidrug resistance activities, and well-defined topo II poisoning mechanisms, as comparable with the parent compound amonafide. All these collectively promise the potential value of R16 as an anticancer drug candidate, which deserves further development. [Mol Cancer Ther 2007;6(2):484–95]

Synthesis and c-Met Kinase Inhibition of 3,5-Disubstituted and 3,5,7-Trisubstituted Quinolines: Identification of 3-(4-Acetylpiperazin-1-yl)-5-(3-nitrobenzylamino)-7- (trifluoromethyl)quinoline as a Novel Anticancer Agent

By use of an improved synthetic strategy, a series of 3,5-disubstituted and 3,5,7-trisubstituted quinolines were readily prepared. 3,5,7-Trisubstituted quinolines 21a-c, 21l, and 27a-c were identified as the most potent c-Met inhibitors with IC(50) of less than 1.0 nM. Compound 21b showed the most promising overall PK profile and has high potency and extraordinary selectivity to c-Met against c-Met family member Ron and 12 other tyrosine kinases. It produced constitutive inhibition of c-Met phosphorylation in c-Met dependent cell lines. At doses of 100 mg/kg, compound 21b showed statistically significant tumor growth inhibition (68-69%) in both NIH-3T3-TPR-Met and U-87 MG human gliobastoma xenograft models. These results clearly indicated that compound 21b is a potent and highly selective c-Met inhibitor. Its favorable in vitro and in vivo profiles warrant further investigation.

Extensive crosstalk between O-GlcNAcylation and phosphorylation regulates Akt signaling.

O-linked N-acetylglucosamine glycosylations (O-GlcNAc) and O-linked phosphorylations (O-phosphate), as two important types of post-translational modifications, often occur on the same protein and bear a reciprocal relationship. In addition to the well documented phosphorylations that control Akt activity, Akt also undergoes O-GlcNAcylation, but the interplay between these two modifications and the biological significance remain unclear, largely due to the technique challenges. Here, we applied a two-step analytic approach composed of the O-GlcNAc immunoenrichment and subsequent O-phosphate immunodetection. Such an easy method enabled us to visualize endogenous glycosylated and phosphorylated Akt subpopulations in parallel and observed the inhibitory effect of Akt O-GlcNAcylations on its phosphorylation. Further studies utilizing mass spectrometry and mutagenesis approaches showed that O-GlcNAcylations at Thr 305 and Thr 312 inhibited Akt phosphorylation at Thr 308 via disrupting the interaction between Akt and PDK1. The impaired Akt activation in turn resulted in the compromised biological functions of Akt, as evidenced by suppressed cell proliferation and migration capabilities. Together, this study revealed an extensive crosstalk between O-GlcNAcylations and phosphorylations of Akt and demonstrated O-GlcNAcylation as a new regulatory modification for Akt signaling.

Design, Synthesis, and Biological Evaluation of Novel Conformationally Constrained Inhibitors Targeting Epidermal Growth Factor Receptor Threonine790 → Methionine790 Mutant

The EGFR(T790M) mutant contributes approximately 50% to clinically acquired resistance against gefitinib or erlotinib. However, almost all the single agent clinical trials of the second generation irreversible EGFR inhibitors appear inadequate to overcome the EGFR(T790M)-related resistance. We have designed and synthesized a series of 2-oxo-3,4-dihydropyrimido[4,5-d]pyrimidinyl derivatives as novel EGFR inhibitors. The most potent compounds, 2q and 2s, inhibited the enzymatic activities of wild-type and mutated EGFRs, with IC(50) values in subnanomolar ranges, including the T790M mutants. The kinase inhibitory efficiencies of the compounds were further validated by Western blot analysis of the activation of EGFR and downstream signaling in cancer cells harboring different mutants of EGFR. The compounds also strongly inhibited the proliferation of H1975 non small cell lung cancer cells bearing EGFR(L858R/T790M), while being significantly less toxic to normal cells. Moreover, 2s displayed promising anticancer efficacy in a human NSCLC (H1975) xenograft nude mouse model.

A novel long non-coding RNA-ARA: Adriamycin Resistance Associated

Long non-coding RNAs (lncRNAs) are emerging as an integral functional component of human genome and have been investigated as critical regulators in molecular biology of cancer. A recent study reported that lncRNA-UCA1 induced drug resistance in adriamycin chemotherapy. However, the contributions of lncRNAs to adriamycin resistance in cancers remain largely unknown. To address this issue, we performed a genome-wide lncRNA microarray analysis in adriamycin resistant MCF-7/ADR and parental MCF-7 cells, and revealed differential expression of lncRNAs in distinct category and chromosome distribution patterns. A specific differentially expressed lncRNA (Adriamycin Resistance Associated, termed ARA) was validated in MCF-7/ADR and HepG2/ADR cells. ARA is derived from an intron of PAK3 gene, predicted to contain several stable hairpins in secondary structure and has conservative sequences in primates. ARA expression is significantly associated with adriamycin sensitivity in a panel of breast and liver cancer cell lines and is markedly up-regulated in parental sensitive MCF-7 and HepG2 cell lines after receiving adriamycin treatment. The functions of ARA were assessed by silencing this lncRNA in vitro, and we found that ARA knockdown reduced the proliferation, induced cell death, G2/M arrest and migration defects. Furthermore, microarray transcriptomic analysis was carried out to comprehensively depict the ARA-regulated genes. We showed that ARA can modulate multiple signalling pathways, including MAPK signalling pathway, metabolism pathways, cell cycle and cell adhesion-related biological pathways, and regulate cellular processes, including transcriptional processes and protein binding function. Overall, our results indicate novel insights of adriamycin resistance in lncRNA level.

Curcumin Induces Cell Death and Restores Tamoxifen Sensitivity in the Antiestrogen-Resistant Breast Cancer Cell Lines MCF-7/LCC2 and MCF-7/LCC9

Curcumin, a principal component of turmeric (Curcuma longa), has potential therapeutic activities against breast cancer through multiple signaling pathways. Increasing evidence indicates that curcumin reverses chemo-resistance and sensitizes cancer cells to chemotherapy and targeted therapy in breast cancer. To date, few studies have explored its potential antiproliferation effects and resistance reversal in antiestrogen-resistant breast cancer. In this study, we therefore investigated the efficacy of curcumin alone and in combination with tamoxifen in the established antiestrogen-resistant breast cancer cell lines MCF-7/LCC2 and MCF-7/LCC9. We discovered that curcumin treatment displayed anti-proliferative and pro-apoptotic activities and induced cell cycle arrest at G2/M phase. Of note, the combination of curcumin and tamoxifen resulted in a synergistic survival inhibition in MCF-7/LCC2 and MCF-7/LCC9 cells. Moreover, we found that curcumin targeted multiple signals involved in growth maintenance and resistance acquisition in endocrine resistant cells. In our cell models, curcumin could suppress expression of pro-growth and anti-apoptosis molecules, induce inactivation of NF-κB, Src and Akt/mTOR pathways and downregulate the key epigenetic modifier EZH2. The above findings suggested that curcumin alone and combinations of curcumin with endocrine therapy may be of therapeutic benefit for endocrine-resistant breast cancer.