Novel second-generation taxoids with systematic modifications at the C2, C10, and C3'N positions were synthesized and their structure-activity relationships studied. A number of these taxoids exhibited exceptionally high potentency against multidrug drug-resistant cell lines, and several taxoids exhibited virtually no difference in potency against the drug-sensitive and drug-resistant cell lines. These exceptionally potent taxoids were termed "third-generation taxoids". 19 (SB-T-1214), 14g (SB-T-121303), and 14i (SB-T-1213031), exhibited excellent activity against paclitaxelresistant ovarian cancer cell lines as well, wherein the drug-resistance is mediated by β-tubulin mutation. These taxoids were found to possess exceptional activity in promoting tubulin assembly, forming numerous very short microtubules similar to those formed by discodermolide. Taxoids 19 and 14g also showed excellent cytotoxicity against 4 pancreatic cancer cell lines, expressing 3-4 multidrug resistant genes. Moreover, taxoid 19 exhibited excellent in vivo efficacy against highly drug-resistant CFPAC-1 pancreatic as well as DLD-1 human colon tumor xenografts in mice.

A new computational docking protocol has been developed and used in combination with conformational information inferred from REDOR-NMR experiments on microtubule bound 2-(p-fluorobenzoyl)paclitaxel to delineate a unique tubulin binding structure of paclitaxel. A conformationally constrained macrocyclic taxoid bearing a linker between the C-14 and C-3'N positions has been designed and synthesized to enforce this "REDOR-taxol" conformation. The novel taxoid SB-T-2053 inhibits the growth of MCF-7 and LCC-6 human breast cancer cells (wild-type and drug resistant) on the same order of magnitude as paclitaxel. Moreover, SB-T-2053 induces in vitro tubulin polymerization at least as well as paclitaxel, which directly validates our drug design process. These results open a new avenue for drug design of next generation taxoids and other microtubule-stabilizing agents based on the refined structural information of drug-tubulin complexes, in accordance with typical enzyme-inhibitor medicinal chemistry precepts.

Novel macrocyclic paclitaxel congeners were designed to mimic the bioactive conformation of paclitaxel. Computational analysis of the "REDOR-Taxol" structure revealed that this structure could be rigidified by connecting the C14 position of the baccatin moiety and the ortho position of C3'Nbenzoyl group (C3'BzN), which are ca. 7.5 Å apart, with a short linker (4−6 atoms). 7-TES-14β-allyloxybaccatin III and (3R,4S)-1-(2-alkenylbenzoyl)-β-lactams were selected as key components and the Ojima-Holton coupling afforded the corresponding paclitaxel-dienes. The Ru-catalyzed ringclosing metathesis (RCM) of paclitaxel-dienes gave the designed 15-and 16-membered macrocyclic taxoids. However, the RCM reaction to form the designed 14-membered macrocyclic taxoid did not proceed as planned. Instead, the attempted RCM reaction led to the occurrence of an unprecedented novel Ru-catalyzed diene-coupling process, giving the corresponding 15-membered macrocyclic taxoid (SB-T-2054). The biological activities of the novel macrocyclic taxoids were evaluated by tumor cell growth inhibition (i.e., cytotoxicity) and tubulin-polymerization assays. Those assays revealed high sensitivity of cytotoxicity to subtle conformational changes. Among the novel macrocyclic taxoids evaluated, SB-T-2054 is the most active compound, which possesses virtually the same potency as that of paclitaxel. The result may also indicate that SB-T-2054 structure is an excellent mimic of the bioactive conformation of paclitaxel. Computational analysis for the observed structure-activity relationships is also performed and discussed.

Nuclear factor erythroid-2-related factor 2 (Nrf2) is a critical cell protector by inducing phase two detoxifying and anti-oxidant enzymes in normal cells. But recently, numerous evidence show Nrf2 may play the same beneficial roles toward the cancer cells. Nrf2 is found upexpressed in lots of cancers and promote the proliferation and drug resistance. But studies about the role of Nrf2 in the metastases are few. It has been testified that the tumor cells are under hypoxic conditions. As an important anti-oxidant element, the expression of Nrf2 may be upregulated, which in turn promotes the tumor invasion and metastases in the hypoxic microenvironment. Our team found the expression of Nrf2 correlated with the lymph node metastasis of esophageal squamous cell carcinoma by pathological sections of esophageal carcinoma patients. Further, the mechanism beneath it was studied in this paper. It was hypothesized that the hypoxia microenvironment transformed Nrf2 a friend to a foe. First, Eca-109 cells were treated with different concentration of CoCl2 . Western blot and quantitative reverse transcription-polymerase chain reaction showed that with the increase of the concentration of CoCl2 , the expression levels of Nrf2 and hypoxia-inducible factor-1 (HIF-1) alpha were upregulated simultaneously. By analyzing the data, a significant correlation between Nrf2 and HIF-1 alpha in the protein levels was found. Further, blockage of Nrf2 mediated by shRNA suppressed the expression of HIF-1 alpha, hemeoxygenase-1 (HO-1), and matrix metalloproteinase 2 but enhanced the expression of E-cadherin. In addition, the results of wound healing and invasion assay-verified blockage of Nrf2 suppressed the migration and invasion. So it was suggested that blockage of Nrf2 repressed the migration and invasion of esophageal squamous cell carcinoma cells in the hypoxic microenvironment. HIF-1 alpha might be one of the downstream genes of Nrf2 regulated through Nrf2/HO-1 axis in the CoCl2 model. Nrf2 inhibition suppressed matrix metalloproteinase 2 and enhanced E-cadherin partly through HIF-1 alpha way.

BackgroundThe dysregulation of long noncoding RNAs (lncRNAs) has been identified in a variety of cancers. An increasing number of studies have found the critical role of lncRNAs in the regulation of cellular processes, such as proliferation, invasion and differentiation. Long noncoding RNA papillary thyroid carcinoma susceptibility candidate 3 (PTCSC3) is a novel lncRNA that was primarily detected in papillary thyroid carcinoma. However, the biological function and molecular mechanism of lncRNA PTCSC3 in glioma are still unknown.MethodsThe expression level of lncRNA PTCSC3 in human microglia and glioma cell lines was examined using quantitative real-time polymerase chain reaction (qRT-PCR). The influence of lncRNA PTCSC3 on cell proliferation were studied using the cell counting kit-8, and cell cycle and apoptosis were analyzed by flow cytometry assays. The migration and invasion abilities were investigated by transwell and wound healing assays. The target genes of lncRNA PTCSC3 were explored by qRT-PCR, immunofluorescence and western blot.ResultsLncRNA PTCSC3 was significantly downregulated in glioma cell lines. The overexpression of lncRNA PTCSC3 suppressed proliferation and induced apoptosis in U87 and U251 cells. Additionally, the overexpression of lncRNA PTCSC3 inhibited the migration and invasion of U87 and U251 cells. Moreover, lncRNA PTCSC3 inhibited the epithelial-mesenchymal transition of U87 cells. The study also demonstrated that LRP6, as a receptor of the Wnt/β-catenin pathway, was a target of lncRNA PTCSC3. By evaluating the expression levels of Axin1, active β-catenin, c-myc, and cyclin D1, the study indicated that lncRNA PTCSC3 inhibited the activation of the Wnt/β-cateninpathway through targeting LRP6.ConclusionsLncRNA PTCSC3 inhibits the proliferation and migration of glioma cells and suppresses Wnt/β-catenin signaling pathway by targeting LRP6. LncRNA PTCSC3 is a potential therapeutic target for treatment of glioma.Electronic supplementary materialThe online version of this article (doi:10.1186/s12883-017-0813-6) contains supplementary material, which is available to authorized users.

A series of 3′-difluorovinyl taxoids with C10 modifications, as well as those with C2 and C10 modifications, were strategically designed to block the metabolism by cytochrome P-450 3A4 enzyme and synthesized. These novel difluorovinyl taxoids were evaluated for their cytotoxicity against drug-sensitive human breast (MCF7), multidrug-resistant (MDR) human ovarian (NCI/ADR), human colon (HT-29) and human pancreatic (PANC-1) cancer cell lines. 3′-Difluorovinyl taxoids exhibit several to 16 times better activity against MCF7, HT-29 and PANC-1 cell lines and up to three orders of magnitude higher potency against NCI/ADR cell line as compared to paclitaxel. Structure-activity relationship study shows the critical importance of the C2 modifications on the activity against MDR cancer cell line, while the C10 modifications have a rather minor effect on the potency with some exceptions. The effect of the C2 modifications on potency against MCF7 cell line increases in the following order: H < F < Cl

Discodermolide is a potentially important antitumor agent that stabilizes microtubules and blocks cells at the G2/M phase of the cell cycle in a manner similar to that of Taxol. Discodermolide also has unique properties that distinguish it from Taxol. In the present study, photoaffinity-labeled discodermolide analogues are used to investigate their binding site in tubulin. Three photoaffinity-labeled discodermolide analogues were synthesized, all of which promoted microtubule polymerization in the absence of GTP. The analogue, C19-[4-(4-(3)H-benzoyl-phenyl)-carbamate]-discodermolide (C19-[3H]BPC-discodermolide), was selected for photolabeling studies because it had the highest extent of photoincorporation, approximately 1%, of the three radiolabeled discodermolide analogues explored. Although compared to discodermolide, C19-BPC-discodermolide revealed no hypernucleation effect in the in vitro microtubule polymerization assay, it was more cytotoxic than discodermolide, and, like discodermolide, demonstrated synergism with Taxol. These results suggest that the hypernucleation effect of discodermolide is not involved in its cytotoxic activity. Similar to discodermolide, C19-BPC-discodermolide can effectively displace [3H]Taxol from microtubules, but Taxol cannot effectively displace C19-[3H]BPC-discodermolide binding. Discodermolide can effectively displace C19-[3H]BPC-discodermolide binding. Formic acid hydrolysis, immunoprecipitation experiments, and subtilisin digestion indicate that C19-BPC-discodermolide labels amino acid residues 305-433 in beta-tubulin. Further digestion with Asp-N and Arg-C enzymes suggested that C19-BPC-discodermolide binds to amino acid residues, 355-359, in beta-tubulin, which is in close proximity to the Taxol binding site. Molecular modeling guided by the above evidence led to a putative binding model for C19-BPC-discodermolide in tubulin.

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