LAF389 is a synthetic analogue of bengamides, a class of marine natural products that produce inhibitory effects on tumor growth in vitro and in vivo. A proteomics-based approach has been used to ...identify signaling pathways affected by bengamides. LAF389 treatment of cells resulted in altered mobility of a subset of proteins on two-dimensional gel electrophoresis. Detailed analysis of one of the proteins, 14-3-3gamma, showed that bengamide treatment resulted in retention of the amino-terminal methionine, suggesting that bengamides directly or indirectly inhibited methionine aminopeptidases (MetAps). Both known MetAps are inhibited by LAF389. Short interfering RNA suppression of MetAp2 also altered amino-terminal processing of 14-3-3gamma. A high resolution structure of human MetAp2 co-crystallized with a bengamide shows that the compound binds in a manner that mimics peptide substrates. Additionally, the structure reveals that three key hydroxyl groups on the inhibitor coordinate the di-cobalt center in the enzyme active site.
Inhibition of endothelial cell growth by fumagillin has been assumed to be mediated by inhibition of the molecular target methionine aminopeptidase 2 (MetAp2). New data show that depletion of MetAp2 ...by siRNA does not inhibit endothelial cell growth. Moreover, MetAp2-depleted endothelial cells remain responsive to inhibition by either fumagillin or a newly identified MetAp2 enzyme inhibitor. These data suggest that MetAp2 function is not required for endothelial cell proliferation.
Lipophilic camptothecin derivatives are considered to have negligible affinity for breast cancer resistance protein (BCRP;
ABCG2). Gimatecan, a new orally available 7- t ...-butoxyiminomethyl–substituted lipophilic camptothecin derivative, has been previously reported to be not a substrate for
BCRP. Using a panel of in vitro models, we tested whether gimatecan is a substrate for BCRP as well as for P-glycoprotein (MDR1) or multidrug resistance
protein 2 (MRP2; ABCC2), ATP-binding cassette drug efflux transporters involved in anticancer drug resistance, and able to
affect the pharmacokinetics of substrate drugs. Cell survival, drug transport, accumulation, and efflux were studied in IGROV1
and (human BCRP overexpressing) T8 cells, Madin-Darby canine kidney II (MDCKII-WT, MDCKII-Bcrp1, MDCKII-MDR1, and MDCKII-MRP2),
and LLCPK (LLCPK-WT and LLCPK-MDR1) cells. Competition with methotrexate uptake was studied in Sf9-BCRP membrane vesicles.
In vitro , expression of BCRP resulted in 8- to 10-fold resistance to gimatecan. In Transwell experiments, gimatecan was transported
by Bcrp1 and transport was inhibited by the BCRP/P-glycoprotein inhibitors elacridar and pantoprazole. Efflux of gimatecan
from MDCKII-Bcrp1 cells was faster than in WT cells. In Sf9-BCRP membrane vesicles, gimatecan significantly inhibited BCRP-mediated
transport of methotrexate. In contrast, gimatecan was not transported by MDR1 or MRP2. Gimatecan is transported by BCRP/Bcrp1
in vitro , although to a lesser extent than the camptothecin analogue topotecan. Implications of BCRP expression in the gut for the
oral development of gimatecan and the interaction between gimatecan and other BCRP substrate drugs and/or inhibitors warrant
further clinical investigation. Mol Cancer Ther 2007;6(12):3307–13
Bengamide B, a novel sponge-derived marine natural product with broad spectrum antitumor activity, was not suitable for further preclinical development because of its difficult synthesis and very ...poor water solubility. Bengamide B produced a 31% T/C at its solubility-limited maximum intravenous dose of 33 μmol/kg in MDA-MB-435 breast carcinoma implanted subcutaneously as a xenograft in nude mice. Compound 8a, a bengamide B analogue with three structural changes (t-Bu alkene substituent, unsubstituted lactam nitrogen, and inverted lactam 5‘-myristoyloxy group), was as potent as bengamide B in vitro and more efficacious than bengamide B in vivo. A series of ester-modified analogues based on 8a were synthesized and tested in vitro and in vivo (MDA-MB-435). The cyclohexyl- and phenethyl-substituted esters, 8c and 8g, respectively, had in vitro and in vivo activities similar to that of 8a and enhanced water solubility (ca. 1 mg/mL). Consequently, 8c and 8g were tested in the MDA-MB-435 xenograft model at 100 μmol/kg and produced 29% and 57% tumor regression, respectively.
Camptothecin, a potent cytotoxic agent that inhibits topoisomerase I, was identified in 1966 as a cytotoxic component in extracts of the Chinese tree Camptotheca acuminata. Initial clinical trials ...with this agent showed promising antitumour activity but due to unacceptable toxicity the trials were halted. The underlying cause of the toxicity was soon determined to be instability of the δ-lactone present in the structure. As a result, analogues were prepared that overcame the lactone instability, leading eventually to the chemotherapeutic drugs irinotecan and topotecan. Although these drugs proved successful in the clinic, side effects and a narrow spectrum of activity have limited their utility. In the decade since the development of these agents, continued research has greatly improved our understanding of camptothecin stability and pharmacology. From this has emerged several new series of analogues that will produce the next generation camptothecin. Silatecans are novel third generation camptothecin analogues that contain lipophilic silane groups. The incorporation of lipophilic substituents into the camptothecin structure provides enhanced blood stability, increased cell penetration and improved pharmacokinetics. This review will first examine the various mechanisms involved and approaches taken to develop new camptothecin-based drugs followed by an analysis of silatecan patents, example compounds and biological data.
Total Syntheses of Bengamides B and E Kinder, Frederick R; Wattanasin, Sompong; Versace, Richard W ...
Journal of organic chemistry,
03/2001, Letnik:
66, Številka:
6
Journal Article
Recenzirano
Total syntheses of the cytotoxic marine natural products bengamides B and E are described. Both bengamides are prepared via amide coupling of a protected polyhydroxylated lactone intermediate 9 with ...a suitably substituted aminocaprolactam intermediate. Lactone 9 is prepared in five steps from commercially available α-d-glucoheptonic γ-lactone. The key reactions are a selective deprotection of a 1,2-acetonide in the presence of a 1,3-acetonide and an (E)-selective olefination of an unstable aldehyde using a gem-dichromium reagent. The bengamide B lactam intermediate 10 is prepared in seven steps from commercially available (5R)-5-hydroxy-l-lysine (12). The desired S-configuration at the γ-OH lactam position is established using the Mitsunobu reaction.
Abstract
HER3 is a member of the ErbB family of receptor tyrosine kinases. Aberrant activation of HER3 as a result of HER2 amplification or neuregulin 1 (NRG1) over-expression has been demonstrated ...to mediate constitutive activation of downstream oncogenic signals. LJM716 is a fully human IgG1 anti-HER3 monoclonal antibody. It locks HER3 in an inactive conformation and prevents HER3 dimerization with other ErbB family members. This unique mode of action enables LJM716 to block both ligand dependent and ligand independent HER3 activation. In search of new indications that may benefit from anti-HER3 therapies, we noted that squamous cell carcinomas (SCC) tend to have relatively higher NRG1 expression as compared to their adenocarcinoma counterparts. Highest NRG1 expression was observed in the lung SCC cell lines in cell line encyclopedia (CLE). A subset of the lung SCC cell lines with high NRG1 expression are moderately sensitive to LJM716, with HER3 activation detected in all of the sensitive lines. Additionally, EGFR activation is consistently observed in our panel of squamous lung carcinoma models. In some cases, activation of HER2 and/or HER3 is also noted. We hypothesize that squamous lung carcinomas may be dependent on signaling through EGFR, HER2 and HER3. To completely block EGFR, HER2-HER3 signaling, we set to test the treatment of LJM716 and Cetixumab in a number of NGR 1 positive squamous lung carcinomas tumor models. Enhanced anti tumor activity of LJM716 and Cetixumab is observed in four out nine tumor models. Analysis of broad activation status of receptor tyrosine kinases (RTK) reveals that a subset of responsive models have activated pEGFR, pHER2 and pHER3. These data suggest that activated HER3 signaling may be important in a subset of lung squamous cell carcinoma. Combination of anti-HER3 and anti EGFR treatment is effective at inhibiting growth in these tumors.
Note: This abstract was not presented at the meeting.
Citation Format: Maria C. Pinzon-Ortiz, Xianhui Rong, Richard Versace, Qing Sheng, Z. Alexander Cao. Targeting HER3 and EGFR in NRG1 positive and HER3 mutated lung squamous cell carcinoma. abstract. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5320. doi:10.1158/1538-7445.AM2015-5320
We have synthesized a histone deacetylase inhibitor, NVP-LAQ824, a cinnamic hydroxamic acid, that inhibited in vitro enzymatic activities and transcriptionally activated the p21 promoter in reporter ...gene assays. NVP-LAQ824 selectively inhibited growth of cancer cell lines at submicromolar levels after 48-72 h of exposure, whereas higher concentrations and longer exposure times were required to retard the growth of normal dermal human fibroblasts. Flow cytometry studies revealed that both tumor and normal cells arrested in the G(2)-M phase of the cell cycle after compound treatment. However, an increased sub-G(1) population at 48 h (reminiscent of apoptotic cells) was observed only in the cancer cell line. Annexin V staining data supported our hypothesis that NVP-LAQ824 induced apoptosis in tumor and transformed cells but not in normal cells. Western blotting experiments showed an increased histone H3 and H4 acetylation level in NVP-LAQ824-treated cancer cells, suggesting that the likely in vivo target of NVP-LAQ824 was histone deacetylase(s). Finally, NVP-LAQ824 exhibited antitumor effects in a xenograft animal model. Together, our data indicated that the activity of NVP-LAQ824 was consistent with its intended mechanism of action. This novel histone deacetylase inhibitor is currently in clinical trials as an anticancer agent.
The in vitro metabolism of SDZ HDL 376, a thiocarbamide developed for the treatment of atherosclerosis, was investigated in rat, dog, monkey, and human liver microsomes, as well as in rat and human ...liver slices. 14CSDZ HDL 376 was extensively metabolized in all the species except human. In rat liver microsomes an S-oxide was the major metabolite. In human and monkey microsomes, carbon hydroxylation was favored. The NADPH-dependent oxidation of SDZ HDL 376 resulted in covalent binding to microsomal protein. Addition of GSH to the incubations decreased protein binding in a concentration-dependent manner and resulted in a novel SDZ HDL 376−GSH adduct. Adduct formation required NADPH and was mediated predominately by cytochrome P450. Inhibition of cytochrome P450 by 1-aminobenzotriazole resulted in a 95% decrease in adduct formation, while heat inactivation of flavin-containing monooxygenases resulted in a 10% decrease. Unlike other thiocarbamides which form disulfide adducts with GSH, the SDZ HDL 376 adduct contained a thioether linkage as characterized by LC/MS/MS and reference to a synthetic standard. Reactions performed with 35SGSH resulted in a 35SSDZ HDL 376−GSH adduct, demonstrating the sulfur was derived from GSH. Adduct formation was faster in rat microsomal reactions compared to human microsomes. Other structurally unrelated thiocarbamides (phenylthiourea, methimazole, 2-mercaptobenzimidazole, 2-mercaptoquinazoline, and 2-propyl-6-thiouracil) did not form similar adducts in rat liver microsomes supplemented with GSH. Therefore, the GSH adduct of SDZ HDL 376 is unique for this type of thiocarbamide. These results suggest that the bioactivation and detoxification of SDZ HDL 376 differ significantly from other thiocarbamides. Furthermore, the in vitro formation of S-oxides and GSH adducts in rat hepatic tissue, and ring hydroxylation and glucuronidation in human hepatic tissue, suggests rats may be more susceptible to the toxicity of SDZ HDL 376 compared to humans.
A series of N-hydroxy-3-phenyl-2-propenamides were prepared as novel inhibitors of human histone deacetylase (HDAC). These compounds were potent enzyme inhibitors, having IC50s < 400 nM in a ...partially purified enzyme assay. However, potency in cell growth inhibition assays ranged over 2 orders of magnitude in two human carcinoma cell lines. Selected compounds having cellular IC50 < 750 nM were tested for maximum tolerated dose (MTD) and for efficacy in the HCT116 human colon tumor xenograft assay. Four compounds having an MTD ≥ 100 mg/kg were selected for dose−response studies in the HCT116 xenograft model. One compound, 9 (NVP-LAQ824), had significant dose-related activity in the HCT116 colon and A549 lung tumor models, high MTD, and low gross toxicity. On the basis, in part, of these properties, 9 has entered human clinical trials in 2002.
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