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Objectives Several plaque and lesion characteristics have been associated with an increased risk for procedural stroke during or shortly after carotid artery stenting (CAS). While technical advancements in stent design and cerebral protection devices (CPD) may help reduce the procedural stroke risk, and anatomy remains important, tailoring stenting procedures according to plaque and lesion characteristics might be a useful strategy in reducing stroke associated with CAS. In this descriptive report of the ongoing Asymptomatic Carotid Surgery Trial-2 (ACST-2), it was assessed whether choice for stent and use or type of CPD was influenced by plaque and lesion characteristics. Materials and methods Trial patients who underwent CAS between 2008 and 2015 were included in this study. Chi-square statistics were used to study the effects of plaque echolucency, ipsilateral preocclusive disease (90–99%), and contralateral high-grade stenosis (>50%) or occlusion of the carotid artery on interventionalists' choice for stent and CPD. Differences in treatment preference between specialties were also analysed. Results In this study, 831 patients from 88 ACST-2 centres were included. Almost all procedures were performed by either interventional radiologists (50%) or vascular surgeons (45%). Plaque echolucency, ipsilateral preocclusive disease (90–99%), and significant contralateral stenosis (>50%) or occlusion did not affect the choice of stent or either the use of cerebral protection and type of CPD employed (i.e., filter/flow reversal). Vascular surgeons used a CPD significantly more often than interventional radiologists (98.6% vs. 76.3%; p < .001), but this choice did not appear to be dependent on patient characteristics. Conclusions In ACST-2, plaque characteristics and severity of stenosis did not primarily determine interventionalists' choice of stent or use or type of CPD, suggesting that other factors, such as vascular anatomy or personal and centre preference, may be more important. Stent and CPD use was highly heterogeneous among participating European centres.

Human FASN is the key enzyme required for de novo synthesis of fatty acids. Up-regulated FASN expression has been reported in various human cancers and was thought to contribute to poor prognosis and recurrence of these cancers. Studies using model cell lines have indicated the role of FASN in both intrinsic and acquired drug and radiation resistance. Recent studies suggest that FASN may play an important role in regulating gene expression such as pro-apoptotic proteins and cellular processes such as DNA repair pathways, which in turn contribute to resistance to drug and radiation-induced apoptosis. In this review, we will highlight our recent progress in understanding the mechanism of FASN-induced resistance.

The lack of correlative and predictive models to assess acute and chronic toxicities limits the rapid pre-clinical development of new therapeutics. This barrier is due in part to the exponential growth of nanotechnology and nanotherapeutics, coupled with the lack of rigorous and robust screening assays and putative standards. It is a fairly simple and cost-effective process to initially screen the toxicity of a nanomaterial by using invitro cell cultures; unfortunately it is nearly impossible to imitate a complimentary invivo system. Small mammalian models are the most common method used to assess possible toxicities and biodistribution of nanomaterials in humans. Alternatively, Daniorerio, commonly known as zebrafish, are proving to be a quick, cheap, and facile model to conservatively assess toxicity of nanomaterials.

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and outcome is dismal, due to tumor heterogeneity and lack of effective treatment options for patients with later stage disease. Transcatheter arterial chemoembolization (TACE) is the gold standard of therapy for patients with intermediate to locally advanced tumors. TACE delivers a high dose of chemotherapy directly to the tumor via the hepatic artery, followed by an embolizing agent to restrict tumor blood supply. However, tumor hypoxia is linked to alterations in metabolism, such as increased glycolysis (the Warburg effect), and can lead to enhanced cell survival. Several randomized control trials (RCTs) showed a survival benefit with TACE, but only with strict patient selection criteria. In Asia, TACE is also commonly used as adjuvant therapy after surgical resection, yet RCTs evaluating adjuvant TACE have shown conflicting results, likely due to patient selection and stratification. We hypothesize that tumor gene expression is predictive of response following TACE, and that differential cellular metabolism resembling a hypoxic phenotype prior to treatment is responsible for TACE resistance. We retrospectively analyzed gene expression data in treatment-naive tumor tissue from a cohort of Chinese patients who received TACE. Using hierarchical clustering, followed by class comparison and survival risk prediction, we identified a 14-gene signature that is predictive of response vs. non-response to TACE, as measured by overall survival, independent of other clinical variables. We found that hypoxia- and glycolysis-related genes are enriched among differentially expressed genes in TACE Responders vs. Non-Responders, and that hypoxia master regulator HIF-1α and hypoxia target gene VEGF are significantly up-regulated in Non-Responders. We determined that a key glycolysis gene is up-regulated in Non-Responders, and conversely, two rate-limiting genes involved in gluconeogenesis, the pathway opposing glycolysis, are up-regulated in Responders. We also examined metabolomic data from the TACE cohort, and found an enrichment of glycolysis-related metabolites in Non-Responders, and gluconeogenesis-related metabolites in Responders. Further investigation will be required to connect altered glucose metabolism to TACE resistance and to determine driver genes linking hypoxia and metabolism, which, together with our 14-gene signature, may serve as a stratification tool to guide personalized treatment modalities for HCC patients. Citation Format: Valerie Fako, Joyce Lee, Tan-To Cheung, Irene O. Ng, Xin W. Wang. Hypoxia response signaling is linked to TACE resistance in hepatocellular carcinoma (HCC) patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 544. doi:10.1158/1538-7445.AM2017-544

Fatty acid synthase (FASN), the enzyme responsible for de novo synthesis of free fatty acids, is up-regulated in many cancers. FASN is essential for cancer cell survival and contributes to drug resistance and poor prognosis. However, it is not expressed in most nonlipogenic normal tissues. Thus, FASN is a desirable target for drug discovery. Although different FASN inhibitors have been identified, none has successfully moved into clinical use. In this study, using in silico screening of an FDA-approved drug database, we identified proton pump inhibitors (PPIs) as effective inhibitors of the thioesterase activity of human FASN. Further investigation showed that PPIs inhibited proliferation and induced apoptosis of cancer cells. Supplementation of palmitate, the end product of FASN catalysis, rescued cancer cells from PPI-induced cell death. These findings provide new evidence for the mechanism by which this FDA-approved class of compounds may be acting on cancer cells.

Fatty acid synthase (FASN), the sole protein capable of de novo synthesis of free fatty acids, is overexpressed in a wide variety of human cancers and is associated with poor prognosis and aggressiveness of these cancers. Orlistat, an FDA-approved drug for obesity treatment that inhibits pancreatic lipases in the GI tract, also inhibits the thioesterase (TE) of human FASN. The cocrystal structure of TE with orlistat shows a pseudo TE dimer containing two different forms of orlistat in the active site, an intermediate that is covalently bound to a serine residue (Ser2308) and a hydrolyzed and inactivated product. In this study, we attempted to understand the mechanism of TE-catalyzed orlistat hydrolysis by examining the role of the hexyl tail of the covalently bound orlistat in water activation for hydrolysis using molecular dynamics simulations. We found that the hexyl tail of the covalently bound orlistat undergoes a conformational transition, which is accompanied by destabilization of a hydrogen bond between a hydroxyl moiety of orlistat and the catalytic His2481 of TE that in turn leads to an increased hydrogen bonding between water molecules and His2481 and increased chance for water activation to hydrolyze the covalent bond between orlistat and Ser2308. Thus, the conformation of the hexyl tail of orlistat plays an important role in orlistat hydrolysis. Strategies that stabilize the hexyl tail may lead to the design of more potent irreversible inhibitors that target FASN and block TE activity with greater endurance.

The potential toxicity of nanoparticles is addressed by utilizing a putative attractive model in developmental biology and genetics: the zebrafish (Danio rerio). Transparent zebrafish embryos, possessing a high degree of homology to the human genome, offer an economically feasible, medium-throughput screening platform for noninvasive real-time assessments of toxicity. Using colloidal silver (cAg) and gold nanoparticles (cAu) in a panoply of sizes (3, 10, 50, and 100 nm) and a semiquantitative scoring system, it is found that cAg produces almost 100% mortality at 120 h post-fertilization, while cAu produces less than 3% mortality at the same time point. Furthermore, while cAu induces minimal sublethal toxic effects, cAg treatments generate a variety of embryonic morphological malformations. Both cAg and cAu are taken up by the embryos and control experiments, suggesting that cAg toxicity is caused by the nanoparticles themselves or Ag(+) that is formed during in vivo nanoparticle destabilization. Although cAg toxicity is slightly size dependent at certain concentrations and time points, the most striking result is that parallel sizes of cAg and cAu induce significantly different toxic profiles, with the former being toxic and the latter being inert in all exposed sizes. Therefore, it is proposed that nanoparticle chemistry is as, if not more, important than specific nanosizes at inducing toxicity in vivo. Ultimately such assessments using the zebrafish embryo model should lead to the identification of nanomaterial characteristics that afford minimal or no toxicity and guide more rational designs of materials on the nanoscale.

Fatty acid synthase (FASN), a seven domain enzyme, is the sole protein capable of de novo synthesis of free fatty acids, most commonly 16-carbon palmitate. The fatty acid synthesis cycle begins with the condensation of acetyl-CoA and malonyl-CoA, and continues with the elongation of the fatty acid chain, which is tethered to an acyl carrier protein domain (ACP), via a repeating cycle. At the end of elongation, the thioesterase (TE) domain of FASN, a member of the serine hydrolase family with an Asp-His-Ser catalytic triad, cleaves the bond between palmitate and ACP, and releases free palmitate. FASN has been found to be over-expressed in a wide variety of human cancers, and this over-expression is correlated to a higher metastatic potential and poorer prognosis in cancer patients. FASN over-expression is also associated with increased resistance toward cancer chemotherapeutics. Orlistat, an FDA approved drug for obesity treatment that prevents uptake of dietary fats by inhibiting pancreatic lipases in the gastrointestinal tract, is a compound found to act as a reversible inhibitor of FASN TE. A previous study using the co-crystal structure of the TE domain with orlistat found that orlistat was covalently bound to the active site Ser within the TE domain, indicating that inhibition of FASN by orlistat halts the fatty acid synthesis cycle by blocking the release of free palmitate from the ACP. A hydrolyzed form of orlistat was also observed in the active site of TE, demonstrating that orlistat is not a stable inhibitor of FASN. In this study, we examined the mechanism of orlistat hydrolysis within the TE domain of FASN using molecular dynamics simulations. We found that the hexanoyl tail of orlistat is capable of shifting while covalently bound to the active site Ser, and that this shift is accompanied by the destabilization of a hydrogen bond that exists between a hydroxyl moiety of orlistat and the active site His. Once this hydrogen bond is destabilized, a catalytic water molecule can enter the active site of TE with the proper orientation for catalysis of the covalent bond between orlistat and Ser. These findings suggest that the hexanoyl tail of orlistat plays an important role in its hydrolysis and may guide the future design of new inhibitors that target the TE domain of FASN with greater endurance for potential use in the treatment of cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3978. doi:1538-7445.AM2012-3978