Vasculogenesis: a crucial player in the resistance of solid tumours to radiotherapy

Tumours have two main ways to develop a vasculature: by angiogenesis, the sprouting of endothelial cells from nearby blood vessels, and vasculogenesis, the formation of blood vessels from circulating cells. Because tumour irradiation abrogates local angiogenesis, the tumour must rely on the vasculogenesis pathway for regrowth after irradiation. Tumour irradiation produces a marked influx of CD11b(+) myeloid cells (macrophages) into the tumours, and these are crucial to the formation of blood vessels in the tumours after irradiation and for the recurrence of the tumours. This process is driven by increased tumour hypoxia, which increases levels of HIF-1 (hypoxia-inducible factor 1), which in turn upregulates SDF-1 (stromal cell-derived factor 1 or CXCL12), the main driver of the vasculogenesis pathway. Inhibition of HIF-1 or of its downstream target SDF-1 prevents the radiation-induced influx of the CD11b(+) myeloid cells and delays or prevents the tumours from recurring following irradiation. Others and we have shown that with a variety of tumours in both mice and rats, the inhibition of the SDF-1/CXCR4 pathway delays or prevents the recurrence of implanted or autochthonous tumours following irradiation or following treatment with vascular disrupting agents or some chemotherapeutic drugs such as paclitaxel. In addition to the recruited macrophages, endothelial progenitor cells (EPCs) are also recruited to the irradiated tumours, a process also driven by SDF-1. Together, the recruited proangiogenic macrophages and the EPCs reform the tumour vasculature and allow the tumour to regrow following irradiation. This is a new paradigm with major implications for the treatment of solid tumours by radiotherapy.

Vascular Tissue Contractility Changes Following Late Gestational Exposure to Multi-Walled Carbon Nanotubes or their Dispersing Vehicle in Sprague Dawley Rats

Multi-walled carbon nanotubes (MWCNTs) are increasingly used in industry and in nanomedicine raising safety concerns, especially during unique life-stages such as pregnancy. We hypothesized that MWCNT exposure during pregnancy will increase vascular tissue contractile responses by increasing Rho kinase signaling. Pregnant (17-19 gestational days) and non-pregnant Sprague Dawley rats were exposed to 100 μg/kg of MWCNTs by intratracheal instillation or intravenous administration. Vasoactive responses of uterine, mesenteric, aortic and umbilical vessels were studied 24 hours post-exposure by wire myography. The contractile responses of the vessel segments were different between the pregnant and non-pregnant rats, following MWCNT exposure. Maximum stress generation in the uterine artery segments from the pregnant rats following pulmonary MWCNT exposure was increased in response to angiotensin II by 4.9 mN/mm² (+118%), as compared to the naïve response and by 2.6 mN/mm² (+40.7%) as compared to the vehicle exposed group. Following MWCNT exposure, serotonin induced approximately 4 mN/mm² increase in stress generation of the mesenteric artery from both pregnant and non-pregnant rats as compared to the vehicle response. A significant contribution of the dispersion medium was identified as inducing changes in the contractile properties following both pulmonary and intravenous exposure to MWCNTs. Wire myographic studies in the presence of a Rho kinase inhibitor and RhoA and Rho kinase mRNA/protein expression of rat aortic endothelial cells were unaltered following exposure to MWCNTs, suggesting absent/minimal contribution of Rho kinase to the enhanced contractile responses following MWCNT exposure. The reactivity of the umbilical vein was not changed; however, mean fetal weight gain was reduced with dispersion media and MWCNT exposure by both routes. These results suggest a susceptibility of the vasculature during gestation to MWCNT and their dispersion media-induced vasoconstriction, predisposing reduced fetal growth during pregnancy.

Inhibition of CXCR7 extends survival following irradiation of brain tumours in mice and rats

Background:

In experimental models of glioblastoma multiforme (GBM), irradiation (IR) induces local expression of the chemokine CXCL12/SDF-1, which promotes tumour recurrence. The role of CXCR7, the high-affinity receptor for CXCL12, in the tumour's response to IR has not been addressed.

Methods:

We tested CXCR7 inhibitors for their effects on tumour growth and/or animal survival post IR in three rodent GBM models. We used immunohistochemistry to determine where CXCR7 protein is expressed in the tumours and in human GBM samples. We used neurosphere formation assays with human GBM xenografts to determine whether CXCR7 is required for cancer stem cell (CSC) activity in vitro.

Results:

CXCR7 was detected on tumour cells and/or tumour-associated vasculature in the rodent models and in human GBM. In human GBM, CXCR7 expression increased with glioma grade and was spatially associated with CXCL12 and CXCL11/I-TAC. In the rodent GBM models, pharmacological inhibition of CXCR7 post IR caused tumour regression, blocked tumour recurrence, and/or substantially prolonged survival. CXCR7 expression levels on human GBM xenograft cells correlated with neurosphere-forming activity, and a CXCR7 inhibitor blocked sphere formation by sorted CSCs.

Conclusions:

These results indicate that CXCR7 inhibitors could block GBM tumour recurrence after IR, perhaps by interfering with CSCs.

Origins of Stabilization and Evidence for Charge Delocalization in the Bicyclo[3.2.1]octadienyl Anion and Related Species

Bridged bicyclic allylic anions with ethene and allyl units in proximity possess enhanced stability over analogues lacking the ethene bridge. Experimental observations have encouraged much computational effort, and for many years claims for homoaromatic behaviour in anions were disputed. More recently, and especially with the advent of quantum mechanics methods that assess magnetic susceptibility, homoaromaticity has become accepted. This paper provides a review of work on this topic to date, and additional density functional theory calculations with the purpose of providing a general overview. The presence of homoaromaticity in anions of this class is supported, and their stability is augmented by inductive and counterion effects.

CADASIL presenting with a behavioural variant frontotemporal dementia phenotype

The behavioural variant of frontotemporal dementia (bvFTD) is characterised by personality change with a decline in cognition. We describe two patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukencephalopathy (CADASIL) who presented with behavioural phenotypes similar to bvFTD. The first patient presented with progressive personality and behavioural change, had florid white matter hyperintensity, and had a novel missense mutation C366W in exon 7 of the Notch3 gene. The second patient presented with progressive memory impairment and marked personality changes after a transient ischaemic attack. In this second patient, the radiological features were subtle and only the family history of stroke prompted testing for CADASIL using Notch3 genotyping. We present these patients to demonstrate that CADASIL may mimic bvFTD, with little clinical or radiological evidence to distinguish the two. CADASIL may be an under-recognised diagnosis in apparent bvFTD. Screening Notch3 in a substantial and unselected cohort of frontotemporal dementia patients might be appropriate to investigate this possibility.

Abstract 106: Transintestinal Cholesterol Excretion and Macrophage Reverse Cholesterol Transport are not Stimulated in Hepatic ABCG8 Knockdown Mice Treated with an LXR Agonist

Transintestinal cholesterol excretion (TICE) is a recently discovered pathway by which cholesterol travels from plasma to the small intestine for direct excretion into the feces. Hallmarks of animal models with TICE include severely diminished biliary cholesterol secretion but near normal levels of hepatic cholesterol and fecal neutral sterol excretion. Using an ATP binding cassette transporter G8 (ABCG8) antisense oligonucleotide (ASO) to knock down ABCG8 specifically in liver (G8 HKD ), we created a novel mouse model with significantly decreased biliary cholesterol excretion but a 658% increase in hepatic cholesterol accumulation and a 78% reduction in fecal neutral sterol excretion, indicating a dysfunction in the TICE pathway. LXR agonists have previously been shown to stimulate the TICE pathway. In order to more definitively prove the TICE pathway was disfunctional in G8 HKD mice, we treated wild type (WT) and G8 HKD mice with the LXR agonist T0901317 and measured markers of TICE stimulation. As expected, in WT mice, T0901317 doubled biliary cholesterol concentrations. A similar effect was seen in G8 HKD mice treated with T0901317, but biliary cholesterol concentrations remained significantly less than their WT counterparts. These levels of biliary cholesterol closely mirrored hepatic ABCG8 mRNA expression. T0901317 stimulated fecal neutral sterol excretion by >1000% in wild type mice but only by 190% in G8 HKD mice. These data indicate that TICE is disfunctional in G8 HDK mice since the pathway was not stimulated to the same extent in WT and G8 HKD mice by an LXR agonist. Some controversy remains over whether the TICE pathway transports macrophage derived cholesterol. In order to address this issue, we performed a macrophage RCT assay on WT and TICE disfunctional G8 HKD mice. T0901317 stimulated macrophage RCT (fecal neutral sterol 3H dpm) by >2300% in wild type mice but only by 370% in G8 HKD mice. T0901317 increased fecal acidic sterol 3H count by 65-75% in both wild type and G8 HKD mice. These results indicate that macrophage RCT is impaired when the TICE pathway is decreased. In sum, our data shows that hepatic ABCG8 plays a key role in the TICE pathway and that impairing the TICE pathway through hepatic ABCG8 knockdown causes decreased macrophage RCT.

Abstract 396: Acute Hepatic ACAT2 Knockdown Transiently Increases Plasma and Hepatic Free Cholesterol and Fecal Neutral Sterol Excretion

In spite of the advent of statins, atherosclerotic coronary vascular disease (ASCVD) remains the number one killer of Americans. A way to reduce LDL cholesterol, the primary risk factor of ASCVD, is to increase cholesterol excretion from the body. Our group and others have recently found that cholesterol excretion can be facilitated by both biliary and non-biliary pathways. The lipoprotein that delivers cholesterol from the liver through the plasma to the small intestine for transintestinal cholesterol excretion (TICE) is not yet known. We have previously shown that chronic knockdown in mice of hepatic acyl-CoA cholesterol acyltransferase 2 (ACAT2), a cellular enzyme that converts free cholesterol (FC) into cholesteryl ester (CE), appeared to cause the formation of hepatic apoB-containing lipoproteins that preferentially trafficked cholesterol to the small intestine for TICE. We tested the hypothesis that the plasma concentration of TICE-competent, apoB-containing lipoproteins, could be increased by preloading the liver with cholesterol and then acutely depleting the cholesterol by knocking down hepatic ACAT2 with antisense oligonucleotides (ASO). After feeding a high cholesterol (0.2% wt/wt) diet for six weeks, C57BL/6 mice were treated with control non-targeting ASO or ACAT2 ASO for one or two weeks. After only one week of ACAT2 knockdown (ACAT2KD) hepatic ACAT2 protein expression was decreased nearly 80%. This translated into a 50% decrease in hepatic CE concentration in conjunction with a rarely seen 2-fold increase in hepatic FC concentration. Acute hepatic ACAT2KD increased plasma FC levels by 25%, which subsided after two weeks of treatment. The increased plasma FC was primarily associated with large and small LDL. After one week of hepatic ACAT2KD mice had a minor, non-significant increase in biliary cholesterol levels but had a 2-fold increase in fecal neutral sterol (FNS) excretion. In summary our data show that when CE is rapidly cleared from the liver, FNS levels dramatically increase with a transient increase in hepatic and plasma FC levels. We believe that in the ACAT2KD mice the increased plasma FC associated with LDL is feeding into TICE thus resulting in increased FNS.

Effects of surface functional groups on the formation of nanoparticle-protein corona

Herein, we examined the dependence of protein adsorption on the nanoparticle surface in the presence of functional groups. Our UV-visible spectrophotometry, transmission electron microscopy, infrared spectroscopy, and dynamic light scattering measurements evidently suggested that the functional groups play an important role in the formation of nanoparticle-protein corona. We found that uncoated and surfactant-free silver nanoparticles derived from a laser ablation process promoted a maximum protein (bovine serum albumin) coating due to increased changes in entropy. On the other hand, bovine serum albumin displayed a relatively lower affinity for electrostatically stabilized nanoparticles due to the constrained entropy changes.

Long-term follow-up of the Medical Research Council CLASICC trial of conventional versus laparoscopically assisted resection in colorectal cancer

BACKGROUND

Laparoscopic resection is used widely in the management of colorectal cancer; however, the data on long-term outcomes, particularly those related to rectal cancer, are limited. The results of long-term follow-up of the UK Medical Research Council trial of laparoscopically assisted versus open surgery for colorectal cancer are presented.

METHODS

A total of 794 patients from 27 UK centres were randomized to laparoscopic or open surgery in a 2:1 ratio between 1996 and 2002. Long-term follow-up data were analysed to determine differences in survival outcomes and recurrences for intention-to-treat and actual treatment groups.

RESULTS

Median follow-up of all patients was 62·9 (interquartile range 22·9 - 92·8) months. There were no statistically significant differences between open and laparoscopic groups in overall survival (78·3 (95 per cent confidence interval (c.i.) 65·8 to 106·6) versus 82·7 (69·1 to 94·8) months respectively; P = 0·780) and disease-free survival (DFS) (89·5 (67·1 to 121·7) versus 77·0 (63·3 to 94·0) months; P = 0·589). In colonic cancer intraoperative conversions to open surgery were associated with worse overall survival (hazard ratio (HR) 2·28, 95 per cent c.i. 1·47 to 3·53; P < 0·001) and DFS (HR 2·20, 1·31 to 3·67; P = 0·007). In terms of recurrence, no significant differences were observed by randomized procedure. However, at 10 years, right colonic cancers showed an increased propensity for local recurrence compared with left colonic cancers: 14·7 versus 5·2 per cent (difference 9·5 (95 per cent c.i. 2·3 to 16·6) per cent; P = 0·019).

CONCLUSION

Long-term results continue to support the use of laparoscopic surgery for both colonic and rectal cancer.

Space-time resolved simulation of femtosecond nonlinear light-matter interactions using a holistic quantum atomic model: application to near-threshold harmonics

We introduce a new computational approach for femtosecond pulse propagation in the transparency region of gases that permits full resolution in three space dimensions plus time while fully incorporating quantum coherent effects such as high-harmonic generation and strong-field ionization in a holistic fashion. This is achieved by utilizing a one-dimensional model atom with a delta-function potential which allows for a closed-form solution for the nonlinear optical response due to ground-state to continuum transitions. It side-steps evaluation of the wave function, and offers more than one hundred-fold reduction in computation time in comparison to direct solution of the atomic Schrödinger equation. To illustrate the capability of our new computational approach, we apply it to the example of near-threshold harmonic generation in Xenon, and we also present a qualitative comparison between our model and results from an in-house experiment on extreme ultraviolet generation in a femtosecond enhancement cavity.

Palladium-catalyzed substitution and cross-coupling of benzylic fluorides

Benzylic fluorides are suitable substrates for Pd(0)-catalyzed Tsuji-Trost substitution using carbon, nitrogen, oxygen, and sulfur nucleophiles and for cross-coupling with phenylboronic acid. For the bifunctional substrate 4-chlorobenzyl fluoride, fine-tuning of the reaction conditions allows for the regioselective displacement of either the chlorine or fluorine substituent. The leaving group ability of fluoride vs other groups displaced in substitution is CF(3)CO(2) ≈ p-NO(2)C(6)H(4)CO(2) ≈ OCO(2)CH(3) > F > CH(3)CO(2), a ranking similar to allylic fluorides under Pd catalysis.