Single-Stranded DNA with Internal Base Modifications Mediates Highly Efficient Gene Insertion in Primary Cells

Single-stranded DNA (ssDNA) templates along with Cas9 have been used for gene insertion but suffer from low efficiency. Here, we show that ssDNA with chemical modifications in 10-17% of internal bases (eDNA) is compatible with the homologous recombination machinery. Moreover, eDNA templates improve gene insertion by 2-3 fold compared to unmodified and end-modified ssDNA in airway basal stem cells (ABCs), hematopoietic stem and progenitor cells (HSPCs), T-cells and endothelial cells. Over 50% of alleles showed gene insertion in three clinically relevant loci (CFTR, HBB, and CCR5) in ABCs using eDNA and up to 70% of alleles showed gene insertion in the HBB locus in HSPCs. This level of correction is therapeutically relevant and is comparable to adeno-associated virus-based templates. Knocking out TREX1 nuclease improved gene insertion using unmodified ssDNA but not eDNA suggesting that chemical modifications inhibit TREX1. This approach can be used for therapeutic applications and biological modeling.

WE-C-217BCD-11: Coupled Radiative and Optical Geant4 Simulation of MV EPIDs Based on Thick Pixelated Scintillating Crystals

PURPOSE

One way to greatly reduce the incidence of metal artifacts produced in kilovoltage (kV) CT images is by using megavoltage (MV) photons that penetrate high-Z objects, thus providing a measurable signal. For do se-efficient imaging, a high detective quantum efficiency (DQE) MV detector is desired. This study validates the coupled radiation and optical Geant4 simulation results against experimental data from various prototype pixelated scintillator MV detectors and determines the essential optical parameters which control the detector performance.

METHODS

Experimental data obtained with a 6MV radiation source from 8 different detectors was considered. The detectors used CsI, CdW and BGO as scintillating crystals and polystyrene septal wall material. Accurate Geant4 models of the detectors were implemented and coupled radiation and optical simulations were performed. The unknown optical properties of the models were determined by minimizing the difference between the modulation transfer functions (MTF) of the simulated data obtained with the slanted slit technique and the experimental MTFs. With the set of optical properties fixed, further simulation validation was performed against the experimental normalized noise power spectrum (NNPS(f)) and the experimental DQE(f) curves for each detector. All the simulations were performed on a computer cluster deployed on the Amazon EC2 platform.

RESULTS

The optimal values for the free optical parameters are 10%, 95% and 90% for the top surface reflectivity, the crystal-sept a surface reflectivity, and the Lambertian component contribution to the reflected beam from the crystal-septa interface respectively. The absolute difference between experimental and simulated data was below 10% for all the data sets.

CONCLUSIONS

To our knowledge this study is the first to present a full optical and radiative DQE(f) model using Geant4 that shows an excellent match with experimental data. The model indicates that improved performance can be obtained using more specular septa which are optically opaque. Support: NIH-T32-CA09695, NIH-1R01CA138426 NIH T32-CA09695, NIH R01- CA138426, Several authors work for Varian Medical Systems.

Use of early primary tumor response to predict overall survival in patients with metastatic RCC undergoing treatment with sunitinib

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Background: In metastatic renal cell carcinoma (mRCC) patients treated with sunitinib and the primary tumor in situ, there is minimal predictive data available to help guide clinicians during treatment with targeted therapy. In prior studies, early primary tumor response (PTR) was associated with improved overall PTR, but the effect on overall survival (OS) is unknown. The purpose of our study was to evaluate whether early PTR was associated with improved OS in mRCC patients undergoing treatment with sunitinib.

Methods: We reviewed our institutional database to identify patients with mRCC treated with sunitinib with primary tumor in situ. Clinical and pathological data were collected for each patient. Sequential abdominal CT or MRI scans were reviewed to evaluate PTR. Early PTR was defined as ≥ 10% decrease in tumor diameter within the first 90 days of treatment. Univariable and multivariable stepwise Cox proportional hazards regression analysis were performed to identify predictors of OS in these patients.

Results: 75 consecutive patients were identified between 2005 and 2009 with a median follow-up of 15 months. 24 patients exhibited an early PTR; median maximum response 23.1% (range: −53.4, −10.2) and decrease in primary tumor diameter at a median of 90.5 days. Early PTR was associated with a decreased risk of death on multivariate analysis (HR: 0.18; 95% CI 0.05, 0.62, p<0.01). In addition, median OS was improved in patients with an early PTR (30.2 vs. 12.7 months). Independent predictors of decreased survival on multivariate analysis included local symptoms, multiple bone metastases, clinical evidence of venous thrombus, LDH > upper limit of normal, and >2 visceral metastatic sites.

Conclusions: Early PTR ≥ 10% is associated with improved survival, better response in metastatic sites, and better overall PTR in patients with mRCC. Future studies should consider this variable when evaluating sunitinib in mRCC treatment.

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Forced expression of a constitutively active form of Stat3 in mouse epidermis enhances malignant progression of skin tumors induced by two-stage carcinogenesis

Recently, our laboratory demonstrated that Stat3 is required for the de novo development of chemically-induced skin tumors. We have further investigated the role of Stat3 in epithelial carcinogenesis using mice in which the expression of a constitutively active/dimerized form of Stat3 (Stat3C) is targeted to the proliferative compartment of epidermis (referred to as K5.Stat3C transgenic mice). Keratinocytes from K5.Stat3C mice showed increased survival following exposure to 7,12-dimethylbenz[a]anthracene (DMBA) and enhanced proliferation following exposure to 12-O-tetradecanoylphorbol-13-acetate (TPA). In two-stage chemical carcinogenesis experiments using DMBA as the tumor initiator and TPA as the promoter, K5.Stat3C mice developed skin tumors with a shorter latency and in much greater number compared to non-transgenic littermates. Remarkably, 100% of the skin tumors that developed in K5.Stat3C transgenic mice bypassed the premalignant stage and were initially diagnosed as carcinoma in situ which rapidly progressed to squamous cell carcinoma (SCC). These tumors were highly vascularized, poorly differentiated and invasive and loss of expression of K10, filaggrin and E-cadherin was observed by 20 weeks. Finally, overexpression of Stat3C in a papilloma cell line led to enhanced cell migration and enhanced invasion through Matrigel in both the absence and presence of growth factors. In addition to its critical role in early stages of epithelial carcinogenesis, the current study reveals a novel role for Stat3 in driving malignant progression of skin tumors in vivo.

Optimization of the Continuous Wavelet Transform for DSP Processor Implementation

The redundant wavelet transform is an effective tool when emphasis is on the analysis of non-stationary signals and on localization and characterization of singularities. Here we describe an optimized method to implement a B-spline based redundant wavelet transform (RWT) on a Digital Signal Processor (DSP) for integer scales. Expressions are derived to give an exact operation count at any integer scale m for any B-spline of order n. Finally experimental results are given using cubic b-spline as scaling function and first-and second-order derivative of B-splines as wavelets. It has been shown that optimized method improves the execution speed over the standard method by 20-28%.

Surface free energy effect on bacterial retention

Bacterial infection is one of the most frequent and severe complications in the long-term effectiveness of medical implants and devices, greatly increasing treatment cost and inconvenience to the patient. Surface physical and chemical properties are known to influence the extent and form of bacterial infection, although the exact correlation with specific properties is difficult due to the complexity of the system. One approach in the attempt to reduce the bacterial colonisation is to modify the surface energy and chemistry, so as to influence the interactions between the surface and the bacteria that come into contact with it. Five types of coatings were investigated in this study, together with silicone, and polished and non-polished stainless steel 316L. Surfaces were tested for retention of Pseudomonas aeruginosa AK1 after 1h. A good correlation (>90%) was found between P. aeruginosa AK1 retention and total surface free energy, as well as its polar and dispersive components. The minimum level of P. aeruginosa AK1 retention was found for a range of total surface free energy in the range 20-27 mN/m.

Early disturbance of microvascular function precedes chemotherapy-induced intestinal injury

Intestinal injury 4-48 hr after cytotoxic therapy (etoposide phosphate, 100 mg/kg body weight [bw], intravenously [i.v.]) was studied in rats using ligated intestinal loops. Chromium-51 ethylenediaminetetraacetic acid ((51)Cr-EDTA) and rubidium-86 chloride ((86)RbCl) were deposited intraluminally to determine the extent of the increase in intestinal permeability and ion channel disruption. Evans Blue (EB) was used for detection of endothelial leakage. Intestinal morphology was documented. Endothelial dysfunction, as observed by an increased extravasation of EB, was evident already 4 hr after cytotoxic therapy. Intestinal epithelial injury, as observed by an increase in (51)Cr-EDTA permeation and a decrease in (86)Rb absorption, occurred after 48 hr. Finally, histology disclosed a reduced crypt cell proliferation, displayed as a decrease in Ki67-positive cells. The findings suggest that, in the development of intestinal injury after cytotoxic therapy, endothelial disruption is an early event, whereafter epithelial dysfunction and crypt stem cell arrest occur. This knowledge could be of importance in the design of future intervention trials.

Delayed facial palsy following laser stapedectomy: in vitro study of facial nerve temperature

Delayed facial palsy following conventional stapes surgery is a rare event, but this complication appears to be more common when a laser is used. We have investigated the temperature in the facial canal during stapes surgery using a KTP laser or a microdrill in preserved human temporal bones. Thermocouples were placed in the facial canal and under the foot plate. The results show maximum rises in temperature of between 1.4 degrees C and 15.2 degrees C in the facial canal during laser surgery (mean 6.1 degrees C, SD 4.5 degrees C), but only between 0.45 degrees C and 2 degrees C during procedures in which a microdrill was used (mean 0.9 degrees C, SD 0.9 degrees C) (P = < 0.009). In addition, the facial nerve undergoes repeated heating and cooling cycles during the laser surgery. We conclude that heating of the facial nerve during laser surgery causes oedema, which in turn leads to compression of the nerve within its bony canal.