Colby Shad Thaxton

Biomarkers For Prostate Cancer

The detection of prostate cancer using a blood test has by many standards changed the face of the disease. Despite this tremendous success, there are limitations attributed to the use of prostate specific antigen (PSA) as a means to screen and detect prostate cancer. PSA, as its name implies, is not specific for prostate cancer and as such is often found elevated in other prostatic diseases/symptoms associated with the aging male. Clearly, more specific marker(s) that could identify which individuals actually have prostate cancer and differentiate them from those without the disease would be of tremendous value. The search for more accurate and clinically useful biomarkers of prostate cancer has been extensive. This has focused on individual markers, as well as groups of markers. Included among these are PSA isoforms, pathological indicators and stains, nucleic acids and others. This article highlights the discovery of PSA as a first blood‐based biomarker for prostate cancer detection, as well as other molecular biomarkers and their potential application in detection of the disease. J. Cell. Biochem. 108: 3–9, 2009.

Radiographic Parameters on Noncontrast Computerized Tomography Predictive of Shock Wave Lithotripsy Success

PURPOSE Accurate prediction of shock wave lithotripsy success for given patient and radiographic parameters will lead to improved selection of patients for shock wave lithotripsy vs more invasive treatment. In this study we determined which radiographic parameters are the most predictive of shock wave lithotripsy success, and present a method to incorporate these into current and future models based on nonradiographic parameters. MATERIALS AND METHODS A retrospective case-control study was performed to determine average, maximum and standard deviation of stone attenuation values, stone size and skin-to-stone distance on preoperative noncontrast computerized tomography for 220 patients successfully treated with shock wave lithotripsy and 105 patients in whom shock wave lithotripsy failed. RESULTS Average stone attenuation is the best independent predictor of shock wave lithotripsy success as determined by the Student t test (p <0.0001) and receiver operating characteristic curves. Odds and likelihood ratios are provided for shock wave lithotripsy success for incremental average HU cutoffs. An average HU cutoff can be established over which the refined probability of success is below an arbitrary minimally acceptable cutoff of a 60% stone-free rate. Using pre-test probabilities of shock wave lithotripsy success from nomograms in the literature, our data suggest that shock wave lithotripsy should be first line therapy for solitary 6 to 10 mm stones with an average stone attenuation of less than 1,000 and 640 HU for the proximal ureter and renal pelvis, respectively. CONCLUSIONS Average stone attenuation is a convenient radiographic measure that can be used to refine a known probability of shock wave lithotripsy success. Clinical HU cutoff guidelines can be determined based on current or future predictive nomograms based on other parameters.

A novel mouse model that develops spontaneous arthritis and is predisposed towards atherosclerosis

Objectives Patients with rheumatoid arthritis (RA) have a reduced life expectancy due to increased cardiovascular disease. The lack of a suitable animal model resembling both RA and atherosclerosis has hindered studies demonstrating a direct link between systemic inflammation in RA and the development of atherosclerosis. Our objective was to overcome this barrier by generating an animal model (K/BxAg7) that spontaneously develops both RA-like disease and atherosclerosis. Methods Arthritis severity was evaluated using clinical indices and immunohistochemical staining of ankle joint specimens. Aortic atherosclerosis was delineated via Sudan IV staining and immunohistochemical analysis. Serum cholesterol and lipoprotein levels were measured using enzymatic assays. Serum levels of cytokines, chemokines and adipokines were determined by Luminex assays. Results K/BxAg7 mice developed a destructive arthropathy followed by prominent aortic atherosclerosis. These animals also displayed dyslipidaemia, characterised by reduced serum levels of total cholesterol and high-density lipoprotein, and increased low-density lipoprotein (LDL)/vLDL compared with control mice. Further, there were higher levels of circulating inflammatory mediators, such as interleukin-6, sRANKL and CCL5 in atherosclerotic K/BxAg7 mice compared with controls. Treatment with etanercept reduced arthritis and atherosclerosis development in K/BxAg7 mice. Conclusions K/BxAg7 mice recapitulate the same sequence of events occurring in patients with RA, namely an erosive, inflammatory arthritis followed by atherosclerosis. These data suggest that the K/BxAg7 mouse is a novel system for investigating the interplay between systemic inflammation occurring in RA and the development of atherosclerosis.

High-density lipoproteins for the systemic delivery of short interfering RNA

Introduction: RNA interference (RNAi) is a powerful mechanism for gene silencing with the potential to greatly impact the development of new therapies for many human diseases. Short interfering RNAs (siRNAs) may be the ideal molecules for therapeutic RNAi. However, therapeutic siRNAs face significant challenges that must be overcome prior to widespread clinical use. Many efforts have been made to overcome the hurdles associated with systemic administration of siRNA; however, current approaches are still limited. As such, there is an urgent need to develop new strategies for siRNA delivery that have the potential to impact a broad spectrum of systemic diseases. Areas covered: This review focuses on the promise of siRNA therapies and highlights current siRNA delivery methods. With an eye toward new strategies, this review first introduces high-density lipoprotein (HDL) and describes its natural biological functions, and then transitions into how HDLs may provide significant opportunities as next-generation siRNA delivery vehicles. Importantly, this review describes how synthetic HDLs leverage the natural ability of HDL to stabilize and deliver siRNAs. Expert opinion: HDLs are natural nanoparticles that are critical to understanding the systemic delivery of therapeutic nucleic acids, like siRNA. Methods to synthesize biomimetic HDLs are being explored, and data demonstrate that this type of delivery vehicle may be highly beneficial for targeted and efficacious systemic delivery of siRNAs.

Synthetic high-density lipoprotein-like nanoparticles for cancer therapy.

High-density lipoproteins (HDLs) are a diverse group of natural nanoparticles that are most well known for their role in cholesterol transport. However, HDLs have diverse functions that provide significant opportunities for cancer therapy. Presented is a focused review of the ways that synthetic versions of HDL have been used as targeted therapies for cancer, and as vehicles for the delivery of diverse therapeutic cargo to cancer cells. As such, synthetic HDLs are likely to play a central role in the development of next-generation cancer therapies.

Properties of Native High-Density Lipoproteins Inspire Synthesis of Actively Targeted In Vivo siRNA Delivery Vehicles

Efficient systemic administration of therapeutic short interfering RNA (siRNA) is challenging. High-density lipoproteins (HDL) are natural in vivo RNA delivery vehicles. Specifically, native HDLs: 1) Load single-stranded RNA; 2) Are anionic, which requires charge reconciliation between the RNA and HDL, and 3) Actively target scavenger receptor type B-1 (SR-B1) to deliver RNA. Emphasizing these particular parameters, we employed templated lipoprotein particles (TLP), mimics of spherical HDLs, and self-assembled them with single-stranded complements of, presumably, any highly unmodified siRNA duplex pair after formulation with a cationic lipid. Resulting siRNA templated lipoprotein particles (siRNA-TLP) are anionic and tunable with regard to RNA assembly and function. Data demonstrate that the siRNA-TLPs actively target SR-B1 to potently reduce androgen receptor (AR) and enhancer of zeste homolog 2 (EZH2) proteins in multiple cancer cell lines. Systemic administration of siRNA-TLPs demonstrated no off-target toxicity and significantly reduced the growth of prostate cancer xenografts. Thus, native HDLs inspired the synthesis of a hybrid siRNA delivery vehicle that can modularly load single-stranded RNA complements after charge reconciliation with a cationic lipid, and that function due to active targeting of SR-B1.

Systemically administered collagen‐targeted gold nanoparticles bind to arterial injury following vascular interventions

Surgical and endovascular therapies for severe atherosclerosis often fail due to the development of neointimal hyperplasia and arterial restenosis. Our objective was to synthesize, characterize, and evaluate the targeting specificity and biocompatibility of a novel systemically injected nanoparticle. We hypothesize that surface‐functionalization of gold nanoparticles (AuNPs) with a collagen‐targeting peptide will be biocompatible and target specifically to vascular injury. 13 nm AuNPs were surface functionalized with a peptide‐molecular fluorophore and targeted to collagen (T‐AuNP) or a scrambled peptide sequence (S‐AuNP). After rat carotid artery balloon injury and systemic injection of T‐AuNP or S‐AuNP, arteries and organs were harvested and assessed for binding specificity and biocompatibility. The T‐AuNP bound with specificity to vascular injury for a minimum of 24 h. No significant inflammation was evident locally at arterial injury or systemically in major organs. The T‐AuNP did not impact endothelial cell viability or induce apoptosis at the site of injury in vivo. No major changes were evident in hepatic or renal blood chemistry profiles. Herein, we synthesized a biocompatible nanoparticle that targets to vascular injury following systemic administration. These studies demonstrate proof‐of‐principle and serve as the foundation for further T‐AuNP optimization to realize systemic, targeted delivery of therapeutics to the sites of vascular injury.

Abstract 3672: Expression patterns of scavenger receptor B-1 (SR-B1) to guide biomimetic HDL gold nanoparticle therapy

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Introduction: Treatment options for many advanced cancers are fairly limited. New therapies that can open new paradigm are urgently needed. We have recently developed a novel synthetic biomimetic HDL gold nanoparticle (HDL NP) that demonstrated anti-tumor activity in cancer cells via apoptosis (Yang et al. PNAS, 2013) Its activity correlated with the expression of scavenger receptor-B1 (SR-B1) that binds to natural HDLs and HDL NPs. SR-B1 is a high-affinity HDL receptor that facilitates the bidirectional flux of free cholesterol and the transport of esterified cholesterol to cells. The mechanism of action of HDL NPs involved alterations in cholesterol flux and metabolism as well as cholesterol-based cell-signaling pathways. Understanding the expression patterns of SR-B1 in various human cancers can assist in developing HDL NP therapy to broader indications. Methods: We used Oncomine Research Edition public database to assess the gene expression levels of SR-B1 in various human cell lines, cancer tissues, and normal tissues. T test was use to compare cell line with the highest SR-B1 expression with the rest of cell lines of various tumor types. Also comparison was made between resected human cancer tissues and their counterpart normal tissues across various histologies. Each significant t test results from all publicly available array datasets within Oncomine were counted and compared among different tumor types. Results: First, we compared the mRNA levels of SR-B1 in human cancer tissues with those of normal tissues. Twenty different tumor types were included. Among 20 different datasets of renal cell carcinoma, 12 (60%) revealed statistically significant increase in SR-B1 expression in cancer compared with normal renal tissue samples. Other tumor types that showed ≥10% of databsets demonstrating the same pattern of expression were esophageal (44%, 4/9), melanoma (43%, 3/7), gastric (26%, 6/23), leukemia (21%, 6/29), lymphoma (20%, 6/30), colorectal (19%, 7/36), liver (15%, 2/13), and prostate cancer (15%, 3/20). Second, we compared the mRNA levels of SR-B1 across various human cancer cell lines. Among 17 different datasets that contain cancer cell lines including melanoma cell lines, melanoma was found to have the highest level of SR-B1 expression compared with the rest of the cell lines of various cancer types in 11 (65%) datasets. Other tumor types associated with ≥10% of datasets demonstrating the same highest level of SR-B1 expression were liver (33%, 4/12), kidney (12%, 2/17), and leukemia (11%, 2/19). Discussion: We found that renal cell carcinoma, melanoma, and hepatocellular carcinoma were among the cancers that expressed higher levels of SR-B1 compared with other cancers as well as with their normal tissues. These tumors merit further investigation as targets for HDL NP therapy either in the form of mono-therapy or in combination. Citation Format: Young Kwang Chae, Alan Pan, Denise Scholtens, Shuo Yang, Jonathan Rink, Colby S. Thaxton, Leo Gordon. Expression patterns of scavenger receptor B-1 (SR-B1) to guide biomimetic HDL gold nanoparticle therapy. [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 3672. doi:10.1158/1538-7445.AM2015-3672