A novel approach for detecting viable and tissue-specific circulating tumor cells through an adenovirus-based reporter vector.

BACKGROUND: Circulating tumor cells (CTCs) hold great promise as biomarkers and are a direct source of tumor cells through a simple blood draw. However, CTCs are rare and their detection requires sensitive and specific methods to overcome the overwhelming hematocyte population. Therefore, CTC detection remains technically challenging. METHODS: An assay was developed for detecting viable and tissue-specific CTCs using a tropism-enhanced and conditionally replicating reporter adenovirus (CTC-RV). Adenoviral replication was made prostate-specific by placing the E1A gene under the control of the probasin promoter and prostate-specific antigen enhancer (PSE-PBN). Viral tropism was expanded through capsid-displayed integrin targeting peptides. A secreted reporter, humanized Metridia Luciferase (hMLuc), was engineered for expression during the major late phase of viral replication. The assay involves red blood cell lysis, cell collection, viral infection, and subsequent quantification of reporter activity from cellular media. Assay and reporter stability, cell specificity and sensitivity were evaluated in cell dilution models in human blood. RESULTS: A conditionally replicating prostate-selective adenovirus reporter and CTC assay system were generated. The secreted reporter, MLuc, was found to be stable for at least 3 days under assay conditions. CTC detection, modeled by cell dilution in blood, was selective for androgen receptor positive prostate cancer (PCa) cells. Serial dilution demonstrated assay linearity and sensitivity to as few as three cells. Prostate cancer cell viability declined after several hours in anticoagulated blood at ambient temperatures. CONCLUSIONS: Conditionally replicative adenoviral vectors and secreted reporters offer a functional method to detect viable CTCs with cell specificity and high sensitivity.

CAR- or CD46-dependent TRAIL-adenoviral vector induced apoptosis in lung cancer cells / 中国肿瘤生物治疗杂志

Objective: To observe the effects of recombinant adenovirus TRAIL (AdS-TRAIL & Ad5F35-TRAIL) on apoptosis of non-small cell lung (NSCLC) cells, so as to assess the value of Ad-TRAIL in gene therapy of NSCLC. Meth-ods: CAR and CD46 expression levels in lung cancer cell lines (A549, Z793, QG56 and NCI-H520) and the primary lung cancer cells from samples of 10 NSCLC patients were assayed by flow cytometry analysis. The lung cancer cell lines and primary lung cancer cells were infected with Ad5-TRAIL & Ad5F35-TRAIL adenoviral vectors at MOI 10 or 50, re-spectively; the percentage of apoptosis cells labeled by Annexin V-FITC in different cells were measured by flow cytometry 48 h after transfection. Results: The expression of CD46 were higher than that of CAR in all the lung cancer lines (A549, Z793, QG56 and NCI-H520) and the primary lung cancer cells. Significant apoptosis was observed in Z793 and QG56 cells transfected with Ad5-TRAIL or Ad5F35-TRAIL at MOI 10, with the apoptosis rate being (1.76±2.10)% (Ad5-TRAIL), (15.96±2.89) % (Ad5F35-THAIL) and (6.05±1.58) % (Ad5-TRAIL), (10.11±1.26) % (Ad5F35-TRAIL), respectively, compared to no adenovirus-transfected cells ([2.33±0.37] % and [5.95±1.89]%, respectively, P < 0.05). Less than 10% of apoptosis cells were detected in NCI-H520 cells transfected with Ad5- or Ad5F35-TRAIL at MOI 50 ([12.89±3.2] % for AdS-TRAIL and [9.08±1.35]% for Ad5F35-TRAIL, respectively) compared to no adenovirus-transfected cells ([7.04±2.17] %, P > 0.05). Moreover, apoptosis induced by Ad5- or Ad5F35-TRAIL transfection in A549 cells was not detected both at MOI 10 and 50. About half of the primary lung cancer cells from 10 patients induced apoptosis after transfected with Ad5-TRAIL or Ad5F35-TRAIL vector. A higher percentage of apoptotic cells were found in Ad5F35-TRAIL group than those in Ad5-TRAIL and control groups. Conclusion: Ad5-TRAIL can induce apoptosis of NSCLC cells in vitro, and Ad5F35-TRAIL is more potent than Ad5-TRAIL, so Ad5F35-TRAIL is more suitable for gene therapy of NSCLC.

Enhancement of Adenoviral Transduction and Immunogenecity of Transgenes by Soluble Coxsackie and Adenovirus Receptor-TAT Fusion Protein on Dendritic Cells

BACKGROUND: Investigating strategy to enhance efficiency of gene transfer via adenovirus is critical to sustain gene expression in targeted cells or tissues to regulate immune responses. However, the use of adenovirus as a gene delivery method has been limited by the native tropism of the virus. In this study, the critical parameter is to improve the efficient binding of viral particles to the plasma membrane prior to cellular uptake. METHODS: Human immunodeficiency virus (HIV-1) trans-acting activator of transcription (TAT), a protein transduction domain, was fused to the ectodomain of the coxsackie-adenovirus receptor (CAR). The CAR-TAT protein was produced from a Drosophila Schneider 2 cells (S2) transfected with CAR-TAT genes. The function of CAR- TAT was analyzed the efficiency of adenoviral gene transfer by flow cytometry, and then immunizing AdVGFP with CAR-TAT was transduced on dendritic cells (DCs). RESULTS: S2 transfectants secreting CAR-TAT fusion protein has been stable over a period of 6 months and its expression was verified by western blot. Addition of CAR-TAT induced higher transduction efficiency for AdVGFP at every MOI tested. When mice were vaccinated with DC of which adenoviral transduction was mediated by CAR-TAT, the number of IFN-gamma secreting T-cells was increased as compared with those DCs transduced without CAR-TAT. CONCLUSION: Our data provide evidence that CAR-TAT fusion protein enhances adenoviral transduction and immunogenecity of transgenes on DCs and may influence on the development of adenoviral- mediated anti-tumor immunotherapy.