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

Authors

  • Ping Wu,

    1. The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins School of Medicine, Baltimore, Maryland
    Current affiliation:
    1. Department of Urology, University of Texas Health Science Center at San Antonio, San Antonio, TX
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  • Lori J. Sokoll,

    1. The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins School of Medicine, Baltimore, Maryland
    2. The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland
    3. Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland
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  • Tarana A. Kudrolli,

    1. The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins School of Medicine, Baltimore, Maryland
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  • Wasim H. Chowdhury,

    1. The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins School of Medicine, Baltimore, Maryland
    Current affiliation:
    1. Department of Urology, University of Texas Health Science Center at San Antonio, San Antonio, TX
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  • Rong Ma,

    1. The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins School of Medicine, Baltimore, Maryland
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  • Minzhi M. Liu,

    1. The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins School of Medicine, Baltimore, Maryland
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  • Ronald Rodriguez,

    Corresponding author
    1. The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins School of Medicine, Baltimore, Maryland
    2. The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland
    Current affiliation:
    1. Department of Urology, University of Texas Health Science Center at San Antonio, San Antonio, TX
    • Correspondence to: Ronald Rodriguez, Department of Urology, University of Texas Health Science Center, 7703 Floyd Curl Drive, MC 7845, San Antonio, TX 78229-3900. E-mail: rodriguezr32@uthscsa.edu

      **Correspondence to: Shawn E. Lupold, Department of Urology,The Johns Hopkins School of Medicine, 600 N. Wolfe St., Marburg 205, Baltimore, MD 21287-2101. E-mail: slupold1@jhmi.edu

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  • Shawn E. Lupold

    Corresponding author
    1. The James Buchanan Brady Urological Institute and Department of Urology, The Johns Hopkins School of Medicine, Baltimore, Maryland
    2. The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland
    • Correspondence to: Ronald Rodriguez, Department of Urology, University of Texas Health Science Center, 7703 Floyd Curl Drive, MC 7845, San Antonio, TX 78229-3900. E-mail: rodriguezr32@uthscsa.edu

      **Correspondence to: Shawn E. Lupold, Department of Urology,The Johns Hopkins School of Medicine, 600 N. Wolfe St., Marburg 205, Baltimore, MD 21287-2101. E-mail: slupold1@jhmi.edu

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  • Ronald Rodriguez and Shawn E. Lupold contributed equally to this study.
  • Disclosure Statement: The authors have nothing to disclose.

Abstract

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. Prostate 74: 1286–1296, 2014. © 2014 Wiley Periodicals, Inc.

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