Detecting cancers through tumor-activatable minicircles that lead to a detectable blood biomarker

• Published in: Proceedings of the National Academy of Sciences - PNAS 2015-03, Vol.112 (10), p.3068-3073
• Main Authors: Ronald, John A., Chuang, Hui-Yen, Dragulescu-Andrasi, Anca, Hori, Sharon S., Gambhir, Sanjiv S.
• Format: Article
• Language: English
• Subjects: Biological Sciences; Biomarkers; Biomarkers, Tumor - blood; Blood tests; Cancer; Humans; Metastasis; Neoplasms - blood; Neoplasms - diagnosis; ROC Curve; Tumors
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1414156112

Earlier detection of cancers can dramatically improve the efficacy of available treatment strategies. However, despite decades of effort on blood-based biomarker cancer detection, many promising endogenous biomarkers have failed clinically because of intractable problems such as highly variable background expression from nonmalignant tissues and tumor heterogeneity. In this work we present a tumor-detection strategy based on systemic administration of tumor-activatable minicircles that use the pan-tumor–specific Survivin promoter to drive expression of a secretable reporter that is detectable in the blood nearly exclusively in tumor-bearing subjects. After systemic administration we demonstrate a robust ability to differentiate mice bearing human melanoma metastases from tumor-free subjects for up to 2 wk simply by measuring blood reporter levels. Cumulative change in reporter levels also identified tumor-bearing subjects, and a receiver operator-characteristic curve analysis highlighted this test’s performance with an area of 0.918 ± 0.084. Lung tumor burden additionally correlated ( r ² = 0.714; P < 0.05) with cumulative reporter levels, indicating that determination of disease extent was possible. Continued development of our system could improve tumor detectability dramatically because of the temporally controlled, high reporter expression in tumors and nearly zero background from healthy tissues. Our strategy’s highly modular nature also allows it to be iteratively optimized over time to improve the test’s sensitivity and specificity. We envision this system could be used first in patients at high risk for tumor recurrence, followed by screening high-risk populations before tumor diagnosis, and, if proven safe and effective, eventually may have potential as a powerful cancer-screening tool for the general population. Significance Blood-based cancer diagnosis is highly attractive, but current strategies suffer because they rely on the detection of endogenous molecules that often are secreted into the circulation by both malignant and nonmalignant cells. One solution to this problem is to avoid nonmalignant tissue expression by artificially engineering tumor cells to express a unique reporter not normally expressed by any tissue. This study shows that systemic administration of nonviral safe vectors we call “tumor-activatable minicircles” allows one to distinguish tumor-bearing from tumor-free subjects reliably and to assess tumor burden simply by measu