Abstract 2392: A novel approach for detecting viable and tissue-specific circulating tumor cells

Abstract

Abstract Circulating tumor cells (CTCs) offer a new strategy to access cancer tissue through a simple blood sample. CTCs levels can be predictive of overall survival in patients with metastatic cancers and changes in CTC levels following therapy can be indicative of therapeutic response. Moreover, CTCs may provide a means to select patients for specific therapeutic approaches by identifying active or susceptible pathways. However, most of the current methods for detecting CTCs have limitations including the need for specialized equipment, the reliance on cell capture through cell surface markers such as EpCAM, limited sensitivity, the inability to distinguish cancer from normal, tissue type, active pathways, or cell viability. Here we present a novel CTC detection approach which applies tissue-selective replicating adenoviruses and highly sensitive secreted reporters. These Circulating Tumor Cell Reporter Viruses (CTC-RVs) were generated by replacing the early viral E1A gene promoter with the prostate specific probasin promoter and prostate specific antigen enhancer (PSE-PBN). The secreted reporter gene, humanized metridia luciferase (hMLuc), was incorporated into the viral major late transcriptional unit, at the fiber gene locus, to limit reporter expression to only those cells in which the virus has replicated. Cells from total blood, including mononuclear cells and CTCs, are placed in tissue culture media and infected with the CTC-RV. After three days, viral replication dramatically amplifies reporter levels within infected prostate cancer cells with active Androgen Receptor pathways leading to the secretion of the bioluminescent reporter. Non-prostatic cells will not amplify the virus or express the reporter gene. LNCaP cellular dilution study results show that as few as five CTCs per million lymphocytes cells could be readily detected without any cell isolation. LNCaP cells diluted in healthy volunteer blood samples identified the optimal time and dosing conditions. Initial studies in clinical samples support the detection of viable CTCs with this assay. This new approach offers a means to quantify live CTC levels in a tissue-specific manner, without the need for cell capture, through the use of a secreted signal which can be detected separate from the large blood cell population. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2392. doi:1538-7445.AM2012-2392