Abstract 4774: Engineering an oncolytic adenovirus to target CEA in colorectal cancer

• Published in: Cancer research (Chicago, Ill.) Ill.), 2019-07, Vol.79 (13_Supplement), p.4774-4774
• Main Author: Schaumburg, Jessica C.
• Format: Article
• Language: English
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/1538-7445.AM2019-4774

Colorectal cancer is the second leading cause of cancer-related deaths in the United States and the third most commonly diagnosed cancer overall. Screening methods can identify precancerous polyps before they progress, leading to five-year survival rates of 92%. However, if diagnosed in later stages the survival rates decrease to 12%. While treatment options are available for advanced stages, they remain inadequate to affect overall survival. Thus, new therapies are needed to improve treatment outcomes. Oncolytic virotherapy is a unique therapeutic approach in which a virus is genetically modified to target cancer cells while sparing normal tissue. Oncolytic virotherapy takes advantage of the lytic properties of the viral life cycle. These viruses are used replicate inside cancer cells, lyse them and spread to adjacent cells throughout the tumor. The adenovirus is a well-characterized vector that is easily manipulated and produced and is capable of infecting a wide range of cells. However, the endogenous receptor for adenovirus, the Coxsackie and adenovirus receptor (CXADR), is often downregulated in cancers, thus decreasing the ability to selectively infect cancer cells. In this study, an adenovirus was genetically engineered to present the single variable domain (VHH) derived from a camelid heavy chain antibody B2. The B2 antibody recognizes the human carcinoembryonic antigen (CEA), which is often overexpressed in a variety of cancers, including colorectal cancer. Here, the wild-type fiber and knob domain of the adenovirus fiber gene was replaced with a modified T4 fibritin fiber linked to the B2 VHH. To provide for visual tracking of adenovirus infection and biodistribution, a red fluorescent protein (RFP) marker gene was also fused to the capsid protein IX (pIX). This virus was rescued and amplified in the HEK293 F28 packaging cell line with a final round of amplification in HEK293 cells. The virus was purified by CsCl ultracentrifugation and dialysis. The resulting viral stock was titered and characterized for the presence of the modified fiber and knob. Subsequently, the vector was modified to express the human sodium-iodide symporter (NIS) transgene, to allow for noninvasive imaging of the adenovirus uptake and replication as well as radiotherapy using 131I. Further experiments will be completed to confirm viral selectivity for CEA and subsequent lysis of colorectal cancer cells. The results of this study will advance targeting oncolytic adenoviruse