br are required per dose
are required per dose, creating excessive expense. Moreover, higher doses required to achieve therapeutic benefit can yield substantial tox-icities and prohibit effective dosing strategies. For instance, clinical trial results confirm that oncolytic viral therapy using poxvirus-based and other viral vectors is safe and demonstrates clear biologic activity against cancers refractory to traditional adjuvant therapies.7,8 Howev-er, a current poxvirus in clinical trials requires three doses of 109 plaque-forming units (PFU) of virus, making therapy extremely expensive and making toxicity more likely.9 Thus, more potent, tumor-selective viruses capable of more efficient viral replication are needed. This project aimed to characterize a novel chimeric poxvirus (CF33-hNIS) that we created via an innovative recombina-tion technique. This virus is potent, replicates efficiently, and allows for additional deliverables in the form of noninvasive imaging and therapeutic synergy.
To noninvasively track viral replication in real time and facilitate syn-ergy with therapeutic radioisotopes, CF33-hNIS has been engineered to encode a human sodium iodide symporter (hNIS). Our group and others have established that viral infection and proliferation can be noninvasively imaged in vivo using a number of different reporter
genes.10,11 hNIS is able to facilitate both imaging and synergistic cell kill via radioisotope uptake.12,13 Thus, CF33-hNIS replication
and efficacy can be both tracked (via positron emission tomography [PET] or single-photon emission computed tomography [SPECT] imaging) and enhanced (via addition of radioisotopes, which can ablate Acetylcysteine surrounding an infected cell that takes in the isotope). Clinically, this means that one day a patient could receive a dose of virus, be imaged several days later to identify known and unknown sites of tumor via viral replication, and then receive adjunctive radio-isotope that could augment cytotoxic effects of already replicating oncolytic virus.
Correspondence: Susanne G. Warner, MD, Department of Surgery, Division of
Surgical Oncology, City of Hope National Medical Center, 1500 E. Duarte Road,
E-mail: [email protected]
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Figure 1. Chimeric Orthopoxvirus CF33 Expressing hNIS
(A) Schematic represents tk locus insertion of hNIS at tk locus under the control of the synthetic early (SE) promoter. (B) Immunofluorescence demonstrates co-staining with
vaccinia (red) and hNIS (green) at 24 h post-infection with CF33-hNIS at MOI 0.01 in HCT116 (upper panel) and HT29 (lower panel) cells magnified at 60. DAPI (blue) was used for nuclei staining. (C) Schema depicting insertion of GFP on tk locus, instead of hNIS, to generate CF33-GFP. (D) Viral replication in HCT116 and HT29 at an MOI of 0.01. Bars indicate SD. hNIS, human sodium iodide symporter; PSE, synthetic early promoter.
This study sought to characterize the efficacy of CF33-hNIS against colon cancer in vitro and in vivo, and to evaluate its capability to induce in vivo radioisotope uptake. This study further investigates cell death patterns of CF33-hNIS against preclinical colorectal cancer models and the use of radioisotopes for synergistic tumor destruction in vitro and in vivo. We hypothesized that CF33-hNIS is tumor-tropic, and that viral replication is imageable in real time. We further hypothesized that viral infection would facilitate synergy with thera-peutic radioisotopes, and that cell death from viral infection would occur via mechanisms commonly attributed to poxvirus infection.
CF33-hNIS Infects, Replicates in, and Kills Colon Cancer Cells