Metastatic
tumor cells in body fluids are important targets for treatment, and critical
surrogate markers for evaluating
cancer prognosis and therapeutic response. Here we report, for the first time, that live metastatic
tumor cells in blood samples from mice bearing human
tumor xenografts and in blood and cerebrospinal fluid samples from patients with
cancer were successfully detected using a
tumor cell-specific recombinant vaccinia virus (VACV). In contrast to the FDA-approved CellSearch system, VACV detects
circulating tumor cells (CTCs) in a
cancer biomarker-independent manner, thus, free of any bias related to the use of
antibodies, and can be potentially a universal system for detection of live CTCs of any
tumor type, not limited to CTCs of epithelial origin. Furthermore, we demonstrate for the first time that VACV was effective in preventing and reducing
circulating tumor cells in mice bearing human
tumor xenografts. Importantly, a single intra-peritoneal delivery of VACV resulted in a dramatic decline in the number of
tumor cells in the ascitic fluid from a patient with
gastric cancer. Taken together, these results suggest VACV to be a useful tool for quantitative detection of live
tumor cells in liquid biopsies as well as a potentially effective treatment for reducing or eliminating live
tumor cells in body fluids of patients with metastatic disease.