Colorectal cancer is among the most common types of cancer, and ovarian cancer is the second most common gynecological malignancy.Patients with these types of cancer have high frequency of disease relapse and metastatic cancers of either type are hard to treat.The prevalence and mortality associated with these malignancies has led to the alternative treatment strategies with the aim to reduce recurrence and improve survival.Oncolytic viruses and gene therapy have bee actively investigated as a new way for treating cancer.Vaccinia virus (VV), a poxvirus, has many attributes that make it an attractive candidate for oncolytic therapy and tumor-targeted gene therapy.We have genetically engineered three recombinant oncolytic VV for these purposes.First, we previously deleted two viral genes encoding thymidine kinase (tk) and vaccinia growth factor (vgf), and the resulting virus (vvDD) has been shown to be highly tumor selective and displayed potent oncolytic activity in tumor models in mice and is now in clinical trials.