Project 467165

Oncolytic viruses can be used to target and destroy cancer without harming healthy cells. Clinical trials using an oncolytic reovirus have shown positive results, though the optimization of treatment is required. For example, metalloproteases (MPs), present in the breast cancer tumor microenvironment (TME), have been observed to cleave the ?1 attachment protein of reovirus, thereby reducing tumor clearance. The Shmulevitz lab has previously published that a mutation in the ?1 protein (T249I) can resist MP-mediated cleavage. Aim 1 is to establish the oncolytic activity of MP-resistant reoviruses by comparison to wild-type reovirus in breast cancer models. If the T249I mutation in the ?1 protein protects against MP-mediated cleavage, then an increase in breast cancer clearance should be observed. In Aim 2, the TME of triple-negative breast cancer (TNBC) models will be characterized to determine the repertoire of MP expression. The findings will provide the foundations for the optimization of reovirus clinical treatments. To further provide the means to increase the efficacy of reovirus clinical treatments of breast cancer, reovirus variants will be created with modified ?1 proteins. Aim 3 consists of testing these variants to ensure resistance to MP-mediated cleavage but also show maintained levels of breast cancer infectivity. Additionally, the ?1 protein is immunogenic; therefore, neutralization of reovirus by antibodies will be measured and circumvented by using subsequent doses of ?1 variant reoviruses. Collectively, the findings will provide an understanding of the TME of breast cancers and the barriers to oncolytic virus treatments such as ?1 cleavage while also providing the means to overcome such obstacles.