Following administration, OVs modulate the tumor microenvironment by attracting bone marrow-derived macrophages and brain resident microglia to the OV-injected tumor site through the release of chemoattractants by OV-infected tumor cells, such as CCL2 and CCN1 (Parker et al., 2005; Thorne et al., 2014; Meisen et al., 2015). Here, CCL2 is linked to neoplasm.