PDGFRA and cytomegalovirus infection: Infection with human cytomegalovirus (CMV) is common in adults in developed countries (~40–70%), and this virus was shown to preferentially infect breast cancer cells with elevated expression of platelet-derived growth factor receptor-α (PDGFRα) and fibroblasts (which have high levels of PDGFRα expression); infection of PDGFRα+ fibroblasts raised the possibility that human CMV infection could affect the tumor microenvironment, leading to a more inflammatory milieu [110].