CXCR4 and breast cancer: To further address the mechanism underlying upregulation of CXCR4 by BAG3, nascent RNA was isolated and real-time RT-PCR demonstrated that BAG3 overexpression did not alter nascent CXCR4 mRNA in breast cancer cells (Figure 5a), indicating that BAG3 promoted CXCR4 expression independent of transcription initiation.