FAP and neoplasm: Interestingly, the elimination of CAFs using a FAP-targeting DNA vaccine in the 4T1 murine model of metastatic breast cancer switched the immune microenvironment of the tumor from a Th2 (anti-inflammatory) to a Th1 (pro-inflammatory) phenotype, indicating a key role for CAFs in polarizing the immune response to a pro-tumor type (Liao et al., 2009).