THBS4 and breast cancer: However, interestingly, all three peptides, SAA1, SAA2, and THBS4, also enhanced the migration of two out of three HER2/neu+ cells as examined by the Boyden chamber experiments (Fig. 4d), indicating that the presence of mutant p53 in stromal fibroblasts might have endowed higher metastatic potential to the HER2+ mammary tumor.