RAG2 and breast cancer: The metastatic tropism of HER-2+ breast cancer in patients is not readily reproduced in nude mice; recently we reported that Rag2−/−;Il2rg−/− mice enabled a multiorgan metastatic spread of MDA-MB-453 and BT-474 cell lines that mirrored the clinical situation, including ovarian, lung and brain metastases in most mice (Fig. S2 and [18]).