RARRES2 (retinoic acid receptor responder 2) has different expression patterns in different tumors; for example, in acute myeloid leukemia (AML) and breast cancer, RARRES2 expression is downregulated [38]; however, RARRES2 is overexpressed in oral squamous cell carcinoma, and the overexpression of RARRES2 is associated with angiogenesis and poor prognosis of tumors [39]. This evidence concerns the gene RARRES2 and breast cancer.