Taken together, through the functional validation in estrogen receptor positive breast cancer cells, we found that the expression of seven genes, RPP25, EXOC2, NUP37, RPL13, RPS6, GBP1, and JAK2, were involved in tamoxifen-induced response in both cell lines, and three genes, EMP1, EXTL3, and WBP2NL were involved in tamoxifen-induced response in MCF7. This evidence concerns the gene EXOC2 and breast cancer.