Because the TM4SF1 expression was downregulated in HR+HER2- breast cancer and the TM4SF1-overexpression inhibited MCF-7 and ZR-75-1 cell viability and proliferation in vitro, the roles of TM4SF1 in the HR+HER2- breast tumor growth were examined in a murine model. This evidence concerns the gene ERBB2 and breast carcinoma.