In this study utilizing the GART inhibitor LMX (39) in various BC cell lines of different subtypes has revealed that LMX could act as an ‘anti-estrogen-like’ compound by inducing receptor degradation, and that the de novo purine biosynthetic pathway could be a promising target for treating LumA ERα-expressing primary and metastatic IDC. This evidence concerns the gene TMEM43 and breast cancer.