Through the use of several cell lines, it has been shown that NGF -mediated proliferation of breast cancer cells could be reduced or inhibited by the TrkA phosphorylation inhibitor K252a [85,88], the selective inhibitor of the MAPK cascade PD98059 [88], the antiestrogen drug tamoxifen [85], the TrkA inhibitor larotrectinib [70] and endocannabinoids [96]. This evidence concerns the gene NTRK1 and breast cancer.