TABLE 1.

Summary of mechanisms leading to tamoxifen resistance

Factors	Mechanism(pathway)	Expression in breast cancer	Ref
EREG	miR-186-3p/EREG/EGFR regulatory cascade	High	(He et al., 2019)
NgBR	Promote EGF signaling	High	(Gao et al., 2018)
ERα36	Promote EGFR/ERK signaling	High	(Li et al., 2020b)
	Activate HER2 expression and its cascade	High	(Mansouri et al., 2018b)
	Activate Sphkl/S1P axis	High	(Maczis et al., 2018)
IGF1R	Inhibit FoxOl expression	Low	(Vaziri-Gohar et al., 2017)
PAK2	PAK2 acts downstream of IGF1R signaling	High	(Zhang et al., 2018)
Brachyury	Downregulate SIRT1 expression	High	(Li et al., 2016)
RBP2	Activate ER-IGF1R-ErbB signaling cascade	High	(Choi et al., 2018)
Cyclin D1	Promote the progress of G1-S phase	High	(Viedma-Rodriguez et al., 2014)
LEM4	Promote the transcription of cyclin D1	High	(Gao et al., 2018)
SPY1	SPY1 binds to CDK, mediates the phosphorylation of ERK	High	(Ferraiuolo et al., 2017)
SOX9	c-MYC/HDAC5/SOX9 axis	High	(Xue et al., 2019)
SALL2	Activate AKT/mTOR signaling	Low	(Ye et al., 2019)
HIF-1α	Downregulate the expression of ERα	High	(Jogi et al., 2019)