PBX1-interacting proteins increase cancer cell proliferation/M cell cycle transition through the activation of G1/S and G2, which is accompanied by an increase in the levels of positive cell cycle regulators, such as cyclin D1, cyclin A, and cyclin B. PBX1 interacts with estrogen receptor (ER) and its overexpression partially alleviates the inhibitory effect of ER antagonists on tumor cells and aggravates the tumor-promoting effect of estrogen on cancer cells (Magnani et al., 2013; Feng et al., 2015; He et al., 2017; Zhao et al., 2022). The gene discussed is ESR1; the disease is cancer.