CREB1 and breast cancer: Indeed, phosphorylated CREB (p-CREB) was notably reduced in LIMK1-knockdown Hs578T and PL-BC-05 cells and increased in ectopic LIMK1 MCF-7 cells (Figs. 5A and S5F, G), while total CREB levels were similar (Fig. S5F), suggesting that LIMK1 regulates MMP2 gene expression by phosphorylating CREB.