Figure 4From: Tamoxifen induces apoptosis through cancerous inhibitor of protein phosphatase 2A–dependent phospho-Akt inactivation in estrogen receptor–negative human breast cancer cellsIn vivo effect of tamoxifen on human breast cancer cell lines in xenograft nude mice. (A) Tamoxifen treatment decreased the size of MDA-MB-468 tumors (left) but did not affect HCC-1937 tumor cell growth (right). Points, mean values (n = 6); bars, SE; *P < 0.05. Mice received either 100 mg/kg body weight tamoxifen citrate administered orally three times weekly or vehicle (1× phosphate-buffered saline), as described in the Methods section. (B) Western blot analysis of the expression levels of cancerous inhibitor of protein phosphatase 2A (CIP2A), phospho-Akt (p-Akt) and Akt in MDA-MB-468 and HCC-1937 xenografts treated with control or tamoxifen. (C) Body weight of xenograft mice bearing MDA-MB-468 (top) and HCC-1937 (bottom) tumors. Points, mean values (n = 6); bars, SD. (D) Schema of the molecular mechanism of the action of tamoxifen on the CIP2A/PP2A pathway. By inhibiting CIP2A, tamoxifen restores protein phosphatase 2A (PP2A) activity downregulating p-Akt and leading to subsequent cell apoptosis.Back to article page