Data have shown that tamoxifen (TAM) can be used to treat not only breast cancer with positive estrogen receptor (ER), but also negative ER including human glioma. However, the molecular mechanism of this drug against different kinds of cancers remains to be elucidated. In this study, we provided the evidence that PKCalpha-ERK1/2 signaling pathway plays a negative role in TAM-induced C6 cell apoptosis, and a combined utilization of TAM with inhibitors of PKCalpha or ERK1/2 could enhance the effectiveness of TAM on inhibiting tumor growth.