Curcumin Inhibits AP-2γ To Induce Apoptosis In Testicular Germ Cell Tumor Cell Line NTera-2

Though the apoptotic effect of curcumin focus on many cancers such as breast carcinoma and hepocellular carcinoma,which is considered to be an important mechanism of anti-tumor, few studies have been designed to explore the effect of curcumin on human testicular germ cell tumors(TGCT).In the present study, we investigate the apoptosis effects of curcumin on testicular germ tumor cell line NTera-2 by Hoechst 33258 staining, TUNEL assay and Annexin V-FITC/PI method. MTT assay was used to detect proliferation. The results show that the induction of apoptosis and inhibition of proliferation were observed in NTera-2 cells incubated with curcumin in a time- and dose-dependent manner. By western blot analysis, we found the anti-apoptotic gene Bcl-2 was down-regulated after curcumin treatment, whereas the protein level of Bax was up-regulated, which induced the permeability change of mitochondrial outer membrane. Furthermore, induced apoptosis was accompanied by the release of CytC and the activation of caspase-9, caspase-3, caspase-8 and Poly(ADP-Ribose) polymerase(PARP).There is no expression of transcription factor AP-2γ in the normal testicular tissues, but high expression in germ cell tumors. So is considered to be a marker protein on the patients of TGCT. The expression of transcription factor AP-2γ shown a downward trend with the increasing dose of curcumin. While we found that the degradation of AP-2γ protein was due to the proteasome pathway. At the same time, we found the expression of ErbB2 is down-regulated when the expression of AP-2γ down-regulared. This result consistented with the study of AP-2γ positive regulate ErbB2. In order to further investigate the potential mechanisms of the apoptosis by curcumin, we studied the influence AP-2γ to the cell survival signaling pathways of MAPK and PI3K-PKB/AKT. We found that curcumin inhibited the activation of p-ERK and p-AKT.These data reveal that curcumin can inhibit the proliferation and induce apoptosis of NTera-2 cell maybe via influencing AP-2γ downstream signaling pathways. These indicate a novel anti-tumor mechanism of curcumin and a new candidate therapeutic agent for human testicular germ cell tumors.