Adriamycin Enhances Proteasome-Mediated Generation of the Proapoptotic Processed Form of MAGE-A4 in Hepatoma Cells

作者：Sakurai Toshiharu^*; Kudo Masatoshi; Itoh Katsuhiko; Ryu U; Higashitsuji Hiroaki; Fujita Jun

来源：Oncology, 2011, 81: 30-35.

DOI：10.1159/000334307

• Adriamycin
• MAGE-A4
• Proteasome
• Apoptosis
• Proteolysis

Background: Melanoma antigen (MAGE)-A4 is processed to generate a C-terminal fragment with proapoptotic activity. Here we demonstrate that Adriamycin promotes generation of the processed MAGE-A4 by activating the proteasome. The proteasome is known to prevent accumulation of toxic proteins to maintain cellular homeostasis. Methods and Results: Treatment of hepatoma cells expressing MAGE-A4 with a sublethal dose of Adriamycin increased the MAGE-A4 processing and sensitized the cells to Adriamycin-induced apoptosis. The processing of MAGE-A4 was inhibited by the proteasome inhibitors MG115, MG132, lactacystin and epoxamicin. MAGE-A4 was coimmunoprecipitated with the S6 proteasomal ATPase, and present in the fractions containing the proteasome during glycerol gradient centrifugation. Consistent with the notion that the proteasome cleaves MAGE-A4, the 26S proteasome, ubiquitin, and cell lysates were necessary for efficient in vitro cleavage of MAGE-A4. Conclusions: The present study suggests that a low dose of maintains cellular homeostasis or leads to apoptosis depending, at least under the present conditions, on the expression of MAGE-A4.

• 出版日期2011