RFX1-dependent activation of SHP-1 induces autophagy by a novel obatoclax derivative in hepatocellular carcinoma cells

• Published in: Oncotarget 2014-07, Vol.5 (13), p.4909-4919
• Main Authors: Su, Jung-Chen, Tseng, Ping-Hui, Hsu, Cheng-Yi, Tai, Wei-Tien, Huang, Jui-Wen, Ko, Ching-Huai, Lin, Mai-Wei, Liu, Chun-Yu, Chen, Kuen-Feng, Shiau, Chung-Wai
• Format: Article
• Language: English
• Subjects: Animals; Antineoplastic Agents - pharmacology; Apoptosis - drug effects; Apoptosis Regulatory Proteins - metabolism; Autophagy - drug effects; Beclin-1; Blotting, Western; Carcinoma, Hepatocellular - genetics; Carcinoma, Hepatocellular - metabolism; Carcinoma, Hepatocellular - prevention & control; Cell Line, Tumor; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Hep G2 Cells; Humans; Liver Neoplasms - genetics; Liver Neoplasms - metabolism; Liver Neoplasms - prevention & control; Male; Membrane Proteins - metabolism; Mice, Nude; Microscopy, Electron, Transmission; Microtubule-Associated Proteins - metabolism; Myeloid Cell Leukemia Sequence 1 Protein - metabolism; Phagosomes - drug effects; Phagosomes - metabolism; Phagosomes - ultrastructure; Phosphorylation - drug effects; Protein Tyrosine Phosphatase, Non-Receptor Type 6 - genetics; Protein Tyrosine Phosphatase, Non-Receptor Type 6 - metabolism; Pyrroles - pharmacology; Regulatory Factor X Transcription Factors; Regulatory Factor X1; Research Paper; RNA Interference; STAT3 Transcription Factor - metabolism; Transcription Factors - genetics; Transcription Factors - metabolism; Tumor Burden - drug effects; Xenograft Model Antitumor Assays
• ISSN: 1949-2553; 1949-2553
• DOI: 10.18632/oncotarget.2054

Obatoclax is a small molecule which targets the Bcl-2 family, and is to treat leukemia, lymphoma and lung carcinoma. Previously, an obatoclax analogue, SC-2001, was found to disrupt the protein-protein interactions of the Bcl-2 family and also repress Bcl-XL and Mcl-1 expression via STAT3 inactivation. Here, we report a novel mechanism of autophagy induction by SC-2001 in liver cancer cells. The findings indicate that SC-2001 induced the autophagy marker LC3-II in four hepatocellular carcinoma (HCC) cells. Autophagosomes induced by SC-2001-treated cells were confirmed by electron microscopy. SC-2001 activated SHP-1, dephosphorylated STAT3 and Mcl-1, and subsequently released free beclin 1. Overexpression of STAT3 and Mcl-1 in PLC5 cells attenuated the induction of SC-2001 on autophagy. Abolishment of SHP-1 by a specific inhibitor aboragated the autophagic effects induced by SC-2001. In addition, it was further revealed that RFX-1, a transcription factor of SHP-1, is a critical regulator in SC-2001-mediated autophagy. Downregulation of RFX-1 by si-RNA protected cells from SC-2001-induced autophagy. Importantly, Huh7 tumor-bearing nude mice treated with SC-2001 showed downregulation of Mcl-1 and p-STAT3 protein expression and upregulation of SHP-1, LC3II, and RFX-1 protein expression. In summary, our data suggest that SC-2001 induces autophagic cell death in a RFX1/SHP-1/STAT3/Mcl-1 signaling cascade.