Abstract.The small molecule multi-kinase inhibitor sorafenib has become the standard systemic treatment for patients with advanced hepatocellular carcinoma (HCC) and renal cell carcinoma. Similar to other kinase inhibitors, drug resistance hinders its clinical use; thus, combination therapy to improve sorafenib sensitivity is a promising approach. The present study shows for the first time that the combination of sorafenib and wogonin exerts a significant potentiation of cytotoxicity in a number of human HCC cell lines in a dose-dependent manner. Enhanced cell death was due to potentiation of apoptosis, which was demonstrated by increased apoptotic cell populations, caspase activation and suppression of cell death by the pan-caspase inhibitor carbobenzoxy-valyl-alanyl-aspartyl. Sorafenib induced autophagy activation, which was shown by autophagic flux. Suppression of autophagy with the autophagy inhibitors chloroquine or 3-methyladenine significantly enhanced cytotoxicity, suggesting that sorafenib-induced autophagy is cytoprotective. Notably, wogonin effectively inhibited sorafenib-induced autophagy. Altogether, our results indicate that the combination of wogonin and sorafenib effectively kills human HCC cells. This occurs, at least in part, through autophagy inhibition, which potentiates apoptosis. Thus, wogonin could be an ideal candidate for increasing sorafenib's activity in HCC therapy, which warrants further investigation in vivo.

Sorafenib is a small-molecule multi-kinase inhibitor approved by FDA as an oral agent for the treatment of hepatocellular carcinoma (HCC) and renal cell carcinoma. However, unresponsiveness and acquired resistance are commonly observed, which hinder the clinical use of sorafenib. As combination therapy is a promising approach to improve its efficacy, we investigated if sorafenib and luteolin combination is effective in killing human HCC cells. Cell death was examined by lactate dehydrogenase (LDH) releasing assay. Apoptosis was detected by flow cytometric. The activation of apoptotic pathway and c-Jun N-terminal kinase (JNK) signaling pathway was measured by western blot. The results showed that sorafenib and luteolin combination synergistically induced cytotoxicity in HCC cells, which was accompanied by potentiation of apoptosis as demonstrated by increased apoptotic cell populations, caspase activation, and suppression of cell death by the pan-caspase inhibitor z-VAD-fmk. Furthermore, the combination of both agents enhanced expression of phosphorylated form of JNK, and the JNK inhibitor SP600125 effectively attenuated cell death induced by the combination treatment. Thus, sorafenib and luteolin combination synergistically kills HCC cells through JNK-mediated apoptosis, and luteolin may be an ideal candidate for increasing the activity of sorafenib in HCC therapy.

Abstract. Human desumoylating isopeptidase 2 (DESI-2) is a member of the DESI family and contains a conserved PPPDE1 domain. Previous studies have demonstrated that DESI-2 overexpression may induce cell apoptosis. In the present study, differentially expressed genes were analyzed using a transcription microarray in DESI-2 overexpressing PANC-1 pancreatic cancer cells. A total of 45,033 genes were examined by microarray, which identified 1,766 upregulated and 1,643 downregulated genes. A series of altered signaling pathways were analyzed, in which certain essential signaling factors, including retinoid X receptor (RXR), BH3 interacting-domain death agonist, Ras homolog gene family member A (RhoA) and Rho-associated protein kinase, were further investigated at the protein level. The release of cytochrome c and the activation of caspase-3 were also detected by western blot analysis. Immunohistochemistry further revealed the expression features of RXR and RhoA in pancreatic ductal adenocarcinoma tissues with various DESI-2 expression levels. The results serve as a valuable reference for the further elucidation of the functions of DESI-2 in pancreatic cancer.