Apoptin sensitizes radiation-induced cell death via classic mitochondrial, caspase and p53-dependent signaling in HepG2 cells

Abstract

Abstract. resistance or insensitivity to radiation therapy is one of the hallmarks of hepatocellular carcinoma. Sensitizing radioresistant cancer by combining radiation with other therapeutics to induce apoptosis has been widely investigated. our previous study showed that chicken anaemia virus-derived apoptin protein induced the apoptosis of hepatic carcinoma HepG2 cells. in the present study, we demonstrated that apoptin sensitizes cells to radiation-induced apoptosis using a lentivirus-apoptin expression system in hepatic carcinoma HepG2 cells. combination therapy with radiation and apoptin dramatically induced mitochondrial cytochrome c release and the cleavage of caspases -9, -3 and -7. Our findings are also the first to show that the combination of radiation and apoptin up-regulates p53 expression. Thus, apoptin treatment represents a potential method for enhancing the effectiveness of radiotherapy in poorly responding hepatocellular carcinoma. IntroductionHepatocellular carcinoma is the sixth most common cancer worldwide and the third most common cause of cancer-related death, particularly in developing countries. Hepatocellular carcinoma patients have fairly poor outcomes, with only a 3-5% survival rate at the 5-year benchmark (1). Major treatment options for patients include liver resection and subsequent liver transplantation; however, these are not possible in many patients (2). reasons include poor liver function, macrovascular tumor invasion and extended wait times for donor organs (3). radiation therapy (rT) has historically played a minor role in the management of unresectable tumors, since these cancer cells are not sensitive to radiation. They also present a clinical challenge, since rT dose-escalation is not well-tolerated by the liver (4). researchers are therefore examining combination treatments using novel strategies that may allow for a decreased dosage and enhanced sensitivity to radiation. apoptin has increasingly been shown to be of value in specifically targeting and eliminating cancer cells (5). This protein was first isolated from the chicken anemia virus, and its potential anti-cancer effects appear to be tumor specific; transformed cells are specifically targeted, while primary and non-transformed cells are spared (6). The apoptotic activity of apoptin is suggested to occur via a p53-independent, Bcl-2-enhanced mechanism (7,8).our previous study showed that secretory transactivating transcription apoptin fusion protein induces cell apoptosis in hepatocellular carcinoma HepG2 cells (9,10). in the present study, we sought to explore the anti-tumor effect of a combination of rT and apoptin gene therapy in radio-resistant hepatocellular carcinoma HepG2 cells, and to further investigate the mechanisms of apoptosis. The results indicated that combination treatment with RT and apoptin has a beneficial effect on the apoptosis of radio-resistant hepatocellular carcinoma HepG2 cells through mitochondrial proteins, caspase activation and p53-dependent signaling. Materials and methods Cells an...

Mechanism of Inactivation of Ornithine Aminotransferase by (1S,3S)-3-Amino-4-(hexafluoropropan-2-ylidenyl)cyclopentane-1-carboxylic Acid

“…It is apparent from the crystal structure (Figure 2) that the carbon atom bound to the α-trifluoromethyl group is sp 3hybridized instead of sp 2 -hybridized as shown in 13 (Scheme 2). This alters the mechanism from that predicted in Scheme 2 because an sp 3 -hybridized carbon atom adjacent to the trifluoromethyl group would require that upon inactivation the cofactor would be in the PLP form. High-resolution mass spectrometry was used to identify the cofactor form as PLP (Figure 4), consistent with the crystal structure.…”

“…The hydrolysis of 40 gives 43 (via possible intermediates 41 and 42), one of the observed species by intact protein mass spectrometry, and the hydrolysis of 43 gives 44, the other species observed by intact protein mass spectrometry. To obtain the sp 3 -hybridized center at the carbon adjacent to the α-trifluoromethyl group, enolate 42 must be protonated stereoselectively. Given that the iminium proton has broken its phenoxide hydrogen bond and is 2.7 Å from the enol alkene (Figure 8) and because of the geometric constraints of the newly formed covalent bond to Lys292 and the lack of rotatable bonds, we propose an intramolecular stereoselective proton transfer (42) to produce 43, as depicted in Scheme 6.…”

“…Liver cancer is the second leading cause of cancer death worldwide; hepatocellular carcinoma (HCC) accounts for 90% of liver cancer in the United States . Current treatments for liver cancer consist of surgery, radiation, and chemotherapy; however, HCC is highly resistant to both radiation and chemotherapy . , The development of HCC has been shown to correlate with the activation of the Wnt/β-catenin signaling pathway in the liver .…”

TAT-Apoptin induces apoptosis in the human bladder cancer EJ cell line and regulates Bax, Bcl-2, caspase-3 and survivin expression

“…This makes it a candidate for the development of novel therapeutic strategies. Studies have revealed that Apoptin is able to kill numerous types of tumor cells, including hepatoma carcinoma cells (1)(2)(3), oral cancer cells (4) and ovarian cancer cells (5). However, the effect of this protein on bladder cancer cells remains unknown.…”

Apoptin Induces Apoptosis in Human Bladder Cancer EJ and BIU-87 Cells

“…This merit has attracted more and more attention from the researchers. Different studies have shown that Apoptin could kill almost all kinds of tumor cells, such as hepatoma carcinoma cells (Han et al, 2008;Han et al, 2010;Han et al, 2011) , oral cancer cells (Schoop, et al, 2008), ovarian cancer cells (Wang et al, 2011). However, the effect of this protein on bladder cancer cells still keep unknown.…”