Correction to: Novel smac mimetic APG-1387 elicits ovarian cancer cell killing through TNF-alpha, Ripoptosome and autophagy mediated cell death pathway.

In the publication of this article [1], there was an error in Figs. 2, 3 and 6.

Novel smac mimetic APG-1387 elicits ovarian cancer cell killing through TNF-alpha, Ripoptosome and autophagy mediated cell death pathway.

BACKGROUND: Ovarian cancer is a deadly disease. Inhibitors of apoptosis proteins (IAPs) are key regulators of apoptosis and are frequently dysregulated in ovarian cancer. Overexpression of IAPs proteins has been correlated with tumorigenesis, treatment resistance and poor prognosis. Reinstalling functional cell death machinery by pharmacological inhibition of IAPs proteins may represent an attractive therapeutic strategy for treatment of ovarian cancer. METHODS: CCK-8 and colony formation assay was performed to examine cytotoxic activity. Apoptosis was analyzed by fluorescence microscopy, flow cytometry and TUNEL assay. Elisa assay was used to determine TNFα protein. Caspase activity assay was used for caspase activation evaluation. Immunoprecipitation and siRNA interference were carried out for functional analysis. Western blotting analysis were carried out to test protein expression. Ovarian cancer cell xenograft nude mice model was used for in vivo efficacy evaluation. RESULTS: APG-1387 demonstrated potent inhibitory effect on ovarian cancer cell growth and clonogenic cell survival. APG-1387 induced RIP1- and TNFα-dependent apoptotic cell death in ovarian cancer through downregulation of IAPs proteins and induction of caspase-8/FADD/RIP1 complex, which drives caspase-8 activation. NF-κB signaling pathway was activated upon APG-1387 treatment and RIP1 contributed to NF-κB activation. APG-1387 induced cytoprotective autophagy while triggering apoptosis in ovarian cancer cells and inhibition of autophagy enhanced APG-1387-induced apoptotic cell death. APG-1387 exhibited potent antitumor activity against established human ovarian cancer xenografts. CONCLUSIONS: Our results demonstrate that APG-1387 targets IAPs proteins to potently elicit apoptotic cell death in vitro and in vivo, and provide mechanistic and applicable rationale for future clinical evaluation of APG-1387 in ovarian cancer.

Smac mimetics in combination with TRAIL selectively target cancer stem cells in nasopharyngeal carcinoma.

Nasopharyngeal carcinoma is a common malignancy in Southern China. After radiotherapy and chemotherapy, a considerable proportion of patients with nasopharyngeal carcinoma suffered tumor relapse and metastasis. Cancer stem cells (CSC) have been shown with resistance against therapies and thus considered as the initiator of recurrence and metastasis in tumors, where the antiapoptotic property of CSCs play an important role. Smac/DIABLO is an inverse regulator for the inhibitors of apoptosis protein family (IAP), which have been involved in apoptosis. Here, the effects of Smac mimetics on the CSCs of nasopharyngeal carcinoma were studied both in vitro and in vivo, using two clones of nasopharyngeal carcinoma cell line CNE2 as models. We found that one of the clones, S18, had CSC-like properties and IAPs were overexpressed. The combination of Smac mimetics and TNF-related apoptosis-inducing ligand (TRAIL) can reduce the percentage of SP cells and inhibit the colony- and sphere-forming abilities of S18 cells, indicating their ability to attenuate the CSCs. Moreover, in a nasopharyngeal carcinoma xenograft model, the administration of Smac mimetics in combination with TRAIL also led to the elimination of nasopharyngeal carcinoma stem cells. Furthermore, the Smac mimetics in combination with TRAIL induced the degradation of cIAP1 and XIAP and thus induced apoptosis in vitro and in vivo. Taken together, our data show that Smac mimetics exerted an antitumor effect on nasopharyngeal carcinoma cancer stem cells, and this combination treatment should be considered as a promising strategy for the treatment of nasopharyngeal carcinoma.

Synergistic antitumoral activity and induction of apoptosis by novel pan Bcl-2 proteins inhibitor apogossypolone with adriamycin in human hepatocellular carcinoma.

AIM: To investigate the in vitro and in vivo activities and related mechanism of apogossypolone (ApoG2) alone or in combination with adriamycin (ADM) against human hepatocellular carcinoma (HCC). METHODS: The IC50 of ApoG2 in vitro was tested by WST assay, and the synergistic effect was analyzed using the CalcuSyn method. Cell apoptosis was determined using 4',6-diamidino-2- phenylindole staining and flow cytometric analysis. Western blotting was used to determine the expression of apoptosis-related proteins. In vivo activity was evaluated in the xenograft model in nude mice, and apoptosis in tumor tissues was determined by terminal deoxynucleotidyl transferase-mediated digoxigenin-dUTP nick-end labeling (TUNEL) assay. RESULTS: The IC50 of ApoG2 in HCC cells was 17.28-30.63 micromol/L. When ApoG2 was combined with ADM, increased cytotoxicity and apoptosis were observed in SMMC-7721 cells compared to treatment with ApoG2 alone. The Western blotting results indicated that the ApoG2 induced apoptosis in SMMC-7721 cells by downregulating anti-apoptotic proteins Bcl-2, Mcl-1, and Bcl-XL, up-regulating pro-apoptotic protein Noxa, and promoting the activities of caspases-9 and -3. The tumor growth of xenograft SMMC-7721 was inhibited in nude mice when ApoG2 was administered orally without causing damage to the normal tissues. The in vivo study also indicated an increasing anti-tumoral effect when ApoG2 at 100 or 200 mg/kg dosages were used together with ADM at 5.5 mg/kg, with relative tumor proliferation rate (T/C) values of 0.456 and 0.323, respectively. Apoptosis induced in vivo by ApoG2 alone or combined with ADM was confirmed by TUNEL assay in tumor tissues. CONCLUSION: ApoG2 is a potential non-toxic target agent that induces apoptosis by upregulating Noxa, while inhibiting anti-apoptotic proteins and promoting the effect of chemotherapy agent ADM in HCC.