Sorafenib is the standard first-line therapeutic treatment for patients with advanced hepatocellular carcinoma (HCC), but its use is hampered by the development of drug resistance. The activation of Akt by sorafenib is thought to be responsible for this resistance. Bufalin is the major active ingredient of the traditional Chinese medicine Chan su, which inhibits Akt activation; therefore, Chan su is currently used in the clinic to treat cancer. The present study aimed to investigate the ability of bufalin to reverse both inherent and acquired resistance to sorafenib. Bufalin synergized with sorafenib to inhibit tumor cell proliferation and induce apoptosis. This effect was at least partially due to the ability of bufalin to inhibit Akt activation by sorafenib. Moreover, the ability of bufalin to inactivate Akt depended on endoplasmic reticulum (ER) stress mediated by inositol-requiring enzyme 1 (IRE1). Silencing IRE1 with siRNA blocked the bufalin-induced Akt inactivation, but silencing eukaryotic initiation factor 2 (eIF2) or C/EBP-homologous protein (CHOP) did not have the same effect. Additionally, silencing Akt did not influence IRE1, CHOP or phosphorylated eIF2α expression. Two sorafenib-resistant HCC cell lines, which were established from human HCC HepG2 and Huh7 cells, were refractory to sorafenib-induced growth inhibition but were sensitive to bufalin. Thus, Bufalin reversed acquired resistance to sorafenib by downregulating phosphorylated Akt in an ER-stress-dependent manner via the IRE1 pathway. These findings warrant further studies to examine the utility of bufalin alone or in combination with sorafenib as a first- or second-line treatment after sorafenib failure for advanced HCC.
Sorafenib is the standard first-line systemic drug for advanced hepatocellular carcinoma (HCC), but it also induces the activation of Akt, which contributes to the mechanisms for the resistance to sorafenib. Arsenic trioxide (ATO) is a currently clinically used anticancer drug and displays its anticancer activities by inhibiting Akt activation. Therefore, we hypothesized that ATO may potentiate the anti-cancer activities of sorafenib against HCC. The results have demonstrated that ATO synergized with sorafenib to inhibit the proliferation and promote the apoptosis of HCC cells by diminishing the increased activation of Akt by sorafenib. ATO was shown to inhibit the expression or activation of Akt downstream factors, including glycogen synthase kinase (GSK)-3β, mammalian target of rapamycin (mTOR), ribosomal protein S6 kinase (S6K), and eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), which regulate cell apoptosis and were upregulated or activated by sorafenib. Both sorafenib and ATO downregulated the expression of cyclin D1, resulting in HCC cells arrested at G0/G1 phase. ATO downregulated the expression of Bcl-2 and Bcl-xL and upregulated the expression of Bax, indicating that ATO could induce the apoptosis of HCC cells through the intrinsic pathways; but sorafenib showed little effects on these proteins of Bcl-2 family. ATO synergized with sorafenib to suppress the growth of HCC tumors established in mice by inhibiting the proliferation and inducing the apoptosis of HCC cells in situ. These results indicate that ATO may be a potential agent that given in combination with sorafenib acts synergistically for treating HCC.
Fragile X-related gene 1 (FXR1) is deregulated in a variety of human disorders including cancer. However, there is relatively little evidence concerning the relationship between FXR1 and colorectal cancer. Western blot, immunohistochemistry (IHC), and quantitative real-time PCR (qRT-PCR) were adopted to detect the FXR1 protein and messenger RNA (mRNA) expression, respectively. Enzyme-linked immunosorbent assay (ELISA) was used to evaluate the plasma FXR1 expression in our study. MTT assay and colony formation assay were used to examine the proliferation ability of cells in vitro. In addition, Transwell assays were performed to test the migration and invasion abilities of cancer cells. We found that the average plasma FXR1 level in CRC was significantly higher than that in healthy controls (P < 0.001). Moreover, the plasma expression of FXR1 in stage IV patients was dramatically higher than that in stage I, stage II, and stage III patients (P < 0.001). Consistently, FXR1 mRNA expression levels were much higher in cancer tissues than that in normal tissues. Moreover, IHC results showed that cancer tissues possessed higher FXR1 expression (P = 0.027). What's more, plasma FXR1 was a risk factor of colorectal cancer indicated by univariate survival analysis (P = 0.021, HR = 1.685, 95 % CI 1.336-1.927). Multivariate analysis suggested that FXR1 was an independent risk factor of colorectal cancer (P = 0.008, HR = 1.381, 95 % CI 1.119-1.741). Kaplan-Meier analysis showed that the patients with higher plasma FXR1 expression had a poorer outcome (P < 0.001). Besides, FXR1 acted as an oncogene which could increase the proliferation, migration, and invasion of cancer cells. All these data indicate that FXR1 might act as a tumor promoter. Future investigations are warranted to explore whether FXR1 may represent a novel therapeutic target.
Exposure to dioxins, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), is reported to affect the autoimmune system and increase the risk of autoimmune disease. Generally, dioxin exerts its toxicity via aryl hydrocarbon receptor (AhR). Primary biliary cholangitis (PBC) is a chronic autoimmune disease, and its pathogenesis involves the interplay between immune and environmental factors. This study showed the effect of dendritic cells (DCs) activated by TCDD on naïve CD4+ T cell differentiation in patients with PBC. CD14+ mononuclear cells were isolated from peripheral blood mononuclear cells (PBMCs) of patients with PBC and healthy people by magnetic cell separation and introduced into DCs. Two days after stimulation by TCDD, DCs were cocultured with naïve CD4+ T cells in a ratio of 1 : 2 for 3 days. Then, differentiation-related factors for naïve CD4+ T cells were detected by real-time fluorescence quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and flow cytometry. The results showed that TCDD-activated DCs could promote Th1 and Th17 differentiation in patients with PBC. Therefore, this study demonstrated TCDD as an AhR agonist in regulating naïve CD4+ T cell differentiation in patients with PBC.
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