Silence of p15 expression by RNAi enhances cisplatin resistance in hepatocellular carcinoma cells

Measuring the differential expression of the major hypermethylated tumor suppressor genes in tissues of primary hepatocellular carcinoma

BACKGROUND

Hepatocarcinogenesis is a multifactorial process that arises from a integration of genetic and epigenetic anomalies leading to abnormal gene expression and function. It is difficult to characterize HCC with a single biomarker. Our study aimed at detecting the expression of a panel of 8 methylated genes (SOCS1, APC, Gadd45b, CDKN1B, P15, PAX6, STAT1 and MSH2) as regulatory factors among Egyptian patients with HCC.

METHODS

This study was conducted on HCC tissue samples of 30 Egyptian patients in comparison with their non-cancerous adjacent cirrhotic tissue as a control. Tissue samples were obtained from patients who have undergone living donor liver transplantation (LDLT) or liver resection at El Sahel Teaching Hospital (Cairo, Egypt). A special Custom designed PCR Arrays was used to analyze the expression profiles of chosen methylated genes associated with HCC.

RESULTS

Expression of SOCS1, APC, Gadd45b, CDKN1B, P15, PAX6, STAT1 and MSH2 were lower in the HCC tissue compared to the cirrhotic tissue (pvalue = 0.015, 0.081, 0.004, 0.027, 0.211, 0.015, 0.025 and 0.0001 respectively). 5 genes (SOCS1, APC, GAdd45b, CDKN1B, and MSH2) showed the ability to be used as diagnostic biomarkers for HCC with high sensitivity and specificity values at cut off values: 1.05, 1.17, 0.995, 0.546, and 0.125 respectively. As for the other 3 genes (P15, PAX6, STAT1), PAX6 gene has the highest sensitivity at a cut off value of 0.3364. A significant negative correlation was shown between alpha fetoprotein (AFP) and 5 of the studied genes (SOCS1, APC, Gadd45b, STAT1, and MSH2).

CONCLUSIONS

Expression of the selected hypermethylated genes (SOCS1, APC, Gadd45b, CDKN1B, P15, PAX6, STAT1 and MSH2) in HCC tissue samples was lower than adjacent tissue. Their role should be further studied to solve the mystery that surrounds the pathogenesis of HCC.

High Expression of G9a Induces Cisplatin Resistance in Hepatocellular Carcinoma

OBJECTIVE

Chemotherapeutic drug resistance is the main obstacle that affects the efficacy of current therapies of hepatocellular carcinoma (HCC), which needs to be addressed urgently. High expression of histone methyltransferase G9a was reported to play a pivotal role in the progression of HCC. Regulatory mechanism of aberrant activation of G9a in HCC and the association with subsequent cisplatin (DDP) resistance still remains ambiguous. This study strived to investigate mechanism of G9a overexpression and its impact on cisplatin resistance in HCC cells.

MATERIALS AND METHODS

In this experimental study, we investigated effects of different concentrations of cisplatin in combination with BIX-01294 or PR-619 on viability and apoptosis of HuH7 and SNU387 cells via CCK-8 kit and flow cytometric analysis, respectively. Colony formation capacity was applied to evaluate effect of cisplatin with or without BIX-01294 on cell proliferation, and western blotting was used to verify expression level of the related proteins. Global mRNA expression profile analysis was adopted to identify differentially expressed genes associated with overexpression of G9a.

RESULTS

We observed that overexpression of G9a admittedly promoted cisplatin resistance in HCC cells. Global mRNA expression profile analysis after G9a inhibition showed that DNA repair and cell cycle progression were downregulated. Moreover, we identified that deubiquitination enzymes (DUBs) stabilized high expression of G9a in HCC through deubiquitination. Additionally, cisplatin could significantly inhibit proliferation of DUBs-deficient HCC cells, while promoting their apoptosis.

CONCLUSION

Collectively, our data indicated that DUBs stabilize G9a through deubiquitination, thereby participating in the cisplatin resistance of HCC cells. The elucidation of this mechanism contributes to propose a potential alternative intervention strategy for the treatment of HCC patients harboring high G9a levels.

TIPE2 sensitizes osteosarcoma cells to cis-platin by down-regulating MDR1 via the TAK1- NF-κB and - AP-1 pathways

TIPE2 participates in multiple types of cancer development. However, its mechanism underlying chemoresistance in osteosarcoma has not been elucidated. Herein, we observed the expression of TIPE2 and MDR1 in cis-platin-resistant osteosarcoma tissues and cell lines. Compared to their matched sensitive cell lines and tissues, TIPE2 was downregulated while MDR1 expression was increased. Further investigation showed that overexpression of TIPE2 effectively inhibited MDR1 expression and greatly sensitized osteosarcoma cells to cis-platin, both in vivo and in vitro. Mechanistically, TIPE2 inhibited the transcription of the MDR1 promoter by interfering with the TAK1-NF-κB and -AP-1 pathways. Overall, our results elucidated for the first time that TIPE2 sensitizes osteosarcoma cells to cis-platin through downregulation of MDR1 and may be a novel target in osteosarcoma therapy.

ZHX2 enhances the cytotoxicity of chemotherapeutic drugs in liver tumor cells by repressing MDR1 via interfering with NF-YA

We previously reported the tumor suppressor function of Zinc-fingers and homeoboxes 2 (ZHX2) in hepatocellular carcinoma (HCC). Other studies indicate the association of increased ZHX2 expression with improved response to high dose chemotherapy in multiple myeloma. Here, we aim to test whether increased ZHX2 levels in HCC cells repress multidrug resistance 1(MDR1) expression resulting in increased sensitivity to chemotherapeutic drugs. We showed evidence that increased ZHX2 levels correlated with reduced MDR1 expression and enhanced the cytotoxicity of CDDP and ADM in different HCC cell lines. Consistently, elevated ZHX2 significantly reduced ADM efflux in HepG2 cells and greatly increased the CDDP-mediated suppression of liver tumor growth in vivo. Furthermore, immunohistochemical staining demonstrated the inverse correlation of ZHX2 and MDR1 expression in HCC tissues. Luciferase report assay showed that ZHX2 repressed the MDR1 promoter activity, while knockdown of NF-YA or mutating the NF-Y binding site eliminated this ZHX2-mediated repression of MDR1 transcription. Co-IP and ChIP assay further suggested that ZHX2 interacted with NF-YA and reduced NF-Y binding to the MDR1 promoter. Taken together, we clarify that ZHX2 represses NF-Y-mediated activation of MDR1 transcription and, in doing so, enhances the effects of chemotherapeutics in HCC cells both in vitro and in vivo.

Overexpression of osteopontin promotes resistance to cisplatin treatment in HCC

Osteopontin (OPN) is a multi-functional cytokine involved in cell survival, migration and adhesion. Increasing evidence has elucidated its role in tumorigenesis, progression and metastasis. However, the role of OPN in chemoresistance of human hepatocellular carcinoma (HCC) has not yet been clarified. In the present study, we examined the expression of OPN in human HCC samples before and after cisplatin-treatment, the results showed that OPN was significantly increased in cisplatin-resistant specimens. We then studied the effect of cisplatin on OPN expression in HCC cells, after exposure to cisplatin, the expression of OPN in HCC cells was elevated compared to control cells. We also found that PI3K/AKT signaling pathway was also activated by cisplatin and this effect was induced by the OPN pathway. To study the effect of OPN on chemoresistance, HCC cells were treated with cisplatin along with OPN. Incubation with OPN enchanced the chemoresistance of HCC cells to cisplatin. In contrast, blockage of OPN pathway promoted the chemosensitivity of HCC cells to cisplatin. Our results suggest that OPN enhanced chemoresistance of cisplatin in HCC cells by activating PI3K/AKT signaling pathway, blocking the OPN pathway might be a novel way to overcome the disease.

Effects of urotensin II and its specific receptor antagonist urantide on rat vascular smooth muscle cells

We investigated the effects of urantide, a receptor antagonist of urotensin II (U-II), on the expression of U-II and its receptor GPR14 in rat vascular smooth muscle cells. Vascular smooth muscle cells from rat thoracic aorta were cultured by explant method. Subjects in this experiment were divided into eight groups: normal control group (group C), U-II group (group M), positive control group (Flu group) and urantide-treated groups (10⁻¹⁰, 10⁻⁹, 10⁻⁸, 10⁻⁷ and 10⁻⁶ mol/L). Cultured vascular smooth muscle cells in vitro were studied by immunocytochemistry, biochemistry, and flow cytometry. U-II (10⁻⁸ mol/L) promoted the proliferation of vascular smooth muscle cells at each time point, influenced cell cycle, increased proliferation index and S-phase cell fraction, and dramatically promoted the expression of U-II and GPR14. In the concentration range from 10⁻¹⁰ to 10⁻⁶ mol/L, urantide dramatically inhibited the proliferation of vascular smooth muscle cells and the protein expression of U-II and GPR14, especially at a concentration of 10⁻⁶ mol/L. U-II, binding with its receptor GPR14, promotes vascular smooth muscle cells proliferation and migration, which can be inhibited by urantide. This study provides an evidence for understanding the effects of U-II and its receptor GPR14 on vascular smooth muscle cells.

Promoter hypermethylation of p14 (ARF) , RB, and INK4 gene family in hepatocellular carcinoma with hepatitis B virus infection

Both hepatitis B virus (HBV) and gene methylation play important roles in hepatocarcinogenesis. However, their association between HBV infection and gene methylation is not fully understood. Cell cycle control involving RB1 gene-related cell inhibitors is one of the main regulatory pathways were reported to be altered in hepatocellular carcinoma (HCC). The purpose of this research is to assess the methylation status of p14 (ARF) and INK4 gene family (p14 (ARF) , p15 (INK4B) , p16 (INK4A) , and p18 (INK4C) ) in HCC with HBV infection and HCC without it, and discuss possible role of HBV-induced hypermethylation in the mechanism of hepatocarcinogenesis. Methylation status of RB, p14 (ARF) , and INK4 gene family in 64 case of HCC with HBV infection and 24 cases without it were detected by methylation-specific polymerase chain reaction, and HBV-DNA of the plasma were detected by quantitative real-time polymerase chain reaction. p14 (ARF) , p15 (INK4B) , p16 (INK4A) , and RB hypermethylation were observed in 30 (34.1%), 50 (56.8%), 62 (70.5%), and 24(27.3%) of 88 hepatocellular carcinomas, respectively. Methylation frequencies of them between HCC with HBV infection and HCC without it were 43.8% versus 8.3 % (p14 (ARF) ), 68.9% versus 25% (p15 (INK4B) ), 90.6% versus 16.7% ( p16 (INK4A) ), and 28.1 % versus 25% (RB), respectively. In HBV-associated HCC, the numbers of methylated genes were also more than HCC without virus infection, more than two methylated genes were seen in 48 of 64 (75 %) cases; more than three methylated genes were found in 32 of 64 (50%); correspondently, no one case has more than two genes methylated. p18 (INK4C) methylation product was not found in cancerous or non-cancerous tissues of 88 HCC. HBV infection is associated with p14 (ARF) , p15 (INK4B) , p16 (INK4A) , and RB gene methylation (P = 0.048, 0.035, 0.02); HBV-DNA replication is associated with p14 (ARF) , p15 (INK4B) , p16 (INK4A) , and RB gene methylation (P = 0.048, 0.035, 0.02); high rate of p14 (ARF) , p15 (INK4B) , and p16 (INK4A) in HCC with HBV infection suggests that HBV-induced hypermethylation may be one of the mechanisms of HBV involved in hepatocellular carcinogenesis.