Gastric cancer prevention by demethylation

Amide-type local anesthetics may suppress tumor cell proliferation and sensitize Human Hepatocellular Carcinoma Cells to Cisplatin via upregulation of RASSF1A expression and demethylation

Background: It has been reported that local anesthetics are toxic to various types of cells. Furthermore, several local anesthetics have been confirmed to exert demethylation effects and regulate the proliferation of human cancer cells. Our previous findings suggest that lidocaine may exert potential antitumor activity and enhance the sensitivity of cisplatin to hepatocellular carcinoma in vitro and in vivo. A recent study proved that lidocaine sensitizes breast cancer cells to cisplatin via upregulation of RASSF1A, a promotor of tumor suppressive gene (TSG) demethylation. We sought to determine whether amide-type local anesthetics (lidocaine, ropivacaine and bupivacaine) exert growth-inhibitory effects on human hepatoma cells and to determine whether amide-type local anesthetics sensitize human hepatoma cells to cisplatin-mediated cytotoxicity via upregulation of RASSF1A expression.

Methods: Human hepatoma cell lines HepG2 and BEL-7402 were incubated with lidocaine, ropivacaine and bupivacaine. The viability of local anesthetic-treated cells with or without cisplatin was investigated. Further, we evaluated RASSF1A expression after treatment of HepG2 and BEL-7402 cells with three local anesthetics and determined the influence of RASSF1A expression on the toxicity of cisplatin to these cells.

Results: The viability of HepG2 and BEL-7402 cells was significantly decreased by treatment with amide-type local anesthetics (lidocaine, ropivacaine and bupivacaine). In these cells, the combination treatment with cisplatin and local anesthetics exhibited a stronger reduction in viability. Lidocaine, ropivacaine and bupivacaine promoted a significant increase in RASSF1A expression and a decrease in RASSF1A methylation. The combined treatment with both local anesthetics and cisplatin resulted in a significantly lower level of HepG2 and BEL-7402 cell viability than that with singular local anesthetics or cisplatin treatment. Moreover, local anesthetics enhanced the cytotoxicity of cisplatin against HepG2 and BEL-7402 cells, accompanied by an increase in RASSF1A expression.

Conclusions: These data indicated that amide-type local anesthetics (lidocaine, ropivacaine and bupivacaine) have growth-inhibitory and demethylation effects in human hepatoma cells. We also found that these amide local anesthetics may enhance the cytotoxicity of cisplatin in human hepatocellular carcinoma cells possibly via upregulation of RASSF1A expression and demethylation.

Silencing of ATP4B of ATPase H+/K+ Transporting Beta Subunit by Intragenic Epigenetic Alteration in Human Gastric Cancer Cells

The ATPase H+/K+ Transporting Beta Subunit (ATP4B) encodes the β subunit of the gastric H+, K+-ATPase, which controls gastric acid secretion and is therefore a target for acid reduction. Downregulation of ATP4B was recently observed in human gastric cancer (GC) without known mechanisms. In the present study, we demonstrated that ATP4B expression was decreased in human GC tissues and cell lines associated with DNA hypermethylation and histone hypoacetylation of histone H3 lysine 9 at its intragenic region close to the transcriptional start site. The expression of ATP4B was restored in GC cell lines by treatment with the DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine (5-AZA), or histone deacetylase inhibitor, trichostatin A (TSA), with further enhancement by combined treatment with both drugs. In contrast, 5-AZA had no effect on ATP4B expression in human hepatocellular carcinoma (HCC) and pancreatic cancer cell lines, in which ATP4B was silenced and accompanied by intragenic methylation. Chromatin immunoprecipitation (ChIP) showed that, in BGC823 GC cells, histone H3 lysine 9 acetylation (H3K9ac) was enhanced in the intragenic region of ATP4B upon TSA treatment, whereas 5-AZA showed a minimal effect. Additionally, ATP4B expression enhanced the inhibitory effects of chemotherapeutic mediation docetaxel on GC cell growth. Thus, as opposed to HCC and pancreatic cancer cells, the silencing of ATP4B in GC cells is attributable to the interplay between intragenic DNA methylation and histone acetylation of ATP4B, the restoration of which is associated with a favorable anticancer effect of docetaxel. These results have implications for targeting epigenetic alteration at the intragenic region of ATP4B in GC cells to benefit diagnosis and treatment of GC.

Lidocaine sensitizes the cytotoxicity of cisplatin in breast cancer cells via up-regulation of RARβ2 and RASSF1A demethylation

It has been reported that lidocaine is toxic to various types of cells. And a recent study has confirmed that lidocaine exerts a demethylation effect and regulates the proliferation of human breast cancer cell lines. To recognize a potential anti-tumor effect of lidocaine, we evaluated the DNA demethylation by lidocaine in human breast cancer lines, MCF-7 and MDA-MB-231 cells, and determined the influence of demethylation on the toxicity to these cells of cisplatin, which is a commonly utilized anti-tumor agent for breast cancer. Results demonstrated that lidocaine promoted a significant global genomic demethylation, and particularly in the promoters of tumor suppressive genes (TSGs), RARβ2 and RASSF1A. Further, the lidocaine treatment increased cisplatin-induced apoptosis and enhanced cisplatin-induced cytotoxicity. The combined treatment with both lidocaine and cisplatin promoted a significantly higher level of MCF-7 cell apoptosis than singular lidocaine or cisplatin treatment. Moreover, the abrogation of RARβ2 or RASSF1A expression inhibited such apoptosis. In conclusion, the present study confirms the demethylation effect of lidocaine in breast cancer cells, and found that the demethylation of RARβ2 and RASSF1A sensitized the cytotoxicity of cisplatin in breast cancer cells.

Combination of gefitinib and DNA methylation inhibitor decitabine exerts synergistic anti-cancer activity in colon cancer cells

Despite recent advances in the treatment of human colon cancer, the chemotherapy efficacy against colon cancer is still unsatisfactory. In the present study, effects of concomitant inhibition of the epidermal growth factor receptor (EGFR) and DNA methyltransferase were examined in human colon cancer cells. We demonstrated that decitabine (a DNA methyltransferase inhibitor) synergized with gefitinib (an EGFR inhibitor) to reduce cell viability and colony formation in SW1116 and LOVO cells. However, the combination of the two compounds displayed minimal toxicity to NCM460 cells, a normal human colon mucosal epithelial cell line. The combination was also more effective at inhibiting the AKT/mTOR/S6 kinase pathway. In addition, the combination of decitabine with gefitinib markedly inhibited colon cancer cell migration. Furthermore, gefitinib synergistically enhanced decitabine-induced cytotoxicity was primarily due to apoptosis as shown by Annexin V labeling that was attenuated by z-VAD-fmk, a pan caspase inhibitor. Concomitantly, cell apoptosis resulting from the co-treatment of gefitinib and decitabine was accompanied by induction of BAX, cleaved caspase 3 and cleaved PARP, along with reduction of Bcl-2 compared to treatment with either drug alone. Interestingly, combined treatment with these two drugs increased the expression of XIAP-associated factor 1 (XAF1) which play an important role in cell apoptosis. Moreover, small interfering RNA (siRNA) depletion of XAF1 significantly attenuated colon cancer cells apoptosis induced by the combination of the two drugs. Our findings suggested that gefitinib in combination with decitabine exerted enhanced cell apoptosis in colon cancer cells were involved in mitochondrial-mediated pathway and induction of XAF1 expression. In conclusion, based on the observations from our study, we suggested that the combined administration of these two drugs might be considered as a novel therapeutic regimen for treating colon cancer.