Purpose: A malfunction of retinoid X receptor-a (RXRa) due to phosphorylation by the Ras/mitogen-activated protein kinase signaling pathway is associated with the development of hepatocellular carcinoma (HCC). The humanized anti-HER2 monoclonal antibody trastuzumab inhibits the activation of HER2 and its multiple downstream signaling pathways, including the Ras/mitogen-activated protein kinase pathway. In this study, the effects of phosphorylation of RXRa on the ability of RXRa ligand 9-cis-retinoic acid (9cRA) and trastuzumab to inhibit growth of HCC cells was examined. Experimental Design: The effects of a combination of 9cRA plus trastuzumab on the inhibition of cell growth in HLF human HCC cells which express constitutive activation of HER2 protein were examined. Results: The combination of 9cRA plus trastuzumab synergistically inhibited the growth of HLF cells without affecting the growth of Hc normal human hepatocytes. Combined treatment with these agents acted synergistically to induce apoptosis in HLF cells.The treatment of HLF cells with trastuzumab alone inhibited the phosphorylation of HER2, RXRa, ERK, Akt, and Stat3 proteins and these effects were enhanced when the cells were cotreated with 9cRA. Reporter assays indicated that the combination of 9cRA plus trastuzumab markedly increased both the retinoic acid responsive element and retinoid X responsive element promoter activities in HLF cells. Conclusion: 9cRA and trastuzumab cooperatively inhibit the activation of HER2 and its downstream signaling pathways, subsequently inhibiting the phosphorylation of RXRa and the growth of HCC cells.This combination might therefore be effective for the chemoprevention and chemotherapy of HCC.
Transnasal ultrathin esophagogastroduodenoscopy (N-EGD) with less gagging reflexes under non-sedation is likely suitable for the diagnosis of gastroesophageal reflux disease (GERD), however, N-EGD might have drawbacks, including its low image resolution. Limited information is available regarding the diagnosability of N-EGD for GERD. We compared the utility and gagging reflexes of three different endoscopies, including N-EGD, ultrathin transoral EGD (UTO-EGD) and conventional oral EGD (CO-EGD), in the diagnosis of GERD. We performed screening endoscopy in 1580 patients (N-EGD n=727, UTO-EGD n=599, CO-EGD n=254) and compared the frequency distributions of the severity of reflux esophagitis, hiatus hernia, and Barrett's epithelium to estimate the diagnostic performance of each endoscopy. We also analyzed patients' tolerability of endoscopy by the subjective evaluation of gagging reflexes. In the diagnosis of reflux esophagitis and Barrett's epithelium, there was no significant difference in the frequency distributions of the severity of the diseases among three EGDs. However, the incidence of Barrett's epithelium was higher than that in the previous nationwide survey of GERD in Japan. The evaluated size of hiatus hernia was smaller in N-EGD than in two other peroral endoscopies. The size of hiatus hernia correlated significantly with severity of gagging reflexes that was also lowest when diagnosed with N-EGD. N-EGD had an equivalent performance in the diagnosis of reflux esophagitis and Barrett's epithelium compared with CO-EGD. Enlargement of hiatus hernia induced by gagging reflexes was minimal in N-EGD, resulting in its better performance in the diagnosis of Barrett's epithelium.
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