pH-dependent Wnt-Signaling Activation and Gastric Carcinogenesis

在患者和模式生物中，Wnt信号的过度激活和酸性细胞外pH与癌症的发生/发展相关。胃癌是癌症相关死亡的最常见原因之一。胃质子泵ATP4使胃腔酸化。研究表明，ATP4在非洲爪哇激活Wnt信号是必需的，而抑制ATP4诱导的人胃癌细胞选择性凋亡是必需的。这项研究将阐述ATP4和低pH如何在Wnt信号激活和胃癌中发挥作用。将在人类肠道细胞系上进行实验，以测试细胞外pH的变化是否以及如何通过共同受体LRP6促进Wnt信号的激活，以及这种激活如何影响基因表达、表观遗传修饰和细胞向癌细胞的转化。与其他模式生物不同，失去质子泵不会影响小鼠发育中的Wnt信号。然而，ATP4缺陷小鼠的胃成熟似乎受到了影响。这也表明了ATP4在小鼠中的上下文相关信号特性。因此，在ATP4缺陷小鼠的胃肠道发育和成熟过程中，将监测Wnt信号的活性。此外，其他跨膜质子转运体在小鼠发育过程中调节Wnt信号的可能性将通过胚胎表达分析和使用小鼠细胞系进行的功能丧失实验来解决。综上所述，本项目将阐明质子泵和pH依赖的Wnt信号激活和癌症发生/发展的分子机制。此外，还将分析pH和质子泵在小鼠发育和胃肠道成熟中的作用。这些结果将有助于了解Wnt信号在胃肠道组织中的激活和致癌机制，最终可能导致新的癌症治疗方法的开发。

Over-activation of Wnt-signaling and acidic extracellular pH correlate with cancer initiation/progression in patients and model organisms. Gastric cancer is one of the most common causes for cancer-related deaths. The gastric proton pump ATP4 acidifies the gastric lumen. ATP4 was shown to be required for Wnt-signaling activation in Xenopus, and inhibition of ATP4 induced selective apoptosis in human gastric cancer cells. This study will address how ATP4 and low pH act during Wnt-signaling activation and in gastric cancer. Experiments will be performed on human intestinal cell lines in order to test if and how changes in the extracellular pH promote Wnt-signaling activation via the co-receptor LRP6, and how this activation affects gene expression, epigenetic modifications and transformation of cells into cancer cells. In contrast to other model organisms, loss of proton pumps did not affect developmental Wnt-signaling in the mouse. Nevertheless, maturation of the stomach seemed to be affected in ATP4-deficient mice. This indicated context-dependent signaling properties of ATP4 in the mouse as well. Thus, Wnt-signaling activity will be monitored during development and maturation of the gastrointestinal tract in ATP4-deficient mice. Furthermore, the possibility that other transmembrane proton-transporters regulate Wnt-signaling during mouse development will be addressed by expression analysis in embryos and in loss-of-function experiments using murine cell lines. In summary, this project will elucidate the molecular mechanism of proton pump- and pH-dependent Wnt-signaling activation and cancer initiation/progression. Moreover, the role of pH and proton pumps in mouse development and gastrointestinal maturation will be analyzed. The results will help to understand the mechanism of Wnt-signaling activation and carcinogenesis in gastrointestinal tissues, which may ultimately lead to the development of new cancer therapies.