Regulation of Desmosomal Cadherins in Oral Cancer

描述（由申请人提供）：钙粘蛋白粘附的可逆调节在上皮肿瘤细胞进展中起关键作用。 虽然大多数研究都集中在经典的钙粘蛋白在癌症中的调节，很少有人注意到桥粒钙粘蛋白的重要性。 我们最近发现，表皮生长因子受体（EGFR）的抑制导致桥粒钙粘蛋白在口腔鳞状细胞癌（OSCC）细胞中的积累，增强桥粒组装和增加细胞间的粘附强度。 我们假设EGFR抑制干扰桥粒钙粘蛋白内化和/或进入降解途径。 支持这一观点，EGFR抑制剂阻断桥粒芯糖蛋白2（Dsg 2）在细胞质池中的积累，这与抑制Dsg 2胞外域的基质金属蛋白酶（MMP）依赖性加工及其细胞质结构域的酪氨酸磷酸化相关。 此外，MMP抑制阻断了Dsg 2的内化，但不是E-钙粘蛋白，在高度侵袭性的SCC 68细胞，提高的可能性，调节桥粒和经典钙粘蛋白可以解偶联机械。 我们提出了一个模型，EGFR酪氨酸磷酸化和MMP依赖的切割合作，以促进内化和降解的桥粒钙粘蛋白复合物，导致粘附力减弱，增加浸润和转移的口腔鳞癌。 我们将通过以下方式对此进行测试：1）使用OSCC的共聚焦显微镜、活细胞成像和生物化学分析的组合来评估EGFR/MMP抑制是否通过阻止Dsg 2/Dsc 2的内化和/或促进内体再循环而使桥粒钙粘蛋白从降解途径转向，2）定义Dsg 2胞质结构域和相关的犰狳蛋白对调节桥粒钙粘蛋白细胞表面表达和内化的贡献，和3）测定MMP依赖性Dsg 2切割对体外桥粒钙粘蛋白复合物的内化和降解以及体内肿瘤生长、侵袭和转移的贡献。 这些研究将有助于建立一个范式，桥粒钙粘蛋白是如何调节的信号在肿瘤微环境中的头颈癌。 这项工作的结果也将有重要的意义，为未来的治疗策略的基础上，他们的钙粘蛋白和MMP的状态。

DESCRIPTION (provided by applicant): The reversible modulation of cadherin-based adhesion plays a critical role in epithelial tumor cell progression. Whereas most studies have focused on the regulation of classic cadherins in cancer, less attention has been paid to the importance of desmosomal cadherins. We recently showed that epidermal growth factor receptor (EGFR) inhibition results in the accumulation of desmosomal cadherins in oral squamous cell carcinoma (OSCC) cells, enhancing desmosome assembly and increasing intercellular adhesive strength. We hypothesized that EGFR inhibition interferes with desmosomal cadherin internalization and/or entry into a degradative pathway. Supporting this idea, EGFR inhibitors block accumulation of desmoglein 2 (Dsg2) in a cytoplasmic pool, correlated with inhibition of matrix metalloproteinase (MMP)-dependent processing of the Dsg2 ectodomain and tyrosine phosphorylation of its cytoplasmic domain. Furthermore, MMP-inhibition blocked internalization of Dsg2, but not E-cadherin, in highly invasive SCC68 cells, raising the possibility that regulation of desmosomal and classic cadherins can be uncoupled mechanistically. We propose a model whereby EGFR tyrosine phosphorylation and MMP-dependent cleavage cooperate to promote internalization and degradation of the desmosomal cadherin complex, leading to weakened adhesion, increased invasion and metastasis of OSCC. We will test this by: 1) using a combination of confocal microscopy, live cell imaging and biochemical analysis of OSCC to assess whether EGFR/MMP inhibition diverts desmosomal cadherins from a degradative pathway by preventing internalization and/or promoting endosome recycling of Dsg2/Dsc2, 2) defining the contribution of Dsg2 cytoplasmic domain and associated armadillo proteins to regulation of desmosomal cadherin cell surface expression and internalization, and 3) determining the contribution of MMP-dependent Dsg2 cleavage to internalization and degradation of the desmosomal cadherin complex in vitro and to tumor growth, invasion and metastasis in vivo. These studies will help to establish a paradigm for how desmosomal cadherins are regulated by signals in the tumor microenvironment of head and neck cancers. Results from this work will also have important implications for the future tailoring of therapeutic strategies based on their cadherin and MMP status.