PLXDC2通过促进侵袭性伪足形成而调控胃癌细胞侵袭转移的作用及分子机制研究

Invidopodia formation plays a critical role in the invasion and metastasis of gastric cancer cells. However, the definite molecular mechanisms remain ambiguous. We have proved that scinderin promotes the invasion and metastasis of gastric cancer cells through modulating filopodia formation supported by our last National Natural Science Foundation of China. Although the phosphorylation of cortactin at focal adhesions plays a central role in the formation of invadopodia, the mechanisms are not fully understood. Studies demonstrated that PLXDC2 was able to self-activate via autophosphorylation without extracellular signals and that PLXDC2 had the capability to directly interact with cortactin. We have found that in gastric cancer cells, PLXDC2 promoted both the phosphorylation of cortactin and invadopodia formation. So we suppose that the highly expressed PLXDC2 in gastric cancer cells promotes invadopodia formation by recruitment of cortactin and facilitating its phosphorylation independent of extracellular signals. We will perform a series of experiments to verify the hypothesis and uncover the role of PLXDC2 in invadopodia formation of gastric cancer cells. The results would expand the knowledge of the mechanisms underlying invasion and metastasis of gastric cancer and provide new markers for gastric cancer metastasis and potential therapeutic targets for gastric cancer.

侵袭性伪足的形成在胃癌侵袭转移中发挥关键作用，但其机制仍不明了。我们在上一基金中已证明肌切蛋白能促进胃癌细胞伪足形成而显著提高其侵袭转移能力。侵袭性伪足形成的核心步骤是局部粘着斑处cortactin的磷酸化，但其调控机制尚未完全阐明。有研究发现PLXDC2能够在不依赖胞外信号的情况下发生自身磷酸化而激活；也有研究报道PLXDC2可以直接同cortactin相互作用。我们前期研究发现，胃癌细胞中高表达的PLXDC2具有促进cortactin磷酸化及伪足形成的能力。由此我们推测：PLXDC2在胃癌中高表达，可能在无胞外信号刺激的情况下发生自身磷酸化而激活，继而募集并诱导cortactin磷酸化而促进伪足生成。我们拟通过临床样本和体内外实验证实这一假设，阐明PLXDC2在胃癌细胞侵袭性伪足形成中的作用及分子机制，以期对胃癌侵袭转移机制有新的认识,并有望为胃癌诊疗提供新的标志物和靶点。

背景 PLXDC2（Plexindomaincontaining2）是一肿瘤蛋白，已被报道在多种人类恶性肿瘤中表达。然而，其在胃癌中的表达和作用仍不清楚。.方法 采用免疫组织化学染色法检测170例胃癌标本中PLXDC2的表达情况，并对其临床相关性进行统计学分析。用于构建好的PLXDC2沉默和过表达胃癌细胞模型进行了Matrigel-transwell侵袭试验和小鼠腹膜内转移实验，以探索PLXDC2在胃癌细胞中的生物学功能。RNA-Seq、免疫荧光和Co-IP分析用于研究PLXDC2在胃癌中作用的潜在分子机制。.结果 PLXDC2在胃癌组织中高表达，表达水平与临床病理特征呈正相关，与患者预后呈负相关。Cox回归分析确定PLXDC2为患者的独立预后指标。敲低PLXDC2显着抑制了胃癌细胞的体外侵袭和体内转移，而过表达PLXDC2导致相反的效果。从机制上讲，PLXDC2通过与PTP1B（重要的酪氨酸磷酸酶）物理相互作用来抑制磷酸化Cortactin的去磷酸化，从而促进侵袭性的形成。.结论 PLXDC2通过抑制PTP1B促进侵袭性伪足形成，进而促进胃癌的侵袭和转移，可作为该病的潜在预后生物标志物和治疗靶点。