The role of Vimentin in cell adhesion and lung cancer metastasis

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PROJECT SUMMARY Non-small cell lung cancer (NSCLC) is the most common type of lung cancer. Due to frequent diagnosis during advanced stages of the disease when metastasis of the primary tumor has already occurred, NSCLC has a 5- year survival rate of only 15%. Once metastasis has already occurred, the disease is extremely difficult to treat, making identification of the molecular mechanism of metastasis crucial for advances in treatment. The intermediate filament, vimentin, is upregulated in migrating cells, indicating a role in metastasis. Vimentin is a dynamic protein whose assembly and disassembly is critical for the formation of new focal adhesions that regulate cell adhesion. In addition to playing a structural role, evidence suggests that vimentin also plays a signaling role at the focal adhesions. The molecular link between vimentin and the regulation of cell adhesion remains an unexplored field. Focal adhesion kinase (FAK), which is activated by phosphorylation at Y397, also localizes to the focal adhesions. As evident from our preliminary data, vimentin filaments are directed into the phosphorylated FAK sites indicating a potential molecular link between vimentin and FAK phosphorylation. Our preliminary western blot data of lysates from vimentin depleted and control cells also shows that a loss of vimentin expression results in reduced FAK expression and phosphorylation at Y397. Additionally, several phosphorylation sites have been identified on vimentin and have been linked to the disassembly and assembly processes at focal adhesions. The molecular mechanism by which this occurs has not been explored yet. In this proposal we hypothesize that vimentin interacts with FAK to regulate activation and expression of FAK thereby increasing cell adhesion to facilitate metastasis of the primary lung cancer tumor. To test this we will address two specific aims: 1) To determine the molecular mechanism by which vimentin regulates cell adhesion 2) To determine whether vimentin is necessary for lung tumor metastasis in vivo. In the first aim, we will specifically look at the molecular mechanisms by which vimentin regulates FAK expression and activation. We will also test whether three specific vimentin phosphorylation sites (Serines 38, 56 and 72), which are important for vimentin assembly and disassembly, play a role in FAK activation and cell adhesion. In the second aim we will create a novel in vivo mouse model by crossing a vimentin null mouse (vim -/-) to the LKB-/- KrasG12D lung cancer mouse model to determine whether vimentin expression is required for metastasis of the primary lung cancer tumor. This will be the first time such a mouse model will be created to look at the requirement of vimentin expression for metastasis. Understanding how vimentin expression regulates cell adhesion at a molecular level will identify novel therapeutic targets to inhibit metastasis and greatly improve the prognosis of NSCLC patients.