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Cancer metastasis is a major cause of mortality, with Epithelial-to-Mesenchymal Transition (EMT) playing a role in facilitating increased invasion and motility. During metastasis, epithelial cells detach from the primary tumor and may acquire a mesenchymal phenotype which allows cells to more effectively migrate and invade. EMT is a biological process that plays an important role in morphogenesis, cell adhesion, wound repair, tissue fibrosis, and cancer metastasis. EMT is characterized by a panel of molecular markers, which is limited since several lack specificity for given phenotypes. Additionally, molecular markers can be non-specific in cells, making it difficult to assess EMT progression. Metastasis and EMT involve several processes highly dependent on the cell’s intrinsic mechanical and biophysical properties. Although the signaling events during EMT are known, the mechanical and biophysical mechanisms governing EMT are not well established. Currently, there is limited information about how the tumor’s mechanical and biophysical properties influence EMT and metastasis. In Chapter 2, we address these knowledge gaps. Major findings for Chapter 2 include: (1) EMT progression using TGF-ß timecourse in the canonical model (A549 lung cancer cells) can be characterized with biomechanical features. (2) Cell stiffness correlated with different migration modalities during EMT, where increased stiffness prompts detachment and subsequent cell compliance to promote invasion. (3) The findings suggest that targeting tumor cell mechanics can influence detachment, the initial stage of metastasis. Following the canonical model, TGF-ß induced EMT in pancreatic cancer cells (Panc1) and non-cancer keratinocytes (HACAT) was evaluated. Major findings for Chapter 3 include: (1) In both models biomechanical features can assess EMT progression. Cell adhesion and stiffness represent the more robust features. Similar trends shown in the cancer models. (3) Cell stiffness remained the distinct biomechanical feature differentiating the EMT models. (4) Both cancer models had advantages during TGF-ß induced EMT, where increased stiffness promoted detachment, followed by decreased stiffness to aid in metastasis. Results from Chapters 2 and 3 suggest that altering tumor mechanics is a viable way to mitigate the initial stages of metastasis, and cell adhesion and stiffness represent the robust biomechanical features during EMT progression. Chapter 4 builds off previous work with myoferlin (MYOF), a membrane repair protein, regulated biomechanical changes in breast cancer cells and EMT, wherein MYOF deficiency (MYOFKD) promoted a reverse-EMT, increased collective migration, and reduced cell traction and stiffness and invasive processes. MYOF may represent a novel prognostic marker, and a broader indicator of metastasis and EMT. Further, cell resistance to tyrosine kinase inhibitors (TKI) can form an EMT. Major findings of Chapter 4 include: (1) MYOF mRNA expression increased in non-lymphoid versus lymphoid cancer cells, and likewise from small cell to non-small cell lung cancers (NSCLC). PC9 NSCLCs gained TKI resistance with unchanged MYOF expression. (2) EMT molecular markers were unchanged by MYOFKD during TGF-ß induced EMT in A549 NSCLCs. Cell adhesion strength increased in MYOFKD cells. (3) MYOFKD reduced cell detachment during the canonical EMT model. MYOFKD may be involved in reverting to the normal TGF-ß signaling events of apoptosis in lung cancer cells. |
