More than a biomarker: vimentin function in lung cancer invasion and metastasis Restricted; Files Only

Richardson, Alessandra (Fall 2017)

Permanent URL: https://etd.library.emory.edu/concern/etds/gf06g264k?locale=en
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Abstract

Vimentin expression has been shown for decades to correlate with increased metastatic potential across solid tumor types including lung, breast and prostate cancers. However, it has never been demonstrated whether vimentin is a necessary contributor to the metastatic cascade. The work in this dissertation demonstrates with in vitro models, in vivo models, and clinical samples that vimentin is more than a biomarker and contributes to the metastatic cascade through a role in the tumor microenvironment.

We identified a role for vimentin in cell motility using lung cancer cell line models. Here we demonstrate that vimentin enters focal adhesion sites where it acts as a scaffold to promote EGF mediated phosphorylation of VAV2, the guanine exchange factor for the rho GTPase Rac1. Phosphorylation of VAV2 activates Rac1 to its GTP bound form where it promotes FAK activation at focal adhesion sites.

To further elucidate the role of vimentin in lung cancer metastasis, we moved our work into a genetically engineered mouse model (GEMM). For this study we developed a novel GEMM by crossing the Cre-dependent lung cancer metastasis model LSL-KrasG12D/LKB1fl/fl  (KLV+/+) to a whole body vimentin knockout mouse to generate the LSL-KrasG12D/LKB1fl/fl/Vim-/- mouse (KLV-/-). Comparison of the KLV models show that vimentin loss does not impact tumor formation or burden. However, loss of vimentin does significantly reduce the rate of metastasis to the mediastinal lymph node. Immunohistochemical analysis of the primary lung tumors demonstrates that vimentin expression is reserved to the tumor microenvironment. This expression pattern was consistent with lung adenocarcinoma patient tissue samples irrespective of genotype. Further analysis shows vimentin to be predominantly expression in cancer-associated fibroblasts (CAFs). These CAFs support collective invasion and metastasis via heterotypic CAF-cancer cell interactions.

 

Overall this dissertation highlights the importance of vimentin as a functional player in cell motility and demonstrates a novel role in lung adenocarcinoma metastasis. Follow-up studies on the impact of vimentin on the tumor microenvironment will provide further insight on the role of vimentin on tumor progression.

Table of Contents

1.     Introduction …………………………………………………………5

1.1.       Lung cancer ………………………………………………....6

1.1.1.     Histology …………………………………………………………....6

1.1.2.     Genetic drivers ……………………………………………………... 8

1.1.3.     Current treatments …………………………………………………..9

1.2.       Metastasis …………………………………………...............11

1.2.1.     Migration strategies …………………………………………………12

1.2.1.1.         Focal adhesion signaling ………………………………........ 15

1.2.2.     Intravasation, circulation, extravasation …………………………….15

1.3.       Tumor microenvironment ……………………....................... 17

1.3.1.     Microenvironmental factors …………………………………………18

1.3.1.1.         Fibroblasts……………………………………………………18

1.3.1.2.         Immune cells…………………………………………………19

1.3.1.3.         Vasculature…………………………………………………..19

1.3.1.4.         The role of the microenvironment in metastasis……………. 20

1.4.       Metastatic biomarkers………………………………………..20

1.4.1.     History and applications ……………………………………………. 20

1.5.       Vimentin structure and function …………………………......21

1.5.1.     Intermediate filament structure ……………………………………...21

1.5.2.     Vimentin in signal transduction …………………………………......22

1.6.  Current research models ………………………………………………...….22

1.6.1.     Transplantation models ……………………………………..............24

1.6.2.     Genetically engineered mouse models (GEMMs) ………………….26

1.7.  Scope of Dissertation ……………………………………………………....27

2.     Vimentin regulates lung cancer cell adhesion through a VAV2-Rac1 pathway to control focal adhesion kinase activity……………………………………..…….29

2.1.  Introduction…………………………………………………………..……..30

2.2.  Experimental Procedures……………………………………………..……. 31

2.3.  Results…………………………………………………………………..…..39

2.4.  Discussion…………………………………………………………..………62

3.     Vimentin is required for lung adenocarcinoma metastasis via heterotypic tumor cell-cancer-associated fibroblast interactions during collective invasion………..…..65

3.1.  Introduction…………………………………………………………..……..66

3.2.  Experimental Procedures…………………………………………….……..67

3.3.  Results……………………………………………………………...….........74

3.4.  Discussion…………………………………………………………………..103

4.     Discussion of Dissertation……………………………………………………….105

4.1.  Vimentin is identified as a key player in lung cancer invasion and metastasis 106

4.2.  A novel mechanism of vimentin-mediated cell adhesion in vitro………….107

4.3.  Vimentin is necessary for lung cancer metastasis in vivo…………………..108

4.4.  Lung adenocarcinoma metastasis occurs via vimentin-mediated collective invasion……………………………………………………………………...109

4.5.  Context-dependent roles for vimentin…………………………………….…112

4.6.  Postulated mechanisms of vimentin-mediated stroma-cancer cell crosstalk..113

4.7.  Future directions and translational implications………………..……….....114

5.     References …………………………………………………………..…………..116

 

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