Abstract 4106: Lyn kinase promotes metastasis through EMT in cancers
Authors: Thaper Daksh , Vahid Sepideh , Nip Ka Mun , Ketola Kirsi , Bishop Jennifer , Zoubeidi Amina 
Published: August 2015

Introduction: Metastasis is the most common cause of death from cancer and occurs when malignant cells discard epithelial restraints and acquire invasive abilities, facilitating their dissemination to permissive micro-environments. This process is enhanced by tumor cell activation of Epithelial Mesenchymal Transition (EMT), a (normally embryonic) developmental program in which epithelial cells assume a mesenchymal phenotype during gastrulation and organogenesis, allowing single cell invasive movement away from the ectodermal layer. Recent evidence strongly implicates EMT induction in malignant progression and treatment resistance. For example, EMT regulatory transcription factors are required for breast cancer metastasis. Several oncogenic pathways (growth factors, Src family, MAPK, AKT) induce EMT. Lyn tyrosine kinase, a member of Src family tyrosine kinase is up-regulated in advanced prostate cancer and has been reported to correlate with aggressive breast cancer. Our objective is to determine the role of Lyn tyrosine kinase in EMT.

Methods: LNCaP, BT-549, UC-13 cells were transfected with Lyn siRNA; EMT markers were monitored by western blot and qRT-PCR and immunofluorescence, migration by scratch assay, invasion by Boyden chamber and matrix metalloproteinase (MMP) activity by Zymography. Lyn specific Kinase inhibitor Bafetinib will also be used along with over-expression experiments with Lyn Kinase Dead and Constitutively active mutants.

Results: Here we report that Lyn expression is low in epithelial cells and is up-regulated in mesenchymal cells. Targeting Lyn using siRNA decreases EMT markers (Fibronectin, Vimentin) at both mRNA and protein levels while increasing the epithelial marker (E-cadherin). Moreover, we found that targeting Lyn by siRNA/shRNA and small molecule inhibitor Bafetinib decreases cell migration, invasion and the activity of MMPs. This decrease in mesenchymal phenotype can be attributed to the decrease in the amount of Slug and Snail, transcriptional repressors of E-Cadherin and activators of Vimentin. Consequently, we also found that over-expressing Lyn in both as WT or constitutively active (CA) mutant rescues expression of Slug and Snail, inducing EMT, increased cell migration and invasion while Kinase Dead (KD) mutant has no effect.

Conclusion: Expression of Lyn kinase can be correlated to low prognosis and aggressive/metastatic phenotype. We show that targeting Lyn activity initiates a switch to a more epithelial phenotype reducing cell migration and invasion.

Impact: The data suggests that Lyn tyrosine kinase plays a role in Epithelial Mesenchymal Transition and could be considered as a target for metastatic disease; especially in the more aggressive forms of cancer like Triple Negative Breast Cancer or Castration Resistant Prostate Cancer. This could be a realistic therapeutic option, as the Lyn small molecule inhibitor Bafetinib, is currently in clinical trials for treatment of several cancers.

Note: This abstract was not presented at the meeting.

Citation Format: Daksh Thaper, Sepideh Vahid, Ka Mun Nip, Kirsi Ketola, Jennifer Bishop, Amina Zoubeidi. Lyn kinase promotes metastasis through EMT in cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4106. doi:10.1158/1538-7445.AM2015-4106