Abstract 1584: Musashi-2 (MSI2) drives TGFBR1/SMAD3 dependent partial EMT and supports VEGFR2 expression and metastasis of human and mouse NSCLC cells
Authors: Kudinov Alexander , Deneka Alexander , Nikonova Anna , Serebriiskii Ilya , Beck Tim N. , Cai Qi , Egleston Brian L. , Nicolas Emmanuelle , Borghaei Hossein , Gibbons Don , Kurie Jonathan , Golemis Erica A. , Boumber Yanis 
Published: July 2016

Abstract
About 221,200 new patients will be diagnosed with lung cancer and ∼158,040 will succumb to this disease in the United States in 2015. Non-small cell lung cancer (NSCLC) has a 17.4% overall 5-year survival, with metastasis contributing to the vast majority of deaths. Analyzing NSCLC tumors spontaneously arising in KrasLA1/+; P53R172HG/+ (KP) mice, we identified Musashi-2 (MSI2) protein, a stem cell-associated factor that is regulates mRNA translation, as upregulated in the metastasis-competent mouse cell lines. Importantly, MSI2 shRNA depletion in either mouse or human NSCLC cells decreased invasion in Matrigel in vitro and decreased metastasis upon orthotopic injection 129Sv immunocompetent mice in vivo. Mechanistically, by both overexpressing Msi2 cDNA in 393p murine NSCLC and shRNA depleting MSI2 in four independent mouse and human NSCLC cell lines, we defined MSI2 as a driver of a partial epithelial-mesenchymal transition (EMT) program in NSCLC cells. In support of EMT, MSI2 increases the expression of the Snail and Slug pro-EMT transcription factors, as well as the mesenchymal protein vimentin (VMN). MSI2 also downregulates expression of the extracellular matrix component fibronectin (FN1) and tight junction proteins Claudin-3, 5 and 7. However, MSI2 also inhibits protein expression of Zeb-1 and Zeb-2, while sustaining expression of E-cadherin (E-Cad), associated with epithelial identity. Moreover, MSI2 represses NOTCH-1 and upregulates VEGFR2 at the mRNA and protein levels. This is of interest, as NOTCH-1 has been shown to regulate VEGFR2 in angiogenic signaling. We found that knockdown of NOTCH-1 in MSI2-depleted mouse and human NSCLC cells rescued the loss of VEGFR2 expression, suggesting MSI2 increases VEGFR2 expression in a NOTCH-1 dependent manner. Additionally, siRNA of VEGFR2 in the highly metastatic NSCLC cell line 344sq significantly decreased Matrigel invasion, but had only a limited effect in 344sq derivative lines with stable depletion of MSI2, and human NSCLC experiments are ongoing. Together, these results indicate a possible role of MSI2/NOTCH-1/VEGFR2 axis in NSCLC, and suggest that MSI2 connects cancer cell stemness, EMT, and angiogenesis in lung cancer metastasis.
Citation Format: Alexander Kudinov, Alexander Deneka, Anna Nikonova, Ilya Serebriiskii, Tim N. Beck, Qi Cai, Brian L. Egleston, Emmanuelle Nicolas, Hossein Borghaei, Don Gibbons, Jonathan Kurie, Erica A. Golemis, Yanis Boumber. Musashi-2 (MSI2) drives TGFBR1/SMAD3 dependent partial EMT and supports VEGFR2 expression and metastasis of human and mouse NSCLC cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1584.