Abstract 1912: Inhibition of Exportin-1 function reverses the pro-tumorigenic potential of lung fibrotic microenvironments
Authors: Bruccoleri Antonina , Rondinone Ornella , Andriani Francesca , Facchinetti Federica , Tortoreto Monica , Sozzi Gabriella , Bertolini Giulia , Roz Luca 
Published: August 2019

The contribution of stromal cells to tumor progression is widely established while less is known about stromal changes that may influence the early phases of tumorigenesis such as incipient growth of (pre)neoplastic lesions or seeding and awakening of metastatic cells. We have previously characterized the pro-tumorigenic properties of lung fibroblasts identifying increased activity of the nuclear transporter Exportin-1 (XPO1) as a key driver in modulating metabolic properties of fibroblasts towards a tumor promoting phenotype through subcellular re-localization of p53 and p62/SQSTM1. Consistently, XPO1 inhibition prevented the ability of activated fibroblasts to stimulate migration of lung cancer cells and to increase the frequency of CD133+ cancer stem cells, thereby also reducing their in vivo pro-tumorigenic activity.

To test the potential of therapeutic strategies based on modification of pro-tumorigenic microenvironments we exploited a mouse model of lung fibrosis based on single intranasal administration of an adenoviral vector expressing activated TGFβ. Fibrosis was efficiently induced in both nude and SCID mice and was associated with the creation of a pro-tumorigenic milieu as tested by tail vein injection of microenvironment-responsive lung cancer cell line LT73 one month after fibrosis induction. Mice treated with AdTGFβ showed increased number of tumor cells and/or CD133+ lung cancer stem cells two months after cancer cell seeding (p&lt;0.05 for AdTGFβ vs. AdLacZ and medium alone). We also evaluated the modulation of immune cell subsets with multi parametric flow-cytometry detecting a consistent increase in neutrophils (Ly6-G+/Ly6-Clow) and a slight increase in monocyte derived macrophages (F4-80high/GR1-/CD11b+) and plasmacytoid dendritic cells (CD11c+/CD11b-) associated with upregulation of fibrosis-related miRNAs (miR-199a-5p) and induction of a pro-tumorigenic milieu. To test the efficacy of microenvironment modulating therapies we used the selective XPO1 inhibitor KPT-330. In vitro pharmacological inhibition of XPO1 was able to modulate expression of miRNAs in fibroblasts (including miR-199a-5p) and reduce fibroblast pro-tumorigenic secretory phenotype (reduction in IL-8, CXCL1, CCL2 and lactate production). For in vivo experiments animals were treated after induction of fibrosis but before injection of cancer cells to avoid confounding effects related to activity on cancer cells. XPO1 inhibition was able to convert the pro-tumorigenic potential of the fibrotic microenvironment and this was associated with a reduction of the levels of miR-199a-5p, decreased expression extracellular matrix-related genes (Sparc, Col1a1, Mmp2, Col6a1, Col6a3) and dampening of the inflammatory milieu.

Overall these findings suggest potential therapeutic efficacy of XPO1 inhibition to revert the pro-tumorigenic activity of fibrotic lung microenvironments.

Citation Format: Antonina Bruccoleri, Ornella Rondinone, Francesca Andriani, Federica Facchinetti, Monica Tortoreto, Gabriella Sozzi, Giulia Bertolini, Luca Roz. Fondazione IRCCS Ist. Inhibition of Exportin-1 function reverses the pro-tumorigenic potential of lung fibrotic microenvironments [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1912.