Abstract 5090: Exportin-1 enables pro-tumorigenic metabolic reprogramming of lung fibroblasts through relocalization of p53 and p62/SQSTM1
Authors: Bruccoleri Antonina , Andriani Francesca , Facchinetti Federica , Pastorino Ugo , Sozzi Gabriella , Roz Luca 
Published: August 2018

Abstract
Bi-directional interactions between cancer cells and the surrounding microenvironment actively contribute to cancer development and progression. Cancer-associated fibroblasts (CAFs) are one of the most prevalent cellular components in the tumor microenvironment and their metabolic reprogramming towards an activated phenotype reminiscent of fibroblasts found at sites of wound healing is involved in the acquisition of pro-tumorigenic properties. Specific determinants of tumor-promoting function of fibroblasts in lung cancer are however not well characterized. Here we used microarray gene expression profiling of fibroblasts isolated from lung cancer patients and functional in vitro and in vivo assays to identify enablers of fibroblasts pro-tumorigenic activity. Gene expression profiles of CAFs and normal fibroblasts (n=60) identified increased levels of the nuclear transporter Exportin 1 (XPO1/CRM1) in patient-derived fibroblasts endowed with an in vivo pro-tumorigenic phenotype in co-injection experiments with lung cancer cells. Elevated levels of XPO1, which controls cellular localization of numerous proteins including oncosuppressors, have been observed in cancer cells but the role of XPO1-related signaling in stromal cells has not been investigated. Pharmacological inhibition of XPO1 in fibroblasts resulted in anti-proliferative effects with a G2/M cell cycle arrest linked to p53 accumulation, increased CDKN1a transcription, induction of senescence (2-4 fold increase of β-galactosidase positive cells) and accumulation of γ-H2AX foci. Interestingly these effects were persistent only in activated fibroblasts compared to control fibroblasts suggesting a central role for XPO1 in mediating and sustaining permanent reprogramming of pro-tumorigenic fibroblasts. Additionally XPO1 inhibition was associated with cellular relocalization of p62/SQSTM1, a master regulator of energy metabolism in tumor stroma. Low levels of nuclear p62 were observed in activated fibroblasts and could be restored to normal levels through XPO1-activity inhibition. p62 nuclear accumulation inhibited DNA-damage repair and reduced extracellular acidification, indicating potential modification of metabolic properties of activated fibroblasts. Consistently, in heterotypic co-cultures experiments, we found that XPO1 inhibition prevented the ability of activated fibroblasts to stimulate migration of lung cancer cell lines and to increase the frequency of CD133+ cancer stem cells thereby reducing their pro-tumorigenic activity in vivo. Overall these evidences suggest that XPO1 is a potent enabler of the tumor promoting functions of fibroblasts and that XPO1-driven metabolic reprogramming in stromal cells could be targeted to affect cancer progression.
Citation Format: Antonina Bruccoleri, Francesca Andriani, Federica Facchinetti, Ugo Pastorino, Gabriella Sozzi, Luca Roz. Exportin-1 enables pro-tumorigenic metabolic reprogramming of lung fibroblasts through relocalization of p53 and p62/SQSTM1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5090.