Abstract 1915: Deconstructing cancer stem cells: IL-6, G-CSF and Activin-A as mediators of stroma-orchestrated epithelial cells’ dedifferentiation
Authors: Rodrigues Carlos F. , Serrano Eurico , Cunha Marco , Patrício Maria I. , Val Mariana , Fonseca João , Gomes Célia , Abrunhosa Antero , Paiva Artur , Botelho Filomena , Carvalho Lina , Carreira Isabel M. , Carmen Alpoim 
Published: July 2017

Abstract
Intercellular communication in cancer is a deceiving and extremely efficient process through which the corporal machinery is hijacked by a panoply of cellular and molecular strategies turning the entire human body into an evolutionary arena. The extensive crosstalk mediated by cytokines and chemokines overcome the inefficiency of the invasion-metastasis cascade, thus allowing the development of the often-fatal metastatic disease. Cancer stem cells (CSCs) have recently been implicated in major steps of the tumorigenic process, namely in tumor initiation, metastasis formation and tumor relapse following therapy. Yet, despite their relevance, the exact mechanisms underlying their formation are still unclear. After observing that the malignant human bronchial epithelial RenG2 cells dedifferentiated following culture in the subcutaneous mouse lumbar region, co-cultures of surgically isolated mice lumbar stromal cells with RenG2 cells were established and the conditioned media studied by multiplex and ELISA. Consequently, Interleukin-6 (IL-6), Granulocyte colony-stimulating factor (G-CSF) and Activin-A were identified as the paracrine mediators of the intercellular communication process. Aiming to ascertain the individual role of each cytokine in the dedifferentiation process, as well as to access the involvement of exosomes as transport vehicle, the same co-cultures were reproduced in the presence of specific cytokine-communication blockers, either individually or in combinations of up to three blockers, and exosome-mediated communication inhibitors. Finally, exosomes were also collected from control co-cultures and their cargo screened for the target cytokines. ELISA showed that the three cytokines were present inside fibroblasts-secreted exosomes. Moreover, whenever exosomes’ release was blocked, dedifferentiation was abrogated, further proving the role of the aforementioned cytokines and of exosomes in the dedifferentiation process. Additionally, the cytokine-blocking experiments revealed that only IL-6 and Activin-A were endowed with the potential to orchestrate dedifferentiation, as when at least one of these cytokines was present a stem cell population developed inside RenG2 cells. Finally, G-CSF appeared to be decisive in maintaining the undifferentiated phenotype, as a larger pool of CSCs was attained whenever this cytokine and either IL-6 or Activin-A were present. Altogether the attained results implicated IL-6 and Activin-A in the formation of CSCs by dedifferentiation, and G-CSF as a potent keeper of the dedifferentiation status. Subsequent studies are now required to access the use of these cytokines as therapeutic targets so the tumorigenic process may be abrogated in its initial steps, improving patients’ prognosis and survival.
Work sponsored by FEDER, POFC-COMPETE and the FCT grants PTDC/BBB-BQB/2450/2012 and SFRH/BD/33884/2009.
Citation Format: Carlos F. Rodrigues, Eurico Serrano, Marco Cunha, Maria I. Patrício, Mariana Val, João Fonseca, Célia Gomes, Antero Abrunhosa, Artur Paiva, Filomena Botelho, Lina Carvalho, Isabel M. Carreira, Alpoim Carmen. Deconstructing cancer stem cells: IL-6, G-CSF and Activin-A as mediators of stroma-orchestrated epithelial cells’ dedifferentiation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1915. doi:10.1158/1538-7445.AM2017-1915