Abstract 3027: Stromal cells-derived paracrine factors promote dedifferentiation of human lung carcinoma cells into cancer stem cells
Authors: Rodrigues Carlos F D , Rodrigues Inês P. , Val Mariana , Carvalho Lina , Paiva Artur , Zhitkovich Anatoly , Carreira Isabel M. , Alpoim Mª Carmen 
Published: May 2015

Tumors are dynamic entities that act like organs in a perfect trading with the entire body. Through the employment of deceiving cellular and molecular strategies, they use the corporal machinery for the promotion of their survival and dissemination. 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. As heterogeneous entities, tumors are comprised of distinct cell populations. Cancer stem cells (CSCs) are a subset of notably chemo- and radiotherapy resistant malignant tumor cells with the capacity to drive tumorigenesis and metastases formation and eventually tumor relapse.

Lung cancer is a leading cause of death worldwide and its prevalence is increasing mostly due to sustained smoking habits and the accumulation of atmosphere pollutants. In this work hexavalent chromium [Cr(VI)] was the carcinogenic agent used considering its increasing occupational relevance. The non-malignant human bronchial epithelial airway system 2B (BEAS-2B) was malignantly transformed into the RenG2 cell line using low density culture in the presence of Cr(VI). A parallel control cellular system (Cont1) was produced under the same conditions, though, in the absence of Cr(VI). Two additional derivative cell lines, DRenG2 and DDRenG2, were attained following serial rounds of injections in immunocompromised mice. A panoply of techniques was used to characterize the attained cellular systems leading to the hypothesis of CSCs involvement in Cr(VI)-driven BEAS-2B malignant transformation. The sphere-formation assay readily confirmed our hypothesis as CSCs spheres were isolated only from the derivative cell lines (SC-DRenG2 and SC-DDRenG2 cells, respectively). Tumorigenic and RT-qPCR studies further supported the stem potential of the attained systems, suggesting that a dedifferentiation process featured its emergence during RenG2 derivation in nude mice. Using an elegant cell culture model that encompassed the prolonged co-culture of surgically isolated mice lumbar stromal cells with the RenG2 cells, we proved that RenG2 cells’ dedifferentiation was driven by paracrine factors released by the mouse fibroblasts, as they lost the RenG2's molecular signature and acquired a new one more close to that of both DRenG2 and SC-DRenG2. Finally, the key cytokines released by the stromal fibroblasts were identified in the conditioned media of such cultures.

CSCs formation boosted the malignant potential of our carcinoma cell population, providing them with increased resistance to therapeutic drugs. Also, the dedifferentiation process revealed to be essentially chemical and specie-unspecific, as human cells were able to dedifferentiate in response to mice cells-released cytokines.

Work sponsored by FEDER, POFC-COMPETE and the FCT grants PTDC/BBB-BQB/2450/2012 and SFRH/BD/33884/2009.

Citation Format: Carlos F D Rodrigues, Inês P. Rodrigues, Mariana Val, Lina Carvalho, Artur Paiva, Anatoly Zhitkovich, Isabel M. Carreira, Mª Carmen Alpoim. Stromal cells-derived paracrine factors promote dedifferentiation of human lung carcinoma cells into cancer stem cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3027. doi:10.1158/1538-7445.AM2014-3027