Abstract 2370: Tumor-associated stromal cells increase malignancy of human colorectal cancers triggering the induction of Epithelial-to-mesenchymal transition
Authors: Mele Valentina , Muraro Manuele Giuseppe , Droeser Raoul , Oertli Daniel , Zuber Markus , Rosso Raffaele , Martin Ivan , Heberer Michael , Spagnoli Giulio C. , Iezzi Giandomenica 
Published: August 2015

During tumor formation, normal tissue microenvironment is transformed in an “altered” niche, composed of non-malignant supporting cells, which influence the homeostasis of cancer cells via paracrine regulators. Tumor-associated stromal cells (TASC) are the prominent stromal elements in most types of human carcinomas including colorectal cancer (CRC). The differentiation of TASC from other cell types, such as resident stromal cells or bone marrow-derived mesenchymal stem cells (BM-MSC) is mainly mediated by factors produced during the crosstalk with malignant cells. TASC produce various extracellular matrix proteins, chemokines, and other tumor-promoting factors which affect vascularization, proliferation, tumor cell invasiveness and survival. Emerging data suggests that they also play a critical role in determining response to therapy. For instance TASC-derived factors may contribute to the development of a protective milieu by influencing cell-cell/cell-matrix interactions, cancer cell survival, and suppression of anti-tumor immune responses. Moreover, physical contact between TASC and malignant cells supports tumor cell survival via activation of anti-apoptotic pathways or inducing epithelial-to-mesenchymal transition (EMT). We previously showed that BM-MSC are capable of triggering EMT in CRC cells, leading to increased tumor cell aggressiveness in vitro and in vivo. However, the role played by the stromal component and the processes induced on CRC cells remain to be fully elucidated. For this purpose we have addressed phenotypic and functional characterization of TASC in vitro and we have analyzed TASC-mediated effects on CRC development and progression in vivo.

TASC were characterized for phenotype and differentiation capacity. Human CRC cells were cultured in the presence or absence of TASC for five days. After co-culture tumor cells were sorted by flow cytometry and evaluated for the expression of EMT-related genes by Real Time PCR and for in vitro invasiveness by chemoinvasion assay. Furthermore, their tumorigenicity was assessed upon injection in NOD/SCID mice and developing tumors were analyzed.

Our results indicate that TASC resemble BM-MSC in morphology and phenotype. They comprise a multipotent subpopulation that is able to differentiate into adipogenic and osteogenic lineage. After co-culture with CRC cells they express membrane-bound TGF-β, through which they are capable to initiate EMT in tumor cells. Moreover CRC cells acquire a more invasive phenotype after co-culture with TASC. Upon subcutaneous injection in NOD/SCID mice, tumor cells co-cultured with TASC show a significantly faster growth kinetic and develop significantly larger tumor masses as compared to tumor cells alone.

Thus our data show that the stromal component of CRC increases the tumor cells malignancy triggering EMT induction.

Citation Format: Valentina Mele, Manuele Giuseppe Muraro, Raoul Droeser, Daniel Oertli, Markus Zuber, Raffaele Rosso, Ivan Martin, Michael Heberer, Giulio C. Spagnoli, Giandomenica Iezzi. Tumor-associated stromal cells increase malignancy of human colorectal cancers triggering the induction of Epithelial-to-mesenchymal transition. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2370. doi:10.1158/1538-7445.AM2015-2370