Abstract 169: Maintenance of breast cancer stem cells in an inert matrix is mediated by mesenchymal stem cells in the tumor stroma

Abstract

Abstract Introduction: Cancer stem cells (CSCs) hypothesis relates cancer recurrence to a small population of tumor cells with the ability to self-renew to maintain the tumor mass. Recent studies demonstrate that conventional therapies eliminate the differentiated cells that form bulk of the tumor, while leaving CSCs unharmed. There is increasing evidence that the maintenance of CSCs in the tumor tissue is regulated by microenvironment. In particular, human mesenchymal stem cells (hMSCs) and associated soluble factors as part of the tumor stroma play a significant role in self-renewal and maintenance of CSCs (1). Our laboratory has developed an inert 3D synthetic matrix with defined properties that maintains and enriches the CSC sub-population of tumor cells within a certain range of stiffness (2). The objective of this work was to investigate the effect of co-encapsulation of MDA-MB-231 (MDA) human breast cancer cells with human hMSCs in the engineered patterned matrix on tumorsphere formation and CSC maintenance. Methods: Thee effect of MSCs on MDA cells was investigated in a patterned matrix with defined stiffness to control tumorsphere size. To separate the patterned cellular matrix from the glass substrate, a layer of the gel without cells was first crosslinked on the glass substrate by UV radiation. Next, a mixture of MDA and hMSCs (5x105 cells/mL each) in the hydrogel precursor solution was patterned by UV radiation on the gel covered glass slide with a UV mask. The stiffness of the matrix was controlled by the concentration of macromer in the hydrogel precursor solution. Tumorsphere size and density, and expression of CSC markers were determined with incubation time in tumor CSC culture medium. Results and Conclusion: The micro-patterned 3D synthetic hydrogel matrix with defined modulus supported tumorsphere formation and expression of CSC markers. Specifically, co-culture of MDA cells with hMSCs increased the expression of CD44 and ABCG2 markers of stemness by three-fold after 6 days of encapsulation in the engineered matrix from 25 to 58 for CD44 and 14 to 42 for ABCG2. Likewise, tumorsphere density more than doubled and average tumorsphere diameter increased from 25 to 47 µm after 6 days of incubation when MDA cells were co-encapsulated with hMSCs. The model inert matrix can be used to understand the effect of individual cell types in the tumor stroma on CSC maintenance and tumorigenesis. Citation Format: Samaneh K. Sarvestani, Danial Barati, Esmaiel Jabbari. Maintenance of breast cancer stem cells in an inert matrix is mediated by mesenchymal stem cells in the tumor stroma. [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 169. doi:10.1158/1538-7445.AM2014-169