NCI Program Project in Esophageal Carcinogenesis

Project 2 - Targeting Cancer Initiating Cells in Esophageal Squamous Cell Carcinoma

Project Leaders:	Meenhard Herlyn, D.V.M.
	Devraj Basu, MD, PhD
	Marcia Brose, MD, PhD
Postdoctoral Fellow:	Kati Rasanen, PhD

Esophagus squamous cell carcinomas (ESCC) are often highly invasive and tumore expansion is associated with stimulation of stroma formation.  The tumor cells attract fibroblasts by producing growth factors that maintain the normal ceslls in a continuous state of activation for production of matrix and their own growth factors and cytokines.  Our long-term objective is to develop new therapies for ESCC that are based upon the unique biological characteristics of this malignancy. Our overarching hypothesis is that tumor cells establish a dominant relationship with stromal cells to control the formation of a primitive ‘organ’, in which all cellular constituents contribute to tumor cell growth, survival and invasion. We then hypothesize that tumor cell resistance to conventional therapies is due to intrinsic and microenvironmental factors. In preliminary studies we have developed three-dimensional culture models (spheroids and organotypic) of the normal esophagus and of ESCC that mimic conditions in vivo. These models allow us to dissect the roles of each cell type in the tumor microenvironment to determine how tumors progress and resist therapeutic drugs. In this renewal application we will develop novel strategies for understanding and treating ESCC that are expected to have a significant impact on the field.  We will pursue the following interrelated Specific Aims:

Our foucs in Specific Aim I will be to define the functional synergy between invading esophageal tumor cells, stromal fibroblasts and in particular, endothelial cells, during neo-angiogenesis.

We will test the hypothesis that tumors represent a finely tuned ‘organ’ but in which the malignant cells dominate to drive activation of fibroblasts for matrix and growth factor production. Activated fibroblasts in turn attract endothelial cell and induce their differentiation for vessel formation and this furnishes positive feedback for the tumor cells. We will analyze the secretion of soluble mediators (e.g. TGFbeta) and the dynamics of cell-cell interactions (mediated by N-cadherin) that together increase the aggressive nature of tumors.

In Specific Aim II we will develop strategies to overcome the intrinsic strong resistance of ESCC cells to therapies. We will test the hypothesis that the unusual resistance to drugs is due to both microenvironmental and intrinsic cues. We will first target cell surface receptors (TGFbetaII receptor) on tumor cells, fibroblasts and/or endothelial cells. In the second strategy, we have identified a proteasome inhibitor, Bortezomib, as active against ESCC, which has served as a platform for a new human phase Ib clinical protocol. We wish to augment the efficacy of Bortezomib in concert with radiation (used in ESCC) and apoptosis agonists. As model systems in both approaches, we will use the following: (1) ESCC grown in spheroids and organotypic cultures in the presence of fibroblasts; (2) ESCC grown in spheroids and organotypic cultures in a matrix of fibroblasts and endothelial cells; and, (3) ESCC xenografts from freshly isolated patients’ tumors.