NCI Program Project in Esophageal Carcinogenesis

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

Project Leader:	Meenhard Herlyn, D.V.M.
Staff Scientist:	Keiran Smalley, Ph.D.
Technician:	Patricia Brafford, M.S.

Esophagus squamous cell carcinomas are often highly invasive and tumor expansion is associated with stimulation of stroma formation. The tumor cells attract fibroblasts by producing growth factors that maintain the normal cells in a continuous state of activation for production of matrix and their own growth factors and cytokines. To better understand the biology of development of squamous cell carcinomas in the esophagus and their progression towards an invasive and aggressive phenotype, we have developed an organotypic culture model that mimics the normal esophagus mucosa and submucosa. In the proposed studies we will overexpress growth factors or disrupt/inactivate receptor function in either esophageal fibroblasts that form the 'submucosa' or keratinocytes that form the 'mucosa' and investigate the biological implications for the dysbalance in growth and differentiation. We will test the hypothesis that continuous activation of keratinocytes through the local overproduction of growth factors by either fibroblasts or keratinocytes can induce a transformed phenotype as defined by uncontrolled growth and reduced differentiation.

Our focus in Specific Aim I will be on the EGF and TGF-ß receptor systems because we hypothesize that these are dominant for maintaining homeostasis in the normal esophageal mucosa. To investigate the roles of growth factors in progression of carcinoma cells towards an aggressive phenotype, we will determine those tumor-derived factors that are produced for paracrine stimulation of the stroma. The activated stromal cells likely provide the malignant cells with a positive feedback through production of yet to be identified stimulatory growth factors. We will then characterize the origins of fibroblasts in the tumor stroma and test the hypothesis that stromal fibroblasts in esophageal carcinomas are derived from two pools, a resident pool and a bone marrow-derived precursor pool in Specific Aim II.

We will determine the extent of recruitment of bone marrow-derived precursor fibroblasts during disease progression and whether they contribute more to aggressive carcinoma growth and invasion than fibroblasts from the resident pool. Tumor-derived growth factors potentially recruit bone marrow-derived fibroblast precursor cells and we will define new markers for fibroblasts at different stages of differentiation. Such markers can be used in future studies as novel targets for diagnosis, prognosis and therapy of esophagus carcinoma. Our work is closely integrated with the other Projects and Core Facilities.