The Control of Growth, Patterning and Drug Response of the Intestinal Epithelium
The epithelial lining of the human intestine is a prime example of tight homeostatic control of cell proliferation, organization and fate determination. Estimated to have a surface area the size of a tennis court, it continuously receives mechanical, chemical and pathogen-derived insults and is in constant turnover, completely renewing every five days. Amazingly, this active process produces multiple cell types at just the right ratios and locations throughout our life span. Failure of this exquisite control is the basis for diseases including inflammatory bowel disease and cancers of the esophagus, stomach, small and large intestine. To accelerate our ability to study control of cell fate and discover new therapies, we have developed the culture of intestinal stem cells (ISCs) in a high-throughput, quantitative, two-dimensional format. Using this novel “enteroid monolayer” system, we have systematically perturbed intrinsic and extrinsic WNT/BMP signaling to reveal a core morphogenic feedback pathway that controls tissue growth and patterning. Our work demonstrates that the intestinal epithelium, without contributions from the mesenchyme or 3-D crypt geometry, has the intrinsic ability to regulate proliferation and patterning through morphogen-mediated feedback. Additionally we explored Glycogen Synthase Kinase 3 (GSK-3), a protein kinase that is uniquely positioned to act as a signaling by-pass for cancer cells to evade targeted therapies. We found GSK-3 suppression can affect the cellular sensitivities to a broad spectrum of chemotherapies and targeted oncology drugs (e.g., inhibitors of RTKs, mTOR, PLK1). Combined with a kinome-wide RNAi screen, we have shown GSK-3 is a central drug response modulator that affects potency of ~50% of current, clinically relevant kinase-targeted drugs. Our findings suggest small molecule activators of GSK-3 would have potent anti-tumor activity as single agents or in combination therapies.