Compartmentalized microchamber platform for the study of tumor-stroma interactions: A model of paracrine hedgehog signaling in prostate cancer

The cellular microenvironment plays a critical role in cancer development and progression. Paracrine signaling among tumor and stromal cells has been shown to contribute to tumor growth and metastasis. Hedgehog signaling is one example of paracrine- induced tumor growth. Hedgehog ligands secreted by tumor cells activate hedgehog target genes in the mesenchyme - not in the epithelium -- implicating a paracrine mechanism between the tumor and the stroma. Despite the importance of the stroma in tumorigenesis, current technology is not well suited to the study of paracrine signaling. Well-based platforms provide highly convective environments that can sweep soluble signals away from their target, disrupting paracrine signaling interactions. Transwell co-culture systems have long diffusion distances and require large numbers of cells thereby delaying paracrine signaling and limiting the study of tumor stroma interactions to cell lines respectively. Models that provide a controlled and defined culture environment were multiple cell types can interact in close proximity are needed to understand the mechanisms by which paracrine signaling promotes tumorigenesis, and facilitate the pre-clinical evaluation of therapies that effectively target the tumor microenvironment.;Microscale technology can overcome some of these limitations by providing a more controllable diffusion-dominant environment suitable for the study of tumor-stroma signaling. Here, we present data supporting the use of microchannels to study paracrine signaling providing improved sensitivity as well as the ability to move beyond existing co-culture and conditioned medium paradigms. Microscale devices provided a more sensitive environment to study epithelial--stroma interactions as compared to conventional well-based technology. Using a compartmentalized microfluidic platform we developed a prostate cancer model of paracrine Hedgehog signaling and defined the conditions in which Hedgehog activated stroma induces proliferation of prostate tumor cells. The studies presented here establish the first in vitro model to study the tumor promoting mechanisms of paracrine hedgehog signaling and posits the tumor microenviroment as one of the main regulators of Hh driven tumor growth. Our ability to recapitulate in vivo observations of Hh paracrine driven tumor growth demonstrates the utility of microfluidics to better understand in vivo systems and aid in the development of new cancer therapeutics.