Abstract PR02: Capturing the integration of Ras-mutant cells into normal epithelial tissue using live imaging

Healthy tissues are frequently subject to oncogenic mutations that result in abnormal cellular behaviors, yet do not always produce malignancy or even macroscopic phenotypes. Specifically, cancer-associated mutations have frequently been identified in phenotypically “normal” skin; however, the mechanism by which the skin epithelium responds to these mutant cells in order to maintain normalcy has been poorly understood. One challenge to understanding this phenomenon has been the inability to follow the same tissue and cells over time in an intact mammal. To overcome this, we have established a novel live-imaging approach to track over time skin epithelial tissue that has been burdened with varying amounts of two distinct activating mutations: Hras G12V and β-Catenin. My previous work has demonstrated that the skin has a robust capacity for coping with and even reversing disruptions to normal tissue architecture produced by either mutational insult (Brown* and Pineda* et al. Nature in press). Intriguingly, our current work, using the hair follicle epithelium as a model system, demonstrates that while β-Catenin driven aberrancies are corrected through the elimination of mutant cells from the tissue, correction of Hras-driven aberrancies does not require mutant cell elimination. Instead, through live imaging and biochemical analysis, we found that the Hras pathway is active over time, resulting in the expansion of mutant cells and enhanced tissue function including more frequent as well as forced hair follicle cycling. While hair cycling is orchestrated by a specialized mesenchyme, called the dermal papilla (DP), these data instead suggest a model whereby the mutant epithelium can influence the nearby wild-type mesenchymal tissue. Preliminary immunofluorescence stains revealed a non-cell autonomous effect by the Hras epithelium on the neighboring mesenchymal cells whereby its molecular and proliferative behaviors are upregulated. Furthermore, mesenchymal laser ablation experiments show that DPs regenerate faster in Hras-mutant follicles compared to wild-type follicles and quickly restore normal hair cycling. We are currently investigating molecular links identified through our proteomic and cytokine analyses that mediate Hras-mutant epithelium communication with its adjacent mesenchyme while maintaining proper hair follicle function. Altogether, these findings indicate an unexpected relationship by which mutant epithelial tissue is able to non-autonomously influence and enhance adjacent mesenchymal behavior in prephenotypic tissue, establishing a tissue crosstalk that appears to buffer mutant cell potential. This abstract is also being presented as Poster A13. Citation Format: Cristiana M. Pineda, Valentina Greco. Capturing the integration of Ras-mutant cells into normal epithelial tissue using live imaging [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr PR02.