The Overall Goal of this application is to identify shared, conserved mechanisms that induce precancerous lesions like metaplasia. Our preliminary and published data indicate that pseudopyloric or so- called SPEM-type metaplasia in stomach is the manifestation of a conserved regeneration program induced by large-scale injury. The metaplastic cells themselves are characterized by a ?dedifferentiated? phenotype wherein they express embryonic-like or early developmental markers that proliferate to repair the tissue damage. We hypothesize that the metaplastic/regenerative process is fueled by expansion of a population of embryonic-like progenitor cells (EPCs). EPCs arise in large part from mature secretory that become progenitor-like by following a stepwise, conserved cellular program we call ?paligenosis?. Here, we will show preliminary data that Hippo signaling via Nf2 (Merlin) and downstream transcription factors YAP1/TAZ may be a critical, conserved modulator of EPC expansion.
In Aim 1, we will test necessity/sufficiency of Nf2 and Yap1/Taz in gastric metaplasia in mouse models and in human and mouse organoids. We will perform discovery based RNA-Seq experiments to uncover new Hippo targets modulating EPCs and metaplasia.
In Aim 2 we will look at how these Hippo pathway components interact with the stages of paligenosis we have characterized, whether they can overcome molecular checkpoints between Stages 1 and 2 and between 2 and 3. We will also determine how Hippo signaling interacts with the conserved, paligenosis-dedicated gene Ifrd1, which we will show is required to suppress p53 as cells upregulate mTORC1 to reenter the cell cycle in Stage 3 paligenosis.
In Aim 3, we will test whether increasing EPC formation and metaplasia via the Hippo pathway increases tumorigenesis by combining Hippo mutants with: 1) the mutagen MNU; or 2) additional gastric-cancer- related mutant alleles p53 and Cdh1; or 3) by increasing chronic inflammation with the human gastric-cancer- predisposing bacterium H pylori. Experiments were designed to be appropriately powered in collaboration with our biostatistician, Dr. Yan Yan. State-of-the-art imaging (eg. AiryScan live-cell, confocal on organoids; FIB-SEM 3-D ultrastructural nanotomography) will be performed with Dr. James Fitzpatrick in our institutional imaging core; organoid support, and gene editing will be in collaboration with Dr. Blair Madison and our shared organoid core; bioinformatic analysis including synergy with data repositories will be via our collaboration with Dr. Bo Zhang, who directs the institutional bioinformatics core for the Center for Regenerative Medicine.
The proposed experiments will examine how precancerous lesions form. We hypothesize that this process is conserved across organs and species and that there are fundamental genetic and cellular mechanisms that we can identify underlying how these lesions develop. We will test: the Hippo pathway in relation to other key genes regulating precancerous lesions like: IFRD1, p53, CDH1.
