Funding opportunities

EXECUTIVE SUMMARY The overall goal of this effort is to derive both normal and neoplastic intestinal stem cells (ISCs) from human pluripotent stem cells (hPSCs) using a novel, in vitro niche that is meant to reflect the cellular intestinal microenvironment. To achieve these ends, applicant proposes two aims. First, ISCs will be derived from embryonic stem cells (hESCs) and human adipose-derived induced pluripotent stem cells (hiPSCs) using rational reprogramming methods within an explant culture system. In Aim 2, a series of molecular manipulations will be performed in an effort to derive and subsequently characterize intestinal cancer stem cells (CSCs). The reviewers agreed that this proposal addresses a major unsolved problem and if successful, could have a significant impact on the field of regenerative medicine. The combination of an innovative explant culture approach with a strong mechanistic focus was thought to comprise an important first step towards achieving the numbers and types of cells that would be necessary for clinical breakthroughs. While they strongly acknowledged the creativity and compelling rationale, reviewers were somewhat less enthusiastic about the objectives of Aim 2. While some appreciated its novelty, most felt that the information generated from these studies would only incrementally advance our understanding of the processes that lead to oncogenesis. Despite a logical, well written and carefully designed research plan, the reviewers identified a number of issues that were thought to undermine the feasibility of this effort. Importantly, the preliminary finding that hESCs differentiate into non-intestinal epithelium within the explant environment raised questions about the authenticity of this model as an embryonic niche. One reviewer suggested that the explants might in fact be akin to a later or adult stage of development, thereby calling into question whether the appropriate signals would be in place to direct the intestinal differentiation of hPSCs. Beyond this fundamental uncertainty, some reviewers noted that certain necessary cell lines had not yet been produced, cloned or validated. It was not clear that if these strategies should fail whether the back up methods would result in equivalently useful reagents. Another reviewer commented that while the applicant had discussed potential pitfalls and alternative strategies, not all of these appeared realistic given the time-line of the primary approaches. While these weaknesses were significant, the reviewers were compelled to acknowledge the strengths represented by the applicant’s unique experience with the explant system as well as access to a valuable and useful antibody reagent. Reviewers lauded the achievements of the principal investigator (PI) as a highly acclaimed clinician scientist with an outstanding and productive track record. His/her accomplishments were fundamental in establishing the unique model that forms the basis of this investigation. The collaborators and research environment were also considered to be excellent. In summary, this proposal studies the derivation of ISCs from human pluripotent stem cells. Though the reviewers valued the PI’s expertise, productivity, and novel in vitro culture system, their enthusiasm diminished substantially over concerns about impact and feasibility.