ESPE Abstracts

We have explored the role of local epithelial GHR signaling in regulating the tissue microenvironment. Despite declining circulating pituitary GH with age, colon epithelial DNA damage and aging trigger local non-pituitary growth hormone (npGH) expression. We showed that accumulated DNA damage, a driving force for age-related pathologies including neoplasia, may result from local npGH- mediated defective DNA damage repair (DDR) and build-up of unrepaired DNA damage resulting in chromosomal instability in aged 3-dimensional iPSC-derived human intestinal organoids. In the aged human colon, local npGH, a SASP component, enables paracrine epithelial GHR signalling to induce local DNA damage as evidenced by showing that local npGH emanating from lentiG-infected organoids co-cultured with intact organoids induces neighboring organoid chromosomal instability, with somatic mutations including deletions, breakends and duplications. These adverse sequelae are engendered by npGH-mediated suppressed DNA damage repair proteins leading to DNA damage accumulation. We identified WIP1 as a key phosphatase mediating npGH suppression of DNA repair, and is a specific target for GH action. GH-induced Wip1 dephosphorylates ATM, attenuating DNA damage repair proteins in human 3-dimensional intestinal organoids, dephosphorylating CHK2, γH2AX, and p53. Mice bearing GH-secreting tumors show high Wip1 expression with attenuated DNA repair as well as increased DNA damage. GH induction of Wip1 is GHR/STAT5-mediated concordant with decreased colon Wip1 expression observed in GHR-/- mice. Furthermore, Wip1 inhibition reverses GH-induced DNA damage by restoring ATM phosphorylation thereby preventing accumulated epithelial unrepaired DNA. Wip1 is induced in buffy coats derived from patients with GH-secreting adenoma vs patients with non-functioning pituitary adenomas. npGH also triggers EMT as evidenced by suppressed E-cadherin and induced Twist2 and Snai1, increasing cell motility and favoring cell transformation. Hypersomatotrophic mice exhibit increased colon DNA damage, and EMT. Enriched gene ontologyand KEGG pathway analysis of intact organoids exposed to paracrine npGH shows distorted extracellular matrix gene expression and focal adhesion pathways. Disrupted GHR signaling in fibroblasts derived from mutant GHR patients, as well as in GHR-/- mice colon, induced p53, with less DNA damage. Similarly, murine injection of a selective GHR synthesis inhibitor, activates DDR with subsequent decreased colon DNA damage. By contrast, acromegaly patients receiving pegvisomant show induced colon p53 and p21 abundance, conferring protection from epithelial DNA damage. Conclusions: WIP1 induced by GHR signaling is a key molecule suppressing DNA damage repair and mediated by GH in human tissues. Thus, paracrine npGH enables a microenvironmental landscape favoring epithelial cell transformation.