Abstract 300: Mechanisms of growth hormone action in the aging tissue microenvironment
Authors: Chesnokova Vera , Zonis Svetlana , Apaydin Tugce , Wang Christian , Barrett Robert , Melmed Shlomo 
Published: April 2023

The aging tissue microenvironment undergoes progressive changes enabling age-related pathologies. Senescent cells increase with age, and the secretome released from senescence cells (SASP) affects neighboring cells, often promoting proliferation, tissue inflammation, angiogenesis, and, depending on tissue type, creating a milieu favoring neoplasia. We showed that local non-pituitary growth hormone (GH) accumulates with age in human colon tissue, is induced in response to DNA damage, and suppresses DNA repair. We now show that GH is a SASP component. To examine SASP-derived GH actions on the tissue microenvironment, we co-cultured intact human 3D intestinal organoids with organoids infected with lentivirus expressing either hGH (lentiGH) or vector (lentiV) for 5 weeks. Using whole-exome sequencing to evaluate somatic mutations and somatic copy number alterations, we found that local paracrine GH emanating from lentiGH organoids increases chromosomal instability in intact organoid cells, inducing somatic mutations including deletions, breakends, duplications, and insertions, as compared to organoids co-cultured with lentiV organoids. Mechanisms for chromosomal instability observed in these organoids likely occur as a consequence of GH-induced suppression of DNA damage repair proteins including pATM, pATR, and pBRCA2, leading to DNA damage accumulation, and, in the long run, favoring cell transformation. KEGG pathway analysis of intact organoids subjected to paracrine GH exposure identified changes in focal adhesion pathways (p=0.0016), consistent with observed increased migration, invasion, and anchorage-independent growth of normal human colon cells (hNCC) exposed to GH. Furthermore, IPA analysis revealed EMT pathway changes (p=0.0018),,also confirmed by showing increased EMT transcription factors Twist2 and Snai1 expression.Although senescence has been defined as irreversible proliferative arrest, recent studies now show that senescence can be reversed. Treating hNCC with etoposide to induce senescence and culturing senescent cells in the presence of GH for 10 days resulted in p53 suppression, enabling cells to re-enter the cell cycle, as evidenced by induced Ki67, a marker of proliferation. These post-senescent cells also acquired the stem cell marker SOX2 and exhibited increased Twist2, consistent with anchorage-independent growth and increased migration as compared to senescence cells not treated with GH. These results identify local paracrine GH as an important determinant of the local tissue microenvironment promoting age-associated changes consistent with a pro-neoplastic milieu.

Citation Format: Vera Chesnokova, Svetlana Zonis, Tugce Apaydin, Christian Wang, Robert Barrett, Shlomo Melmed. Mechanisms of growth hormone action in the aging tissue microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 300.