DNA damage and growth hormone hypersecretion in pituitary somatotroph adenomas
Anat Ben-Shlomo, … , Artak Labadzhyan, Shlomo Melmed
Anat Ben-Shlomo, … , Artak Labadzhyan, Shlomo Melmed
Published July 16, 2020
Citation Information: J Clin Invest. 2020;130(11):5738-5755. https://doi.org/10.1172/JCI138540.
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Research Article Endocrinology

DNA damage and growth hormone hypersecretion in pituitary somatotroph adenomas

Abstract

Drivers of sporadic benign pituitary adenoma growth are largely unknown. Whole-exome sequencing of 159 prospectively resected pituitary adenomas showed that somatic copy number alteration (SCNA) rather than mutation is a hallmark of hormone-secreting adenomas and that SCNAs correlate with adenoma phenotype. Using single-gene SCNA pathway analysis, we observed that both cAMP and Fanconi anemia DNA damage repair pathways were affected by SCNAs in growth hormone–secreting (GH-secreting) somatotroph adenomas. As somatotroph differentiation and GH secretion are dependent on cAMP activation and we previously showed DNA damage, aneuploidy, and senescence in somatotroph adenomas, we studied links between cAMP signaling and DNA damage. Stimulation of cAMP in C57BL/6 mouse primary pituitary cultures using forskolin or a long-acting GH-releasing hormone (GHRH) analog increased GH production and DNA damage measured by H2AX phosphorylation and a comet assay. Octreotide, a somatostatin receptor ligand that targets somatotroph adenoma GH secretion in patients with acromegaly, inhibited cAMP and GH and reversed DNA damage induction. In vivo long-acting GHRH treatment also induced pituitary DNA damage in mice. We conclude that cAMP, which induces somatotroph proliferation and GH secretion, may concomitantly induce DNA damage, potentially linking hormone hypersecretion to SCNA and genome instability. These results elucidating somatotroph adenoma pathophysiology identify pathways for targeted treatment.

Authors

Anat Ben-Shlomo, Nan Deng, Evelyn Ding, Masaaki Yamamoto, Adam Mamelak, Vera Chesnokova, Artak Labadzhyan, Shlomo Melmed

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Figure 9

CJC-1295 treatment in vivo.

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CJC-1295 treatment in vivo. Four-month-old male C57BL/6 mice were inject...
Four-month-old male C57BL/6 mice were injected s.c. with PBS (n = 15) or 10 μg/kg CJC-1295 (n = 16) 3 times per week for 8 weeks. (A) Pituitary weight (mg) in PBS-treated mice (n = 9) and CJC-1295–treated mice (n = 10). (B) Serum IGF1 levels (pg/mL) in PBS-treated mice (n = 15) and CJC-1295–treated mice (n = 16). Results are presented as the mean ± SEM. *P ≤ 0.05 and ***P ≤ 0.001 versus PBS, by 2-tailed, unpaired t test with Bonferroni’s correction. (C) Comet assay and tail appearance in representative mice. Images on the left are of PBS-treated mice (mice 3, 4, and 14); images on the right are of CJC-1295–treated mice (mice 21, 28, and 31). One image from each mouse is presented. Cells from each mouse pituitary gland were plated on 3 slides, and 61–89 images were taken for each mouse (original magnification, ×20), depending on the number of cells visualized. (D) Comet assay results depicting Olive tail moment for the 6 mice presented in C. The number of cells analyzed by a blinded observer is indicated. Results are presented as the mean ± SEM (mouse 3, 8.3 ± 0.9; mouse 4, 8.8 ± 0.7; mouse 14, 10.5 ± 0.8; mouse 21, 39.3 ± 1.5; mouse 28, 32.9 ± 1.5; mouse 31, 24.4 ± 1.2). ###P ≤ 0.001 for each CJC-1295–treated mouse versus each PBS-treated mouse, by 1-way ANOVA. (E) Quantitative analysis of γH2AX change normalized to total H2AX in PBS-treated mice (n = 5/7) versus CJC-1295–treated mice (n = 8/8), as presented in Supplemental Figure 11. Two mice were excluded from the PBS-treated group, as described in Results. Band intensities were calculated with ImageJ. Results are presented as the mean ± SEM. *P ≤ 0.05 versus PBS, by 2-tailed, unpaired t test with Bonferroni’s correction. The experiment was performed twice.