Targeting zebrafish and murine pituitary corticotroph tumors with a cyclin-dependent kinase (CDK) inhibitor

1. Ning-Ai Liu^a,
2. Hong Jiang^a,
3. Anat Ben-Shlomo^a,
4. Kolja Wawrowsky^a,
5. Xue-Mo Fan^b,
6. Shuo Lin^c, and
7. Shlomo Melmed^a,¹

+ Author Affiliations

1. Departments of ^aMedicine and
2. ^bPathology, Pituitary Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048; and
3. ^cDepartment of Molecular, Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA 90024

1. Edited by Wylie W. Vale, The Salk Institute for Biological Studies, La Jolla, CA, and approved April 7, 2011 (received for review December 3, 2010)

Abstract

Cushing disease caused by adrenocorticotropin (ACTH)-secreting pituitary adenomas leads to hypercortisolemia predisposing to diabetes, hypertension, osteoporosis, central obesity, cardiovascular morbidity, and increased mortality. There is no effective pituitary targeted pharmacotherapy for Cushing disease. Here, we generated germline transgenic zebrafish with overexpression of pituitary tumor transforming gene (PTTG/securin) targeted to the adenohypophyseal proopiomelanocortin (POMC) lineage, which recapitulated early features pathognomonic of corticotroph adenomas, including corticotroph expansion and partial glucocorticoid resistance. Adult Tg:Pomc-Pttg fish develop neoplastic coticotrophs and pituitary cyclin E up-regulation, as well as metabolic disturbances mimicking hypercortisolism caused by Cushing disease. Early development of corticotroph pathologies in Tg:Pomc-Pttg embryos facilitated drug testing in vivo. We identified a pharmacologic CDK2/cyclin E inhibitor, R-roscovitine (seliciclib; CYC202), which specifically reversed corticotroph expansion in live Tg:Pomc-Pttg embryos. We further validated that orally administered R-roscovitine suppresses ACTH and corticosterone levels, and also restrained tumor growth in a mouse model of ACTH-secreting pituitary adenomas. Molecular analyses in vitro and in vivo showed that R-roscovitine suppresses ACTH expression, induces corticotroph tumor cell senescence and cell cycle exit by up-regulating p27, p21 and p57, and downregulates cyclin E expression. The results suggest that use of selective CDK inhibitors could effectively target corticotroph tumor growth and hormone secretion.

• pituitary cell cycle
• pituitary hormone
• adrenal function

Footnotes

• ↵¹To whom correspondence should be addressed. E-mail: melmed@csmc.edu.

• Author contributions: N.-A.L., S.L., and S.M. designed research; N.-A.L., H.J., and K.W. performed research; N.-A.L., A.B.-S., X.-M.F., S.L., and S.M. analyzed data; S.L. contributed new reagents/analytic tools; and N.-A.L. and S.M. wrote the paper.

• The authors declare no conflict of interest.

• This article is a PNAS Direct Submission.

• *Fukuoka H, et al. 92nd Annual Meeting of the Endocrine Society, June 19–22, 2010, San Diego, CA.

• This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1018091108/-/DCSupplemental.

Freely available online through the PNAS open access option.

From http://www.pnas.org/content/early/2011/04/26/1018091108.abstract