Cyclin E - mediated human proopiomelanocortin regulation as a therapeutic target for Cushing disease

Liu, N.A., Araki, T., Cuevas-Ramos, D., Hong, J., Ben-Shlomo, A., Tone, Y., Tone, M., Melmed, S.
The Journal of clinical endocrinology and metabolism   100(7): 2557-64 (Journal)
Registered Authors
Liu, Ningai, Melmed, Shlomo
MeSH Terms
  • ACTH-Secreting Pituitary Adenoma/complications
  • ACTH-Secreting Pituitary Adenoma/drug therapy
  • ACTH-Secreting Pituitary Adenoma/genetics
  • ACTH-Secreting Pituitary Adenoma/pathology
  • Adenoma/complications
  • Adenoma/drug therapy
  • Adenoma/genetics
  • Adenoma/pathology
  • Adolescent
  • Adult
  • Aged
  • Antineoplastic Agents/therapeutic use*
  • Cyclin E/antagonists & inhibitors*
  • Cyclin E/physiology
  • Female
  • Gene Expression Regulation, Neoplastic/drug effects
  • Humans
  • Male
  • Molecular Targeted Therapy/methods*
  • Pituitary ACTH Hypersecretion/drug therapy*
  • Pituitary ACTH Hypersecretion/pathology
  • Primary Cell Culture
  • Pro-Opiomelanocortin/genetics*
  • Pro-Opiomelanocortin/metabolism
  • Purines/therapeutic use*
  • Tumor Cells, Cultured
  • Young Adult
25942479 Full text @ J. Clin. Endocrinol. Metab.
Cushing disease (CD), due to pituitary corticotroph tumor ACTH hypersecretion, drives excess adrenal cortisol production with adverse morbidity and mortality. Loss of glucocorticoid negative feedback on the hypothalamic-pituitary-adrenal (HPA) axis leads to autonomous transcription of the corticotroph precursor hormone proopiomelanocortin (POMC), consequent ACTH over-production and adrenal hypercortisolism. We previously reported that R-roscovitine (CYC202, seliciclib), a 2,6,9-trisubstituted purine analogue, suppresses CDK2/cyclin E, and inhibits ACTH in mice and zebrafish. We hypothesized that intra-pituitary cyclin E signaling regulates corticotroph tumor POMC transcription independently of cell cycle progression. The aim was to investigate whether R-roscovitine inhibits human ACTH in corticotroph tumors by targeting the CDK2/cyclin E signaling pathway.
Primary cell cultures of surgically resected human corticotroph tumors were treated with or without R-roscovitine, ACTH measured by RIA and quantitative PCR and/or Western blot analysis performed to investigate ACTH and lineage specific transcription factors. Cyclin E and E2F1 siRNA transfection was performed in murine corticotroph tumor AtT20 cells to elucidate mechanisms for drug action. POMC gene promoter activity in response to R-roscovitine treatment was analyzed using luciferase reporter and chromatin immunoprecipitation assays.
R-roscovitine inhibits human corticotroph tumor POMC and Tpit/Tbx19 transcription with decreased ACTH expression. Cyclin E and E2F1 exhibit reciprocal positive regulation in corticotroph tumors. R-roscovitine disrupts E2F1 binding to the POMC gene promoter, suppresses Tpit/Tbx19 and other lineage-specific POMC transcription co-factors via E2F1 dependent and independent pathways.
R-roscovitine inhibits human pituitary corticotroph tumor ACTH by targeting the cyclinE/E2F1 pathway. Pituitary cyclin E/E2F1 signaling is a previously unappreciated molecular mechanism underlying neuroendocrine regulation of the HPA axis, providing a sub-cellular therapeutic target for small molecule CDK inhibitors of pituitary ACTH-dependent hypercortisolism, i.e. Cushing disease.
Genes / Markers
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Engineered Foreign Genes