| Summary: | 碩士 === 國立中山大學 === 生物科學系研究所 === 97 === Proopiomelanocortin (POMC) is a 241 amino acids precursor protein, which encodes various neuropeptides including corticotropin (ACTH), a-melanocyte-stimulating hormone (a-MSH), and b-endorphin (b-EP). POMC plays an important role in stress response, metabolism, energy homeostasis and anti-inflammation. Recent studies demonstrated that systemic POMC gene delivery potently suppresses the tumor growth and metastasis of B16-F10 melanoma in vitro and in vivo via inhibition of NF-κB/COX2 pathway. However, systemic POMC expression also led to elevated urine excretion and water intake in mice. This was attributed to enhanced steroidgenesis as evidence by elevated plasma corticosteroids levels in animals and increased cortisol production in adrenal H295R cells after POMC gene delivery. Since corticosteroids are also potent anti-inflammatory agents, it remains unclear whether the ACTH-mediated cortisol synthesis also contributed to the POMC-induced tumor suppression. To address this issue, we generated a series of adenovirus vectors encoding POMC genes with mutation or deletion in ACTH domain including ACTH (K15A/R17A). Unlike the wild type POMC, gene delivery of ACTH (K15A/R17A) resulted in significantly lower cortisol production, CYP11B1 mRNA level, and glucocorticoid responsive element (GRE)-driven luciferase activities in H295R cells. ACTH (K15A/R17A) gene delivery did not affect the urination and water intake in mice. Above all, ACTH (K15A/R17A) gene delivery remained capable of inhibiting the colonies formation and invasiveness of B16-F10 melanoma cells. In summary, steroidgenesis is not essential to POMC-mediated melanoma suppression. In addition, ACTH (K15A/R17A) gene delivery may provide a better alternative for melanoma control.
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