Abstract 5415: Targeted depletion of polo-like kinase 1 alters metabolic regulation in melanoma
Authors: Gutteridge Rosie E. , Singh Chandra K. , Ndiaye Mary A. , Ahmad Nihal 
Published: July 2017

Abstract
Polo-like kinase 1 (PLK1), a critical regulator of mitosis, is shown to be overexpressed in a variety of cancers. PLK1 overexpression has also been linked to poor disease prognosis and a lessened survival in cancer patients. Previously, we have shown that PLK1 is overexpressed in human melanoma and its inhibition causes significant anti-proliferative response in vitro (in multiple melanoma cells) as well as in vivo (in human melanoma xenografts). Further, in another study we demonstrated, based on a large-scale label-free comparative proteomics analysis, that PLK1 inhibition via the small-molecule inhibitor BI 6727 (Volasertib) in human melanoma cells resulted in an alteration of certain metabolism-associated proteins with an associated decrease in cellular metabolism. In this study, to further explore the association between PLK1 and cellular metabolism, we utilized a doxycycline-inducible PLK1 knockdown approach in A375 melanoma cells coupled with a Human Glucose Metabolism PCR array that covers 84 key genes involved in the regulation and enzymatic pathways of glucose and glycogen metabolism. We found that PLK1 knockdown resulted in a significant downregulation of 29 genes and upregulation of 3 genes (more than 2 fold change) associated with cellular metabolism. IDH1, PDP2 and PCK1 were &gt;3-fold downregulated while FBP1 was &gt;7-fold upregulated. Through Ingenuity Pathway Analysis (IPA), we identified glycolysis and the pentose phosphate pathway as major canonical pathways altered by PLK1 inhibition. Further, IPA identified that PLK1 inhibition-modulated genes were largely associated with the proliferation of cells, where FBP1 appeared as a key regulatory player. PCK1 was found to be highly downregulated in our array, and IPA identified it as part of a monosaccharide regulation network. We further validated our data in vivo and found that BI 6727 treatment resulted in a decrease in PCK1 and increase in FBP1 in A375 melanoma cell implanted xenografts. In addition, we observed a strong inverse correlation between PLK1 and FBP1 in multiple melanoma cell lines, with FBP1 expression significantly downregulated in a panel of melanoma cells compared to normal melanocytes. Moreover, BI 6727 treatment resulted in an upregulation in FBP1 in A375, Hs 294T and G361 melanoma cells. Interestingly, in recent studies, FBP1 (fructose-bisphosphatase) that is a rate-limiting enzyme in gluconeogenesis, has been shown to function as a tumor suppressor in certain cancers. Overall, our study support the hypothesis that PLK1 is a regulator of metabolism maintenance that affects the melanoma cell growth.
Citation Format: Rosie E. Gutteridge, Chandra K. Singh, Mary A. Ndiaye, Nihal Ahmad. Targeted depletion of polo-like kinase 1 alters metabolic regulation in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5415. doi:10.1158/1538-7445.AM2017-5415