Abstract 1169: A potential tumor suppressive role of polo-like kinase 5 in specific neoplasms

Abstract

Abstract Polo-like kinase 5 (PLK5) is a member of the serine/threonine family of polo-like kinases (PLKs) which have been shown to play important role in cell cycle regulation. The Plk5 gene was identified to encode an expressed protein in humans over a decade ago; however, limited information is available regarding the functional significance of PLK5. A search of the ProteinAtlas database showed that PLK5 was expressed in several types of normal human tissues including the brain, eye, lung, testis, fallopian tubes, endometrium, and cervix. However, research regarding the role of PLK5 in cancer is still in its infancy, with little available information regarding its functional significance in human biology. Interestingly, one published study has demonstrated that PLK5 was downregulated in brain tumors, suggesting a potential tumor suppressive function in this neoplasm. The objective of this study was to determine the expression profile of PLK5 in a variety of normal and malignant tissues types to gain an insight into its function in cancer. We performed quantitative immunostaining of PLK5 employing tissue microarrays (TMAs) containing tissue cores from six different organs viz. cervix, endometrium, fallopian tubes, ovary, lung, and testis. Following immunohistochemical staining, the TMA slides were scanned via Vectra Imaging System and analyzed using the Inform software, yielding quantitative information of PLK5 protein levels in each tissue core, which was then subjected to further statistical analysis. Our data demonstrated that PLK5 protein levels were significantly downregulated in most malignant tissues when compared to normal tissues (p<0.03). Further, we determined the expression profiles of PLK5 in cancer and normal tissues from the organs of interest using publicly available TCGA (The Cancer Genome Atlas) data via the Genomic Data Commons (GDC) Data Portal. Using this data source, we were able to compare PLK5 levels in tumor versus normal tissues from cervix, endometrium, and ovary. We found that PLK5 had significantly lower expression in cancer than normal in all three tissue types (p<0.003). Additionally, we used the Genotype-Tissue Expression (GTEx) portal, which contains data from non-diseased tissues, to compare the PLK5 expression in normal samples from GTEx to the tumor samples from TCGA. We found that the PLK5 levels were higher in normal versus the malignant tissues from cervix, endometrium, ovary, and testis; however, there was no difference in terms of PLK5 levels between the normal and malignant tissues from lung. Taken together, our results demonstrate that PLK5 levels are downregulated in multiple cancers, suggesting a potential tumor suppressive function of PLK5 in the tissue types studied. However, additional detailed studies are required to fully understand the role and functional significance of PLK5 in cancer. Citation Format: Glorimar Guzmán-Pérez, Shengqin Su, Mary A. Ndiaye, Manish Patankar, Nihal Ahmad. A potential tumor suppressive role of polo-like kinase 5 in specific neoplasms [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1169.