Characterisation of Primary Cilia (PC) Expression in Oral Cancer Cell Lines with Different Metastatic Potentials 

Sakinah Syed Gulam^1,3, Nazia Abdul Majid¹, Siti Amalina Inche Zainal Abidin^2,3,* 

Abstract

Introduction: Primary cilia (PC), a sensory organelle that exists on the surface of most cells are found in various cancers including prostate, renal, lung, ovarian, and breast cancer. PCs are critical signalling hubs for the maintenance of cell homeostasis through various signalling pathways including Hedgehog, Wnt, Hippo, and ROR2 pathways. Dysregulation of these pathways, therefore, lead to tumorigenesis. While most PC studies focused on cancer related molecular pathway, little is known about intraflagellar-transport 20 (IFT20), a component of IFT machinery that is required for ciliogenesis. Therefore, PC changes and its associated ciliary signalling in oral cancer cells were investigated. Methods: Immortalized normal oral keratinocytes (OKF6- TERT2 cell) and two OSCC cell lines, HSC-2 (non-metastatic OSCC) and HSC-3 (highly metastatic OSCC) cells were cultured in media containing low serum (2%) and high serum (20%) concentrations of foetal bovine serum (FBS). Cells were subjected to serum-starvation for 24, 48, 72 hours and 5 days. For each culture condition, the incidence, length and association of PC with cell proliferation were assessed by fluorescence microscopy. Further, the expression of the ciliogenesis gene, IFT20, was determined by quantitative-RT-PCR. Results: An increase in the percentage of ciliated HSC-2 and HSC-3 cells cultured in low and high serum media was observed compared to OKF6-TERT2 cells. Cilia length was longer in HSC-2 and HSC-3 cells compared to OKF6-TERT2 cells, suggesting cilia length abnormalities in oral cancer cells. The number of ciliated cells was increased, and proliferation was decreased in both HSC-2 and HSC-3 cells cultured in low serum and high serum media at all time points. Furthermore, mRNA transcript levels of IFT20 increased in HSC-2 and HSC-3 cells as compared to OKF6-TERT2 cells. Conclusion: These findings indicate that an increase of PC and the presence of ciliary defects in oral cancer cells is associated with the upregulation of IFT20. 

Keywords: Primary Cilia (PC), Oral Squamous Cell Carcinomas (OSCCs), Oral Cancer, Intraflagellar-transport 20 (IFT20)

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