THE ROLE OF TGFΒ1 IN ORAL CANCER CELL MIGRATION VIA ACTIVATING SMAD AND NON-SMAD SIGNALLING PATHWAYS

  • Basher Edress M. Shalgm

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Introduction: In general, a malignant tumour formed from the oral mucosal epithelium is referred to as oral cancer. Squamous cell carcinoma has been identified in more than 90% of cases of oral cancer. Transforming growth factor beta (TGFβ) participates in a variety of biological processes, including cellular differentiation, organogenesis and halting the growth of tumours. However, tumour cells use TGFβ signalling systems to their advantage to develop new features, such as the capacity for metastasis and invasion. The term "epithelial to mesenchymal transition" (EMT) describes a biological process in which an epithelial cell undergoes modifications that cause it to have a mesenchymal cell phenotype, such as the capacity to migrate and invade, resist apoptosis, and produce extracellular matrix components.

Aims: This study sought to determine whether TGFβ-1 contributed to the ability of oral cancer cell lines to migrate or not by triggering Smad or non-Smad signalling pathways. Additionally, the investigation included the mechanism of how TGFβ1 controls the migration of oral cancer cell lines via EMT.

Materials: In this project, three cell lines, HaCaT developed from adult human skin keratinocytes, TYS developed from oral adeno-squamous cell carcinoma of the minor salivary gland and SAS-H1 obtained from a poorly differentiated squamous cell carcinoma from human tongue, were utilised. TGFβ-1, epidermal growth factor (EGF), and several signalling pathway inhibitors, including TGFβ- RI Kinase Inhibitor VII, MK-2206, PD98059, and SB431542, were used as test conditions.

Methods: The behaviour and features of the cell lines under test conditions were evaluated using three types of migration assay (the Scatter assay, Gap closure assay and Scratch assay). Western blotting was used to assess the expression of various cell signalling molecules such as Smad, Akt, Erk/MAPK and Rac1/Cdc42. Additionally, to evaluate the expression and localisation of migratory markers including E-cadherin and N-cadherin, immunocytochemistry and western blotting were used.

Results: Both normal and oral cancer cell lines exhibited both individual and collective cell migration triggered by TGFβ-1. Cell adhesion was broken down when TGFβ-1 caused the re-localisation of E-cadherin and β-catenin molecules from the cell membrane to the cytoplasm. N-cadherin, a mesenchymal marker, was increased by TGFβ-1 in both normal and oral cancer cell lines.

Conclusion: TGFβ1 induces migration of oral cancer cell lines via EMT. TGFβ1 regulates cell migration by Smad, PI3K/Akt and Erk/MAPK signalling pathways in normal and oral cancer cell lines.
Date of Award2023
Original languageEnglish
SponsorsUniversity of Sebha
SupervisorSarah Jones (Supervisor), Ian Ellis (Supervisor) & Michaelina Macluskey (Supervisor)

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