Johanna Farley - Institutionen för experimentell medicinsk vetenskap

Title: The role of Syndecan-1 and calcium in epithelial to mesenchymal transition and breast cancer metastasis.

Main supervisor: Sandeep Gopal

Reviewers: Sofie Mohlin & Nicholas Leigh

Abstract

Background

Metastatic cancer is incurable and accounts for most cancer-related deaths. Deciphering the mechanisms that enable metastasis can lead to the identification of targeted preventative therapies. Epithelial-to-mesenchymal transition (EMT) is a hallmark event in the early metastasis of primary breast tumours. In breast cancer, altered expression of syndecan-1, a transmembrane proteoglycan, has significant associations with poor prognosis, disease progression and invasiveness. Building on our findings from a C. elegans model, we hypothesise that syndecan-1 controls mammalian transcriptomic signaling during EMT via the regulation of intracellular calcium.

Research questions

This project investigates how syndecan-1 controls EMT in mammary epithelial cells and whether this process can be targeted to inhibit EMT. Specifically, we aim to determine the mechanisms underlying syndecan-1 and the expression and activity of EMT transcription factors, relevant markers, and the involvement of calcium.

Preliminary results

We found that the loss of syndecan-1 from mouse mammary epithelial cells resulted in a comprehensive transcriptomic change where several EMT-associated genes were differentially expressed. Following this, we performed confirmatory analysis by staining the syndecan-1 knockout cells for EMT markers including E-cadherin, N-cadherin, F-actin, and Vimentin. To test the cross-species relevance of our findings, we generated syndecan-1 knockout human mammary epithelial cells using CRISPR and observed a comparable EMT phenotype. 

Since the transcriptomic analysis of syndecan-1 knockout cells revealed widespread alterations in gene expression, we hypothesised a fundamental shift in cellular behavior has occurred rather than a change limited to a single pathway. This further led to the analysis of cellular calcium, which plays a key role in cellular behavior and gene expression. Using a Förster resonance energy transfer (FRET)-based calcium biosensor, we found that syndecan-1 regulates cytosolic calcium levels in mammary epithelial cells. Moreover, inhibition of the transient receptor potential channel 4 (TRPC4), a mechanically sensitive calcium channel, partially attenuated the calcium dysregulation observed in syndecan-1-deficient cells.

Significance

We propose that syndecan-1 modulates EMT through calcium-dependent regulation of EMT transcription factors. This work provides novel insights into the role of syndecan-1 in EMT and highlights the potential for inorganic elements to control EMT and justifies a possible benefit for future therapeutic targe