Loss of Laminin alpha 3 drives SCC invasion via ROCK signalling
S241 - S241
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Squamous cell carcinoma (SCC) make up 20% of non-melanoma skin cancers and about 4 to 6% of SCC metastasise. In this study, we examined the role of the 3 chains of Laminin 332 (Lam332) in SCC invasion. Analysis of SCC tumours and cell lines using Lam332 chain specific antibodies identified a link between poorly differentiated SCC and reduced expression of Laminin α3 (but not the other chains of Lam332). This loss of expression of Laminin α3 is due to aberrant methylation at the LAMA3 promoter. To investigate further the role of each chain of Lam332 in SCC we generated stable knockdowns (KDs) of each Lam332 chain (LAMA3, LAMB3 & LAMC2) in cutaneous SCC cell lines. Using these cells we studied their role in cell attachment, motility, in vitro and in vivo invasion, cellular signalling and global gene expression. We observed distinct phenotypic and genotypic changes in each of our laminin chain KDs. RNA-seq analysis identified over-represented genes involved in motility, invasion and cytoskeletal remodelling with KD of LAMA3. Loss of LAMA3 decreased attachment and increased motility in vitro. Using a xenograft model we identified increased invasion and increased EMT in vivo with KD of LAMA3. The loss of LAMB3 decreased invasion and increased differentiation in vivo with increased Keratin 10 and involucrin expression. Cancer cell invasion is linked with the RHO Kinase signalling pathways. We investigated RHO signalling in our cell lines and identified that invading cells with KD of LAMA3 have a significant increase in ROCK activity characterised by increased phosphorylated myosin light chain kinase. Using RHO kinase inhibitors we confirmed that invasion in cells lacking LAMA3 is ROCK- dependent. These findings demonstrate that Lam332 is a major regulator of SCC differentiation and invasion.