Loss of Laminin α3 induces cell invasion and macrophage infiltration in cutaneous squamous cell carcinoma.

Abstract

BACKGROUND: Cutaneous squamous cell carcinoma (cSCC) is a common cancer which invades into dermis through the basement membrane. The role of the basement membrane in poorly differentiated cSCC is poorly understood. OBJECTIVES: To study the effect that the loss of the laminin α3 chain from the tumour microenvironment has on tumour invasion and inflammatory cell recruitment. METHODS: We examined the role of the basement membrane proteins laminin α3 , β3 and γ2 in SCC invasion and inflammatory cell recruitment using immunohistochemistry, shRNA knockdown, RNASeq, mouse xenograft models and patient tumour samples RESULTS: Analysis of SCC tumours and cell lines using antibodies specific to laminin α3, β3 and γ2 identified a link between poorly differentiated SCC and reduced expression of Laminin α3 (but not the other Laminin subunits investigated). Knockdown of laminin α3 increased tumour invasion both in vitro and in vivo. Western blot and immunohistochemical staining identified increased pMLC with loss of laminin α3. Inhibition of ROCK but not RAC-1 significantly reduced the invasive potential of laminin α3 knockdown cells. Knockdown of laminin α3 and γ2 increased monocyte recruitment to the tumour microenvironment. However only the loss of laminin α3 was associated with increased tumour associated macrophages in both xenografted tumours and in patient tumour samples. CONCLUSIONS: These data provide evidence that loss of the laminin α3 chain in cSCC has an effect on both the epithelial and immune components of cSCC resulting in an aggressive tumour microenvironment.