Introduction Stromal and other non-malignant cells have the potential to undergo modifications that can synergistically create a supportive microenvironment for tumour growth, invasion and metastasis. Oesophageal adenocarcinoma (EAC) is characterised by early invasion, leading to metastatic disease and therefore only 20% of patients are suitable for treatment with curative intent. Cancer associated fibroblasts (CAFs) have an activated, myofibroblastic phenotype and have been recognised as mediators of tumour progression in a range of solid tumours. This study investigates the role of CAFs in EAC invasion and resistance to chemotherapy.
Methods Functional biological analyses comparing primary fibroblasts from tumour stroma (CAF) and normal oesophagus (NOF) were carried out using organotypic culture, transwell invasion assays, collagen-1 gel contraction assays, siRNA gene silencing and colony forming assays. T-Tests (>95% CI) were carried out for all statistical analyses.
Results Primary oesophageal CAFs displayed an activated phenotype as demonstrated by α-SMA expression and increased collagen-1 gel contraction in comparison to NOFs (p<0.01). CAF conditioned medium supported tumour colony formation in the presence of cisplatin and 5-Fluorouracil compared to NOF conditioned medium (p<0.05). Ex vivo analysis revealed a twofold (p<0.05) increase in EAC cell invasion in response to primary (CAF) conditioned medium in transwell invasion assays that was replicated in 3D organotypic models containing co-cultures of fibroblasts and EAC tumour cells. Down-regulation of the CAF secreted molecule Periostin (PN) resulted in a 70% reduction in tumour cell invasion in transwell assays (p<0.05), and a total loss of invasion in organotypic culture. Furthermore, collagen-1 gel contraction was abrogated by PN down-regulation. NOFs exposed to TGF-β from 72 h demonstrate features of myofibroblastic activation including, PN expression and the ability to support increased EAC tumour cell invasion (p<0.05).
Conclusion This study has demonstrated that oesophageal derived primary CAF protect EAC cells from chemotherapy and promote tumour cell invasion. Increased α-SMA expression and collagen-1 gel contraction indicates CAF have a myofibroblast like phenotype. PN siRNA reduced gel contraction supports a hypothesis of autocrine regulation of the myofibroblast phenotype. Therefore targeting pathways that determine fibroblast activation may offer a novel therapy for preventing oesophageal cancer invasion and metastasis.
Competing interests None declared.
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