Restoration of paracrine signalling within the tumour microenvironment increases tumour growth and activation of c-Met
Session type: Poster / e-Poster / Silent Theatre session
Paracrine signalling between tumour epithelial cells and the stroma in the tumour microenvironment is a pre-requisite for tumour growth and may determine responsiveness to therapeutic inhibition. Hepatocyte growth factor (HGF) and the HGF receptor, c-Met, are reported to be up-regulated in colorectal liver metastases (CRLMs) and considered to be markers of metastatic potential. They also promote epithelial-mesenchymal transition (EMT), an important developmental process which is frequently activated in carcinogenesis resulting in metastatic spread.
CRLMs (n=27) were grown as sub-cutaneous xenografts in nude mice, and subsequently treated with c-Met inhibitors. Tissues were used for RNA extraction and quantitative PCR analysis, were enzymatically disaggregated to isolate epithelial and mesenchymal cells, and were used for immunohistochemistry.
Analysis of primary human CRLMs showed that c-Met was overexpressed and accompanied by decreased E-cadherin, and increased EMT-related gene expression. Enrichment of individual cell types from primary CRLMs showed that HGF was mesenchymal, whereas c-Met was epithelial. Growth of tumours as sub-cutaneous xenografts revealed that human stroma, and thus paracrine signalling, was rapidly lost, and treatment of tumour-bearing mice with c-Met inhibitors had a generally poor response. Co-implantation of primary CRLM tumour epithelial cells with tumour-conditioned mesenchymal cells increased tumour growth, decreased necrosis, and increased c-Met activation. Implantation of tumour-associated fibroblasts into xenografts was also found to increase response to a c-Met inhibitor and to standard of care agents.
Paracrine HGF:c-Met signalling is rapidly lost in CRLM xenograft models indicating the need to restore human stroma, and it's loss may reflect the poor response to inhibition. Recapitulation of the human tumour microenvironment in xenografts by implantation of human mesenchymal cells improves the therapeutic response, and therefore provide improved models to assess drug efficacy.