Elevated stromal Foxp3+ regulatory T cells combined with low density CD8+ cytotoxic T cells are associated with colorectal metastatic tumour progression


Session type:

Helen Angell1, Xiu Huan Yap2, Sunita Mistry2, Marie Cumberbatch2, Neil Gray2, Chris Womack2, Sue Watson3, David Pritchard1, Robert Wilkinson4
1School of Pharmacy, University of Nottingham, Nottingham, UK, 2Molecular Pathology Group, AstraZeneca Pharmaceuticals, Alderley Park, Macclesfield, UK, 3School of Medical and Surgical Sciences, University of Nottingham, Nottingham, UK, 4Innovative Medicines Oncology, AstraZeneca Pharmaceuticals, Alderley Park, Macclesfield, UK


Several studies in colorectal cancer (CRC) patients indicate a relationship between tumour immune infiltrates and clinical outcome (Galon et al., 2006). The aim of our study was to analyse levels of Foxp3+ regulatory T cells (Tregs) and CD8+ cytotoxic T cells in areas of tumour, tumour associated stroma and adjacent non-neoplastic tissue, within primary and metastatic CRC samples. The study aims to correlate these findings with markers of proliferation (Ki67), apoptosis (cleaved caspase-3), hypoxia (HIF-1α) and vasculature (CD31).


Primary CRC with matched hepatic metastatic (n=7), primary CRC alone (n=18) and primary CRC with matched normal (n=40) FFPE tissue were analysed immunohistochemically. Automated quantitative image analysis of tumour, stroma and non-neoplastic regions using GenieTM pattern recognition software (Aperio Technologies Ltd.) was carried out, combined with appropriate analytical algorithms for each marker.


A significant increase in the prevalence of Tregs (p<0.0001, p<0.05) and CD8 (p<0.0001, p<0.05) cells was observed in the stroma of primary and metastatic CRC, respectively, compared to infiltration of tumour.  A direct comparison between non-metastatic primary CRC (MET-) and primary CRC that resulted in metastasis (MET+) was conducted.  Elevated Tregs (p<0.05) and reduced numbers of CD8 (p>0.05) were observed in MET+ compared to MET- samples.  Within MET+ tissue, Tregs were elevated in adjacent non-neoplastic tissue, compared to distant non-neoplastic samples (p<0.0001).


Our study adds to the ongoing discussion on the role of immune cells in metastatic development.  Increased numbers of immune infiltrates are observed within stroma compared to tumour.  A metastatic phenotype has been alluded to, where elevation of Tregs and low density cytotoxic T cells, within primary tumour, is associated with metastasis.  Accumulating evidence points to a critical role of immune infiltrates in allowing metastatic development, where Tregs may support tumour growth by suppressing the host anti-tumour immune response.