The Wnt pathway, epithelial-stromal interactions, and malignant progression in phyllodes tumours.
In a previous study of phyllodes tumours, it has been shown that both the stroma and the epithelium can exhibit distinct molecular changes, suggesting that both are part of the neoplastic process. In view of this finding, it was decided to study stromal-epithelial interactions in these tumours by examining the Wnt-APC-beta-catenin pathway. Beta-catenin and cyclin D1 immunohistochemistry was performed on 119 phyllodes tumours. Eighty-six (72%) showed stromal nuclear beta-catenin localization and in 57% the staining was moderate or strong; however, of the eight malignant tumours in the series, seven showed absent or weak nuclear staining (p<0.025). In no tumour was nuclear beta-catenin staining seen in the epithelial component. Moderate or strong stromal cyclin D1 staining correlated with nuclear stromal beta-catenin staining (p<0.05). Forty-five of the tumours, including two malignant lesions, were screened for beta-catenin exon 3 mutations using SSCP and sequencing, but none was found. Loss of heterozygosity (LOH) of the marker D5S346 was used to infer APC mutation, but only one (benign) tumour showed LOH. Wnt2 and Wnt5a mRNA was localized by in situ hybridization in 13 cases (three malignant) chosen to reflect the different beta-catenin staining patterns. There was an association between strong nuclear beta-catenin staining of stromal cells and epithelial Wnt5a expression (p<0.0015). These data suggest that stromal proliferation in benign phyllodes tumours relies on abnormalities in the Wnt pathway which result not from mutation, but from Wnt5a expression in the epithelium. In the progression to malignancy, the stromal proliferation appears to become independent of the Wnt pathway and, presumably, of the epithelial component of these tumours.
Sawyer
Elinor J
EJ
Molecular and Population Genetics Laboratory, Imperial Cancer Research Fund, 44 Lincoln's Inn Fields, London WC2A 3PX, UK. esawyer@icrf.icnet.uk
Hanby
Andrew M
AM
Rowan
Andrew J
AJ
Gillett
Cheryl E
CE
Thomas
Rachel E
RE
Poulsom
Richard
R
Lakhani
Sunil R
SR
Ellis
Ian O
IO
Ellis
Paul
P
Tomlinson
Ian P M
IP
D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D019938:Cyclin D1 / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D018450:Disease Progression; D004848:Epithelium / Q000473:pathology; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D019656:Loss of Heterozygosity; D009363:Neoplasm Proteins / Q000378:metabolism*; D003557:Phyllodes Tumor / Q000378:metabolism* / Q000473:pathology; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D017154:Stromal Cells / Q000473:pathology; D015534:Trans-Activators; D051153:Wnt Proteins; D051154:Wnt2 Protein; D029961:Zebrafish Proteins; D051176:beta Catenin
C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D015534:Trans-Activators; C495244:WNT2 protein, human; D051153:Wnt Proteins; D051154:Wnt2 Protein; D029961:Zebrafish Proteins; D051176:beta Catenin; D019938:Cyclin D1