Co-expression of EGF receptor, TGFα and S6 kinase is significantly associated with colorectal carcinomas with distant metastases at diagnosis

Autocrine tumour growth factor alpha (TGF alpha)/epidermal growth factor receptor (EGFR) stimulation in colorectal carcinoma (CRC) cells regulates cell adhesion and invasiveness via ribosomal protein S6 kinase (S6K) phosphorylation in pre-clinical studies. The aim of this study was to evaluate whether TGF alpha and EGFR expression might be correlated with a higher metastatic behaviour in human tumours. Paraffin-embedded material was retrospectively collected from 101 primitive CRCs including all stage IV patients at diagnosis treated at our Institution from 1999 to 2004 (50 cases, Group B) and 51 stage II-III control cases (Group A). EGFR and TGF alpha expression, together with signalling molecules (including signal transducer and activator of transcription [STAT3], serine-treonine kinase [Akt], mitogen-activated protein kinase [MAPK], mammalian target of rapamycin [mTOR] and S6K) in selected samples, was evaluated by immunohistochemistry using the EGFR Dako antibody. A total of 68/101 (67.3%) cases were EGFR positive and 79/101 (78.2%) cases were TGF alpha positive. EGFR/TGF alpha co-expression differed significantly (p = 0.02) between Group A and Group B tumours (23/51, 45.1% vs 34/50, 68.0%, respectively), whereas no differences in STAT, Akt, mTOR expression was evident between the two groups. Conversely, there was a significantly higher expression of phosphorylated S6K in stage IV cases (Group B) than in the controls (Group A; 70.4% vs 38.7%; p = 0.02). In agreement with in vitro data, EGFR, TGF alpha and S6K co-expression in human CRC was significantly higher in patients with advanced stage at diagnosis.