E-cadherin downregulation at the infiltrating tumour front is associated with histological grade and stage in colorectal carcinoma of Malaysians

Loss of E-cadherin, a 120 kDA transmembrane glycoprotein responsible for cell-cell adhesion, is one of the hallmarks of epithelial-mesenchymal-transition (EMT). E-cadherin expression was immunohistochemically studied in 94 histopathologically re-confirmed colorectal carcinomas (CRC) using a monoclonal antibody to E-cadherin (Dako: Clone NCH-38) on a Ventana Benchmark XT automated system. Each case was assessed for E-cadherin immunopositivity at two separate locations viz the tumour centre (TC) as well as the infiltrating front (IF). Expression was semiquantitated for proportion of immunopositive malignant cells as 0 (negative), 1 (1-25% staining), 2 (26-50% staining), 3 (51-75% staining) and 4 (>75% staining) and staining intensity: 0 (negative), 1 (weak), 2 (moderate) and 3 (strong). The final histoscore of E-cadherin immunopositivity was arbitrarily computed as proportion of immunopositivity multiplied by staining intensity of the malignant cells. E-cadherin histoscores were significantly lower at the IF (4.5 ± 2.5) compared with TC (10.7 ± 2.4). Furthermore, the histoscores were significantly reduced at the IF of 49 TNM III+IV tumours (3.6 ± 2.5) compared with 45 II+III CRC (5.4 ± 2.2). Reduction of E-cadherin expression was also noted in the 23 high grade (TC=8.6 ± 3.2; IF=2.6 ± 2.3) compared with 71 low grade tumours (TC = 11.4 ± 1.5; IF = 5.1 ± 2.3). E-cadherin is downregulated at the infiltrating front of CRC, possibly marking for EMT at this location. The downregulation is further enhanced amongst late stage and high grade tumours compared with earlier stage and low grade tumours; findings which are similar to that noted in CRC of other populations.