Role of APAF-1, E-cadherin and peritumoral lymphocytic infiltration in tumour budding in colorectal cancer

Mutated in colorectal cancer, a putative tumor suppressor for serrated colorectal cancer, selectively represses beta-catenin-dependent transcription

Mutated in colorectal cancer (MCC) was originally identified as a candidate gene for familial adenomatous polyposis (FAP) but further study identified adenomatous polyposis coli (APC) as responsible for FAP and the physiologic/pathologic roles of MCC remained poorly understood. Recently, MCC promoter methylation was discovered as a frequent early event in a distinct subset of precursor lesions and colorectal cancer (CRC) associated with the serrated CRC pathway. Here we provide the first evidence of the biological significance of MCC loss in CRC and the molecular pathways involved. We show MCC expression is dramatically decreased in many CRC cell lines and the distinct subset of sporadic CRC characterized by the CpG island methylator phenotype and BRAF(V600E) mutation due to promoter methylation as reported previously. Importantly, we find MCC interacts with beta-catenin and that reexpression of MCC in CRC cells specifically inhibits Wnt signaling, beta-catenin/T-cell factor/lymphoid-enhancer factor-dependent transcription and cellular proliferation even in the presence of oncogenic mutant APC. We also show that MCC is localized in the nucleus and identify two functional nuclear localization signals. Taken together, MCC is a nuclear, beta-catenin-interacting protein that can act as a potential tumor suppressor in the serrated CRC pathway by inhibiting Wnt/beta-catenin signal transduction.

The metalloprotease meprinbeta processes E-cadherin and weakens intercellular adhesion

Background

Meprin (EC 3.4.24.18), an astacin-like metalloprotease, is expressed in the epithelium of the intestine and kidney tubules and has been related to cancer, but the mechanistic links are unknown.

Methodology/Principal Findings

We used MDCK and Caco-2 cells stably transfected with meprinα and or meprinβ to establish models of renal and intestinal epithelial cells expressing this protease at physiological levels. In both models E-cadherin was cleaved, producing a cell-associated 97-kDa E-cadherin fragment, which was enhanced upon activation of the meprin zymogen and reduced in the presence of a meprin inhibitor. The cleavage site was localized in the extracellular domain adjacent to the plasma membrane. In vitro assays with purified components showed that the 97-kDa fragment was specifically generated by meprinβ, but not by ADAM-10 or MMP-7. Concomitantly with E-cadherin cleavage and degradation of the E-cadherin cytoplasmic tail, the plaque proteins β-catenin and plakoglobin were processed by an intracellular protease, whereas α-catenin, which does not bind directly to E-cadherin, remained intact. Using confocal microscopy, we observed a partial colocalization of meprinβ and E-cadherin at lateral membranes of incompletely polarized cells at preconfluent or early confluent stages. Meprinβ-expressing cells displayed a reduced strength of cell-cell contacts and a significantly lower tendency to form multicellular aggregates.

Conclusions/Significance

By identifying E-cadherin as a substrate for meprinβ in a cellular context, this study reveals a novel biological role of this protease in epithelial cells. Our results suggest a crucial role for meprinβ in the control of adhesiveness via cleavage of E-cadherin with potential implications in a wide range of biological processes including epithelial barrier function and cancer progression.

Multimarker phenotype predicts adverse survival in patients with lymph node-negative colorectal cancer

BACKGROUND

The heterogeneity of stage II colon cancer underlines the need for identifying high-risk, lymph node-negative patients. The objective of this study was to define a multimarker prognostic model of 5-year survival in patients with lymph node-negative, mismatch repair (MMR)-proficient colorectal cancer (CRC).

METHODS

Immunohistochemistry for 13 tumor markers was performed on 587 lymph node-negative, MMR-proficient CRC samples by using a tissue microarray. Immunoreactivity was evaluated semiquantitatively. A receiver-operating characteristic-based approach was used to detect clinically relevant tumor markers and to determine cutoff scores for tumor positivity. Univariate and multivariate analyses stratified by pathologic T3 (pT3) or pT4 tumor classification were performed.

RESULTS

In univariate analysis, the absence of CD8+ tumor infiltrating lymphocytes (TILs) (P < .001), loss of p27 (P = .006), positive urokinase-type plasminogen activator (uPA) expression (P = .002), and positive uPA receptor (uPAR) expression (P = .037) were associated with an adverse prognosis. In multivariate analysis, CD8 (P = .001), p27 (P = .031), and uPA (P = .014) were independent prognostic factors. The multimarker phenotype of negative CD8, loss of p27, and positive uPA expression led to significantly worse survival compared with all other combinations of these features. Stratified by pT3 or pT4 stage, CD8 (P = .006) and uPA (P = .011) had independent prognostic value. Combined CD8 negativity and uPA positivity led to a more adverse prognosis in both patients with pT3 tumors and patients with pT4 tumors (P < .001). No difference was observed in the length of survival between patients with pT3 tumors who had CD8 negativity and uPA positivity and patients with pT4 tumors (P = .267).

CONCLUSIONS

The multimarker phenotype of the absence of CD8+ TILs, loss of p27, and positive uPA expression was predictive of an adverse prognosis in patients with lymph node-negative, MMR-proficient CRC. The current findings suggested that a subgroup of patients with high-risk, lymph node-negative pT3 tumors should be considered for adjuvant therapy.