E-cadherin is a transmembrane glycoprotein which connects epithelial cells together at adherens junctions. In normal cells, E-cadherin exerts its tumour suppressing role mainly by sequestering β-catenin from its binding to LEF (Lymphoid enhancer factor)/TCF (T cell factor) which serves the function of transcribing genes of the proliferative Wnt signaling pathway. Despite the ongoing debate on whether the loss of E-cadherin is the cause or effect of epithelial-mesenchymal transition (EMT), E-cadherin functional loss has frequently been associated with poor prognosis and survival in patients of various cancers. The dysregulation of E-cadherin expression that leads to carcinogenesis happens mostly at the epigenetic level but there are cases of genetic alterations as well. E-cadherin expression has been linked to the cellular functions of invasiveness reduction, growth inhibition, apoptosis, cell cycle arrest and differentiation. Studies on various cancers have shown that these different cellular functions are also interdependent. Recent studies have reported a rapid expansion of E-cadherin clinical relevance in various cancers. This review article summarises the multifaceted effect E-cadherin expression has on cellular functions in the context of carcinogenesis as well as its clinical implications in diagnosis, prognosis and therapeutics.

E-cadherin: Its dysregulation in carcinogenesis and clinical implications

Lung cancer remains one of the most common and malignant cancers worldwide. It is most often diagnosed at late stages, when it has already presented local invasion and distal metastases. The basic stages of invasion and metastasis involve the detachment of tumor cells from the extracellular matrix, invasion of surrounding tissues and basal lamina, intravasation into the blood stream, survival and transport through the blood stream, migration, arrest and extravasation at a distal site and formation of a metastatic lesion. These steps require fundamental mechanisms such as angiogenesis, degradation of matrix barriers, disruption of cell-cell and cell-matrix adhesion and inducement of cellular motility. Genes that regulate functions like unlimited growth potential, survival, genomic instability, angiogenesis, epithelial to mesenchymal transition and apoptosis evasion, are involved in giving lung cancer tumors invasive and metastatic competence. Improving of understanding of the underlying molecular and cellular mechanisms remains an urgent and essential issue, in order to develop new more effective strategies in preventing and treating lung cancer.

Key molecular mechanisms in lung cancer invasion and metastasis: a comprehensive review.

Background
Epithelial-mesenchymal transition (EMT) plays a crucial role in the progression and aggressiveness of colorectal carcinoma. E-cadherin is the best-characterized molecular marker of EMT, but its prognostic significance for patients with CRC remains inconclusive.

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Downregulated E-cadherin expression indicates worse prognosis in Asian patients with colorectal cancer: evidence from meta-analysis.

Background: Observational studies on the prognostic role of programmed cell death-ligand 1 (PD-L1) in non-small cell lung cancer (NSCLC) are controversial.
 Methods: To clarify the impact of PD-L1 in NSCLC survival, we performed this meta-analysis that included eligible studies. The combined hazard ratios (HR) and their corresponding 95% confidence intervals (CIs) were calculated in terms of overall survival.
 Results: A total of five studies with 877 patients were evaluable for this meta-analysis. Our results suggested that PD-L1 overexpression had a poor impact on survival of patients with NSCLC, the HR (95% CI) was 1.43 (1.24-1.63) overall, 1.51 (1.24-1.7954) in Asian patients, 1.35 (1.08-1.63) in non-Asian patients. Moreover, there was no heterogeneity between the studies.
 Conclusions: PD-L1 overexpression indicates a poor prognosis for patients with NSCLC.

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PD-L1 over-expression and survival in patients with non-small cell lung cancer: a meta-analysis.

Summary BACKGROUND: Hypoxia-inducible factor-1α (HIF-1α) plays an important role in tumour progression and metastasis through activation of many target genes that are especially involved in pivotal aspects of cancer biology. However, the prognostic role of HIF-1α has been controversial in primary patients with lung cancer. This metaanalysis was performed to systematically evaluate whether HIF-1α expression is associated with the clinical outcomes in lung cancer patients. METHODS: We retrieved relevant articles from Cochrane library, PubMed, EMbase, CNKI, CBM, VIP and Wan Fang Databases from inception to May 2012. Studies were selected using specific inclusion and exclusion criteria. A systematic review and meta-analysis was performed on the association between HIF-1α expression and clinical outcomes in lung cancer patients. All analyses were performed using the Revman 5.1 software. RESULTS: A total of 30 studies were identified as eligible for the systematic review and meta-analysis. The expression of HIF-1α was significantly higher than those in normal lung tissue; and III‒IV stage, lymph node metastasis, poorly differentiation, squamous cell carcinoma and small cell lung cancer (SCLC) were significantly higher than those in I‒II stage, no lymph node metastasis, well differentiation, adenocarcinomas and non small cell lung cancer (NSCLC), respectively (odds ratio (OR) = 19.00, 95% confidence interval (CI):12.12–29.78, p <0.00001; OR = 0.23, 95% CI:0.14–0.36, p <0.00001; OR = 3.72, 95% CI:2.38–5.80, p <0.00001; OR = 0.47, 95% CI:0.31–0.70, p <0.00002, OR = 0.24, 95% CI:0.07–0.77, p = 0.02; OR = 0.78, 95% CI:0.63–0.98, p = 0.03). VEGF and CA IX positive expression in HIF-1α positive tumour tissues were significantly higher than those in HIF-1α negative tumour tissues, respectively (OR = 3.23, 95% CI: 1.90–5.46, p <0.0001; OR = 3.84, 95% CI: 2.10–7.03, p <0.0001). The positive HIF-1α tumour tissues of patients had lower 5-year survival rates (OR = 0.13, 95% CI: 0.03–0.47, p = 0.002) and overall survival (relative risk (RR) = 1.68, 95% CI: 1.12–2.50, p = 0.01). CONCLUSIONS: HIF-1α is related to a differing degree of lung cancer cell, lymph node metastasis, post-operative survival time and histology (NSCLC vs. SCLC, adenocarcinomas vs. squamous cell carcinoma). HIF-1 α , which combines other proteins, such as vascular endothelial growth factor (VEGF) or CA IX, might serve as important parameters in evaluating biological behaviour and prognosis of lung cancer; it will be of benefit to clinical treatment and prognostic evaluation.

The expression of hypoxia-inducible factor-1α and its clinical significance in lung cancer: a systematic review and meta-analysis

E-cadherin has been implicated in invasiveness and metastasis. However, the clinical prognostic value of decreased E-cadherin expression in patients with non-small cell lung cancer (NSCLC) remains unsettled. A meta-analysis of eligible studies was performed to quantitatively review the correlation of decreased E-cadherin expression with survival in patients with NSCLC. Thirteen studies, including 2,274 patients, were subjected to final analysis. The rate of decreased E-cadherin expression was 47.6 % overall and 41.4 % for stage I disease. The combined hazard ratio (HR) was 1.41 (95 % CI 0.18-1.65; P = 0.001), indicating that decreased E-cadherin expression had an unfavorable impact on the survival of patients with NSCLC. Further, in the stratified analysis by ethnicity, the combined HR in Asians was 1.49 (95 % CI 1.27-1.71) and in non-Asians was 1.01 (95 % CI 1.00-1.02). However, when only the stage I studies were considered, the combined HR was 1.19 (95 % CI 0.90-1.47; P = 0.576), suggesting that decreased E-cadherin expression has no impact on survival. Decreased E-cadherin expression was associated with poor survival in patients with NSCLC, especially among Asians, but was not significantly correlated with survival for stage I NSCLC patients.

Xiao-Su Fu

Papers

The impact of E-cadherin expression on non-small cell lung cancer survival: a meta-analysis